Debt - Long-term debt (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Term loan (matures October 1, 2023)	$ 10,000,000	$ 10,000,000
Debt issuance costs, net of amortization	(208,000)	(222,000)
Accrued final payment fee	40,000	16,000
Long-term debt, net	$ 9,832,000	$ 9,794,000
Maturity date	Oct. 01, 2023
Annual interest rate	7.85%
Debt issuance costs amortized and recognized as Interest expense	$ 21,000
Effective interest rate on long-term debt	9.77%
Interest expense.
Debt Instrument [Line Items]
Accrued final payment fee	$ 24,000