CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Statement [Abstract]
Net sales	$ 110,954	$ 80,915	$ 211,089	$ 148,228
Cost of products sold	68,881	54,140	132,611	98,700
Gross profit	42,073	26,775	78,478	49,528
Costs and expenses:
General and administrative expenses	9,460	9,743	18,628	17,920
Selling and distribution expenses	7,239	5,795	13,548	11,007
Amortization of purchased intangible assets	397	791	795	1,596
Restructuring expenses, net	324	217	402	361
Anti-dumping duty penalties	0	0	0	3,103
Total costs and expenses	17,420	16,546	33,373	33,987
Operating income	24,653	10,229	45,105	15,541
Other income (expense):
Other income (expense), net	343	(327)	322	(704)
Interest expense, net	(409)	(136)	(782)	(601)
Income before income taxes	24,587	9,766	44,645	14,236
Income tax provision	7,343	3,394	12,231	3,944
Net income	$ 17,244	$ 6,372	$ 32,414	$ 10,292
Net income per share
Basic (in dollars per share)	$ 1.17	$ 0.43	$ 2.20	$ 0.69
Diluted (in dollars per share)	$ 1.15	$ 0.43	$ 2.17	$ 0.69
Weighted-average shares outstanding:
Basic (in shares)	14,647,019	14,534,016	14,624,718	14,491,569
Diluted (in shares)	14,899,987	14,534,016	14,849,816	14,491,569
Dividends declared per common share (in dollars per share)	$ 0.02	$ 0.02	$ 0.04	$ 0.04