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								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Numerator for basic and diluted earnings per share:
Net income	$ 54,094	$ 39,284	$ 53,892	$ 47,550	$ 46,790	$ 40,390	$ 31,999	$ 27,348	$ 194,820	$ 146,527	$ 147,462
Denominator:
Weighted-average basic common shares outstanding									40,035	38,640	38,445
Assumed conversion of dilutive securities:
Share-based awards (in shares)									1,491	1,465	1,678
Denominator for diluted earnings per share    - Adjusted weighted-average shares	41,925	41,606	41,416	41,144	40,736	40,280	39,813	39,585	41,526	40,105	40,123
Earnings per common share:
Basic (USD per share)									$ 4.87	$ 3.79	$ 3.84
Diluted (USD per share)	$ 1.29	$ 0.94	$ 1.30	$ 1.16	$ 1.15	$ 1.00	$ 0.80	$ 0.69	$ 4.69	$ 3.65	$ 3.68