Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	$ 295,750	$ 412,653	$ 454,126
Adjustments to reconcile net income to net cash provided by operating activities:
Decrease (increase) in premiums receivable	1,140	(49,602)	83,362
Decrease (increase) in funds held by reinsureds, net	(4,445)	4,737	2,236
Decrease (increase) in reinsurance receivables	(112,797)	(465,761)	(460,635)
Decrease (increase) in income taxes	60,325	57,487	68,206
Decrease (increase) in prepaid reinsurance premiums	(8,083)	30,985	(138,010)
Increase (decrease) in reserve for losses and loss adjustment expenses	384,628	184,845	248,053
Increase (decrease) in unearned premiums	(38,271)	(82,494)	130,519
Increase (decrease) in other net payable to reinsurers	(364,242)	204,526	5,130
Increase (decrease) in losses in course of payment	(42,643)	(51,416)	(171,071)
Change in equity adjustments in limited partnerships	(24,486)	(18,144)	(28,249)
Distribution of limited partnership income	32,613	45,235	41,064
Change in other assets and liabilities, net	16,090	7,499	81,388
Non-cash compensation expense	9,481	8,025	7,911
Amortization of bond premium (accrual of bond discount)	18,051	18,160	19,086
Amortization of underwriting discount on senior notes	4	4	46
Net realized capital (gains) losses	28,941	(50,335)	(206,679)
Net cash provided by (used in) operating activities	252,056	256,404	136,483
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from fixed maturities matured/called - available for sale, at market value	781,744	902,932	1,071,296
Proceeds from fixed maturities matured/called - available for sale, at fair value			875
Proceeds from fixed maturities sold - available for sale, at market value	704,191	544,955	1,080,276
Proceeds from fixed maturities sold - available for sale, at fair value	5,837	1,824	36,467
Proceeds from equity securities sold - available for sale, at market value		16
Proceeds from equity securities sold - available for sale, at fair value	695,039	567,069	528,958
Proceeds from sale of subsidiary (net of cash disposed)	47,721	3,934
Distributions from other invested assets	1,756,484	51,494	72,323
Cost of fixed maturities acquired - available for sale, at market value	(2,110,113)	(1,811,463)	(2,406,162)
Cost of fixed maturities acquired - available for sale, at fair value	(3,940)	(2,436)	(24,097)
Cost of equity securities acquired - available for sale, at fair value	(324,407)	(530,538)	(416,375)
Cost of other invested assets acquired	(1,928,119)	(93,728)	(134,373)
Net change in short-term investments	257,792	(6,145)	189,139
Net cost of lending for long term note - affiliated			(250,000)
Net change in unsettled securities transactions	10,474	(23,447)	(4,157)
Net cash provided by (used in) investing activities	(107,297)	(395,533)	(255,830)
CASH FLOWS FROM FINANCING ACTIVITIES:
Tax benefit from share-based compensation	3,298	4,472	3,331
Net proceeds from issuance of senior notes			400,000
Net cost of senior notes maturing			(250,000)
Net cash provided by (used in) financing activities	3,298	4,472	153,331
EFFECT OF EXCHANGE RATE CHANGES ON CASH	(5,692)	(33,889)	(26,816)
Net increase (decrease) in cash	142,365	(168,546)	7,168
Cash, beginning of period	155,429	323,975	316,807
Cash, end of period	297,794	155,429	323,975
SUPPLEMENTAL CASH FLOW INFORMATION:
Income taxes paid (recovered)	31,018	131,632	133,057
Interest paid	$ 35,217	35,217	$ 38,861
NON-CASH TRANSACTION:
Exchange of common shares of parent company, held as other invested assets at fair value, for preferred shares of an affiliated company, held as other invested assets at fair value		$ 1,773,214