Segment Information - Schedule of Segment Reporting Information by Segment (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Mar. 31, 2019
Segment Reporting Information [Line Items]
Total financing revenues	$ 3,044	$ 2,968	$ 9,025	$ 8,694
Depreciation on operating leases	1,712	1,717	4,920	5,145
Interest expense	755	699	2,065	2,083
Net financing revenues	577	552	2,040	1,466
Insurance earned premiums and contract revenues	231	226	692	676
Investment and other income, net	57	68	272	164
Net financing revenues and other revenues	865	846	3,004	2,306
Expenses:
Provision for credit losses	128	110	264	266
Operating and administrative expenses	406	347	1,101	1,019
Insurance losses and loss adjustment expenses	116	106	344	343
Total expenses	650	563	1,709	1,628
Income before income taxes	215	283	1,295	678
Provision for income taxes	34	69	296	178
Net income	181	214	999	500
Total assets	122,607	119,122	122,607	119,122	$ 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	(4)	(6)	(16)	(16)
Net financing revenues	4	6	16	16
Insurance earned premiums and contract revenues	0	0	0	0
Investment and other income, net	(4)	(6)	(16)	(16)
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	(1,112)	(1,077)	(1,112)	(1,077)
Finance Operations [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total financing revenues	3,044	2,968	9,025	8,694
Depreciation on operating leases	1,712	1,717	4,920	5,145
Interest expense	759	705	2,081	2,099
Net financing revenues	573	546	2,024	1,450
Insurance earned premiums and contract revenues	0	0	0	0
Investment and other income, net	42	43	117	142
Net financing revenues and other revenues	615	589	2,141	1,592
Expenses:
Provision for credit losses	128	110	264	266
Operating and administrative expenses	318	259	832	762
Insurance losses and loss adjustment expenses	0	0	0	0
Total expenses	446	369	1,096	1,028
Income before income taxes	169	220	1,045	564
Provision for income taxes	23	54	235	150
Net income	146	166	810	414
Total assets	118,228	115,319	118,228	115,319
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	231	226	692	676
Investment and other income, net	19	31	171	38
Net financing revenues and other revenues	250	257	863	714
Expenses:
Provision for credit losses	0	0	0	0
Operating and administrative expenses	88	88	269	257
Insurance losses and loss adjustment expenses	116	106	344	343
Total expenses	204	194	613	600
Income before income taxes	46	63	250	114
Provision for income taxes	11	15	61	28
Net income	35	48	189	86
Total assets	$ 5,491	$ 4,880	$ 5,491	$ 4,880