Changes in Accumulated Other Comprehensive Income by Component (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	$ 2	$ 37	$ 69
Other comprehensive income (loss) before reclassifications	(6)	(46)	(41)
Amounts reclassified from accumulated other comprehensive income	(12)	11	9
Net current-period other comprehensive income (loss)	(18)	(35)	(32)
Ending balance	(16)	2	37
Unrealized Gains (Losses) on Available-for-Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(3)	(4)	(4)
Other comprehensive income (loss) before reclassifications	4	1	0
Amounts reclassified from accumulated other comprehensive income	0	0	0
Net current-period other comprehensive income (loss)	4	1	0
Ending balance	1	(3)	(4)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	21	(10)	0
Other comprehensive income (loss) before reclassifications	5	20	(19)
Amounts reclassified from accumulated other comprehensive income	(12)	11	9
Net current-period other comprehensive income (loss)	(7)	31	(10)
Ending balance	14	21	(10)
Foreign Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(16)	51	73
Other comprehensive income (loss) before reclassifications	(15)	(67)	(22)
Amounts reclassified from accumulated other comprehensive income	0	0	0
Net current-period other comprehensive income (loss)	(15)	(67)	(22)
Ending balance	$ (31)	$ (16)	$ 51