XML 86 R72.htm IDEA: XBRL DOCUMENT v3.8.0.1
Accounting for Stock-based Compensation - Outstanding Stock Option Activity (Details) - USD ($)
$ / shares in Units, $ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Number of Shares, Outstanding Ending Balance 411,498    
Number of Shares, Exercisable at December 31, 2017 411,498    
Weighted Average Exercise Price, Outstanding Ending Balance $ 30.71    
Weighted Average Exercise Price, Exercisable at December 31, 2017 $ 30.71    
Employee Stock Option      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Number of Shares, Outstanding Beginning Balance 587,407 723,005 766,924
Number of Shares, Exercised (175,909) (128,301) (43,919)
Number of Shares, Granted 0 0 0
Number of Shares, Forfeited/Expired   (7,297)  
Number of Shares, Outstanding Ending Balance 411,498 587,407 723,005
Number of Shares, Vested plus expected to vest at December 31, 2017 411,498    
Number of Shares, Exercisable at December 31, 2017 411,498    
Weighted Average Exercise Price, Outstanding Beginning Balance $ 29.56 $ 28.62 $ 28.20
Weighted Average Exercise Price, Exercised 26.84 23.65 21.23
Weighted Average Exercise Price, Forfeited/Expired   40.68  
Weighted Average Exercise Price, Outstanding Ending Balance 30.71 $ 29.56 $ 28.62
Weighted Average Exercise Price, Vested plus expected to vest at December 31, 2017 30.71    
Weighted Average Exercise Price, Exercisable at December 31, 2017 $ 30.71    
Aggregate Intrinsic Value, Outstanding at December 31,2017 $ 8,965    
Aggregate Intrinsic Value, Vested plus expected to vest at December 31, 2017 8,965    
Aggregate Intrinsic Value, Exercisable at December 31, 2017 $ 8,965