Note 4 - Other Accrued Liabilities - Other Accrued Liabilities (Details) - USD ($)	Dec. 31, 2021	Dec. 31, 2020
Equipment maintenance and upgrades	$ 1,281,000	$ 0
Insurance	340,000	471,000
Professional services	90,000	211,000
Operating costs	397,000	703,000
Other	311,000	660,000
Total other accrued liabilities	$ 2,419,000	$ 2,045,000