Financing Receivable, Allowance for Credit Loss, Other

No definition available.

Name:	ally_FinancingReceivableAllowanceForCreditLossOther
Namespace Prefix:	ally_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

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

- Definition

Amount excluding accrued interest, of allowance for credit loss on financing receivable.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=124255206&loc=SL82895884-210446

+ Details

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

- Definition

Amount, after recovery, of writeoff of financing receivable, charged against allowance for credit loss.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 55
-Paragraph 79
-URI http://asc.fasb.org/extlink&oid=124267575&loc=SL82922352-210448

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher SEC
-Name Regulation S-K (SK)
-Number 229
-Section 1405
-Paragraph (a)
-Subparagraph (4)

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossWriteoffAfterRecovery
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of increase in allowance for credit loss on financing receivable from recovery.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 55
-Paragraph 79
-URI http://asc.fasb.org/extlink&oid=124267575&loc=SL82922352-210448

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(4)
-URI http://asc.fasb.org/extlink&oid=123577603&loc=SL6953423-111524

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of writeoff of financing receivable, charged against allowance for credit loss.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(3)
-URI http://asc.fasb.org/extlink&oid=123577603&loc=SL6953423-111524

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 55
-Paragraph 79
-URI http://asc.fasb.org/extlink&oid=124267575&loc=SL82922352-210448

+ Details

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of allowance for credit loss at acquisition date of financing receivable purchased with credit deterioration.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 19
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=124255953&loc=SL82919265-210447

+ Details

Name:	us-gaap_FinancingReceivablePurchasedWithCreditDeteriorationAllowanceForCreditLossAtAcquisitionDate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-URI http://asc.fasb.org/subtopic&trid=2196772

+ Details

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

- Definition

Amount of credit loss expense (reversal of expense) for financing receivable.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=124255953&loc=SL82919249-210447

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(11))
-URI http://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

+ Details

Name:	us-gaap_ProvisionForLoanLossesExpensed
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_BusinessAcquisitionAxis=ally_FairSquareFinancialHoldingsLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CumulativeEffectPeriodOfAdoptionAxis=srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CumulativeEffectPeriodOfAdoptionAxis=srt_CumulativeEffectPeriodOfAdoptionAdjustedBalanceMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ConsumerPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_AutomobileLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_RealEstateLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=ally_OtherLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Finance Receivables and Loans, Net (Allowance for Credit Losses on Financing Receivables) (Details) - USD ($) $ in Millions		12 Months Ended
	Dec. 01, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Allowance, beginning balance		$ 3,283	$ 1,263
Charge-offs		(981)	(1,326)
Recoveries		712	562
Net charge-offs		(269)	(764)
Provision for credit losses		241	1,439	$ 998
Other		12	(1)
Allowance, ending balance		3,267	3,283	1,263
Fair Square Financial Holdings LLC
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Financing receivable, purchased with credit deterioration, allowance for credit loss	$ 12
Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Allowance, beginning balance			1,346
Allowance, ending balance				1,346
Cumulative Effect, Period of Adoption, Adjusted Balance
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Allowance, beginning balance			2,609
Allowance, ending balance				2,609
Consumer \| Automotive
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Allowance, beginning balance		2,902	1,075
Charge-offs		(923)	(1,244)
Recoveries		686	542
Net charge-offs		(237)	(702)
Provision for credit losses		104	1,194
Other		0	1
Allowance, ending balance		2,769	2,902	1,075
Consumer \| Automotive \| Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Allowance, beginning balance			1,334
Allowance, ending balance				1,334
Consumer \| Automotive \| Cumulative Effect, Period of Adoption, Adjusted Balance
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Allowance, beginning balance			2,409
Allowance, ending balance				2,409
Consumer \| Mortgage/Real Estate
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Allowance, beginning balance		33	46
Charge-offs		(6)	(13)
Recoveries		13	16
Net charge-offs		7	3
Provision for credit losses		(14)	(10)
Other		1	0
Allowance, ending balance		27	33	46
Consumer \| Mortgage/Real Estate \| Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Allowance, beginning balance			(6)
Allowance, ending balance				(6)
Consumer \| Mortgage/Real Estate \| Cumulative Effect, Period of Adoption, Adjusted Balance
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Allowance, beginning balance			40
Allowance, ending balance				40
Consumer \| Other
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Allowance, beginning balance		73	9
Charge-offs		(30)	(15)
Recoveries		2	1
Net charge-offs		(28)	(14)
Provision for credit losses		163	62
Other		13	0
Allowance, ending balance		221	73	9
Finance receivables, fair value		7	8	11
Consumer \| Other \| Fair Square Financial Holdings LLC
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Provision for credit losses	$ 97
Consumer \| Other \| Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Allowance, beginning balance			16
Allowance, ending balance				16
Consumer \| Other \| Cumulative Effect, Period of Adoption, Adjusted Balance
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Allowance, beginning balance			25
Allowance, ending balance				25
Commercial
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Allowance, beginning balance		275	133
Charge-offs		(22)	(54)
Recoveries		11	3
Net charge-offs		(11)	(51)
Provision for credit losses		(12)	193
Other		(2)	(2)
Allowance, ending balance		$ 250	275	133
Commercial \| Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Allowance, beginning balance			2
Allowance, ending balance				2
Commercial \| Cumulative Effect, Period of Adoption, Adjusted Balance
Financing Receivable, Allowance for Loan and Lease Losses [Roll Forward]
Allowance, beginning balance			$ 135
Allowance, ending balance				$ 135