Income Taxes (Provision For (Benefit From) Income Taxes) (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2014
Income Tax Disclosure [Abstract]
Federal, Current	$ 69	$ 10	$ (2)
State, Current	5	0	1
Foreign, Current	36	21	8
Total, Current	110	31	7
Federal, Deferred	(376)	17	(9)
State, Deferred	(14)	0	(2)
Foreign, Deferred	1	2	3
Total, Deferred	(389)	19	(8)
Total, Federal	(307)	27	(11)
Total, State	(9)	0	(1)
Total, Foreign	37	23	11
Total provision for (benefit from) income taxes	$ (279)	$ 50	$ (1)