Inventories (Schedule Of Inventories) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Inventories:
Raw materials and supplies	$ 55,492		$ 55,492		$ 54,469
Work in process	65,349		65,349		52,379
Finished goods	43,727		43,727		49,263
Total	164,568		164,568		$ 156,111
Inventory write-downs	$ 264	$ 4,898	$ 1,773	$ 19,523