Segment Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Mar. 31, 2014
Segment Reporting Information [Line Items]
Total financing revenues	$ 2,057	$ 1,845	$ 4,017	$ 3,640
Insurance earned premiums and contract revenues	160	143	313	282
Investment and other income, net	60	14	95	20
Total gross revenues	2,277	2,002	4,425	3,942
Depreciation on operating leases	1,196	966	2,296	1,917
Interest expense	215	314	345	850
Provision for credit losses	79	28	117	39
Operating and administrative expenses	253	233	486	460
Insurance losses and loss adjustment expenses	67	68	137	139
Provision for income taxes	176	149	389	202
Net income	291	244	655	335
Total assets	106,015	98,083	106,015	98,083	102,740
Intercompany Eliminations [Member]
Segment Reporting Information [Line Items]
Total financing revenues	0	7	0	14
Insurance earned premiums and contract revenues	0	(7)	0	(14)
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	(894)	(669)	(894)	(669)
Finance Operations [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total financing revenues	2,057	1,838	4,017	3,626
Insurance earned premiums and contract revenues	0	0	0	0
Investment and other income, net	27	22	47	34
Total gross revenues	2,084	1,860	4,064	3,660
Depreciation on operating leases	1,196	966	2,296	1,917
Interest expense	215	314	345	850
Provision for credit losses	79	28	117	39
Operating and administrative expenses	200	183	380	363
Insurance losses and loss adjustment expenses	0	0	0	0
Provision for income taxes	149	140	345	185
Net income	245	229	581	306
Total assets	103,307	95,139	103,307	95,139
Insurance Operations [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total financing revenues	0	0	0	0
Insurance earned premiums and contract revenues	160	150	313	296
Investment and other income, net	33	(8)	48	(14)
Total gross revenues	193	142	361	282
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	53	50	106	97
Insurance losses and loss adjustment expenses	67	68	137	139
Provision for income taxes	27	9	44	17
Net income	46	15	74	29
Total assets	$ 3,602	$ 3,613	$ 3,602	$ 3,613