<?xml version="1.0" encoding="utf-8"?>
<FilingSummary xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <Version>2.4.0.8</Version>
  <ProcessingTime />
  <ReportFormat>Html</ReportFormat>
  <ContextCount>978</ContextCount>
  <ElementCount>640</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>true</FootnotesReported>
  <SegmentCount>236</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>9</UnitCount>
  <MyReports>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>0001000 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/DocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
    </Report>
    <Report>
      <IsDefault>true</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>1001000 - Statement - Condensed Consolidated Balance Sheets (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/CondensedConsolidatedBalanceSheetsUnaudited</Role>
      <ShortName>Condensed Consolidated Balance Sheets (Unaudited)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>1001501 - Statement - Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/CondensedConsolidatedBalanceSheetsUnauditedParenthetical</Role>
      <ShortName>Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>1002000 - Statement - Condensed Consolidated Statements of Operations (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/CondensedConsolidatedStatementsOfOperationsUnaudited</Role>
      <ShortName>Condensed Consolidated Statements of Operations (Unaudited)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>1003000 - Statement - Condensed Consolidated Statements of Comprehensive Income (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/CondensedConsolidatedStatementsOfComprehensiveIncomeUnaudited</Role>
      <ShortName>Condensed Consolidated Statements of Comprehensive Income (Unaudited)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>1004000 - Statement - Condensed Consolidated Statement of Stockholder's Equity (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/CondensedConsolidatedStatementOfStockholdersEquityUnaudited</Role>
      <ShortName>Condensed Consolidated Statement of Stockholder's Equity (Unaudited)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>1005000 - Statement - Condensed Consolidated Statements of Cash Flows (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited</Role>
      <ShortName>Condensed Consolidated Statements of Cash Flows (Unaudited)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>2102100 - Disclosure - BASIS OF PRESENTATION AND ACCOUNTING POLICIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/BasisOfPresentationAndAccountingPolicies</Role>
      <ShortName>BASIS OF PRESENTATION AND ACCOUNTING POLICIES</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>2103100 - Disclosure - RECENT ACCOUNTING DEVELOPMENTS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/RecentAccountingDevelopments</Role>
      <ShortName>RECENT ACCOUNTING DEVELOPMENTS</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>2106100 - Disclosure - BUSINESS COMBINATIONS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/BusinessCombinations</Role>
      <ShortName>BUSINESS COMBINATIONS</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>2107100 - Disclosure - INVESTMENT SECURITIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/InvestmentSecurities</Role>
      <ShortName>INVESTMENT SECURITIES</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>2109100 - Disclosure - LOANS AND ALLOWANCE FOR CREDIT LOSSES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/LoansAndAllowanceForCreditLosses</Role>
      <ShortName>LOANS AND ALLOWANCE FOR CREDIT LOSSES</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>2113100 - Disclosure - VARIABLE INTEREST ENTITIES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/VariableInterestEntities</Role>
      <ShortName>VARIABLE INTEREST ENTITIES</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>2114100 - Disclosure - GOODWILL AND OTHER INTANGIBLES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/GoodwillAndOtherIntangibles</Role>
      <ShortName>GOODWILL AND OTHER INTANGIBLES</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>2115100 - Disclosure - OTHER ASSETS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/OtherAssets</Role>
      <ShortName>OTHER ASSETS</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>2116100 - Disclosure - BORROWINGS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/Borrowings</Role>
