Annual report pursuant to Section 13 and 15(d)

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

v3.10.0.1
Share-based Compensation - Summary of Stock Option Transactions under Plans (Detail) - 2007 and 2013 Plan - $ / shares
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]      
Number of Shares, options outstanding at beginning of period (shares) 364,088 387,901 510,148
Number of Shares, Options exercised (shares) (25,750) (23,813) (94,997)
Number of Shares, Options forfeited (shares) 0 0 (125)
Number of Shares, Options expired (shares) 0 0 (27,125)
Number of Shares, Options outstanding at end of period (shares) 338,338 364,088 387,901
Number of Shares, Options exercisable at end of period (shares) 338,338 354,753 341,561
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) $ 17.86 $ 17.49 $ 24.38
Weighted-Average Exercise Price Per Share, Options exercised (in usd per share) 22.06 12.21 15.29
Weighted-Average Exercise Price Per Share, Options forfeited (in usd per share) 0.00 0.00 144.00
Weighted-Average Exercise Price Per Share, Options expired (in usd per share) 0.00 0.00 154.09
Weighted-Average Exercise Price Per Share, Options outstanding at end of period (in usd per share) 17.52 17.86 17.49
Weighted-Average Exercise Price Per Share, Options exercisable at end of period (in usd per share) $ 17.52 $ 17.71 $ 16.85