Deposit Asset on Reinsurance (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Effects of Reinsurance [Line Items]
Reinsurance block of in-force fixed and variable annuity business	$ 3,100.0
Minimum crediting rating (percent)	4.50%
Percentage of forced fixed annuities (percent)	50.00%
Fixed annuity reserves reinsured on a coinsurance basis	$ 2,300.0
Separate account asset	4,157.4	$ 3,708.8
Separate account liability	4,157.4	3,708.8
Net investment income	464.3	445.7	$ 444.8
Deposit Asset On Reinsurance
Effects of Reinsurance [Line Items]
Net investment income	98.1	$ 101.4	$ 104.9
Reinsurance Contract Modified Coinsurance Basis
Effects of Reinsurance [Line Items]
Separate account asset	800.0
Separate account liability	$ 800.0