Summary of Significant Accounting Policies - Reconciliation of Shares Used to Determine Net Income per Share (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share Disclosure [Line Items]
Net (loss) income	$ (3,056)	$ 5,734
Weighted average number of shares - basic	42,403,029	41,507,941
Shares underlying options	0	1,995,948
Weighted average number of shares outstanding - diluted	42,403,029	43,503,889