GM Financial Receivables and Transactions - Summary of Finance Receivables (Details) - GM Financial [Member] - USD ($) $ in Millions	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Finance Receivables [Line Items]
GM Financial receivables, net of fees	$ 53,961		$ 53,900
Less: allowance for loan losses	(2,111)	$ (1,966)	(944)	$ (957)	$ (924)	$ (911)
GM Financial receivables, net	51,850		52,956
Retail Finance Receivables [Member]
Finance Receivables [Line Items]
GM Financial receivables, net of fees	46,472		42,229
Less: allowance for loan losses	(2,044)		(866)
GM Financial receivables, net	44,428		41,363
Commercial Finance Receivables [Member]
Finance Receivables [Line Items]
GM Financial receivables, net of fees	7,489		11,671
Less: allowance for loan losses	(67)		(78)
GM Financial receivables, net	7,422		11,593
Dealer cash management balance	1,300		1,200
Level 2 [Member]
Finance Receivables [Line Items]
Fair value of GM Financial receivables	7,422		11,593
Level 3 [Member]
Finance Receivables [Line Items]
Fair value of GM Financial receivables	$ 46,603		$ 41,973