| **BUSINESS COMBINATIONS (Tables)**                                                                       | 9 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
|----------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
||
| **Business Combinations [Abstract]**                                                                     |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
| Schedule of Recognized Identified Assets Acquired and Liabilities Assumed                                | The following table summarizes these equity related interests in SCUSA which constitute the purchase price and the identified assets acquired and liabilities assumed:  January 28, 2014  (in thousands)Fair value of noncontrolling interest in SCUSA $3,273,265Fair value of SCUSA employee vested stock options  210,181Fair value of SHUSA remaining ownership interest in SCUSA 5,063,881Fair value of equity-related interests in SCUSA $8,547,327   Recognized amounts of identifiable assets acquired and liabilities assumed:    Cash and cash equivalents $11,075Restricted cash 1,704,906Loan receivables - held for sale 990,137Loan receivables - retail installment contracts 19,870,790Loan receivables from dealers 102,689Loan receivables - unsecured 1,009,896Premises and equipment 74,998Leased vehicles, net 2,486,929Intangibles 768,750Miscellaneous receivables and other assets 1,061,351Deferred tax asset 16,399Borrowings and other debt obligations (24,497,607)Accounts payable and accrued liabilities (520,568)Total identifiable net assets 3,079,745   Goodwill $5,467,582                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
| Fair Value of Assets Acquired                                                                            | The fair value of the assets acquired includes finance receivables. SHUSA estimated the fair value of loans acquired from SCUSA by utilizing a methodology in which similar loans were aggregated into pools. Cash flows for each pool were determined by estimating future credit losses and the rate of prepayments. Projected monthly cash flows were then discounted to present value based on a market rate for similar loans. There was no carryover of SCUSA's allowance for loan losses associated with the loans SHUSA acquired as the loans were initially recorded at fair value.   January 28, 2014  (in thousands)Fair value of loan receivables (1) $19,870,790Gross contractual amount of loan receivables (1) 31,410,699Estimate of contractual cash flows not expected to be collected at acquisition (1) 4,301,586   (1) Fair value of receivables does not include amounts related to the loan receivables - unsecured and loan receivables from dealers due to the short-term and revolving nature of the receivables.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
| Schedule of Finite-Lived and Indefinite-Lived Intangible Assets Acquired as Part of Business Combination |   January 28, 2014  Fair ValueWeighted Average Amortization Period  (dollars in thousands)Intangibles subject to amortization:   Dealer networks $580,00017.5 years (a)Chrysler relationship 138,7509.2 years    Intangibles not subject to amortization: Trade name 50,000indefinite livedTotal Intangibles $768,750    (a) The amortization periods of the dealer network range between 7 and 20 years.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
| Summary of Gain on Change in Control                                                                     | The Company recognized a pre-tax gain of $2.4 billion in connection with the Change in Control in Non-interest income in the Condensed Consolidated Statement of Operations.  January 28, 2014  (in thousands)   Gain attributable to SCUSA shares sold $137,536Gain attributable to the remaining equity interest 2,291,003Total pre-tax gain $2,428,539                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
| Summary of Proforma Financial Information                                                                | The following table summarizes the actual unaudited amounts of Total revenue, net of Total interest expense and Net income including Noncontrolling Interest of SCUSA included in the Condensed Consolidated Financial Statements for the three-month and nine-month periods endedSeptember 30, 2014 and the supplemental pro forma consolidated Total revenue, net of total interest expense and Net income including noncontrolling interest of SHUSA entity for the three-month and nine-month periods endedSeptember 30, 2014 as if the Change in Control had occurred on January 1, 2013. These results include the impact of amortizing certain purchase accounting adjustments such as intangible assets as well as fair value adjustments to loans and issued debt. These pro forma results are presented for illustrative purposes and are not intended to represent or be indicative of the actual consolidated results of operations of SHUSA that would have been achieved had the Change in Control occurred at January 1, 2013, nor are they intended to represent or be indicative of future results of operations.   SCUSA Amounts Included in Results for the Supplemental Pro Forma Combined (b)  Three-Month Period Ended September 30, 2014 Nine-Month Period Ended September 30, 2014 Three-Month Period Ended September 30, 2014 Nine-Month Period Ended September 30, 2014  (in thousands)         Total Revenue, Net of Total Interest Expense (a) $1,585,281 $4,281,311 $2,232,312 $6,239,871Net Income including Noncontrolling Interest 136,237 710,984 289,417 655,055         (a) Total Revenue, Net of Total Interest Expense is calculated as the sum of Total Interest Income and Total Non-Interest Income, less Total Interest Expense.(b) Includes the impact of recording provision for loan losses necessary to bring the retail installment contracts and personal unsecured loans to their expected carrying values considering the required allowance for loan losses on their recorded investment amounts. |

| X                                                                                                                                                                                                                                                                                                                                  |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Schedule of Business Acquisition, Gain on Change in Control [Table Text Block]
+ References
No definition available.
+ Details**Name:**sov_ScheduleofBusinessAcquisitionGainonChangeinControlTableTextBlock**Namespace Prefix:**sov_**Data Type:**nonnum:textBlockItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Tabular disclosure of pro forma results of operations for a material business acquisition or series of individually immaterial business acquisitions that are material in the aggregate.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(2)-(3) -URI http://asc.fasb.org/extlink&oid=56956515&loc=d3e1392-128463
+ Details**Name:**us-gaap_BusinessAcquisitionProFormaInformationTextBlock**Namespace Prefix:**us-gaap_**Data Type:**nonnum:textBlockItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                      |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - References
No definition available.
+ Details**Name:**us-gaap_BusinessCombinationsAbstract**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                      |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Tabular disclosure of the reconciliation of contractual cash flows to the carrying amount relating to certain loans acquired in a transfer.
+ References
No definition available.
+ Details**Name:**us-gaap_CertainLoansAcquiredInTransferNotAccountedForAsDebtSecuritiesAcquiredDuringPeriodTableTextBlock**Namespace Prefix:**us-gaap_**Data Type:**nonnum:textBlockItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                               |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Tabular disclosure of finite-lived and indefinite-lived intangible assets acquired as part of a business combination.
+ References
No definition available.
+ Details**Name:**us-gaap_FiniteLivedAndIndefiniteLivedIntangibleAssetsAcquiredAsPartOfBusinessCombinationTableTextBlock**Namespace Prefix:**us-gaap_**Data Type:**nonnum:textBlockItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Tabular disclosure of the amounts recognized as of the acquisition date for each major class of assets acquired and liabilities assumed. May include but not limited to the following: (a) acquired receivables; (b) contingencies recognized at the acquisition date; and (c) the fair value of noncontrolling interests in the acquiree.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=56956791&loc=d3e4845-128472
+ Details**Name:**us-gaap_ScheduleOfRecognizedIdentifiedAssetsAcquiredAndLiabilitiesAssumedTableTextBlock**Namespace Prefix:**us-gaap_**Data Type:**nonnum:textBlockItemType**Balance Type:**na**Period Type:**duration |