Catastrophe Reinsurance - Catastrophe Losses and LAE (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Liability for Catastrophe Claims [Line Items]
Catastrophe Losses and LAE	$ 908.3	$ 991.9	$ 1,221.6
Catastrophe Loss and LAE Reserves, (Unfavorable) Favorable Development	57.1	64.6	31.5
Catastrophe [Member]
Liability for Catastrophe Claims [Line Items]
Catastrophe Losses and LAE	83.8	36.2	118.2
Catastrophe Loss and LAE Reserves, (Unfavorable) Favorable Development	(14.7)	(14.5)	(6.3)
Catastrophe [Member] \| Superstorm Sandy [Member]
Liability for Catastrophe Claims [Line Items]
Liability for Catastrophe Claims, Carrying Amount			48.5
Property and Casualty Insurance [Member] \| Catastrophe [Member]
Liability for Catastrophe Claims [Line Items]
Catastrophe Losses and LAE	80.7	34.6	112.1
Catastrophe Loss and LAE Reserves, (Unfavorable) Favorable Development	(15.8)	(12.5)	(6.4)
Life and Health Insurance [Member] \| Catastrophe [Member]
Liability for Catastrophe Claims [Line Items]
Catastrophe Losses and LAE	3.1	1.6	6.1
Catastrophe Loss and LAE Reserves, (Unfavorable) Favorable Development	$ 1.1	$ (2.0)	$ 0.1

The amount of estimated liability as of the balance sheet date for the specific conflagration, earthquake, windstorm, explosion, or similar event.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 40

-Section 50

-Paragraph 3

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Amount of expense for claims incurred and costs incurred in the claim settlement process.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 40

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Amount of expense for claims incurred in prior reporting periods and related claims settlement costs.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 235

-Section S99

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

-Publisher SEC

-Name Regulation S-X (SX)

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