Equity in Net Assets of Non-consolidated Affiliates (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Schedule of Equity Method Investments [Line Items]
Assets	$ 113,825,000,000	$ 109,217,000,000
Total liabilities	100,227,000,000	96,491,000,000
Finance charge income	3,996,000,000	4,071,000,000	$ 3,629,000,000
Provision for loan losses (Note 3)	881,000,000	726,000,000	642,000,000
Net income	2,009,000,000	1,567,000,000	1,570,000,000
Undistributed earnings of foreign subsidiaries	373,000,000	409,000,000
Non-consolidated affiliates [Member]
Schedule of Equity Method Investments [Line Items]
Finance receivables, net	22,063,000,000	18,358,000,000
Assets	24,722,000,000	19,594,000,000
Debt	18,236,000,000	14,321,000,000
Total liabilities	21,177,000,000	16,352,000,000
Finance charge income	1,447,000,000	1,369,000,000	1,246,000,000
Provision for loan losses (Note 3)	162,000,000	47,000,000	21,000,000
Income before income taxes	572,000,000	630,000,000	696,000,000
Net income	426,000,000	473,000,000	522,000,000
Undistributed earnings of foreign subsidiaries	$ 647,000,000	$ 615,000,000
SAIC-GMAC [Member]
Schedule of Equity Method Investments [Line Items]
Ownership percentage	35.00%	35.00%
Cash dividends received	$ 103,000,000	$ 49,000,000	$ 0
SAIC-GMF Leasing Co. LTD [Member]
Schedule of Equity Method Investments [Line Items]
Ownership percentage	35.00%	35.00%
SAIC-GMAC [Member]
Schedule of Equity Method Investments [Line Items]
Dividends paid	$ 294,000,000	$ 140,000,000