Summary of Accounting Policies and Accounting Changes - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022		Dec. 31, 2021		Dec. 31, 2020
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Policyholders’ Benefits and Incurred Losses and Loss Adjustment Expenses (Changes in Liability for Future Policyholder Benefits: 2023 - $33.5, 2022 - $12.0 and 2021 - $30.2)	$ 3,820.0	$ 4,432.6	[1]	$ 4,519.6	[1]
Reinsurance recoverables	86.5	99.6
Receivables from limited liability investments or partnership investments	0.0	35.2
Accrued investment income	88.4	94.3
Finite-lived intangible assets, net	268.9	267.0
Retained Earnings	1,014.3	1,366.4	[2]
Accumulated Other Comprehensive Loss	(360.8)	(514.9)	[2]
Earned Premiums (Changes in Deferred Profit Liability: 2023 - $84.2, 2022 - $60.2 and 2021 -$80.7)	4,529.4	5,213.4	[1]	5,179.2	[1]
Insurance Expenses	1,052.4	1,201.0	[1]	1,228.8	[1]
Income Tax Expense (Benefit)	$ 74.8	$ 84.4	[1]	$ 125.6	[1]
Basic (in dollars per share)	$ (4.25)	$ (4.50)	[1]	$ (1.92)	[1]
Diluted (in dollars per share)	$ (4.25)	$ (4.50)	[1]	$ (1.92)	[1]
Net Loss	$ (272.1)	$ (286.6)	[1]	$ (123.7)	[1]
Deferred Policy Acquisition Costs	591.6	635.6	[3]	688.0		$ 610.4
Deferred Income Tax Assets	210.4	129.0	[3]
Total Assets	12,742.7	13,313.6	[3]
Life and Health	3,422.4	3,276.2	[2]
Liabilities	10,237.7	10,643.0	[2]
Stockholders' Equity Attributable to Parent	2,505.2	2,670.6	[2]
Change in Discount Rate on Future Life Policyholder Benefits	(101.7)	1,380.7		228.5
Other Comprehensive Income (Loss), before Tax	195.6	(143.7)		(66.3)
Other Comprehensive Income Tax (Expense) Benefit	(41.5)	30.4		14.5
Other Comprehensive Income (Loss), Net of Tax	154.1	(113.3)		(51.8)
Other Comprehensive Income (Loss), before Tax, Portion Attributable to Parent		(399.9)		(175.5)
Increase (Decrease) in Deferred Policy Acquisition Costs	43.9	14.2	[4]	(77.6)	[4]
Insurance Reserves	(30.8)	26.5	[4]	616.4	[4]
Income Taxes	33.2	(83.6)	[4]	(163.9)	[4]
Net Cash Provided by (Used in) Operating Activities	(134.2)	(210.3)	[4]	350.7	[4]
Other Receivables
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reinsurance recoverables	27.8	39.6
Effect of Retrospective Application of Accounting Standards Update 2018-12 | Pre Adoption Balance
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained Earnings						2,071.2
Accumulated Other Comprehensive Loss						680.5
Effect of Retrospective Application of Accounting Standards Update 2018-12 | Post Adoption Balance
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained Earnings						2,046.1
Accumulated Other Comprehensive Loss						(349.8)
Effect of Retrospective Application of Accounting Standards Update 2018-12 | Adjustments to Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained Earnings						(25.1)
Accumulated Other Comprehensive Loss						0.0
Effect of Retrospective Application of Accounting Standards Update 2018-12 | Adjustments to AOCI
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained Earnings						0.0
Accumulated Other Comprehensive Loss						$ (1,030.3)
Revision of Prior Period, Accounting Standards Update, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Policyholders’ Benefits and Incurred Losses and Loss Adjustment Expenses (Changes in Liability for Future Policyholder Benefits: 2023 - $33.5, 2022 - $12.0 and 2021 - $30.2)		(71.8)		(81.2)
Retained Earnings		(13.7)
Accumulated Other Comprehensive Loss		241.1
Earned Premiums (Changes in Deferred Profit Liability: 2023 - $84.2, 2022 - $60.2 and 2021 -$80.7)		(52.9)		(74.5)
Insurance Expenses		0.4		10.7
Income Tax Expense (Benefit)		$ (3.9)		$ 0.8
Basic (in dollars per share)		$ 0.22		$ (0.05)
Diluted (in dollars per share)		$ 0.22		$ (0.05)
Net Loss		$ 14.6		$ (3.2)
Deferred Policy Acquisition Costs		10.0
Deferred Income Tax Assets		(60.4)
Total Assets		(50.4)
Life and Health		(277.8)
Liabilities		(277.8)
Stockholders' Equity Attributable to Parent		227.4
