Related Party Transactions - Related Party Transactions Included in Consolidated Statements of Income (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Net financing revenues:
Manufacturers’ subvention and other revenues									$ 1,374	$ 1,315	$ 1,196
Credit support fees incurred									(92)	(91)	(88)
Interest and other expenses									(3)	(4)	(3)
Insurance earned premiums and contract revenues:
Insurance premiums and contract revenues	$ 210	$ 202	$ 199	$ 193	$ 186	$ 181	$ 178	$ 174	804	719	638
Investments and other income, net:
Gain on sale of commercial finance business					$ 0	$ 197	$ 0	$ 0	0	197	0
TMCC-affiliated companies [Member]
Insurance earned premiums and contract revenues:
Insurance premiums and contract revenues									149	132	129
Investments and other income, net:
Gain on sale of commercial finance business									0	197	0
Interest and other income									9	8	4
Expenses:
Shared services charges and other expenses									48	48	64
Employee benefits expense									$ 25	$ 33	$ 24