Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Net sales	$ 863,717	$ 779,839	$ 709,868
Cost of goods sold	567,937	479,271	431,182
Gross profit	295,780	300,568	278,686
Selling, general and administrative expenses	164,964	160,112	146,192
Technical and research expenses	41,174	40,304	44,753
Restructuring expenses, net	13,491	8,376	23,846
Operating income	76,151	91,776	63,895
Interest income	(1,511)	(2,077)	(1,857)
Interest expense	18,602	15,541	11,841
Other expense, net	4,352	46	2,433
Income before income taxes	54,708	78,266	51,478
Income tax expense/(benefit)	22,123	25,454	(5,787)
Net income	32,585	52,812	57,265
Net (loss)/income attributable to the noncontrolling interest	(526)	79	(14)
Net income attributable to the Company	$ 33,111	$ 52,733	$ 57,279
Earnings per share attributable to Company shareholders - Basic	$ 1.03	$ 1.64	$ 1.79
Earnings per share attributable to Company shareholders - Diluted	1.03	1.64	1.79
Dividends declared per share, Class A and Class B	$ 0.68	$ 0.68	$ 0.67