|**Basic and Diluted Earnings Per Share (Tables)**                                                                                          | 6 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
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|**Earnings Per Share [Abstract]**                                                                                                          |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]                                                                       | The following table summarizes the calculation of basic and diluted earnings per share:Three Months EndedJune 30,Six Months EndedJune 30,2013201220132012(millions, except per share amounts)Income from Continuing Operations$358$275$590$524Earnings Adjustment from Assumed Conversion of Dilutive Shares of Common Stock in Rabbi Trust(1)—(7)—(5)Income from Continuing Operations Used for Diluted Earnings Per Share Calculation$358$268$590$519Weighted Average Number of Shares Outstanding, Basic359356358355Incremental Shares From Assumed Conversion of Dilutive Stock Options, Restricted Stock and Shares of Common Stock in Rabbi Trust4545Weighted Average Number of Shares Outstanding, Diluted363361362360Earnings from Continuing Operations Per Share, Basic$1.00$0.77$1.64$1.47Earnings from Continuing Operations Per Share, Diluted0.990.741.631.44Number of antidilutive stock options, shares of restricted stock and shares of common stock in rabbi trust excluded from calculation above5555(1)Consistent with GAAP, when dilutive, deferred compensation gains or losses, net of tax, are excluded from net income while our common shares held in the rabbi trust are included in the diluted share count. For this reason, the diluted earnings per share calculations for the three and six months ended June 30, 2012 exclude deferred compensation gains.
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|                                                                                                                                           | Three Months EndedJune 30,                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
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|(millions, except per share amounts)                                                                                                       |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             
|Income from Continuing Operations                                                                                                          | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Earnings Adjustment from Assumed Conversion of Dilutive Shares of Common Stock in Rabbi Trust(1)                                           | —                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Income from Continuing Operations Used for Diluted Earnings Per Share Calculation                                                          | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
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|Weighted Average Number of Shares Outstanding, Basic                                                                                       | 359                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         
|Incremental Shares From Assumed Conversion of Dilutive Stock Options, Restricted Stock and Shares of Common Stock in Rabbi Trust           | 4                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Weighted Average Number of Shares Outstanding, Diluted                                                                                     | 363                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         
|Earnings from Continuing Operations Per Share, Basic                                                                                       | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|Earnings from Continuing Operations Per Share, Diluted                                                                                     | 0.99                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Number of antidilutive stock options, shares of restricted stock and shares of common stock in rabbi trust excluded from calculation above | 5                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
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|(1)                                                                                                                                        | Consistent with GAAP, when dilutive, deferred compensation gains or losses, net of tax, are excluded from net income while our common shares held in the rabbi trust are included in the diluted share count. For this reason, the diluted earnings per share calculations for the three and six months ended June 30, 2012 exclude deferred compensation gains.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            

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