VARIABLE INTEREST ENTITIES (Assets and Liabilities of VIEs) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014
Variable Interest Entity and Securitizations [Abstract]
Restricted cash	$ 1,613,054
Retail installment contracts, net	19,148,951
Leased vehicles, net	3,567,546
Various other assets	898,291
Notes payable	27,192,535
Various other liabilities	$ 49,983

Name:	sov_VariableInterestEntityandSecuritizationsAbstract
Namespace Prefix:	sov_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Variable Interest Entity, Consolidated, Carrying Amount, Notes Payable

No definition available.

Name:	sov_VariableInterestEntityConsolidatedCarryingAmountNotesPayable
Namespace Prefix:	sov_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Variable Interest Entity, Consolidated, Carrying Amount, Other Assets

No definition available.

Name:	sov_VariableInterestEntityConsolidatedCarryingAmountOtherAssets
Namespace Prefix:	sov_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Variable Interest Entity, Consolidated, Carrying Amount, Other Liabilities

No definition available.

Name:	sov_VariableInterestEntityConsolidatedCarryingAmountOtherLiabilities
Namespace Prefix:	sov_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Variable Interest Entity, Consolidated, Carrying Amount, Property Subject to or Available for Operating Lease, Net

No definition available.

Name:	sov_VariableInterestEntityConsolidatedCarryingAmountPropertySubjecttoorAvailableforOperatingLeaseNet
Namespace Prefix:	sov_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Variable Interest Entity, Consolidated, Carrying Amount, Restricted Cash

No definition available.

Name:	sov_VariableInterestEntityConsolidatedCarryingAmountRestrictedCash
Namespace Prefix:	sov_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Variable Interest Entity, Consolidated, Carrying Amount, Retail Installment Contracts, Net

No definition available.

Name:	sov_VariableInterestEntityConsolidatedCarryingAmountRetailInstallmentContractsNet
Namespace Prefix:	sov_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant