Segment Reporting (Schedule Of Underwriting Results For Operating Segments) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Segment Reporting Information [Line Items]
Premiums earned	$ 521,062us-gaap_PremiumsEarnedNet	$ 470,445us-gaap_PremiumsEarnedNet
Incurred losses and LAE	308,880	278,046
Commission and brokerage	96,531us-gaap_SellingAndMarketingExpense	76,094us-gaap_SellingAndMarketingExpense
Other underwriting expenses	48,543us-gaap_OtherUnderwritingExpense	39,251us-gaap_OtherUnderwritingExpense
Underwriting gain (loss)	67,108us-gaap_UnderwritingIncomeLoss	77,054us-gaap_UnderwritingIncomeLoss
U.S. Reinsurance [Member]
Segment Reporting Information [Line Items]
Gross written premiums	562,647	530,301
Net written premiums	240,694	251,521
Premiums earned	255,412	218,191
Incurred losses and LAE	111,455	115,984
Commission and brokerage	58,364	40,136
Other underwriting expenses	11,529	9,482
Underwriting gain (loss)	74,064	52,589
International [Member]
Segment Reporting Information [Line Items]
Gross written premiums	333,615	328,878
Net written premiums	121,681	141,457
Premiums earned	140,699	145,004
Incurred losses and LAE	101,445	83,575
Commission and brokerage	33,999	29,169
Other underwriting expenses	8,115	7,837
Underwriting gain (loss)	(2,860)	24,423
Insurance [Member]
Segment Reporting Information [Line Items]
Gross written premiums	330,501	225,276
Net written premiums	146,052	106,726
Premiums earned	124,951	107,250
Incurred losses and LAE	95,980	78,487
Commission and brokerage	4,168	6,789
Other underwriting expenses	28,899	21,932
Underwriting gain (loss)	$ (4,096)	$ 42

Amount, before premiums ceded to other entities and premiums assumed by the entity, of premiums written.

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- Definition

Costs incurred during the period, such as those relating to general administration and policy maintenance that do not vary with and are not primarily related to the acquisition or renewal of insurance contracts.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 7

-Article 7

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

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-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-04.7)

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-Topic 944

-SubTopic 720

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- Definition

Amount, after effects of policies assumed or ceded, of expense related to the provision for policy benefits and costs incurred.

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

-Publisher FASB

-Name Accounting Standards Codification

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-Section S99

-Paragraph 1

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-Topic 944

-SubTopic 20

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-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6480758&loc=d3e6811-158387

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- Definition

Amount, after premiums ceded to other entities and premiums assumed by the entity, of premiums earned.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 17

-Article 12

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 235

-Section S99

-Paragraph 2

-Subparagraph (SX 210.12-17)

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-Publisher SEC

-Name Regulation S-X (SX)

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

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-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-04.13(c))

-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

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- Definition

Amount, after premiums ceded to other entities and premiums assumed by the entity, of premiums written.

+ References

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- Definition

The aggregate total amount of expenses directly related to the marketing or selling of products or services.

+ References

No definition available.

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- Definition

The difference between the price paid by the public and the contract price less the related expenses. A broker-dealer may underwrite a security offering by contracting to buy the issue either at a fixed price or a price based on selling the offering on a best-effort basis.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-04.13(b))

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 940

-SubTopic 605

-Section 05

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6476344&loc=d3e44274-110985

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