      <ShortName>BORROWINGS</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>2117100 - Disclosure - DERIVATIVES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/Derivatives</Role>
      <ShortName>DERIVATIVES</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>2118100 - Disclosure - INCOME TAXES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/IncomeTaxes</Role>
      <ShortName>INCOME TAXES</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>2119100 - Disclosure - STOCKHOLDER'S EQUITY</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/StockholdersEquity</Role>
      <ShortName>STOCKHOLDER'S EQUITY</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>2120100 - Disclosure - ACCUMULATED OTHER COMPREHENSIVE INCOME / (LOSS)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/AccumulatedOtherComprehensiveIncomeLoss</Role>
      <ShortName>ACCUMULATED OTHER COMPREHENSIVE INCOME / (LOSS)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>2121100 - Disclosure - COMMITMENTS, CONTINGENCIES, AND GUARANTEES</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/CommitmentsContingenciesAndGuarantees</Role>
      <ShortName>COMMITMENTS, CONTINGENCIES, AND GUARANTEES</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>2122100 - Disclosure - RELATED PARTY TRANSACTIONS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/RelatedPartyTransactions</Role>
      <ShortName>RELATED PARTY TRANSACTIONS</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>2123100 - Disclosure - FAIR VALUE</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/FairValue</Role>
      <ShortName>FAIR VALUE</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>2124100 - Disclosure - BUSINESS SEGMENT INFORMATION</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/BusinessSegmentInformation</Role>
      <ShortName>BUSINESS SEGMENT INFORMATION</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>2202202 - Disclosure - BASIS OF PRESENTATION AND ACCOUNTING POLICIES (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/BasisOfPresentationAndAccountingPoliciesPolicies</Role>
      <ShortName>BASIS OF PRESENTATION AND ACCOUNTING POLICIES (Policies)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>2302301 - Disclosure - BASIS OF PRESENTATION AND ACCOUNTING POLICIES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/BasisOfPresentationAndAccountingPoliciesTables</Role>
      <ShortName>BASIS OF PRESENTATION AND ACCOUNTING POLICIES (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>2306301 - Disclosure - BUSINESS COMBINATIONS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/BusinessCombinationsTables</Role>
      <ShortName>BUSINESS COMBINATIONS (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>2307301 - Disclosure - INVESTMENT SECURITIES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/InvestmentSecuritiesTables</Role>
      <ShortName>INVESTMENT SECURITIES (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>2309301 - Disclosure - LOANS AND ALLOWANCE FOR CREDIT LOSSES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/LoansAndAllowanceForCreditLossesTables</Role>
      <ShortName>LOANS AND ALLOWANCE FOR CREDIT LOSSES (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>2313301 - Disclosure - VARIABLE INTEREST ENTITIES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/VariableInterestEntitiesTables</Role>
      <ShortName>VARIABLE INTEREST ENTITIES (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>2314301 - Disclosure - GOODWILL AND OTHER INTANGIBLES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/GoodwillAndOtherIntangiblesTables</Role>
      <ShortName>GOODWILL AND OTHER INTANGIBLES (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>2315301 - Disclosure - OTHER ASSETS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/OtherAssetsTables</Role>
      <ShortName>OTHER ASSETS (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>2316301 - Disclosure - BORROWINGS (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/BorrowingsTables</Role>
      <ShortName>BORROWINGS (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>2317301 - Disclosure - DERIVATIVES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/DerivativesTables</Role>
      <ShortName>DERIVATIVES (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>2320301 - Disclosure - ACCUMULATED OTHER COMPREHENSIVE INCOME / (LOSS) (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/AccumulatedOtherComprehensiveIncomeLossTables</Role>
