Selected Quarterly Financial Data (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Net Deferred Federal Tax Expense/(Benefit) Related to Tax Cuts and Jobs Act									$ 1,400
Total revenue	$ 2,981	$ 2,863	$ 2,802	$ 2,731	$ 2,817	$ 2,796	$ 2,688	$ 2,608	11,377	$ 10,909	$ 9,697
Depreciation on vehicles subject to operating leases	(1,045)	(989)	(1,037)	(1,064)	(1,155)	(1,085)	(1,075)	(1,014)	(4,135)	(4,329)	(3,640)
Interest expense	(867)	(810)	(769)	(729)	(725)	(697)	(687)	(646)	(3,175)	(2,755)	(2,416)
Net Financing Margin, Insurance Premiums Earned and Other Income, net					937	1,014	926	948		3,825
Total financing margin and other revenue	1,069	1,064	996	938					4,067	3,495	3,357
Provision for credit losses	168	169	99	152	144	138	137	128	588	547	347
Net income	$ 1,814	$ 414	$ 446	$ 333	$ 333	$ 386	$ 296	$ 358	$ 3,007	$ 1,373	$ 1,363