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Note 4 - Investments - Investment Gains (Losses), Net (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2025 | Sep. 30, 2024
Investment gains, net | $ 55.1 | $ 35.0 | $ 102.2 | $ 63.9
Seeded Investment Products and Hedges, Net [Member] |  |  |  |
Investment gains, net | 8.3 | 10.8 | 27.9 | 27.3
Third-party Ownership Interests in Seeded Investment Products [Member] |  |  |  |
Investment gains, net | 39.0 | 22.7 | 72.4 | 37.0
Equity Method Investments [Member] |  |  |  |
Investment gains, net | (1.1) | (1.0) | (4.4) | (4.5)
Other Security Investments [Member] |  |  |  |
Investment gains, net | $ 8.9 | $ 2.5 | $ 6.3 | $ 4.1

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