      <ShortName>ACCUMULATED OTHER COMPREHENSIVE INCOME / (LOSS) (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>2321301 - Disclosure - COMMITMENTS, CONTINGENCIES, AND GUARANTEES (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/CommitmentsContingenciesAndGuaranteesTables</Role>
      <ShortName>COMMITMENTS, CONTINGENCIES, AND GUARANTEES (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>2323301 - Disclosure - FAIR VALUE (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/FairValueTables</Role>
      <ShortName>FAIR VALUE (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>2324301 - Disclosure - BUSINESS SEGMENT INFORMATION (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/BusinessSegmentInformationTables</Role>
      <ShortName>BUSINESS SEGMENT INFORMATION (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>2402403 - Disclosure - BASIS OF PRESENTATION AND ACCOUNTING POLICIES (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/BasisOfPresentationAndAccountingPoliciesDetails</Role>
      <ShortName>BASIS OF PRESENTATION AND ACCOUNTING POLICIES (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>2403401 - Disclosure - RECENT ACCOUNTING DEVELOPMENTS Recent Accounting Developments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/RecentAccountingDevelopmentsRecentAccountingDevelopmentsDetails</Role>
      <ShortName>RECENT ACCOUNTING DEVELOPMENTS Recent Accounting Developments (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>2406402 - Disclosure - BUSINESS COMBINATIONS (Consolidated Assets Acquired and Liabilities Assumed) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/BusinessCombinationsConsolidatedAssetsAcquiredAndLiabilitiesAssumedDetails</Role>
      <ShortName>BUSINESS COMBINATIONS (Consolidated Assets Acquired and Liabilities Assumed) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>2406403 - Disclosure - BUSINESS COMBINATIONS (Fair Value of Loans Acquired) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/BusinessCombinationsFairValueOfLoansAcquiredDetails</Role>
      <ShortName>BUSINESS COMBINATIONS (Fair Value of Loans Acquired) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>2406404 - Disclosure - BUSINESS COMBINATIONS (Finite-Lived and Indefinite-Lived Intangible Assets Acquired) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/BusinessCombinationsFiniteLivedAndIndefiniteLivedIntangibleAssetsAcquiredDetails</Role>
      <ShortName>BUSINESS COMBINATIONS (Finite-Lived and Indefinite-Lived Intangible Assets Acquired) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>2406405 - Disclosure - BUSINESS COMBINATIONS (Gain in Change in Control) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/BusinessCombinationsGainInChangeInControlDetails</Role>
      <ShortName>BUSINESS COMBINATIONS (Gain in Change in Control) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>2406406 - Disclosure - BUSINESS COMBINATIONS (Pro Forma Information) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/BusinessCombinationsProFormaInformationDetails</Role>
      <ShortName>BUSINESS COMBINATIONS (Pro Forma Information) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>2407402 - Disclosure - INVESTMENT SECURITIES (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/InvestmentSecuritiesDetails</Role>
      <ShortName>INVESTMENT SECURITIES (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>2407403 - Disclosure - INVESTMENT SECURITIES (Securities Pledged as Collateral) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/InvestmentSecuritiesSecuritiesPledgedAsCollateralDetails</Role>
      <ShortName>INVESTMENT SECURITIES (Securities Pledged as Collateral) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>2407404 - Disclosure - INVESTMENT SECURITIES (Concentration Risk) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/InvestmentSecuritiesConcentrationRiskDetails</Role>
      <ShortName>INVESTMENT SECURITIES (Concentration Risk) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>2407405 - Disclosure - INVESTMENT SECURITIES (Contractual Maturity of Debt Securities) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/InvestmentSecuritiesContractualMaturityOfDebtSecuritiesDetails</Role>
      <ShortName>INVESTMENT SECURITIES (Contractual Maturity of Debt Securities) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>2407406 - Disclosure - INVESTMENT SECURITIES (Gross Unrealized Loss and Fair Value of Securities Available for Sale) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/InvestmentSecuritiesGrossUnrealizedLossAndFairValueOfSecuritiesAvailableForSaleDetails</Role>
