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, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	$ 1,008,822	$ 912,380	$ 844,748
Long-lived assets	268,041	246,097	224,190
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	726,582	663,600	615,028
Long-lived assets	191,958	171,048	166,707
United Kingdom
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	51,043	44,416	45,184
Long-lived assets	19,270	18,948	16,254
France
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	90,956	86,443	79,070
Long-lived assets	18,650	19,324	16,772
Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	62,077	52,332	48,357
Long-lived assets	21,647	24,302	19,435
Australia
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	9,055	12,778	13,580
Long-lived assets	815	917	1,401
Brazil
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	16,829	9,321	2,665
Long-lived assets	15,701	11,558	3,621
Other
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales	$ 52,280	$ 43,490	$ 40,864