| **LOANS AND ALLOWANCE FOR CREDIT LOSSES (Non-accrual Loans and Age Analysis of Past Due Loans) (Details) (USD $)In Thousands, unless otherwise specified** | Mar. 31, 2015                                                                                                                                                                                                                                                                                       | Dec. 31, 2014                                                                                                                                                                                                                                                                                       |
|------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| **Financing Receivable, Recorded Investments, Past Due [Line Items]**                                                                                      |                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                                                |
| 30-89 Days Past Due                                                                                                                                        | $ 2,775,495sov_FinancingReceivableIncludingReceivableHeldforsaleRecordedInvestment30to89DaysPastDue                                                                                                                                                                                                 | $ 3,460,694sov_FinancingReceivableIncludingReceivableHeldforsaleRecordedInvestment30to89DaysPastDue                                                                                                                                                                                                 |
| Greater Than 90 Days                                                                                                                                       | 683,998us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue                                                                                                                                                                                                                 | 793,324us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue                                                                                                                                                                                                                 |
| Total Past Due                                                                                                                                             | 3,459,493us-gaap_FinancingReceivableRecordedInvestmentPastDue                                                                                                                                                                                                                                       | 4,254,018us-gaap_FinancingReceivableRecordedInvestmentPastDue                                                                                                                                                                                                                                       |
| Current                                                                                                                                                    | 76,422,567us-gaap_FinancingReceivableRecordedInvestmentCurrent                                                                                                                                                                                                                                      | 72,038,796us-gaap_FinancingReceivableRecordedInvestmentCurrent                                                                                                                                                                                                                                      |
| Total Financing Receivables                                                                                                                                | 79,882,060us-gaap_NotesReceivableGross                                                                                                                                                                                                                                                              | 76,292,814us-gaap_NotesReceivableGross                                                                                                                                                                                                                                                              |
| Recorded Investment 90 Days and Accruing                                                                                                                   | 84,567us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing                                                                                                                                                                                                                    | 93,152us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing                                                                                                                                                                                                                    |
| Corporate banking [Member]                                                                                                                                 |                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                                                |
| **Financing Receivable, Recorded Investments, Past Due [Line Items]**                                                                                      |                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                                                |
| Total Financing Receivables                                                                                                                                | 3,170,416us-gaap_NotesReceivableGross/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis= sov_CorporateBankingCommercialLoansMember                                                                                                                                     | 3,218,151us-gaap_NotesReceivableGross/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis= sov_CorporateBankingCommercialLoansMember                                                                                                                                     |
| Middle market commercial real estate [Member]                                                                                                              |                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                                                |
| **Financing Receivable, Recorded Investments, Past Due [Line Items]**                                                                                      |                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                                                |
| Total Financing Receivables                                                                                                                                | 3,991,045us-gaap_NotesReceivableGross/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis= sov_MiddleMarketCommercialRealEstateLoansMember                                                                                                                               | 3,743,100us-gaap_NotesReceivableGross/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis= sov_MiddleMarketCommercialRealEstateLoansMember                                                                                                                               |
| Santander real estate capital [Member]                                                                                                                     |                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                                                |
| **Financing Receivable, Recorded Investments, Past Due [Line Items]**                                                                                      |                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                                                |
