|**Net Income Per Common Share (Tables)**              | 12 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
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|**Earnings Per Share [Abstract]**                     |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Calculations For Basic And Diluted Earnings Per Share | The table shows calculations for basic and diluted earnings per share:(In millions except per share data)Years ended December 31,201320122011Numerator:Net income—basic and diluted$517$421$164Denominator:Basic weighted-average common shares outstanding163.5162.5162.7Effect of stock-based awards:Stock options1.20.50.1Nonvested shares0.70.70.5Adjusted diluted weighted-average shares165.4163.7163.3Earnings per share:Basic$3.16$2.59$1.01Diluted3.122.571.01Number of anti-dilutive stock-based awards0.45.97.8
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|(In millions except per share data)                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|                                                      | 2013                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      
|Numerator:                                            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Net income—basic and diluted                          |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
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|Denominator:                                          |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Basic weighted-average common shares outstanding      |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Effect of stock-based awards:                         |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Stock options                                         |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Nonvested shares                                      |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Adjusted diluted weighted-average shares              |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
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|Earnings per share:                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Basic                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Diluted                                               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
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|Number of anti-dilutive stock-based awards            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
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