| **BORROWINGS (SCUSA) (Details) (USD $)**                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                | 9 Months Ended                                                                                                                                                                                                                                                           |     |
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| **Line of Credit Facility [Line Items]**                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                     |     |   |
| Balance, revolving credit facilities                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    | 78,200,000us-gaap_LineOfCredit                                                                                                                                                                                                                                           |     | $ 90,200,000us-gaap_LineOfCredit |
| SCUSA [Member]                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |                                                                                                                                                                                                                                                                     |     |   |
| **Line of Credit Facility [Line Items]**                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                     |     |   |
| Balance, secured structured financings                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  | 18,562,621,000us-gaap_SecuredDebt/ dei_LegalEntityAxis= sov_ScusaMember                                                                                                                                                                                                  |     |   |
| SCUSA [Member] | Minimum [Member]                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |                                                                                                                                                                                                                                                                     |     |   |
| **Line of Credit Facility [Line Items]**                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                     |     |   |
| Effective Rate                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          | 0.89%us-gaap_DebtInstrumentInterestRateEffectivePercentage/ dei_LegalEntityAxis= sov_ScusaMember/ us-gaap_RangeAxis= us-gaap_MinimumMember                                                                                                                               |     |   |
| SCUSA [Member] | Maximum [Member]                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |                                                                                                                                                                                                                                                                     |     |   |
| **Line of Credit Facility [Line Items]**                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                     |     |   |
| Effective Rate                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          | 2.80%us-gaap_DebtInstrumentInterestRateEffectivePercentage/ dei_LegalEntityAxis= sov_ScusaMember/ us-gaap_RangeAxis= us-gaap_MaximumMember                                                                                                                               |     |   |
| SCUSA [Member] | Public Securitizations due on Various Dates [Member]                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |                                                                                                                                                                                                                                                                     |     |   |
| **Line of Credit Facility [Line Items]**                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                     |     |   |
| Balance, secured structured financings                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  | 12,211,534,000us-gaap_SecuredDebt/ us-gaap_DebtInstrumentAxis= sov_PublicSecuritizationsdueonVariousDatesMember/ dei_LegalEntityAxis= sov_ScusaMember                                                                                                                    | [1] |   |
| SCUSA [Member] | Public Securitizations due on Various Dates [Member] | Minimum [Member]                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                     |     |   |
| **Line of Credit Facility [Line Items]**                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                     |     |   |
| Effective Rate                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          | 0.89%us-gaap_DebtInstrumentInterestRateEffectivePercentage/ us-gaap_DebtInstrumentAxis= sov_PublicSecuritizationsdueonVariousDatesMember/ dei_LegalEntityAxis= sov_ScusaMember/ us-gaap_RangeAxis= us-gaap_MinimumMember                                                 |     |   |
| SCUSA [Member] | Public Securitizations due on Various Dates [Member] | Maximum [Member]                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                     |     |   |
| **Line of Credit Facility [Line Items]**                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                     |     |   |
| Effective Rate                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          | 2.80%us-gaap_DebtInstrumentInterestRateEffectivePercentage/ us-gaap_DebtInstrumentAxis= sov_PublicSecuritizationsdueonVariousDatesMember/ dei_LegalEntityAxis= sov_ScusaMember/ us-gaap_RangeAxis= us-gaap_MaximumMember                                                 |     |   |
| SCUSA [Member] | Privately Issued Amortizing Notes due on Various Dates [Member]                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |                                                                                                                                                                                                                                                                     |     |   |
| **Line of Credit Facility [Line Items]**                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                     |     |   |
