Investments - Private equity funds subject to lock-up or commitment periods (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Debt and Equity Securities, FV-NI [Line Items]
Other long-term investments, Fair value	$ 456.1	$ 4.0
Private equity
Debt and Equity Securities, FV-NI [Line Items]
Other long-term investments, Fair value	125.4
Private equity | 1 - 3 years
Debt and Equity Securities, FV-NI [Line Items]
Other long-term investments, Fair value	47.5
Private equity | 3 – 5 years
Debt and Equity Securities, FV-NI [Line Items]
Other long-term investments, Fair value	61.4
Private equity | 5 – 10 years
Debt and Equity Securities, FV-NI [Line Items]
Other long-term investments, Fair value	$ 16.5