Note 5 - Derivative Instruments - Change in Fair Value of Derivatives (Details) - Not Designated as Hedging Instrument [Member] - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2025 |
Jun. 30, 2024 |
Jun. 30, 2025 |
Jun. 30, 2024 |
|
| Gain (losses) from derivative instruments | $ (26.3) | $ (0.2) | $ (24.2) | $ (11.9) |
| Futures [Member] | ||||
| Gain (losses) from derivative instruments | (20.8) | 2.9 | (23.1) | (5.8) |
| Credit Default Swaps [Member] | ||||
| Gain (losses) from derivative instruments | (1.2) | (0.1) | (0.6) | (1.5) |
| Total Return Swaps [Member] | ||||
| Gain (losses) from derivative instruments | (7.1) | (1.3) | (5.5) | (5.9) |
| Foreign Currency, Forward Contracts and Swaps [Member] | ||||
| Gain (losses) from derivative instruments | 3.2 | (1.8) | 5.4 | 0.9 |
| TBAs [Member] | ||||
| Gain (losses) from derivative instruments | $ (0.4) | $ 0.1 | $ (0.4) | $ 0.4 |