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Earnings Per Common Share, Potentially Dilutive Securities (Details)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Common Equivalent Shares [Member]
     
Potentially Dilutive Securities Excluded from Computation of Earnings Per Common Share      
Amount of potentially dilutive securities excluded from computation of earnings per common share 0 0 4
Stock Options [Member]
     
Potentially Dilutive Securities Excluded from Computation of Earnings Per Common Share      
Amount of potentially dilutive securities excluded from computation of earnings per common share 6 14 12