v3.7.0.1
Earnings Per Common Share (Summary Of Calculation Of Basic And Diluted Earnings Per Share) (Details) - USD ($)
$ / shares in Units, shares in Millions, $ in Millions
3 Months Ended
Mar. 31, 2017
Mar. 31, 2016
Earnings Per Common Share [Abstract]    
Net income used for basic and diluted calculation $ 170 $ 92
Shares used in computing earnings per common share—basic 224 225
Stock awards 2 2
Shares used in computing earnings per common share-diluted 226 227
Earnings Per Share, Basic $ 0.76 $ 0.41
Earnings Per Share, Diluted $ 0.75 $ 0.41