SCHEDULE I SUMMARY OF INVESTMENTS-OTHER THAN INVESTMENTS IN RELATED PARTIES (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014
Summary of investments other than investments in related parties
Cost	$ 6,499.7
Carrying Value	6,863.1
Fair Value	6,863.1
Fixed maturity investments
Summary of investments other than investments in related parties
Cost	4,653.3
Carrying Value	4,784.3
Fair Value	4,784.3
US Government and agency obligations
Summary of investments other than investments in related parties
Cost	184.7
Carrying Value	188.1
Fair Value	188.1
Debt securities issued by corporations
Summary of investments other than investments in related parties
Cost	2,221.3
Carrying Value	2,311.2
Fair Value	2,311.2
Municipal obligations
Summary of investments other than investments in related parties
Cost	1,811.1
Carrying Value	1,840.9
Fair Value	1,840.9
Mortgage-backed and asset-backed securities
Summary of investments other than investments in related parties
Cost	82.0
Carrying Value	83.2
Fair Value	83.2
Foreign government, agency and provincial obligations
Summary of investments other than investments in related parties
Cost	274.6
Carrying Value	275.1
Fair Value	275.1
Redeemable preferred stocks
Summary of investments other than investments in related parties
Cost	79.6
Carrying Value	85.8
Fair Value	85.8
Short-term investments
Summary of investments other than investments in related parties
Cost	871.7
Carrying Value	871.7
Fair Value	871.7
Common equity securities
Summary of investments other than investments in related parties
Cost	633.6
Carrying Value	801.6
Fair Value	801.6
Banks, trust and insurance companies
Summary of investments other than investments in related parties
Cost	167.0
Carrying Value	233.9
Fair Value	233.9
Public utilities
Summary of investments other than investments in related parties
Cost	7.9
Carrying Value	9.5
Fair Value	9.5
Industrial, miscellaneous and other
Summary of investments other than investments in related parties
Cost	458.7
Carrying Value	558.2
Fair Value	558.2
Convertible fixed maturity and preferred investments
Summary of investments other than investments in related parties
Cost	19.1
Carrying Value	20.5
Fair Value	20.5
Other long-term investments
Summary of investments other than investments in related parties
Cost	322.0
Carrying Value	385.0
Fair Value	385.0
Other long-term investments
Summary of investments other than investments in related parties
Equity Method Investment, Carrying Value	22.5
Carrying value of investment accounted for using the equity method	$ 23.2

Fair value portion of investments accounted under the equity method.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 323

-SubTopic 10

-Section 25

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6903542&loc=d3e32014-111567

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- Definition

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.

+ References

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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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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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.

+ References

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