Financial Instruments - Marketable debt and equity securities (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Debt Securities, Available-for-Sale, Amortized Cost [Abstract]
Amortized Cost	$ 97.6
Gross unrealized gains	0.0
Gross Unrealized Losses	0.0
Fair Value	97.6
Debt Securities, Trading, and Equity Securities, FV-NI, Cost [Abstract]
Amortized Cost	227.8	$ 668.7
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	(123.9)	(489.0)
Fair Value	103.9	179.7
Corporate Debt Securities Current
Debt Securities, Available-for-Sale, Amortized Cost [Abstract]
Amortized Cost	71.0
Gross unrealized gains	0.0
Gross Unrealized Losses	0.0
Fair Value	71.0
Government Securities Current
Debt Securities, Available-for-Sale, Amortized Cost [Abstract]
Amortized Cost	26.6
Gross unrealized gains	0.0
Gross Unrealized Losses	0.0
Fair Value	26.6
Equity Securities, Non-Current
Debt Securities, Trading, and Equity Securities, FV-NI, Cost [Abstract]
Amortized Cost	227.8	668.7
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	(123.9)	(489.0)
Fair Value	$ 103.9	$ 179.7

Equity Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax

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Equity Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, Before Tax

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Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI), classified as current.

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Cost of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). Excludes equity method investment and investment in equity security without readily determinable fair value.

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