Summary of Significant Accounting Policies - Reconciliation of Shares Used to Determine Net Income per Share (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share Disclosure [Line Items]
Net income	$ 2,104	$ 4,789	$ 16,362	$ 12,562
Weighted average number of shares - basic	41,869,528	33,873,479	41,648,439	33,265,470
Weighted average number of shares outstanding - diluted	43,463,982	35,297,585	43,173,427	34,341,930
Options [Member]
Earnings Per Share Disclosure [Line Items]
Shares underlying options	1,594,454	1,424,106	1,524,988	1,076,460