      <ShortName>INVESTMENT SECURITIES (Gross Unrealized Loss and Fair Value of Securities Available for Sale) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>2407407 - Disclosure - INVESTMENT SECURITIES (Other-Than-Temporary Impairment) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/InvestmentSecuritiesOtherThanTemporaryImpairmentDetails</Role>
      <ShortName>INVESTMENT SECURITIES (Other-Than-Temporary Impairment) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>2407408 - Disclosure - INVESTMENT SECURITIES (Gains (Losses) and Proceeds on Sale of Securities) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/InvestmentSecuritiesGainsLossesAndProceedsOnSaleOfSecuritiesDetails</Role>
      <ShortName>INVESTMENT SECURITIES (Gains (Losses) and Proceeds on Sale of Securities) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>2407409 - Disclosure - INVESTMENT SECURITIES (Trading Securities) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/InvestmentSecuritiesTradingSecuritiesDetails</Role>
      <ShortName>INVESTMENT SECURITIES (Trading Securities) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>2407410 - Disclosure - INVESTMENT SECURITIES (Other Investments) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/InvestmentSecuritiesOtherInvestmentsDetails</Role>
      <ShortName>INVESTMENT SECURITIES (Other Investments) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>2409402 - Disclosure - LOANS AND ALLOWANCE FOR CREDIT LOSSES (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/LoansAndAllowanceForCreditLossesNarrativeDetails</Role>
      <ShortName>LOANS AND ALLOWANCE FOR CREDIT LOSSES (Narrative) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>2409403 - Disclosure - LOANS AND ALLOWANCE FOR CREDIT LOSSES (Loan and Lease Portfolio Composition) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/LoansAndAllowanceForCreditLossesLoanAndLeasePortfolioCompositionDetails</Role>
      <ShortName>LOANS AND ALLOWANCE FOR CREDIT LOSSES (Loan and Lease Portfolio Composition) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>2409404 - Disclosure - LOANS AND ALLOWANCE FOR CREDIT LOSSES (Portfolio Segments and Classes) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/LoansAndAllowanceForCreditLossesPortfolioSegmentsAndClassesDetails</Role>
      <ShortName>LOANS AND ALLOWANCE FOR CREDIT LOSSES (Portfolio Segments and Classes) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>2409405 - Disclosure - LOANS AND ALLOWANCE FOR CREDIT LOSSES (Rollforward of Allowance for Credit Losses) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/LoansAndAllowanceForCreditLossesRollforwardOfAllowanceForCreditLossesDetails</Role>
      <ShortName>LOANS AND ALLOWANCE FOR CREDIT LOSSES (Rollforward of Allowance for Credit Losses) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>2409406 - Disclosure - LOANS AND ALLOWANCE FOR CREDIT LOSSES (Non-performing Assets) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/LoansAndAllowanceForCreditLossesNonPerformingAssetsDetails</Role>
      <ShortName>LOANS AND ALLOWANCE FOR CREDIT LOSSES (Non-performing Assets) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>2409407 - Disclosure - LOANS AND ALLOWANCE FOR CREDIT LOSSES (Non-accrual Loans and Age Analysis of Past Due Loans) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/LoansAndAllowanceForCreditLossesNonAccrualLoansAndAgeAnalysisOfPastDueLoansDetails</Role>
      <ShortName>LOANS AND ALLOWANCE FOR CREDIT LOSSES (Non-accrual Loans and Age Analysis of Past Due Loans) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>2409408 - Disclosure - LOANS AND ALLOWANCE FOR CREDIT LOSSES (Impaired Loans) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/LoansAndAllowanceForCreditLossesImpairedLoansDetails</Role>
      <ShortName>LOANS AND ALLOWANCE FOR CREDIT LOSSES (Impaired Loans) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>2409409 - Disclosure - LOANS AND ALLOWANCE FOR CREDIT LOSSES (Lending Asset Quality Indicators) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/LoansAndAllowanceForCreditLossesLendingAssetQualityIndicatorsDetails</Role>
      <ShortName>LOANS AND ALLOWANCE FOR CREDIT LOSSES (Lending Asset Quality Indicators) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>2409410 - Disclosure - LOANS AND ALLOWANCE FOR CREDIT LOSSES (Consumer Lending Asset Quality Indicators-Credit Score) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/LoansAndAllowanceForCreditLossesConsumerLendingAssetQualityIndicatorsCreditScoreDetails</Role>