| Balance, secured structured financings                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  | 6,351,087,000us-gaap_SecuredDebt/ us-gaap_DebtInstrumentAxis= sov_PrivatelyIssuedAmortizingNotesdueonVariousDatesMember/ dei_LegalEntityAxis= sov_ScusaMember                                                                                                            | [1] |   |
| SCUSA [Member] | Privately Issued Amortizing Notes due on Various Dates [Member] | Minimum [Member]                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |                                                                                                                                                                                                                                                                     |     |   |
| **Line of Credit Facility [Line Items]**                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                     |     |   |
| Effective Rate                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          | 1.05%us-gaap_DebtInstrumentInterestRateEffectivePercentage/ us-gaap_DebtInstrumentAxis= sov_PrivatelyIssuedAmortizingNotesdueonVariousDatesMember/ dei_LegalEntityAxis= sov_ScusaMember/ us-gaap_RangeAxis= us-gaap_MinimumMember                                        |     |   |
| SCUSA [Member] | Privately Issued Amortizing Notes due on Various Dates [Member] | Maximum [Member]                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |                                                                                                                                                                                                                                                                     |     |   |
| **Line of Credit Facility [Line Items]**                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                     |     |   |
| Effective Rate                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          | 1.85%us-gaap_DebtInstrumentInterestRateEffectivePercentage/ us-gaap_DebtInstrumentAxis= sov_PrivatelyIssuedAmortizingNotesdueonVariousDatesMember/ dei_LegalEntityAxis= sov_ScusaMember/ us-gaap_RangeAxis= us-gaap_MaximumMember                                        |     |   |
| SCUSA [Member] | Revolving Credit Facility [Member]                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |                                                                                                                                                                                                                                                                     |     |   |
| **Line of Credit Facility [Line Items]**                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                     |     |   |
| Balance, revolving credit facilities                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    | 8,090,080,000us-gaap_LineOfCredit/ us-gaap_CreditFacilityAxis= us-gaap_RevolvingCreditFacilityMember/ dei_LegalEntityAxis= sov_ScusaMember                                                                                                                               |     |   |
| Effective Rate                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          | 1.71%us-gaap_DebtInstrumentInterestRateEffectivePercentage/ us-gaap_CreditFacilityAxis= us-gaap_RevolvingCreditFacilityMember/ dei_LegalEntityAxis= sov_ScusaMember                                                                                                      |     |   |
| SCUSA [Member] | Revolving Credit Facility [Member] | Warehouse Line due June 2015 [Member]                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                     |     |   |
| **Line of Credit Facility [Line Items]**                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                     |     |   |
| Balance, revolving credit facilities                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    | 214,186,000us-gaap_LineOfCredit/ us-gaap_CreditFacilityAxis= us-gaap_RevolvingCreditFacilityMember/ us-gaap_DebtInstrumentAxis= sov_WarehouseLinedueJune2014Member/ dei_LegalEntityAxis= sov_ScusaMember                                                                 |     |   |
| Effective Rate                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          | 1.22%us-gaap_DebtInstrumentInterestRateEffectivePercentage/ us-gaap_CreditFacilityAxis= us-gaap_RevolvingCreditFacilityMember/ us-gaap_DebtInstrumentAxis= sov_WarehouseLinedueJune2014Member/ dei_LegalEntityAxis= sov_ScusaMember                                      |     |   |
| SCUSA [Member] | Revolving Credit Facility [Member] | Warehouse Line due on Various Dates [Member]                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |                                                                                                                                                                                                                                                                     |     |   |
| **Line of Credit Facility [Line Items]**                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                     |     |   |
| Balance, revolving credit facilities                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    | 149,602,000us-gaap_LineOfCredit/ us-gaap_CreditFacilityAxis= us-gaap_RevolvingCreditFacilityMember/ us-gaap_DebtInstrumentAxis= sov_WarehouseLinedueonVariousDatesMember/ dei_LegalEntityAxis= sov_ScusaMember                                                           | [2] |   |
| Effective Rate                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          | 1.03%us-gaap_DebtInstrumentInterestRateEffectivePercentage/ us-gaap_CreditFacilityAxis= us-gaap_RevolvingCreditFacilityMember/ us-gaap_DebtInstrumentAxis= sov_WarehouseLinedueonVariousDatesMember/ dei_LegalEntityAxis= sov_ScusaMember                                |     |   |
| SCUSA [Member] | Revolving Credit Facility [Member] | Warehouse Line due March 2015 [Member]                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            |                                                                                                                                                                                                                                                                     |     |   |
| **Line of Credit Facility [Line Items]**                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                     |     |   |
