CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Cash Flows from Operating Activities
Net Income	$ 1,779.1	$ 1,283.8	$ 1,407.2
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities
Change in Receivables	623.9	602.7	590.6
Change in Deferred Acquisition Costs	(130.5)	(150.8)	(135.8)
Change in Insurance Liabilities	(780.9)	(313.2)	(244.7)
Change in Income Taxes	97.6	(84.3)	(31.3)
Change in Other Accrued Liabilities	(32.3)	(74.8)	(113.9)
Non-cash Components of Net Investment Income	(248.9)	(240.3)	(247.0)
Net Investment Loss	34.6	36.0	15.7
Depreciation	116.1	108.8	110.5
Amortization of the Cost of Reinsurance	41.4	44.1	50.3
Other, Net	13.1	(9.2)	17.1
Net Cash Provided by Operating Activities	1,513.2	1,202.8	1,418.7
Cash Flows from Investing Activities
Proceeds from Sales of Fixed Maturity Securities	877.3	1,062.7	559.5
Proceeds from Maturities of Fixed Maturity Securities	1,483.0	1,578.1	1,532.5
Proceeds from Sales and Maturities of Other Investments	332.1	360.0	445.9
Purchase of Fixed Maturity Securities	(2,001.7)	(2,991.4)	(2,835.3)
Purchase of Other Investments	(319.1)	(361.2)	(482.9)
Net Purchases of Short-term Investments	(842.1)	(141.0)	(22.6)
Net Increase (Decrease) in Payables for Collateral on Investments	251.8	(98.3)	(50.8)
Net Purchases of Property and Equipment	(125.7)	(134.8)	(102.2)
Net Cash Used by Investing Activities	(344.4)	(725.9)	(955.9)
Cash Flows from Financing Activities
Short-term Debt Repayment	0.0	(2.0)	0.0
Issuance of Long-term Debt	391.6	0.0	349.2
Long-term Debt Repayment	(350.0)	0.0	(364.0)
Cost Related to Early Retirement of Debt	0.0	0.0	3.6
Issuance of Common Stock	6.0	5.2	4.0
Repurchase of Common Stock	(972.9)	(250.1)	(200.1)
Dividends Paid to Stockholders	(296.5)	(277.1)	(254.2)
Proceeds from Policyholder Account Deposits	133.2	143.4	119.8
Payments for Policyholder Account Withdrawals	(82.7)	(87.0)	(72.0)
Cash Received Related to Active Life Volatility Cover Agreement	26.7	18.6	5.2
Other, Net	(7.4)	(1.1)	(2.9)
Net Cash Used by Financing Activities	(1,152.0)	(450.1)	(418.6)
Net Increase (Decrease) in Cash and Bank Deposits	16.8	26.8	44.2
Cash and Bank Deposits at Beginning of Year	146.0	119.2	75.0
Cash and Bank Deposits at End of Year	$ 162.8	$ 146.0	$ 119.2