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, 2016	Mar. 31, 2015
Numerator:
Net income	$ 10,575	$ 12,605
Denominator:
Denominator for basic earnings per share–weighted average common shares	24,998	24,803
Effect of dilutive stock options	48	155
Effect of other common stock equivalents	399	555
Denominator for diluted earnings per share–adjusted weighted average common shares	25,445	25,513
Basic Earnings Per Share	$ 0.42	$ 0.51
Diluted Earnings Per Share	$ 0.42	$ 0.49