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Stock-Based Incentive Compensation Plans (Summary of activity for restricted stock units) (Details) - Restricted Stock Units [Member] - $ / shares
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Summary of activity for restricted stock units [Roll Forward]      
Outstanding as of beginning of year (in shares) 1,527,675    
Granted (in shares) 481,900 462,231 583,404
Vested (in shares) (613,391)    
Forfeited (in shares) (96,185)    
Outstanding as of end of year (in shares) 1,299,999 1,527,675  
Restricted stock units, additional disclosures [Abstract]      
Weighted-average grant date fair value, outstanding as of beginning of year (in dollars per share) $ 34.30    
Weighted-average grant date fair value, granted (in dollars per share) 58.08    
Weighted-average grant date fair value, vested (in dollars per share) 26.33    
Weighted-average grant date fair value, forfeited (in dollars per share) 43.32    
Weighted-average grant date fair value, outstanding as of end of year (in dollars per share) $ 46.21 $ 34.30