Related Party Transactions - Related Party Transactions Included in Consolidated Statements of Income (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Net financing revenues:
Depreciation on operating leases		$ (1,712)	$ (1,717)	$ (4,920)	$ (5,145)
Insurance earned premiums and contract revenues:
Insurance premiums and contract revenues		231	226	692	676
Expenses:
Operating and administrative expenses		406	347	1,101	1,019
TMCC-affiliated companies [Member]
Net financing revenues:
Manufacturer's subvention and other revenues		526	502	1,546	1,436
Depreciation on operating leases		(16)	(6)	(39)	(16)
Interest expense:
Credit support fees, interest and other expenses		24	24	72	73
Insurance earned premiums and contract revenues:
Insurance premiums and contract revenues		46	46	136	135
Investment and other income, net:
Interest and other income		7	4	19	8
Expenses:
Operating and administrative expenses		29	24	65	71
Insurance losses and loss adjustment expenses	[1]	$ 0	$ 0	$ 0	$ (3)

[1] Amount includes the transfer of insurance losses and loss adjustment expenses under a reinsurance contract.