Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Basic earnings per share
Net Income	$ 57,518	$ 70,672	$ 63,401
Less: earnings allocated to participating securities, Income	511	596	582
Net income available to common shareholders, Total	$ 57,007	$ 70,076	$ 62,819
Net income available to common shareholders, (in shares)	50,540	50,477	47,578
Less: earnings allocated to participating securities, (in shares)	0	0	0
Net income available to common shareholders, Total (in shares)	50,540	50,477	47,578
Net income available to common shareholders, (in usd per share)	$ 1.14	$ 1.40	$ 1.33
Less: earnings allocated to participating securities, (in usd per share)	0.01	0.01	0.01
Basic earnings (usd per share)	$ 1.13	$ 1.39	$ 1.32
Effect of dilutive securities
Stock options and restricted stock, Income	$ 0	$ 0	$ 0
Stock options and restricted stock, (in shares)	110	165	188
Stock options and restricted stock, (in usd per share)	$ 0	$ (0.01)	$ 0
Diluted earnings per share
Net income available to common shareholders plus assumed conversions, Income	$ 57,007	$ 70,076	$ 62,819
Net income available to common shareholders plus assumed conversions, (in shares)	50,650	50,642	47,766
Diluted earnings (usd per share)	$ 1.13	$ 1.38	$ 1.32