Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	$ 155,985	$ 261	$ 496,362	$ (88,465)
Adjustments to reconcile net income to net cash provided by operating activities:
Decrease (increase) in premiums receivable	(233,296)	(21,017)	(129,749)	(149,561)
Decrease (increase) in funds held by reinsureds, net	2,646	(94,290)	(14,878)	(102,102)
Decrease (increase) in reinsurance receivables	(39,772)	112,376	(9,281)	(243,523)
Decrease (increase) in current income taxes	18,495	16,559	23,123	15,515
Decrease (increase) in deferred tax asset	22,640	(137,225)	136,264	(122,876)
Decrease (increase) in prepaid reinsurance premiums	(66,455)	(33,514)	28,866	28,649
Increase (decrease) in reserve for losses and loss adjustment expenses	(109,811)	(96,587)	(406,946)	489,779
Increase (decrease) in unearned premiums	98,935	29,928	(102,067)	(73,434)
Increase (decrease) in other net payable to reinsurers	220,948	66,568	263,498	155,372
Change in equity adjustments in limited partnerships	(8,800)	(12,190)	(28,850)	(44,544)
Change in other assets and liabilities, net	59,520	28,444	158,864	44,148
Non-cash compensation expense	1,737	1,584	4,981	4,638
Amortization of bond premium (accrual of bond discount)	3,330	(17)	12,939	6,897
Amortization of underwriting discount on senior notes	13	12	38	36
Net realized capital (gains) losses	(95,943)	179,036	(354,673)	206,744
Net cash provided by (used in) operating activities	30,172	39,928	78,491	127,273
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from fixed maturities matured/called - available for sale, at market value	273,497	262,235	648,218	525,768
Proceeds from fixed maturities matured/called - available for sale, at fair value	1,300		1,300	12,775
Proceeds from fixed maturities sold - available for sale, at market value	114,610	255,913	290,911	1,042,803
Proceeds from fixed maturities sold - available for sale, at fair value	11,783	12,512	72,926	62,632
Proceeds from equity securities sold - available for sale, at market value				27,096
Proceeds from equity securities sold - available for sale, at fair value	85,277	61,080	377,157	150,776
Distributions from other invested assets	16,130	13,487	31,513	103,262
Cost of fixed maturities acquired - available for sale, at market value	(404,009)	(285,414)	(1,066,080)	(995,210)
Cost of fixed maturities acquired - available for sale, at fair value	(1,658)	(9,801)	(7,164)	(25,025)
Cost of equity securities acquired - available for sale, at market value				(27,059)
Cost of equity securities acquired - available for sale, at fair value	(107,330)	(340,493)	(288,218)	(679,764)
Cost of other invested assets acquired	(20,065)	(2,393)	(43,831)	(47,471)
Cost of other invested assets acquired, at fair value				(37,611)
Cost of businesses acquired				(63,100)
Net change in short-term investments	(58,681)	29,080	(216,270)	(18,105)
Net change in unsettled securities transactions	33,600	(14,007)	38,712	30,834
Net cash provided by (used in) investing activities	(55,546)	(17,801)	(160,826)	62,601
CASH FLOWS FROM FINANCING ACTIVITIES:
Tax benefit from share-based compensation	(72)	73	81	242
Revolving credit borrowings		(40,000)		(50,000)
Net cash provided by (used in) financing activities	(72)	(39,927)	81	(49,758)
EFFECT OF EXCHANGE RATE CHANGES ON CASH	28,772	(5,553)	43,046	6,804
Net increase (decrease) in cash	3,326	(23,353)	(39,208)	146,920
Cash, beginning of period	305,733	288,365	348,267	118,092
Cash, end of period	309,059	265,012	309,059	265,012
SUPPLEMENTAL CASH FLOW INFORMATION:
Income taxes paid (recovered)	27,119	4,149	36,498	(16,616)
Interest paid	5,202	5,228	30,244	30,269
Non-cash transaction:
Net assets acquired and liabilities assumed from business acquisitions		$ 19,130		$ 19,130