Related Party Transactions - Related Party Transactions Included in Consolidated Statements of Income (Details) - USD ($) $ in Millions		3 Months Ended
		Jun. 30, 2018	Jun. 30, 2017
Total financing revenues:
Manufacturers’ subvention and other revenues		$ 472	$ 368
Interest expense:
Credit support fees incurred		24	23
Interest and other expenses		1	1
Insurance earned premiums and contract revenues:
Insurance premiums and contract revenues		224	216
Expenses:
Operating and administrative		324	313
TMCC-affiliated companies [Member]
Insurance earned premiums and contract revenues:
Insurance premiums and contract revenues		45	44
Investment and other income, net:
Interest and other income		2	4
Expenses:
Operating and administrative		23	19
Insurance losses and loss adjustment expenses	[1]	$ (2)	$ (5)

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