Deferred Acquisition Costs and Other Actuarial Balances - Disaggregated DAC amounts (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Deferred Acquisition Costs
Deferred acquisition costs	$ 3,948.3	$ 3,948.0		$ 3,822.3
Short-duration contracts
Deferred Acquisition Costs
Deferred acquisition costs	40.2	34.7
Other balances
Deferred Acquisition Costs
Deferred acquisition costs	9.2	8.8
Retirement and Income Solutions
Deferred Acquisition Costs
Deferred acquisition costs	925.6	930.0		964.4
Retirement and Income Solutions | Workplace savings and retirement solutions
Deferred Acquisition Costs
Deferred acquisition costs	500.2	498.0	$ 489.0	477.2
Retirement and Income Solutions | Individual variable annuities
Deferred Acquisition Costs
Deferred acquisition costs	276.8	278.0	281.2	281.9
Retirement and Income Solutions | Pension risk transfer
Deferred Acquisition Costs
Deferred acquisition costs	10.2	8.1	2.7
Retirement and Income Solutions | Individual fixed deferred annuities
Deferred Acquisition Costs
Deferred acquisition costs	124.7	131.0	162.2	192.7
Retirement and Income Solutions | Investment only
Deferred Acquisition Costs
Deferred acquisition costs	13.7	14.9	18.1	12.6
Benefits and Protection
Deferred Acquisition Costs
Deferred acquisition costs	2,973.3	2,974.5		2,857.9
Benefits and Protection | Life Insurance | Universal life
Deferred Acquisition Costs
Deferred acquisition costs	1,560.4	1,569.7	1,596.2	1,608.3
Benefits and Protection | Life Insurance | Term life
Deferred Acquisition Costs
Deferred acquisition costs	687.1	685.7	678.9	607.9
Benefits and Protection | Life Insurance | Participating life
Deferred Acquisition Costs
Deferred acquisition costs	90.8	93.0	102.3	111.9
Benefits and Protection | Specialty Benefits | Individual disability
Deferred Acquisition Costs
Deferred acquisition costs	$ 635.0	$ 626.1	$ 580.7	$ 529.8