Stock Incentive Plans (Details 2) (Stock option awards, USD $)
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Stock option awards
     
Shares      
Outstanding at beginning of year (in shares) 696,379 857,468 1,017,922
Forfeited (in shares) (186,249) (161,089) (160,454)
Outstanding at end of period (in shares) 510,130 696,379 857,468
Exercisable at end of period (in shares) 510,130 696,379 857,468
Weighted-Average Exercise Price      
Outstanding at beginning of year (in dollars per share) $ 17.22 $ 17.01 $ 16.23
Forfeited (in dollars per share) $ 19.67 $ 16.10 $ 12.07
Outstanding at end of period (in dollars per share) $ 16.33 $ 17.22 $ 17.01
Exercisable at end of period (in dollars per share) $ 16.33 $ 17.22 $ 17.01