Note 5 - Derivative and Other Hedging Instruments (Details Textual) - Short [Member] $ / item in Thousands, $ in Millions	Mar. 31, 2026 USD ($) $ / item	Dec. 31, 2025 USD ($) $ / item
Five Year Treasury Note Futures [Member]
Derivative, Forward Price (in USD per Per Share) | $ / item	108,180	109,300
Derivative, Fair Value, Net | $	$ 194.7	$ 133.9
Ten Year T-Note Futures [Member]
Derivative, Forward Price (in USD per Per Share) | $ / item	111,050	112,440
Derivative, Fair Value, Net | $	$ 58.9	$ 101.2
Ten Year Ultra Futures [Member]
Derivative, Forward Price (in USD per Per Share) | $ / item	113,520	115,020
Derivative, Fair Value, Net | $	$ 68.1	$ 69.0