Debt Instrument, Renewal Term

No definition available.

Name:	acf_DebtInstrumentRenewalTerm
Namespace Prefix:	acf_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Line of Credit Facilities, Related Party Facility

+ References

No definition available.

+ Details

Name:	acf_LineofCreditFacilitiesRelatedPartyFacility
Namespace Prefix:	acf_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- 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

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 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Definition

The amount of any current tax-related balances due to affiliates as of the date of each statement of financial position presented.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 17
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32809-109319

+ Details

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

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

- Definition

Purchases during the period (excluding transactions that are eliminated in consolidated or combined financial statements) with related party.

+ References

No definition available.

+ Details

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

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=srt_AffiliatedEntityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=acf_JuniorSubordinatedRevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=acf_GeneralMotorsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_CreditFacilityAxis=acf_ThreeHundredandSixtyFourDayRevolvingCreditFacilitiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=acf_PurchaseofRetailFinanceReceivablesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=srt_ParentCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Related Party Transactions - Narrative (Details) - USD ($)	1 Months Ended	9 Months Ended		12 Months Ended
	Apr. 30, 2019	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Affiliated Entity [Member]
Related Party Transaction [Line Items]
Tax expense due to related party		$ 4,000,000		$ 0
Junior Subordinated Revolving Credit Facility [Member] \| General Motors [Member]
Related Party Transaction [Line Items]
Line of credit facilities - GM Related party facility		1,000,000,000
Line of Credit [Member] \| Three Hundred and Sixty-Four Day Revolving Credit Facilities [Member] \| General Motors [Member]
Related Party Transaction [Line Items]
Debt instrument term	364 days
Maximum borrowing capacity	$ 2,000,000,000
Debt instrument renewal term	364 days
Purchase of Retail Finance Receivables [Member] \| Parent Company [Member]
Related Party Transaction [Line Items]
Related party purchases		$ 689,000,000	$ 371,000,000