Schedule 2 - Parent Company Financial Statements - Statements of Cash Flows (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating Activities:
Net Income	$ 114.5us-gaap_ProfitLoss	$ 217.7us-gaap_ProfitLoss	$ 103.4us-gaap_ProfitLoss
Adjustment Required to Reconcile Net Income to Net Cash Provided by Operations:
Net Realized (Gains) Losses on Sales of Investments	(39.1)	(99.1)	(65.4)
Net Impairment Losses Recognized in Earnings	15.2	13.9	6.9
Other, Net	16.4	36.1	33.4
Net Cash Provided by Operating Activities	133.6	122.1	65.7
Investing Activities:
Sales, Paydowns and Maturities of Fixed Maturities	573.7	664.4	914.4
Sales of Equity Securities	245.3	182.1	70.8
Sales of Fair Value Option Investments	6.9	0	0
Purchases of Fair Value Option Investments	(60.9)	0	0
Change in Short-term Investments	(63.9)	41.8	(80.0)
Net Cash Provided (Used) by Investing Activities	(104.3)	4.8	(106.2)
Financing Activities:
Cash Dividends Paid	(51.8)us-gaap_PaymentsOfDividendsCommonStock	(54.9)us-gaap_PaymentsOfDividendsCommonStock	(56.9)us-gaap_PaymentsOfDividendsCommonStock
Common Stock Repurchases	(114.0)	(100.4)	(60.7)
Cash Exercise of Stock Options	0.5	1.7	1.3
Net Cash Used by Financing Activities	(19.7)	(156.7)	(114.4)
Increase (Decrease) in Cash	9.6us-gaap_CashPeriodIncreaseDecrease	(29.8)us-gaap_CashPeriodIncreaseDecrease	(154.9)us-gaap_CashPeriodIncreaseDecrease
Cash, Beginning of Year	66.5us-gaap_Cash	96.3us-gaap_Cash	251.2us-gaap_Cash
Cash, End of Year	76.1us-gaap_Cash	66.5us-gaap_Cash	96.3us-gaap_Cash
Parent Company [Member]
Operating Activities:
Net Income	114.5	217.7	103.4
Adjustment Required to Reconcile Net Income to Net Cash Provided by Operations:
Equity in Net Income of Subsidiaries	(147.2)	(256.7)	(137.8)
Cash Dividends from Subsidiaries	159.1	95.0	95.0
Cash Contribution to Defined Benefit Plan	0	(55.0)	0
Net Realized (Gains) Losses on Sales of Investments	0.2	(0.6)	(0.3)
Net Impairment Losses Recognized in Earnings	1.7	0	0
Other, Net	10.5	67.3	8.5
Net Cash Provided by Operating Activities	138.8	67.7	68.8
Investing Activities:
Capital Distribution from Subsidiary	1.1	50.5	20.0
Sales, Paydowns and Maturities of Fixed Maturities	11.5	0	13.1
Sales of Equity Securities	15.1	0	0
Sales of Fair Value Option Investments	6.9	0	0
Purchases of Fair Value Option Investments	(60.9)	0	0
Change in Short-term Investments	(94.3)	52.7	(106.3)
Net Cash Provided (Used) by Investing Activities	(120.6)	103.2	(73.2)
Financing Activities:
Net Proceeds from Issuance of Subordinated Debentures	144.0	0	0
Cash Dividends Paid	(51.8)	(54.9)	(56.9)
Common Stock Repurchases	(114.0)	(100.4)	(60.7)
Cash Exercise of Stock Options	0.5	1.7	1.3
Excess Tax Benefits on Share Based Awards	0.2	1.3	0.5
Net Cash Used by Financing Activities	(21.1)	(152.3)	(115.8)
Increase (Decrease) in Cash	(2.9)	18.6	(120.2)
Cash, Beginning of Year	20.8	2.2	122.4
Cash, End of Year	$ 17.9	$ 20.8	$ 2.2

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