Reconciliation of Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Earnings Per Share [Abstract]
Net income for basic and diluted earnings per share	$ 26,592	$ 13,154	$ 43,822	$ 26,390
Weighted average shares outstanding - basic	33,428	33,171	33,423	33,165
Dilutive effect of restricted stock	451	284	404	307
Weighted average shares outstanding - diluted	33,879	33,455	33,827	33,472
Earnings per share - basic	$ 0.80	$ 0.40	$ 1.31	$ 0.80
Earnings per share - diluted	$ 0.78	$ 0.39	$ 1.30	$ 0.79