Investments - Equity Securities and Other-Long Term Investments at Fair Value (Details) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Debt and Equity Securities, FV-NI [Line Items]
Other long-term investments	$ 320.1	$ 316.5
Valued at Level 3
Debt and Equity Securities, FV-NI [Line Items]
Other long-term investments	87.0	86.6
Hedge funds and private equity funds
Debt and Equity Securities, FV-NI [Line Items]
Other long-term investments	191.0	186.0
Hedge funds and private equity funds \| Valued at NAV
Debt and Equity Securities, FV-NI [Line Items]
Other long-term investments	188.5	182.8
Hedge funds and private equity funds \| Valued at Level 3
Debt and Equity Securities, FV-NI [Line Items]
Other long-term investments	0.0	0.0
Strategic investments
Debt and Equity Securities, FV-NI [Line Items]
Other long-term investments	101.5	105.0
Other investments
Debt and Equity Securities, FV-NI [Line Items]
Other long-term investments	27.6	25.5
Strategic investments and Limited liability companies and private equity securities
Debt and Equity Securities, FV-NI [Line Items]
Unfunded commitments	$ 42.1	$ 36.1