Related Party Transactions - Related Party Transactions Included in Consolidated Statements of Income (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2020
Net financing revenues:
Depreciation on operating leases	$ (5,846)	$ (5,932)	$ (6,820)
Voluntary protection contract revenues and insurance earned premiums:
Voluntary protection contract revenues and insurance earned premiums	1,015	956	933
Expenses:
Operating and administrative	1,697	1,487	1,561
TMCC-affiliated companies [Member]
Net financing revenues:
Manufacturer's subvention and other revenues	1,746	1,997	2,065
Depreciation on operating leases	(75)	(113)	(59)
Interest expense:
Credit support fees, interest and other expenses	99	117	96
Voluntary protection contract revenues and insurance earned premiums:
Voluntary protection contract revenues and insurance earned premiums	168	173	181
Investment and other income, net:
Interest and other income	3	18	26
Expenses:
Operating and administrative	$ 82	$ 91	$ 102