| Balance, revolving credit facilities                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    | 250,594,000us-gaap_LineOfCredit/ us-gaap_CreditFacilityAxis= us-gaap_RevolvingCreditFacilityMember/ us-gaap_DebtInstrumentAxis= sov_WarehouseLinedueMarch2015Member/ dei_LegalEntityAxis= sov_ScusaMember                                                                | [3] |   |
| Effective Rate                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          | 0.98%us-gaap_DebtInstrumentInterestRateEffectivePercentage/ us-gaap_CreditFacilityAxis= us-gaap_RevolvingCreditFacilityMember/ us-gaap_DebtInstrumentAxis= sov_WarehouseLinedueMarch2015Member/ dei_LegalEntityAxis= sov_ScusaMember                                     |     |   |
| SCUSA [Member] | Revolving Credit Facility [Member] | Warehouse Line due September 2015 [Member]                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |                                                                                                                                                                                                                                                                     |     |   |
| **Line of Credit Facility [Line Items]**                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                     |     |   |
| Balance, revolving credit facilities                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    | 175,080,000us-gaap_LineOfCredit/ us-gaap_CreditFacilityAxis= us-gaap_RevolvingCreditFacilityMember/ us-gaap_DebtInstrumentAxis= sov_WarehouseLinedueSeptember2015Member/ dei_LegalEntityAxis= sov_ScusaMember                                                            | [4] |   |
| Effective Rate                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          | 2.02%us-gaap_DebtInstrumentInterestRateEffectivePercentage/ us-gaap_CreditFacilityAxis= us-gaap_RevolvingCreditFacilityMember/ us-gaap_DebtInstrumentAxis= sov_WarehouseLinedueSeptember2015Member/ dei_LegalEntityAxis= sov_ScusaMember                                 |     |   |
| SCUSA [Member] | Revolving Credit Facility [Member] | Warehouse Line due June 2016 [Member]                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                     |     |   |
| **Line of Credit Facility [Line Items]**                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                     |     |   |
| Balance, revolving credit facilities                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    | 598,127,000us-gaap_LineOfCredit/ us-gaap_CreditFacilityAxis= us-gaap_RevolvingCreditFacilityMember/ us-gaap_DebtInstrumentAxis= sov_WarehouseLinedueJune2016Member/ dei_LegalEntityAxis= sov_ScusaMember                                                                 |     |   |
| Effective Rate                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          | 2.04%us-gaap_DebtInstrumentInterestRateEffectivePercentage/ us-gaap_CreditFacilityAxis= us-gaap_RevolvingCreditFacilityMember/ us-gaap_DebtInstrumentAxis= sov_WarehouseLinedueJune2016Member/ dei_LegalEntityAxis= sov_ScusaMember                                      |     |   |
| SCUSA [Member] | Revolving Credit Facility [Member] | Warehouse Line due December 2015 [Member]                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                     |     |   |
| **Line of Credit Facility [Line Items]**                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                     |     |   |
| Balance, revolving credit facilities                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    | 331,965,000us-gaap_LineOfCredit/ us-gaap_CreditFacilityAxis= us-gaap_RevolvingCreditFacilityMember/ us-gaap_DebtInstrumentAxis= sov_WarehouseLinedueDecember20151Member/ dei_LegalEntityAxis= sov_ScusaMember                                                            |     |   |
| Effective Rate                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          | 1.06%us-gaap_DebtInstrumentInterestRateEffectivePercentage/ us-gaap_CreditFacilityAxis= us-gaap_RevolvingCreditFacilityMember/ us-gaap_DebtInstrumentAxis= sov_WarehouseLinedueDecember20151Member/ dei_LegalEntityAxis= sov_ScusaMember                                 |     |   |
| SCUSA [Member] | Revolving Credit Facility [Member] | Warehouse Line due June 2016 [Member]                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |                                                                                                                                                                                                                                                                     |     |   |
| **Line of Credit Facility [Line Items]**                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                     |     |   |
| Balance, revolving credit facilities                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    | 2,276,688,000us-gaap_LineOfCredit/ us-gaap_CreditFacilityAxis= us-gaap_RevolvingCreditFacilityMember/ us-gaap_DebtInstrumentAxis= sov_WarehouseLinedueJune2016withChryslerCapitalMember/ dei_LegalEntityAxis= sov_ScusaMember                                            | [5] |   |
| Effective Rate                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          | 0.92%us-gaap_DebtInstrumentInterestRateEffectivePercentage/ us-gaap_CreditFacilityAxis= us-gaap_RevolvingCreditFacilityMember/ us-gaap_DebtInstrumentAxis= sov_WarehouseLinedueJune2016withChryslerCapitalMember/ dei_LegalEntityAxis= sov_ScusaMember                   |     |   |
| SCUSA [Member] | Revolving Credit Facility [Member] | Warehouse Line due June 2016 [Member] | Minimum [Member]                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |                                                                                                                                                                                                                                                                     |     |   |
| **Line of Credit Facility [Line Items]**                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                     |     |   |
| Lease financing, percentage of outstanding balance                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      | 50.00%sov_LeaseFinancingPercentage/ us-gaap_CreditFacilityAxis= us-gaap_RevolvingCreditFacilityMember/ us-gaap_DebtInstrumentAxis= sov_WarehouseLinedueJune2016withChryslerCapitalMember/ dei_LegalEntityAxis= sov_ScusaMember/ us-gaap_RangeAxis= us-gaap_MinimumMember |     |   |
