Note 5 - Derivative and Other Hedging Instruments (Details Textual) - Short [Member] $ in Millions	Sep. 30, 2024 USD ($) $ / item	Dec. 31, 2023 USD ($) $ / item
Ten Year Ultra Future [Member]
Derivative, Forward Price (in USD per Per Share) | $ / item	114.28	112.89
Derivative, Fair Value, Net | $	$ 14.3	$ 361.2
Five Year Treasury Note Futures [Member]
Derivative, Forward Price (in USD per Per Share) | $ / item		108.77
Derivative, Fair Value, Net | $		$ 458.5