Deferred Acquisition Costs and Other Actuarial Balances - Retirement and Income Solutions - Balances and changes in DAC (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Deferred Acquisition Costs
Beginning balance, Deferred acquisition costs	$ 3,948.0		$ 3,822.3
Ending balance, Deferred acquisition costs	3,948.3	$ 3,948.0
Retirement and Income Solutions
Deferred Acquisition Costs
Beginning balance, Deferred acquisition costs	930.0		964.4
Ending balance, Deferred acquisition costs	925.6	930.0
Workplace savings and retirement solutions | Retirement and Income Solutions
Deferred Acquisition Costs
Beginning balance, Deferred acquisition costs	498.0	489.0	477.2
Costs deferred	12.0	48.3	50.1
Amortized to expense	(9.8)	(39.3)	(38.3)
Ending balance, Deferred acquisition costs	500.2	498.0	489.0
Individual variable annuities | Retirement and Income Solutions
Deferred Acquisition Costs
Beginning balance, Deferred acquisition costs	278.0	281.2	281.9
Costs deferred	5.2	22.5	26.4
Amortized to expense	(6.4)	(25.7)	(27.1)
Ending balance, Deferred acquisition costs	276.8	278.0	281.2
Pension risk transfer | Retirement and Income Solutions
Deferred Acquisition Costs
Beginning balance, Deferred acquisition costs	8.1	2.7
Costs deferred	2.2	5.6	2.7
Amortized to expense	(0.1)	(0.2)
Ending balance, Deferred acquisition costs	10.2	8.1	2.7
Individual fixed deferred annuities | Retirement and Income Solutions
Deferred Acquisition Costs
Beginning balance, Deferred acquisition costs	131.0	162.2	192.7
Costs deferred			7.6
Amortized to expense	(6.3)	(31.2)	(38.1)
Ending balance, Deferred acquisition costs	124.7	131.0	162.2
Investment only | Retirement and Income Solutions
Deferred Acquisition Costs
Beginning balance, Deferred acquisition costs	14.9	18.1	12.6
Costs deferred		1.4	9.1
Amortized to expense	(1.2)	(4.6)	(3.6)
Ending balance, Deferred acquisition costs	$ 13.7	$ 14.9	$ 18.1