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, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share Basic And Diluted [Abstract]
Net income	$ 12,972	$ 157,208	$ 3,495	$ 2,618	$ 7,003	$ 5,415	$ 5,717	$ 2,270	$ 176,293	$ 20,405	$ 25,625
Denominator:
Weighted average common shares outstanding, basic									90,272,257	89,340,589	87,920,230
Basic earnings per share:
Net income per share, basic	$ 0.14	$ 1.74	$ 0.04	$ 0.03	$ 0.08	$ 0.06	$ 0.06	$ 0.03	$ 1.95	$ 0.23	$ 0.29
Denominator:
Weighted average common shares outstanding, basic									90,272,257	89,340,589	87,920,230
Dilutive securities:
Stock options									906,519	1,373,733	1,815,489
Restricted stock units									713,181	588,734	559,466
Weighted average common shares outstanding, diluted									91,891,957	91,303,056	90,295,185
Diluted earnings per share:
Net income per share, diluted	$ 0.14	$ 1.71	$ 0.04	$ 0.03	$ 0.08	$ 0.06	$ 0.06	$ 0.02	$ 1.92	$ 0.22	$ 0.28