Other Balance Sheet Captions - Components of Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Components of Property and Equipment [Abstract]
Land, buildings, and improvements	$ 72,223	$ 67,487
Transportation equipment	3,286	3,253
Machinery and equipment	175,371	164,871
Construction in progress	16,408	10,608
Property, plant, and equipment, at cost	267,288	246,219
Less accumulated depreciation and amortization	(164,237)	(153,428)
Property, plant, and equipment, net	$ 103,051	$ 92,791