Schedule 1 - Investments Other Than Investments in Related Parties (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Amortized Cost	$ 5,878.3
Amount Carried in Balance Sheet	6,151.3
Fixed Maturities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Amortized Cost	4,370.5
Fair Value	4,575.0
Amount Carried in Balance Sheet	4,575.0
US Government and Government Agencies and Authorities [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Amortized Cost	351.1
Fair Value	362.2
Amount Carried in Balance Sheet	362.2
States and Political Subdivisions [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Amortized Cost	1,327.4
Fair Value	1,361.0
Amount Carried in Balance Sheet	1,361.0
Other Corporate Bonds and Notes [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Amortized Cost	2,685.4
Fair Value	2,844.4
Amount Carried in Balance Sheet	2,844.4
Redeemable Preferred Stocks [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Amortized Cost	6.6
Fair Value	7.4
Amount Carried in Balance Sheet	7.4
Equity Securities, Investment Summary [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Amortized Cost	530.0
Fair Value	598.5
Amount Carried in Balance Sheet	598.5
Preferred Stock [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Amortized Cost	105.5
Fair Value	110.2
Amount Carried in Balance Sheet	110.2
Common Stock [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Amortized Cost	152.2
Fair Value	189.5
Amount Carried in Balance Sheet	189.5
Other Equity Interests [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Amortized Cost	272.3
Fair Value	298.8
Amount Carried in Balance Sheet	298.8
Equity Method Limited Liability Investments at Cost Plus Cumulative Undistributed Earnings [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Amortized Cost	245.1
Amount Carried in Balance Sheet	245.1
Loans, Real Estate and Other Investments [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Amortized Cost	448.0
Amount Carried in Balance Sheet	448.0
Short-term Investments [Member]
Summary of Investments, Other than Investments in Related Parties, Reportable Data [Line Items]
Amortized Cost	284.7
Amount Carried in Balance Sheet	$ 284.7

This element represents the carrying (reported) amount of the entity's investments as of the balance sheet date. This amount may represent the individual investment's or group of similar investments' original cost, fair value, or such other amount at which the investment is shown in the entity's balance sheet.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 15

-Article 12

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 946

-SubTopic 320

-Section S99

-Paragraph 7

-Subparagraph (SX 210.12-15)

-URI http://asc.fasb.org/extlink&oid=6955306&loc=d3e611379-123010

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- Definition

This item represents the original cost of the entity's investments including investments in equity securities and, as to fixed maturities, original cost reduced by repayments and adjusted for amortization of premiums or accrual of discounts.

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- Definition

This item represents the reported amount of the entity's investments measured at fair value. Fair value is the price that would be received to sell an investment in an orderly transaction between market participants at the balance sheet [measurement] date.

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