Amount after valuation allowance of reinsurance recoverables on paid losses.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 310
-Section 45
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6485522&loc=d3e21412-158489

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- Definition

Amount after valuation allowance of reinsurance recoverables for losses reported to the ceding insurer but not yet paid, amounts expected of incurred losses and settlement expenses, which have not yet been reported to the ceding insurer.

+ References

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- Definition

Stated amount that is the upper retention limit per entity policy.

+ References

No definition available.

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- Definition

Amount of risk reinsured in excess of stated retention per company policy.

+ References

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

Percentage of risk reinsured on insurance products per entity policy.

+ References

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- Definition

Represents the percentage ceded under quota share reinsurance agreement.

+ References

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- Definition

Reinsurance Retention Policy Excess Retention Amount Reinsured Net Of Participation

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Third Party Reinsurance (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Mar. 31, 2016	Sep. 30, 2016	Dec. 31, 2015
Reinsurance Retention Policy [Line Items]
Reinsurance recoverable on paid losses		$ 16.4	$ 7.5
Reinsurance recoverable on unpaid losses		169.4	186.0
OneBeacon [Member]
Reinsurance Retention Policy [Line Items]
Reinsurance recoverable on paid losses		16.4	7.5
Reinsurance recoverable on unpaid losses		$ 169.4	$ 186.0
OneBeacon [Member]
Reinsurance Retention Policy [Line Items]
Percentage of Quota Share Reinsurance Agreement	50.00%
Property Catastrophe Program [Member] \| OneBeacon [Member]
Reinsurance Retention Policy [Line Items]
Percentage of par value of policy reinsured		100.00%
Reinsurance Retention Policy Excess Retention Amount Reinsured Net Of Participation		$ 110.0
Property Catastrophe Program [Member] \| Minimum \| OneBeacon [Member]
Reinsurance Retention Policy [Line Items]
Reinsurance Retention Policy, Amount Retained		20.0
Property Catastrophe Program [Member] \| Maximum [Member] \| OneBeacon [Member]
Reinsurance Retention Policy [Line Items]
Reinsurance Retention Policy, Excess Retention, Amount Reinsured		$ 130.0