Commitments and Contingencies (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Loss Contingencies [Line Items]
Rent expense	$ 38
Operating lease right-of-use asset		$ 129
Operating lease liabilities		$ 144
Operating lease right-of-use asset obtained in exchange for lease obligations	36
2020	27
2021	27
2022	25
2023	21
2024	20
Thereafter	67
Imputed interest	$ 29
Weighted-average discount rate	4.40%
Weighted average remaining lease term	7 years 10 months 15 days
Estimate of possible loss	$ 53
Loss contingency accrual	19
Indirect tax contingency	13
Other Liabilities [Member]
Loss Contingencies [Line Items]
Operating lease liabilities	158
Other Assets [Member]
Loss Contingencies [Line Items]
Operating lease right-of-use asset	137
Senior Notes [Member]
Loss Contingencies [Line Items]
Face amount of debt	43,700
Senior Notes [Member] | Euro Medium Term Notes [Member] | GM [Member]
Loss Contingencies [Line Items]
Face amount of debt	$ 561		$ 1,100
Retail Finance Receivable [Member] | Texas [Member] | Geographic Concentration Risk [Member]
Loss Contingencies [Line Items]
Concentration risk (percent)	12.50%
Maximum [Member] | Administrative Offices And Other [Member]
Loss Contingencies [Line Items]
Term of contract	11 years