Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	$ 798,263	$ 520,329	$ (202,821)
Adjustments to reconcile net income to net cash provided by operating activities:
Decrease (increase) in premiums receivable	(175,854)	(141,501)	(214,581)
Decrease (increase) in funds held by reinsureds, net	(12,075)	(17,897)	(62,082)
Decrease (increase) in reinsurance receivables	25,665	(152,887)	(96,003)
Decrease (increase) in current income taxes	33,760	(22,149)	79,504
Decrease (increase) in deferred tax asset/liability	317,813	146,888	(187,967)
Decrease (increase) in prepaid reinsurance premiums	(118,173)	68,312	3,655
Increase (decrease) in reserve for losses and loss adjustment expenses	(439,560)	(206,435)	674,001
Increase (decrease) in unearned premiums	228,097	(150,747)	(46,182)
Increase (decrease) in other net payable to reinsurers	127,252	270,776	153,508
Increase (decrease) in losses in course of payment	171,829	169,698	(3,440)
Change in equity adjustments in limited partnerships	(35,721)	(38,579)	(42,047)
Distribution of limited partnership income	24,133	19,490	41,249
Change in other assets and liabilities, net	25,049	44,032	72,989
Non-cash compensation expense	7,983	6,803	6,166
Amortization of bond premium (accrual of bond discount)	25,599	19,124	10,125
Amortization of underwriting discount on senior notes	54	52	49
Net realized capital (gains) losses	(723,149)	(391,702)	41,116
Net cash provided by (used in) operating activities	280,965	143,607	227,239
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from fixed maturities matured/called - available for sale, at market value	1,099,850	927,867	695,921
Proceeds from fixed maturities matured/called - available for sale, at fair value	7,213	1,300	12,775
Proceeds from fixed maturities sold - available for sale, at market value	598,342	476,491	1,209,150
Proceeds from fixed maturities sold - available for sale, at fair value	21,572	84,917	65,158
Proceeds from equity securities sold - available for sale, at market value			27,096
Proceeds from equity securities sold - available for sale, at fair value	612,516	546,463	237,849
Proceeds from sale of subsidiary to related party			61,005
Distributions from other invested assets	64,483	29,198	79,927
Cost of fixed maturities acquired - available for sale, at market value	(1,611,791)	(1,784,344)	(1,455,940)
Cost of fixed maturities acquired - available for sale, at fair value	(6,196)	(7,955)	(27,481)
Cost of equity securities acquired - available for sale, at market value			(27,059)
Cost of equity securities acquired - available for sale, at fair value	(439,115)	(404,051)	(746,604)
Cost of other invested assets acquired	(17,926)	(51,512)	(53,070)
Cost of other invested assets acquired, at fair value			(37,611)
Cost of businesses acquired			(63,100)
Net change in short-term investments	(292,751)	(42,027)	89,735
Net change in unsettled securities transactions	(3,057)	35,075	13,467
Net cash provided by (used in) investing activities	33,140	(188,578)	81,218
CASH FLOWS FROM FINANCING ACTIVITIES:
Tax benefit from share-based compensation	2,845	4	275
Revolving credit borrowings			(50,000)
Net cost of junior subordinated debt securities maturing	(329,897)
Net cash provided by (used in) financing activities	(327,052)	4	(49,725)
EFFECT OF EXCHANGE RATE CHANGES ON CASH	(17,966)	44,420	(28,557)
Net increase (decrease) in cash	(30,913)	(547)	230,175
Cash, beginning of period	347,720	348,267	118,092
Cash, end of period	316,807	347,720	348,267
SUPPLEMENTAL CASH FLOW INFORMATION:
Income taxes paid (recovered)	51,045	38,548	(62,137)
Interest paid	37,725	50,072	50,091
Non-cash transaction:
Net assets acquired and liabilities assumed from business acquisitions			$ 19,130