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Note 6 - Fair Value Measurements - Level of Fair Value (Details) - USD ($) $ in Millions | 9 Months Ended |
--- | --- | ---
Sep. 30, 2025 | Dec. 31, 2024
Total investment securities |  | $ 395.9 |  | $ 337.1 |
Variable Interest Entity, Primary Beneficiary [Member] |  |  |  |  |
Total investment securities |  | 1,067.5 |  | 502.1 |
Fair Value, Recurring [Member] |  |  |  |  |
Cash equivalents |  | 657.3 |  | 821.7 |
Total investment securities |  | 1,463.4 |  | 839.2 |
Other |  | 5.1 |  |  |
Total assets |  | 2,125.8 |  | 1,673.6 |
Seed hedge derivatives |  | 25.7 |  |  |
Long-term debt |  | 404.8 | [1] | 383.3 | [2]
Contingent consideration |  | 24.5 |  | 30.4 |
Total liabilities |  | 583.9 |  | 543.0 |
Other |  |  |  | 5.1 |
Fair Value, Recurring [Member] | Derivatives Used in Consolidated Seeded Investment Products [Member] |  |  |  |  |
Other |  |  |  | 12.7 |
Fair Value, Recurring [Member] | Seed Hedge Derivatives [Member] |  |  |  |  |
Seed hedge derivatives |  | 10.3 |  | 8.5 |
Fair Value, Recurring [Member] | Deferred Bonuses Hedge [Member] |  |  |  |  |
Seed hedge derivatives |  | 92.6 |  | 115.7 |
Fair Value, Recurring [Member] | Warrants Liability [Member] |  |  |  |  |
Warrants |  | 26.0 |  |  |
Fair Value, Recurring [Member] | Other Investment Securities [Member] |  |  |  |  |
Total investment securities |  | 395.9 |  | 337.1 |
Fair Value, Recurring [Member] | Variable Interest Entity, Primary Beneficiary [Member] |  |  |  |  |
Total investment securities |  | 1,067.5 |  | 502.1 |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] |  |  |  |  |
Cash equivalents |  | 657.3 |  | 821.7 |
Total investment securities |  | 838.2 |  | 534.4 |
Other |  | 0.0 |  |  |
Total assets |  | 1,495.5 |  | 1,356.1 |
Seed hedge derivatives |  | 4.6 |  |  |
Long-term debt |  | 0.0 | [1] | 0.0 | [2]
Contingent consideration |  | 0.0 |  | 0.0 |
Total liabilities |  | 4.6 |  | 1.9 |
Other |  |  |  | 1.9 |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Derivatives Used in Consolidated Seeded Investment Products [Member] |  |  |  |  |
Other |  |  |  | 0.0 |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Seed Hedge Derivatives [Member] |  |  |  |  |
Seed hedge derivatives |  | 0.0 |  | 0.0 |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Deferred Bonuses Hedge [Member] |  |  |  |  |
Seed hedge derivatives |  | 0.0 |  | 0.0 |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Warrants Liability [Member] |  |  |  |  |
Warrants |  | 0.0 |  |  |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Other Investment Securities [Member] |  |  |  |  |
Total investment securities |  | 322.4 |  | 273.8 |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Variable Interest Entity, Primary Beneficiary [Member] |  |  |  |  |
Total investment securities |  | 515.8 |  | 260.6 |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] |  |  |  |  |
Cash equivalents |  | 0.0 |  | 0.0 |
Total investment securities |  | 576.2 |  | 275.2 |
Other |  | 2.3 |  |  |
Total assets |  | 578.5 |  | 285.4 |
Seed hedge derivatives |  | 2.5 |  |  |
Long-term debt |  | 404.8 | [1] | 383.3 | [2]
Contingent consideration |  | 0.0 |  | 0.0 |
Total liabilities |  | 443.6 |  | 395.0 |
Other |  |  |  | 3.2 |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Derivatives Used in Consolidated Seeded Investment Products [Member] |  |  |  |  |
Other |  |  |  | 10.2 |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Seed Hedge Derivatives [Member] |  |  |  |  |
Seed hedge derivatives |  | 10.3 |  | 8.5 |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Deferred Bonuses Hedge [Member] |  |  |  |  |
Seed hedge derivatives |  | 0.0 |  | 0.0 |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Warrants Liability [Member] |  |  |  |  |
Warrants |  | 26.0 |  |  |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Other Investment Securities [Member] |  |  |  |  |
Total investment securities |  | 24.5 |  | 33.7 |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Variable Interest Entity, Primary Beneficiary [Member] |  |  |  |  |
Total investment securities |  | 551.7 |  | 241.5 |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] |  |  |  |  |
Cash equivalents |  | 0.0 |  | 0.0 |
