Convertible Notes, Warrants, and Related Derivatives	12 Months Ended
Dec. 31, 2015
Debt Disclosure [Abstract]
Convertible Notes, Warrants, and Related Derivatives	Convertible Notes, Warrants, and Related Derivatives 2011 Convertible Notes and Common Stock Warrants In January 2011, the Company entered into a convertible promissory note agreement, or the 2011 Notes, and borrowed an aggregate of $40.6 million through 2012. The 2011 Notes were issued to related parties of which $30.9 million were issued to existing stockholders with holdings of 5% or more of the outstanding equity of the Company at the time of issuance. These holders were determined to be related parties because they include holders of convertible preferred stock and board members who could influence the conversion or redemption of the 2011 Notes. In conjunction with a Series E-5 convertible preferred stock offering in the year ended December 31, 2013, the Company, with the consent of at least 75% of the Convertible Note holders, amended the Note and Warrant Purchase Agreement under which the 2011 Notes were issued to allow for the conversion of 2011 Notes into 4,748,484 shares of Series E-4 convertible preferred stock. The outstanding principal and accrued interest of the 2011 Notes of $71.0 million were converted at a price equal to 66 2/3% of the Series E-5 offering price of $22.425 per share per the terms of the 2011 Notes. The modification of the 2011 Notes was treated as an extinguishment of debt, in which the resulting issuances of Series E-4 convertible preferred stock was recorded at its estimated fair value on the date of the extinguishment. The difference in the estimated fair value of the Series E-4 convertible preferred stock and the carrying values of the outstanding principal, accrued interest and the remaining debt issuance costs related to the 2011 Notes was recorded as a capital contribution in the amount of $32.0 million which was recognized to additional paid-in capital during the year ended December 31, 2013. The Company recognized the capital contribution as such because, immediately prior to the conversion, substantially all of the holders of the 2011 Notes were holders of the Company’s outstanding capital stock. In addition, the Company remeasured the embedded derivative to its fair value of approximately zero immediately prior to the conversion of the 2011 Notes in March 2013, as the execution of a qualified financing approached certainty, resulting in a gain of $1.8 million. As of the date of conversion, the Company was in compliance with all covenants in the 2011 Notes. Also, in connection with the issuance of the 2011 Notes, the Company issued warrants to purchase 77,521 shares of common stock and with a fair value of $0.2 million during the year ended December 31, 2012, with an exercise price of $0.15 per share. The relative fair value of the warrants was recorded as debt discount which was amortized to interest expense over the loan term. The Company recognized interest expense of $0.2 million from the amortization of the warrant related debt discounts during the year ended December 31, 2013. There was no unamortized warrant related debt discount balance beyond December 31, 2013. Also, in connection with the 2011 Notes, the Company determined that the conversion and redemption features were embedded derivatives requiring bifurcation and separate accounting. The fair value of the derivative liabilities associated with the 2011 Notes at the time of issuance was recognized as an additional debt discount and was amortized to interest expense over the term of the 2011 Notes. The Company recognized interest expense of $2.8 million from the amortization of the derivative liability related debt discounts during the year ended December 31, 2013. In the year ended December 31, 2013, the 2011 Notes converted into shares of Series E-4 convertible preferred stock. Immediately prior to the conversion, the Company determined that the fair value of the derivative liabilities associated with the convertible notes were reduced to zero. There was no unamortized derivative related debt discount balance beyond December 31, 2013. 2013 Convertible Notes, Common Stock Warrants, and Related Derivatives In October 2013, the Company entered into a convertible promissory note and warrant agreement, referred to as the 2013 Notes, to borrow up to $30.0 million. The Company borrowed $19.4 million in the fourth quarter of 2013. In January 2014, the Company issued an additional $4.3 million in 2013 Notes. The 2013 Notes bear interest at 12% per annum and mature in October 2014. In February 2014, in connection with the Company’s IPO, the 2013 Notes with a principal amount, accrued interest through the date of the IPO, remaining interest due through October 7, 2014, and derivative liability totaling $26.2 million converted into 1,637,846 shares of the Company’s common stock. In connection with the issuance of the 2013 Notes, the Company issued warrants to purchase 409,450 shares of common stock, which were net exercised for 405,594 shares of common stock upon the IPO. Additionally, the 2013 Notes had conversion and redemption features which were determined to be embedded derivatives, requiring bifurcation and separate fair value accounting. Immediately prior to the conversion, the Company determined that the fair value of the derivative liabilities associated with the convertible notes was reduced to $1.9 million, the value of interest due to note holders from the date of the IPO through the maturity date of the loan in October 2014. Upon the conversion of the 2013 Notes into shares of common stock, the Company applied extinguishment accounting resulting in a loss of $8.3 million. As of the date of conversion, the Company was in compliance with all covenants in the 2013 Notes. During the three months ended March 31, 2014, the Company recognized non-cash interest expense of $9.6 million related to the 2013 Notes, including amortization of warrant-related debt discount of approximately $0.4 million up to the date of conversion, amortization of the derivative-related debt discount of $0.6 million up to the date of conversion, accrued interest of $0.3 million up to the date of conversion and a loss on extinguishment of $8.3 million upon conversion of the 2013 Notes into common stock.

