Market Risk Benefits - Net Asset (Liability) Balances and Changes in Valuation of the MRBs for Individual Variable Annuities (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
The net asset (liability) balances and the changes in the valuation of the MRBs
Balance at beginning of period	$ (98.2)
Balance at end of period	(87.1)	$ (98.2)
Net amount at risk				$ 644.6
Retirement and Income Solutions | Individual variable annuities
The net asset (liability) balances and the changes in the valuation of the MRBs
Balance at beginning of period	(72.2)	(494.7)	$ (591.3)
Effect of changes in nonperformance risk at beginning of period	(31.7)	109.5	106.7
Adjusted balance at beginning of period	(103.9)	(385.2)	(484.6)
Interest accrual and expected policyholder behavior	(19.8)	(90.1)	(120.7)
Benefit payments	0.2	1.3	0.4
Changes in interest rates	(54.2)	539.1	154.3
Changes in equity markets	46.4	(112.4)	106.4
Changes in equity index volatility	30.6	(50.2)	15.1
Actual policyholder behavior different from expected behavior	(2.0)	1.5	2.3
Changes in future expected policyholder behavior	0.0	(6.1)	(96.6)
Changes in other future expected assumptions	0.0	(1.8)	38.2
Adjusted balance at end of period	(102.7)	(103.9)	(385.2)
Effect of changes in nonperformance risk at end of period	(39.6)	(31.7)	109.5
Balance at end of period	$ (63.1)	$ (72.2)	$ (494.7)
Weighted-average attained age of policyholders (years)	67 years 6 months	67 years 4 months 24 days
Net amount at risk	$ 299.8	$ 415.5		$ 591.3