GM Financial Receivables and Transactions - Allowance for Loan Losses (Details) - GM Financial [Member] - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses at beginning of period	$ 944	$ 911
Provision for loan losses	466	175
Charge-offs	(340)	(309)
Recoveries	156	145
Effect of foreign currency	(61)	2
Allowance for loan losses at end of period	1,966	$ 924
Impact of Adoption ASU 2016-13 [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for loan losses at beginning of period	$ 801

Amount of gain (loss) from converting allowance reserve for credit loss to currency of reporting entity from amount denominated or measured in a different currency, which decreases (increases) the allowance for loan and lease losses.

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Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

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Amount of recovery of financing receivables doubtful of collection that were previously charged off.

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

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

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Amount of expense related loan transactions, lease transactions, credit loss from transactions other than loan and lease transactions, and other loss based on assessment of uncollectability from the counterparty to reduce the account to their net realizable value.

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