INVESTMENTS (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Amortized Cost
Due in one year or less	$ 12,229
Due after one year through five years	286,581
Due after five years through 10 years	562,899
Due after 10 years	305,922
Total amoritzed cost	1,504,333
Fair Value
Due in one year or less	12,407
Due after one year through five years	292,120
Due after five years through 10 years	572,555
Due after 10 years	309,142
Total fair value	1,532,304	$ 1,495,087
Fair value measured on recurring basis
Available-for-sale
Fair Value	1,901,351	1,905,729
Fair value measured on recurring basis | Significant Unobservable Inputs (Level 3)
INVESTMENTS
Total assets at fair value	0
Debt securities
Available-for-sale
Available-for-sale Securities, Amortized Cost Basis, Total	1,504,333	1,448,204
Gross Unrealized Gains	41,166	53,004
Gross Unrealized Losses	(13,195)	(6,121)
Fair Value	1,532,304	1,495,087
U.S. government
Available-for-sale
Available-for-sale Securities, Amortized Cost Basis, Total	32,708	33,668
Gross Unrealized Gains	328	131
Gross Unrealized Losses		(11)
Fair Value	33,036	33,788
U.S. Agency
Available-for-sale
Available-for-sale Securities, Amortized Cost Basis, Total	13,455	6,385
Gross Unrealized Gains	430	362
Gross Unrealized Losses	(18)
Fair Value	13,867	6,747
Non-U.S. govt. & agency
Available-for-sale
Available-for-sale Securities, Amortized Cost Basis, Total	5,042	9,862
Gross Unrealized Gains		803
Gross Unrealized Losses	(378)
Fair Value	4,664	10,665
ABS/CMBS
Available-for-sale
Available-for-sale Securities, Amortized Cost Basis, Total	83,203	133,894
Gross Unrealized Gains	1,778	1,821
Gross Unrealized Losses	(172)	(411)
Fair Value	84,809	135,304
Agency MBS
Available-for-sale
Available-for-sale Securities, Amortized Cost Basis, Total	253,499	256,443
Gross Unrealized Gains	8,312	9,401
Gross Unrealized Losses	(539)	(1,376)
Fair Value	261,272	264,468
Corporate
Available-for-sale
Available-for-sale Securities, Amortized Cost Basis, Total	599,808	543,183
Gross Unrealized Gains	13,704	23,697
Gross Unrealized Losses	(11,489)	(4,190)
Fair Value	602,023	562,690
Municipal
Available-for-sale
Available-for-sale Securities, Amortized Cost Basis, Total	516,618	464,769
Gross Unrealized Gains	16,614	16,789
Gross Unrealized Losses	(599)	(133)
Fair Value	532,633	481,425
Mtge/ABS/CMBS
Available-for-sale
Available-for-sale Securities, Amortized Cost Basis, Total	336,702
Fair Value	346,080
Equity securities
Available-for-sale
Available-for-sale Securities, Amortized Cost Basis, Total	206,546	193,535
Gross Unrealized Gains	165,428	218,105
Gross Unrealized Losses	(2,927)	(998)
Fair Value	$ 369,047	$ 410,642