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, 2018	Mar. 31, 2017
Numerator:
Net income	$ 21,125	$ 11,395
Denominator:
Denominator for basic earnings per share–weighted average common shares	25,698	25,225
Effect of dilutive stock options	172	118
Effect of other common stock equivalents	438	628
Denominator for diluted earnings per share–adjusted weighted average common shares	26,308	25,971
Basic Earnings Per Share	$ 0.82	$ 0.45
Diluted Earnings Per Share	$ 0.80	$ 0.44