| Total Financing Receivables                                                                                                                                | 1,638,296us-gaap_NotesReceivableGross/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis= sov_SantanderRealEstateCapitalMember                                                                                                                                          | 1,777,982us-gaap_NotesReceivableGross/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis= sov_SantanderRealEstateCapitalMember                                                                                                                                          |
| Commercial real estate loans [Member] | Corporate banking [Member]                                                                                         |                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                                                |
| **Financing Receivable, Recorded Investments, Past Due [Line Items]**                                                                                      |                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                                                |
| 30-89 Days Past Due                                                                                                                                        | 27,149sov_FinancingReceivableIncludingReceivableHeldforsaleRecordedInvestment30to89DaysPastDue/ us-gaap_FinancialInstrumentAxis= sov_CommercialRealEstateLoansMember/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis= sov_CorporateBankingCommercialLoansMember      | 18,363sov_FinancingReceivableIncludingReceivableHeldforsaleRecordedInvestment30to89DaysPastDue/ us-gaap_FinancialInstrumentAxis= sov_CommercialRealEstateLoansMember/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis= sov_CorporateBankingCommercialLoansMember      |
| Greater Than 90 Days                                                                                                                                       | 39,407us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue/ us-gaap_FinancialInstrumentAxis= sov_CommercialRealEstateLoansMember/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis= sov_CorporateBankingCommercialLoansMember                  | 37,708us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue/ us-gaap_FinancialInstrumentAxis= sov_CommercialRealEstateLoansMember/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis= sov_CorporateBankingCommercialLoansMember                  |
| Total Past Due                                                                                                                                             | 66,556us-gaap_FinancingReceivableRecordedInvestmentPastDue/ us-gaap_FinancialInstrumentAxis= sov_CommercialRealEstateLoansMember/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis= sov_CorporateBankingCommercialLoansMember                                          | 56,071us-gaap_FinancingReceivableRecordedInvestmentPastDue/ us-gaap_FinancialInstrumentAxis= sov_CommercialRealEstateLoansMember/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis= sov_CorporateBankingCommercialLoansMember                                          |
| Current                                                                                                                                                    | 3,103,860us-gaap_FinancingReceivableRecordedInvestmentCurrent/ us-gaap_FinancialInstrumentAxis= sov_CommercialRealEstateLoansMember/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis= sov_CorporateBankingCommercialLoansMember                                       | 3,162,080us-gaap_FinancingReceivableRecordedInvestmentCurrent/ us-gaap_FinancialInstrumentAxis= sov_CommercialRealEstateLoansMember/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis= sov_CorporateBankingCommercialLoansMember                                       |
| Total Financing Receivables                                                                                                                                | 3,170,416us-gaap_NotesReceivableGross/ us-gaap_FinancialInstrumentAxis= sov_CommercialRealEstateLoansMember/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis= sov_CorporateBankingCommercialLoansMember                                                               | 3,218,151us-gaap_NotesReceivableGross/ us-gaap_FinancialInstrumentAxis= sov_CommercialRealEstateLoansMember/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis= sov_CorporateBankingCommercialLoansMember                                                               |
| Recorded Investment 90 Days and Accruing                                                                                                                   | 0us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing/ us-gaap_FinancialInstrumentAxis= sov_CommercialRealEstateLoansMember/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis= sov_CorporateBankingCommercialLoansMember                         | 0us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing/ us-gaap_FinancialInstrumentAxis= sov_CommercialRealEstateLoansMember/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis= sov_CorporateBankingCommercialLoansMember                         |
| Commercial real estate loans [Member] | Middle market commercial real estate [Member]                                                                      |                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                                                |
| **Financing Receivable, Recorded Investments, Past Due [Line Items]**                                                                                      |                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                                                |
| 30-89 Days Past Due                                                                                                                                        | 1,224sov_FinancingReceivableIncludingReceivableHeldforsaleRecordedInvestment30to89DaysPastDue/ us-gaap_FinancialInstrumentAxis= sov_CommercialRealEstateLoansMember/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis= sov_MiddleMarketCommercialRealEstateLoansMember | 3,179sov_FinancingReceivableIncludingReceivableHeldforsaleRecordedInvestment30to89DaysPastDue/ us-gaap_FinancialInstrumentAxis= sov_CommercialRealEstateLoansMember/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis= sov_MiddleMarketCommercialRealEstateLoansMember |
| Greater Than 90 Days                                                                                                                                       | 26,263us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue/ us-gaap_FinancialInstrumentAxis= sov_CommercialRealEstateLoansMember/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis= sov_MiddleMarketCommercialRealEstateLoansMember            | 33,604us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue/ us-gaap_FinancialInstrumentAxis= sov_CommercialRealEstateLoansMember/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis= sov_MiddleMarketCommercialRealEstateLoansMember            |
| Total Past Due                                                                                                                                             | 27,487us-gaap_FinancingReceivableRecordedInvestmentPastDue/ us-gaap_FinancialInstrumentAxis= sov_CommercialRealEstateLoansMember/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis= sov_MiddleMarketCommercialRealEstateLoansMember                                    | 36,783us-gaap_FinancingReceivableRecordedInvestmentPastDue/ us-gaap_FinancialInstrumentAxis= sov_CommercialRealEstateLoansMember/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis= sov_MiddleMarketCommercialRealEstateLoansMember                                    |
| Current                                                                                                                                                    | 3,963,558us-gaap_FinancingReceivableRecordedInvestmentCurrent/ us-gaap_FinancialInstrumentAxis= sov_CommercialRealEstateLoansMember/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis= sov_MiddleMarketCommercialRealEstateLoansMember                                 | 3,706,317us-gaap_FinancingReceivableRecordedInvestmentCurrent/ us-gaap_FinancialInstrumentAxis= sov_CommercialRealEstateLoansMember/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis= sov_MiddleMarketCommercialRealEstateLoansMember                                 |
