Debt (Details) - USD ($)			1 Months Ended		4 Months Ended	12 Months Ended
	Jul. 01, 2013	Feb. 28, 2013	Jun. 30, 2014	Feb. 28, 2013	Dec. 31, 2012	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	May. 29, 2013	Nov. 30, 2012	Jan. 31, 2012	Apr. 28, 2008
Debt
Debt issuance costs						$ 100,000
Estimated future principal payments due under the Credit Facility
Payments of long term debt						$ 638,000
Series A preferred stock
Estimated future principal payments due under the Credit Facility
Conversion of convertible promissory notes into Series A preferred stock (in shares)								16,623,092
Preferred stock, shares issued					23,975,000				23,975,000
Number of shares of preferred stock converted into shares of common stock								(57,598,092)
Series A-1 preferred stock
Estimated future principal payments due under the Credit Facility
Conversion of convertible promissory notes into Series A preferred stock (in shares)								6,750,000
Number of shares of preferred stock converted into shares of common stock								(6,750,000)
Warrant
Debt
Exercise price (in dollars per share)						$ 7.25
Series A preferred stock warrant
Debt
Warrants exercisable into stock (in shares)	1,940,000
Exercise price (in dollars per share)	$ 1.00
10% Convertible promissory notes | Series A preferred stock
Estimated future principal payments due under the Credit Facility
Aggregate principal amount		$ 15,700,000		$ 15,700,000
Accrued interest		$ 900,000		$ 900,000
Conversion of convertible promissory notes into Series A preferred stock (in shares)		16,623,092		16,623,092
Conversion price (in dollars per share)		$ 1.00		$ 1.00
Short term convertible notes issued January 2012
Debt
Interest rate (as a percent)												10.00%
Estimated future principal payments due under the Credit Facility
Aggregate principal amount												$ 6,000,000
Short term convertible notes issued September and November 2012
Debt
Interest rate (as a percent)											10.00%
Estimated future principal payments due under the Credit Facility
Aggregate principal amount											$ 9,700,000
Short term borrowings with related parties, net of debt discount											$ 9,400,000
Short term convertible notes issued September and November 2012 | Series A preferred stock warrant | Series A preferred stock | Maximum
Estimated future principal payments due under the Credit Facility
Aggregate purchase price of warrants					$ 100,000
Short term convertible notes issued September 2012
Estimated future principal payments due under the Credit Facility
Fair value of beneficial conversion feature				$ 300,000
Short term convertible notes issued September 2012 | Interest Expense.
Estimated future principal payments due under the Credit Facility
Amortization of debt discount and beneficial conversion								$ 200,000	$ 100,000
Pfizer note
Debt
Interest rate (as a percent)													8.931%
Estimated future principal payments due under the Credit Facility
Aggregate principal amount													$ 5,000,000
Outstanding principal amount										$ 7,800,000
Accrued interest during period								$ 300,000	$ 600,000
Pfizer note | Series A-1 preferred stock
Estimated future principal payments due under the Credit Facility
Preferred stock, shares issued										6,750,000
Number of shares of preferred stock converted into shares of common stock	966,218
Credit Facility
Debt
Maximum borrowing capacity						$ 20,000,000
Percentage of final payment equal to amount drawn under the Credit Facility						8.00%
Estimated future principal payments due under the Credit Facility
2016						$ 1,604,000
2017						1,709,000
2018						1,049,000
Total						4,362,000
Interest expense						500,000	$ 300,000
Interest payments						300,000	$ 100,000
Term A Loan
Debt
Maximum borrowing capacity						$ 5,000,000
Period of consecutive equal monthly installments of principal and interest						36 months
Interest rate (as a percent)						6.40%
Term A Loan | Warrant
Debt
Warrants exercisable into stock (in shares)			8,230
Exercise price (in dollars per share)			$ 15.19
Unamortized discount			$ 100,000
Term A Loan | Secured promissory notes
Debt
Proceeds from issuance of debt			$ 5,000,000
Term B Loan
Debt
Maximum borrowing capacity						$ 15,000,000
Remaining borrowing capacity						$ 15,000,000