Debt - MidCap Facility Agreement (Details) - USD ($)			12 Months Ended
	Nov. 06, 2018	Mar. 08, 2018	Dec. 31, 2018	Dec. 31, 2017
Line of Credit Facility [Line Items]
Unamortized debt discount			$ 3,857,000	$ 2,023,000
Minimum liquidity covenant amount			$ 5,000,000
Latest effective date of minimum liquidity covenant			2020-03
Amended credit facility with MidCap
Line of Credit Facility [Line Items]
Unamortized debt discount			$ 1,300,000
Minimum liquidity covenant amount		$ 5,000,000
Latest effective date of minimum liquidity covenant	2020-03	2019-03
Amended credit facility with MidCap | Maximum
Line of Credit Facility [Line Items]
Effective date of financial covenants of amended credit facility	2020-04	2019-04
Amended credit facility with MidCap | Minimum
Line of Credit Facility [Line Items]
Effective date of financial covenants of amended credit facility	2019-04	2018-04
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 | Revolving credit facility
Line of Credit Facility [Line Items]
Maximum borrowing capacity			$ 22,500,000
Line of credit			$ 11,000,000
Line of credit, expiration month and year			2022-12
Interest rate			8.35%
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]
Maximum borrowing capacity			$ 5,000,000