Basis of Presentation and Significant Accounting Policies - Supplemental cash flow information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Capital expenditures financed by accounts payable	$ 59	$ 667	$ 434
Capital Lease Obligations Incurred	0	0	873
Property, plant and equipment subject to build-to-suit lease	0	13,735	0
Cash paid during the year for:
Interest	31,404	32,934	32,278
Income taxes	2,434	1,980	1,800
Cash received during the year for:
Income tax refunds	$ 500	$ 1,798	$ 2,284