Inventories - Reserve Rollforward (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Inventory, Reserve [Roll Forward]
Beginning Balance	$ (3,645)	$ (4,212)
Provision (accrual)	112	(814)
Reduction due to sold inventory	167	845
Write-off for disposed inventory	40	536
Reserves for excess, obsolete, and slow-moving inventories	$ (3,326)	$ (3,645)