Line Of Credit Facility, Additional Borrowing Capacity

No definition available.

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

- Definition

Line Of Credit Facility, Reduction In Borrowing Capacity

+ References

No definition available.

+ Details

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

- Definition

Pledged Restricted Cash Separately Reported Securities Pledged Under Letter Of Credit Facilities At Fair Value

+ References

No definition available.

+ Details

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

- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 6
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=120520924&loc=SL6036836-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28551-108399

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateEffectivePercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

+ Details

Name:	us-gaap_LineOfCredit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The fair value, as of the date of each statement of financial position presented, of securities that are restricted as collateral under letter of credit agreements, and that are reclassified and separately reported in the statement of financial position because the transferee has the right by contract or custom to sell or re-pledge them.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=66007379&loc=d3e113888-111728

+ Details

Name:	us-gaap_PledgedAssetsSeparatelyReportedSecuritiesPledgedUnderLetterOfCreditFacilitiesAtFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

BORROWINGS (SC Credit Facilities) (Details) - USD ($)	Sep. 30, 2020	Apr. 30, 2020	Mar. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Balance	$ 148,000,000.0			$ 89,600,000
SC
Debt Instrument [Line Items]
Balance	55,494,918,000			54,379,783,000
Restricted Cash Pledged	1,761,567,000			1,627,524,000
SC \| Revolving Credit Facility
Debt Instrument [Line Items]
Balance	6,803,684,000			5,399,931,000
Committed Amount	$ 16,061,896,000			$ 11,872,262,000
Effective Rate	1.66%			3.44%
Assets Pledged	$ 5,525,220,000			$ 8,339,059,000
Restricted Cash Pledged	1,685,000			2,346,000
SC \| Revolving Credit Facility \| Warehouse line, due March 2021
Debt Instrument [Line Items]
Balance				516,045,000
Committed Amount				$ 1,250,000,000
Effective Rate				3.10%
Assets Pledged				$ 734,640,000
Restricted Cash Pledged				1,000
SC \| Revolving Credit Facility \| Warehouse line, due November 2020
Debt Instrument [Line Items]
Balance				471,320,000
Committed Amount				$ 500,000,000
Effective Rate				2.69%
Assets Pledged				$ 505,502,000
Restricted Cash Pledged				186,000
SC \| Revolving Credit Facility \| Warehouse line, due July 2021
Debt Instrument [Line Items]
Balance				500,000,000
Committed Amount				$ 500,000,000
Effective Rate				3.64%
Assets Pledged				$ 761,690,000
Restricted Cash Pledged				302,000
SC \| Revolving Credit Facility \| Warehouse line, due October 2021
Debt Instrument [Line Items]
Balance				896,077,000
Committed Amount				$ 2,100,000,000
Effective Rate				3.44%
Assets Pledged				$ 1,748,325,000
Restricted Cash Pledged				7,000
SC \| Revolving Credit Facility \| Warehouse line, due June 2021
Debt Instrument [Line Items]
Balance				471,284,000
Committed Amount				$ 500,000,000
Effective Rate				3.32%
Assets Pledged				$ 675,426,000
Restricted Cash Pledged				0
SC \| Revolving Credit Facility \| Warehouse line, due November 2020
Debt Instrument [Line Items]
Balance				970,600,000
Committed Amount				$ 1,000,000,000
Effective Rate				2.57%
Assets Pledged				$ 1,353,305,000
Restricted Cash Pledged				0
SC \| Revolving Credit Facility \| Warehouse line, due June 2021
Debt Instrument [Line Items]
Balance				53,900,000
Committed Amount				$ 600,000,000
Effective Rate				7.02%
Assets Pledged				$ 62,601,000
Restricted Cash Pledged				94,000
SC \| Revolving Credit Facility \| Warehouse line due, October 2021
Debt Instrument [Line Items]
Balance				1,098,443,000
Committed Amount			$ 1,000,000,000	$ 5,000,000,000
Effective Rate				4.43%
Assets Pledged				$ 1,898,365,000
Restricted Cash Pledged				1,756,000
Line of credit facility, additional borrowing capacity		$ 500,000,000
SC \| Revolving Credit Facility \| Warehouse line, due October 2021
Debt Instrument [Line Items]
Line of credit facility, reduction in borrowing capacity		$ 500,000,000
