Long-Duration Insurance Contracts - Separate Account Liability Rollforward (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2023	Dec. 31, 2022
Separate Account, Liability [Roll Forward]
Balance, beginning of year	$ 2,792.3
Balance, end of period	2,954.7	$ 2,792.3
Variable Account Annuities
Separate Account, Liability [Roll Forward]
Balance, beginning of year	2,792.3	3,441.0
Deposits	57.3	240.3
Withdrawals	(46.6)	(186.8)
Net transfers	(5.6)	(38.1)
Fees and charges	(9.1)	(36.8)
Market appreciation (depreciation)	168.2	(619.7)
Other	(1.8)	(7.6)
Balance, end of period	$ 2,954.7	$ 2,792.3