Consolidated Income Statements (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]
Gross sales	$ 147,214	$ 134,487	$ 286,344	$ 238,198
Commissions, allowances and rebates	192	649	401	1,243
Net sales	147,022	133,838	285,943	236,955
Other revenues, net	5,024	716	7,200	2,605
Net revenue	152,046	134,554	293,143	239,560
Cost of goods sold	87,254	76,995	177,496	135,126
Gross profit	64,792	57,559	115,647	104,434
Operating expenses:
Selling, general and administrative expenses	16,007	18,120	32,862	33,511
Research and development expenses	4,133	4,467	7,752	8,357
Total operating expenses	20,140	22,587	40,614	41,868
Operating profit	44,652	34,972	75,033	62,566
Other expenses/(income):
Interest expense, net	17	388	99	654
Unrealized gain on investment in equity securities	(5,146)		(5,146)
Other expenses, net	181	286	445	687
Income before income taxes	49,600	34,298	79,635	61,225
Provision for income taxes	8,748	9,174	14,534	14,986
Income from continuing operations	40,852	25,124	65,101	46,239
Loss from discontinued operations, net of tax	(433)	(94)	(624)	(1,344)
Net income	$ 40,419	$ 25,030	$ 64,477	$ 44,895
Basic earnings/(loss) per share of common stock:
Income from continuing operations	$ 1.23	$ 0.77	$ 1.97	$ 1.42
Loss from discontinued operations, net of tax	(0.01)	0.00	(0.02)	(0.04)
Net income	1.22	0.77	1.95	1.38
Diluted earnings/(loss) per share of common stock:
Income from continuing operations	1.21	0.75	1.94	1.38
Loss from discontinued operations, net of tax	(0.01)	0.00	(0.02)	(0.04)
Net income	$ 1.20	$ 0.75	$ 1.92	$ 1.34
Weighted average shares outstanding:
Basic	33,085	32,629	32,990	32,542
Effect of dilutive stock based compensation	557	840	628	874
Diluted	33,642	33,469	33,618	33,416