Separate Account Balances - Retirement and Income Solutions (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2023	Dec. 31, 2022
Changes in separate account liabilities
Balance at beginning of period	$ 155,375.1
Balance at end of period	162,000.8	$ 155,375.1
Retirement and Income Solutions
Changes in separate account liabilities
Balance at beginning of period	115,899.1
Balance at end of period	120,186.1	115,899.1
Retirement and Income Solutions | Group retirement contracts
Changes in separate account liabilities
Balance at beginning of period	107,240.1	131,188.6
Premiums and deposits	2,881.3	14,859.3
Policy charges	(77.7)	(383.7)
Surrenders, withdrawals and benefit payments	(2,747.8)	(14,479.4)
Investment performance	5,016.8	(20,641.3)
Net transfers (to) from general account	(1,331.8)	(2,571.7)
Other	294.9	(731.7)
Balance at end of period	111,275.8	107,240.1
Cash surrender value	109,850.4	106,125.7
Retirement and Income Solutions | Individual variable annuities
Changes in separate account liabilities
Balance at beginning of period	8,659.0	11,000.0
Premiums and deposits	94.8	354.1
Policy charges	(51.2)	(211.1)
Surrenders, withdrawals and benefit payments	(217.3)	(790.1)
Investment performance	417.6	(1,723.3)
Net transfers (to) from general account	7.4	29.4
Balance at end of period	8,910.3	8,659.0
Cash surrender value	$ 8,789.3	$ 8,538.7