CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenues:
Products	$ 433,012	$ 685,364	$ 773,205
Services	105,719	158,946	157,752
Total revenues	538,731	844,310	930,957
Cost of sales:
Products	268,405	382,925	428,125
Services	59,999	76,361	85,402
Total cost of sales	328,404	459,286	513,527
Selling, general and administrative	53,143	88,044	92,762
Engineering and product development	44,325	48,145	45,920
Total costs and expenses	425,872	595,475	652,209
Operating income	112,859	248,835	278,748
Interest income	3,037	948	667
Interest expense	(28)	(12)	(35)
Income before income taxes	115,868	249,771	279,380
Income tax provision	22,647	57,763	70,668
Net income	$ 93,221	$ 192,008	$ 208,712
Earnings per common share:
Basic (in dollars per share)	$ 2.48	$ 5.00	$ 5.22
Diluted (in dollars per share)	$ 2.47	$ 4.98	$ 5.19
Weighted average common shares outstanding:
Basic (in shares)	37,537	38,364	39,964
Diluted (in shares)	37,667	38,531	40,190