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)	$ 302,022	$ 384,343
Adjustments to reconcile net income to net cash provided by operating activities:
Decrease (increase) in premiums receivable	25,533	(53,067)
Decrease (increase) in funds held by reinsureds, net	3,399	4,584
Decrease (increase) in reinsurance receivables	(114,898)	(92,736)
Decrease (increase) in income taxes	34,417	64,227
Decrease (increase) in prepaid reinsurance premiums	2,359	3,446
Increase (decrease) in reserve for losses and loss adjustment expenses	(56,348)	(127,942)
Increase (decrease) in future policy benefit reserve	(1,423)	(796)
Increase (decrease) in unearned premiums	80,016	54,323
Increase (decrease) in other net payables to reinsurers	1,176	4,188
Increase (decrease) in losses in course of payment	107,003	148,773
Change in equity adjustments in limited partnerships	2,313	(17,356)
Distribution of limited partnership income	8,600	33,686
Change in other assets and liabilities, net	(23,959)	(43,814)
Non-cash compensation expense	4,427	5,614
Amortization of bond premium (accrual of bond discount)	13,572	18,607
Amortization of underwriting discount on senior notes	14	13
Net realized capital (gains) losses	(21,126)	(126,735)
Net cash provided by (used in) operating activities	367,097	259,358
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from fixed maturities matured/called - available for sale, at market value	490,745	612,044
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	328,709	254,496
Proceeds from fixed maturities sold - available for sale, at fair value	20,763	3,664
Proceeds from equity securities sold - available for sale, at market value	534	1,229
Proceeds from equity securities sold - available for sale, at fair value	178,598	106,175
Distributions from other invested assets	17,077	50,016
Cost of fixed maturities acquired - available for sale, at market value	(1,163,440)	(1,016,289)
Cost of fixed maturities acquired - available for sale, at fair value	(1,309)	(1,295)
Cost of equity securities acquired - available for sale, at market value	(8,546)	(1,566)
Cost of equity securities acquired - available for sale, at fair value	(92,329)	(122,617)
Cost of other invested assets acquired	(4,961)	(6,684)
Net change in short-term investments	(152,715)	78,507
Net change in unsettled securities transactions	1,564	(8,467)
Net cash provided by (used in) investing activities	(384,435)	(47,787)
CASH FLOWS FROM FINANCING ACTIVITIES:
Common shares issued during the period, net	2,121	26,918
Purchase of treasury shares	(249,983)	(238,632)
Third party investment in redeemable noncontrolling interest	70,700
Dividends paid to shareholders	(34,742)	(24,231)
Net cash provided by (used in) financing activities	(211,904)	(235,945)
EFFECT OF EXCHANGE RATE CHANGES ON CASH	3,264	11,460
Net increase (decrease) in cash	(225,978)	(12,914)
Cash, beginning of period	611,382	537,050
Cash, end of period	385,404	524,136
SUPPLEMENTAL CASH FLOW INFORMATION:
Income taxes paid (recovered)	16,260	19,188
Interest paid	$ 174	$ 6,001