Property, Plant and Equipment (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Property, plant and equipment
Land	$ 1,764	$ 1,764
Building improvements	870,251	855,318
Capitalized leases for machinery, equipment and buildings	9,015	16,133
Property, plant and equipment, gross	881,030	873,215
Accumulated depreciation and amortization	(411,446)	(395,520)
Property Plant and Equipment Net before Construction in Progress	469,584	477,695
Construction in Progress	7,253	8,578
Property, plant and equipment, net	$ 476,837	$ 486,273