Note 3 - Contracts With Customers 2 (Details Textual) - Long-term Contract with Customer [Member] - USD ($)	Jun. 30, 2021	Mar. 31, 2021
Revenue, Remaining Performance Obligation, Amount	$ 1,600,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-07-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period (Year)		6 months
Revenue, Remaining Performance Obligation, Amount	590,000
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	551,000
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