Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash Flows from Operating Activities:
Net Income	$ 409.9	$ 531.1	$ 190.1
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities:
Net Realized Investment (Gains) Losses	(38.1)	(41.9)	(26.4)
Impairment Losses	19.5	13.8	4.5
Depreciation and Amortization of Property, Equipment and Software	36.2	32.8	15.6
Amortization of Intangibles Assets Acquired	18.8	29.7	156.3
Settlement Costs Related to Defined Benefit Pension Plan	64.1	0.0
Contribution to Defined Benefit Pension Plan	0.0	(55.3)	(5.1)
Loss from Early Extinguishment of Debt	0.0	5.8	0.0
Change in Accumulated Undistributed Earnings of Equity Method Limited Liability Investments	(4.0)	10.9	2.9
Decrease (Increase) in Value of Equity and Convertible Securities at Fair Value	(72.1)	(138.9)	64.3
Changes in:
Receivables from Policyholders	(77.4)	(110.1)	(57.6)
Reinsurance Recoverables	16.8	35.6	(46.7)
Deferred Policy Acquisition Costs	(52.3)	(66.9)	(104.6)
Insurance Reserves	38.3	102.3	183.2
Unearned Premiums	69.6	121.2	54.7
Income Taxes	46.5	58.8	13.1
Other Assets and Liabilities	(27.8)	5.4	94.9
Net Cash Provided by Operating Activities	448.0	534.3	539.2
Cash Flows from Investing Activities:
Proceeds from Sales, Calls and Maturities of Fixed Maturities	972.4	1,229.1	2,643.3
Proceeds from the Sales or Paydowns of Investments:
Equity Securities	434.4	217.3	351.9
Real Estate Investments	5.4	0.0	0.0
Mortgage Loans	25.5	17.2	0.0
Other Investments	45.2	29.5	14.1
Purchases of Investments:
Fixed Maturities	(1,293.3)	(1,284.9)	(2,413.2)
Equity Securities	(319.1)	(307.0)	(478.5)
Real Estate Investments	(0.5)	(1.4)	(1.5)
Corporate-owned Life Insurance	(100.0)	(150.0)	0.0
Mortgage Loans	(52.7)	(44.5)	0.0
Other Investments	(43.5)	(73.8)	(45.1)
Net Sales (Purchases) of Short-term Investments	(390.8)	(176.0)	52.7
Acquisition of Business, Net of Cash Acquired	0.0	0.0	(560.6)
Acquisition of Software and Long-lived Assets	(53.4)	(84.0)	(65.3)
Other	13.4	(4.9)	4.6
Net Cash Provided by (Used in) Investing Activities	(757.0)	(633.4)	(497.6)
Cash Flows from Financing Activities:
Net Proceeds from Issuance of Long-term Debt	395.6	49.9	249.4
Repayment of Long-term Debt	0.0	(185.0)	(215.0)
Proceeds from Policyholder Obligations	467.0	615.8	11.4
Repayment of Policyholder Obligations	(304.8)	(383.6)	(2.5)
Proceeds from Issuance of Common Stock, Net of Transaction Costs	0.0	127.5	0.0
Proceeds from Shares Issued under Employee Stock Purchase Plan	4.4	1.6	0.0
Common Stock Repurchases	(110.4)	0.0	0.0
Dividends and Dividend Equivalents Paid	(78.9)	(67.8)	(56.4)
Other	5.4	2.4	0.9
Net Cash Provided by (Used in) Financing Activities	378.3	160.8	(12.2)
Increase in Cash	69.3	61.7	29.4
Cash, Beginning of Year	136.8	75.1	45.7
Cash, End of Period	$ 206.1	$ 136.8	$ 75.1