CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Statement [Abstract]
Net sales	[1]	$ 641,443	$ 610,911	$ 537,482
Cost of sales		406,081	376,158	348,945
Gross margin		235,362	234,753	188,537
Selling, general and administrative expenses		131,463	125,244	106,398
Research and development expenses		27,644	22,878	21,646
Restructuring and impairment charges		0	5,390	10,376
Operating income		76,255	81,241	50,117
Equity income in unconsolidated joint ventures		2,890	4,123	4,326
Interest income (expense), net		(4,480)	(2,946)	(3,481)
Other income (expense), net		(8,492)	(1,194)	(1,240)
Income before income taxes		66,173	81,224	49,722
Income tax expense		19,853	27,812	11,519
Income from continuing operations		46,320	53,412	38,203
Income from discontinued operations, net of income taxes		0	0	102
Net income		$ 46,320	$ 53,412	$ 38,305
Basic earnings per share:
Income from continuing operations (in dollars per share)		$ 2.52	$ 2.94	$ 2.22
Income from discontinued operations (in dollars per share)		0.00	0.00	0.01
Net income (in dollars per share)		2.52	2.94	2.23
Diluted earnings per share:
Income from continuing operations (in dollars per share)		2.48	2.86	2.15
Income from discontinued operations (in dollars per share)		0.00	0.00	0.01
Net income (in dollars per share)		$ 2.48	$ 2.86	$ 2.16
Shares used in computing:
Basic earnings per share (in shares)		18,371,000	18,177,000	17,198,000
Diluted earnings per share (in shares)		18,680,000	18,698,000	17,768,000

[1] Net sales are allocated to countries based on the location of the customer.