Stockholders' Equity - Summary of Reserved Shares of Common Stock for Future Issuance (Details)	Sep. 30, 2014	Dec. 31, 2013
Class of Stock [Line Items]
Common stock, shares reserved for future issuance	3,151,792	13,628,787
Series A redeemable convertible preferred stock
Class of Stock [Line Items]
Common stock, shares reserved for future issuance		3,672,673
Series B redeemable convertible preferred stock
Class of Stock [Line Items]
Common stock, shares reserved for future issuance		2,253,157
Series C redeemable convertible preferred stock
Class of Stock [Line Items]
Common stock, shares reserved for future issuance		6,296,451
Options to purchase common stock
Class of Stock [Line Items]
Common stock, shares reserved for future issuance	1,596,538	1,251,398
Shares available for future issuance
Class of Stock [Line Items]
Common stock, shares reserved for future issuance	1,555,254	155,108