Other Assets and Other Liabilities - Other Assets and Other Liabilities (Details) - USD ($) $ in Millions	Mar. 31, 2017	Mar. 31, 2016
Other assets:
Notes receivable from affiliates	$ 823	$ 1,177
Used vehicles held for sale	264	319
Income taxes receivable	0	31
Derivative assets	51	68
Other assets	906	622
Total other assets	2,044	2,217
Other liabilities:
Unearned insurance premiums and contract revenues	2,154	1,985
Accounts payable and accrued expenses	1,057	939
Deferred income	468	462
Income taxes payable	62	0
Derivative liabilities	46	7
Other liabilities	165	192
Total other liabilities	$ 3,952	$ 3,585