Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
CASH FROM OPERATING ACTIVITIES:
Net income to common stockholders	$ 530,670	$ 681,944	$ 640,749
Adjustments to reconcile net income to net cash from operating activities:
Net investment gains	(103,000)	(120,703)	(154,488)
Depreciation and amortization	135,065	113,387	131,108
Noncontrolling interests	2,315	2,041	8,317
Investment funds	(54,253)	(69,194)	(109,349)
Stock incentive plans	49,658	49,274	36,591
Change in:
Arbitrage trading account	(67,943)	(26,553)	(19,093)
Premiums and fees receivable	(173,618)	(189,151)	(43,813)
Reinsurance accounts	(313,525)	(165,898)	(165,287)
Deferred policy acquisition costs	(38,691)	(20,057)	7,788
Current income taxes	49,021	(12,530)	(11,950)
Deferred income taxes	(34,057)	7,130	(74,761)
Reserves for losses and loss expenses	1,176,049	612,254	339,015
Unearned premiums	415,956	301,355	84,142
Other	43,039	(19,506)	(48,770)
Net cash from operating activities	1,616,686	1,143,793	620,199
CASH FLOWS FROM (USED) IN INVESTING ACTIVITIES:
Proceeds from sale of fixed maturity securities	3,832,555	2,093,271	3,525,149
Proceeds from sale of equity securities	114,763	79,963	497,989
(Contributions) distributions from investment funds	3,042	(194,663)	79,635
Proceeds from maturities and prepayments of fixed maturity securities	3,864,327	2,933,980	2,676,455
Purchase of fixed maturity securities	(7,551,591)	(5,352,886)	(6,677,753)
Purchase of equity securities	(253,031)	(172,978)	(85,610)
Real estate sold (purchased)	178,934	(146,752)	(514,064)
Change in loans receivable	1,467	3,481	(13,204)
Net additions to property, furniture and equipment	(38,171)	(60,457)	(49,860)
Change in balances due from security brokers	(26,515)	2,844	4,262
Cash received in connection with business disposition	0	0	8,664
Payment for business purchased, net of cash acquired	0	0	(6,637)
Net cash from (used) in investing activities	119,696	(424,871)	(714,244)
CASH FLOWS USED IN FINANCING ACTIVITIES:
Net proceeds from issuance of debt	741,637	290,974	294,562
Repayment and redemption of debt	(652,751)	(456,360)	(4,524)
Cash dividends to common stockholders	(84,147)	(308,191)	(254,951)
Purchase of common treasury shares	(346,357)	(18,225)	(24,750)
Other, net	(56,225)	(21,391)	(17,740)
Net cash used in financing activities	(397,843)	(513,193)	(7,403)
Net impact on cash due to change in foreign exchange rates	10,117	379	(31,421)
Net increase (decrease) in cash and cash equivalents	1,348,656	206,108	(132,869)
Cash and cash equivalents at beginning of year	1,023,710	817,602	950,471
Cash and cash equivalents at end of year	$ 2,372,366	$ 1,023,710	$ 817,602