Investments (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Dec. 31, 2024	Dec. 31, 2023
Schedule of Investments [Line Items]
Impairments (recoveries) losses on investments	$ 0.0
Allowance for credit losses	5.7	$ 9.7	$ 5.7	$ 10.0
Federal Home Loan Bank of Boston [Member]
Schedule of Investments [Line Items]
Securities on loan, fair value	344.7		130.9
Fixed Maturities [Member]
Schedule of Investments [Line Items]
Impairments (recoveries) losses on investments		$ 0.3
Fixed Maturities Including Held For Sale [Member]
Schedule of Investments [Line Items]
Allowance for credit losses	0.5		0.6
Mortgage Loans [Member]
Schedule of Investments [Line Items]
Allowance for credit losses	$ 5.7		$ 5.7