Reconciliation of Net Income Per Share - Summary of Reconciliation of Net Income (Loss) Per Share (Detail) (USD $) In Thousands, except Per 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
Earnings Per Share [Abstract]
Net income	$ 1,619	$ (3,840)	$ 5,200	$ 5,238	$ 4,485	$ 5,052	$ 4,770	$ 2,871	$ 8,217	$ 17,178	$ 24,268
Weighted average shares outstanding	18,970	17,979	17,779	17,656	17,527	17,302	17,136	17,055	17,887	17,176	17,009
Effective of dilutive stock options	347		393	306	290	148	36	107	366	84	105
Diluted shares outstanding	19,317	17,979	18,172	17,962	17,817	17,450	17,172	17,162	18,253	17,260	17,114
Basic net income per share	$ 0.09	$ (0.21)	$ 0.29	$ 0.30	$ 0.25	$ 0.29	$ 0.28	$ 0.17	$ 0.46	$ 1.00	$ 1.43
Diluted net income per share	$ 0.08	$ (0.21)	$ 0.29	$ 0.29	$ 0.25	$ 0.29	$ 0.28	$ 0.17	$ 0.45	$ 1.00	$ 1.42