CONSOLIDATED STATEMENTS OF INCOME (LOSS) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues:
Products	$ 351,132,000	$ 433,012,000	$ 685,364,000
Services	104,337,000	105,719,000	158,946,000
Total revenues	455,469,000	538,731,000	844,310,000
Cost of sales:
Products	246,005,000	268,405,000	382,925,000
Services	59,389,000	59,999,000	76,361,000
Total cost of sales	305,394,000	328,404,000	459,286,000
Selling, general and administrative	116,083,000	53,143,000	88,044,000
Engineering and product development	42,160,000	44,325,000	48,145,000
Impairment and other charges	60,968,000	0	0
Total costs and expenses	524,605,000	425,872,000	595,475,000
Operating income (loss)	(69,136,000)	112,859,000	248,835,000
Interest income	3,564,000	3,037,000	948,000
Interest expense	(72,000)	(28,000)	(12,000)
Income (loss) before taxes	(65,644,000)	115,868,000	249,771,000
Income tax (benefit) provision	34,995,000	22,647,000	57,763,000
Net income (loss)	$ (100,639,000)	$ 93,221,000	$ 192,008,000
Earnings per common share:
Basic (in dollars per share)	$ (2.69)	$ 2.48	$ 5.00
Diluted (in dollars per share)	$ (2.69)	$ 2.47	$ 4.98
Weighted average common shares outstanding:
Basic (in shares)	37,457,413	37,537,000	38,364,000
Diluted (in shares)	37,457,413	37,667,000	38,531,000