Allowance for Credit Losses - Allowance for Credit Losses on Finance Receivables and Investments in Operating Leases (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Allowance for Credit Losses on Finance Receivables and Investments in Operating Leases
Allowance for credit losses at beginning of period	$ 467	$ 447	$ 485	$ 454
Provision for credit losses	105	79	150	117
Transferred to held-for-sale	(7)	0	(7)	0
Charge-offs, net of recoveries	(92)	(81)	(155)	(126)
Allowance for credit losses at end of period	$ 473	$ 445	$ 473	$ 445