RESERVE FOR LOSSES AND LOSS EXPENSES (DETAILS) (USD $) In Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Reconciliation of Beginning and Ending Gross Unpaid Losses and Loss Expenses
Gross reserve for losses and loss expenses, beginning of period			$ 7,032,375	$ 6,564,133
Less reinsurance recoverable on unpaid losses, beginning of period			(1,540,633)	(1,381,058)
Net reserve for losses and loss expenses, beginning of period			5,491,742	5,183,075
Net incurred losses related to:
Current year			2,271,284	1,525,564
Prior years	(78,431)	(71,707)	(179,686)	(231,777)
Net incurred losses			2,091,598	1,293,787
Net paid losses related to:
Current year			(285,137)	(207,922)
Prior years			(700,522)	(835,972)
Net paid losses			(985,659)	(1,043,894)
Foreign exchange and other			(3,949)	(23,208)
Net reserve for losses and loss expenses, end of period	6,593,732	5,409,760	6,593,732	5,409,760
Reinsurance recoverable on unpaid losses, end of period	1,741,109	1,524,768	1,741,109	1,524,768
Gross reserve for losses and loss expenses, end of period	$ 8,334,841	$ 6,934,528	$ 8,334,841	$ 6,934,528