Fair Value Measurements - Additional Information (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative asset counterparty credit valuation adjustment	$ 1	$ 1
Finance receivables from related party	94	89
Receivables from direct finance leases	308	274
U.S. government and agency obligations [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Reclassification within Level 3 debt instrument		2
Maximum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative liability non-performance credit valuation adjustment	$ 1	$ 1