Total investment securities |  | 28.6 |  | 2.0 |
Other |  | 2.8 |  |  |
Total assets |  | 31.4 |  | 4.5 |
Seed hedge derivatives |  | 18.6 |  |  |
Long-term debt |  | 0.0 | [1] | 0.0 | [2]
Contingent consideration |  | 24.5 |  | 30.4 |
Total liabilities |  | 135.7 |  | 146.1 |
Other |  |  |  | 0.0 |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Derivatives Used in Consolidated Seeded Investment Products [Member] |  |  |  |  |
Other |  |  |  | 2.5 |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Seed Hedge Derivatives [Member] |  |  |  |  |
Seed hedge derivatives |  | 0.0 |  | 0.0 |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Deferred Bonuses Hedge [Member] |  |  |  |  |
Seed hedge derivatives |  | 92.6 |  | 115.7 |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Warrants Liability [Member] |  |  |  |  |
Warrants |  | 0.0 |  |  |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Other Investment Securities [Member] |  |  |  |  |
Total investment securities |  | 28.6 |  | 2.0 |
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Variable Interest Entity, Primary Beneficiary [Member] |  |  |  |  |
Total investment securities |  | 0.0 |  | 0.0 |
Fair Value, Recurring [Member] | Fair Value Measured at Net Asset Value Per Share [Member] |  |  |  |  |
Cash equivalents |  | 0.0 | [3] | 0.0 | [4]
Total investment securities |  | 20.4 | [3] | 27.6 | [4]
Other | [3] | 0.0 |  |  |
Total assets |  | 20.4 | [3] | 27.6 | [4]
Seed hedge derivatives | [3] | 0.0 |  |  |
Long-term debt |  | 0.0 | [1],[3] | 0.0 | [2],[4]
Contingent consideration |  | 0.0 | [3] | 0.0 | [4]
Total liabilities |  | 0.0 | [3] | 0.0 | [4]
Other | [4] |  |  | 0.0 |
Fair Value, Recurring [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Derivatives Used in Consolidated Seeded Investment Products [Member] |  |  |  |  |
Other | [4] |  |  | 0.0 |
Fair Value, Recurring [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Seed Hedge Derivatives [Member] |  |  |  |  |
Seed hedge derivatives |  | 0.0 |  | 0.0 |
Fair Value, Recurring [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Deferred Bonuses Hedge [Member] |  |  |  |  |
Seed hedge derivatives |  | 0.0 | [3] | 0.0 | [4]
Fair Value, Recurring [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Warrants Liability [Member] |  |  |  |  |
Warrants |  | 0.0 |  |  |
Fair Value, Recurring [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Other Investment Securities [Member] |  |  |  |  |
Total investment securities |  | 20.4 | [3] | 27.6 | [4]
Fair Value, Recurring [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | Variable Interest Entity, Primary Beneficiary [Member] |  |  |  |  |
Total investment securities |  | $ 0.0 | [3] | $ 0.0 | [4]
[1] | Carried at amortized cost in our Consolidated Balance Sheets and disclosed in this table at fair value.
[2] | Carried at amortized cost in our Condensed Consolidated Balance Sheets and disclosed in this table at fair value.
[3] | Certain seeded investment products that do not have a readily determinable fair value have been measured at fair value using the net asset value (“NAV”) as a practical expedient and have not been categorized in the fair value hierarchy.
[4] | Certain seeded investment products that do not have a readily determinable fair value have been measured at fair value using the NAV as a practical expedient and have not been categorized in the fair value hierarchy.

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- Definition Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 825 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 11 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482907/825-10-50-11 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 825 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 11 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482907/825-10-50-11 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 825 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 10 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482907/825-10-50-10 Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 + Details
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- Definition Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. 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