CONSOLIDATED STATEMENTS OF INCOME (LOSS) - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues:
Revenues from products and services	$ 334,411	$ 375,297
Leasing	30,562	39,509	$ 47,160
Total revenues	364,973	414,806	384,626
Cost of sales:
Total cost of sales	269,698	295,007	293,573
Selling, general and administrative	95,057	98,412	102,097
Engineering and product development	18,920	17,329	20,297
Impairments	7,719		38,559
Restructuring and other charges	35,380	4,396	60,043
Gain on sale of assets	(587)	(1,511)	(6,198)
Foreign currency transaction (gains) and losses	2,345	(1,630)	(1,007)
Total costs and expenses	428,532	412,003	507,364
Operating income (loss)	(63,559)	2,803	(122,738)
Interest income	2,131	7,940	8,040
Interest expense	(621)	(314)	(291)
Income (loss) before income taxes	(62,049)	10,429	(114,989)
Income tax provision (benefit)	(31,281)	8,709	(19,294)
Net income (loss)	$ (30,768)	$ 1,720	$ (95,695)
Income (loss) per common share:
Basic (in dollars per share)	$ (0.87)	$ 0.05	$ (2.58)
Diluted (in dollars per share)	$ (0.87)	$ 0.05	$ (2.58)
Weighted average common shares outstanding:
Basic (in shares)	35,260	35,839	37,075
Diluted (in shares)	35,260	36,152	37,075
Products
Revenues:
Revenues from products and services	$ 258,834	$ 303,279	$ 265,052
Cost of sales:
Total cost of sales	200,758	223,502	222,568
Services
Revenues:
Revenues from products and services	75,577	72,018	72,414
Cost of sales:
Total cost of sales	37,449	36,550	37,196
Leasing
Cost of sales:
Total cost of sales	$ 31,491	$ 34,955	$ 33,809