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]	6 Months Ended
	Jun. 30, 2018 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Unvested at December 31, 2017	1,164,040
Number of Shares, Granted	296,005
Number of Shares, Vested	(332,586)
Number of Shares, Forfeited	(171,212)
Number of Shares, Unvested at June 30, 2018	956,247