Computation of Earnings Per Share - Summary of Calculation of Basic Earnings Per Common Share and Diluted Earnings Per Common Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Numerator:
Net income	$ 37,291	$ 28,111
Denominator:
Denominator for basic earnings per share–weighted average common shares	26,285	26,070
Effect of dilutive stock options	121	96
Effect of other common stock equivalents	265	326
Denominator for diluted earnings per share–adjusted weighted average common shares	26,671	26,492
Basic Earnings Per Share	$ 1.42	$ 1.08
Diluted Earnings Per Share	$ 1.40	$ 1.06