| Total Financing Receivables                                                                                                                                | 3,991,045us-gaap_NotesReceivableGross/ us-gaap_FinancialInstrumentAxis= sov_CommercialRealEstateLoansMember/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis= sov_MiddleMarketCommercialRealEstateLoansMember                                                         | 3,743,100us-gaap_NotesReceivableGross/ us-gaap_FinancialInstrumentAxis= sov_CommercialRealEstateLoansMember/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis= sov_MiddleMarketCommercialRealEstateLoansMember                                                         |
| Recorded Investment 90 Days and Accruing                                                                                                                   | 0us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing/ us-gaap_FinancialInstrumentAxis= sov_CommercialRealEstateLoansMember/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis= sov_MiddleMarketCommercialRealEstateLoansMember                   | 0us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing/ us-gaap_FinancialInstrumentAxis= sov_CommercialRealEstateLoansMember/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis= sov_MiddleMarketCommercialRealEstateLoansMember                   |
| Commercial real estate loans [Member] | Santander real estate capital [Member]                                                                             |                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                                                |
| **Financing Receivable, Recorded Investments, Past Due [Line Items]**                                                                                      |                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                                                |
| 30-89 Days Past Due                                                                                                                                        | 833sov_FinancingReceivableIncludingReceivableHeldforsaleRecordedInvestment30to89DaysPastDue/ us-gaap_FinancialInstrumentAxis= sov_CommercialRealEstateLoansMember/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis= sov_SantanderRealEstateCapitalMember              | 4,329sov_FinancingReceivableIncludingReceivableHeldforsaleRecordedInvestment30to89DaysPastDue/ us-gaap_FinancialInstrumentAxis= sov_CommercialRealEstateLoansMember/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis= sov_SantanderRealEstateCapitalMember            |
| Greater Than 90 Days                                                                                                                                       | 2,092us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue/ us-gaap_FinancialInstrumentAxis= sov_CommercialRealEstateLoansMember/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis= sov_SantanderRealEstateCapitalMember                        | 2,115us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue/ us-gaap_FinancialInstrumentAxis= sov_CommercialRealEstateLoansMember/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis= sov_SantanderRealEstateCapitalMember                        |
| Total Past Due                                                                                                                                             | 2,925us-gaap_FinancingReceivableRecordedInvestmentPastDue/ us-gaap_FinancialInstrumentAxis= sov_CommercialRealEstateLoansMember/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis= sov_SantanderRealEstateCapitalMember                                                | 6,444us-gaap_FinancingReceivableRecordedInvestmentPastDue/ us-gaap_FinancialInstrumentAxis= sov_CommercialRealEstateLoansMember/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis= sov_SantanderRealEstateCapitalMember                                                |
| Current                                                                                                                                                    | 1,635,371us-gaap_FinancingReceivableRecordedInvestmentCurrent/ us-gaap_FinancialInstrumentAxis= sov_CommercialRealEstateLoansMember/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis= sov_SantanderRealEstateCapitalMember                                            | 1,771,538us-gaap_FinancingReceivableRecordedInvestmentCurrent/ us-gaap_FinancialInstrumentAxis= sov_CommercialRealEstateLoansMember/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis= sov_SantanderRealEstateCapitalMember                                            |
| Total Financing Receivables                                                                                                                                | 1,638,296us-gaap_NotesReceivableGross/ us-gaap_FinancialInstrumentAxis= sov_CommercialRealEstateLoansMember/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis= sov_SantanderRealEstateCapitalMember                                                                    | 1,777,982us-gaap_NotesReceivableGross/ us-gaap_FinancialInstrumentAxis= sov_CommercialRealEstateLoansMember/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis= sov_SantanderRealEstateCapitalMember                                                                    |
| Recorded Investment 90 Days and Accruing                                                                                                                   | 0us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing/ us-gaap_FinancialInstrumentAxis= sov_CommercialRealEstateLoansMember/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis= sov_SantanderRealEstateCapitalMember                              | 0us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing/ us-gaap_FinancialInstrumentAxis= sov_CommercialRealEstateLoansMember/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis= sov_SantanderRealEstateCapitalMember                              |
| Commercial and industrial loans [Member]                                                                                                                   |                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                                                |
| **Financing Receivable, Recorded Investments, Past Due [Line Items]**                                                                                      |                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                                                |
| 30-89 Days Past Due                                                                                                                                        | 27,440sov_FinancingReceivableIncludingReceivableHeldforsaleRecordedInvestment30to89DaysPastDue/ us-gaap_FinancialInstrumentAxis= sov_CommercialAndIndustrialLoansMember                                                                                                                             | 27,071sov_FinancingReceivableIncludingReceivableHeldforsaleRecordedInvestment30to89DaysPastDue/ us-gaap_FinancialInstrumentAxis= sov_CommercialAndIndustrialLoansMember                                                                                                                             |
| Greater Than 90 Days                                                                                                                                       | 32,075us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue/ us-gaap_FinancialInstrumentAxis= sov_CommercialAndIndustrialLoansMember                                                                                                                                         | 23,469us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue/ us-gaap_FinancialInstrumentAxis= sov_CommercialAndIndustrialLoansMember                                                                                                                                         |
