Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Numerator:
Net Income	$ 15,770	$ 12,889
Denominator:
Weighted average basic shares	29,671	28,218
Dilutive potential common shares	558	535
Weighted average fully diluted shares	30,229	28,753
Earnings per share:
Basic	$ 0.53	$ 0.46
Diluted	$ 0.52	$ 0.45
Outstanding common stock equivalents having no dilutive effect	42	238