|**Additional Shareholders' Equity Information (Tables)**                                                    | 12 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
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|**Additional Shareholders' Equity Information [Abstract]**                                                  |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|Schedule Of Activity In Shares Of Common And Treasury Stock                                                 | Activity in shares of our common stock and treasury stock was as follows:Year Ended December 31,20122011Common Stock Shares IssuedShares, Beginning of Period196,656,846195,440,048Exercise of Common Stock Options1,265,231837,096Restricted Stock Awards, Net of Forfeitures426,665379,702Shares, End of Period198,348,742196,656,846Treasury StockShares, Beginning of Period18,736,52018,650,064Shares Received From Employees in Payment of Withholding Taxes Due on Vesting of Shares of Restricted Stock141,124186,556Rabbi Trust Shares Distributed and/or Sold(102,268)(100,100)Shares, End of Period18,775,37618,736,520           
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|Common Stock Shares Issued                                                                                  |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|Shares, Beginning of Period                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|Exercise of Common Stock Options                                                                            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|Restricted Stock Awards, Net of Forfeitures                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|Shares, End of Period                                                                                       |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|Treasury Stock                                                                                              |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|Shares, Beginning of Period                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|Shares Received From Employees in Payment of Withholding Taxes Due on Vesting of Shares of Restricted Stock |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|Rabbi Trust Shares Distributed and/or Sold                                                                  |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|Shares, End of Period                                                                                       |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|Accumulated other comprehensive income (loss) in the shareholders' equity section of the balance sheet      | Accumulated other comprehensive loss in the shareholders’ equity section of the balance sheet included:Accumulated Other Comprehensive LossOil and GasCash FlowHedgesInterest RateCash FlowHedgesPension-Related andOtherTotal(millions)December 31, 2009$(12)$(2)$(61)$(75)Realized Amounts Reclassified Into Earnings121316Net Change in Other—(41)(4)(45)December 31, 2010—(42)(62)(104)Realized Amounts Reclassified Into Earnings—145Unrealized Change in Fair Value—15(16)(1)December 31, 2011—(26)(74)(100)Realized Amounts Reclassified Into Earnings—167Unrealized Change in Fair Value——(20)(20)December 31, 2012$—$(25)$(88)$(113)
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|(millions)                                                                                                  |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|December 31, 2009                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|Realized Amounts Reclassified Into Earnings                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|Net Change in Other                                                                                         |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|December 31, 2010                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|Realized Amounts Reclassified Into Earnings                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|Unrealized Change in Fair Value                                                                             |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|December 31, 2011                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|Realized Amounts Reclassified Into Earnings                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|Unrealized Change in Fair Value                                                                             |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              
|December 31, 2012                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              

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