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		9 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Antidilutive Securities Excluded from Computation of Earnings (Loss) Per Share
Net income (loss)	$ (186)	$ (1)	$ 436	$ 401
Weighted Average Number of Shares Outstanding, Basic	308	303	309	302
Dilutive potential common shares related to stock award plans and from assumed exercise of stock options	0	0	3	3
Weighted Average Number of Shares Outstanding, Diluted	308	303	312	314
Basic	$ (0.60)	$ 0.00	$ 1.41	$ 1.33
Diluted	$ (0.60)	$ 0.00	$ 1.40	$ 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	1
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	8