Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Cash Flows from Operating Activities:
Net (Loss) Income	$ (301.2)	$ (120.5)	$ 409.9
Adjustments to Reconcile Net (Loss) Income to Net Cash (Used in) Provided by Operating Activities:
Net Realized Gain on Sale of Investments	(4.3)	(64.8)	(38.1)
Impairment Losses	25.8	11.0	19.5
Depreciation and Amortization of Property, Equipment and Software	50.5	46.3	36.2
Amortization of Intangible Assets Acquired	20.4	53.5	18.8
Settlement Costs Related to Defined Benefit Pension Plan	0.0	0.0	64.1
Loss from Early Extinguishment of Debt	3.7	0.0	0.0
Change in Accumulated Undistributed Earnings of Equity Method Limited Liability Investments	(9.5)	(33.5)	(4.0)
Decrease (Increase) in Value of Equity and Convertible Securities	79.9	(114.6)	(72.1)
Changes in:
Receivables from Policyholders	129.4	(75.2)	(77.4)
Reinsurance Recoverables	(1.9)	20.6	16.8
Deferred Policy Acquisition Costs	13.8	(88.3)	(52.3)
Insurance Reserves	45.4	623.1	38.3
Unearned Premiums	(183.5)	105.9	69.6
Income Taxes	(87.5)	(163.1)	46.5
Other Assets and Liabilities	(11.2)	89.1	(27.8)
Net Cash (Used in) Provided by Operating Activities	(210.3)	350.7	448.0
Cash Flows from Investing Activities:
Proceeds from the Sales, Calls and Maturities of Fixed Maturities	1,295.5	1,388.9	972.4
Equity Securities	536.0	316.6	434.4
Real Estate Investments	0.0	8.0	5.4
Mortgage Loans	91.3	70.8	25.5
Other Investments	52.1	47.5	45.2
Fixed Maturities	(1,815.8)	(1,825.4)	(1,293.3)
Equity Securities	(58.9)	(124.3)	(319.1)
Real Estate Investments	(3.1)	(5.1)	(0.5)
Corporate-Owned Life Insurance	(110.0)	(100.0)	(100.0)
Mortgage Loans	(81.1)	(119.9)	(52.7)
Other Investments	(13.0)	(104.9)	(43.5)
Net Sales (Purchases) of Short-term Investments	6.1	687.2	(390.8)
Acquisition of Business, Net of Cash Acquired	0.0	(316.6)	0.0
Sale of Reserve National, Net of Cash Disposed	14.8	0.0	0.0
Acquisition of Software and Long-lived Assets	(30.8)	(57.8)	(53.4)
Other	8.5	16.8	13.4
Net Cash Used in Investing Activities	(108.4)	(118.2)	(757.0)
Cash Flows from Financing Activities:
Repayments of Long-term Debt	(280.0)	(50.0)	0.0
Proceeds from Issuance of 5.875% Fixed-Rate Reset Junior Subordinated Debentures Due 2062	145.6	0.0	0.0
Proceeds from Policyholder Contract Obligations	335.5	386.8	467.0
Repayment of Policyholder Contract Obligations	(138.2)	(394.0)	(304.8)
Proceeds from Shares Issued under Employee Stock Purchase Plan	4.9	5.4	4.4
Common Stock Repurchases	0.0	(161.7)	(110.4)
Dividends Paid	(79.7)	(80.6)	(78.9)
Other	0.6	3.7	5.4
Net Cash Provided by (Used in) Financing Activities	382.9	(290.4)	378.3
Net increase (decrease) in cash	64.2	(57.9)	69.3
Cash, Beginning of Year	148.2	206.1	136.8
Cash, End of Year	212.4	148.2	206.1
Senior Notes, 3.800 Percent Due February 23, 2032
Cash Flows from Financing Activities:
Proceeds from Issuance of 3.800% Senior Notes due February 23, 2032	396.3	0.0	0.0
Issue Fess	(1.2)	0.0	0.0
5.875% Fixed-Rate Reset Junior Subordinated Debentures due 2062
Cash Flows from Financing Activities:
Issue Fess	(0.9)	0.0	0.0
Senior Notes, 2.400 Percent Due September 30, 2030
Cash Flows from Financing Activities:
Proceeds from Issuance of 3.800% Senior Notes due February 23, 2032	0.0	0.0	396.8
Issue Fess	0.0	0.0	(1.2)
Alternative Energy Partnership Investments
Adjustments to Reconcile Net (Loss) Income to Net Cash (Used in) Provided by Operating Activities:
Loss from Change in Value of Alternative Energy Partnership Investments	$ 19.9	$ 61.2	$ 0.0