Condensed Consolidated Statements of Operations - 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	$ 237,323	$ 223,357	$ 477,708	$ 438,792
Cost of sales	159,068	151,231	325,227	300,499
Gross profit	78,255	72,126	152,481	138,293
Operating expenses:
Selling, general and administrative expenses	43,382	41,619	90,512	82,003
Research and development expenses	6,258	6,160	12,731	12,383
Restructuring and consolidation costs	566	1,198	1,509	3,096
Total operating expenses	50,206	48,977	104,752	97,482
Income from operations	28,049	23,149	47,729	40,811
Other non-operating income and expense:
Loss on settlement of pension plan			5,086
Interest expense, net	2,065	2,031	3,899	3,736
Other non-operating expense/(income), net	(282)	(136)	(428)	(666)
Loss on extinguishment of convertible debt				1,797
Total other non-operating (income) expense, net	1,783	1,895	8,557	4,867
Income before income taxes	26,266	21,254	39,172	35,944
Provision for income taxes	7,259	5,870	11,164	10,234
Net income	$ 19,007	$ 15,384	$ 28,008	$ 25,710
Weighted average shares, basic	28,979	28,978	29,085	28,873
Weighted average shares, diluted	29,089	29,114	29,245	29,042
Net income per share:
Basic net income	$ 0.66	$ 0.53	$ 0.96	$ 0.89
Diluted net income	0.65	0.53	0.96	0.89
Cash dividend declared	$ 0.17	$ 0.17	$ 0.34	$ 0.32