| Total Past Due                                                                                                                                             | 59,515us-gaap_FinancingReceivableRecordedInvestmentPastDue/ us-gaap_FinancialInstrumentAxis= sov_CommercialAndIndustrialLoansMember                                                                                                                                                                 | 50,540us-gaap_FinancingReceivableRecordedInvestmentPastDue/ us-gaap_FinancialInstrumentAxis= sov_CommercialAndIndustrialLoansMember                                                                                                                                                                 |
| Current                                                                                                                                                    | 18,799,528us-gaap_FinancingReceivableRecordedInvestmentCurrent/ us-gaap_FinancialInstrumentAxis= sov_CommercialAndIndustrialLoansMember                                                                                                                                                             | 17,060,866us-gaap_FinancingReceivableRecordedInvestmentCurrent/ us-gaap_FinancialInstrumentAxis= sov_CommercialAndIndustrialLoansMember                                                                                                                                                             |
| Total Financing Receivables                                                                                                                                | 18,859,043us-gaap_NotesReceivableGross/ us-gaap_FinancialInstrumentAxis= sov_CommercialAndIndustrialLoansMember                                                                                                                                                                                     | 17,111,406us-gaap_NotesReceivableGross/ us-gaap_FinancialInstrumentAxis= sov_CommercialAndIndustrialLoansMember                                                                                                                                                                                     |
| Recorded Investment 90 Days and Accruing                                                                                                                   | 0us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing/ us-gaap_FinancialInstrumentAxis= sov_CommercialAndIndustrialLoansMember                                                                                                                                                | 0us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing/ us-gaap_FinancialInstrumentAxis= sov_CommercialAndIndustrialLoansMember                                                                                                                                                |
| Multi-family loans [Member]                                                                                                                                |                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                                                |
| **Financing Receivable, Recorded Investments, Past Due [Line Items]**                                                                                      |                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                                                |
| 30-89 Days Past Due                                                                                                                                        | 6,567sov_FinancingReceivableIncludingReceivableHeldforsaleRecordedInvestment30to89DaysPastDue/ us-gaap_FinancialInstrumentAxis= sov_MultiFamilyCommercialLoansMember                                                                                                                                | 13,810sov_FinancingReceivableIncludingReceivableHeldforsaleRecordedInvestment30to89DaysPastDue/ us-gaap_FinancialInstrumentAxis= sov_MultiFamilyCommercialLoansMember                                                                                                                               |
| Greater Than 90 Days                                                                                                                                       | 4,692us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue/ us-gaap_FinancialInstrumentAxis= sov_MultiFamilyCommercialLoansMember                                                                                                                                            | 5,512us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue/ us-gaap_FinancialInstrumentAxis= sov_MultiFamilyCommercialLoansMember                                                                                                                                            |
| Total Past Due                                                                                                                                             | 11,259us-gaap_FinancingReceivableRecordedInvestmentPastDue/ us-gaap_FinancialInstrumentAxis= sov_MultiFamilyCommercialLoansMember                                                                                                                                                                   | 19,322us-gaap_FinancingReceivableRecordedInvestmentPastDue/ us-gaap_FinancialInstrumentAxis= sov_MultiFamilyCommercialLoansMember                                                                                                                                                                   |
| Current                                                                                                                                                    | 8,541,652us-gaap_FinancingReceivableRecordedInvestmentCurrent/ us-gaap_FinancialInstrumentAxis= sov_MultiFamilyCommercialLoansMember                                                                                                                                                                | 8,686,568us-gaap_FinancingReceivableRecordedInvestmentCurrent/ us-gaap_FinancialInstrumentAxis= sov_MultiFamilyCommercialLoansMember                                                                                                                                                                |
| Total Financing Receivables                                                                                                                                | 8,552,911us-gaap_NotesReceivableGross/ us-gaap_FinancialInstrumentAxis= sov_MultiFamilyCommercialLoansMember                                                                                                                                                                                        | 8,705,890us-gaap_NotesReceivableGross/ us-gaap_FinancialInstrumentAxis= sov_MultiFamilyCommercialLoansMember                                                                                                                                                                                        |
| Recorded Investment 90 Days and Accruing                                                                                                                   | 0us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing/ us-gaap_FinancialInstrumentAxis= sov_MultiFamilyCommercialLoansMember                                                                                                                                                  | 0us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing/ us-gaap_FinancialInstrumentAxis= sov_MultiFamilyCommercialLoansMember                                                                                                                                                  |
| Other commercial [Member]                                                                                                                                  |                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                                                |
| **Financing Receivable, Recorded Investments, Past Due [Line Items]**                                                                                      |                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                                                |
