Other Assets and Other Liabilities - Other Assets and Other Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2016	Mar. 31, 2016
Other assets:
Notes receivable from affiliates	$ 204	$ 1,177
Used vehicles held for sale	359	319
Income taxes receivable	0	31
Derivative assets	45	68
Other assets	895	622
Total other assets	1,503	2,217
Other liabilities:
Unearned insurance premiums and contract revenues	2,083	1,985
Accounts payable and accrued expenses	941	939
Deferred income	476	462
Income taxes payable	14	0
Derivative liabilities	5	7
Other liabilities	167	192
Total other liabilities	$ 3,686	$ 3,585