Net Income Per Share (Calculation of Net Income per Common Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Earnings Per Share [Abstract]
Net income	$ 10,995	$ 11,142	$ 32,553	$ 29,052
Basic:
Basic weighted average EPS shares	24,526	25,074	24,692	25,045
Basic net income per share	$ 0.45	$ 0.44	$ 1.32	$ 1.16
Diluted:
Basic weighted average EPS shares	24,526	25,074	24,692	25,045
Dilutive common stock equivalents	77	78	87	90
Dilutive EPS shares	24,603	25,152	24,779	25,135
Diluted net income per share	$ 0.45	$ 0.44	$ 1.31	$ 1.16
Anti-dilutive shares	7	64	8	59