Segment Information - Schedule of Segment Reporting Information by Segment (Details) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Mar. 31, 2025
Segment Reporting Information [Line Items]
Total financing revenues	$ 3,363	$ 3,209
Depreciation on operating leases	1,023	1,034
Interest expense	1,305	1,443
Net financing revenues	1,035	732
Voluntary protection contract revenues and insurance earned premiums	320	295
Investment and other income, net	356	223
Net financing revenues and other revenues	1,711	1,250
Expenses:
Provision for credit losses	45	189
Operating and administrative	427	440
Voluntary protection contract expenses and insurance losses	174	159
Total expenses	646	788
Income before income taxes	1,065	462
Provision for income taxes	253	105
Net income	812	357
Total assets	152,215	148,638	$ 155,294
Intercompany Eliminations [Member]
Segment Reporting Information [Line Items]
Total financing revenues	0	0
Depreciation on operating leases	0	0
Interest expense	(6)	0
Net financing revenues	6	0
Voluntary protection contract revenues and insurance earned premiums	0	0
Investment and other income, net	(6)	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	(1,074)	(142)
Finance Operations [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total financing revenues	3,363	3,209
Depreciation on operating leases	1,023	1,034
Interest expense	1,311	1,443
Net financing revenues	1,029	732
Voluntary protection contract revenues and insurance earned premiums	0	0
Investment and other income, net	172	166
Net financing revenues and other revenues	1,201	898
Expenses:
Provision for credit losses	45	189
Operating and administrative	313	327
Voluntary protection contract expenses and insurance losses	0	0
Total expenses	358	516
Income before income taxes	843	382
Provision for income taxes	202	87
Net income	641	295
Total assets	144,743	141,145
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	320	295
Investment and other income, net	190	57
Net financing revenues and other revenues	510	352
Expenses:
Provision for credit losses	0	0
Operating and administrative	114	113
Voluntary protection contract expenses and insurance losses	174	159
Total expenses	288	272
Income before income taxes	222	80
Provision for income taxes	51	18
Net income	171	62
Total assets	$ 8,546	$ 7,635