Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
CASH FROM OPERATING ACTIVITIES:
Net income to common stockholders	$ 640,749	$ 549,094	$ 601,916
Adjustments to reconcile net income to net cash from operating activities:
Net realized and unrealized gains on investments	(154,488)	(335,858)	(267,005)
Depreciation and amortization	131,108	112,956	86,051
Noncontrolling interests	8,317	4,243	1,569
Investment funds	(109,349)	(69,333)	(99,301)
Stock incentive plans	36,591	40,490	37,174
Change in:
Arbitrage trading account	(19,093)	(4,896)	(10,633)
Premiums and fees receivable	(43,813)	(67,752)	(60,403)
Reinsurance accounts	(165,287)	(66,542)	(235,455)
Deferred policy acquisition costs	7,788	30,343	(25,912)
Current income taxes	(11,950)	25,859	42,632
Deferred income taxes	(74,761)	(16,893)	9,012
Reserves for losses and loss expenses	339,015	438,530	572,196
Unearned premiums	84,142	4,160	149,683
Other	(48,770)	66,482	46,852
Net cash from operating activities	620,199	710,883	848,376
CASH FLOWS USED IN INVESTING ACTIVITIES:
Proceeds from sale of fixed maturity securities	3,525,149	4,035,162	2,440,310
Proceeds from sale of equity securities	497,989	195,270	143,042
(Contributions) distributions from investment funds	(79,635)	247,404	142,601
Proceeds from maturities and prepayments of fixed maturity securities	2,676,455	3,556,744	2,189,365
Purchase of fixed maturity securities	(6,677,753)	(7,940,957)	(5,541,202)
Purchase of equity securities	(85,610)	(27,522)	(202,736)
Real estate purchased	(514,064)	(236,039)	(299,123)
Change in loans receivable	(13,204)	27,135	166,327
Net additions to property, furniture and equipment	(49,860)	(115,719)	(50,829)
Change in balances due from security brokers	4,262	(4,372)	20,992
Cash received in connection with business disposition	8,664	0	250,216
Payment for business purchased, net of cash acquired	(6,637)	(70,570)	(53,451)
Net cash used in investing activities	(714,244)	(333,464)	(794,488)
CASH FLOWS USED IN FINANCING ACTIVITIES:
Net proceeds from issuance of debt	294,562	6,983	388,769
Repayment of senior notes and other debt	(4,524)	(20)	(75,487)
Cash dividends to common stockholders	(254,951)	(188,199)	(183,999)
Purchase of common treasury shares	(24,750)	(47,807)	(132,392)
Other, net	(17,740)	(6,043)	(3,823)
Net cash used in financing activities	(7,403)	(235,086)	(6,932)
Net impact on cash due to change in foreign exchange rates	(31,421)	12,853	(15,302)
Net (decrease) increase in cash and cash equivalents	(132,869)	155,186	31,654
Cash and cash equivalents at beginning of year	950,471	795,285	763,631
Cash and cash equivalents at end of year	$ 817,602	$ 950,471	$ 795,285