Credit Facility and Term Loans - Additional Information (Details) - USD ($)		3 Months Ended		6 Months Ended		12 Months Ended
	Nov. 23, 2018	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2018	Dec. 31, 2019
Debt Instrument [Line Items]
Available balance of credit facility		$ 0		$ 0			$ 0
Interest expense of credit facilities		600,000	$ 800,000	1,200,000	$ 1,500,000
Deferred debt issuance costs		400,000	200,000	400,000	200,000
Borrowings, outstanding		31,900,000		31,900,000			35,100,000
Interest expense		1,084,000	1,288,000	2,217,000	2,501,000
Term Loan
Debt Instrument [Line Items]
Credit facility maximum borrowing amount						$ 15,000,000
Debt instrument maturity month and year						2023-01
Borrowings, outstanding		15,000,000		15,000,000			15,000,000
Interest expense		500,000	500,000	1,000,000	1,000,000
Term Loan | Maximum
Debt Instrument [Line Items]
Debt issuance costs		300,000	$ 300,000	300,000	$ 300,000
Horizon Term Loan
Debt Instrument [Line Items]
Debt offset against and expense over the term						5 years
Deferred debt issuance costs		697,000		$ 697,000		$ 1,000,000	836,000
Warrants term						10 years
Fair value on issuance						$ 900,000
Debt discount						$ 900,000
Horizon Term Loan | Common Stock
Debt Instrument [Line Items]
Warrants to purchase shares						76,923
Warrants to purchase shares, exercise price						$ 15.60
London Interbank Offered Rate ("LIBOR") | Term Loan
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate						9.90%
Description of variable rate basis				one-month LIBOR
London Interbank Offered Rate ("LIBOR") | Term Loan | Minimum
Debt Instrument [Line Items]
Potential additional interest						2.50%
Mid Cap Prior Credit Facility
Debt Instrument [Line Items]
Unamortized debt issuance costs						$ 700,000
Mid Cap Credit Facility
Debt Instrument [Line Items]
Credit facility maximum borrowing amount	$ 25,000,000
Additional increase in borrowing amount	$ 50,000,000
Line of credit facility, unused capacity, commitment fee percentage	0.50%
Line of credit facility, minimum liquidity financial covenant requirement in cash on hand	$ 5,000,000
Debt issuance costs						$ 1,300,000
Debt offset against and expense over the term						3 years
Line of credit, outstanding		19,100,000		$ 19,100,000			23,000,000
Available balance of credit facility		$ 0		$ 0			$ 0
Current borrowing capacity						$ 25,000,000
Mid Cap Credit Facility | London Interbank Offered Rate ("LIBOR")
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	5.75%
Credit Facility and Term Loan
Debt Instrument [Line Items]
Line of credit facility covenant minimum liquidity requirement in unrestricted cash						$ 5,000,000