Note 3 - Revenue 1 (Details Textual) Pure in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2026 USD ($)	Sep. 30, 2025 USD ($)	Sep. 30, 2026 USD ($)	Sep. 30, 2025 USD ($)	Dec. 31, 2025 USD ($)	Dec. 31, 2024 USD ($)
Contract with Customer, Asset, after Allowance for Credit Loss	$ 2,440		$ 2,440
Contract with Customer, Liability, Current	698		698		$ 1,026	$ 721
Contract with Customer, Liability, Revenue Recognized	$ 176	$ 1	$ 783	$ 544
Contract with Customer, Contracts in Progress, Number of Contracts Identified as Loss Contracts	0		0		0
Revenue, Remaining Performance Obligation, Amount	$ 16,626		$ 16,626
Air Pollution Control [Member]
Contract with Customer, Asset, after Allowance for Credit Loss					$ 887	$ 2,075