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Reserve for Losses and Loss Expenses (Exposure to Environmental Claims) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Liability for Claims and Claims Adjustment Expense [Line Items]
Losses and Loss expense reserves, Gross	$ 30,411	$ 30,653	$ 32,764	$ 35,575
Liability for Asbestos and Environmental Claims, Net	23,161	22,994	25,167	27,769
Asbestos [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Losses and Loss expense reserves, Gross	8,024	8,751	8,897	9,170
Liability for Asbestos and Environmental Claims, Net	6,793	$ 7,314	$ 7,518	$ 7,791
Landfill Sites Related Claims [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Losses and Loss expense reserves, Gross	13,100
Liability for Asbestos and Environmental Claims, Net	8,300
Leaking Underground Storage Tanks Claims [Member]
Liability for Claims and Claims Adjustment Expense [Line Items]
Losses and Loss expense reserves, Gross	9,300
Liability for Asbestos and Environmental Claims, Net	$ 8,100

X

- Definition

Carrying amount as of the balance sheet date of reserves for the costs of settling insured claims and costs incurred in the claims settlement process attributable to asbestos and environmental claims, before estimated recoveries from reinsurers.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6482485&loc=d3e14764-158437

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- Definition

Carrying amount as of the balance sheet date of reserves for the costs of settling insured claims and costs incurred in the claims settlement process attributable to asbestos and environmental claims, net of estimated reinsurance recoveries.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6482485&loc=d3e14764-158437

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- Definition

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+ References

No definition available.

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