INVESTMENTS (DETAILS) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 11,280,366	$ 10,821,338
Cost	609,718	699,566
Fair Value (fixed maturities)	11,504,448	10,940,100
Fair Value (equities)	631,731	677,560
Fixed Maturities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	11,280,366	10,821,338
Gross Unrealized Gains	280,165	243,646
Gross Unrealized Losses	(56,083)	(124,884)
Fair Value (fixed maturities)	11,504,448	10,940,100
Non-credit OTTI in AOCI	(949)	(1,120)
US Government and Agency [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	1,129,843	1,142,732
Gross Unrealized Gains	7,117	5,669
Gross Unrealized Losses	(806)	(134)
Fair Value (fixed maturities)	1,136,154	1,148,267
Non-credit OTTI in AOCI	0	0
Non-US Government [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	1,251,832	1,241,664
Gross Unrealized Gains	23,132	7,359
Gross Unrealized Losses	(12,421)	(36,572)
Fair Value (fixed maturities)	1,262,543	1,212,451
Non-credit OTTI in AOCI	0	0
Corporate Debt [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	3,572,982	3,581,320
Gross Unrealized Gains	93,932	85,766
Gross Unrealized Losses	(23,542)	(57,495)
Fair Value (fixed maturities)	3,643,372	3,609,591
Non-credit OTTI in AOCI	0	0
Agency RMBS [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	2,713,950	2,568,053
Gross Unrealized Gains	77,118	69,073
Gross Unrealized Losses	(911)	(492)
Fair Value (fixed maturities)	2,790,157	2,636,634
Non-credit OTTI in AOCI	0	0
CMBS [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	606,935	298,138
Gross Unrealized Gains	16,703	14,816
Gross Unrealized Losses	(242)	(263)
Fair Value (fixed maturities)	623,396	312,691
Non-credit OTTI in AOCI	0	0
Non-Agency RMBS [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	151,906	177,529
Gross Unrealized Gains	2,116	1,431
Gross Unrealized Losses	(6,427)	(13,247)
Fair Value (fixed maturities)	147,595	165,713
Non-credit OTTI in AOCI	(949)	(1,120)
ABS [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	674,767	639,949
Gross Unrealized Gains	6,260	7,094
Gross Unrealized Losses	(11,420)	(15,001)
Fair Value (fixed maturities)	669,607	632,042
Non-credit OTTI in AOCI	0	0
Municipals [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	1,178,151	1,171,953
Gross Unrealized Gains	53,787	52,438
Gross Unrealized Losses	(314)	(1,680)
Fair Value (fixed maturities)	1,231,624	1,222,711
Non-credit OTTI in AOCI	0	0
Equity Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost	609,718	699,566
Gross Unrealized Gains	41,602	25,220
Gross Unrealized Losses	(19,589)	(47,226)
Fair Value (equities)	631,731	677,560
Common Stock [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost	385,871	341,603
Gross Unrealized Gains	40,240	25,143
Gross Unrealized Losses	(17,073)	(19,291)
Fair Value (equities)	409,038	347,455
Exchange Traded Funds [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost	128,622	239,411
Gross Unrealized Gains	1,362	77
Gross Unrealized Losses	0	(25,507)
Fair Value (equities)	129,984	213,981
Non-U.S. Bond Mutual Funds [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost	95,225	118,552
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(2,516)	(2,428)
Fair Value (equities)	$ 92,709	$ 116,124

Total of accumulated other comprehensive loss related to that portion of other than temporary impairment (OTTI) due to factors other than credit losses on debt securities categorized either as available-for-sale or held-to-maturity that an entity does not intend to sell and which it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis of the debt security. The amount represented by this item is net of tax, as applicable.

+ References+ Details

This item represents the total of all debt securities grouped by maturity dates, at cost, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments, as defined), and fair value hedge accounting adjustments, if any, which are classified neither as held-to-maturity nor trading securities.

+ References+ Details

- Definition

For an unclassified balance sheet, total of debt securities categorized neither as held-to-maturity nor trading.

+ References

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+ Details

- Definition

For an unclassified balance sheet, this item represents equity securities categorized neither as held-to-maturity nor trading.

+ References

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+ Details

- Definition

This item represents the gross unrealized gains for securities, at a point in time, which are categorized neither as held-to-maturity nor trading securities.

+ References+ Details