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Fair Value Measurements - Narrative (Details) - USD ($)
$ in Millions
3 Months Ended
Mar. 31, 2025
Mar. 31, 2024
Dec. 31, 2024
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Securities owned not readily marketable $ 316.8   $ 159.8
Net unrealized gains (losses) 139.7 $ (196.2)  
Level 2 | Measured on a recurring basis      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Long-term debt, fair value 1,511.0   1,484.0
Level 3 | Measured on a recurring basis      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Equity investments $ 72.3   $ 52.0