Reserve For Losses And Loss Expenses (Schedule Of Reconciliation Of Unpaid Losses And Loss Expenses) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Insurance Loss Reserves [Abstract]
Gross liability at beginning of year	$ 5,881,165	$ 5,766,529
Reinsurance recoverable at beginning of year	(1,340,256)us-gaap_ReinsuranceRecoverables	(1,234,504)us-gaap_ReinsuranceRecoverables
Net liability at beginning of year	4,540,909	4,532,025
Net losses incurred related to:
Current year	388,817	324,147
Prior years	(63,641)	(48,861)
Total incurred	325,176	275,286
Net paid losses related to:
Current year	6,557	3,743
Prior years	293,098	228,594
Total paid	299,655	232,337
Foreign exchange revaluation	(11,631)	1,299
Net liability at end of year	4,554,799	4,576,273
Reinsurance recoverable at end of year	1,350,311us-gaap_ReinsuranceRecoverables	1,280,525us-gaap_ReinsuranceRecoverables
Gross liability at end of year	$ 5,905,110	$ 5,856,798

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The amount needed to reflect the estimated ultimate cost of settling claims relating to insured events that have occurred on or before the balance sheet date, whether or not reported to the insurer at that date.

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- Definition

Amount of payments to settle claims incurred in the current period and related claims settlement costs.

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- Definition

Amount of payments to settle claims incurred in prior periods and related claims settlement costs.

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- Definition

Amount of increase (decrease) in the cost of settling unpaid claims after deduction of reinsurance recoveries related to foreign currency exchange rate changes. Includes, but is not limited to, claims which have been incurred but not reported.

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No definition available.

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

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Liability as of the balance sheet date for amounts representing estimated cost of settling unpaid claims under the terms of the underlying insurance policies, less estimated reinsurance recoveries on such claims. This includes an estimate for claims which have been incurred but not reported. Claim adjustment expenses represent the costs estimated to be incurred in the settlement of unpaid claims.

+ 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)

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-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 13

-Subparagraph a

-Article 7

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Amount of payments to settle insured claims and pay costs incurred in the claims settlement process.

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

-Publisher FASB

-Name Accounting Standards Codification

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-SubTopic 10

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Amount after valuation allowance recoverable including premium paid under reinsurance contracts. Examples include, but are not limited to, settled and unsettled claims, incurred but not reported losses, loss adjustment expense, premium paid, policy benefits and policy reserves.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

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- Definition

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

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