Ceded Reinsurance (Schedule Of Reinsurance Recoverables By Credit Rating) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Ceded Credit Risk [Line Items]
Ceded, OSLR	$ 196,484	$ 206,130
Ceded, IBNR	806,435	721,458
Reinsurance Recoverable on Paid, Losses	54,040
A.M. Best Rating A++ [Member]
Ceded Credit Risk [Line Items]
Ceded, OSLR	32,306
Ceded, IBNR	48,351
Reinsurance Recoverable on Paid, Losses	1,115
A.M. Best Rating A+ [Member]
Ceded Credit Risk [Line Items]
Ceded, OSLR	63,414
Ceded, IBNR	278,100
Reinsurance Recoverable on Paid, Losses	15,391
A.M. Best Rating A [Member]
Ceded Credit Risk [Line Items]
Ceded, OSLR	90,057
Ceded, IBNR	467,892
Reinsurance Recoverable on Paid, Losses	32,824
A.M. Best Rating A- [Member]
Ceded Credit Risk [Line Items]
Ceded, OSLR	5,886
Ceded, IBNR	2,371
Reinsurance Recoverable on Paid, Losses	4,219
A.M. Best Rating B++ [Member]
Ceded Credit Risk [Line Items]
Ceded, OSLR	242
Ceded, IBNR	5,363
Reinsurance Recoverable on Paid, Losses	276
AM Best Rating NR [Member]
Ceded Credit Risk [Line Items]
Ceded, OSLR	4,579
Ceded, IBNR	4,358
Reinsurance Recoverable on Paid, Losses	$ 215