| SCUSA [Member] | Revolving Credit Facility [Member] | Warehouse Line due November 2016 [Member]                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |                                                                                                                                                                                                                                                                     |     |   |
| **Line of Credit Facility [Line Items]**                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                     |     |   |
| Balance, revolving credit facilities                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    | 175,000,000us-gaap_LineOfCredit/ us-gaap_CreditFacilityAxis= us-gaap_RevolvingCreditFacilityMember/ us-gaap_DebtInstrumentAxis= sov_WarehouseLinedueNovember2016Member/ dei_LegalEntityAxis= sov_ScusaMember                                                             | [6] |   |
| Effective Rate                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          | 1.71%us-gaap_DebtInstrumentInterestRateEffectivePercentage/ us-gaap_CreditFacilityAxis= us-gaap_RevolvingCreditFacilityMember/ us-gaap_DebtInstrumentAxis= sov_WarehouseLinedueNovember2016Member/ dei_LegalEntityAxis= sov_ScusaMember                                  |     |   |
| SCUSA [Member] | Revolving Credit Facility [Member] | Repurchase Facility due on Various Dates [Member]                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |                                                                                                                                                                                                                                                                     |     |   |
| **Line of Credit Facility [Line Items]**                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                     |     |   |
| Balance, revolving credit facilities                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    | 868,838,000us-gaap_LineOfCredit/ us-gaap_CreditFacilityAxis= us-gaap_RevolvingCreditFacilityMember/ us-gaap_DebtInstrumentAxis= sov_RepurchaseFacilitydueonVariousDatesMember/ dei_LegalEntityAxis= sov_ScusaMember                                                      | [7] |   |
| Effective Rate                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          | 1.59%us-gaap_DebtInstrumentInterestRateEffectivePercentage/ us-gaap_CreditFacilityAxis= us-gaap_RevolvingCreditFacilityMember/ us-gaap_DebtInstrumentAxis= sov_RepurchaseFacilitydueonVariousDatesMember/ dei_LegalEntityAxis= sov_ScusaMember                           |     |   |
| SCUSA [Member] | Revolving Credit Facility [Member] | Repurchase Facility due on Various Dates [Member] | Minimum [Member]                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |                                                                                                                                                                                                                                                                     |     |   |
| **Line of Credit Facility [Line Items]**                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                     |     |   |
| Facility rolling maturity period                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        | 30 days                                                                                                                                                                                                                                                                  |     |   |
| SCUSA [Member] | Revolving Credit Facility [Member] | Repurchase Facility due on Various Dates [Member] | Maximum [Member]                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |                                                                                                                                                                                                                                                                     |     |   |
| **Line of Credit Facility [Line Items]**                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                     |     |   |
| Facility rolling maturity period                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        | 90 days                                                                                                                                                                                                                                                                  |     |   |
| SCUSA [Member] | Revolving Credit Facility [Member] | Line of Credit with Related Party due December 2016 [Member]                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |                                                                                                                                                                                                                                                                     |     |   |
| **Line of Credit Facility [Line Items]**                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                     |     |   |
| Balance, revolving credit facilities                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    | 500,000,000us-gaap_LineOfCredit/ us-gaap_CreditFacilityAxis= us-gaap_RevolvingCreditFacilityMember/ us-gaap_DebtInstrumentAxis= sov_LineofCreditwithRelatedPartydueDecember2016Member/ dei_LegalEntityAxis= sov_ScusaMember                                              | [8] |   |
| Effective Rate                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          | 2.45%us-gaap_DebtInstrumentInterestRateEffectivePercentage/ us-gaap_CreditFacilityAxis= us-gaap_RevolvingCreditFacilityMember/ us-gaap_DebtInstrumentAxis= sov_LineofCreditwithRelatedPartydueDecember2016Member/ dei_LegalEntityAxis= sov_ScusaMember                   |     |   |
| SCUSA [Member] | Revolving Credit Facility [Member] | Line of Credit with Related Party due December 2016 [Member]                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |                                                                                                                                                                                                                                                                     |     |   |
| **Line of Credit Facility [Line Items]**                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                     |     |   |
| Balance, revolving credit facilities                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    | 1,750,000,000us-gaap_LineOfCredit/ us-gaap_CreditFacilityAxis= us-gaap_RevolvingCreditFacilityMember/ us-gaap_DebtInstrumentAxis= sov_LineofCreditwithRelatedPartydueDecember20161Member/ dei_LegalEntityAxis= sov_ScusaMember                                           | [8] |   |
