Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
CASH FROM OPERATING ACTIVITIES:
Net income to common stockholders	$ 499,925	$ 510,592	$ 391,211
Adjustments to reconcile net income to net cash from operating activities:
Net investment gains	(121,544)	(210,465)	(125,481)
Depreciation and amortization	103,090	103,419	88,012
Noncontrolling interests	5,376	51	(70)
Investment funds	(67,712)	(77,015)	1,751
Stock incentive plans	23,784	26,763	27,175
Change in:
Arbitrage trading account	(10,324)	(1,424)	(8,106)
Premiums and fees receivable	(138,027)	(228,756)	(122,468)
Reinsurance accounts	(171,263)	(216,968)	(161,070)
Deferred policy acquisition costs	(52,124)	(38,656)	(38,541)
Deferred income taxes	56,281	13,240	43,340
Reserves for losses and loss expenses	372,002	406,763	325,758
Unearned premiums	323,160	279,986	238,499
Other	(2,826)	107,928	10,269
Net cash from operating activities	819,798	675,458	670,279
CASH FLOWS FROM (USED IN) INVESTING ACTIVITIES:
Proceeds from sale of fixed maturity securities	1,344,707	838,576	1,293,876
Proceeds from sale of equity securities	267,554	409,610	159,827
Distributions from (contributions to) investment funds	(236,580)	77,930	(113,913)
Proceeds from maturities and prepayments of fixed maturity securities	2,718,156	2,291,105	1,697,144
Purchase of fixed maturity securities	(4,198,135)	(3,617,002)	(2,815,340)
Purchase of equity securities	(156,557)	(284,991)	(97,986)
Real estate purchased	(107,352)	(256,386)	(96,552)
Change in loans receivable	(30,974)	(124,776)	92,176
Net additions to property, furniture and equipment	(63,150)	(40,556)	(45,320)
Change in balances due from security brokers	(26,155)	(25,799)	(16,194)
Payment for business purchased, net of cash acquired	(56,878)	(42,779)	(261,992)
Net cash used investing activities	(545,364)	(775,068)	(204,274)
CASH FLOWS FROM (USED IN) FINANCING ACTIVITIES:
Net proceeds from issuance of debt	346,822	369,291	0
Net proceeds from stock options exercised	53	7,660	21,963
Repayment of senior notes and other debt	(465,389)	0	(1,310)
Cash dividends to common stockholders	(52,717)	(183,947)	(43,253)
Purchase of common treasury shares	(166,473)	(127,663)	(187,163)
Other	7,442	31,851	14,550
Net cash from (used in) financing activities	(330,262)	97,192	(195,213)
Net impact on cash due to change in foreign exchange rates	(10,104)	(3,654)	(2,002)
Net increase (decrease) in cash and cash equivalents	(65,932)	(6,072)	268,790
Cash and cash equivalents at beginning of year	905,670	911,742	642,952
Cash and cash equivalents at end of year	$ 839,738	$ 905,670	$ 911,742