Stockholders' Equity - Schedule of Number of Shares of Common Stock Reserved for Future Issuance (Detail) - shares	Sep. 30, 2015	Dec. 31, 2014
Class of Stock [Line Items]
Common stock shares reserved for future issuance	5,254,094	5,292,012
Shares Available for Issuance Under the 2013 Stock Option and Incentive Plan [Member]
Class of Stock [Line Items]
Common stock shares reserved for future issuance	1,694,682	1,375,555
Shares Available for Issuance Under the 2013 Employee Stock Purchase Plan [Member]
Class of Stock [Line Items]
Common stock shares reserved for future issuance	788,503	788,503
Unvested Restricted Stock [Member]
Class of Stock [Line Items]
Common stock shares reserved for future issuance	945,276	335,933
Common Stock Options Outstanding [Member]
Class of Stock [Line Items]
Common stock shares reserved for future issuance	1,825,633	2,792,021