Note 2 - Summary of Significant Accounting Policies (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Sep. 30, 2019	Jan. 01, 2019
Percentage of Net Property, Plant, and Equipment Accounted for Under ASC980	84.30%	81.40%
Revenue Requirement, Cap Interest Rate, Percent of Prior Year	95.00%
Contract with Customer, Liability, Total				$ 3,600,000
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense, Total	$ 0
Operating Lease, Right-of-Use Asset	1,146,000
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability			$ 9,300,000
Operating Lease, Liability, Total	1,146,000
Accounting Standards Update 2016-02 [Member]
Operating Lease, Right-of-Use Asset					$ 1,073,919
Operating Lease, Liability, Total					$ 1,073,919
Transport Services [Member]
Deferred Revenue, Total	2,100,000	2,300,000
Service, Other [Member]
Contract with Customer, Liability, Total	$ 229,000	$ 126,000
Revenue Benchmark [Member]
Concentration Risk, Percentage	100.00%	100.00%
Revenue Benchmark [Member] | Customer Concentration Risk [Member] | Interstate Access Services [Member]
Concentration Risk, Percentage	23.30%	21.30%	20.70%