Segment Information - Schedule of Segment Reporting Information by Segment (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Mar. 31, 2022
Segment Reporting Information [Line Items]
Total financing revenues	$ 2,824	$ 3,032	$ 5,655	$ 6,031
Depreciation on operating leases	1,305	1,499	2,714	2,940
Interest expense	705	423	1,268	709
Net financing revenues	814	1,110	1,673	2,382
Voluntary protection contract revenues and insurance earned premiums	263	254	522	503
Investment and other income (loss), net	(138)	7	(444)	163
Net financing revenues and other revenues	939	1,371	1,751	3,048
Expenses:
Provision for credit losses	213	68	291	65
Operating and administrative	444	385	850	769
Voluntary protection contract expenses and insurance losses	114	99	221	207
Total expenses	771	552	1,362	1,041
Income before income taxes	168	819	389	2,007
Provision (benefit) for income taxes	49	197	100	464
Net income	119	622	289	1,543
Total assets	134,352	136,977	134,352	136,977	$ 135,041
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	0	0	0	0
Net financing revenues	0	0	0	0
Voluntary protection contract revenues and insurance earned premiums	0	0	0	0
Investment and other income (loss), net	0	0	0	0
Net financing revenues and other revenues	0	0	0	0
Expenses:
Provision for credit losses	0	0	0	0
Operating and administrative	0	0	0	0
Voluntary protection contract expenses and insurance losses	0	0	0	0
Total expenses	0	0	0	0
Income before income taxes	0	0	0	0
Provision (benefit) for income taxes	0	0	0	0
Net income	0	0	0	0
Total assets	(128)	(138)	(128)	(138)
Finance Operations [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total financing revenues	2,824	3,032	5,655	6,031
Depreciation on operating leases	1,305	1,499	2,714	2,940
Interest expense	705	423	1,268	709
Net financing revenues	814	1,110	1,673	2,382
Voluntary protection contract revenues and insurance earned premiums	0	0	0	0
Investment and other income (loss), net	55	9	88	28
Net financing revenues and other revenues	869	1,119	1,761	2,410
Expenses:
Provision for credit losses	213	68	291	65
Operating and administrative	339	287	638	579
Voluntary protection contract expenses and insurance losses	0	0	0	0
Total expenses	552	355	929	644
Income before income taxes	317	764	832	1,766
Provision (benefit) for income taxes	86	185	211	406
Net income	231	579	621	1,360
Total assets	128,403	130,544	128,403	130,544
Voluntary Protection 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
Voluntary protection contract revenues and insurance earned premiums	263	254	522	503
Investment and other income (loss), net	(193)	(2)	(532)	135
Net financing revenues and other revenues	70	252	(10)	638
Expenses:
Provision for credit losses	0	0	0	0
Operating and administrative	105	98	212	190
Voluntary protection contract expenses and insurance losses	114	99	221	207
Total expenses	219	197	433	397
Income before income taxes	(149)	55	(443)	241
Provision (benefit) for income taxes	(37)	12	(111)	58
Net income	(112)	43	(332)	183
Total assets	$ 6,077	$ 6,571	$ 6,077	$ 6,571