GM Financial Receivables and Transactions Commercial Finance Receivables Credit Quality Indicators (Details) - GM Financial [Member] - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment [Line Items]
GM Financial receivables	$ 45,874	$ 42,671
Commercial Finance Receivables [Member]
Financing Receivable, Recorded Investment [Line Items]
GM Financial receivables	10,319	9,957
Commercial Finance Receivables [Member] | Group I - Dealers with superior financial metrics [Member]
Financing Receivable, Recorded Investment [Line Items]
GM Financial receivables	1,945	1,915
Commercial Finance Receivables [Member] | Group II - Dealers with strong financial metrics [Member]
Financing Receivable, Recorded Investment [Line Items]
GM Financial receivables	3,939	3,465
Commercial Finance Receivables [Member] | Group III - Dealers with fair financial metrics [Member]
Financing Receivable, Recorded Investment [Line Items]
GM Financial receivables	2,992	3,239
Commercial Finance Receivables [Member] | Group IV - Dealers with weak financial metrics [Member]
Financing Receivable, Recorded Investment [Line Items]
GM Financial receivables	970	997
Commercial Finance Receivables [Member] | Group V - Dealers warranting special mention due to potential weaknesses [Member]
Financing Receivable, Recorded Investment [Line Items]
GM Financial receivables	396	260
Commercial Finance Receivables [Member] | Group VI - Dealers with loans classified as substandard, doubtful or impaired [Member]
Financing Receivable, Recorded Investment [Line Items]
GM Financial receivables	$ 77	$ 81