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Financial Instruments and Fair Value - Investments (Details) - USD ($) $ in Millions | Sep. 30, 2025 | Dec. 31, 2024
--- | --- | ---
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | $ 1,317.8 | $ 1,126.0
Unrealized Gains | 1.1 | 0.7
Unrealized Losses | (0.2) | (0.3)
Fair Value | 1,318.7 | 1,126.4
Marketable equity securities | 98.1 | 64.2
Fair Value | 1,416.8 | 1,190.6
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract] |  |
Less Than 12 Months, Fair Value | 1,318.7 | 251.6
Less Than 12 Months, Unrealized Losses | (0.2) | (0.3)
12 Months or Greater, Fair Value | 0.0 | 0.0
12 Months or Greater, Unrealized Losses | 0.0 | 0.0
Total, Fair Value | 1,318.7 | 251.6
Total, Unrealized Losses | (0.2) | (0.3)
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract] |  |
Due within one year | 1,029.6 | 1,126.4
Due within one to three years | 289.1 | 0.0
Fair Value | 1,318.7 | 1,126.4
U.S. government and agency securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 560.0 | 469.1
Unrealized Gains | 0.6 | 0.4
Unrealized Losses | (0.1) | 0.0
Fair Value | 560.5 | 469.5
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract] |  |
Less Than 12 Months, Fair Value | 560.5 | 27.8
Less Than 12 Months, Unrealized Losses | (0.1) | 0.0
12 Months or Greater, Fair Value | 0.0 | 0.0
12 Months or Greater, Unrealized Losses | 0.0 | 0.0
Total, Fair Value | 560.5 | 27.8
Total, Unrealized Losses | (0.1) | 0.0
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract] |  |
Fair Value | 560.5 | 469.5
Commercial paper |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 370.4 | 428.7
Unrealized Gains | 0.1 | 0.2
Unrealized Losses | 0.0 | (0.2)
Fair Value | 370.5 | 428.7
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract] |  |
Less Than 12 Months, Fair Value | 370.5 | 149.4
Less Than 12 Months, Unrealized Losses | 0.0 | (0.2)
12 Months or Greater, Fair Value | 0.0 | 0.0
12 Months or Greater, Unrealized Losses | 0.0 | 0.0
Total, Fair Value | 370.5 | 149.4
Total, Unrealized Losses | 0.0 | (0.2)
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract] |  |
Fair Value | 370.5 | 428.7
Corporate debt securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 285.2 | 166.4
Unrealized Gains | 0.3 | 0.1
Unrealized Losses | (0.1) | (0.1)
Fair Value | 285.4 | 166.4
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract] |  |
Less Than 12 Months, Fair Value | 285.4 | 63.5
Less Than 12 Months, Unrealized Losses | (0.1) | (0.1)
12 Months or Greater, Fair Value | 0.0 | 0.0
12 Months or Greater, Unrealized Losses | 0.0 | 0.0
Total, Fair Value | 285.4 | 63.5
Total, Unrealized Losses | (0.1) | (0.1)
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract] |  |
Fair Value | 285.4 | 166.4
Certificates of deposit and term deposits |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized Cost | 102.2 | 61.8
Unrealized Gains | 0.1 | 0.0
Unrealized Losses | 0.0 | 0.0
Fair Value | 102.3 | 61.8
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract] |  |
Less Than 12 Months, Fair Value | 102.3 | 10.9
Less Than 12 Months, Unrealized Losses | 0.0 | 0.0
12 Months or Greater, Fair Value | 0.0 | 0.0
12 Months or Greater, Unrealized Losses | 0.0 | 0.0
Total, Fair Value | 102.3 | 10.9
Total, Unrealized Losses | 0.0 | 0.0
Available-for-sale Securities, Debt Maturities, Fair Value [Abstract] |  |
Fair Value | $ 102.3 | $ 61.8

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