Allowance for Credit Losses (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012	Dec. 31, 2011
Allowance for Credit Losses on Finance Receivables and Investments in Operating Leases
Allowance for credit losses at	$ 549	$ 623	$ 619	$ 879
Provision for credit losses	88	56	107	(136)
Charge-offs, net of recoveries	(77)	(59)	(166)	(123)
Allowance for credit losses at	560	620	560	620
Recoveries from credit loss charge-offs	$ 18	$ 21	$ 59	$ 99