Net Income (Loss) Per Share Net Income Per Share (Computation Of Basic Earnings And Diluted Earnings Per Share) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Earnings Per Share Reconciliation [Abstract]
Net income (loss)	$ 3	$ (273)	$ 338	$ (51)
Weighted Average Number of Shares Outstanding, Basic	313	308	312	306
Dilutive potential common shares related to stock award plans and from assumed exercise of stock options	6	0	8	0
Dilutive potential common shares related to Notes	3	0	2	0
Weighted Average Number of Shares Outstanding, Diluted	322	308	322	306
Basic	$ 0.01	$ (0.89)	$ 1.08	$ (0.17)
Diluted	$ 0.01	$ (0.89)	$ 1.05	$ (0.17)