Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	$ 585,250	$ 46,052
Adjustments to reconcile net income to net cash provided by operating activities:
Decrease (increase) in premiums receivable	(233,770)	(147,210)
Decrease (increase) in funds held by reinsureds, net	(21,256)	(13,336)
Decrease (increase) in reinsurance recoverables	226,291	233,199
Decrease (increase) in income taxes	116,483	(41,843)
Decrease (increase) in prepaid reinsurance premiums	(40,542)	15,928
Increase (decrease) in reserve for losses and loss adjustment expenses	812,725	205,192
Increase (decrease) in unearned premiums	272,722	90,640
Increase (decrease) in other net payable to reinsurers	66,461	89,520
Increase (decrease) in losses in course of payment	39,117	118,964
Change in equity adjustments in limited partnerships	(201,379)	50,809
Distribution of limited partnership income	27,905	30,916
Change in other assets and liabilities, net	(93,690)	(75,931)
Non-cash compensation expense	18,406	15,462
Amortization of bond premium (accrual of bond discount)	15,535	4,436
Net realized capital (gains) losses	(318,774)	222,493
Net cash provided by (used in) operating activities	1,271,484	845,291
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from fixed maturities matured/called - available for sale, at market value	1,153,258	494,544
Proceeds from fixed maturities sold - available for sale, at market value	242,072	337,723
Proceeds from equity securities sold - at fair value	346,088	213,003
Distributions from other invested assets	70,811	119,727
Cost of fixed maturities acquired - available for sale, at market value	(2,401,534)	(1,226,251)
Cost of equity securities acquired- at fair value	(358,790)	(222,818)
Cost of other invested assets acquired	(210,373)	(215,569)
Net change in short-term investments	205,323	(308,979)
Net change in unsettled securities transactions	(129,026)	37,744
Net cash provided by (used in) investing activities	(1,082,171)	(770,876)
CASH FLOWS FROM FINANCING ACTIVITIES:
Tax benefit from share-based compensation, net of expense	(18,182)	(15,258)
Cost of debt repurchase		(10,648)
Net cash provided by (used in) financing activities	(18,182)	(25,906)
EFFECT OF EXCHANGE RATE CHANGES ON CASH	(3,903)	(14,015)
Net increase (decrease) in cash	167,228	34,495
Cash, beginning of period	378,518	411,122
Cash, end of period	545,746	445,617
SUPPLEMENTAL CASH FLOW INFORMATION:
Income taxes paid (recovered)	28,859	4,763
Interest paid	$ 31,520	$ 14,782