Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
CASH FROM (USED IN) OPERATING ACTIVITIES:
Net income to common stockholders	$ 232,572	$ 244,156
Adjustments to reconcile net income to net cash from operating activities:
Net investment gains	(53,027)	(71,777)
Depreciation and amortization	50,617	47,147
Noncontrolling interests	(847)	(20)
Investment funds	(33,057)	(63,243)
Stock incentive plans	12,395	15,827
Change in:
Arbitrage trading account	1,590	(1,535)
Premiums and fees receivable	(162,853)	(139,183)
Reinsurance accounts	(67,447)	(46,182)
Deferred policy acquisition costs	(34,039)	(21,637)
Income taxes	(46,642)	20,963
Reserves for losses and loss expenses	221,525	151,975
Unearned premiums	269,931	188,902
Other	(76,786)	(12,982)
Net cash from (used in) operating activities	313,932	312,411
CASH FROM (USED IN) INVESTING ACTIVITIES:
Proceeds from sale of fixed maturity securities	555,694	370,902
Proceeds from sale of equity securities	66,969	70,274
Distributions from (contributions to) investment funds	(60,000)	23,090
Proceeds from maturities and prepayments of fixed maturity securities	1,561,236	922,961
Purchase of fixed maturity securities	(2,214,201)	(1,658,418)
Purchase of equity securities	(111,540)	(184,751)
Real estate purchased	(13,390)	(15,475)
Change in loans receivable	(46,854)	(61,886)
Net additions to real estate, furniture and equipment	(43,446)	(20,376)
Change in balances due to security brokers	(6,167)	38,700
Cash distributed in connection with business disposition	(21,408)
Payment for business purchased, net of cash acquired	(38,556)	0
Net cash from (used in) investing activities	(371,663)	(514,979)
CASH FROM (USED IN) FINANCING ACTIVITIES:
Repayment of senior notes and other debt	(486,297)	0
Net proceeds from issuance of debt	371,923	364,044
Net proceeds from stock options exercised	51	4,776
Cash dividends to common stockholders	(12,243)	(11,042)
Purchase of common treasury shares	(31,362)	(48,346)
Other, net	7,273	19,500
Net cash from (used in) financing activities	(150,655)	328,932
Net impact on cash due to change in foreign exchange rates	(38,445)	(25,886)
Net change in cash and cash equivalents	(246,831)	100,478
Cash and cash equivalents at beginning of year	905,670	911,742
Cash and cash equivalents at end of period	$ 658,839	$ 1,012,220