Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	$ 316,645	$ 251,608
Adjustments to reconcile net income to net cash provided by operating activities:
Decrease (increase) in premiums receivable	(88,422)	(104,944)
Decrease (increase) in funds held by reinsureds, net	(20,983)	(14,361)
Decrease (increase) in reinsurance receivables	97,388	(63,291)
Decrease (increase) in income taxes	35,413	94,733
Decrease (increase) in prepaid reinsurance premiums	30,259	(2,163)
Increase (decrease) in reserve for losses and loss adjustment expenses	106,144	(3,035)
Increase (decrease) in unearned premiums	112,401	123,901
Increase (decrease) in other net payable to reinsurers	84,561	(61,808)
Increase (decrease) in losses in course of payment	976	(78,061)
Change in equity adjustments in limited partnerships	6,063	(7,836)
Distribution of limited partnership income	9,486	7,162
Change in other assets and liabilities, net	(76,651)	44,139
Non-cash compensation expense	7,528	7,551
Amortization of bond premium (accrual of bond discount)	1,385	(366)
Net realized capital (gains) losses	(256,867)	(135,056)
Net cash provided by (used in) operating activities	365,327	58,173
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from fixed maturities matured/called - available for sale, at market value	257,000	184,894
Proceeds from fixed maturities sold - available for sale, at market value	164,244	1,603,889
Proceeds from equity securities sold - at fair value	204,161	69,238
Distributions from other invested assets	76,391	43,469
Cost of fixed maturities acquired - available for sale, at market value	(713,474)	(1,522,903)
Cost of equity securities acquired- at fair value	(167,914)	(146,335)
Cost of other invested assets acquired	(101,663)	(89,216)
Net change in short-term investments	(45,503)	(283,094)
Net change in unsettled securities transactions	(34,793)	19,330
Net cash provided by (used in) investing activities	(361,551)	(120,728)
CASH FLOWS FROM FINANCING ACTIVITIES:
Tax benefit from share-based compensation, net of expense	(7,425)	(7,464)
Cost of debt repurchase	(1,198)
Net cash provided by (used in) financing activities	(8,623)	(7,464)
EFFECT OF EXCHANGE RATE CHANGES ON CASH	(20,301)	2,722
Net increase (decrease) in cash	(25,148)	(67,297)
Cash, beginning of period	411,122	404,522
Cash, end of period	385,974	337,225
SUPPLEMENTAL CASH FLOW INFORMATION:
Income taxes paid (recovered)	3,558	(90,148)
Interest paid	$ 2,712	$ 3,049