Fair Value Measurements - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net unrealized gains (losses)	$ (100.3)	$ 254.3	$ (295.9)	$ (120.6)
Write-down in other income (expense)	29.0
Securities owned not readily marketable	60.8		60.8		$ 48.3
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	$ 1,395.0		$ 1,395.0		$ 1,443.0