Note 2 - Summary of Significant Accounting Policies (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2019
Percentage of Net Property, Plant, and Equipment Accounted for Under ASC980	81.40%	80.50%
Revenue Requirement, Cap Interest Rate, Percent of Prior Year	95.00%
Concentration Risk, Percentage	100.00%
Deferred Revenue	$ 2,300,000	$ 2,400,000
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense, Total	$ 0
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability		$ 9,300,000
Accounting Standards Update 2016-02 [Member] | Subsequent Event [Member]
Operating Lease, Right-of-Use Asset				$ 1,073,919
Operating Lease, Liability, Total				$ 1,073,919
Sales Revenue, Services, Net [Member] | Customer Concentration Risk [Member]
Concentration Risk, Percentage	22.60%	21.90%	18.60%