Income Taxes (Provision For (Benefit From) Income Taxes) (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015
Income Tax Disclosure [Abstract]
Federal, Current	$ 86	$ 69	$ 10
State, Current	3	5	0
Foreign, Current	51	36	21
Total, Current	140	110	31
Federal, Deferred	96	(376)	17
State, Deferred	9	(14)	0
Foreign, Deferred	(2)	1	2
Total, Deferred	103	(389)	19
Total, Federal	182	(307)	27
Total, State	12	(9)	0
Total, Foreign	49	37	23
Total provision for (benefit from) income taxes	$ 243	$ (279)	$ 50