Segment Information - Schedule of Segment Reporting Information by Segment (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Mar. 31, 2021
Segment Reporting Information [Line Items]
Total financing revenues	$ 2,991	$ 2,974	$ 9,022	$ 8,821
Depreciation on operating leases	1,460	1,450	4,400	4,484
Interest expense	346	491	1,055	1,534
Net financing revenues	1,185	1,033	3,567	2,803
Voluntary protection contract revenues and insurance earned premiums	255	241	758	714
Investment and other income, net	76	179	239	445
Net financing revenues and other revenues	1,516	1,453	4,564	3,962
Expenses:
Provision for credit losses	45	118	110	366
Operating and administrative expenses	394	354	1,163	1,088
Voluntary protection contract expenses and insurance losses	96	98	303	265
Total expenses	535	570	1,576	1,719
Income before income taxes	981	883	2,988	2,243
Provision for income taxes	233	215	697	546
Net income	748	668	2,291	1,697
Total assets	136,135	134,491	136,135	134,491	$ 133,728
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, 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 expenses	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 for income taxes	0	0	0	0
Net income	0	0	0	0
Total assets	(121)	(127)	(121)	(127)
Finance Operations [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total financing revenues	2,991	2,974	9,022	8,821
Depreciation on operating leases	1,460	1,450	4,400	4,484
Interest expense	346	491	1,055	1,534
Net financing revenues	1,185	1,033	3,567	2,803
Voluntary protection contract revenues and insurance earned premiums	0	0	0	0
Investment and other income, net	12	21	40	76
Net financing revenues and other revenues	1,197	1,054	3,607	2,879
Expenses:
Provision for credit losses	45	118	110	366
Operating and administrative expenses	293	268	872	818
Voluntary protection contract expenses and insurance losses	0	0	0	0
Total expenses	338	386	982	1,184
Income before income taxes	859	668	2,625	1,695
Provision for income taxes	204	163	610	414
Net income	655	505	2,015	1,281
Total assets	129,511	128,442	129,511	128,442
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	255	241	758	714
Investment and other income, net	64	158	199	369
Net financing revenues and other revenues	319	399	957	1,083
Expenses:
Provision for credit losses	0	0	0	0
Operating and administrative expenses	101	86	291	270
Voluntary protection contract expenses and insurance losses	96	98	303	265
Total expenses	197	184	594	535
Income before income taxes	122	215	363	548
Provision for income taxes	29	52	87	132
Net income	93	163	276	416
Total assets	$ 6,745	$ 6,176	$ 6,745	$ 6,176