| 30-89 Days Past Due                                                                                                                                        | 6,087sov_FinancingReceivableIncludingReceivableHeldforsaleRecordedInvestment30to89DaysPastDue/ us-gaap_FinancialInstrumentAxis= sov_OtherCommercialLoansMember                                                                                                                                      | 5,054sov_FinancingReceivableIncludingReceivableHeldforsaleRecordedInvestment30to89DaysPastDue/ us-gaap_FinancialInstrumentAxis= sov_OtherCommercialLoansMember                                                                                                                                      |
| Greater Than 90 Days                                                                                                                                       | 794us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue/ us-gaap_FinancialInstrumentAxis= sov_OtherCommercialLoansMember                                                                                                                                                    | 1,245us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue/ us-gaap_FinancialInstrumentAxis= sov_OtherCommercialLoansMember                                                                                                                                                  |
| Total Past Due                                                                                                                                             | 6,881us-gaap_FinancingReceivableRecordedInvestmentPastDue/ us-gaap_FinancialInstrumentAxis= sov_OtherCommercialLoansMember                                                                                                                                                                          | 6,299us-gaap_FinancingReceivableRecordedInvestmentPastDue/ us-gaap_FinancialInstrumentAxis= sov_OtherCommercialLoansMember                                                                                                                                                                          |
| Current                                                                                                                                                    | 2,141,399us-gaap_FinancingReceivableRecordedInvestmentCurrent/ us-gaap_FinancialInstrumentAxis= sov_OtherCommercialLoansMember                                                                                                                                                                      | 2,077,933us-gaap_FinancingReceivableRecordedInvestmentCurrent/ us-gaap_FinancialInstrumentAxis= sov_OtherCommercialLoansMember                                                                                                                                                                      |
| Total Financing Receivables                                                                                                                                | 2,148,280us-gaap_NotesReceivableGross/ us-gaap_FinancialInstrumentAxis= sov_OtherCommercialLoansMember                                                                                                                                                                                              | 2,084,232us-gaap_NotesReceivableGross/ us-gaap_FinancialInstrumentAxis= sov_OtherCommercialLoansMember                                                                                                                                                                                              |
| Recorded Investment 90 Days and Accruing                                                                                                                   | 0us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing/ us-gaap_FinancialInstrumentAxis= sov_OtherCommercialLoansMember                                                                                                                                                        | 0us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing/ us-gaap_FinancialInstrumentAxis= sov_OtherCommercialLoansMember                                                                                                                                                        |
| Residential mortgages [Member]                                                                                                                             |                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                                                |
| **Financing Receivable, Recorded Investments, Past Due [Line Items]**                                                                                      |                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                                                |
| 30-89 Days Past Due                                                                                                                                        | 144,471sov_FinancingReceivableIncludingReceivableHeldforsaleRecordedInvestment30to89DaysPastDue/ us-gaap_FinancialInstrumentAxis= us-gaap_ResidentialMortgageMember                                                                                                                                 | 165,270sov_FinancingReceivableIncludingReceivableHeldforsaleRecordedInvestment30to89DaysPastDue/ us-gaap_FinancialInstrumentAxis= us-gaap_ResidentialMortgageMember                                                                                                                                 |
| Greater Than 90 Days                                                                                                                                       | 181,899us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue/ us-gaap_FinancialInstrumentAxis= us-gaap_ResidentialMortgageMember                                                                                                                                             | 200,818us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue/ us-gaap_FinancialInstrumentAxis= us-gaap_ResidentialMortgageMember                                                                                                                                             |
| Total Past Due                                                                                                                                             | 326,370us-gaap_FinancingReceivableRecordedInvestmentPastDue/ us-gaap_FinancialInstrumentAxis= us-gaap_ResidentialMortgageMember                                                                                                                                                                     | 366,088us-gaap_FinancingReceivableRecordedInvestmentPastDue/ us-gaap_FinancialInstrumentAxis= us-gaap_ResidentialMortgageMember                                                                                                                                                                     |
| Current                                                                                                                                                    | 6,687,906us-gaap_FinancingReceivableRecordedInvestmentCurrent/ us-gaap_FinancialInstrumentAxis= us-gaap_ResidentialMortgageMember                                                                                                                                                                   | 6,603,221us-gaap_FinancingReceivableRecordedInvestmentCurrent/ us-gaap_FinancialInstrumentAxis= us-gaap_ResidentialMortgageMember                                                                                                                                                                   |
| Total Financing Receivables                                                                                                                                | 7,014,276us-gaap_NotesReceivableGross/ us-gaap_FinancialInstrumentAxis= us-gaap_ResidentialMortgageMember                                                                                                                                                                                           | 6,969,309us-gaap_NotesReceivableGross/ us-gaap_FinancialInstrumentAxis= us-gaap_ResidentialMortgageMember                                                                                                                                                                                           |
