Earnings Per Share - Computation of Basic Earnings and Diluted Earnings Per Share Data (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Numerator for basic and diluted earnings per share:
Net income	$ 39,284	$ 40,390	$ 140,726	$ 99,737
Denominator:
Weighted-average basic common shares outstanding (in shares)	40,261	38,765	40,013	38,614
Assumed conversion of dilutive securities:
Stock awards (in shares)	1,345	1,515	1,480	1,401
Denominator for diluted earnings per share - Adjusted weighted-average shares (in shares)	41,606	40,280	41,493	40,015
Earnings per common share:
Basic (usd per share)	$ 0.98	$ 1.04	$ 3.52	$ 2.58
Diluted (usd per share)	$ 0.94	$ 1.00	$ 3.39	$ 2.49