Earnings Per Share (Computation Of Basic Earnings And Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net income (loss)	$ 837	$ 3,039	$ 1,019
Weighted-average common stock outstanding - basic	289	293	303
Dilutive potential common shares related to stock award plans and from assumed exercise of stock options	3	2	3
Weighted Average Number of Shares Outstanding, Diluted	292	295	306
Basic	$ 2.90	$ 10.37	$ 3.36
Diluted	$ 2.87	$ 10.30	$ 3.33