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Financial Instruments (Tables)
 3 Months Ended
Mar. 31, 2024
Investments, Debt and Equity Securities [Abstract]  
Summary of financial assets with maturities of less than 90 days included within cash and cash equivalents
The following table summarizes our financial assets with maturities of less than 90 days from the date of purchase included in cash and cash equivalents in our condensed consolidated balance sheets:
(In millions)As of March 31, 2024As of December 31, 2023
Money market funds$484.8 $610.7 
Total
$484.8 $610.7 
Marketable debt and equity securities The following tables summarize our marketable equity securities, classified as available-for-sale:
As of March 31, 2024
(In millions)Amortized
Cost		Gross
Unrealized
Gains		Gross
Unrealized
Losses		Fair
Value
Marketable equity securities
Marketable equity securities, current$11.7 $— $(11.0)$0.7 
Marketable equity securities, non-current916.7 — (587.9)328.8 
Total marketable equity securities$928.4 $— $(598.9)$329.5 

As of December 31, 2023
(In millions)Amortized
Cost		Gross
Unrealized
Gains		Gross
Unrealized
Losses		Fair
Value
Marketable equity securities
Marketable equity securities, current$31.6 $— $(21.0)$10.6 
Marketable equity securities, non-current948.3 — (542.1)406.2 
Total marketable equity securities$979.9 $— $(563.1)$416.8 
Proceeds from marketable debt securities
The proceeds from maturities and sales of marketable debt securities and resulting realized gains and losses are summarized as follows:
(In millions)For the Three Months Ended March 31, 2023
Proceeds from maturities and sales$406.7 
Realized gains0.1 
Realized losses0.7