Related Party Transactions - Related Party Transactions Included in Consolidated Statement of Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2016	Dec. 31, 2015
Net financing revenues:
Manufacturers’ subvention support and other revenues	$ 349	$ 335	$ 1,020	$ 982
Origination costs paid to affiliates	0	0	(1)	(1)
Credit support fees incurred	(22)	(24)	(68)	(69)
Interest and other expenses paid to affiliates	0	(1)	(1)	(3)
Insurance earned premiums and contract revenues:
Affiliate insurance premiums and contract revenues	202	181	594	533
Investments and other income, net:
Gain on sale of commercial finance business	0	197	0	197
Interest earned on notes receivable from affiliates	1	1	5	4
Other income from affiliates	0	0	1	0
Expenses:
Insurance losses and loss adjustment expenses	92	73	272	230
TMCC-affiliated companies [Member]
Insurance earned premiums and contract revenues:
Affiliate insurance premiums and contract revenues	36	33	105	98
Investments and other income, net:
Gain on sale of commercial finance business	0	197	0	197
Expenses:
Shared services charges and other expenses	12	7	34	34
Employee benefits expense	6	8	18	24
Insurance losses and loss adjustment expenses	$ 0	$ 1	$ 1	$ 1