Allowance for Credit Losses - Allowance for Credit Losses on Finance Receivables and Investments in Operating Leases (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2015	Dec. 31, 2014
Allowance for Credit Losses on Finance Receivables and Investments in Operating Leases
Allowance for credit losses at beginning of period		$ 473	$ 445	$ 485	$ 454
Provision for credit losses		128	103	278	220
Transferred to held-for-sale	[1]	0	0	(7)	0
Charge-offs, net of recoveries		(115)	(98)	(270)	(224)
Allowance for credit losses at end of period		$ 486	$ 450	$ 486	$ 450

[1] Amount relates to the commercial finance business which was sold on October 1, 2015.