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Note 5 - Derivative Instruments - Derivative Instruments (Details) - USD ($) $ in Millions | Sep. 30, 2025 | Dec. 31, 2024
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Futures [Member] |  |
Notional value of derivative | $ 1,471.3 | $ 789.0
Futures [Member] | Seeded Investment Products [Member] |  |
Notional value of derivative | 711.9 | 160.5
Foreign Currency, Forward Contracts and Swaps [Member] |  |
Notional value of derivative | 296.6 | 328.2
Foreign Currency, Forward Contracts and Swaps [Member] | Not Designated as Hedging Instrument, Economic Hedge [Member] |  |
Notional value of derivative | 36.9 | 38.4
Foreign Currency, Forward Contracts and Swaps [Member] | Seeded Investment Products [Member] |  |
Notional value of derivative | 286.4 | 196.6
Credit Default Swaps [Member] |  |
Notional value of derivative | 159.5 | 148.5
Credit Default Swaps [Member] | Seeded Investment Products [Member] |  |
Notional value of derivative | 12.7 | 4.3
Total Return Swaps [Member] |  |
Notional value of derivative | 59.4 | 69.7
Total Return Swaps [Member] | Seeded Investment Products [Member] |  |
Notional value of derivative | 32.5 | 10.3
Interest Rate Swap [Member] | Seeded Investment Products [Member] |  |
Notional value of derivative | 15.0 | 13.9
TBAs [Member] |  |
Notional value of derivative | 42.6 | 9.1
Other [Member] | Seeded Investment Products [Member] |  |
Notional value of derivative | $ 1.6 | $ 0.0

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