Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Statement [Abstract]
Net sales	$ 228,483	$ 214,623	$ 706,191	$ 653,415
Cost of sales	156,543	145,610	481,770	446,109
Gross profit	71,940	69,013	224,421	207,306
Operating expenses:
Selling, general and administrative expenses	44,860	41,009	135,372	123,012
Research and development expenses	5,733	6,051	18,464	18,434
Restructuring and consolidation costs	610	680	2,119	3,776
Total operating expenses	51,203	47,740	155,955	145,222
Income from operations	20,737	21,273	68,466	62,084
Other non-operating income and expense:
Loss on settlement of pension plan			5,086
Interest expense, net	1,958	1,811	5,857	5,547
Other non-operating expense/(income), net	644	696	216	30
Loss on extinguishment of convertible debt				1,797
Total other non-operating (income) expense, net	2,602	2,507	11,159	7,374
Income before income taxes	18,135	18,766	57,307	54,710
Provision for income taxes	5,822	5,489	16,986	15,723
Net income	$ 12,313	$ 13,277	$ 40,321	$ 38,987
Weighted average shares, basic	29,010	29,008	29,101	28,912
Weighted average shares, diluted	29,049	29,074	29,178	29,001
Net income per share:
Basic net income	$ 0.42	$ 0.46	$ 1.39	$ 1.35
Diluted net income	0.42	0.46	1.38	1.34
Cash dividend declared	$ 0.17	$ 0.17	$ 0.51	$ 0.49