Note 3 - Contracts With Customers 2 (Details Textual)	Mar. 31, 2019 USD ($)
Revenue, Remaining Performance Obligation, Amount	$ 524,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-04-01
Revenue, Remaining Performance Obligation, Amount	$ 419,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Amount	$ 105,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year