Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Property, plant and equipment
Land	$ 7,766	$ 8,287
Building improvements	655,565	654,585
Capitalized leases for machinery, equipment and buildings	54,968	30,648
Property, plant and equipment, gross	718,299	693,520
Accumulated depreciation and amortization	(517,390)	(514,509)
Property Plant and Equipment Net before Construction in Progress	200,909	179,011
Construction in Progress	16,492	16,988
Property, plant and equipment, net	$ 217,401	$ 195,999