Changes in Accumulated Other Comprehensive Income by Component (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2015	Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	$ (44)	$ 53	$ 2	$ 37
Other comprehensive income (loss) before reclassifications	(10)	(30)	(48)	(21)
Amounts reclassified from accumulated other comprehensive income (loss)	(3)	0	(11)	7
Net current-period other comprehensive income (loss)	(13)	(30)	(59)	(14)
Ending balance	(57)	23	(57)	23
Unrealized Gains (Losses) on Available-for-Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(3)	(4)	(3)	(4)
Other comprehensive income (loss) before reclassifications	(4)	(1)	(3)	(1)
Amounts reclassified from accumulated other comprehensive income (loss)	1	(1)	0	(1)
Net current-period other comprehensive income (loss)	(3)	(2)	(3)	(2)
Ending balance	(6)	(6)	(6)	(6)
Unrealized Gains (Losses) on Derivative Instruments [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	6	7	21	(10)
Other comprehensive income (loss) before reclassifications	10	1	2	11
Amounts reclassified from accumulated other comprehensive income (loss)	(4)	1	(11)	8
Net current-period other comprehensive income (loss)	6	2	(9)	19
Ending balance	12	9	12	9
Foreign Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance	(47)	50	(16)	51
Other comprehensive income (loss) before reclassifications	(16)	(30)	(47)	(31)
Amounts reclassified from accumulated other comprehensive income (loss)	0	0	0	0
Net current-period other comprehensive income (loss)	(16)	(30)	(47)	(31)
Ending balance	$ (63)	$ 20	$ (63)	$ 20