Inventories - Allowance (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Inventory Valuation Reserves [Roll Forward]
Balance, beginning of period	$ 2,726	$ 2,373	$ 3,261	$ 2,644
Provisions for excess and obsolete inventories	86	1,969	378	1,776
Inventories written off	(520)	(230)	(1,347)	(308)
Balance, end of period	$ 2,292	$ 4,112	$ 2,292	$ 4,112