Note 3 - Contracts With Customers 2 (Details Textual) - Long-term Contract with Customer [Member]	Mar. 31, 2021 USD ($)
Revenue, Remaining Performance Obligation, Amount	$ 1,700,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period (Year)	9 months
Revenue, Remaining Performance Obligation, Amount	$ 708,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period (Year)	1 year
Revenue, Remaining Performance Obligation, Amount	$ 497,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period (Year)	1 year
Revenue, Remaining Performance Obligation, Amount	$ 458,000