Segment Information - Schedule of Segment Reporting Information by Segment (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Mar. 31, 2019
Segment Reporting Information [Line Items]
Total financing revenues	$ 3,018	$ 2,890	$ 5,981	$ 5,726
Depreciation on operating leases	1,583	1,662	3,208	3,428
Interest expense	613	702	1,310	1,384
Net financing revenues	822	526	1,463	914
Insurance earned premiums and contract revenues	232	226	461	450
Investment and other income, net	97	56	215	96
Net financing revenues and other revenues	1,151	808	2,139	1,460
Expenses:
Provision for credit losses	61	67	136	156
Operating and administrative expenses	358	348	695	672
Insurance losses and loss adjustment expenses	115	112	228	237
Total expenses	534	527	1,059	1,065
Income before income taxes	617	281	1,080	395
Provision for income taxes	158	87	262	109
Net income	459	194	818	286
Total assets	119,938	121,060	119,938	121,060	$ 116,516
Intercompany Eliminations [Member]
Segment Reporting Information [Line Items]
Total financing revenues	0	0	0	0
Depreciation on operating leases	0	0	0	0
Interest expense	(6)	(5)	(12)	(10)
Net financing revenues	6	5	12	10
Insurance earned premiums and contract revenues	0	0	0	0
Investment and other income, net	(6)	(5)	(12)	(10)
Net financing revenues and other revenues	0	0	0	0
Expenses:
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
Total expenses	0	0	0	0
Income before income taxes	0	0	0	0
Provision for income taxes	0	0	0	0
Net income	0	0	0	0
Total assets	(1,190)	(1,160)	(1,190)	(1,160)
Finance Operations [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total financing revenues	3,018	2,890	5,981	5,726
Depreciation on operating leases	1,583	1,662	3,208	3,428
Interest expense	619	707	1,322	1,394
Net financing revenues	816	521	1,451	904
Insurance earned premiums and contract revenues	0	0	0	0
Investment and other income, net	38	51	75	99
Net financing revenues and other revenues	854	572	1,526	1,003
Expenses:
Provision for credit losses	61	67	136	156
Operating and administrative expenses	268	262	514	503
Insurance losses and loss adjustment expenses	0	0	0	0
Total expenses	329	329	650	659
Income before income taxes	525	243	876	344
Provision for income taxes	136	77	212	96
Net income	389	166	664	248
Total assets	115,714	117,265	115,714	117,265
Insurance Operations [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total financing revenues	0	0	0	0
Depreciation on operating leases	0	0	0	0
Interest expense	0	0	0	0
Net financing revenues	0	0	0	0
Insurance earned premiums and contract revenues	232	226	461	450
Investment and other income, net	65	10	152	7
Net financing revenues and other revenues	297	236	613	457
Expenses:
Provision for credit losses	0	0	0	0
Operating and administrative expenses	90	86	181	169
Insurance losses and loss adjustment expenses	115	112	228	237
Total expenses	205	198	409	406
Income before income taxes	92	38	204	51
Provision for income taxes	22	10	50	13
Net income	70	28	154	38
Total assets	$ 5,414	$ 4,955	$ 5,414	$ 4,955