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Subsequent Events (Details) - USD ($) $ in Thousands		1 Months Ended
Subsequent Events (Details) - USD ($) $ in Thousands	Jan. 28, 2019	Jul. 31, 2017	Jan. 01, 2019	Dec. 31, 2018	Dec. 31, 2017
Subsequent Events
Term loan					$ 8,683
A&R 2015 Plan
Subsequent Events
Common stock reserved for issuance (in shares)				415,077	0
A&R 2015 Plan \| Subsequent Event
Subsequent Events
Common stock reserved for issuance (in shares)			501,001
Term Loan
Subsequent Events
Debt discount amortized as interest expenses		$ 100
Term Loan \| Subsequent Event
Subsequent Events
Term loan	$ 8,900
Debt discount amortized as interest expenses	800
SVB \| Term Loan \| Subsequent Event
Subsequent Events
Payment fee due	$ 1,000