Summary of Significant Accounting Policies - PPE (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, plant and equipment
Depreciation and amortization expense	$ 7,613	$ 7,183	$ 6,146
Repairs and maintenance expenses	$ 6,032	$ 5,222	$ 5,060
Land improvements and buildings | Minimum
Property, plant and equipment
Estimated useful lives	15 years
Land improvements and buildings | Maximum
Property, plant and equipment
Estimated useful lives	40 years
Leasehold Improvements | Minimum
Property, plant and equipment
Estimated useful lives	12 years
Machinery and equipment | Minimum
Property, plant and equipment
Estimated useful lives	3 years
Machinery and equipment | Maximum
Property, plant and equipment
Estimated useful lives	20 years
Furniture and fixtures | Minimum
Property, plant and equipment
Estimated useful lives	3 years
Furniture and fixtures | Maximum
Property, plant and equipment
Estimated useful lives	12 years
Mobile equipment and other | Minimum
Property, plant and equipment
Estimated useful lives	3 years
Mobile equipment and other | Maximum
Property, plant and equipment
Estimated useful lives	10 years