Redeemable Convertible Preferred Stock Tranche Liability	6 Months Ended
Jun. 30, 2017
Temporary Equity Disclosure [Abstract]
Redeemable Convertible Preferred Stock Tranche Liability	Redeemable Convertible Preferred Stock Tranche Liability In July 2015, the Company entered into the Series C Preferred Stock Purchase Agreement (“the Series C Agreement”) for the issuance of up to 80,337,411 shares of Series C redeemable convertible preferred stock at a price of $0.4979 per share, in multiple closings. The initial closing occurred on July 10, 2015, whereby 35,147,617 shares of Series C redeemable convertible preferred stock were issued for gross proceeds of approximately $17.5 million. According to the initial terms of the Series C Agreement, the Company could issue 45,189,794 additional shares under the same terms as the initial closing, in a subsequent closing (“Series C Second Tranche”) contingent upon the achievement of certain development milestones. On the date of the initial closing, the Company recorded a Series C redeemable convertible preferred stock liability of $1.0 million, as the fair value of the obligation/right to complete the Series C Second Tranche. In March 2016, the Company completed the closing of the Series C Second Tranche and issued 45,189,794 shares of Series C redeemable convertible preferred stock for net cash proceeds of $22.5 million. At this time, the Series C redeemable convertible preferred stock liability was remeasured at $5.8 million, determined using a hybrid method of the Option Pricing Model with a 67% weighted value per share and the PWERM with a 33% weighted value per share. Upon the closing of the Series C Second Tranche, the Series C redeemable convertible preferred stock liability was terminated and the balance of the liability of $5.8 million was reclassified to redeemable convertible preferred stock. The Company recorded a charge of $4.2 million for the increase in the fair value of the Series C redeemable convertible preferred stock liability in the condensed consolidated statements of operations for the six months ended June 30, 2016. There were no such charges incurred for the three months ended June 30, 2016 and the three and six months ended June 30, 2017.

Redeemable Convertible Preferred Stock Tranche Liability

In July 2015, the Company entered into the Series C Preferred Stock Purchase Agreement (“the Series C Agreement”) for the issuance of up to 80,337,411 shares of Series C redeemable convertible preferred stock at a price of $0.4979 per share, in multiple closings. The initial closing occurred on July 10, 2015, whereby 35,147,617 shares of Series C redeemable convertible preferred stock were issued for gross proceeds of approximately $17.5 million. According to the initial terms of the Series C Agreement, the Company could issue 45,189,794 additional shares under the same terms as the initial closing, in a subsequent closing (“Series C Second Tranche”) contingent upon the achievement of certain development milestones. On the date of the initial closing, the Company recorded a Series C redeemable convertible preferred stock liability of $1.0 million, as the fair value of the obligation/right to complete the Series C Second Tranche.

In March 2016, the Company completed the closing of the Series C Second Tranche and issued 45,189,794 shares of Series C redeemable convertible preferred stock for net cash proceeds of $22.5 million. At this time, the Series C redeemable convertible preferred stock liability was remeasured at $5.8 million, determined using a hybrid method of the Option Pricing Model with a 67% weighted value per share and the PWERM with a 33% weighted value per share. Upon the closing of the Series C Second Tranche, the Series C redeemable convertible preferred stock liability was terminated and the balance of the liability of $5.8 million was reclassified to redeemable convertible preferred stock. The Company recorded a charge of $4.2 million for the increase in the fair value of the Series C redeemable convertible preferred stock liability in the condensed consolidated statements of operations for the six months ended June 30, 2016. There were no such charges incurred for the three months ended June 30, 2016 and the three and six months ended June 30, 2017.