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Fair Value (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended	9 Months Ended
	Sep. 30, 2024	Jun. 30, 2025	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Fair Value Disclosure [Line Items]
Transfers between Fair Value Hierarchies		$ 0.0	$ 0.0
Allowance for Credit Loss			0.1		$ 0.1
Debt Securities, Available-for-Sale, Realized Gain	$ 0.1		0.1	$ 0.5
Debt and Equity Securities, FV-NI [Line Items]
Equity Securities, FV-NI, Cost			7.9
Debt and Equity Securities, Unrealized Gain (Loss)			0.6
Equity Securities, FV-NI			8.5
Net Assets			17.9
Net Assets			17.9
U.S. Treasury debt securities
Fair Value Disclosure [Line Items]
Allowance for Credit Loss			0.0
Corporate/Other debt securities
Fair Value Disclosure [Line Items]
Allowance for Credit Loss			$ 0.1		$ 0.1

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