Business Segments (Revenue by Geography) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues from External Customers and Long-Lived Assets
Net Sales	$ 536,377	$ 483,514	$ 624,523
United States
Revenues from External Customers and Long-Lived Assets
Net Sales	431,868	390,930	522,404
Canada
Revenues from External Customers and Long-Lived Assets
Net Sales	38,859	30,644	40,545
United Kingdom
Revenues from External Customers and Long-Lived Assets
Net Sales	37,237	37,188	26,817
Other
Revenues from External Customers and Long-Lived Assets
Net Sales	$ 28,413	$ 24,752	$ 34,757