INVESTMENTS (DETAILS 2) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Schedule Of Contractual Maturities [Line Items]
Due in one year or less (amortized cost)	$ 646,351	$ 543,100
Due after one year through five years (amortized cost)	4,777,747	4,694,832
Due after five years through ten years (amortized cost)	1,611,931	1,779,811
Due after ten years (amortized cost)	96,779	119,926
Total fixed maturities with single maturity date (amortized cost)	7,132,808	7,137,669
Total (amortized cost)	11,280,366	10,821,338
Due in one year or less (fair value)	647,923	539,009
Due after one year through five years (fair value)	4,828,090	4,685,866
Due after five years through ten years (fair value)	1,695,911	1,845,054
Due after ten years (fair value)	101,769	123,091
Total fixed maturities with a single maturity date (fair value)	7,273,693	7,193,020
Fair Value (fixed maturities)	11,504,448	10,940,100
Due in one year or less (% of total fair value)	5.60%	4.90%
Due after one year through five years (% of total fair value)	42.00%	42.80%
Due after five years through ten years (% of total fair value)	14.70%	16.90%
Due after ten years (% of total fair value)	0.90%	1.10%
Fixed maturities with single maturity date (% of total fair value)	63.20%	65.70%
Total	100.00%	100.00%
Agency RMBS [Member]
Schedule Of Contractual Maturities [Line Items]
Fixed maturities without a single maturity date (amortized cost)	2,713,950	2,568,053
Total (amortized cost)	2,713,950	2,568,053
Fixed maturities without a single maturity date (fair value)	2,790,157	2,636,634
Fair Value (fixed maturities)	2,790,157	2,636,634
Fixed maturities without a single maturity date (% of total fair value)	24.30%	24.10%
CMBS [Member]
Schedule Of Contractual Maturities [Line Items]
Fixed maturities without a single maturity date (amortized cost)	606,935	298,138
Total (amortized cost)	606,935	298,138
Fixed maturities without a single maturity date (fair value)	623,396	312,691
Fair Value (fixed maturities)	623,396	312,691
Fixed maturities without a single maturity date (% of total fair value)	5.40%	2.90%
Non-Agency RMBS [Member]
Schedule Of Contractual Maturities [Line Items]
Fixed maturities without a single maturity date (amortized cost)	151,906	177,529
Total (amortized cost)	151,906	177,529
Fixed maturities without a single maturity date (fair value)	147,595	165,713
Fair Value (fixed maturities)	147,595	165,713
Fixed maturities without a single maturity date (% of total fair value)	1.30%	1.50%
ABS [Member]
Schedule Of Contractual Maturities [Line Items]
Fixed maturities without a single maturity date (amortized cost)	674,767	639,949
Total (amortized cost)	674,767	639,949
Fixed maturities without a single maturity date (fair value)	669,607	632,042
Fair Value (fixed maturities)	$ 669,607	$ 632,042
Fixed maturities without a single maturity date (% of total fair value)	5.80%	5.80%