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, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Antidilutive Securities Excluded from Computation of Earnings (Loss) Per Share
Net income (loss)	$ (38)	$ (140)	$ 402	$ 302
Weighted Average Number of Shares Outstanding, Basic	301	312	301	311
Dilutive potential common shares related to stock award plans and from assumed exercise of stock options	0	0	3	7
Weighted Average Number of Shares Outstanding, Diluted	301	312	315	334
Basic	$ (0.13)	$ (0.45)	$ 1.34	$ 0.97
Diluted	$ (0.13)	$ (0.45)	$ 1.28	$ 0.90
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	2	9
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	9	7