Segment Information - Schedule of Segment Reporting Information by Segment (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Mar. 31, 2016
Segment Reporting Information [Line Items]
Total financing revenues	$ 2,496	$ 2,353	$ 4,954	$ 4,608
Insurance earned premiums and contract revenues	199	178	392	352
Investment and other income, net	112	14	164	52
Total gross revenues	2,807	2,545	5,510	5,012
Depreciation on operating leases	1,683	1,446	3,272	2,806
Interest expense	297	203	604	711
Provision for credit losses	161	105	213	150
Operating and administrative expenses	317	287	596	557
Insurance losses and loss adjustment expenses	91	78	180	157
Provision for income taxes	95	161	241	231
Net income	163	265	404	400
Total assets	115,793	115,070	115,793	115,070	$ 114,592
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	(979)	(1,021)	(979)	(1,021)
Finance Operations [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total financing revenues	2,496	2,353	4,954	4,608
Insurance earned premiums and contract revenues	0	0	0	0
Investment and other income, net	100	22	134	43
Total gross revenues	2,596	2,375	5,088	4,651
Depreciation on operating leases	1,683	1,446	3,272	2,806
Interest expense	297	203	604	711
Provision for credit losses	161	105	213	150
Operating and administrative expenses	242	225	452	434
Insurance losses and loss adjustment expenses	0	0	0	0
Provision for income taxes	80	150	205	201
Net income	133	246	342	349
Total assets	112,355	112,045	112,355	112,045
Insurance Operations [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total financing revenues	0	0	0	0
Insurance earned premiums and contract revenues	199	178	392	352
Investment and other income, net	12	(8)	30	9
Total gross revenues	211	170	422	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	75	62	144	123
Insurance losses and loss adjustment expenses	91	78	180	157
Provision for income taxes	15	11	36	30
Net income	30	19	62	51
Total assets	$ 4,417	$ 4,046	$ 4,417	$ 4,046