      <ShortName>LOANS AND ALLOWANCE FOR CREDIT LOSSES (Consumer Lending Asset Quality Indicators-Credit Score) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>2409411 - Disclosure - LOANS AND ALLOWANCE FOR CREDIT LOSSES (Consumer Lending Asset Quality Indicators-CLTV Range) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/LoansAndAllowanceForCreditLossesConsumerLendingAssetQualityIndicatorsCltvRangeDetails</Role>
      <ShortName>LOANS AND ALLOWANCE FOR CREDIT LOSSES (Consumer Lending Asset Quality Indicators-CLTV Range) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>2409412 - Disclosure - LOANS AND ALLOWANCE FOR CREDIT LOSSES (Troubled Debt Restructuring Activity) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/LoansAndAllowanceForCreditLossesTroubledDebtRestructuringActivityDetails</Role>
      <ShortName>LOANS AND ALLOWANCE FOR CREDIT LOSSES (Troubled Debt Restructuring Activity) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>2413402 - Disclosure - VARIABLE INTEREST ENTITIES (Assets and Liabilities of VIEs) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/VariableInterestEntitiesAssetsAndLiabilitiesOfViesDetails</Role>
      <ShortName>VARIABLE INTEREST ENTITIES (Assets and Liabilities of VIEs) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R67.htm</HtmlFileName>
      <LongName>2413403 - Disclosure - VARIABLE INTEREST ENTITIES (Cash Flow Summary) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/VariableInterestEntitiesCashFlowSummaryDetails</Role>
      <ShortName>VARIABLE INTEREST ENTITIES (Cash Flow Summary) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R68.htm</HtmlFileName>
      <LongName>2413404 - Disclosure - VARIABLE INTEREST ENTITIES (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/VariableInterestEntitiesDetails</Role>
      <ShortName>VARIABLE INTEREST ENTITIES (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R69.htm</HtmlFileName>
      <LongName>2414402 - Disclosure - GOODWILL AND OTHER INTANGIBLES (Goodwill) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/GoodwillAndOtherIntangiblesGoodwillDetails</Role>
      <ShortName>GOODWILL AND OTHER INTANGIBLES (Goodwill) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R70.htm</HtmlFileName>
      <LongName>2414403 - Disclosure - GOODWILL AND OTHER INTANGIBLES (Finite-lived and Indefinite-lived Intangibles) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/GoodwillAndOtherIntangiblesFiniteLivedAndIndefiniteLivedIntangiblesDetails</Role>
      <ShortName>GOODWILL AND OTHER INTANGIBLES (Finite-lived and Indefinite-lived Intangibles) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R71.htm</HtmlFileName>
      <LongName>2414404 - Disclosure - GOODWILL AND OTHER INTANGIBLES (Future Amortization Expense) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/GoodwillAndOtherIntangiblesFutureAmortizationExpenseDetails</Role>
      <ShortName>GOODWILL AND OTHER INTANGIBLES (Future Amortization Expense) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R72.htm</HtmlFileName>
      <LongName>2415402 - Disclosure - OTHER ASSETS (Other Assets Schedule) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/OtherAssetsOtherAssetsScheduleDetails</Role>
      <ShortName>OTHER ASSETS (Other Assets Schedule) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R73.htm</HtmlFileName>
      <LongName>2415403 - Disclosure - OTHER ASSETS (Servicing Assets Rollforward) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/OtherAssetsServicingAssetsRollforwardDetails</Role>
      <ShortName>OTHER ASSETS (Servicing Assets Rollforward) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R74.htm</HtmlFileName>
      <LongName>2415404 - Disclosure - OTHER ASSETS (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/OtherAssetsNarrativeDetails</Role>
      <ShortName>OTHER ASSETS (Narrative) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R75.htm</HtmlFileName>
      <LongName>2416402 - Disclosure - BORROWINGS (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/BorrowingsNarrativeDetails</Role>
      <ShortName>BORROWINGS (Narrative) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R76.htm</HtmlFileName>
      <LongName>2416403 - Disclosure - BORROWINGS (SHUSA) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/BorrowingsShusaDetails</Role>
      <ShortName>BORROWINGS (SHUSA) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R77.htm</HtmlFileName>
      <LongName>2416404 - Disclosure - BORROWINGS (Santander Bank) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/BorrowingsSantanderBankDetails</Role>
