Related Party Transactions - Related Party Transactions Included in Consolidated Statements of Income (Details) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Net financing revenues:
Depreciation on operating leases	$ (1,441)	$ (1,685)
Voluntary protection contract revenues and insurance earned premiums:
Voluntary protection contract revenues and insurance earned premiums	249	235
Expenses:
Operating and administrative expenses	384	345
TMCC-affiliated companies [Member]
Net financing revenues:
Manufacturer's subvention and other revenues	479	499
Depreciation on operating leases	(28)	(23)
Interest expense:
Credit support fees, interest and other expenses	24	38
Voluntary protection contract revenues and insurance earned premiums:
Voluntary protection contract revenues and insurance earned premiums	42	44
Investment and other income, net:
Interest and other income	3	8
Expenses:
Operating and administrative expenses	$ 21	$ 20