| Effective Rate                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          | 2.30%us-gaap_DebtInstrumentInterestRateEffectivePercentage/ us-gaap_CreditFacilityAxis= us-gaap_RevolvingCreditFacilityMember/ us-gaap_DebtInstrumentAxis= sov_LineofCreditwithRelatedPartydueDecember20161Member/ dei_LegalEntityAxis= sov_ScusaMember                  |     |   |
| SCUSA [Member] | Revolving Credit Facility [Member] | Line of Credit with Related Party due December 2018 [Member]                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |                                                                                                                                                                                                                                                                     |     |   |
| **Line of Credit Facility [Line Items]**                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                     |     |   |
| Balance, revolving credit facilities                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    | 800,000,000us-gaap_LineOfCredit/ us-gaap_CreditFacilityAxis= us-gaap_RevolvingCreditFacilityMember/ us-gaap_DebtInstrumentAxis= sov_LineofCreditwithRelatedPartydueDecember20181Member/ dei_LegalEntityAxis= sov_ScusaMember                                             | [8] |   |
| Effective Rate                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          | 2.75%us-gaap_DebtInstrumentInterestRateEffectivePercentage/ us-gaap_CreditFacilityAxis= us-gaap_RevolvingCreditFacilityMember/ us-gaap_DebtInstrumentAxis= sov_LineofCreditwithRelatedPartydueDecember20181Member/ dei_LegalEntityAxis= sov_ScusaMember                  |     |   |
| SCUSA [Member] | Revolving Credit Facility [Member] | Line of Credit with Related Party [Member]                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |                                                                                                                                                                                                                                                                     |     |   |
| **Line of Credit Facility [Line Items]**                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                     |     |   |
| Unsecured debt                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          | 1,700,000,000us-gaap_UnsecuredDebt/ us-gaap_CreditFacilityAxis= us-gaap_RevolvingCreditFacilityMember/ us-gaap_DebtInstrumentAxis= sov_LineofCreditwithRelatedPartyMember/ dei_LegalEntityAxis= sov_ScusaMember                                                          |     |   |
|                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
| [1]SCUSA has entered into various securitization transactions involving its retail automotive installment loans and leases. These transactions are accounted for as secured financings and therefore both the securitized retail installment contracts and the related securitization debt issued by SPEs, remain on the Condensed Consolidated Balance Sheet. The maturity of this debt is based on the timing of repayments from the securitized assets.[2]Half of the outstanding balance on this facility matures in March 2015 and half in March 2016.[3]This line is collateralized by securitization notes payable retained by SCUSA.[4]This line is held exclusively for unsecured consumer term loans.[5]This line is held exclusively for Chrysler Capital retail loan and lease financing, with lease financing comprising no more than 50% of the outstanding balance upon advance.[6]This line is collateralized by residuals retained by SCUSA.[7]The repurchase facility is also collateralized by securitization notes payable retained by the Company. No portion of this facility is unsecured. This facility has rolling 30-day and 90-day maturities.[8]These lines are collateralized by securitization notes payable and residuals retained by SCUSA. As of September 30, 2014, $1.7 billion of the aggregate outstanding balances on these credit facilities was unsecured. |

| X                                                                                                                                                                                                                                 |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Lease Financing Percentage
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 22 -Article 5Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682
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|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.16) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 19, 20, 22 -Article 5Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.16) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910
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| X                                                                                                                                                                                                                                                                                                                                                                                                                             |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Period remaining on line of credit facility before it terminates, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Carrying value as of the balance sheet date, including the current and noncurrent portions, of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer). Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower.
+ References
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|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Including the current and noncurrent portions, carrying value as of the balance sheet date of uncollateralized debt obligations (with maturities initially due after one year or beyond the operating cycle if longer).
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.16) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 16 -Article 9Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03.16) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Article 5 -Subsection 19, 20, 22
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|-----------------------------------------------------------------------------------------------------------------------------|
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