Effect of Modified Retrospective Application Accounting Standards Update 2018-12
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net Loss		14.6		(3.2)
Change in Discount Rate on Future Life Policyholder Benefits		1,380.7		228.5
Other Comprehensive Income (Loss), before Tax		1,380.7		228.5
Other Comprehensive Income Tax (Expense) Benefit		(289.9)		(47.9)
Other Comprehensive Income (Loss), Net of Tax		1,090.8		180.6
Other Comprehensive Income (Loss), before Tax, Portion Attributable to Parent		1,105.4		177.4
Increase (Decrease) in Deferred Policy Acquisition Costs		(0.4)		(10.7)
Insurance Reserves		(18.9)		(6.7)
Income Taxes		3.9		(0.8)
Net Cash Provided by (Used in) Operating Activities		0.0		0.0
Value of Business Acquired
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Finite-lived intangible assets, net	13.8	15.4
Customer Relationships
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Finite-lived intangible assets, net	1.7	2.7
Agent Relationships
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Finite-lived intangible assets, net	$ 43.4	50.6
Accounting Standards Update 2018-12
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Policyholders’ Benefits and Incurred Losses and Loss Adjustment Expenses (Changes in Liability for Future Policyholder Benefits: 2023 - $33.5, 2022 - $12.0 and 2021 - $30.2)		4,504.4		4,600.8
Retained Earnings		1,380.1
Accumulated Other Comprehensive Loss		(756.0)
Earned Premiums (Changes in Deferred Profit Liability: 2023 - $84.2, 2022 - $60.2 and 2021 -$80.7)		5,266.3		5,253.7
Insurance Expenses		1,200.6		1,218.1
Income Tax Expense (Benefit)		$ 88.3		$ 124.8
Basic (in dollars per share)		$ (4.72)		$ (1.87)
Diluted (in dollars per share)		$ (4.72)		$ (1.87)
Net Loss		$ (301.2)		$ (120.5)
Deferred Policy Acquisition Costs		625.6
Deferred Income Tax Assets		189.4
Total Assets		13,364.0
Life and Health		3,554.0
Liabilities		10,920.8
Stockholders' Equity Attributable to Parent		2,443.2
Change in Discount Rate on Future Life Policyholder Benefits		0.0		0.0
Other Comprehensive Income (Loss), before Tax		(1,524.4)		(294.8)
Other Comprehensive Income Tax (Expense) Benefit		320.3		62.4
Other Comprehensive Income (Loss), Net of Tax		(1,204.1)		(232.4)
Other Comprehensive Income (Loss), before Tax, Portion Attributable to Parent		(1,505.3)		(352.9)
Increase (Decrease) in Deferred Policy Acquisition Costs		13.8		(88.3)
Insurance Reserves		45.4		623.1
Income Taxes		(87.5)		(163.1)
Net Cash Provided by (Used in) Operating Activities		$ (210.3)		$ 350.7

[1] As of January 1, 2023, the Company adopted ASU 2018-12 using the modified retrospective method applied as of the transition date of January 1, 2021. Prior period amounts in the financial statements have been recast to reflect application of the new guidance. See Note 2 to the Consolidated Financial Statements for additional information.

[2] As of January 1, 2023, the Company adopted ASU 2018-12 using the modified retrospective method applied as of the transition date of January 1, 2021. Prior period amounts in the financial statements have been recast to reflect application of the new guidance. See Note 2 to the Consolidated Financial Statements for additional information.

[3] As of January 1, 2023, the Company adopted ASU 2018-12 using the modified retrospective method applied as of the transition date of January 1, 2021. Prior period amounts in the financial statements have been recast to reflect application of the new guidance. See Note 2 to the Consolidated Financial Statements for additional information.

[4] As of January 1, 2023, the Company adopted ASU 2018-12 using the modified retrospective method applied as of the transition date of January 1, 2021. Prior period amounts in the financial statements have been recast to reflect application of the new guidance. See Note 2 to the Consolidated Financial Statements for additional information.