Convertible Notes, Warrants, and Related Derivatives

2011 Convertible Notes and Common Stock Warrants

In January 2011, the Company entered into a convertible promissory note agreement, or the 2011 Notes, and borrowed an aggregate of $40.6 million through 2012. The 2011 Notes were issued to related parties of which $30.9 million were issued to existing stockholders with holdings of 5% or more of the outstanding equity of the Company at the time of issuance. These holders were determined to be related parties because they include holders of convertible preferred stock and board members who could influence the conversion or redemption of the 2011 Notes.

In conjunction with a Series E-5 convertible preferred stock offering in the year ended December 31, 2013, the Company, with the consent of at least 75% of the Convertible Note holders, amended the Note and Warrant Purchase Agreement under which the 2011 Notes were issued to allow for the conversion of 2011 Notes into 4,748,484 shares of Series E-4 convertible preferred stock. The outstanding principal and accrued interest of the 2011 Notes of $71.0 million were converted at a price equal to 66 2/3% of the Series E-5 offering price of $22.425 per share per the terms of the 2011 Notes. The modification of the 2011 Notes was treated as an extinguishment of debt, in which the resulting issuances of Series E-4 convertible preferred stock was recorded at its estimated fair value on the date of the extinguishment. The difference in the estimated fair value of the Series E-4 convertible preferred stock and the carrying values of the outstanding principal, accrued interest and the remaining debt issuance costs related to the 2011 Notes was recorded as a capital contribution in the amount of $32.0 million which was recognized to additional paid-in capital during the year ended December 31, 2013. The Company recognized the capital contribution as such because, immediately prior to the conversion, substantially all of the holders of the 2011 Notes were holders of the Company’s outstanding capital stock. In addition, the Company remeasured the embedded derivative to its fair value of approximately zero immediately prior to the conversion of the 2011 Notes in March 2013, as the execution of a qualified financing approached certainty, resulting in a gain of $1.8 million. As of the date of conversion, the Company was in compliance with all covenants in the 2011 Notes.

Also, in connection with the issuance of the 2011 Notes, the Company issued warrants to purchase 77,521 shares of common stock and with a fair value of $0.2 million during the year ended December 31, 2012, with an exercise price of $0.15 per share. The relative fair value of the warrants was recorded as debt discount which was amortized to interest expense over the loan term. The Company recognized interest expense of $0.2 million from the amortization of the warrant related debt discounts during the year ended December 31, 2013. There was no unamortized warrant related debt discount balance beyond December 31, 2013.

Also, in connection with the 2011 Notes, the Company determined that the conversion and redemption features were embedded derivatives requiring bifurcation and separate accounting. The fair value of the derivative liabilities associated with the 2011 Notes at the time of issuance was recognized as an additional debt discount and was amortized to interest expense over the term of the 2011 Notes. The Company recognized interest expense of $2.8 million from the amortization of the derivative liability related debt discounts during the year ended December 31, 2013. In the year ended December 31, 2013, the 2011 Notes converted into shares of Series E-4 convertible preferred stock. Immediately prior to the conversion, the Company determined that the fair value of the derivative liabilities associated with the convertible notes were reduced to zero. There was no unamortized derivative related debt discount balance beyond December 31, 2013.

2013 Convertible Notes, Common Stock Warrants, and Related Derivatives

In October 2013, the Company entered into a convertible promissory note and warrant agreement, referred to as the 2013 Notes, to borrow up to $30.0 million. The Company borrowed $19.4 million in the fourth quarter of 2013. In January 2014, the Company issued an additional $4.3 million in 2013 Notes. The 2013 Notes bear interest at 12% per annum and mature in October 2014. In February 2014, in connection with the Company’s IPO, the 2013 Notes with a principal amount, accrued interest through the date of the IPO, remaining interest due through October 7, 2014, and derivative liability totaling $26.2 million converted into 1,637,846 shares of the Company’s common stock.

In connection with the issuance of the 2013 Notes, the Company issued warrants to purchase 409,450 shares of common stock, which were net exercised for 405,594 shares of common stock upon the IPO.

Additionally, the 2013 Notes had conversion and redemption features which were determined to be embedded derivatives, requiring bifurcation and separate fair value accounting. Immediately prior to the conversion, the Company determined that the fair value of the derivative liabilities associated with the convertible notes was reduced to $1.9 million, the value of interest due to note holders from the date of the IPO through the maturity date of the loan in October 2014.

Upon the conversion of the 2013 Notes into shares of common stock, the Company applied extinguishment accounting resulting in a loss of $8.3 million. As of the date of conversion, the Company was in compliance with all covenants in the 2013 Notes.

During the three months ended March 31, 2014, the Company recognized non-cash interest expense of $9.6 million related to the 2013 Notes, including amortization of warrant-related debt discount of approximately $0.4 million up to the date of conversion, amortization of the derivative-related debt discount of $0.6 million up to the date of conversion, accrued interest of $0.3 million up to the date of conversion and a loss on extinguishment of $8.3 million upon conversion of the 2013 Notes into common stock.