CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash Flows from Operating Activities
Net Income	$ 931.4	$ 867.1	$ 402.1
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities
Change in Receivables	(167.3)	29.3	(21.5)
Change in Deferred Acquisition Costs	(99.4)	(87.4)	(83.2)
Change in Insurance Reserves and Liabilities	368.2	293.9	972.2
Change in Income Taxes	34.7	180.5	(18.6)
Change in Other Accrued Liabilities	125.8	20.0	105.2
Non-cash Components of Net Investment Income	(187.7)	(194.1)	(195.7)
Net Realized Investment (Gain) Loss	(24.2)	43.8	(16.1)
Depreciation	101.7	99.5	87.9
Other, Net	32.9	39.5	(8.7)
Net Cash Provided by Operating Activities	1,116.1	1,292.1	1,223.6
Cash Flows from Investing Activities
Proceeds from Sales of Fixed Maturity Securities	911.5	880.1	450.1
Proceeds from Maturities of Fixed Maturity Securities	2,197.8	2,417.0	1,819.4
Proceeds from Sales and Maturities of Other Investments	336.8	347.0	235.0
Purchase of Fixed Maturity Securities	(3,362.8)	(4,305.3)	(2,918.4)
Purchase of Other Investments	(576.0)	(409.5)	(285.2)
Net Sales (Purchases) of Short-term Investments	6.3	170.6	(69.3)
Net Increase (Decrease) in Payables for Collateral on Investments	(9.4)	341.6	(3.8)
Acquisition of Business (Net of Cash Acquired)	(129.2)	(54.3)	0.0
Net Purchases of Property and Equipment	(85.0)	(100.2)	(114.5)
Other, Net	0.0	0.0	0.1
Net Cash Used by Investing Activities	(710.0)	(713.0)	(886.6)
Cash Flows from Financing Activities
Issuance of Long-term Debt	609.1	271.4	347.2
Long-term Debt Repayment	(414.0)	(226.3)	(186.6)
Cost Related to Early Retirement of Debt	0.0	0.0	(13.2)
Issuance of Common Stock	8.5	6.4	12.3
Repurchase of Common Stock	(405.2)	(417.9)	(306.0)
Dividends Paid to Stockholders	(182.6)	(174.2)	(159.4)
Other, Net	(34.4)	(28.1)	(22.9)
Net Cash Used by Financing Activities	(418.6)	(568.7)	(328.6)
Net Increase (Decrease) in Cash and Bank Deposits	(12.5)	10.4	8.4
Cash and Bank Deposits at Beginning of Year	112.9	102.5	94.1
Cash and Bank Deposits at End of Year	$ 100.4	$ 112.9	$ 102.5