Accrued Expenses (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Dec. 31, 2020
Accrued Expenses
Accrued employee compensation and benefits			$ 786	$ 2,069
Accrued warranty	$ 1,265	$ 907	1,086	1,265
Accrued professional fees			729	975
Accrued other			410	729
Accrued Liabilities, Current, Total			$ 3,011	$ 5,038
Changes in product warranty obligation
Accrual balance at beginning of period	1,265	968
Provision for new warranties	198	107
Settlements and adjustments made during the period	(377)	(168)
Accrual balance at end of period	$ 1,086	$ 907