Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	$ 1,074,488	$ 1,258,463	$ 1,265,260
Adjustments to reconcile net income to net cash provided by operating activities:
Decrease (increase) in premiums receivable	(93,837)	45,282	(217,678)
Decrease (increase) in funds held by reinsureds, net	31,225	(1,835)	162
Decrease (increase) in reinsurance receivables	(240,414)	(186,014)	118,963
Decrease (increase) in income taxes	(36,771)	31,340	213,848
Decrease (increase) in prepaid reinsurance premiums	(14,486)	(79,086)	(12,777)
Increase (decrease) in reserve for losses and loss adjustment expenses	394,167	195,524	(374,027)
Increase (decrease) in future policy benefit reserve	(910)	308	(6,595)
Increase (decrease) in unearned premiums	(96,950)	161,149	261,959
Increase (decrease) in other net payable to reinsurers	38,262	29,410	(45,043)
Increase (decrease) in losses in course of payment	(43,964)	(174,206)	142,192
Change in equity adjustments in limited partnerships	(12,965)	(39,464)	(45,905)
Distribution of limited partnership income	53,984	51,120	56,982
Change in other assets and liabilities, net	264	35,419	(57,212)
Non-cash compensation expense	21,237	21,197	31,844
Amortization of bond premium (accrual of bond discount)	50,901	49,214	66,461
Amortization of underwriting discount on senior notes	4	46	54
Net realized capital (gains) losses	184,147	(84,046)	(300,227)
Net cash provided by (used in) operating activities	1,308,382	1,313,821	1,098,261
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from fixed maturities matured/called - available for sale, at market value	2,144,930	2,142,693	2,415,730
Proceeds from fixed maturities matured/called - available for sale, at fair value		875	7,213
Proceeds from fixed maturities sold - available for sale, at market value	1,724,093	1,811,801	1,092,387
Proceeds from fixed maturities sold - available for sale, at fair value	1,824	36,467	21,573
Proceeds from equity securities sold - available for sale, at market value	28,936	16,901	46,142
Proceeds from equity securities sold - available for sale, at fair value	614,044	584,069	705,831
Distributions from other invested assets	57,201	115,482	100,081
Proceeds from sale of subsidiary (net of cash disposed)	3,934
Cost of fixed maturities acquired - available for sale, at market value	(4,718,303)	(4,672,633)	(3,543,776)
Cost of fixed maturities acquired - available for sale, at fair value	(2,436)	(24,098)	(6,196)
Cost of equity securities acquired - available for sale, at market value	(10,850)	(18,016)	(59,756)
Cost of equity securities acquired - available for sale, at fair value	(556,889)	(446,457)	(621,038)
Cost of other invested assets acquired	(286,599)	(224,740)	(21,935)
Net change in short-term investments	(98,903)	(497,983)	(357,451)
Net change in unsettled securities transactions	(22,719)	(4,433)	(2,808)
Net cash provided by (used in) investing activities	(1,121,737)	(1,180,072)	(224,003)
CASH FLOWS FROM FINANCING ACTIVITIES:
Common shares issued during the period, net	13,597	17,839	51,500
Purchase of treasury shares	(400,059)	(500,024)	(621,915)
Net cost of junior subordinated debt securities redemption			(329,897)
Net cost of senior notes maturing		(250,000)
Net proceeds from issuance of senior notes		400,000
Third party investment in redeemable noncontrolling interest	266,848	136,200	87,500
Subscription advances for third party redeemable noncontrolling interest	30,000	40,000	143,000
Dividends paid to shareholders	(175,107)	(145,913)	(106,681)
Dividends paid on third party investment in redeemable noncontrolling interest	(68,158)	(10,334)
Net cash provided by (used in) financing activities	(332,879)	(312,232)	(776,493)
EFFECT OF EXCHANGE RATE CHANGES ON CASH	(7,582)	4,575	(23,433)
Net increase (decrease) in cash	(153,816)	(173,908)	74,332
Cash, beginning of period	437,474	611,382	537,050
Cash, end of period	283,658	437,474	611,382
SUPPLEMENTAL CASH FLOW INFORMATION:
Income taxes paid (recovered)	164,856	153,455	69,302
Interest paid	$ 35,973	$ 39,424	$ 38,390