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, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Antidilutive Securities Excluded from Computation of Earnings (Loss) Per Share
Net income (loss)	$ (22)	$ (38)	$ 622	$ 402
Weighted Average Number of Shares Outstanding, Basic	309	301	309	301
Dilutive potential common shares related to stock award plans and from assumed exercise of stock options	0	0	4	3
Weighted Average Number of Shares Outstanding, Diluted	309	301	313	315
Basic	$ (0.07)	$ (0.13)	$ 2.01	$ 1.34
Diluted	$ (0.07)	$ (0.13)	$ 1.99	$ 1.28
Convertible Debt
Antidilutive Securities Excluded from Computation of Earnings (Loss) Per Share
Incremental Common Shares Attributable to Dilutive Effect of Call Options and Warrants	0	0	0	2
Warrants
Antidilutive Securities Excluded from Computation of Earnings (Loss) Per Share
Incremental Common Shares Attributable to Dilutive Effect of Call Options and Warrants	0	0	0	9