CONSOLIDATED CONDENSED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Income Statement [Abstract]
NET SALES	$ 219,453	$ 223,217	$ 425,634	$ 433,203
COST OF GOODS SOLD	150,016	152,913	292,284	301,318
Gross profit	69,437	70,304	133,350	131,885
OPERATING EXPENSES
Selling, general and administrative	31,882	33,291	63,613	65,621
Research and development	13,590	12,781	26,899	25,701
Other operating expenses	1,967	1,089	3,937	3,077
Total operating expenses	47,439	47,161	94,449	94,399
Income from operations	21,998	23,143	38,901	37,486
OTHER INCOME (EXPENSES)	(741)	359	(1,681)	(991)
Income before income taxes and noncontrolling interest	21,257	23,502	37,220	36,495
INCOME TAX PROVISION	5,399	5,651	9,586	8,198
NET INCOME	15,858	17,851	27,634	28,297
Less: NET INCOME attributable to noncontrolling interest	(780)	(466)	(1,424)	(710)
NET INCOME attributable to common stockholders	$ 15,078	$ 17,385	$ 26,210	$ 27,587
EARNINGS PER SHARE attributable to common stockholders
Basic	$ 0.31	$ 0.37	$ 0.55	$ 0.59
Diluted	$ 0.31	$ 0.36	$ 0.53	$ 0.57
Number of shares used in computation
Basic	48,076	46,889	47,872	46,794
Diluted	49,250	48,423	49,091	48,223