Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Property, plant and equipment
Land	$ 7,777	$ 8,287
Building improvements	653,966	654,585
Capitalized leases for machinery, equipment and buildings	54,968	30,648
Property, plant and equipment, gross	716,711	693,520
Accumulated depreciation and amortization	(510,070)	(514,509)
Property Plant and Equipment Net before Construction in Progress	206,641	179,011
Construction in Progress	10,704	16,988
Property, plant and equipment, net	$ 217,345	$ 195,999