| Recorded Investment 90 Days and Accruing                                                                                                                   | 0us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing/ us-gaap_FinancialInstrumentAxis= us-gaap_ResidentialMortgageMember                                                                                                                                                     | 0us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing/ us-gaap_FinancialInstrumentAxis= us-gaap_ResidentialMortgageMember                                                                                                                                                     |
| Home equity loans and lines of credit [Member]                                                                                                             |                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                                                |
| **Financing Receivable, Recorded Investments, Past Due [Line Items]**                                                                                      |                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                                                |
| 30-89 Days Past Due                                                                                                                                        | 34,430sov_FinancingReceivableIncludingReceivableHeldforsaleRecordedInvestment30to89DaysPastDue/ us-gaap_FinancialInstrumentAxis= us-gaap_HomeEquityMember                                                                                                                                           | 36,074sov_FinancingReceivableIncludingReceivableHeldforsaleRecordedInvestment30to89DaysPastDue/ us-gaap_FinancialInstrumentAxis= us-gaap_HomeEquityMember                                                                                                                                           |
| Greater Than 90 Days                                                                                                                                       | 84,504us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue/ us-gaap_FinancialInstrumentAxis= us-gaap_HomeEquityMember                                                                                                                                                       | 86,749us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue/ us-gaap_FinancialInstrumentAxis= us-gaap_HomeEquityMember                                                                                                                                                       |
| Total Past Due                                                                                                                                             | 118,934us-gaap_FinancingReceivableRecordedInvestmentPastDue/ us-gaap_FinancialInstrumentAxis= us-gaap_HomeEquityMember                                                                                                                                                                              | 122,823us-gaap_FinancingReceivableRecordedInvestmentPastDue/ us-gaap_FinancialInstrumentAxis= us-gaap_HomeEquityMember                                                                                                                                                                              |
| Current                                                                                                                                                    | 6,053,047us-gaap_FinancingReceivableRecordedInvestmentCurrent/ us-gaap_FinancialInstrumentAxis= us-gaap_HomeEquityMember                                                                                                                                                                            | 6,084,157us-gaap_FinancingReceivableRecordedInvestmentCurrent/ us-gaap_FinancialInstrumentAxis= us-gaap_HomeEquityMember                                                                                                                                                                            |
| Total Financing Receivables                                                                                                                                | 6,171,981us-gaap_NotesReceivableGross/ us-gaap_FinancialInstrumentAxis= us-gaap_HomeEquityMember                                                                                                                                                                                                    | 6,206,980us-gaap_NotesReceivableGross/ us-gaap_FinancialInstrumentAxis= us-gaap_HomeEquityMember                                                                                                                                                                                                    |
| Recorded Investment 90 Days and Accruing                                                                                                                   | 0us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing/ us-gaap_FinancialInstrumentAxis= us-gaap_HomeEquityMember                                                                                                                                                              | 0us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing/ us-gaap_FinancialInstrumentAxis= us-gaap_HomeEquityMember                                                                                                                                                              |
| Retail installment contracts and auto loans [Member]                                                                                                       |                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                                                |
| **Financing Receivable, Recorded Investments, Past Due [Line Items]**                                                                                      |                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                                                |
| 30-89 Days Past Due                                                                                                                                        | 2,374,712sov_FinancingReceivableIncludingReceivableHeldforsaleRecordedInvestment30to89DaysPastDue/ us-gaap_FinancialInstrumentAxis= us-gaap_ConsumerLoansAutoFinancingReceivableMember                                                                                                              | 3,046,943sov_FinancingReceivableIncludingReceivableHeldforsaleRecordedInvestment30to89DaysPastDue/ us-gaap_FinancialInstrumentAxis= us-gaap_ConsumerLoansAutoFinancingReceivableMember                                                                                                              |
| Greater Than 90 Days                                                                                                                                       | 177,559us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue/ us-gaap_FinancialInstrumentAxis= us-gaap_ConsumerLoansAutoFinancingReceivableMember                                                                                                                            | 259,534us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue/ us-gaap_FinancialInstrumentAxis= us-gaap_ConsumerLoansAutoFinancingReceivableMember                                                                                                                            |
| Total Past Due                                                                                                                                             | 2,552,271us-gaap_FinancingReceivableRecordedInvestmentPastDue/ us-gaap_FinancialInstrumentAxis= us-gaap_ConsumerLoansAutoFinancingReceivableMember                                                                                                                                                  | 3,306,477us-gaap_FinancingReceivableRecordedInvestmentPastDue/ us-gaap_FinancialInstrumentAxis= us-gaap_ConsumerLoansAutoFinancingReceivableMember                                                                                                                                                  |
