Note 2 - Summary of Significant Accounting Policies (Details Textual) - USD ($) $ in Thousands	6 Months Ended
Jun. 30, 2022	Dec. 31, 2021
Restricted Cash and Cash Equivalents, Total	$ 1,990
Investment Plan, Maximum Amount. Approved	10,000
Inventory, Net, Total	405	$ 348
Equipment Contstructed for Resale [Member]
Inventory, Net, Total	208	227
Spare Parts [Member]
Inventory, Net, Total	$ 197	$ 121
Minimum [Member]
Debt Securities, Held-to-maturity, Maturity Term (Month)	3 months
Maximum [Member]
Debt Securities, Held-to-maturity, Maturity Term (Month)	36 months
Money Market Funds [Member]
Restricted Cash and Investments, Total	$ 10,000

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Amount after valuation and LIFO reserves of inventory expected to be sold, or consumed within one year or operating cycle, if longer.

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Amount of cash and cash equivalents restricted as to withdrawal or usage. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Cash and investments whose use in whole or in part is restricted for the long-term, generally by contractual agreements or regulatory requirements. For use in an unclassified balance sheet.

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