Inventories (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Inventory Disclosure [Abstract]
Inventory Charges, net (E&O and APC)	$ 661	$ 501
Inventory, Net [Abstract]
Raw materials	24,037		$ 23,269
Finished goods	3,766		4,012
Inventory, Gross	27,803		27,281
Less: inventory valuation allowance	(23,204)		(23,016)
Inventories, net	$ 4,599		$ 4,265
Age of consignment inventory purchased as a result of forecasted demand	180 days
Inventory Charges, Inventory Valuation, Deposit And Adverse Purchase Commitment Liability	$ (332)	702
Adverse Purchase Commitments	$ (993)	$ 201