Stockholders' Equity - Summary of Roll Forward of Restricted Stock Activity Pursuant to the 2010 and 2013 Stock Plan (Detail) - 2010 and 2013 Stock Incentive Plans [Member] - Unvested Restricted Stock [Member]	9 Months Ended
	Sep. 30, 2017 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Unvested at December 31, 2016	1,297,054
Number of Shares, Granted	775,819
Number of Shares, Vested	(520,098)
Number of Shares, Cancelled	(165,833)
Number of Shares, Unvested at September 30, 2017	1,386,942