Basis of Presentation and Accounting Policies - Effects of Adoption, Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Change in Discount Rate on Future Life Policyholder Benefits	$ 50.6	$ 527.7	$ (59.2)	$ 1,090.0
Other Comprehensive Loss Before Income Taxes	(33.4)	(52.7)	43.5	(136.4)
Other Comprehensive Income Tax (Expense) Benefit	7.3	11.1	(9.4)	28.6
Other Comprehensive Income (Loss), Net of Taxes	(26.1)	(41.6)	34.1	(107.8)
Total Comprehensive Loss	(123.2)	(113.8)	(143.1)	(266.3)
Net Loss	$ (97.1)	(72.2)	(177.2)	(158.5)
Change in Deferred Policy Acquisition Costs			(10.6)	(2.1)
Insurance Reserves			(47.7)	(1.8)
Income Taxes			72.6	(46.2)
Net Cash Used in Operating Activities			$ (65.9)	(90.0)
Effect of Modified Retrospective Application Accounting Standards Update 2018-12
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Change in Discount Rate on Future Life Policyholder Benefits		527.7		1,090.0
Other Comprehensive Loss Before Income Taxes		527.7		1,090.0
Other Comprehensive Income Tax (Expense) Benefit		(110.8)		(228.9)
Other Comprehensive Income (Loss), Net of Taxes		416.9		861.1
Other Comprehensive Income (Loss), before Tax, Portion Attributable to Parent				872.1
Total Comprehensive Loss		419.4
Net Loss		2.5		11.0
Change in Deferred Policy Acquisition Costs				(0.8)
Insurance Reserves				(14.7)
Income Taxes				2.9
Net Cash Used in Operating Activities				0.0
Accounting Standards Update 2018-12
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Change in Discount Rate on Future Life Policyholder Benefits		0.0		0.0
Other Comprehensive Loss Before Income Taxes		(580.4)		(1,226.4)
Other Comprehensive Income Tax (Expense) Benefit		121.9		257.5
Other Comprehensive Income (Loss), Net of Taxes		(458.5)		(968.9)
Other Comprehensive Income (Loss), before Tax, Portion Attributable to Parent				(1,138.4)
Total Comprehensive Loss		(533.2)
Net Loss		$ (74.7)		(169.5)
Change in Deferred Policy Acquisition Costs				2.9
Insurance Reserves				12.9
Income Taxes				(49.1)
Net Cash Used in Operating Activities				$ (90.0)