Earnings (Loss) Per Share Earnings (Loss) Per Share (Computation Of Basic Earnings And Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Antidilutive Securities Excluded from Computation of Earnings (Loss) Per Share
Net income (loss)	$ 255	$ (22)	$ 548	$ 622
Weighted Average Number of Shares Outstanding, Basic	305	309	305	309
Dilutive potential common shares related to stock award plans and from assumed exercise of stock options	2	0	4	4
Weighted Average Number of Shares Outstanding, Diluted	307	309	309	313
Earnings Per Share, Basic	$ 0.84	$ (0.07)	$ 1.80	$ 2.01
Earnings Per Share, Diluted	$ 0.83	$ (0.07)	$ 1.77	$ 1.99