Borrowings (Details) - USD ($) $ in Thousands		9 Months Ended
	May 16, 2018	Sep. 30, 2018	Sep. 30, 2019	Dec. 31, 2018	[1]
Term Loans
Amount of term loan facility	$ 50,000
Net proceeds from the loan	$ 49,300	$ 49,292
Percentage of premium payable on redemption of the term loan	1.00%
Amount of fee payable upon closing of the term loan	$ 500
Exit fee (as a percent)	3.00%
Expiration term of exit fee	10 years
Minimum unrestricted cash and cash equivalents to be maintained	$ 50,000
Additional default interest rate	4.00%
Future debt payment obligations
2020			$ 2,083
2021			25,000
2022			24,892
Total			51,975
Less: Unamortized discount and debt issuance costs			(827)
Less: Unaccreted value of final fee			(1,345)
Loan payable, long term			$ 49,803	$ 49,209
At Maturity
Term Loans
Final payment fee (as a percent)	3.95%
Prior to first anniversary of closing date
Term Loans
Prepayment fee (as a percent)	3.00%
After first anniversary of closing date
Term Loans
Prepayment fee (as a percent)	2.00%
After second anniversary to maturity date
Term Loans
Prepayment fee (as a percent)	1.00%
LIBOR
Term Loans
Floating interest rate	7.45%

[1] Derived from the audited consolidated financial statements included in the Company’s Annual Report on Form 10K for the year ended December 31, 2018.