Stockholders' Equity - Basic and Diluted Net Income Per Common Shares (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Equity [Abstract]
Net income	$ 6,912	$ 4,652	$ 4,291	$ 4,890	$ 8,015	$ 5,762	$ 6,828	$ 6,925	$ 20,745	$ 27,530	$ 26,984
Weighted average shares of common stock outstanding									21,621,466	21,648,654	21,924,748
Dilutive effect of restricted stock and RSUs									469,304	361,869	472,839
Weighted average shares of common stock and common stock equivalents									22,090,770	22,010,523	22,397,587
Basic	$ 0.32	$ 0.21	$ 0.20	$ 0.23	$ 0.37	$ 0.27	$ 0.32	$ 0.32	$ 0.96	$ 1.27	$ 1.23
Diluted	$ 0.31	$ 0.21	$ 0.19	$ 0.22	$ 0.36	$ 0.26	$ 0.31	$ 0.32	$ 0.94	$ 1.25	$ 1.20