LOSSES AND LOSS EXPENSES (Detail) - Net losses and loss expenses incurred (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Loss and loss expenses payments	$ 4,911,737	$ 4,309,523	$ 5,138,951
Change in unpaid losses and loss expenses	260,631	(141,589)	(1,148,495)
Change in unpaid losses and loss expenses recoverable	(28,442)	(117,120)	441,397
Paid loss recoveries	(1,065,535)	(839,014)	(1,263,016)
Net losses and loss expenses incurred	$ 4,078,391	$ 3,211,800	$ 3,168,837