Quarterly Financial Data (Schedule of Quarterly Data) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	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, 2016	Dec. 31, 2015	Dec. 31, 2014
Net sales	$ 213,000	$ 191,300	$ 203,200	$ 172,300	$ 177,500	$ 178,800	$ 172,300	$ 181,300	$ 191,600	$ 179,900	$ 193,500	$ 180,300	$ 779,839	$ 709,868	$ 745,345
Gross profit	77,400	72,400	78,300	72,500	71,700	75,700	54,600	76,700	72,900	68,600	75,300	74,800	300,568	278,686	291,635
Net income/(loss) attributable to the Company	$ 15,800	$ 13,100	$ 10,400	$ 13,500	$ 37,600	$ 9,700	$ (2,200)	$ 12,200	$ 8,000	$ 11,800	$ 11,200	$ 10,600	$ 52,733	$ 57,279	$ 41,569
Basic earnings per share	$ 0.49	$ 0.41	$ 0.32	$ 0.42	$ 1.18	$ 0.30	$ (0.07)	$ 0.38	$ 0.26	$ 0.37	$ 0.35	$ 0.33	$ 1.64	$ 1.79	$ 1.31
Diluted earnings per share	0.49	0.41	0.32	0.42	1.18	0.30	(0.07)	0.38	0.25	0.37	0.35	0.33	1.64	1.79	1.30
Cash dividends per share	0.17	0.17	0.17	0.17	0.17	0.17	0.17	0.16	0.16	0.16	0.16	0.15	$ 0.68	$ 0.67	$ 0.63
Minimum [Member]
Class A Common Stock prices:	38.65	38.92	37.27	31.43	28.19	28.28	39.15	34.13	32.46	34.04	33.67	32.85
Maximum [Member]
Class A Common Stock prices:	$ 49.25	$ 43.78	$ 41.31	$ 38.21	$ 39.25	$ 40.21	$ 41.15	$ 40.31	$ 38.15	$ 38.53	$ 38.01	$ 37.59