XML 129 R114.htm IDEA: XBRL DOCUMENT v3.8.0.1
Stock Options and Other Equity-Based Incentive Instruments - Summary of Options Outstanding (Detail) - USD ($)
$ / shares in Units, $ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]    
Number of options 446,400 592,250
Weighted average exercise price $ 16.84 $ 17.12
Intrinsic value (in thousands) $ 9,382  
Weighted average remaining contractual term (yrs.) 3 years 10 months 25 days  
Currently Exercisable [Member]    
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]    
Number of options 422,100  
Weighted average exercise price $ 16.65  
Intrinsic value (in thousands) $ 8,953  
Weighted average remaining contractual term (yrs.) 3 years 9 months 18 days  
Currently Not Exercisable [Member]    
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]    
Number of options 24,300  
Weighted average exercise price $ 20.21  
Intrinsic value (in thousands) $ 429  
Weighted average remaining contractual term (yrs.) 5 years 8 months 12 days