INVESTMENTS (Details 3) $ in Thousands	Mar. 31, 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	$ 590,420	$ 971,489
Unrealized Losses - 12 months or greater	(48,386)	(77,645)
Fair Value - Less than 12 months	5,029,407	5,833,715
Unrealized Losses - Less than 12 months	(81,508)	(119,550)
Total Fair Value of Securities in Unrealized Loss Position	5,619,827	6,805,204
Total Unrealized Losses	$ (129,894)	$ (197,195)
Number of Available For Sale Securities In Unrealized Loss Positions | security	1,674	1,881
Number of Available For Sale Securities in Unrealized Loss Positions for 12 Months or Greater | security	238	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	54,215	54,051
Unrealized Losses - 12 months or greater	(2,278)	(2,729)
Fair Value - Less than 12 months	1,097,124	1,340,719
Unrealized Losses - Less than 12 months	(15,738)	(24,275)
Total Fair Value of Securities in Unrealized Loss Position	1,151,339	1,394,770
Total Unrealized Losses	(18,016)	(27,004)
Non-US Government [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value - 12 months or greater	84,895	149,360
Unrealized Losses - 12 months or greater	(21,569)	(38,683)
Fair Value - Less than 12 months	191,561	283,796
Unrealized Losses - Less than 12 months	(2,641)	(10,971)
Total Fair Value of Securities in Unrealized Loss Position	276,456	433,156
Total Unrealized Losses	(24,210)	(49,654)
Corporate Debt [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value - 12 months or greater	137,955	230,218
Unrealized Losses - 12 months or greater	(19,905)	(30,652)
Fair Value - Less than 12 months	1,588,217	1,948,976
Unrealized Losses - Less than 12 months	(29,521)	(44,488)
Total Fair Value of Securities in Unrealized Loss Position	1,726,172	2,179,194
Total Unrealized Losses	(49,426)	(75,140)
Agency RMBS [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value - 12 months or greater	73,078	76,694
Unrealized Losses - 12 months or greater	(1,022)	(1,101)
Fair Value - Less than 12 months	1,619,979	1,724,170
Unrealized Losses - Less than 12 months	(29,673)	(34,876)
Total Fair Value of Securities in Unrealized Loss Position	1,693,057	1,800,864
Total Unrealized Losses	(30,695)	(35,977)
CMBS [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value - 12 months or greater	53,070	84,640
Unrealized Losses - 12 months or greater	(1,043)	(749)
Fair Value - Less than 12 months	210,308	193,499
Unrealized Losses - Less than 12 months	(2,372)	(2,815)
Total Fair Value of Securities in Unrealized Loss Position	263,378	278,139
Total Unrealized Losses	(3,415)	(3,564)
Non-Agency RMBS [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value - 12 months or greater	13,195	13,642
Unrealized Losses - 12 months or greater	(1,483)	(1,752)
Fair Value - Less than 12 months	6,917	7,194
Unrealized Losses - Less than 12 months	(159)	(271)
Total Fair Value of Securities in Unrealized Loss Position	20,112	20,836
Total Unrealized Losses	(1,642)	(2,023)
ABS [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value - 12 months or greater	173,243	362,110
Unrealized Losses - 12 months or greater	(1,054)	(1,950)
Fair Value - Less than 12 months	278,337	266,763
Unrealized Losses - Less than 12 months	(762)	(893)
Total Fair Value of Securities in Unrealized Loss Position	451,580	628,873
Total Unrealized Losses	(1,816)	(2,843)
Municipals [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value - 12 months or greater	769	774
Unrealized Losses - 12 months or greater	(32)	(29)
Fair Value - Less than 12 months	36,964	68,598
Unrealized Losses - Less than 12 months	(642)	(961)
Total Fair Value of Securities in Unrealized Loss Position	37,733	69,372
Total Unrealized Losses	(674)	(990)
Equity Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value - 12 months or greater	12	4,959
Unrealized Losses - 12 months or greater	(70)	(461)
Fair Value - Less than 12 months	126,849	211,751
Unrealized Losses - Less than 12 months	(7,066)	(11,607)
Total Fair Value of Securities in Unrealized Loss Position	126,861	216,710
Total Unrealized Losses	$ (7,136)	$ (12,068)
Number of Available For Sale Securities In Unrealized Loss Positions | security	3	23
Number of Available For Sale Securities in Unrealized Loss Positions for 12 Months or Greater | security	1	3
Common Stock [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair Value - 12 months or greater	$ 12	$ 0
Unrealized Losses - 12 months or greater	(70)	0
Fair Value - Less than 12 months	27	37
Unrealized Losses - Less than 12 months	(270)	(342)
Total Fair Value of Securities in Unrealized Loss Position	39	37
Total Unrealized Losses	(340)	(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	126,822	123,954
Unrealized Losses - Less than 12 months	(6,796)	(9,092)
Total Fair Value of Securities in Unrealized Loss Position	126,822	123,954
Total Unrealized Losses	$ (6,796)	$ (9,092)