Segment Reporting (Schedule Of Underwriting Results For Operating Segments) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Segment Reporting Information [Line Items]
Premiums earned	$ 569,597	$ 523,521	$ 1,560,778	$ 1,461,549
Incurred losses and LAE	380,580	307,121	980,143	909,661
Commission and brokerage	79,168	71,560	240,584	215,047
Other underwriting expenses	50,623	48,945	137,032	136,751
Underwriting gain (loss)	59,226	95,895	203,019	200,090
U.S. Reinsurance [Member]
Segment Reporting Information [Line Items]
Gross written premiums	679,904	532,324	1,663,320	1,385,482
Net written premiums	304,442	257,085	771,054	690,547
Premiums earned	275,521	225,231	739,977	621,430
Incurred losses and LAE	125,475	102,506	371,135	340,799
Commission and brokerage	51,231	38,275	144,747	114,945
Other underwriting expenses	12,119	12,013	33,054	32,541
Underwriting gain (loss)	86,696	72,437	191,041	133,145
International [Member]
Segment Reporting Information [Line Items]
Gross written premiums	419,457	339,739	1,214,343	994,526
Net written premiums	157,932	149,812	446,599	446,158
Premiums earned	145,662	140,854	438,394	433,872
Incurred losses and LAE	113,703	90,743	286,166	262,709
Commission and brokerage	23,767	27,932	80,348	87,195
Other underwriting expenses	8,759	8,722	24,689	24,319
Underwriting gain (loss)	(567)	13,457	47,191	59,649
Insurance [Member]
Segment Reporting Information [Line Items]
Gross written premiums	354,033	367,465	885,006	923,571
Net written premiums	149,542	178,365	386,694	456,334
Premiums earned	148,414	157,436	382,407	406,247
Incurred losses and LAE	141,402	113,872	322,842	306,153
Commission and brokerage	4,170	5,353	15,489	12,907
Other underwriting expenses	29,745	28,210	79,289	79,891
Underwriting gain (loss)	$ (26,903)	$ 10,001	$ (35,213)	$ 7,296