Calculation of Net Income per Common Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Schedule of Earnings Per Share, Basic and Diluted, by Common Class [Line Items]
Net income	$ 12,089	$ 10,990	$ 34,809	$ 26,673
Basic:
Basic weighted average EPS shares	24,979	24,893	24,952	24,463
Basic net income per share	$ 0.48	$ 0.44	$ 1.40	$ 1.09
Diluted:
Basic weighted average EPS shares	24,979	24,893	24,952	24,463
Dilutive common stock equivalents	92	56	97	72
Dilutive EPS shares	25,071	24,949	25,049	24,535
Diluted net income per share	$ 0.48	$ 0.44	$ 1.39	$ 1.09
Anti-dilutive shares	146	459	195	489