      <ShortName>BORROWINGS (Santander Bank) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R78.htm</HtmlFileName>
      <LongName>2416405 - Disclosure - BORROWINGS (SCUSA) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/BorrowingsScusaDetails</Role>
      <ShortName>BORROWINGS (SCUSA) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R79.htm</HtmlFileName>
      <LongName>2417402 - Disclosure - DERIVATIVES (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/DerivativesDetails</Role>
      <ShortName>DERIVATIVES (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R80.htm</HtmlFileName>
      <LongName>2417403 - Disclosure - DERIVATIVES (Other Derivatives) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/DerivativesOtherDerivativesDetails</Role>
      <ShortName>DERIVATIVES (Other Derivatives) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R81.htm</HtmlFileName>
      <LongName>2417404 - Disclosure - DERIVATIVES (Income Statement Effect) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/DerivativesIncomeStatementEffectDetails</Role>
      <ShortName>DERIVATIVES (Income Statement Effect) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R82.htm</HtmlFileName>
      <LongName>2417405 - Disclosure - DERIVATIVES (Offsetting of Financial Assets) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/DerivativesOffsettingOfFinancialAssetsDetails</Role>
      <ShortName>DERIVATIVES (Offsetting of Financial Assets) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R83.htm</HtmlFileName>
      <LongName>2417406 - Disclosure - DERIVATIVES (Offsetting of Financial Liabilities) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/DerivativesOffsettingOfFinancialLiabilitiesDetails</Role>
      <ShortName>DERIVATIVES (Offsetting of Financial Liabilities) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R84.htm</HtmlFileName>
      <LongName>2418401 - Disclosure - INCOME TAXES (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/IncomeTaxesDetails</Role>
      <ShortName>INCOME TAXES (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R85.htm</HtmlFileName>
      <LongName>2419401 - Disclosure - STOCKHOLDER'S EQUITY (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/StockholdersEquityDetails</Role>
      <ShortName>STOCKHOLDER'S EQUITY (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R86.htm</HtmlFileName>
      <LongName>2420402 - Disclosure - ACCUMULATED OTHER COMPREHENSIVE INCOME / (LOSS) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/AccumulatedOtherComprehensiveIncomeLossDetails</Role>
      <ShortName>ACCUMULATED OTHER COMPREHENSIVE INCOME / (LOSS) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R87.htm</HtmlFileName>
      <LongName>2421402 - Disclosure - COMMITMENTS, CONTINGENCIES, AND GUARANTEES (Off-Balance Sheet Risk and Guarantees) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/CommitmentsContingenciesAndGuaranteesOffBalanceSheetRiskAndGuaranteesDetails</Role>
      <ShortName>COMMITMENTS, CONTINGENCIES, AND GUARANTEES (Off-Balance Sheet Risk and Guarantees) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R88.htm</HtmlFileName>
      <LongName>2421403 - Disclosure - COMMITMENTS, CONTINGENCIES, AND GUARANTEES (Representation and Warranty Reserve) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/CommitmentsContingenciesAndGuaranteesRepresentationAndWarrantyReserveDetails</Role>
      <ShortName>COMMITMENTS, CONTINGENCIES, AND GUARANTEES (Representation and Warranty Reserve) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R89.htm</HtmlFileName>
      <LongName>2421404 - Disclosure - COMMITMENTS, CONTINGENCIES, AND GUARANTEES (Litigation) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/CommitmentsContingenciesAndGuaranteesLitigationDetails</Role>
      <ShortName>COMMITMENTS, CONTINGENCIES, AND GUARANTEES (Litigation) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R90.htm</HtmlFileName>
      <LongName>2423402 - Disclosure - FAIR VALUE (General) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/FairValueGeneralDetails</Role>
      <ShortName>FAIR VALUE (General) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R91.htm</HtmlFileName>
      <LongName>2423403 - Disclosure - FAIR VALUE (Fair Value Measurements, Recurring) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/FairValueFairValueMeasurementsRecurringDetails</Role>
      <ShortName>FAIR VALUE (Fair Value Measurements, Recurring) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R92.htm</HtmlFileName>
