Related Party Transactions - Related Party Transactions Included in Consolidated Statements of Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2023	Dec. 31, 2022
Voluntary protection contract revenues and insurance earned premiums:
Voluntary protection contract revenues and insurance earned premiums	$ 282	$ 263	$ 831	$ 785
Expenses:
Operating and administrative	517	463	1,414	1,313
TMCC-affiliated companies [Member]
Net financing revenues:
Manufacturer's subvention and other revenues	237	300	760	955
Depreciation on operating leases	5	23	(82)	79
Interest expense:
Credit support fees, interest and other expenses	29	25	77	72
Voluntary protection contract revenues and insurance earned premiums:
Voluntary protection contract revenues and insurance earned premiums	39	39	116	118
Investment and other income, net:
Interest and other income	26	21	45	18
Expenses:
Operating and administrative	$ 26	$ 42	$ 72	$ 79