INVESTMENTS (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Amortized Cost
Due in one year or less	$ 17,680
Due after one year through five years	242,863
Due after five years through 10 years	594,841
Due after 10 years	254,433
Total	1,502,504
Fair Value
Due in one year or less	17,855
Due after one year through five years	253,882
Due after five years through 10 years	612,167
Due after 10 years	262,606
Total	1,545,530	1,440,052
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	1,502,504	1,431,049
Gross Unrealized Gains	49,621	37,661
Gross Unrealized Losses	(6,595)	(28,658)
Fair Value	1,545,530	1,440,052
U.S. Agency
Available-for-sale
Available-for-sale Securities, Amortized Cost Basis, Total	6,383	10,513
Gross Unrealized Gains	147	22
Gross Unrealized Losses	(14)	(237)
Fair Value	6,516	10,298
Corporate Debt
Available-for-sale
Available-for-sale Securities, Amortized Cost Basis, Total	563,120	511,748
Gross Unrealized Gains	23,639	22,302
Gross Unrealized Losses	(2,603)	(8,012)
Fair Value	584,156	526,038
Mtge/ABS/CMBS
Available-for-sale
Available-for-sale Securities, Amortized Cost Basis, Total	392,687	350,187
Gross Unrealized Gains	9,627	8,188
Gross Unrealized Losses	(3,294)	(7,650)
Fair Value	399,020	350,725
Non-U.S. govt. & agency
Available-for-sale
Available-for-sale Securities, Amortized Cost Basis, Total	9,861	13,306
Gross Unrealized Gains	696	437
Gross Unrealized Losses		(65)
Fair Value	10,557	13,678
U.S. government
Available-for-sale
Available-for-sale Securities, Amortized Cost Basis, Total	32,082	17,086
Gross Unrealized Gains	120	217
Gross Unrealized Losses	(39)
Fair Value	32,163	17,303
Municipal
Available-for-sale
Available-for-sale Securities, Amortized Cost Basis, Total	498,371	528,209
Gross Unrealized Gains	15,392	6,495
Gross Unrealized Losses	(645)	(12,694)
Fair Value	513,118	522,010
Equity securities
Available-for-sale
Available-for-sale Securities, Amortized Cost Basis, Total	214,239	218,848
Gross Unrealized Gains	205,253	200,081
Gross Unrealized Losses	(470)	(275)
Fair Value	$ 419,022	$ 418,654