Fair Value Of Financial Instruments (Schedule Of Fair Value Measurement Using Significant Unobservable Inputs Level Three) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Asset-Backed [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Opening balance	$ 48,707	$ 104,871
Total realized and unrealized gains included in net income	90	818
Total realized and unrealized losses included in net income	(452)	(233)
Change in unrealized gains included in OCI		70
Change in unrealized losses included in OCI		(6)
Purchases	24,056	64,275
Sales	(3,204)	(21,944)
Cumulative effect adjustment related to the adoption of ASU 2010-11		(19)
Transfers into Level 3	30,536	56,033
Transfers out of Level 3	(4,988)	(155,158)
Ending balance	94,745	48,707
Mortgage-Backed [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Transfers out of Level 3		(44,515)
Other Invested Assets [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Opening balance	347,632	184,725
Total realized and unrealized gains included in net income	22,059	18,368
Total realized and unrealized losses included in net income	(25,679)	(965)
Purchases	311,185	155,504
Sales	(114,788)	(10,000)
Ending balance	540,409	347,632
Mortgage-Backed [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Opening balance	172,559	253,979
Total realized and unrealized gains included in net income	4,472	24,983
Total realized and unrealized losses included in net income	(6,603)	(9,247)
Change in unrealized gains included in OCI		5,781
Change in unrealized losses included in OCI		(3,026)
Purchases	101,302	138,995
Sales	(44,549)	(252,769)
Cumulative effect adjustment related to the adoption of ASU 2010-11		1,796
Transfers into Level 3	63,717	56,582
Transfers out of Level 3	(41,694)	(44,515)
Ending balance	$ 249,204	$ 172,559