Fair Value Measurements - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Mar. 31, 2015
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative asset counterparty credit valuation adjustment			$ 2,000,000		$ 1,000,000
Fair value, amount transferred from level 1 to level 2	$ 37,000,000		37,000,000
Fair value, amount transferred from level 3 to level 2	4,000,000		4,000,000
Fair value, transfer between levels	0	$ 0		$ 0
Finance receivables from related party	112,000,000		112,000,000		94,000,000
Receivables from direct finance leases	25,000,000		25,000,000		308,000,000
Other Assets [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Finance receivables from related party	47,000,000		47,000,000
Receivables from direct finance leases	$ 304,000,000		$ 304,000,000
Maximum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative liability non-performance credit valuation adjustment					$ 1,000,000