Preferred Stock Warrant Liabilities	9 Months Ended
Sep. 30, 2017
Preferred Stock Warrant Liabilities [Abstract]
Preferred Stock Warrant Liabilities	11. Preferred Stock Warrant Liabilities In November 2012, in connection with borrowings under a convertible note, the Company issued warrants to purchase shares of Series C or New Preferred. The warrants were only exercisable if the Convertible Notes were converted into Series C or New Preferred. The warrants’ exercise price is $0.001 per share and they have a seven year term. On March 27, 2013 the Company closed the Series D financing. The warrants were converted into warrants to purchase 207,177 shares of Series D convertible preferred stock. The Company recognized a charge of $0.5 million and $0.7 million related to the change in the fair value of the warrants for the three and nine months ended September 30, 2016. Upon the IPO, the Series D preferred stock warrants converted into common stock warrants and were reclassified to additional paid-in-capital in the Company's balance sheet. As a result, the warrants are no longer subject to fair value remeasurement. As of September 30, 2017, 127,918 warrants were outstanding. In June 2014, in connection with borrowings under the Second Amendment (Note 8), the Company issued warrants to purchase 20,136 shares of Series D Preferred Stock at $7.31 per share that expire June 2024. The fair value of the warrants was determined by using an option pricing model prepared by a third-party based on an allocation of the Company’s aggregate value to the outstanding equity instruments, applying a 30% discount to the warrant value for lack of marketability. The fair value of the warrant, $0.1 million, was recorded as a debt discount and is being amortized over the loan repayment period to interest expense. The Company recognized a charge of $15,000 and income of $41,000 related to change in the fair value of the warrants for the three and nine months ended September 30, 2016. The warrants were converted into warrants to purchase common stock upon the completion of the IPO in 2016, and were reclassified to additional paid-in-capital in the Company's balance sheet. One of the warrants for 10,068 shares was exercised through a cashless exercise on October 26, 2016 resulting in the issuance of a net 7,310 shares of the Company's common stock, and the other warrant for 10,068 was exercised through a cashless exercise on May 2, 2017 resulting in the issuance of a net 8,077 shares.

11. Preferred Stock Warrant Liabilities

In November 2012, in connection with borrowings under a convertible note, the Company issued warrants to purchase shares of Series C or New Preferred. The warrants were only exercisable if the Convertible Notes were converted into Series C or New Preferred. The warrants’ exercise price is $0.001 per share and they have a seven year term. On March 27, 2013 the Company closed the Series D financing. The warrants were converted into warrants to purchase 207,177 shares of Series D convertible preferred stock. The Company recognized a charge of $0.5 million and $0.7 million related to the change in the fair value of the warrants for the three and nine months ended September 30, 2016. Upon the IPO, the Series D preferred stock warrants converted into common stock warrants and were reclassified to additional paid-in-capital in the Company's balance sheet. As a result, the warrants are no longer subject to fair value remeasurement. As of September 30, 2017, 127,918 warrants were outstanding.

In June 2014, in connection with borrowings under the Second Amendment (Note 8), the Company issued warrants to purchase 20,136 shares of Series D Preferred Stock at $7.31 per share that expire June 2024. The fair value of the warrants was determined by using an option pricing model prepared by a third-party based on an allocation of the Company’s aggregate value to the outstanding equity instruments, applying a 30% discount to the warrant value for lack of marketability. The fair value of the warrant, $0.1 million, was recorded as a debt discount and is being amortized over the loan repayment period to interest expense. The Company recognized a charge of $15,000 and income of $41,000 related to change in the fair value of the warrants for the three and nine months ended September 30, 2016. The warrants were converted into warrants to purchase common stock upon the completion of the IPO in 2016, and were reclassified to additional paid-in-capital in the Company's balance sheet. One of the warrants for 10,068 shares was exercised through a cashless exercise on October 26, 2016 resulting in the issuance of a net 7,310 shares of the Company's common stock, and the other warrant for 10,068 was exercised through a cashless exercise on May 2, 2017 resulting in the issuance of a net 8,077 shares.