Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
CASH FROM OPERATING ACTIVITIES:
Net income to common stockholders	$ 681,944	$ 640,749	$ 549,094
Adjustments to reconcile net income to net cash from operating activities:
Net realized and unrealized gains on investments	(120,703)	(154,488)	(335,858)
Depreciation and amortization	113,387	131,108	112,956
Noncontrolling interests	2,041	8,317	4,243
Investment funds	(69,194)	(109,349)	(69,333)
Stock incentive plans	49,274	36,591	40,490
Change in:
Arbitrage trading account	(26,553)	(19,093)	(4,896)
Premiums and fees receivable	(189,151)	(43,813)	(67,752)
Reinsurance accounts	(165,898)	(165,287)	(66,542)
Deferred policy acquisition costs	(20,057)	7,788	30,343
Current income taxes	(12,530)	(11,950)	25,859
Deferred income taxes	7,130	(74,761)	(16,893)
Reserves for losses and loss expenses	612,254	339,015	438,530
Unearned premiums	301,355	84,142	4,160
Other	(19,506)	(48,770)	66,482
Net cash from operating activities	1,143,793	620,199	710,883
CASH FLOWS USED IN INVESTING ACTIVITIES:
Proceeds from sale of fixed maturity securities	2,093,271	3,525,149	4,035,162
Proceeds from sale of equity securities	79,963	497,989	195,270
Distributions (contributions) from investment funds	194,663	(79,635)	247,404
Proceeds from maturities and prepayments of fixed maturity securities	2,933,980	2,676,455	3,556,744
Purchase of fixed maturity securities	(5,352,886)	(6,677,753)	(7,940,957)
Purchase of equity securities	(172,978)	(85,610)	(27,522)
Real estate purchased	(146,752)	(514,064)	(236,039)
Change in loans receivable	3,481	(13,204)	27,135
Net additions to property, furniture and equipment	(60,457)	(49,860)	(115,719)
Change in balances due from security brokers	2,844	4,262	(4,372)
Cash received in connection with business disposition	0	8,664	0
Payment for business purchased, net of cash acquired	0	(6,637)	(70,570)
Net cash used in investing activities	(424,871)	(714,244)	(333,464)
CASH FLOWS USED IN FINANCING ACTIVITIES:
Net proceeds from issuance of debt	290,974	294,562	6,983
Repayment of senior notes and other debt	(456,360)	(4,524)	(20)
Cash dividends to common stockholders	(308,191)	(254,951)	(188,199)
Purchase of common treasury shares	(18,225)	(24,750)	(47,807)
Other, net	(21,391)	(17,740)	(6,043)
Net cash used in financing activities	(513,193)	(7,403)	(235,086)
Net impact on cash due to change in foreign exchange rates	379	(31,421)	12,853
Net increase (decrease) in cash and cash equivalents	206,108	(132,869)	155,186
Cash and cash equivalents at beginning of year	817,602	950,471	795,285
Cash and cash equivalents at end of year	$ 1,023,710	$ 817,602	$ 950,471