Debt Obligations - Narrative (Details) - USD ($)	1 Months Ended					12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2016	Dec. 31, 2014	May 31, 2014	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Imputed interest on working capital advance	$ 0					$ 0	$ 3,733,000
End of term fee due under the Loan Agreement						1,865,000	0	$ 0
Loss on extinguishment of debt						$ 4,876,000	$ 0	$ 0
Oxford/SVB [Member]
Debt Instrument [Line Items]
Shares of common stock exercisable through warrants (shares)				63,559
Warrants exercise price (in usd per share)				$ 9.44
Term of common stock warrant exercisable				10 years
Imputed interest on working capital advance				$ 600,000
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Revolving credit facility				4,000,000
Second Amendment [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
End of term fee due under revolving credit facility			$ 64,000
Term Loan [Member] | Second Amendment [Member]
Debt Instrument [Line Items]
Interest rate (percent)			7.00%
Prepayment penalty			$ 1,400,000.0
Repayments of debt	20,000,000
Loss on extinguishment of debt	1,500,000
Write-off of unamortized debt issuance costs and discount	$ 1,900,000
Term Loan [Member] | Second Amendment [Member] | Prime Rate [Member]
Debt Instrument [Line Items]
Basis spread on variable rate (percent)			3.25%
Term Loan [Member] | Loan And Security Agreement [Member]
Debt Instrument [Line Items]
Revolving credit facility				$ 20,000,000
Interest rate (percent)				8.75%
End of term fee due under the Loan Agreement			$ 1,000,000
Term Loan [Member] | Loan And Security Agreement [Member] | Prime Rate [Member]
Debt Instrument [Line Items]
Basis spread on variable rate (percent)				5.25%
Notes Payable, Other Payables [Member] | Endo Asset Purchase Agreement [Member]
Debt Instrument [Line Items]
Notes payable					$ 7,000,000
Endo Asset Purchase Agreement [Member]
Debt Instrument [Line Items]
Imputed interest on working capital advance					$ 4,700,000
Term of agreement					8 years
Endo Asset Purchase Agreement [Member] | Notes Payable, Other Payables [Member]
Debt Instrument [Line Items]
Notes payable					$ 7,000,000
Write-off of unamortized discount		$ 3,400,000