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Fair Value Measurements - Assets and Liabilities Measured on a Recurring Basis (Details) - Fair Value Measured on a Recurring Basis - USD ($) $ in Millions | Sep. 30, 2024 | Dec. 31, 2023
--- | --- | ---
Financial Assets |  |
Investments in equity securities | $ 42.0 | $ 37.9
Investments in debt securities | 24.1 | 423.1
Financial Liabilities |  |
Contingent payment obligations | 6.5 | 14.7
Affiliate equity purchase obligations | 58.9 | 53.9
Quoted Prices in Active Markets for Identical Assets (Level 1) |  |
Financial Assets |  |
Investments in equity securities | 42.0 | 37.9
Investments in debt securities | 0.0 | 0.0
Financial Liabilities |  |
Contingent payment obligations | 0.0 | 0.0
Affiliate equity purchase obligations | 0.0 | 0.0
Significant Other Observable Inputs (Level 2) |  |
Financial Assets |  |
Investments in equity securities | 0.0 | 0.0
Investments in debt securities | 24.1 | 423.1
Financial Liabilities |  |
Contingent payment obligations | 0.0 | 0.0
Affiliate equity purchase obligations | 0.0 | 0.0
Significant Unobservable Inputs (Level 3) |  |
Financial Assets |  |
Investments in equity securities | 0.0 | 0.0
Investments in debt securities | 0.0 | 0.0
Financial Liabilities |  |
Contingent payment obligations | 6.5 | 14.7
Affiliate equity purchase obligations | $ 58.9 | $ 53.9

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