Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	$ 450,549	$ 791,817
Adjustments to reconcile net income to net cash provided by operating activities:
Decrease (increase) in premiums receivable	(357,162)	(219,637)
Decrease (increase) in funds held by reinsureds, net	(53,878)	(17,961)
Decrease (increase) in reinsurance receivables	(172,454)	(42,891)
Decrease (increase) in income taxes	184,311	168,360
Decrease (increase) in prepaid reinsurance premiums	(7,963)	(145,846)
Increase (decrease) in reserve for losses and loss adjustment expenses	1,665,982	553,668
Increase (decrease) in future policy benefit reserve	(2,218)	(2,502)
Increase (decrease) in unearned premiums	392,904	388,597
Increase (decrease) in other net payable to reinsurers	68,784	160,306
Increase (decrease) in losses in course of payment	132,208	(6,438)
Change in equity adjustments in limited partnerships	(12,475)	(104,987)
Distribution of limited partnership income	55,576	62,359
Change in other assets and liabilities, net	(131,224)	(37,449)
Non-cash compensation expense	29,337	25,386
Amortization of bond premium (accrual of bond discount)	32,594	23,642
Net realized capital (gains) losses	(84,263)	(109,561)
Net cash provided by (used in) operating activities	2,190,608	1,486,863
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from fixed maturities matured/called - available for sale, at market value	1,781,821	1,631,298
Proceeds from fixed maturities sold - available for sale, at market value	1,390,747	2,589,232
Proceeds from fixed maturities sold - available for sale, at fair value	2,054	2,706
Proceeds from equity securities sold, at fair value	329,750	185,157
Distributions from other invested assets	210,527	215,800
Cost of fixed maturities acquired - available for sale, at market value	(3,874,890)	(5,039,728)
Cost of equity securities acquired, at fair value	(460,953)	(269,969)
Cost of other invested assets acquired	(392,650)	(299,480)
Net change in short-term investments	(804,744)	(213,048)
Net change in unsettled securities transactions	89,064	(13,770)
Net cash provided by (used in) investing activities	(1,729,274)	(1,211,802)
CASH FLOWS FROM FINANCING ACTIVITIES:
Common shares issued during the period for share-based compensation, net of expense	(13,617)	(7,836)
Purchase of treasury shares	(200,020)	(24,604)
Dividends paid to shareholders	(187,110)	(171,131)
Cost of debt repurchase	(10,647)
FHLB advances (repayments)	90,000
Cost of shares withheld on settlements of share-based compensation awards	(15,298)	(12,473)
Net cash provided by (used in) financing activities	(336,691)	(216,044)
EFFECT OF EXCHANGE RATE CHANGES ON CASH	6,203	2,060
Net increase (decrease) in cash	130,845	61,077
Cash, beginning of period	808,036	656,095
Cash, end of period	938,881	717,172
SUPPLEMENTAL CASH FLOW INFORMATION:
Income taxes paid (recovered)	(169,149)	(80,544)
Interest paid	$ 16,731	$ 19,078