INVESTMENTS (Details 3) $ in Thousands	Jun. 30, 2017 USD ($) security	Dec. 31, 2016 USD ($) security
Fixed Maturities [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value - 12 months or greater	$ 516,233	$ 971,489
Unrealized Losses - 12 months or greater	(38,330)	(77,645)
Fair Value - Less than 12 months	5,109,359	5,833,715
Unrealized Losses - Less than 12 months	(56,424)	(119,550)
Total Fair Value of Securities in Unrealized Loss Position	5,625,592	6,805,204
Total Unrealized Losses	$ (94,754)	$ (197,195)
Number of Available For Sale Securities In Unrealized Loss Positions | security	1,690	1,881
Number of Available For Sale Securities in Unrealized Loss Positions for 12 Months or Greater | security	216	330
Fixed Maturities [Member] | Below Investment Grade or Not Rated [Member]
Schedule Of Available For Sale Securities [Line Items]
Total Unrealized Losses	$ (7,000)	$ (15,000)
US Government and Agency [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value - 12 months or greater	65,015	54,051
Unrealized Losses - 12 months or greater	(2,795)	(2,729)
Fair Value - Less than 12 months	1,303,677	1,340,719
Unrealized Losses - Less than 12 months	(12,712)	(24,275)
Total Fair Value of Securities in Unrealized Loss Position	1,368,692	1,394,770
Total Unrealized Losses	(15,507)	(27,004)
Non-US Government [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value - 12 months or greater	103,740	149,360
Unrealized Losses - 12 months or greater	(16,923)	(38,683)
Fair Value - Less than 12 months	180,768	283,796
Unrealized Losses - Less than 12 months	(1,356)	(10,971)
Total Fair Value of Securities in Unrealized Loss Position	284,508	433,156
Total Unrealized Losses	(18,279)	(49,654)
Corporate Debt [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value - 12 months or greater	163,247	230,218
Unrealized Losses - 12 months or greater	(14,667)	(30,652)
Fair Value - Less than 12 months	1,532,619	1,948,976
Unrealized Losses - Less than 12 months	(17,543)	(44,488)
Total Fair Value of Securities in Unrealized Loss Position	1,695,866	2,179,194
Total Unrealized Losses	(32,210)	(75,140)
Agency RMBS [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value - 12 months or greater	93,978	76,694
Unrealized Losses - 12 months or greater	(1,760)	(1,101)
Fair Value - Less than 12 months	1,539,025	1,724,170
Unrealized Losses - Less than 12 months	(22,223)	(34,876)
Total Fair Value of Securities in Unrealized Loss Position	1,633,003	1,800,864
Total Unrealized Losses	(23,983)	(35,977)
CMBS [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value - 12 months or greater	22,821	84,640
Unrealized Losses - 12 months or greater	(502)	(749)
Fair Value - Less than 12 months	190,379	193,499
Unrealized Losses - Less than 12 months	(1,648)	(2,815)
Total Fair Value of Securities in Unrealized Loss Position	213,200	278,139
Total Unrealized Losses	(2,150)	(3,564)
Non-Agency RMBS [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value - 12 months or greater	8,563	13,642
Unrealized Losses - 12 months or greater	(1,070)	(1,752)
Fair Value - Less than 12 months	61	7,194
Unrealized Losses - Less than 12 months	(1)	(271)
Total Fair Value of Securities in Unrealized Loss Position	8,624	20,836
Total Unrealized Losses	(1,071)	(2,023)
ABS [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value - 12 months or greater	58,106	362,110
Unrealized Losses - 12 months or greater	(576)	(1,950)
Fair Value - Less than 12 months	318,030	266,763
Unrealized Losses - Less than 12 months	(424)	(893)
Total Fair Value of Securities in Unrealized Loss Position	376,136	628,873
Total Unrealized Losses	(1,000)	(2,843)
Municipals [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value - 12 months or greater	763	774
Unrealized Losses - 12 months or greater	(37)	(29)
Fair Value - Less than 12 months	44,800	68,598
Unrealized Losses - Less than 12 months	(517)	(961)
Total Fair Value of Securities in Unrealized Loss Position	45,563	69,372
Total Unrealized Losses	(554)	(990)
Equity Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value - 12 months or greater	40	4,959
Unrealized Losses - 12 months or greater	(128)	(461)
Fair Value - Less than 12 months	28,156	211,751
Unrealized Losses - Less than 12 months	(1,615)	(11,607)
Total Fair Value of Securities in Unrealized Loss Position	28,196	216,710
Total Unrealized Losses	$ (1,743)	$ (12,068)
Number of Available For Sale Securities In Unrealized Loss Positions | security	45	23
Number of Available For Sale Securities in Unrealized Loss Positions for 12 Months or Greater | security	2	3
Common Stock [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value - 12 months or greater	$ 40	$ 0
Unrealized Losses - 12 months or greater	(128)	0
Fair Value - Less than 12 months	4,438	37
Unrealized Losses - Less than 12 months	(437)	(342)
Total Fair Value of Securities in Unrealized Loss Position	4,478	37
Total Unrealized Losses	(565)	(342)
Exchange-Traded Funds [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value - 12 months or greater	0	4,959
Unrealized Losses - 12 months or greater	0	(461)
Fair Value - Less than 12 months	0	87,760
Unrealized Losses - Less than 12 months	0	(2,173)
Total Fair Value of Securities in Unrealized Loss Position	0	92,719
Total Unrealized Losses	0	(2,634)
Bond Mutual Funds [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value - 12 months or greater	0	0
Unrealized Losses - 12 months or greater	0	0
Fair Value - Less than 12 months	23,718	123,954
Unrealized Losses - Less than 12 months	(1,178)	(9,092)
Total Fair Value of Securities in Unrealized Loss Position	23,718	123,954
Total Unrealized Losses	$ (1,178)	$ (9,092)