Related Party Transactions - Related Party Transactions Included in Consolidated Balance Sheet (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Dec. 31, 2015	Mar. 31, 2015
Investments in marketable securities
Investments in affiliates’ commercial paper	$ 0	$ 37
Finance receivables, net
Accounts receivable from affiliates	99	83
Direct finance lease receivables from affiliates	0	6
Notes receivable under home loan programs	9	11
Deferred retail origination costs paid to affiliates	1	1
Deferred retail subvention income from affiliates	(828)	(802)
Investments in operating leases, net
Leases to affiliates	35,336	31,128
Deferred lease origination costs paid to affiliates	1	1
Deferred lease subvention income from affiliates	(1,068)	(950)
Other assets
Notes receivable from affiliates	1,126	1,184
Other receivables from affiliates	41	6
Subvention support receivable from affiliates	139	126
Other liabilities
Unearned insurance premiums and contract revenues	1,957	1,825
Accounts payable to affiliates	81	136
Notes payable to affiliates	5	24
TMCC-affiliated companies [Member]
Investments in operating leases, net
Leases to affiliates	2	7
Other liabilities
Unearned insurance premiums and contract revenues	265	252
Shareholder’s equity:
Stock-based compensation	$ 2	$ 2