Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Operating Activities:
Net Income	$ 190.1	$ 277.4
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities:
Increase in Deferred Policy Acquisition Costs	(23.1)	(51.1)
Amortization of Intangible Assets Acquired	9.5	16.7
Equity in Earnings of Equity Method Limited Liability Investments	10.9	(1.0)
Distribution of Accumulated Earnings of Equity Method Limited Liability Investments	0.0	6.3
Decrease (Increase) in Value of Equity and Convertible Securities at Fair Value	46.2	(89.9)
Amortization of Investment Securities and Depreciation of Investment Real Estate	1.0	5.9
Net Realized Gains on Sales of Investments	(28.2)	(37.4)
Impairment Losses	19.0	10.3
Depreciation and Amortization of Property, Equipment and Software	16.8	14.8
Increase in Receivables	(36.3)	(95.0)
Increase (Decrease) in Insurance Reserves	(96.7)	56.2
Increase in Unearned Premiums	97.1	121.3
Change in Income Taxes	46.5	23.2
Change in Accrued Expenses and Other Liabilities	10.7	(22.5)
Other, Net	0.3	1.3
Net Cash Provided by Operating Activities	263.8	236.5
Investing Activities:
Sales, Paydowns and Maturities of Fixed Maturities	482.5	959.0
Purchases of Fixed Maturities	(832.2)	(721.5)
Sales of Equity and Convertible Securities	382.6	82.7
Purchases of Equity and Convertible Securities	(309.2)	(231.7)
Acquisition and Improvements of Investment Real Estate	0.1	0.6
Sales of Investment Real Estate	5.4	0.0
Sale of and Return of Investment of Equity Method Limited Liability Investments	12.0	13.7
Acquisitions of Equity Method Limited Liability Investments	(12.4)	(51.6)
Decrease (Increase) in Short-term Investments	326.7	(353.4)
Acquisition of Mortgage Loans	10.5	0.0
Paydowns of Mortgage Loans	13.1	0.0
Increase in Other Investments	0.1	(29.2)
Purchases of Corporate-owned Life Insurance	(100.0)	(50.0)
Acquisition of Software and Long-lived Assets	(39.4)	(30.7)
Other, Net	4.6	(0.3)
Net Cash Provided (Used) by Investing Activities	(76.8)	(413.6)
Financing Activities:
Repayment of Long-term Debt	0.0	(35.0)
Proceeds from Policyholder Contract Liabilities	322.9	259.0
Repayment of Policyholder Contract Liabilities	(112.8)	(113.9)
Proceeds from Issuance of Common Stock, Net of Transaction Costs	0.0	127.5
Common Stock Repurchases	(110.4)	0.0
Dividends and Dividend Equivalents Paid	(39.7)	(32.8)
Proceeds from Shares Issued under Employee Stock Purchase Plan	1.9	0.0
Cash Exercise of Stock Options	3.6	2.0
Other, Net	0.0	(0.4)
Net Cash Provided by Financing Activities	65.5	206.4
Increase in Cash	252.5	29.3
Cash, Beginning of Year	136.8	75.1
Cash, End of Period	$ 389.3	$ 104.4