The increase in the maximum borrowing capacity of the facility during the period.

No definition available.

Name:	gm_LineOfCreditIncreaseMaximumBorrowingCapacity
Namespace Prefix:	gm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

+ Details

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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

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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

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

- Definition

Weighted average interest rate of long-term debt outstanding calculated at point in time.

+ References

No definition available.

+ Details

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

- Definition

The cash outflow for the settlement of obligation drawn from a contractual arrangement with the lender, including letter of credit, standby letter of credit and revolving credit arrangements, under which borrowings can be made up to a specific amount at any point in time with maturities due beyond one year or the operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3291-108585

+ Details

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

- Details

Name:	gm_BusinessGroupAxis=gm_AutomotiveMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	gm_DebtTypeAxis=us-gaap_UnsecuredDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	gm_BusinessGroupAxis=gm_GmFinancialMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	gm_DebtTypeAxis=us-gaap_SecuredDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_DebtInstrumentAxis=gm_SecuritizationNotesPayableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByMeasurementBasisAxis=us-gaap_EstimateOfFairValueFairValueDisclosureMember
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Data Type:	na
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Automotive and GM Financial Debt Secured Debt and Unsecured Debt (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2017	Jan. 31, 2018	Aug. 31, 2017	Dec. 31, 2016
Automotive [Member]
Debt Instrument [Line Items]
Weighted-average interest rate on outstanding long-term debt		5.20%			5.20%
Revolving Credit Facility [Member] \| Automotive [Member] \| Unsecured Debt [Member]
Debt Instrument [Line Items]
Repayments of lines of credit	$ 3,000
Debt term	3 years
Revolving Credit Facility [Member] \| GM Financial [Member] \| Unsecured Debt [Member]
Debt Instrument [Line Items]
Weighted-average interest rate		7.28%
Revolving Credit Facility [Member] \| GM Financial [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Increase to maximum borrowing capacity		$ 2,900
Maximum [Member] \| Revolving Credit Facility [Member] \| GM Financial [Member] \| Unsecured Debt [Member]
Debt Instrument [Line Items]
Debt term		4 years
Senior Notes [Member] \| Automotive [Member] \| Unsecured Debt [Member]
Debt Instrument [Line Items]
Amount of debt issued				$ 3,000
Senior Notes [Member] \| GM Financial [Member] \| Unsecured Debt [Member]
Debt Instrument [Line Items]
Amount of debt issued		$ 12,700
Weighted-average interest rate		2.85%
Weighted-average interest rate on outstanding long-term debt		3.27%
Senior Notes [Member] \| GM Financial [Member] \| Subsequent Event [Member] \| Unsecured Debt [Member]
Debt Instrument [Line Items]
Amount of debt issued			$ 1,650
Weighted-average interest rate			3.26%
Notes Payable, Other Payables [Member] \| Automotive [Member] \| Unsecured Debt [Member] \| Securitization notes payable [Member]
Debt Instrument [Line Items]
Weighted-average interest rate				4.50%
Notes Payable, Other Payables [Member] \| GM Financial [Member] \| Secured Debt [Member] \| Securitization notes payable [Member]
Debt Instrument [Line Items]
Amount of debt issued		$ 22,400
Weighted-average interest rate		2.10%
Weighted-average interest rate on outstanding long-term debt		2.37%
Estimate of Fair Value Measurement [Member]
Debt Instrument [Line Items]
Debt term		18 months