Face (par) amount of debt instrument at time of issuance.

Reference 1: 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 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

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

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

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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

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- 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

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

- Definition

Weighted average interest rate of debt outstanding.

+ References

No definition available.

+ Details

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

- Definition

Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28555-108399

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Period remaining on line of credit facility before it terminates, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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

- Definition

Amount of increase (decrease) of the credit facility.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(f))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

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

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Balance Type:
Period Type:

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Name:	srt_RangeAxis=srt_MaximumMember
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Name:	us-gaap_DebtInstrumentAxis=acf_SecuritizationNotesPayableMember
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Debt - Narrative (Details)	12 Months Ended
Debt - Narrative (Details)	Dec. 31, 2020 USD ($)	Jan. 31, 2021 USD ($)	Jan. 31, 2021 CAD ($)	Dec. 31, 2019 USD ($)
Revolving Credit Facilities [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Expiration period	6 years
Senior Notes [Member]
Debt Instrument [Line Items]
Weighted average interest rate (percent)	3.25%
Face amount of debt	$ 46,300,000,000
Senior Notes [Member] \| Senior Notes with Maturity Dates from 2023 to 2030 [Member]
Debt Instrument [Line Items]
Weighted average interest rate (percent)	2.93%
Face amount of debt	$ 9,200,000,000
Senior Notes [Member] \| Senior Notes Due with Maturity Dates from 2026 to 2031 [Member] \| Subsequent Event [Member]
Debt Instrument [Line Items]
Face amount of debt		$ 2,500,000,000
Interest rate (percent)		1.69%	1.69%
Senior Notes [Member] \| CAD Senior Notes Due 2026 [Member] \| Subsequent Event [Member]
Debt Instrument [Line Items]
Face amount of debt			$ 500,000,000
Interest rate (percent)		1.75%	1.75%
Line of Credit [Member]
Debt Instrument [Line Items]
Weighted average interest rate (percent)	2.47%
Debt instrument term	4 years
Unsecured Debt [Member]
Debt Instrument [Line Items]
Issuance costs	$ 106,000,000			$ 109,000,000
Secured Debt [Member]
Debt Instrument [Line Items]
Weighted average interest rate (percent)	1.89%
Issuance costs	$ 85,000,000			$ 75,000,000
Secured Debt [Member] \| Revolving Credit Facilities [Member]
Debt Instrument [Line Items]
Increase in credit facilities	$ 21,100,000,000
Secured Debt [Member] \| Securitization Notes Payable [Member]
Debt Instrument [Line Items]
Weighted average interest rate (percent)	1.17%
Face amount of debt	$ 24,600,000,000