Note 2 - Summary of Significant Accounting Policies (Details Textual) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2025	Jun. 30, 2025	Dec. 31, 2024	Dec. 31, 2022
Investment Plan, Maximum Amount. Approved				$ 20,000
Inventory, Net		$ 616	$ 397
Equipment Constructed for Resale [Member]
Inventory, Net		176	176
Spare Parts [Member]
Inventory, Net		440	221
In Process Equipment [Member]
Inventory, Net		44	$ 44
Minimum [Member]
Debt Securities, Held-to-maturity, Maturity Term (Month)	3 months
Maximum [Member]
Debt Securities, Held-to-maturity, Maturity Term (Month)	36 months
Asset Pledged as Collateral [Member] | Letter of Credit [Member]
Restricted Cash and Investments		4,385
Asset Pledged as Collateral [Member] | Letter of Credit [Member] | Varying Maturity Dates Expiring No Later Than June 30, 2026 [Member]
Restricted Cash and Investments		2,933
Asset Pledged as Collateral [Member] | Letter of Credit [Member] | Latest Maturity Dates Expiring No Later Than March 31, 2027 [Member]
Restricted Cash and Investments		$ 1,452