CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash Flows from Operating Activities
Net Income	$ 867.1	$ 402.1	$ 847.0
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities
Change in Receivables	29.3	(21.5)	(196.7)
Change in Deferred Acquisition Costs	(87.4)	(83.2)	(47.9)
Change in Insurance Reserves and Liabilities	293.9	972.2	572.5
Change in Income Taxes	180.5	(18.6)	(23.5)
Change in Other Accrued Liabilities	20.0	105.2	21.2
Non-cash Components of Net Investment Income	(194.1)	(195.7)	(226.3)
Net Realized Investment (Gain) Loss	43.8	(16.1)	(6.8)
Depreciation	99.5	87.9	84.8
Other, Net	39.5	(8.7)	7.2
Net Cash Provided by Operating Activities	1,292.1	1,223.6	1,031.5
Cash Flows from Investing Activities
Proceeds from Sales of Fixed Maturity Securities	880.1	450.1	1,040.5
Proceeds from Maturities of Fixed Maturity Securities	2,417.0	1,819.4	2,146.4
Proceeds from Sales and Maturities of Other Investments	347.0	235.0	243.4
Purchase of Fixed Maturity Securities	(4,305.3)	(2,918.4)	(3,553.6)
Purchase of Other Investments	(409.5)	(285.2)	(363.7)
Net Sales (Purchases) of Short-term Investments	170.6	(69.3)	551.3
Net Increase (Decrease) in Payables for Collateral on Investments	341.6	(3.8)	(378.2)
Acquisition of Business	(54.3)	0.0	0.0
Net Purchases of Property and Equipment	(100.2)	(114.5)	(105.5)
Other, Net	0.0	0.1	0.2
Net Cash Used by Investing Activities	(713.0)	(886.6)	(419.2)
Cash Flows from Financing Activities
Issuance of Long-term Debt	271.4	347.2	0.0
Long-term Debt Repayments	(226.3)	(186.6)	(116.2)
Cost Related to Early Retirement of Debt	0.0	(13.2)	0.0
Issuance of Common Stock	6.4	12.3	11.4
Repurchase of Common Stock	(417.9)	(306.0)	(317.2)
Dividends Paid to Stockholders	(174.2)	(159.4)	(146.5)
Other, Net	(28.1)	(22.9)	(27.0)
Net Cash Used by Financing Activities	(568.7)	(328.6)	(595.5)
Net Increase in Cash and Bank Deposits	10.4	8.4	16.8
Cash and Bank Deposits at Beginning of Year	102.5	94.1	77.3
Cash and Bank Deposits at End of Year	$ 112.9	$ 102.5	$ 94.1