INVESTMENTS (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Amortized Cost
Due in one year or less	$ 9,309
Due after one year through five years	259,490
Due after five years through 10 years	599,500
Due after 10 years	326,606
Total amoritzed cost	1,515,002
Fair Value
Due in one year or less	9,391
Due after one year through five years	265,403
Due after five years through 10 years	608,967
Due after 10 years	326,125
Total fair value	1,537,365	$ 1,495,087
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	1,515,002	1,448,204
Gross Unrealized Gains	35,907	53,004
Gross Unrealized Losses	(13,544)	(6,121)
Fair Value	1,537,365	1,495,087
U.S. government
Available-for-sale
Available-for-sale Securities, Amortized Cost Basis, Total	30,281	33,668
Gross Unrealized Gains	129	131
Gross Unrealized Losses	(10)	(11)
Fair Value	30,400	33,788
U.S. Agency
Available-for-sale
Available-for-sale Securities, Amortized Cost Basis, Total	13,499	6,385
Gross Unrealized Gains	229	362
Gross Unrealized Losses	(84)
Fair Value	13,644	6,747
Non-U.S. govt. & agency
Available-for-sale
Available-for-sale Securities, Amortized Cost Basis, Total	1,893	9,862
Gross Unrealized Gains		803
Gross Unrealized Losses	(53)
Fair Value	1,840	10,665
ABS/CMBS
Available-for-sale
Available-for-sale Securities, Amortized Cost Basis, Total	87,214	133,894
Gross Unrealized Gains	1,429	1,821
Gross Unrealized Losses	(344)	(411)
Fair Value	88,299	135,304
Agency MBS
Available-for-sale
Available-for-sale Securities, Amortized Cost Basis, Total	232,883	256,443
Gross Unrealized Gains	7,680	9,401
Gross Unrealized Losses	(1,383)	(1,376)
Fair Value	239,180	264,468
Corporate
Available-for-sale
Available-for-sale Securities, Amortized Cost Basis, Total	595,886	543,183
Gross Unrealized Gains	14,694	23,697
Gross Unrealized Losses	(8,620)	(4,190)
Fair Value	601,960	562,690
Municipal
Available-for-sale
Available-for-sale Securities, Amortized Cost Basis, Total	553,346	464,769
Gross Unrealized Gains	11,746	16,789
Gross Unrealized Losses	(3,050)	(133)
Fair Value	562,042	481,425
Mtge/ABS/CMBS
Available-for-sale
Available-for-sale Securities, Amortized Cost Basis, Total	320,097
Fair Value	327,479
Equity securities
Available-for-sale
Available-for-sale Securities, Amortized Cost Basis, Total	198,607	193,535
Gross Unrealized Gains	193,648	218,105
Gross Unrealized Losses	(1,103)	(998)
Fair Value	$ 391,152	$ 410,642