Related Party Transactions - Related Party Transactions Included in Consolidated Statements of Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Net financing revenues:
Depreciation on operating leases	$ (1,349)	$ (1,583)	$ (3,034)	$ (3,208)
Insurance earned premiums and contract revenues:
Insurance premiums and contract revenues	238	232	473	461
Expenses:
Operating and administrative expenses	389	358	734	695
TMCC-affiliated companies [Member]
Net financing revenues:
Manufacturer's subvention and other revenues	502	508	1,001	1,020
Depreciation on operating leases	(26)	(13)	(49)	(23)
Interest expense:
Credit support fees, interest and other expenses	29	24	67	48
Insurance earned premiums and contract revenues:
Insurance premiums and contract revenues	43	45	87	90
Investment and other income, net:
Interest and other income	5	6	13	12
Expenses:
Operating and administrative expenses	$ 23	$ 21	$ 43	$ 42