Marketable Securities and Equity Investments - Available-for-Sale Debt Securities at Fair Value (Details) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Debt securities	$ 6,301.2	$ 5,642.8
Cash and cash equivalents
Debt Securities, Available-for-sale [Line Items]
Debt securities	3,911.3	5,372.9
Marketable securities
Debt Securities, Available-for-sale [Line Items]
Debt securities	$ 1,032.6	$ 157.7