| Current                                                                                                                                                    | 21,853,397us-gaap_FinancingReceivableRecordedInvestmentCurrent/ us-gaap_FinancialInstrumentAxis= us-gaap_ConsumerLoansAutoFinancingReceivableMember                                                                                                                                                 | 19,169,188us-gaap_FinancingReceivableRecordedInvestmentCurrent/ us-gaap_FinancialInstrumentAxis= us-gaap_ConsumerLoansAutoFinancingReceivableMember                                                                                                                                                 |
| Total Financing Receivables                                                                                                                                | 24,405,668us-gaap_NotesReceivableGross/ us-gaap_FinancialInstrumentAxis= us-gaap_ConsumerLoansAutoFinancingReceivableMember                                                                                                                                                                         | 22,475,665us-gaap_NotesReceivableGross/ us-gaap_FinancialInstrumentAxis= us-gaap_ConsumerLoansAutoFinancingReceivableMember                                                                                                                                                                         |
| Recorded Investment 90 Days and Accruing                                                                                                                   | 0us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing/ us-gaap_FinancialInstrumentAxis= us-gaap_ConsumerLoansAutoFinancingReceivableMember                                                                                                                                    | 0us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing/ us-gaap_FinancialInstrumentAxis= us-gaap_ConsumerLoansAutoFinancingReceivableMember                                                                                                                                    |
| Personal unsecured loan [Member]                                                                                                                           |                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                                                |
| **Financing Receivable, Recorded Investments, Past Due [Line Items]**                                                                                      |                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                                                |
| 30-89 Days Past Due                                                                                                                                        | 110,324sov_FinancingReceivableIncludingReceivableHeldforsaleRecordedInvestment30to89DaysPastDue/ us-gaap_FinancialInstrumentAxis= sov_PersonalUnsecuredLoanMember                                                                                                                                   | 92,905sov_FinancingReceivableIncludingReceivableHeldforsaleRecordedInvestment30to89DaysPastDue/ us-gaap_FinancialInstrumentAxis= sov_PersonalUnsecuredLoanMember                                                                                                                                    |
| Greater Than 90 Days                                                                                                                                       | 100,137us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue/ us-gaap_FinancialInstrumentAxis= sov_PersonalUnsecuredLoanMember                                                                                                                                               | 111,917us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue/ us-gaap_FinancialInstrumentAxis= sov_PersonalUnsecuredLoanMember                                                                                                                                               |
| Total Past Due                                                                                                                                             | 210,461us-gaap_FinancingReceivableRecordedInvestmentPastDue/ us-gaap_FinancialInstrumentAxis= sov_PersonalUnsecuredLoanMember                                                                                                                                                                       | 204,822us-gaap_FinancingReceivableRecordedInvestmentPastDue/ us-gaap_FinancialInstrumentAxis= sov_PersonalUnsecuredLoanMember                                                                                                                                                                       |
| Current                                                                                                                                                    | 2,486,354us-gaap_FinancingReceivableRecordedInvestmentCurrent/ us-gaap_FinancialInstrumentAxis= sov_PersonalUnsecuredLoanMember                                                                                                                                                                     | 2,491,998us-gaap_FinancingReceivableRecordedInvestmentCurrent/ us-gaap_FinancialInstrumentAxis= sov_PersonalUnsecuredLoanMember                                                                                                                                                                     |
| Total Financing Receivables                                                                                                                                | 2,696,815us-gaap_NotesReceivableGross/ us-gaap_FinancialInstrumentAxis= sov_PersonalUnsecuredLoanMember                                                                                                                                                                                             | 2,696,820us-gaap_NotesReceivableGross/ us-gaap_FinancialInstrumentAxis= sov_PersonalUnsecuredLoanMember                                                                                                                                                                                             |
| Recorded Investment 90 Days and Accruing                                                                                                                   | 84,567us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing/ us-gaap_FinancialInstrumentAxis= sov_PersonalUnsecuredLoanMember                                                                                                                                                  | 93,152us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing/ us-gaap_FinancialInstrumentAxis= sov_PersonalUnsecuredLoanMember                                                                                                                                                  |
| Other consumer [Member]                                                                                                                                    |                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                                                |
| **Financing Receivable, Recorded Investments, Past Due [Line Items]**                                                                                      |                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                                                                                |
| 30-89 Days Past Due                                                                                                                                        | 42,258sov_FinancingReceivableIncludingReceivableHeldforsaleRecordedInvestment30to89DaysPastDue/ us-gaap_FinancialInstrumentAxis= sov_OtherConsumerLoansMember                                                                                                                                       | 47,696sov_FinancingReceivableIncludingReceivableHeldforsaleRecordedInvestment30to89DaysPastDue/ us-gaap_FinancialInstrumentAxis= sov_OtherConsumerLoansMember                                                                                                                                       |
