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Term Loan (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Aug. 31, 2018
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Interest expense	$ 363	$ 678	$ 1,086	$ 1,037
Term Loan [Member]
Debt Instrument [Line Items]
Interest expense	363	678	1,086	1,037
Final payment fee			1,008
Silicon Valley Bank [Member] \| Term Loan [Member]
Debt Instrument [Line Items]
Amortization of debt discount and accretion of final payment fee	$ 133	$ (8)	$ 389	$ 156
Debt instrument, frequency periodic payment, interest			monthly
Silicon Valley Bank [Member] \| Term Loan [Member] \| Loan Agreement [Member]
Debt Instrument [Line Items]
Aggregate principal amount of debt instrument						$ 15,500
Warrants outstanding to purchase common stock	40,000		40,000
Warrants exercise price per common share	$ 9.79		$ 9.79
Silicon Valley Bank [Member] \| Term Loan [Member] \| Loan Agreement [Member] \| Initial Tranche [Member]
Debt Instrument [Line Items]
Effective interest rate on initial tranche of debt instrument	9.06%		9.06%		9.53%