Related Party Transactions - Related Party Transactions Included in Consolidated Statements of Income (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Net financing revenues:
Depreciation on operating leases		$ (1,583)	$ (1,662)	$ (3,208)	$ (3,428)
Insurance earned premiums and contract revenues:
Insurance premiums and contract revenues		232	226	461	450
Expenses:
Operating and administrative expenses		358	348	695	672
TMCC-affiliated companies [Member]
Net financing revenues:
Manufacturer's subvention and other revenues		508	467	1,020	934
Depreciation on operating leases		(13)	(5)	(23)	(10)
Interest expense:
Credit support fees, interest and other expenses		24	24	48	49
Insurance earned premiums and contract revenues:
Insurance premiums and contract revenues		45	44	90	89
Investment and other income, net:
Interest and other income		6	2	12	4
Expenses:
Operating and administrative expenses		21	24	42	47
Insurance losses and loss adjustment expenses	[1]	$ 0	$ (1)	$ 0	$ (3)

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