Basis of Presentation (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Consolidated Balance Sheet Line Item
Other current assets	$ 13,453	$ 10,638
Deferred income taxes	37,850	45,839
Accrued liabilities	(43,991)	(45,708)
Post retirement obligations	(6,823)	(7,006)
Other long-term obligations	$ (6,709)	$ (5,580)