      <LongName>2423404 - Disclosure - FAIR VALUE (Fair Value Measurements, Non-recurring) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/FairValueFairValueMeasurementsNonRecurringDetails</Role>
      <ShortName>FAIR VALUE (Fair Value Measurements, Non-recurring) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R93.htm</HtmlFileName>
      <LongName>2423405 - Disclosure - FAIR VALUE (Reconciliation of Assets and Liabilities Using Level 3 Inputs) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/FairValueReconciliationOfAssetsAndLiabilitiesUsingLevel3InputsDetails</Role>
      <ShortName>FAIR VALUE (Reconciliation of Assets and Liabilities Using Level 3 Inputs) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R94.htm</HtmlFileName>
      <LongName>2423406 - Disclosure - FAIR VALUE (Sensitivity Analysis of Fair Value, Mortgage Servicing Rights) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/FairValueSensitivityAnalysisOfFairValueMortgageServicingRightsDetails</Role>
      <ShortName>FAIR VALUE (Sensitivity Analysis of Fair Value, Mortgage Servicing Rights) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R95.htm</HtmlFileName>
      <LongName>2423407 - Disclosure - FAIR VALUE (Quantitative Information) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/FairValueQuantitativeInformationDetails</Role>
      <ShortName>FAIR VALUE (Quantitative Information) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R96.htm</HtmlFileName>
      <LongName>2423408 - Disclosure - FAIR VALUE (Fair Value of Financial Instruments) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/FairValueFairValueOfFinancialInstrumentsDetails</Role>
      <ShortName>FAIR VALUE (Fair Value of Financial Instruments) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R97.htm</HtmlFileName>
      <LongName>2423409 - Disclosure - FAIR VALUE (Fair Value Option Disclosure) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/FairValueFairValueOptionDisclosureDetails</Role>
      <ShortName>FAIR VALUE (Fair Value Option Disclosure) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R98.htm</HtmlFileName>
      <LongName>2424402 - Disclosure - BUSINESS SEGMENT INFORMATION (Segment Reporting Information) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.sovereignbank.com/role/BusinessSegmentInformationSegmentReportingInformationDetails</Role>
      <ShortName>BUSINESS SEGMENT INFORMATION (Segment Reporting Information) (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <Logs>
    <Log type="Info">Element sov_CommitmentsAmountCommitted had a mix of decimals attribute values: -3 0.</Log>
    <Log type="Info">Element sov_FairValueOptionLoansHeldasAssetsAggregateAmount had a mix of decimals attribute values: -8 -3.</Log>
    <Log type="Info">Element sov_FairValueOptionLoansHeldasAssetsAggregateUnpaidPrincipalBalance had a mix of decimals attribute values: -8 -3.</Log>
    <Log type="Info">Element sov_InvestmentSecuritiesSoldDuringPeriod had a mix of decimals attribute values: -8 -5.</Log>
    <Log type="Info">Element sov_LoansSoldwithRecourseRepurchaseAmount had a mix of decimals attribute values: -8 -5.</Log>
    <Log type="Info">Element us-gaap_BusinessCombinationBargainPurchaseGainRecognizedAmount had a mix of decimals attribute values: -7 -3.</Log>
    <Log type="Info">Element us-gaap_CommonStockSharesOutstanding had a mix of decimals attribute values: -3 0.</Log>
    <Log type="Info">Element us-gaap_DerivativeLiabilities had a mix of decimals attribute values: -3 0.</Log>
    <Log type="Info">Element us-gaap_FinitelivedIntangibleAssetsAcquired1 had a mix of decimals attribute values: -5 -3.</Log>
    <Log type="Info">Element us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance had a mix of decimals attribute values: -3 0.</Log>
    <Log type="Info">Element us-gaap_InterestReceivable had a mix of decimals attribute values: -5 -3.</Log>
    <Log type="Info">Element us-gaap_LineOfCreditFacilityAmountOutstanding had a mix of decimals attribute values: -5 -3.</Log>
    <Log type="Info">Element us-gaap_LoansReceivableFairValueDisclosure had a mix of decimals attribute values: -8 -3.</Log>
    <Log type="Info">Element us-gaap_ProceedsFromIssuanceOfCommonStock had a mix of decimals attribute values: -7 -5 -3.</Log>
    <Log type="Info">Element us-gaap_SecurityOwnedAndPledgedAsCollateralFairValue had a mix of decimals attribute values: -8 -5.</Log>
    <Log type="Info">Element us-gaap_StockIssuedDuringPeriodSharesNewIssues had a mix of decimals attribute values: -3 0.</Log>
