Inventories - Allowance (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Inventory Valuation Reserves [Roll Forward]
Balance, beginning of period	$ 2,373	$ 2,350	$ 2,644	$ 1,210
Provisions for excess and obsolete inventories	1,969	(150)	1,776	1,003
Inventories written off	(230)	0	(308)	(13)
Balance, end of period	$ 4,112	$ 2,200	$ 4,112	$ 2,200