Note 5 - Derivative Instruments - Change in Fair Value of Derivatives (Details) - Not Designated as Hedging Instrument [Member] - USD ($) $ in Millions |
3 Months Ended | |
|---|---|---|
Mar. 31, 2025 |
Mar. 31, 2024 |
|
| Gain (losses) from derivative instruments | $ 2.1 | $ (12.0) |
| Futures [Member] | ||
| Gain (losses) from derivative instruments | (2.3) | (8.7) |
| Credit Default Swaps [Member] | ||
| Gain (losses) from derivative instruments | 0.6 | (1.4) |
| Total Return Swaps [Member] | ||
| Gain (losses) from derivative instruments | 1.6 | (4.6) |
| Foreign Currency, Forward Contracts and Swaps [Member] | ||
| Gain (losses) from derivative instruments | $ 2.2 | $ 2.7 |