CONSOLIDATED STATEMENT OF INCOME (LOSS) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Income Statement [Abstract]
Net sales	$ 537,482	[1]	$ 498,761	[1]	$ 548,341	[1]
Cost of sales	349,782		340,015		369,356
Gross margin	187,700		158,746		178,985
Selling and administrative expenses	106,398		99,689		103,532
Research and development expenses	21,646		19,311		21,530
Restructuring and impairment charges	10,376		14,082		441
Operating income (loss)	49,280		25,664		53,482
Equity income in unconsolidated joint ventures	4,326		4,743		5,451
Other income (expense), net	(1,240)		(208)		1,942
Realized investment gain (loss):
Increase (decrease) in fair value of investments	0		(522)		(14)
Less: Portion reclassified to/from other comprehensive income	0		2,723		182
Net realized gain (loss)	0		(3,245)		(196)
Interest income (expense), net	(3,481)		(4,304)		(4,911)
Income (loss) before income tax expense (benefit)	48,885		22,650		55,768
Income tax expense (benefit)	11,226		(46,484)		11,518
Income (loss) from continuing operations	37,659		69,134		44,250
Income (loss) from discontinued operations, net of income taxes	102		(449)		(7,195)
Net income (loss)	$ 37,761		$ 68,685		$ 37,055
Basic net income (loss) per share:
Income (loss) from continuing operations (in dollars per share)	$ 2.19		$ 4.21		$ 2.76
Income (loss) from discontinued operations (in dollars per share)	$ 0.01		$ (0.03)		$ (0.45)
Net income (loss) (in dollars per share)	$ 2.20		$ 4.18		$ 2.31
Diluted net income (loss) per share:
Income (loss) from continuing operations (in dollars per share)	$ 2.12		$ 4.07		$ 2.64
Income (loss) from discontinued operations (in dollars per share)	$ 0.01		$ (0.03)		$ (0.43)
Net income (loss) (in dollars per share)	$ 2.13		$ 4.04		$ 2.21
Shares used in computing:
Basic net income per share (shares)	17,197,840		16,426,209		16,035,882
Diluted net income per share (shares)	17,768,075		16,991,158		16,737,711

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