Derivative Instruments - Income Statement Effect of Derivative Instruments (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2015	Dec. 31, 2014
Derivative Instruments Gain Loss [Line Items]
Gain/(Loss) on derivative instruments	$ (65)	$ (61)	$ (62)	$ (193)
Interest rate swaps
Derivative Instruments Gain Loss [Line Items]
Gain/(Loss) on derivative instruments	7	7	(21)	20
Cross currency swaps
Derivative Instruments Gain Loss [Line Items]
Gain/(Loss) on derivative instruments	$ (72)	$ (68)	$ (41)	$ (213)