Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	$ 86,466	$ 285,651
Adjustments to reconcile net income to net cash provided by operating activities:
Decrease (increase) in premiums receivable	12,611	(51,555)
Decrease (increase) in funds held by reinsureds, net	2,877	(6,122)
Decrease (increase) in reinsurance receivables	(279,364)	(22,142)
Decrease (increase) in income taxes	24,447	132,099
Decrease (increase) in prepaid reinsurance premiums	(47,040)	(16,378)
Increase (decrease) in reserve for losses and loss adjustment expenses	(58,410)	(176,428)
Increase (decrease) in unearned premiums	76,126	43,947
Increase (decrease) in other net payable to reinsurers	130,527	(4,619)
Increase (decrease) in losses in course of payment	101,869	162,432
Change in equity adjustments in limited partnerships	3,143	(11,220)
Distribution of limited partnership income	5,824	10,252
Change in other assets and liabilities, net	(16,618)	12,988
Non-cash compensation expense	1,729	2,173
Amortization of bond premium (accrual of bond discount)	6,004	6,563
Amortization of underwriting discount on senior notes	14	13
Net realized capital (gains) losses	4,050	(309,806)
Net cash provided by (used in) operating activities	54,255	57,848
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from fixed maturities matured/called - available for sale, at market value	207,534	298,241
Proceeds from fixed maturities matured/called - available for sale, at fair value	875	3,000
Proceeds from fixed maturities sold - available for sale, at market value	149,578	166,934
Proceeds from fixed maturities sold - available for sale, at fair value	20,763	3,664
Proceeds from equity securities sold - available for sale, at fair value	176,116	103,828
Distributions from other invested assets	9,828	22,225
Cost of fixed maturities acquired - available for sale, at market value	(689,205)	(586,523)
Cost of fixed maturities acquired - available for sale, at fair value	(1,309)	(1,295)
Cost of equity securities acquired - available for sale, at fair value	(77,427)	(120,527)
Cost of other invested assets acquired	(4,961)	(4,661)
Net change in short-term investments	113,571	83,622
Net change in unsettled securities transactions	(8,812)	(17,558)
Net cash provided by (used in) investing activities	(103,449)	(49,050)
CASH FLOWS FROM FINANCING ACTIVITIES:
Tax benefit from share-based compensation	1,665	985
Net cash provided by (used in) financing activities	1,665	985
EFFECT OF EXCHANGE RATE CHANGES ON CASH	3,987	(13,548)
Net increase (decrease) in cash	(43,542)	(3,765)
Cash, beginning of period	316,807	347,720
Cash, end of period	273,265	343,955
SUPPLEMENTAL CASH FLOW INFORMATION:
Income taxes paid (recovered)	12,474	862
Interest paid	$ 42	$ 5,136