Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	$ (202,821)	$ 265,397	$ 395,851
Adjustments to reconcile net income to net cash provided by operating activities:
Decrease (increase) in premiums receivable	(214,581)	131,870	(51,103)
Decrease (increase) in funds held by reinsureds, net	(62,082)	(8,910)	31,915
Decrease (increase) in reinsurance receivables	(96,003)	(271,644)	15,207
Decrease (increase) in federal income taxes receivable	79,504	(13,560)	(70,447)
Decrease (increase) in deferred tax asset	(187,967)	28,192	170,490
Decrease (increase) in prepaid reinsurance premiums	3,655	(66,408)	(103,677)
Increase (decrease) in reserve for losses and loss adjustment expenses	674,001	318,301	(175,589)
Increase (decrease) in unearned premiums	(46,182)	40,729	54,760
Increase (decrease) in other net payable to reinsurers	153,508	22,072	62,535
Change in equity adjustments in limited partnerships	(42,047)	(45,463)	28,467
Change in other assets and liabilities, net	69,549	(63,273)	32,904
Non-cash compensation expense	6,166	6,382	5,384
Amortization of bond premium (accrual of bond discount)	10,125	8,614	11,665
Amortization of underwriting discount on senior notes	49	76	192
Realized gain on debt repurchase			(78,271)
Net realized capital (gains) losses	41,116	(65,291)	(56,928)
Net cash provided by (used in) operating activities	185,990	287,084	273,355
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from fixed maturities matured/called - available for sale, at market value	695,921	676,822	445,817
Proceeds from fixed maturities matured/called - available for sale, at fair value	12,775		15,358
Proceeds from fixed maturities sold - available for sale, at market value	1,209,150	953,714	102,396
Proceeds from fixed maturities sold - available for sale, at fair value	65,158	20,237	14,778
Proceeds from equity securities sold - available for sale, at market value	27,096		23,028
Proceeds from equity securities sold - available for sale, at fair value	237,849	230,562	43,483
Proceeds from sale of subsidiary to related party	61,005
Distributions from other invested assets	121,176	60,283	28,460
Cost of fixed maturities acquired - available for sale, at market value	(1,455,940)	(785,831)	(1,152,966)
Cost of fixed maturities acquired - available for sale, at fair value	(27,481)	(134,324)	(27,555)
Cost of equity securities acquired - available for sale, at market value	(27,059)
Cost of equity securities acquired - available for sale, at fair value	(746,604)	(475,047)	(265,272)
Cost of other invested assets acquired	(53,070)	(33,021)	(43,628)
Cost of other invested assets acquired, at fair value	(37,611)	(379,591)	(25,840)
Cost of businesses acquired	(63,100)
Net change in short-term investments	89,735	(254,160)	666,882
Net change in unsettled securities transactions	13,467	(11,773)	6,042
Net cash provided by (used in) investing activities	122,467	(132,129)	(169,017)
CASH FLOWS FROM FINANCING ACTIVITIES:
Tax benefit from share-based compensation	275	200	30
Net cost of senior notes maturing		(200,000)
Revolving credit borrowings	(50,000)	50,000
Net cost of debt repurchase			(83,026)
Net cash provided by (used in) financing activities	(49,725)	(149,800)	(82,996)
EFFECT OF EXCHANGE RATE CHANGES ON CASH	(28,557)	5,457	(6,126)
Net increase (decrease) in cash	230,175	10,612	15,216
Cash, beginning of period	118,092	107,480	92,264
Cash, end of period	348,267	118,092	107,480
SUPPLEMENTAL CASH FLOW INFORMATION:
Income taxes paid (recovered)	(62,137)	(51,360)	30,859
Interest paid	50,091	58,921	71,256
Non-cash transaction:
Net assets acquired and liabilities assumed from business acquisitions	$ 19,130