Income Taxes (Provision For (Benefit From) Income Taxes) (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Federal, Current	$ 258	$ 29	$ 138
State, Current	39	5	4
Foreign, Current	48	42	61
Total, Current	345	76	203
Federal, Deferred	(14)	(18)	197
State, Deferred	(2)	0	9
Foreign, Deferred	(1,860)	2	(3)
Total, Deferred	(1,876)	(16)	203
Total, Federal	244	11	335
Total, State	37	5	13
Total, Foreign	(1,812)	44	58
Total provision for (benefit from) income taxes	$ (1,531)	$ 60	$ 406