Contractholder Funds - Changes in Policyholder Account Balances (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2023	Dec. 31, 2022
Changes in policyholder account balances
Balance at beginning of period	$ 26,349.6
Balance at end of period	26,184.4	$ 26,349.6
Retirement and Income Solutions
Changes in policyholder account balances
Balance at beginning of period	19,764.4
Balance at end of period	19,628.4	19,764.4
Retirement and Income Solutions | Workplace savings and retirement solutions
Changes in policyholder account balances
Balance at beginning of period	12,154.7	10,996.2
Premiums and deposits	1,337.6	3,719.5
Policy charges	(7.5)	(28.5)
Surrenders, withdrawals and benefit payments	(1,960.2)	(2,866.7)
Net transfers from (to) separate account	896.8	164.6
Interest credited	63.3	194.3
Other	(8.1)	(24.7)
Balance at end of period	$ 12,476.6	$ 12,154.7
Weighted-average crediting rate	2.16%	1.94%
Cash surrender value	$ 10,797.2	$ 10,341.7
Retirement and Income Solutions | Individual variable annuities
Changes in policyholder account balances
Balance at beginning of period	381.4	380.9
Premiums and deposits	110.2	426.5
Surrenders, withdrawals and benefit payments	(243.1)	(843.2)
Net transfers from (to) separate account	115.1	406.6
Interest credited	2.5	10.6
Balance at end of period	$ 366.1	$ 381.4
Weighted-average crediting rate	2.81%	2.79%
Cash surrender value	$ 363.3	$ 378.6
Retirement and Income Solutions | Individual fixed deferred annuities
Changes in policyholder account balances
Balance at beginning of period	7,228.3	9,646.3
Premiums and deposits	7.5	35.9
Surrenders, withdrawals and benefit payments	(492.8)	(2,655.6)
Interest credited	42.7	201.7
Balance at end of period	$ 6,785.7	$ 7,228.3
Weighted-average crediting rate	2.67%	2.63%
Cash surrender value	$ 6,648.8	$ 7,081.4
Benefits and Protection | Life Insurance | Universal life
Changes in policyholder account balances
Balance at beginning of period	6,947.9	6,962.5
Premiums and deposits	312.4	1,267.2
Policy charges	(213.5)	(837.8)
Surrenders, withdrawals and benefit payments	(170.4)	(390.0)
Net transfers from (to) separate account	(13.1)	(301.5)
Interest credited	52.4	247.5
Other	(0.3)
Balance at end of period	6,915.4	6,947.9
Reinsurance impact	(3,496.8)	(3,528.9)
Balance at end of period after reinsurance	$ 3,418.6	$ 3,419.0
Weighted-average crediting rate	3.33%	3.35%
Net amount at risk	$ 86,335.6	$ 86,547.9
Cash surrender value	$ 5,883.5	$ 5,911.5