International Operations and Geographic Information (Schedule of Geographic Net Sales and Location of Long-lived assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	$ 912,380	$ 844,748	$ 879,577
Long-lived assets	246,097	224,190	239,301
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	663,600	615,028	635,923
Long-lived assets	171,048	166,707	174,811
United Kingdom
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	44,416	45,184	59,621
Long-lived assets	18,948	16,254	20,338
France
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	86,443	79,070	80,762
Long-lived assets	19,324	16,772	18,755
Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	52,332	48,357	44,388
Long-lived assets	24,302	19,435	21,466
Australia
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	12,778	13,580	13,801
Long-lived assets	917	1,401	1,189
Other
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	52,811	43,529	45,082
Brazil
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	$ 11,558	$ 3,621	$ 2,742