| **EQUITY METHOD INVESTMENTS, VARIABLE INTEREST ENTITIES AND SECURITIZATIONS - VIE and Asset Securitizations (Details) (USD $)**                                                                                                                                                                             | Dec. 31, 2013 | Dec. 31, 2012 |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------------|---------------|
| **Variable Interest Entity [Line Items]**                                                                                                                                                                                                                                                                   |          |               |   |  |
| Maximum exposure, investment in equity                                                                                                                                                                                                                                                                      | $ 73,445,000  | [1]           | $ 101,663,000 | [1] |
| Maximum exposure, commitments                                                                                                                                                                                                                                                                               | 141,000       |               | 154,000 |  |
| Total maximum exposure                                                                                                                                                                                                                                                                                      | 73,586,000    |               | 101,817,000 |  |
| Equity method investments                                                                                                                                                                                                                                                                                   | 3,085,450,000 |               | 2,834,469,000 |  |
| Aggregate amount of assets held by VIEs                                                                                                                                                                                                                                                                     |          |               | 754,700,000 |  |
| Aggregate amount of liabilities held by VIEs                                                                                                                                                                                                                                                                |          |               | 380,100,000 |  |
| Low income housing partnerships [Member]                                                                                                                                                                                                                                                                    |          |               |   |  |
| **Variable Interest Entity [Line Items]**                                                                                                                                                                                                                                                                   |          |               |   |  |
| Maximum exposure, investment in equity                                                                                                                                                                                                                                                                      | 34,374,000    | [1]           | 57,929,000 | [1] |
| Maximum exposure, commitments                                                                                                                                                                                                                                                                               | 141,000       |               | 0 |  |
| Total maximum exposure                                                                                                                                                                                                                                                                                      | 34,515,000    |               | 57,929,000 |  |
| New market partnerships [Member]                                                                                                                                                                                                                                                                            |          |               |   |  |
| **Variable Interest Entity [Line Items]**                                                                                                                                                                                                                                                                   |          |               |   |  |
| Maximum exposure, investment in equity                                                                                                                                                                                                                                                                      | 39,071,000    | [1]           | 43,734,000 | [1] |
| Maximum exposure, commitments                                                                                                                                                                                                                                                                               | 0             |               | 154,000 |  |
| Total maximum exposure                                                                                                                                                                                                                                                                                      | 39,071,000    |               | 43,888,000 |  |
| Securitization entities [Member]                                                                                                                                                                                                                                                                            |          |               |   |  |
| **Variable Interest Entity [Line Items]**                                                                                                                                                                                                                                                                   |          |               |   |  |
| Receivable from securitizations                                                                                                                                                                                                                                                                             | 5,500,000     |               | 4,700,000 |  |
| Securitization entities [Member] | Home Equity Line of Credit [Member]                                                                                                                                                                                                                                      |          |               |   |  |
| **Variable Interest Entity [Line Items]**                                                                                                                                                                                                                                                                   |          |               |   |  |
| Principal amount outstanding on loans securitized                                                                                                                                                                                                                                                           | 41,500,000    |               | 48,100,000 |  |
| Principal amount outstanding on loans securitized, greater than 90 days past due                                                                                                                                                                                                                            | 15,300,000    |               | 14,700,000 |  |
| Net credit losses on securitized loans                                                                                                                                                                                                                                                                      | 300,000       |               | 1,100,000 |  |
| GTS EI Centro Equity Holdings, LLC [Member]                                                                                                                                                                                                                                                                 |          |               |   |  |
| **Variable Interest Entity [Line Items]**                                                                                                                                                                                                                                                                   |          |               |   |  |
| Equity method investments                                                                                                                                                                                                                                                                                   | $ 33,700,000  |               |   |  |
|                                                                                                                                                                                                                                                                                                             |
| [1]Amount represents the carrying value of the VIE's assets and liabilities on the Company's Consolidated Financial Statements which are classified within Equity method investments on the Consolidated Balance Sheet. This amount equals the carrying amount of the VIE's assets at each respective date. |

| X                                                                                                                                                                                                                                                             |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Net credit losses on securitized loans.
+ References
No definition available.
+ Details**Name:**sov_NetCreditLossesOnSecuritizedLoans**Namespace Prefix:**sov_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                       |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
This is the principal amount outstanding greater than 90 days past due for securitized loans only (across all types of loans).
+ References
No definition available.
+ Details**Name:**sov_PrincipalAmountOutstandingOnLoansSecuritizedOrAssetBackedFinancingArrangementGreaterThan90DaysPastDue**Namespace Prefix:**sov_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Variable Interest Entity, Assets
+ References
No definition available.
+ Details**Name:**sov_VariableInterestEntityAssets**Namespace Prefix:**sov_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                           |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Variable Interest Entity, Liabilities
+ References
No definition available.
+ Details**Name:**sov_VariableInterestEntityLiabilities**Namespace Prefix:**sov_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                           |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The amount owed to the reporting entity by counterparties in securitized loan transactions.
+ References
No definition available.
+ Details**Name:**us-gaap_AccountsReceivableFromSecuritization**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
This item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.12) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=16385135&loc=d3e33749-111570
+ Details**Name:**us-gaap_EquityMethodInvestments**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
This is the principal amount outstanding for securitized loans only (across all types of loans).
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=13989330&loc=d3e107314-111719
+ Details**Name:**us-gaap_PrincipalAmountOutstandingOnLoansSecuritized**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Difference between the carrying amount of assets and liabilities in the reporting entity's statement of financial position that relate to the reporting entity's variable interest in the variable interest entity (VIE) and the reporting entity's maximum exposure to loss as a result of its involvement with the VIE, where the reporting entity is not the VIE's primary beneficiary.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 4 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=28200181&loc=d3e5728-111685
+ Details**Name:**us-gaap_VariableInterestDifferenceBetweenCarryingAmountAndMaximumExposure**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The reporting entity's maximum amount of exposure to loss as a result of its involvement with the Variable Interest Entity (VIE).
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 4 -Subparagraph b -URI http://asc.fasb.org/extlink&oid=28200181&loc=d3e5728-111685Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=28200181&loc=d3e5747-111685
+ Details**Name:**us-gaap_VariableInterestEntityEntityMaximumLossExposureAmount**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**instant |
| X                                                                                                                                                                   |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_VariableInterestEntityLineItems**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Net carrying amount of the assets and liabilities in the reporting entity's statement of financial position that relate to the reporting entity's variable interest in the Variable Interest Entity (VIE), when the reporting entity is not the VIE's primary beneficiary.
+ References
No definition available.
+ Details**Name:**us-gaap_VariableInterestEntityNonconsolidatedCarryingAmountAssetsAndLiabilitiesNet**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**instant |