Product warranty liabilities are included in “Accrued liabilities” in the Condensed Consolidated Balance Sheets. Below is a reconciliation of changes in product warranty liabilities: (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020
Commitments and Contingencies Disclosure [Abstract]
Balance, January 1	$ 22	$ 16
Accruals for warranties issued	12	18
Accruals for pre-existing warranties
Settlements made (in cash or in kind)	(5)	(4)
Balance, end of period	$ 29	$ 30