Property, Plant and Equipment - Schedule of Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Property, plant and equipment
Property, plant and equipment, gross	$ 607,081	$ 587,458
Less: accumulated depreciation	(287,077)	(277,471)
Total property, plant and equipment, net	320,004	309,987
Land
Property, plant and equipment
Property, plant and equipment, gross	6,560	6,486
Building and Improvements
Property, plant and equipment
Property, plant and equipment, gross	170,289	157,053
Furniture, Fixtures and Equipment
Property, plant and equipment
Property, plant and equipment, gross	320,882	314,831
Leasehold Improvements
Property, plant and equipment
Property, plant and equipment, gross	20,105	20,105
Construction in Progress
Property, plant and equipment
Property, plant and equipment, gross	$ 89,245	$ 88,983