CONSOLIDATED CONDENSED STATEMENTS OF OPERATIONS (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Income Statement [Abstract]
NET SALES	$ 206,182	$ 209,986
COST OF GOODS SOLD	142,269	148,405
Gross profit	63,913	61,581
OPERATING EXPENSES
Selling, general and administrative	31,731	32,330
Research and development	13,309	12,920
Other operating expenses	1,970	1,988
Total operating expenses	47,010	47,238
Income from operations	16,903	14,343
OTHER INCOME (EXPENSES)	(939)	(1,350)
Income before income taxes and noncontrolling interest	15,964	12,993
INCOME TAX PROVISION	4,187	2,547
NET INCOME	11,777	10,446
Less: NET INCOME attributable to noncontrolling interest	(645)	(244)
NET INCOME attributable to common stockholders	$ 11,132	$ 10,202
EARNINGS PER SHARE attributable to common stockholders
Basic	$ 0.23	$ 0.22
Diluted	$ 0.23	$ 0.21
Number of shares used in computation
Basic	47,667	46,699
Diluted	48,978	47,996