Net Income Per Share - Summary of Net Income Per Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Earnings Per Share [Abstract]
Net income	$ 3,971		$ 3,934		$ 11,561		$ 11,400
Weighted-average common shares outstanding	17,410,000		17,235,000		17,359,000		17,195,000
Basic earnings per share	$ 0.23	[1]	$ 0.23	[1]	$ 0.67	[1]	$ 0.66	[1]
Weighted-average common shares outstanding	17,409,820	[1]	17,234,850	[1]	17,358,818	[1]	17,194,979	[1]
Common stock equivalents due to effect of stock options	193,000		154,000		171,000		155,000
Total weighted-average common shares and equivalents	17,603,000		17,389,000		17,530,000		17,350,000
Diluted earnings per share	$ 0.23	[1]	$ 0.22	[1]	$ 0.66	[1]	$ 0.66	[1]

[1] Outstanding shares and per share data have been adjusted to reflect the six-for-five stock split declared April 16, 2013.