Segment Reporting (Schedule Of Underwriting Results For Operating Segments) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Segment Reporting Information [Line Items]
Premiums earned	$ 427,112	$ 442,862	$ 1,299,293	$ 1,354,305
Incurred losses and LAE	242,877	322,099	786,851	1,187,936
Commission and brokerage	70,464	70,842	251,320	239,659
Other underwriting expenses	45,938	42,708	126,551	120,148
Underwriting gain (loss)	67,833	7,213	134,571	(193,438)
U.S. Reinsurance [Member]
Segment Reporting Information [Line Items]
Gross written premiums	433,494	360,833	938,444	947,155
Net written premiums	219,884	167,469	475,271	486,032
Premiums earned	181,396	167,530	529,409	512,104
Incurred losses and LAE	108,153	97,197	321,397	371,638
Commission and brokerage	40,092	23,298	139,920	106,123
Other underwriting expenses	12,766	10,843	33,541	30,621
Underwriting gain (loss)	20,385	36,192	34,551	3,722
International [Member]
Segment Reporting Information [Line Items]
Gross written premiums	248,459	326,053	878,637	923,649
Net written premiums	105,550	158,038	402,078	457,663
Premiums earned	121,611	151,050	426,419	479,989
Incurred losses and LAE	29,309	104,570	191,837	514,260
Commission and brokerage	19,692	35,686	88,432	105,755
Other underwriting expenses	8,246	7,549	21,532	20,938
Underwriting gain (loss)	64,364	3,245	124,618	(160,964)
Insurance [Member]
Segment Reporting Information [Line Items]
Gross written premiums	328,930	236,294	783,872	750,283
Net written premiums	133,432	114,328	348,328	366,223
Premiums earned	124,105	124,282	343,465	362,212
Incurred losses and LAE	105,415	120,332	273,617	302,038
Commission and brokerage	10,680	11,858	22,968	27,781
Other underwriting expenses	24,926	24,316	71,478	68,589
Underwriting gain (loss)	$ (16,916)	$ (32,224)	$ (24,598)	$ (36,196)
Accident & Health [Member]
Segment Reporting Information [Line Items]
Premiums earned, percentage		2.00%
Specialty Underwriting [Member]
Segment Reporting Information [Line Items]
Premiums earned, percentage		5.00%
Percentage threshold of maximum projected volume of premiums earned		6.00%