Annual report pursuant to Section 13 and 15(d)

Share-based Compensation - Summary of Stock Option Transactions under Plans (Detail)

v3.19.3.a.u2
Share-based Compensation - Summary of Stock Option Transactions under Plans (Detail) - 2007 and 2013 Plan - $ / shares
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]      
Number of Shares, options outstanding at beginning of period (shares) 338,338 364,088 387,901
Number of Shares, Options granted (shares) 0    
Number of Shares, Options exercised (shares) (181,900) (25,750) (23,813)
Number of Shares, Options forfeited (shares)   0 0
Number of Shares, Options expired (shares)   0 0
Number of Shares, Options outstanding at end of period (shares) 156,438 338,338 364,088
Number of Shares, Options exercisable at end of period (shares) 156,438 338,338 354,753
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) $ 17.52 $ 17.86 $ 17.49
Weighted-Average Exercise Price Per Share, Options exercised (in USD per share) 16.38 22.06 12.21
Weighted-Average Exercise Price Per Share, Options forfeited (in USD per share)   0 0
Weighted-Average Exercise Price Per Share, Options expired (in USD per share)   0 0
Weighted-Average Exercise Price Per Share, Options outstanding at end of period (in USD per share) 18.84 17.52 17.86
Weighted-Average Exercise Price Per Share, Options exercisable at end of period (in USD per share) $ 18.84 $ 17.52 $ 17.71