Property and Equipment - Components of Property and Equipment (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Components of Property, Plant and Equipment
Property and equipment	$ 113,634	$ 112,852
Less accumulated depreciation	(40,526)	(39,019)
Property and equipment, net	73,108	73,833
Land
Components of Property, Plant and Equipment
Property and equipment	6,724	6,724
Buildings and leasehold improvements
Components of Property, Plant and Equipment
Property and equipment	43,611	43,899
Machinery and equipment
Components of Property, Plant and Equipment
Property and equipment	41,506	41,548
Fixed assets in progress
Components of Property, Plant and Equipment
Property and equipment	5,605	4,298
Furniture and fixtures
Components of Property, Plant and Equipment
Property and equipment	1,719	2,002
Transportation equipment
Components of Property, Plant and Equipment
Property and equipment	2,364	2,200
Computer equipment and software
Components of Property, Plant and Equipment
Property and equipment	$ 12,105	$ 12,181