Earnings Per Share - Basic and Diluted Weighted Average Shares Outstanding Used to Compute Earnings Per Share (Detail) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share Basic And Diluted [Abstract]
Basic weighted average shares outstanding	37,359	37,083	36,958
Dilutive effect of stock options and restricted stock	785	873	897
Diluted weighted average shares outstanding	38,144	37,956	37,855
Basic earnings per share	$ 8.01	$ 5.53	$ 4.68
Diluted earnings per share	$ 7.85	$ 5.40	$ 4.57