|**Basic and Diluted Earnings Per Share (Tables)**                                                                                          | 3 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 EndedMarch 31,20132012(millions, except per share amounts)Income from Continuing Operations$232$249Weighted Average Number of Shares Outstanding, Basic179177Incremental Shares From Assumed Conversion of Dilutive Stock Options, Restricted Stock and Shares of Common Stock in Rabbi Trust23Weighted Average Number of Shares Outstanding, Diluted181180Earnings from Continuing Operations Per Share, Basic$1.29$1.40Earnings from Continuing Operations Per Share, Diluted1.281.39Number of antidilutive stock options, shares of restricted stock and shares of common stock in rabbi trust excluded from calculation above32
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|                                                                                                                                           | Three Months EndedMarch 31,                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
|                                                                                                                                           | 2013                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
|(millions, except per share amounts)                                                                                                       |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Income from Continuing Operations                                                                                                          | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      
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|Weighted Average Number of Shares Outstanding, Basic                                                                                       | 179                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Incremental Shares From Assumed Conversion of Dilutive Stock Options, Restricted Stock and Shares of Common Stock in Rabbi Trust           | 2                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      
|Weighted Average Number of Shares Outstanding, Diluted                                                                                     | 181                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Earnings from Continuing Operations Per Share, Basic                                                                                       | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      
|Earnings from Continuing Operations Per Share, Diluted                                                                                     | 1.28                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
|Number of antidilutive stock options, shares of restricted stock and shares of common stock in rabbi trust excluded from calculation above | 3                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      
|Retrospective Effect of Stock Split                                                                                                        | Pro forma earnings per share and common shares outstanding, giving retrospective effect to the stock split, is as follows:Three Months Ended March 31,20132012As ReportedPro FormaAs ReportedPro Forma(millions, except per share amounts)Earnings Per Share, BasicIncome from Continuing Operations$1.29$0.65$1.40$0.70Discontinued Operations, Net of Tax0.170.080.080.04Net Income$1.46$0.73$1.48$0.74Earnings Per Share, DilutedIncome from Continuing Operations$1.28$0.64$1.39$0.69Discontinued Operations, Net of Tax0.170.080.080.04Net Income$1.45$0.72$1.47$0.73Weighted Avg Number of Shares OutstandingBasic179358177355Diluted181362180359                                                                                
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|                                                                                                                                           | Three Months Ended March 31,                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           
|                                                                                                                                           | 2013                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
|                                                                                                                                           | As Reported                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
|(millions, except per share amounts)                                                                                                       |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Earnings Per Share, Basic                                                                                                                  |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Income from Continuing Operations                                                                                                          | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      
|Discontinued Operations, Net of Tax                                                                                                        | 0.17                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
|Net Income                                                                                                                                 | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      
|Earnings Per Share, Diluted                                                                                                                |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Income from Continuing Operations                                                                                                          | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      
|Discontinued Operations, Net of Tax                                                                                                        | 0.17                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   
|Net Income                                                                                                                                 | $                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      
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|Weighted Avg Number of Shares Outstanding                                                                                                  |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        
|Basic                                                                                                                                      | 179                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Diluted                                                                                                                                    | 181                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    

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