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Note 5 - Derivative Instruments - Derivative Instruments (Details) - USD ($) $ in Millions | Mar. 31, 2025 | Dec. 31, 2024
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Futures [Member] |  |
Notional value of derivative | $ 832.0 | $ 789.0
Futures [Member] | Seeded Investment Products [Member] |  |
Notional value of derivative | 192.1 | 160.5
Foreign Currency, Forward Contracts and Swaps [Member] |  |
Notional value of derivative | 316.2 | 328.2
Foreign Currency, Forward Contracts and Swaps [Member] | Not Designated as Hedging Instrument, Economic Hedge [Member] |  |
Notional value of derivative | 41.8 | 38.4
Foreign Currency, Forward Contracts and Swaps [Member] | Seeded Investment Products [Member] |  |
Notional value of derivative | 234.4 | 196.6
Credit Default Swaps [Member] |  |
Notional value of derivative | 135.8 | 148.5
Credit Default Swaps [Member] | Seeded Investment Products [Member] |  |
Notional value of derivative | 3.0 | 4.3
Total Return Swaps [Member] |  |
Notional value of derivative | 97.2 | 69.7
Total Return Swaps [Member] | Seeded Investment Products [Member] |  |
Notional value of derivative | 5.0 | 10.3
Interest Rate Swap [Member] | Seeded Investment Products [Member] |  |
Notional value of derivative | $ 14.0 | $ 13.9

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