Marketable Securities and Equity Investments - Available-for-Sale Debt Securities by Contractual Maturity (Details) - Total marketable available-for-sale debt securities - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items]
Matures within one year	$ 1,509.7	$ 803.2
Matures after one year through five years	5,034.4	2,495.6
Matures after five years	73.5	2.2
Total	$ 6,617.6	$ 3,301.0