Fair Value Of Financial Instruments (Schedule Of Fair Value Measurement Using Significant Unobservable Inputs Level Three) (Details) (USD $) In Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Other Invested Assets [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Opening balance	$ 562,267	$ 319,592	$ 347,632	$ 184,725
Total realized and unrealized gains included in net income	3,938	6,093	16,641	8,233
Total realized and unrealized losses included in net income	(38,667)	(3,990)	(38,877)	(2,932)
Change in unrealized gains included in OCI
Change in unrealized losses included in OCI				138,249
Purchases	29,553	6,580	274,893
Sales	(5,017)		(48,215)
Cumulative effect adjustment related to the adoption of ASU 2010-11
Transfers into Level 3
Transfers out of Level 3
Ending balance	552,074	328,275	552,074	328,275
Mortgage-Backed [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Opening balance	216,660	278,789	172,558	253,979
Total realized and unrealized gains included in net income	4,671	6,448	8,480	15,928
Total realized and unrealized losses included in net income	(2,795)	(1,548)	(3,377)	(41)
Change in unrealized gains included in OCI		3,238		2,755
Change in unrealized losses included in OCI		(5,119)
Purchases	46,077	1,115	108,681	122,058
Sales	(7,021)	(58,998)	(50,308)	(178,226)
Cumulative effect adjustment related to the adoption of ASU 2010-11		1,796		1,796
Transfers into Level 3	18,170	6,773	104,255	55,504
Transfers out of Level 3	(28,299)	(3,257)	(92,826)	(44,516)
Ending balance	247,463	229,237	247,463	229,237
Asset-Backed [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Opening balance	113,310	103,555	48,707	104,871
Total realized and unrealized gains included in net income	28	406	115	573
Total realized and unrealized losses included in net income	(1,402)	(257)	(903)
Change in unrealized gains included in OCI		21		64
Change in unrealized losses included in OCI		(2)
Purchases	328	2,177	115,745	53,358
Sales	(5,708)	(1,803)	(8,933)	(7,049)
Cumulative effect adjustment related to the adoption of ASU 2010-11		(19)		(19)
Transfers into Level 3	1,351	5,294	34,152	56,034
Transfers out of Level 3	(12,300)	(51,680)	(93,276)	(150,140)
Ending balance	$ 95,607	$ 57,692	$ 95,607	$ 57,692

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Fair Value, Measurement with Unobservable Inputs Reconciliation Realized and Unrealized Gains Included in Net Income

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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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Purchases that have taken place during the period in relation to assets measured at fair value and categorized within Level 3 of the fair value hierarchy.

+ References

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Transfers into assets measured at fair value and categorized within Level 3 of the fair value hierarchy that have taken place during the period.

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-Name Accounting Standards Codification

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Transfers out of assets measured at fair value and categorized within Level 3 of the fair value hierarchy that have taken place during the period.

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This element represents an asset measured at fair value using significant unobservable inputs (Level 3) which is required for reconciliation purposes of beginning and ending balances.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 157

-Paragraph 32

-Subparagraph c

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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