Fair Value (Available-For-Sale Securities) (Details) - USD ($) $ in Millions	Sep. 30, 2026	Dec. 31, 2025
Fair Value Disclosure [Line Items]
Amortized Cost	$ 173.0	$ 145.8
Gross Unrealized Gains	0.3	2.4
Gross Unrealized Losses	(7.2)	(2.1)
Fair Value	166.1	146.1
U.S. Treasury debt securities
Fair Value Disclosure [Line Items]
Amortized Cost	6.9	9.5
Gross Unrealized Gains	0.0	0.0
Gross Unrealized Losses	(0.1)	0.0
Fair Value	6.8	9.5
Corporate/Other debt securities
Fair Value Disclosure [Line Items]
Amortized Cost	166.1	136.3
Gross Unrealized Gains	0.3	2.4
Gross Unrealized Losses	(7.1)	(2.1)
Fair Value	159.3	136.6
Debt Securities, Available-for-sale, Unrealized Loss Position	139.3	40.2
US Treasury Securities
Fair Value Disclosure [Line Items]
Fair Value	4.0
Debt Securities, Available-for-sale, Unrealized Loss Position	$ 6.2	$ 3.5

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

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