Segment Information - Schedule of Segment Reporting Information by Segment (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013
Segment Reporting Information [Line Items]
Total financing revenues	$ 2,181	$ 2,112	$ 2,057	$ 1,960	$ 1,881	$ 1,876	$ 1,845	$ 1,795	$ 8,310	$ 7,397	$ 7,244
Insurance earned premiums and contract revenues									638	567	571
Investment and other income, net									194	135	173
Total gross revenue									9,142	8,099	7,988
Depreciation on operating leases	1,313	1,248	1,196	1,100	1,062	1,033	966	951	4,857	4,012	3,568
Interest expense	230	161	215	130	104	386	314	536	736	1,340	940
Provision for credit losses	88	103	79	38	68	63	28	11	308	170	121
Operating and administrative expenses									1,046	965	911
Insurance losses and loss adjustment expenses									269	258	293
Provision for income taxes	155	185	176	213	182	113	149	53	729	497	824
Net income	235	307	291	364	329	193	244	91	1,197	857	1,331
Total assets	109,625				102,740				109,625	102,740	95,302
Intercompany Eliminations [Member]
Segment Reporting Information [Line Items]
Total financing revenues									0	26	25
Insurance earned premiums and contract revenues									0	(26)	(25)
Investment and other income, net									0	0	0
Total gross revenue									0	0	0
Depreciation on operating leases									0	0	0
Interest expense									0	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	(919)				(725)				(919)	(725)	(704)
Finance Operations [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total financing revenues									8,310	7,371	7,219
Insurance earned premiums and contract revenues									0	0	0
Investment and other income, net									89	98	57
Total gross revenue									8,399	7,469	7,276
Depreciation on operating leases									4,857	4,012	3,568
Interest expense									736	1,340	940
Provision for credit losses									308	170	121
Operating and administrative expenses									825	767	734
Insurance losses and loss adjustment expenses									0	0	0
Provision for income taxes									635	437	730
Net income									1,038	743	1,183
Total assets	106,653				99,737				106,653	99,737	92,504
Insurance Operations [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total financing revenues									0	0	0
Insurance earned premiums and contract revenues									638	593	596
Investment and other income, net									105	37	116
Total gross revenue									743	630	712
Depreciation on operating leases									0	0	0
Interest expense									0	0	0
Provision for credit losses									0	0	0
Operating and administrative expenses									221	198	177
Insurance losses and loss adjustment expenses									269	258	293
Provision for income taxes									94	60	94
Net income									159	114	148
Total assets	$ 3,891				$ 3,728				$ 3,891	$ 3,728	$ 3,502