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Earnings Per Share (Tables) | 12 Months Ended
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Dec. 31, 2017
Text Block [Abstract] |
Schedule Of Basic And Diluted Earnings Per Share |
|  |  | Years Ended December 31, |
In millions except per share amounts |  | 2017 |  | 2016 |  |  | 2015 |
Basic earnings per share: |  |  |  |  |  |  |  |  |  |
| Net income (loss) |  | $ | (1,605) |  | $ | (338) |  | $ | 180 |
| Less: undistributed earnings allocated to participating securities |  |  | - |  |  | - |  |  | 6 |
| Net income (loss) available to common shareholders |  |  | (1,605) |  |  | (338) |  |  | 174 |
| Basic weighted average shares (1) |  |  | 118.9 |  |  | 133.0 |  |  | 163.9 |
| Net income (loss) per basic common share |  | $ | (13.50) |  | $ | (2.54) |  | $ | 1.06 |
Diluted earnings per share: |  |  |  |  |  |  |  |  |  |
| Net income (loss) |  | $ | (1,605) |  | $ | (338) |  | $ | 180 |
| Less: undistributed earnings allocated to participating securities |  |  | - |  |  | - |  |  | 6 |
| Net income (loss) available to common shareholders |  |  | (1,605) |  |  | (338) |  |  | 174 |
| Basic weighted average shares (1) |  |  | 118.9 |  |  | 133.0 |  |  | 163.9 |
| Effect of common stock equivalents: |  |  |  |  |  |  |  |  |  |
| Stock options |  |  | - |  |  | - |  |  | 1.0 |
| Diluted weighted average shares |  |  | 118.9 |  |  | 133.0 |  |  | 164.9 |
| Net income (loss) per diluted common share |  | $ | (13.50) |  | $ | (2.54) |  | $ | 1.06 |
| Potentially dilutive securities excluded from the diluted EPS because of antidilutive affect |  |  | 14.1 |  |  | 16.5 |  |  | 18.0 |
| (1) Includes 0.3 million, 0.9 million and 0.6 million of participating securities that met the service condition and were eligible to receive nonforfeitable dividends or dividend |
| equivalents for the years ended December 31, 2017, 2016 and 2015, respectively. |

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