Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Activities:
Net Income	$ 531.1	$ 190.1	$ 120.9
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities:
Increase in Deferred Policy Acquisition Costs	(66.9)	(104.6)	(33.3)
Amortization of Intangible Assets Acquired	29.7	156.3	5.1
Equity in Earnings of Equity Method Limited Liability Investments	(1.0)	(11.0)	(24.8)
Contribution to Defined Benefit Pension Plan	(55.3)	(5.1)	0.0
Distribution of Accumulated Earnings of Equity Method Limited Liability Investments	11.9	13.9	19.6
Decrease (Increase) in Value of Fair Value Option Investments reported in Investment Income	0.0	0.0	(1.3)
Decrease (Increase) in Value of Equity and Convertible Securities at Fair Value	(138.9)	64.3	0.0
Amortization of Investment Securities and Depreciation of Investment Real Estate	0.5	7.7	16.7
Net Realized Gains on Sales of Investments	(41.9)	(26.4)	(56.5)
Net Impairment Losses Recognized in Earnings	13.8	4.5	14.3
Loss from Early Extinguishment of Debt	5.8	0.0	0.0
Depreciation and Amortization of Property, Equipment and Software	32.8	15.6	13.1
Increase in Receivables	(84.3)	(80.7)	(29.2)
Increase in Insurance Reserves	102.3	183.2	131.1
Increase in Unearned Premiums	121.2	54.7	35.2
Change in Income Taxes	58.8	13.1	28.9
Change in Accrued Expenses and Other Liabilities	(16.0)	49.9	2.9
Other, Net	30.7	13.7	(2.1)
Net Cash Provided by Operating Activities	534.3	539.2	240.6
Investing Activities:
Sales, Paydowns and Maturities of Fixed Maturities	1,229.1	2,643.3	528.2
Purchases of Fixed Maturities	(1,284.9)	(2,413.2)	(710.1)
Sales of Equity and Convertible Securities	217.3	351.9	342.0
Purchases of Equity and Convertible Securities	(307.0)	(478.5)	(342.7)
Acquisition and Improvements of Investment Real Estate	(1.4)	(1.5)	(1.5)
Sales of Investment Real Estate	0.0	0.0	26.7
Sale of and Return of Investment of Equity Method Limited Liability Investments	29.5	14.1	48.1
Acquisitions of Equity Method Limited Liability Investments	(73.7)	(43.1)	(27.9)
Sales of Fair Value Option Investments	0.0	0.0	42.2
Purchases of Fair Value Option Investments	0.0	0.0	(7.0)
Decrease (Increase) in Short-term Investments	(176.0)	52.7	39.4
Acquisition of Business, Net of Cash Acquired	0.0	(560.6)	0.0
Acquisitions of Mortgage Loans	(44.5)	0.0	0.0
Paydowns of Mortgage Loans	17.2	0.0	0.0
Increase in Other Investments	(0.1)	(2.0)	(4.5)
Purchases of Corporate-owned Life Insurance	(150.0)	0.0	0.0
Acquisition of Software and Long-lived Assets	(84.0)	(65.3)	(35.5)
Other, Net	(4.9)	4.6	(2.8)
Net Cash Used by Investing Activities	(633.4)	(497.6)	(105.4)
Financing Activities:
Net Proceeds from Issuance of Long-term Debt	49.9	249.4	200.2
Repayment of Long-term Debt	(185.0)	(215.0)	(360.0)
Proceeds from Policyholder Contract Liabilities	615.8	11.4	3.0
Repayment of Policyholder Contract Liabilities	(383.6)	(2.5)	(2.9)
Proceeds from Issuance of Common Stock, Net of Transaction Costs	127.5	0.0	0.0
Dividends and Dividend Equivalents Paid	(67.8)	(56.4)	(49.5)
Proceeds from Shares Issued under Employee Stock Purchase Plan	1.6	0.0	0.0
Cash Exercise of Stock Options	2.4	0.9	4.0
Net Cash Provided (Used) by Financing Activities	160.8	(12.2)	(205.2)
Increase (Decrease) in Cash	61.7	29.4	(70.0)
Cash, Beginning of Year	75.1	45.7	115.7
Cash, End of Year	$ 136.8	$ 75.1	$ 45.7