Deposit Asset on Reinsurance - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
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	$ 2,500.0
Net investment income	400.9	$ 422.5	$ 357.6
Separate account asset	2,792.3	3,441.0
Separate account liability	2,792.3	3,441.0
Reinsurance Contract Modified Coinsurance Basis
Effects of Reinsurance [Line Items]
Separate account asset	600.0
Separate account liability	600.0
Deposit Asset On Reinsurance
Effects of Reinsurance [Line Items]
Net investment income	$ 103.5	$ 101.1	$ 97.3