Quarterly report pursuant to Section 13 or 15(d)

Share-Based Compensation - Additional Information (Detail)

v3.10.0.1
Share-Based Compensation - Additional Information (Detail) - USD ($)
3 Months Ended 9 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]        
Share-based compensation expense $ 850,000 $ 709,000 $ 2,664,000 $ 2,071,000
Related tax benefits on non-qualified stock options $ 238,000 $ 291,000 $ 746,000 $ 666,000
Number of shares, stock options exercised (shares) 0   25,750 22,125
Stock option awards [Member]        
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]        
Unrecognized share-based compensation expense $ 0   $ 0  
Restricted stock awards [Member]        
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]        
Unrecognized share-based compensation expense $ 5,069,000   $ 5,069,000