Quarterly report pursuant to Section 13 or 15(d)

Share-Based Compensation - Summary of Stock Options Outstanding under Plans (Detail)

v3.3.0.814
Share-Based Compensation - Summary of Stock Options Outstanding under Plans (Detail) - USD ($)
$ / shares in Units, $ in Thousands
 3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2015
Jun. 30, 2015
Sep. 30, 2014
Sep. 30, 2015
Sep. 30, 2014
Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]            
Number of Shares, Options outstanding at beginning of period 553,440     603,872    
Number of Shares, Options granted       28,000    
Number of Shares, Options exercised (13,311)   (687) (39,766) (34,382)  
Number of Shares, Options forfeited (2,875)     (54,502)    
Number of Shares, Options expired (1,375)     (1,725)    
Number of Shares, Options outstanding at end of period 535,879 553,440   535,879   603,872
Number of Shares, Options exercisable at end of period 304,251     304,251    
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]            
Weighted-Average Exercise Price Per Share, Options outstanding at beginning of period (in usd per share) $ 24.42     $ 23.78    
Weighted-Average Exercise Price Per Share, Options granted (in usd per share)       23.47    
Weighted-Average Exercise Price Per Share, Options exercised (in usd per share) 12.54     13.36    
Weighted-Average Exercise Price Per Share, Options forfeited (in usd per share) 12.54     20.67    
Weighted-Average Exercise Price Per Share, Options expired (in usd per share) 144.00     144.00    
Weighted-Average Exercise Price Per Share, Options outstanding at end of period (in usd per share) 24.47 $ 24.42   24.47   $ 23.78
Weighted-Average Exercise Price Per Share, Options exercisable at end of period (in usd per share) $ 29.09     $ 29.09    
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term [Abstract]            
Weighted-Average Remaining Contractual Life, Options outstanding at beginning of period 7 years 7 months 7 days 7 years 9 months 18 days   7 years 7 months 6 days   8 years 3 months 18 days
Weighted-Average Remaining Contractual Life, Options granted       9 years 8 months 12 days    
Weighted-Average Remaining Contractual Life, Options exercised 6 years 6 months     7 years 1 month 6 days    
Weighted-Average Remaining Contractual Life, Options forfeited 7 years 2 months 12 days     8 years 6 months    
Weighted-Average Remaining Contractual Life, Options expired 7 months 6 days     7 months 6 days    
Weighted-Average Remaining Contractual Life, Options outstanding at end of period 7 years 7 months 7 days 7 years 9 months 18 days   7 years 7 months 6 days   8 years 3 months 18 days
Weighted-Average Remaining Contractual Life, Options exercisable at end of period 7 years     7 years    
Aggregate Intrinsic Value of In-the-Money Options, Options outstanding at beginning of period $ 1,764     $ 2,853    
Aggregate Intrinsic Value of In-the-Money Options, Options outstanding at end of period 4,099 $ 1,764   4,099   $ 2,853
Aggregate Intrinsic Value of In-the-Money Options, Options exercisable at end of period $ 2,511     $ 2,511    
Intrinsic value represents the excess of the closing stock price related to options outstanding (in usd per share) $ 25.20 $ 24.84   $ 25.20   $ 21.81