Stock Incentive Plans - Stock option activity (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Shares
Outstanding, beginning of period (in shares)	785,832	785,832
Granted (in shares)		666,200
Exercised (in shares)		(7,000)
Cancelled or forfeited (in shares)		(76,884)
Expired (in shares)		(481)
Outstanding, end of period (in shares)		1,367,667	785,832
Vested and exercisable (in shares)		504,171
Weighted-Average Exercise Price
Outstanding, beginning of period (in dollars per share)	$ 16.48	$ 16.48
Granted (in dollars per share)		5.69
Exercised (in dollars per share)		4.39
Cancelled or forfeited (in dollars per share)		14.65
Expired (in dollars per share)		32.10
Outstanding at end of year (in dollars per share)		11.38	$ 16.48
Vested and Exercisable (in dollars per share)		$ 21.22
Weighted Average Remaining Contractual Term (years)
Outstanding	8 years 1 month 17 days		8 years 1 month 17 days
Vested and Exercisable	6 years 8 months 5 days
Aggregate Intrinsic Value
Outstanding			$ 470
Stock options
Shares
Exercised (in shares)			0
Additional disclosures
Intrinsic value of options exercised		$ 29
Weighted average grant date fair value of options granted (in dollars per share)		$ 3.81	$ 3.25
Unrecognized compensation expense related to unvested stock option awards		$ 2,700
Weighted-average amortization period over which cost is expected to be recognized		2 years 8 months 12 days

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Gross number of share options (or share units) granted during the period.

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Number of fully vested and expected to vest exercisable options that may be converted into shares under option plan. Includes, but is not limited to, unvested options for which requisite service period has not been rendered but that are expected to vest based on achievement of performance condition, if forfeitures are recognized when they occur.

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