CONSOLIDATED STATEMENTS OF INCOME (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Statement [Abstract]
Net sales	$ 256,225	$ 215,571	$ 486,206	$ 414,848
Cost of goods sold	164,047	152,393	312,377	275,642
Gross profit	92,178	63,178	173,829	139,206
Selling, general, and administrative expenses	36,707	41,314	78,637	81,721
Technical and research expenses	10,198	9,973	20,515	20,235
Restructuring expenses, net	2,589	2,036	11,162	4,717
Operating income	42,684	9,855	63,515	32,533
Interest expense, net	4,621	4,285	8,909	8,613
Other expense, net	726	2,558	2,178	3,384
Income before income taxes	37,337	3,012	52,428	20,536
Income tax expense	7,031	1,779	11,640	8,329
Net income	30,306	1,233	40,788	12,207
Net income/(loss) attributable to the noncontrolling interest	(59)	116	178	251
Net income attributable to the Company	$ 30,365	$ 1,117	$ 40,610	$ 11,956
Earnings per share attributable to Company shareholders - Basic	$ 0.94	$ 0.03	$ 1.26	$ 0.37
Earnings per share attributable to Company shareholders - Diluted	$ 0.94	$ 0.03	$ 1.26	$ 0.37
Shares of the Company used in computing earnings per share:
Basic	32,257	32,166	32,239	32,147
Diluted	32,273	32,200	32,255	32,182
Dividends declared per share, Class A and Class B	$ 0.17	$ 0.17	$ 0.34	$ 0.34