Segment Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Mar. 31, 2014
Segment Reporting Information [Line Items]
Total financing revenues	$ 2,112	$ 1,876	$ 6,129	$ 5,516
Insurance earned premiums and contract revenues	159	141	472	423
Investment and other income, net	62	68	157	88
Total gross revenues	2,333	2,085	6,758	6,027
Depreciation on operating leases	1,248	1,033	3,544	2,950
Interest expense	161	386	506	1,236
Provision for credit losses	103	63	220	102
Operating and administrative expenses	266	240	752	700
Insurance losses and loss adjustment expenses	63	57	200	196
Provision for income taxes	185	113	574	315
Net income	307	193	962	528
Total assets	106,848	99,651	106,848	99,651	102,740
Intercompany Eliminations [Member]
Segment Reporting Information [Line Items]
Total financing revenues	0	7	0	21
Insurance earned premiums and contract revenues	0	(7)	0	(21)
Investment and other income, net	0	0	0	0
Total gross revenues	0	0	0	0
Depreciation on operating leases	0	0	0	0
Interest expense	0	0	0	0
Provision for credit losses	0	0	0	0
Operating and administrative expenses	0	0	0	0
Insurance losses and loss adjustment expenses	0	0	0	0
Provision for income taxes	0	0	0	0
Net income	0	0	0	0
Total assets	(903)	(665)	(903)	(665)
Finance Operations [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total financing revenues	2,112	1,869	6,129	5,495
Insurance earned premiums and contract revenues	0	0	0	0
Investment and other income, net	20	22	67	56
Total gross revenues	2,132	1,891	6,196	5,551
Depreciation on operating leases	1,248	1,033	3,544	2,950
Interest expense	161	386	506	1,236
Provision for credit losses	103	63	220	102
Operating and administrative expenses	209	190	589	553
Insurance losses and loss adjustment expenses	0	0	0	0
Provision for income taxes	155	82	500	267
Net income	256	137	837	443
Total assets	104,068	96,665	104,068	96,665
Insurance Operations [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total financing revenues	0	0	0	0
Insurance earned premiums and contract revenues	159	148	472	444
Investment and other income, net	42	46	90	32
Total gross revenues	201	194	562	476
Depreciation on operating leases	0	0	0	0
Interest expense	0	0	0	0
Provision for credit losses	0	0	0	0
Operating and administrative expenses	57	50	163	147
Insurance losses and loss adjustment expenses	63	57	200	196
Provision for income taxes	30	31	74	48
Net income	51	56	125	85
Total assets	$ 3,683	$ 3,651	$ 3,683	$ 3,651