SC \| Revolving Credit Facility \| Repurchase facility, due January 2020
Debt Instrument [Line Items]
Balance				273,655,000
Committed Amount				$ 273,655,000
Effective Rate				3.80%
Assets Pledged				$ 377,550,000
Restricted Cash Pledged				0
SC \| Revolving Credit Facility \| Repurchase facility, due March 2020
Debt Instrument [Line Items]
Balance				100,756,000
Committed Amount				$ 100,756,000
Effective Rate				3.04%
Assets Pledged				$ 151,710,000
Restricted Cash Pledged				0
SC \| Revolving Credit Facility \| Repurchase facility, due March 2020
Debt Instrument [Line Items]
Balance				47,851,000
Committed Amount				$ 47,851,000
Effective Rate				3.15%
Assets Pledged				$ 69,945,000
Restricted Cash Pledged				$ 0
SC \| Revolving Credit Facilities With Third Parties
Debt Instrument [Line Items]
Balance	2,803,684,000
Committed Amount	$ 12,061,896,000
Effective Rate	2.28%
Assets Pledged	$ 5,525,220,000
Restricted Cash Pledged	1,685,000
SC \| Revolving Credit Facilities With Third Parties \| Warehouse line, due March 2021
Debt Instrument [Line Items]
Balance	500,445,000
Committed Amount	$ 1,250,000,000
Effective Rate	1.27%
Assets Pledged	$ 1,151,745,000
Restricted Cash Pledged	1,000
SC \| Revolving Credit Facilities With Third Parties \| Warehouse line, due November 2021
Debt Instrument [Line Items]
Balance	166,600,000
Committed Amount	$ 500,000,000
Effective Rate	1.04%
Assets Pledged	$ 495,011,000
Restricted Cash Pledged	0
SC \| Revolving Credit Facilities With Third Parties \| Warehouse line, due July 2021
Debt Instrument [Line Items]
Balance	0
Committed Amount	$ 500,000,000
Effective Rate	1.53%
Assets Pledged	$ 497,994,000
Restricted Cash Pledged	0
SC \| Revolving Credit Facilities With Third Parties \| Warehouse line, due October 2021
Debt Instrument [Line Items]
Balance	0
Committed Amount	$ 2,100,000,000
Effective Rate	4.18%
Assets Pledged	$ 0
Restricted Cash Pledged	0
SC \| Revolving Credit Facilities With Third Parties \| Warehouse line, due August 2022
Debt Instrument [Line Items]
Balance	166,000,000
Committed Amount	$ 500,000,000
Effective Rate	2.54%
Assets Pledged	$ 267,776,000
Restricted Cash Pledged	0
SC \| Revolving Credit Facilities With Third Parties \| Warehouse line due, January 2022
Debt Instrument [Line Items]
Balance	400,000,000
Committed Amount	$ 1,000,000,000
Effective Rate	1.43%
Assets Pledged	$ 572,755,000
Restricted Cash Pledged	0
SC \| Revolving Credit Facilities With Third Parties \| Warehouse line, due July 2022
Debt Instrument [Line Items]
Balance	0
Committed Amount	$ 900,000,000
Effective Rate	3.10%
Assets Pledged	$ 0
Restricted Cash Pledged	1,684,000
SC \| Revolving Credit Facilities With Third Parties \| Warehouse line due, October 2021
Debt Instrument [Line Items]
Balance	92,800,000
Committed Amount	$ 1,500,000,000
Effective Rate	2.69%
Assets Pledged	$ 819,518,000
Restricted Cash Pledged	0
SC \| Revolving Credit Facilities With Third Parties \| Warehouse line, due October 2021
Debt Instrument [Line Items]
Balance	1,165,943,000
Committed Amount	$ 3,500,000,000
Effective Rate	3.27%
Assets Pledged	$ 1,272,926,000
Restricted Cash Pledged	0
SC \| Revolving Credit Facilities With Third Parties \| Repurchase facility, due January 2021
Debt Instrument [Line Items]
Balance	263,272,000
Committed Amount	$ 263,272,000
Effective Rate	1.66%
Assets Pledged	$ 377,550,000
Restricted Cash Pledged	0
SC \| Revolving Credit Facilities With Third Parties \| Repurchase facility, due November 2020
Debt Instrument [Line Items]
Balance	48,624,000
Committed Amount	$ 48,624,000
Effective Rate	1.79%
Assets Pledged	$ 69,945,000
Restricted Cash Pledged	0
SC \| Revolving Credit Facility With Related Parties
Debt Instrument [Line Items]
Balance	4,000,000,000
Committed Amount	$ 4,000,000,000
Effective Rate	1.22%
Assets Pledged	$ 0
Restricted Cash Pledged	0
SC \| Revolving Credit Facility With Related Parties \| Promissory note with Santander due June 2022
Debt Instrument [Line Items]
Balance	2,000,000,000
Committed Amount	$ 2,000,000,000
Effective Rate	1.40%
Assets Pledged	$ 0
Restricted Cash Pledged	0
SC \| Revolving Credit Facility With Related Parties \| Promissory note with Santander due September 2022
Debt Instrument [Line Items]
Balance	2,000,000,000
Committed Amount	$ 2,000,000,000
Effective Rate	1.04%
Assets Pledged	$ 0
Restricted Cash Pledged	$ 0