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Note 4 - Investments (Tables) | 3 Months Ended
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Mar. 31, 2025
Notes Tables |
Investment [Table Text Block] |
|  | March 31, |  |  | December 31, |
|  | 2025 |  |  | 2024 |
Current investments: |  |  |  |  |  |  |  |
Seeded investment products: |  |  |  |  |  |  |  |
Consolidated VIEs |  | $ | 713.4 |  |  | $ | 502.1 |
Consolidated VREs |  |  | 127.9 |  |  |  | 132.5 |
Unconsolidated VIEs and VREs |  |  | 101.1 |  |  |  | 127.1 |
Separately managed accounts |  |  | 37.3 |  |  |  | 41.9 |
Total seeded investment products |  |  | 979.7 |  |  |  | 803.6 |
Investments related to deferred compensation plans |  |  | 37.9 |  |  |  | 29.8 |
Other investments |  |  | 58.5 |  |  |  | 5.8 |
Total current investments |  | $ | 1,076.1 |  |  | $ | 839.2 |
Non-current investments: |  |  |  |  |  |  |  |
Equity method investments |  |  | 20.5 |  |  |  | 23.1 |
Total investments |  | $ | 1,096.6 |  |  | $ | 862.3 |
Gain (Loss) on Securities [Table Text Block] |
|  | Three months ended |
|  | March 31, |
|  | 2025 |  |  | 2024 |
Seeded investment products and seed hedges, net |  | $ | 5.8 |  |  | $ | 11.9 |
Third-party ownership interests in seeded investment products |  |  | (3.3 | ) |  |  | 10.5 |
Equity method investments |  |  | (1.7 | ) |  |  | (1.4 | )
Other |  |  | (6.3 | ) |  |  | 1.5 |
Investment gains (losses), net |  | $ | (5.5 | ) |  | $ | 22.5 |
Unrealized Gain (Loss) on Investments [Table Text Block] |
|  | March 31, |
|  | 2025 |  |  | 2024 |
Unrealized gains (losses), net |  | $ | 29.2 |  |  | $ | 28.1 |
Cash Flows Related to Investment Securities and Other Assets [Table Text Block] |
|  | Three months ended March 31, |
|  | 2025 |  |  | 2024 |
|  | Purchases |  |  | Sales, |  |  |  |  |  |  | Purchases |  |  | Sales, |  |  |  |  |
|  | and |  |  | settlements and |  |  | Net |  |  | and |  |  | settlements and |  |  | Net |
|  | settlements |  |  | maturities |  |  | cash flow |  |  | settlements |  |  | maturities |  |  | cash flow |
Investments by consolidated seeded investment products |  | $ | (204.2 | ) |  | $ | 22.5 |  |  | $ | (181.7 | ) |  | $ | (41.1 | ) |  | $ | 3.0 |  |  | $ | (38.1 | )
Investments |  |  | (119.1 | ) |  |  | 74.3 |  |  |  | (44.8 | ) |  |  | (65.7 | ) |  |  | 55.8 |  |  |  | (9.9 | )

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