Unaudited Condensed Consolidated Statements of Cash Flows (USD $) In Thousands	9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010
Cash flows from operating activities
Net (loss) income	$ (502,648)	$ 795,518
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Amortization of net premium on investments	63,268	59,766
Amortization of intangible assets	27,512	22,639
Net realized and unrealized investment losses (gains)	7,860	(484,683)
Changes in:
Reinsurance balances, net	(228,133)	(165,012)
Reinsurance recoverable on paid and unpaid losses, net of ceded premiums payable	(1,923)	(2,061)
Funds held by reinsured companies and funds held - directly managed	573,220	225,757
Deferred acquisition costs	8,716	(31,300)
Net tax assets and liabilities	(2,893)	(50,269)
Unpaid losses and loss expenses including life policy benefits	500,038	172,974
Unearned premiums	140,091	312,687
Other net changes in operating assets and liabilities	(1,176)	56,269
Net cash provided by operating activities	583,932	912,285
Redemptions of fixed maturities	967,020	962,540
Sales and redemptions of short-term investments	242,234	175,733
Purchases of short-term investments	(292,833)	(86,252)
Other, net	(131,989)	(160,862)
Net cash (used in) provided by investing activities	(1,599,055)	326,499
Cash flows from financing activities
Cash dividends paid to shareholders	(150,006)	(142,972)
Net proceeds from issuance of preferred shares	361,722	0
Repurchase of common shares	(244,222)	(682,476)
Issuance of common shares	13,219	17,487
Proceeds from issuance of senior notes	0	500,000
Contract fees on forward sale agreement	0	(2,638)
Repayment of debt	0	(200,000)
Net cash used in financing activities	(19,287)	(510,599)
Effect of foreign exchange rate changes on cash	(3,242)	(28,772)
(Decrease) increase in cash and cash equivalents	(1,037,652)	699,413
Cash and cash equivalents - beginning of period	2,111,084	738,309
Cash and cash equivalents - end of period	1,073,432	1,437,722
Supplemental cash flow information:
Taxes paid	136,188	182,335
Interest paid	24,630	18,365
Fixed maturities [Member]
Changes in:
Sales	5,049,822	5,609,630
Purchases	7,412,275	5,957,460
Equity securities [Member]
Changes in:
Sales	492,491	268,625
Purchases	$ 513,525	$ 485,455