| Greater Than 90 Days                                                                                                                                       | 34,576us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue/ us-gaap_FinancialInstrumentAxis= sov_OtherConsumerLoansMember                                                                                                                                                   | 30,653us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue/ us-gaap_FinancialInstrumentAxis= sov_OtherConsumerLoansMember                                                                                                                                                   |
| Total Past Due                                                                                                                                             | 76,834us-gaap_FinancingReceivableRecordedInvestmentPastDue/ us-gaap_FinancialInstrumentAxis= sov_OtherConsumerLoansMember                                                                                                                                                                           | 78,349us-gaap_FinancingReceivableRecordedInvestmentPastDue/ us-gaap_FinancialInstrumentAxis= sov_OtherConsumerLoansMember                                                                                                                                                                           |
| Current                                                                                                                                                    | 1,156,495us-gaap_FinancingReceivableRecordedInvestmentCurrent/ us-gaap_FinancialInstrumentAxis= sov_OtherConsumerLoansMember                                                                                                                                                                        | 1,224,930us-gaap_FinancingReceivableRecordedInvestmentCurrent/ us-gaap_FinancialInstrumentAxis= sov_OtherConsumerLoansMember                                                                                                                                                                        |
| Total Financing Receivables                                                                                                                                | 1,233,329us-gaap_NotesReceivableGross/ us-gaap_FinancialInstrumentAxis= sov_OtherConsumerLoansMember                                                                                                                                                                                                | 1,303,279us-gaap_NotesReceivableGross/ us-gaap_FinancialInstrumentAxis= sov_OtherConsumerLoansMember                                                                                                                                                                                                |
| Recorded Investment 90 Days and Accruing                                                                                                                   | $ 0us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing/ us-gaap_FinancialInstrumentAxis= sov_OtherConsumerLoansMember                                                                                                                                                        | $ 0us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing/ us-gaap_FinancialInstrumentAxis= sov_OtherConsumerLoansMember                                                                                                                                                        |

| X                                                                                                                                                                                                                                                                                                                                                                             |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Financing Receivable, Including Receivable Held-for-sale, Recorded Investment, 30 to 89 Days Past Due
+ References
No definition available.
+ Details**Name:**sov_FinancingReceivableIncludingReceivableHeldforsaleRecordedInvestment30to89DaysPastDue**Namespace Prefix:**sov_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Recorded investment in financing receivables that are 90 days or more past due and still accruing.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 7 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=35738203&loc=d3e5111-111524
+ Details**Name:**us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Financing receivables that are current.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 7A -URI http://asc.fasb.org/extlink&oid=35738203&loc=SL6953401-111524
+ Details**Name:**us-gaap_FinancingReceivableRecordedInvestmentCurrent**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Financing receivables that are equal to or greater than 90 days past due.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 7A -URI http://asc.fasb.org/extlink&oid=35738203&loc=SL6953401-111524
+ Details**Name:**us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Recorded Investment in financing receivables that are past due at the balance sheet date.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 7A -URI http://asc.fasb.org/extlink&oid=35738203&loc=SL6953401-111524
+ Details**Name:**us-gaap_FinancingReceivableRecordedInvestmentPastDue**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                         |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount representing an agreement for an unconditional promise by the maker to pay the entity (holder) a definite sum of money at a future date. Such amount may include accrued interest receivable in accordance with the terms of the note. The note also may contain provisions and related items including a discount or premium, payable on demand, secured, or unsecured, interest bearing or noninterest bearing, among a myriad of other features and characteristics. Excludes amounts related to receivables held-for-sale.
+ 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 210.9-03.10(3)) -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 10 -Subparagraph 3 -Article 9
+ Details**Name:**us-gaap_NotesReceivableGross**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                              |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                           |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                            |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_FinancialInstrumentAxis=sov_MultiFamilyCommercialLoansMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                      |
|--------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_FinancialInstrumentAxis=sov_OtherCommercialLoansMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                    |
|------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_FinancialInstrumentAxis=sov_OtherConsumerLoansMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                       |
|---------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_FinancialInstrumentAxis=sov_PersonalUnsecuredLoanMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                          |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_FinancialInstrumentAxis=us-gaap_ConsumerLoansAutoFinancingReceivableMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                |
|--------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                         |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                                                                               |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                                                                                     |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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| X                                                                                                                                                                                                          |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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