Summary of Significant Accounting Policies - Reconciliation of Basic and Diluted Income (Loss) Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share Basic And Diluted [Abstract]
Net income	$ 7,003	$ 5,415	$ 5,717	$ 2,270	$ 5,807	$ 9,293	$ 5,241	$ 5,284	$ 20,405	$ 25,625	$ 27,122
Denominator:
Weighted average common shares outstanding, basic									89,340,589	87,920,230	88,680,322
Basic earnings per share:
Net income per share, basic	$ 0.08	$ 0.06	$ 0.06	$ 0.03	$ 0.07	$ 0.11	$ 0.06	$ 0.06	$ 0.23	$ 0.29	$ 0.31
Denominator:
Weighted average common shares outstanding, basic									89,340,589	87,920,230	88,680,322
Dilutive securities:
Stock options									1,373,733	1,815,489	1,856,707
Restricted stock units									588,734	559,466	406,705
Weighted average common shares outstanding, diluted									91,303,056	90,295,185	90,943,734
Diluted earnings per share:
Net income per share, diluted	$ 0.08	$ 0.06	$ 0.06	$ 0.02	$ 0.06	$ 0.10	$ 0.06	$ 0.06	$ 0.22	$ 0.28	$ 0.30