Deferred Acquisition Costs and Other Actuarial Balances - Unearned Revenue Liability (Details) - Benefits and Protection - Life Insurance - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Other Actuarial Balances
Total unearned revenue liability	$ 475.4	$ 467.4		$ 384.4
Universal life
Other Actuarial Balances
Total unearned revenue liability	466.6	459.0	$ 425.3	$ 384.4
Other balances
Other Actuarial Balances
Total unearned revenue liability	$ 8.8	$ 8.4