Property, Plant and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment
Property, plant and equipment - gross	$ 189,076	$ 185,495
Less accumulated depreciation and amortization, including accumulated amortization of capitalized leases	92,980	81,522
Total property, plant and equipment, net	96,096	103,973
Land
Property, Plant and Equipment
Property, plant and equipment - gross	14,869	14,826
Improvements to land and leaseholds
Property, Plant and Equipment
Property, plant and equipment - gross	17,415	17,408
Buildings
Property, Plant and Equipment
Property, plant and equipment - gross	34,929	33,910
Machinery and equipment, including equipment under capitalized leases
Property, Plant and Equipment
Property, plant and equipment - gross	120,806	118,060
Construction in progress
Property, Plant and Equipment
Property, plant and equipment - gross	$ 1,057	$ 1,291