    <Log type="Info">Element us-gaap_TradingSecurities had a mix of decimals attribute values: -3 0.</Log>
    <Log type="Info">Element us-gaap_TransferOfPortfolioLoansAndLeasesToHeldForSale1 had a mix of decimals attribute values: -5 -3.</Log>
    <Log type="Info">'Monetary' elements on report '1001000 - Statement - Condensed Consolidated Balance Sheets (Unaudited)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '1001501 - Statement - Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '1002000 - Statement - Condensed Consolidated Statements of Operations (Unaudited)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '1005000 - Statement - Condensed Consolidated Statements of Cash Flows (Unaudited)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2402403 - Disclosure - BASIS OF PRESENTATION AND ACCOUNTING POLICIES (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2406402 - Disclosure - BUSINESS COMBINATIONS (Consolidated Assets Acquired and Liabilities Assumed) (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2407407 - Disclosure - INVESTMENT SECURITIES (Other-Than-Temporary Impairment) (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2407408 - Disclosure - INVESTMENT SECURITIES (Gains (Losses) and Proceeds on Sale of Securities) (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2409402 - Disclosure - LOANS AND ALLOWANCE FOR CREDIT LOSSES (Narrative) (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2409403 - Disclosure - LOANS AND ALLOWANCE FOR CREDIT LOSSES (Loan and Lease Portfolio Composition) (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2413404 - Disclosure - VARIABLE INTEREST ENTITIES (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2415404 - Disclosure - OTHER ASSETS (Narrative) (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2416402 - Disclosure - BORROWINGS (Narrative) (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2416403 - Disclosure - BORROWINGS (SHUSA) (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2416405 - Disclosure - BORROWINGS (SCUSA) (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2417402 - Disclosure - DERIVATIVES (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2417403 - Disclosure - DERIVATIVES (Other Derivatives) (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2417406 - Disclosure - DERIVATIVES (Offsetting of Financial Liabilities) (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2418401 - Disclosure - INCOME TAXES (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2421402 - Disclosure - COMMITMENTS, CONTINGENCIES, AND GUARANTEES (Off-Balance Sheet Risk and Guarantees) (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2421404 - Disclosure - COMMITMENTS, CONTINGENCIES, AND GUARANTEES (Litigation) (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2423403 - Disclosure - FAIR VALUE (Fair Value Measurements, Recurring) (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2423408 - Disclosure - FAIR VALUE (Fair Value of Financial Instruments) (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '2424402 - Disclosure - BUSINESS SEGMENT INFORMATION (Segment Reporting Information) (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">Process Flow-Through: 1001000 - Statement - Condensed Consolidated Balance Sheets (Unaudited)</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Mar. 31, 2014'</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Jun. 30, 2013'</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Mar. 31, 2013'</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Dec. 31, 2012'</Log>
    <Log type="Info">Process Flow-Through: 1001501 - Statement - Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical)</Log>
    <Log type="Info">Process Flow-Through: 1002000 - Statement - Condensed Consolidated Statements of Operations (Unaudited)</Log>
    <Log type="Info">	Process Flow-Through: Removing column '3 Months Ended
Mar. 31, 2013'</Log>
    <Log type="Info">Process Flow-Through: 1003000 - Statement - Condensed Consolidated Statements of Comprehensive Income (Unaudited)</Log>
    <Log type="Info">Process Flow-Through: 1005000 - Statement - Condensed Consolidated Statements of Cash Flows (Unaudited)</Log>
  </Logs>
  <InputFiles>
    <File>sov-20140630.xml</File>
    <File>sov-20140630.xsd</File>
    <File>sov-20140630_cal.xml</File>
    <File>sov-20140630_def.xml</File>
    <File>sov-20140630_lab.xml</File>
    <File>sov-20140630_pre.xml</File>
  </InputFiles>
  <SupplementalFiles />
  <BaseTaxonomies />
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
