Condensed Consolidated Statements of Income (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Revenues:
Products	$ 157,790	$ 198,827	$ 521,413	$ 560,742
Services	43,612	42,923	121,267	115,396
Total revenues	201,402	241,750	642,680	676,138
Cost and expenses:
Products	88,923	113,642	293,279	309,181
Services	19,209	21,608	57,655	61,849
Total cost of sales	108,132	135,250	350,934	371,030
Selling, general and administrative	17,280	20,845	67,871	70,300
Engineering and product development	11,735	12,663	35,348	34,295
Total costs and expenses	137,147	168,758	454,153	475,625
Operating income	64,255	72,992	188,527	200,513
Interest income	345	206	559	555
Interest expense	(4)	(3)	(10)	(15)
Income before income taxes	64,596	73,195	189,076	201,053
Income tax provision	13,819	17,512	45,422	51,428
Net income	$ 50,777	$ 55,683	$ 143,654	$ 149,625
Earnings per common share:
Basic	$ 1.32	$ 1.41	$ 3.72	$ 3.72
Diluted	$ 1.32	$ 1.40	$ 3.70	$ 3.70
Weighted average common shares outstanding:
Basic	38,347	39,630	38,601	40,208
Diluted	38,548	39,880	38,789	40,444