Selected Quarterly Financial Data - Selected Quarterly Financial Data (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Financing revenues:
Operating lease	$ 1,958	$ 1,946	$ 1,925	$ 1,891	$ 1,861	$ 1,795	$ 1,789	$ 1,696	$ 7,720	$ 7,141	$ 6,113
Retail	467	468	459	456	453	484	465	457	1,850	1,859	1,797
Dealer	130	123	112	111	105	97	99	102	476	403	400
Total financing revenues	2,555	2,537	2,496	2,458	2,419	2,376	2,353	2,255	10,046	9,403	8,310
Depreciation on operating leases	1,859	1,722	1,683	1,589	1,605	1,503	1,446	1,360	6,853	5,914	4,857
Interest expense	449	701	297	307	149	277	203	508	1,754	1,137	736
Net financing revenues	247	114	516	562	665	596	704	387	1,439	2,352	2,717
Insurance earned premiums and contract revenues	210	202	199	193	186	181	178	174	804	719	638
Investment and other income, net	37	52	42	39	29	67	35	27	170	158	124
Realized gains (losses), net on investments in marketable securities	(14)	157	70	13	16	0	(21)	11	226	6	70
Gain on sale of commercial finance business					0	197	0	0	0	197	0
Net financing revenues and other revenues	480	525	827	807	896	1,041	896	599	2,639	3,432	3,549
Expenses:
Provision for credit losses	186	183	161	52	163	128	105	45	582	441	308
Operating and administrative	356	325	317	279	316	288	287	270	1,277	1,161	1,046
Insurance losses and loss adjustment expenses	99	92	91	89	88	73	78	79	371	318	269
Total expenses	641	600	569	420	567	489	470	394	2,230	1,920	1,623
Income before income taxes	(161)	(75)	258	387	329	552	426	205	409	1,512	1,926
Provision (benefit) for income taxes	(70)	(29)	95	146	139	210	161	70	142	580	729
Net income	$ (91)	$ (46)	$ 163	$ 241	$ 190	$ 342	$ 265	$ 135	$ 267	$ 932	$ 1,197