Note 5 - Derivatives - Interest Rate Swaps Outstanding (Details) - Rio Grande [Member] - Contingent Interest Rate Swaps [Member] $ in Millions	9 Months Ended
	Sep. 30, 2023 USD ($)
Initial Notional Amount	$ 123
Maturity Date	Jul. 12, 2030
Variable Interest Rate Received	3.40%
Maximum [Member]
Initial Notional Amount	$ 8,500