Segment Information - Schedule of Segment Reporting Information by Segment (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
Segment Reporting Information [Line Items]
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
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
Total gross revenues									11,246	10,483	9,142
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
Provision for credit losses	186	183	161	52	163	128	105	45	582	441	308
Operating and administrative expenses	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
Provision 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
Total assets	119,635				114,592				119,635	114,592	109,503
Intercompany Eliminations [Member]
Segment Reporting Information [Line Items]
Total financing revenues									0	0	0
Insurance earned premiums and contract revenues									0	0	0
Investment and other income, net									(5)	0	0
Realized gains (losses), net on investments in marketable securities									0	0	0
Gain on sale of commercial finance business									0	0	0
Total gross revenues									(5)	0	0
Depreciation on operating leases									0	0	0
Interest expense									(5)	0	0
Provision for credit losses									0	0	0
Operating and administrative expenses									0	0	0
Insurance losses and loss adjustment expenses									0	0	0
Provision for income taxes									0	0	0
Net income									0	0	0
Total assets	(1,083)				(1,065)				(1,083)	(1,065)	(919)
Finance Operations [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total financing revenues									10,046	9,403	8,310
Insurance earned premiums and contract revenues									0	0	0
Investment and other income, net									96	59	49
Realized gains (losses), net on investments in marketable securities									241	40	40
Gain on sale of commercial finance business									0	197	0
Total gross revenues									10,383	9,699	8,399
Depreciation on operating leases									6,853	5,914	4,857
Interest expense									1,759	1,137	736
Provision for credit losses									582	441	308
Operating and administrative expenses									979	909	825
Insurance losses and loss adjustment expenses									0	0	0
Provision for income taxes									67	501	635
Net income									143	797	1,038
Total assets	116,242				111,496				116,242	111,496	106,531
Insurance Operations [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total financing revenues									0	0	0
Insurance earned premiums and contract revenues									804	719	638
Investment and other income, net									79	99	75
Realized gains (losses), net on investments in marketable securities									(15)	(34)	30
Gain on sale of commercial finance business									0	0	0
Total gross revenues									868	784	743
Depreciation on operating leases									0	0	0
Interest expense									0	0	0
Provision for credit losses									0	0	0
Operating and administrative expenses									298	252	221
Insurance losses and loss adjustment expenses									371	318	269
Provision for income taxes									75	79	94
Net income									124	135	159
Total assets	$ 4,476				$ 4,161				$ 4,476	$ 4,161	$ 3,891