Related Party Transactions - Related Party Transactions Included in Consolidated Statement of Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2015	Dec. 31, 2014
Net financing revenues:
Manufacturers’ subvention support and other revenues	$ 335	$ 315	$ 982	$ 884
Origination costs paid to affiliates	0	0	(1)	0
Credit support fees incurred	(24)	(23)	(69)	(66)
Interest and other expenses paid to affiliates	(1)	(1)	(3)	(2)
Insurance earned premiums and contract revenues:
Affiliate insurance premiums and contract revenues	181	159	533	472
Investments and other income, net:
Interest earned on notes receivable from affiliates	1	1	4	3
Gain on sale of commercial finance business	197		197
Expenses:
Insurance losses and loss adjustment expenses	73	63	230	200
TMCC-affiliated companies [Member]
Insurance earned premiums and contract revenues:
Affiliate insurance premiums and contract revenues	33	32	98	97
Expenses:
Shared services charges and other expenses	7	16	34	48
Employee benefits expense	8	5	24	18
Insurance losses and loss adjustment expenses	$ 1	$ 0	$ 1	$ 0