Segment Information - Schedule of Segment Reporting Information by Segment (Details) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Mar. 31, 2024
Segment Reporting Information [Line Items]
Total financing revenues	$ 3,209	$ 2,904
Depreciation on operating leases	1,034	1,155
Interest expense	1,443	899
Net financing revenues	732	850
Voluntary protection contract revenues and insurance earned premiums	295	271
Investment and other income, net	223	162
Net financing revenues and other revenues	1,250	1,283
Expenses:
Provision for credit losses	189	165
Operating and administrative	440	448
Voluntary protection contract expenses and insurance losses	159	146
Total expenses	788	759
Income before income taxes	462	524
Provision for income taxes	105	132
Net income	357	392
Total assets	148,638	138,636	$ 149,381
Intercompany Eliminations [Member]
Segment Reporting Information [Line Items]
Total financing revenues	0	0
Depreciation on operating leases	0	0
Interest expense	0	0
Net financing revenues	0	0
Voluntary protection contract revenues and insurance earned premiums	0	0
Investment and other income, net	0	0
Net financing revenues and other revenues	0	0
Expenses:
Provision for credit losses	0	0
Operating and administrative	0	0
Voluntary protection contract expenses and insurance losses	0	0
Total expenses	0	0
Income before income taxes	0	0
Provision for income taxes	0	0
Net income	0	0
Total assets	(142)	(67)
Finance Operations [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total financing revenues	3,209	2,904
Depreciation on operating leases	1,034	1,155
Interest expense	1,443	899
Net financing revenues	732	850
Voluntary protection contract revenues and insurance earned premiums	0	0
Investment and other income, net	166	114
Net financing revenues and other revenues	898	964
Expenses:
Provision for credit losses	189	165
Operating and administrative	327	334
Voluntary protection contract expenses and insurance losses	0	0
Total expenses	516	499
Income before income taxes	382	465
Provision for income taxes	87	119
Net income	295	346
Total assets	141,145	131,974
Voluntary Protection Operations [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total financing revenues	0	0
Depreciation on operating leases	0	0
Interest expense	0	0
Net financing revenues	0	0
Voluntary protection contract revenues and insurance earned premiums	295	271
Investment and other income, net	57	48
Net financing revenues and other revenues	352	319
Expenses:
Provision for credit losses	0	0
Operating and administrative	113	114
Voluntary protection contract expenses and insurance losses	159	146
Total expenses	272	260
Income before income taxes	80	59
Provision for income taxes	18	13
Net income	62	46
Total assets	$ 7,635	$ 6,729