Earnings Per Share - Basic and Diluted Weighted Average Shares Outstanding Used to Compute Earnings Per Share (Detail) - $ / shares shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Earnings Per Share Basic And Diluted [Abstract]
Basic weighted average shares outstanding	37,508	37,340	37,489	37,322
Dilutive effect of stock options and restricted stock	596	813	640	793
Diluted weighted average shares outstanding	38,104	38,153	38,129	38,115
Basic earnings per share	$ 1.79	$ 2.25	$ 3.94	$ 4.25
Diluted earnings per share	$ 1.77	$ 2.20	$ 3.87	$ 4.16