Related Party Transactions - Related Party Transactions Included in Consolidated Statements of Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Net financing revenues:
Depreciation on operating leases	$ (1,450)	$ (1,712)	$ (4,484)	$ (4,920)
Insurance earned premiums and contract revenues:
Insurance premiums and contract revenues	241	231	714	692
Expenses:
Operating and administrative expenses	354	406	1,088	1,101
TMCC-affiliated companies [Member]
Net financing revenues:
Manufacturer's subvention and other revenues	503	526	1,504	1,546
Depreciation on operating leases	(33)	(16)	(82)	(39)
Interest expense:
Credit support fees, interest and other expenses	26	24	93	72
Insurance earned premiums and contract revenues:
Insurance premiums and contract revenues	43	46	130	136
Investment and other income, net:
Interest and other income	3	7	16	19
Expenses:
Operating and administrative expenses	$ 20	$ 29	$ 63	$ 65