International Operations and Geographic Information (Schedule of Selected Financial Information for International Operations) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Net sales	$ 912,380	$ 844,748	$ 879,577
Income from operations	88,738	67,620	66,528
Identifiable assets	639,671	552,776
Non-US
Segment Reporting Information [Line Items]
Net sales	254,144	232,291	243,108
Income from operations	23,110	18,544	9,682
Income before income taxes	22,476	18,720	15,840
Identifiable assets	$ 227,758	$ 167,990	$ 194,839