| **Net Income Per Common Share (Tables)**              | 9 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) Three months ended September 30, Nine months ended September 30, 2015 2014 2015 2014Numerator:        Net income—basic and diluted $174 $183 $478 $358Denominator:        Basic weighted-average common shares  outstanding 164.0 163.5 164.1 163.5Effect of share-based awards:        Stock options 1.0 0.9 0.9 0.9Nonvested shares 0.5 0.6 0.5 0.6Diluted weighted-average shares  165.5 165.0 165.5 165.0Earnings per share:        Basic $1.06 $1.12 $2.91 $2.19Diluted 1.05 1.11 2.89 2.17Number of anti-dilutive share-based awards: 0.3 0.7 0.7 0.7          |

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| - References
No definition available.
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| - Definition
Tabular disclosure of an entity's basic and diluted earnings per share calculations, including a reconciliation of numerators and denominators of the basic and diluted per-share computations for income from continuing operations.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257
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