Quarterly Financial Data (Schedule of Quarterly Data) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Net sales	$ 177,500	$ 178,800	$ 172,300	$ 181,300	$ 191,600	$ 179,900	$ 193,500	$ 180,300	$ 189,600	$ 183,100	$ 198,000	$ 186,700	$ 709,868	$ 745,345	$ 757,414
Gross profit	71,700	75,700	54,600	76,700	72,900	68,600	75,300	74,800	72,400	68,000	77,400	72,800	278,686	291,635	290,554
Net income/(loss) attributable to the Company	$ 37,600	$ 9,700	$ (2,200)	$ 12,200	$ 8,000	$ 11,800	$ 11,200	$ 10,600	$ 8,700	$ 4,700	$ (7,400)	$ 11,500	$ 57,279	$ 41,569	$ 17,517
Basic earnings per share	$ 1.18	$ 0.30	$ (0.07)	$ 0.38	$ 0.26	$ 0.37	$ 0.35	$ 0.33	$ 0.27	$ 0.15	$ (0.23)	$ 0.36	$ 1.79	$ 1.31	$ 0.55
Diluted earnings per share	1.18	0.30	(0.07)	0.38	0.25	0.37	0.35	0.33	0.27	0.15	(0.23)	0.36	$ 1.79	$ 1.30	$ 0.55
Cash dividends per share	0.17	0.17	0.17	0.16	0.16	0.16	0.16	0.15	0.15	0.15	0.15	0.14
Maximum [Member]
Class A Common Stock prices:	39.25	40.21	41.15	40.31	38.15	38.53	38.01	37.59	37.25	36.53	33.90	29.87
Minimum [Member]
Class A Common Stock prices:	$ 28.19	$ 28.28	$ 39.15	$ 34.13	$ 32.46	$ 34.04	$ 33.67	$ 32.85	$ 33.81	$ 32.27	$ 27.48	$ 23.21