Ally has the right to defer payments of interest for a period not exceeding consecutive quarters of

No definition available.

Name:	ally_Allyhastherighttodeferpaymentsofinterestforaperiodnotexceedingconsecutivequartersof
Namespace Prefix:	ally_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Debt redeemed during period, number of shares

+ References

No definition available.

+ Details

Name:	ally_DebtRedeemedDuringPeriodNumberOfShares
Namespace Prefix:	ally_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Distributions will be payable at an annual rate equal to three-month London interbank offer rate plus:

+ References

No definition available.

+ Details

Name:	ally_DistributionswillbepayableatanannualrateequaltothreemonthLondoninterbankofferrateplus
Namespace Prefix:	ally_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percent of principal debt, plus accrued and unpaid interest is the redemption price if Ally redeems the Series 2 TRUPS at anytime on or before February 15, 2040.

+ References

No definition available.

+ Details

Name:	ally_PercentofprincipaldebtplusaccruedandunpaidinterestistheredemptionpriceifAllyredeemstheSeries2TRUPSatanytimeonorbeforeFebruary152040.
Namespace Prefix:	ally_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Trust preferred securities

+ References

No definition available.

+ Details

Name:	ally_TrustPreferredSecurities
Namespace Prefix:	ally_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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 cash outflow to reacquire preferred stocks issued by a business trust or other special purpose entity, mainly established by a bank holding entity, to third party investors. The trust's assets are deeply subordinated debentures of the bank holding entity. Most trust preferred securities are subject to a mandatory redemption upon the repayment of the debentures.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3291-108585

+ Details

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

- Definition

The per share liquidation preference (or restrictions) of nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer) that has a preference in involuntary liquidation considerably in excess of the par or stated value of the shares. The liquidation preference is the difference between the preference in liquidation and the par or stated values of the share.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(d))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21475-112644

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(28))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21484-112644

+ Details

Name:	us-gaap_PreferredStockLiquidationPreference
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Proceeds from issuance of capital stock which provides for a specific dividend that is paid to the shareholders before any dividends to common stockholders and which takes precedence over common stockholders in the event of liquidation.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3255-108585

+ Details

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

- Definition

Amount of Tier 1 leverage capital as defined by regulatory framework.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 505
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=117337116&loc=SL5958568-112826

+ Details

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

- Details

Name:	us-gaap_StatementClassOfStockAxis=us-gaap_SeriesBPreferredStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=us-gaap_SeriesCPreferredStockMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=us-gaap_TrustPreferredSecuritiesSubjectToMandatoryRedemptionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_VariableIncomeInterestRateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_TrustPreferredSecuritiesSubjectToMandatoryRedemptionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Debt (Narrative - Trust Preferred Securities) (Details) $ / shares in Units, $ in Millions				6 Months Ended
	Jul. 02, 2021 USD ($) shares	Jun. 02, 2021 USD ($)	Apr. 22, 2021 USD ($) shares	Jun. 30, 2021 USD ($) quarter $ / shares	Jun. 30, 2020 USD ($)	Apr. 30, 2021 $ / shares	Dec. 31, 2020 USD ($)
Debt Instrument [Line Items]
Trust preferred securities				$ 1,200			$ 2,600
Liquidation preference (in dollars per share) \| $ / shares				$ 25
Distribution payable in addition to annual rate equal to three-month London interbank offer rate, percentage				5.785%
Period of consecutive quarters for which Ally has right to defer interest payments, maximum \| quarter				20
Redemption price, percentage of principal debt, plus accrued and unpaid interest				100.00%
Preferred stock issuance				$ 2,326	$ 0
Trust preferred securities redemption				$ 1,442	$ 0
Series B Preferred Stock
Debt Instrument [Line Items]
Liquidation preference (in dollars per share) \| $ / shares				$ 1,000		$ 1,000
Preferred stock issuance			$ 1,350
Series C Preferred Stock
Debt Instrument [Line Items]
Liquidation preference (in dollars per share) \| $ / shares				$ 1,000
Preferred stock issuance		$ 1,000
Trust Preferred Securities Subject to Mandatory Redemption
Debt Instrument [Line Items]
Trust preferred securities redemption			$ 1,400
Debt redeemed during period, number of shares \| shares			56,000,000
Trust Preferred Securities Subject to Mandatory Redemption \| Subsequent event
Debt Instrument [Line Items]
Trust preferred securities redemption	$ 1,040
Debt redeemed during period, number of shares \| shares	41,600,000
Variable Income Interest Rate
Debt Instrument [Line Items]
Trust preferred securities				$ 1,200			$ 2,600
Trust Preferred Securities Subject to Mandatory Redemption
Debt Instrument [Line Items]
Series 2 TRUPS included in Tier 1 capital				$ 181