Note 3 - Revenues 1 (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2018
Retained Earnings (Accumulated Deficit), Ending Balance	$ 327,137	$ 358,998
Disposal Group, Including Discontinued Operation, Contract Assets, Current	9,300	13,500
Disposal Group, Including Discontinued Operation, Contract Liabilities, Current	200	200
Increase (Decrease) in Contract with Customer, Liability	(289)	5,302	$ (22,728)
Contract with Customer, Liability, Total	37,500	32,300
Construction, Engineering and Installation Services [Member]
Revenue, Remaining Performance Obligation, Amount	$ 463,800
Difference Between Work Performed On Open Contracts And Contractual Billing Terms [Member]
Increase (Decrease) in Contract with Customer, Asset		1,100
Increase (Decrease) in Contract with Customer, Liability		$ 100
Product and Services [Member]
Revenue Recognized, Percent	90.20%	89.40%	91.30%
Product [Member]
Revenue Recognized, Percent	9.80%	10.60%	8.70%
Accounting Standards Update 2014-09 [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member]
Retained Earnings (Accumulated Deficit), Ending Balance				$ (300)