Income Taxes (Provision For (Benefit From) Income Taxes) (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019
Income Tax Disclosure [Abstract]
Federal, Current	$ 251	$ 258	$ 29
State, Current	24	39	5
Foreign, Current	47	48	42
Total, Current	322	345	76
Federal, Deferred	(26)	(14)	(18)
State, Deferred	(2)	(2)	0
Foreign, Deferred	(114)	(1,860)	2
Total, Deferred	(142)	(1,876)	(16)
Total, Federal	225	244	11
Total, State	22	37	5
Total, Foreign	(67)	(1,812)	44
Total provision for (benefit from) income taxes	$ 180	$ (1,531)	$ 60