Debt - MidCap Facility Agreement (Details) - USD ($)		12 Months Ended
	Aug. 08, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Sep. 01, 2016	Mar. 11, 2016	Dec. 31, 2015
Line of Credit Facility [Line Items]
Debt issuance costs				$ 3,543,000			$ 5,642,000
Fifth amendment credit facility with MidCap | Revolving credit facility
Line of Credit Facility [Line Items]
Maximum borrowing capacity					$ 22,500,000
Fifth amendment credit facility with MidCap | Term loan
Line of Credit Facility [Line Items]
Maximum borrowing capacity					5,000,000
Debt instrument, prepayment fee					$ 600,000
Amended credit facility with MidCap
Line of Credit Facility [Line Items]
Maximum borrowing capacity				17,873,000			$ 56,799,000
Debt issuance costs				$ 1,900,000
Amended credit facility with MidCap | Line of credit | Maximum
Line of Credit Facility [Line Items]
Debt default, interest rate increase				5.00%
Amended credit facility with MidCap | Forecast
Line of Credit Facility [Line Items]
Monthly term loan payments		$ 300,000	$ 200,000
Amended credit facility with MidCap | Revolving credit facility
Line of Credit Facility [Line Items]
Line of credit				$ 12,500,000
Interest rate				6.60%
Amended credit facility with MidCap | Revolving credit facility | LIBOR
Line of Credit Facility [Line Items]
Interest rate description				LIBOR plus 6.0%
Basis spread				6.00%
Amended credit facility with MidCap | Term loan
Line of Credit Facility [Line Items]
Line of credit				$ 4,800,000
Floor on interest rate				9.50%
Interest rate				9.50%
Amended credit facility with MidCap | Term loan | LIBOR
Line of Credit Facility [Line Items]
Interest rate description				("LIBOR") plus 8.0%
Basis spread				8.00%
Third amendment credit facility with MidC
Line of Credit Facility [Line Items]
Amendment fee amount						$ 500,000
Fourth Amendment to the amended credit facility with MidCap
Line of Credit Facility [Line Items]
Amendment fee amount	$ 200,000
Line of credit facility, increase in maximum borrowing capacity	$ 2,200,000