Related Party Transactions - Related Party Transactions Included in Consolidated Statements of Income (Details) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Total financing revenues:
Manufacturers’ subvention and other revenues	$ 368	$ 336
Interest expense:
Credit support fees incurred	23	23
Interest and other expenses	1	1
Insurance earned premiums and contract revenues:
Insurance premiums and contract revenues	216	193
Expenses:
Operating and administrative	313	279
Insurance losses and loss adjustment expenses	114	89
TMCC-affiliated companies [Member]
Insurance earned premiums and contract revenues:
Insurance premiums and contract revenues	44	34
Investment and other income, net:
Interest and other income	4	2
Expenses:
Operating and administrative	19	17
Insurance losses and loss adjustment expenses	$ (5)	$ 1