Inventories - Allowance (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Inventory Valuation Reserves [Roll Forward]
Balance, beginning of period	$ 2,365	$ 1,567	$ 2,644	$ 1,210
Provisions for excess and obsolete inventories	81	796	(193)	1,153
Inventories written off	(73)	(13)	(78)	(13)
Balance, end of period	$ 2,373	$ 2,350	$ 2,373	$ 2,350