Quarterly report pursuant to Section 13 or 15(d)

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

v3.19.3
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, 2019
Jun. 30, 2019
Sep. 30, 2018
Sep. 30, 2019
Sep. 30, 2018
Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]            
Number of Shares, Options outstanding at beginning of period (shares) 336,438     338,338    
Number of shares, Stock options exercised (shares) (180,000)   0 (181,900) (25,750)  
Number of Shares, Options outstanding at end of period (shares) 156,438 336,438   156,438   338,338
Number of Shares, Options exercisable at end of period (shares) 156,438     156,438    
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) $ 17.55     $ 17.52    
Weighted-Average Exercise Price Per Share, Options exercised (in usd per share) 16.43     16.38    
Weighted-Average Exercise Price Per Share, Options outstanding at end of period (in usd per share) 18.84 $ 17.55   18.84   $ 17.52
Weighted-Average Exercise Price Per Share, Options exercisable at end of period (in usd per share) $ 18.84     $ 18.84    
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 4 years 4 months 24 days 4 years 4 months 24 days   4 years 4 months 24 days   4 years 7 months 6 days
Weighted-Average Remaining Contractual Life, Options exercised 4 years 2 months 12 days     4 years 7 months 6 days    
Weighted-Average Remaining Contractual Life, Options exercisable at end of period 4 years 4 months 24 days          
Aggregate Intrinsic Value of In-the-Money Options, Options outstanding at beginning of period $ 1,162     $ 1,356    
Aggregate Intrinsic Value of In-the-Money Options, Options exercised 754     604    
Aggregate Intrinsic Value of In-the-Money Options, Options outstanding at end of period 407 $ 1,162   407   $ 1,356
Aggregate Intrinsic Value of In-the-Money Options, Options exercisable at end of period $ 407     $ 407    
Intrinsic value represents the excess of the closing stock price related to options outstanding (in usd per share) $ 18.78 $ 22.27   $ 18.78   $ 19.70