Segment Information - Schedule of Segment Reporting Information by Segment (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Mar. 31, 2015
Segment Reporting Information [Line Items]
Total financing revenues	$ 2,353	$ 2,057	$ 4,608	$ 4,017
Insurance earned premiums and contract revenues	178	160	352	313
Investment and other income, net	14	60	52	95
Total gross revenues	2,545	2,277	5,012	4,425
Depreciation on operating leases	1,446	1,196	2,806	2,296
Interest expense	203	215	711	345
Provision for credit losses	105	79	150	117
Operating and administrative expenses	287	253	557	486
Insurance losses and loss adjustment expenses	78	67	157	137
Provision for income taxes	161	176	231	389
Net income	265	291	400	655
Total assets	115,191	106,015	115,191	106,015	$ 109,625
Intercompany Eliminations [Member]
Segment Reporting Information [Line Items]
Total financing revenues	0	0	0	0
Insurance earned premiums and contract revenues	0	0	0	0
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	(1,021)	(894)	(1,021)	(894)
Finance Operations [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total financing revenues	2,353	2,057	4,608	4,017
Insurance earned premiums and contract revenues	0	0	0	0
Investment and other income, net	22	27	43	47
Total gross revenues	2,375	2,084	4,651	4,064
Depreciation on operating leases	1,446	1,196	2,806	2,296
Interest expense	203	215	711	345
Provision for credit losses	105	79	150	117
Operating and administrative expenses	225	200	434	380
Insurance losses and loss adjustment expenses	0	0	0	0
Provision for income taxes	150	149	201	345
Net income	246	245	349	581
Total assets	112,166	103,307	112,166	103,307
Insurance Operations [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total financing revenues	0	0	0	0
Insurance earned premiums and contract revenues	178	160	352	313
Investment and other income, net	(8)	33	9	48
Total gross revenues	170	193	361	361
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	62	53	123	106
Insurance losses and loss adjustment expenses	78	67	157	137
Provision for income taxes	11	27	30	44
Net income	19	46	51	74
Total assets	$ 4,046	$ 3,602	$ 4,046	$ 3,602