| **Earnings (Loss) Per Share**                    | 6 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
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| **Earnings Per Share Reconciliation [Abstract]** |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
| Earnings (Loss) Per Share                        | (13) EARNINGS (LOSS) PER SHAREThe following table summarizes the computations of basic earnings per share (“Basic EPS”) and diluted earnings per share (“Diluted EPS”). Basic EPS is computed as net income divided by the weighted-average number of common shares outstanding for the period. Diluted EPS reflects the potential dilution that could occur from common shares issuable through stock-based compensation plans including stock options, restricted stock, restricted stock units, ESPP purchase rights, warrants, and other convertible securities using the treasury stock method. Three Months Ended September 30,    Six Months Ended September 30, (In millions, except per share amounts)2016 2015 2016 2015Net income (loss)$(38) $(140) $402 $302Shares used to compute earnings (loss) per share:       Weighted-average common stock outstanding — basic301 312 301 311Dilutive potential common shares related to stock award plans and from assumed exercise of stock options— — 3 7Dilutive potential common shares related to the Convertible Notes— — 2 9Dilutive potential common shares related to the Warrants— — 9 7Weighted-average common stock outstanding — diluted301 312 315 334Earnings (loss) per share:       Basic$(0.13) $(0.45) $1.34 $0.97Diluted$(0.13) $(0.45) $1.28 $0.90As a result of our net loss for the three months ended September 30, 2016, we have excluded all potentially dilutive common shares from the diluted loss per share calculation as their inclusion would have had an antidilutive effect. Had we reported net income for this period, an additional 3 million shares of common stock related to our outstanding equity-based instruments and an additional 10 million shares related to the Warrants would have been included in the number of shares used to calculate Diluted EPS for the three months ended September 30, 2016. As a result of our net loss for the three months ended September 30, 2015, we have excluded all potentially dilutive common shares from the diluted loss per share calculation as their inclusion would have had an antidilutive effect. Had we reported net income for this period, an additional 6 million shares of common stock related to our outstanding equity-based instruments, an additional 7 million shares of common stock related to the Notes, and an additional 8 million shares related to the Warrants would have been included in the number of shares used to calculate Diluted EPS for the three months ended September 30, 2015. For the six months ended September 30, 2016 and 2015, an immaterial amount of options to purchase, restricted stock units and restricted stock to be released were excluded from the treasury stock method computation of diluted shares as their inclusion would have had an antidilutive effect. |

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| - Definition
The entire disclosure for earnings per share.
+ References
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