INVESTMENTS (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Amortized Cost
Due in one year or less	$ 11,557
Due after one year through five years	211,437
Due after five years through 10 years	618,409
Due after 10 years	269,107
Total amortized cost	1,485,626
Fair Value
Due in one year or less	11,628
Due after one year through five years	221,664
Due after five years through 10 years	642,994
Due after 10 years	274,896
Total fair value	1,534,622	1,440,052
Fair value measured on recurring basis | Significant Unobservable Inputs (Level 3)
INVESTMENTS
Total assets at fair value	0
Fixed income securities
Available-for-sale
Cost or Amortized Cost	1,485,626	1,431,049
Gross Unrealized Gains	54,603	37,661
Gross Unrealized Losses	(5,607)	(28,658)
Fair Value	1,534,622	1,440,052
U.S. agency
Available-for-sale
Cost or Amortized Cost	3,883	10,513
Gross Unrealized Gains	99	22
Gross Unrealized Losses	(1)	(237)
Fair Value	3,981	10,298
Corporate
Available-for-sale
Cost or Amortized Cost	550,687	511,748
Gross Unrealized Gains	28,919	22,302
Gross Unrealized Losses	(797)	(8,012)
Fair Value	578,809	526,038
Mtge/ABS/CMBS
Available-for-sale
Cost or Amortized Cost	375,116	350,187
Gross Unrealized Gains	11,242	8,188
Gross Unrealized Losses	(2,918)	(7,650)
Fair Value	383,440	350,725
Non-U.S. govt. & agency
Available-for-sale
Cost or Amortized Cost	13,853	13,306
Gross Unrealized Gains	1,064	437
Gross Unrealized Losses		(65)
Fair Value	14,917	13,678
U.S. government
Available-for-sale
Cost or Amortized Cost	31,571	17,086
Gross Unrealized Gains	168	217
Gross Unrealized Losses	(10)
Fair Value	31,729	17,303
Municipal
Available-for-sale
Cost or Amortized Cost	510,516	528,209
Gross Unrealized Gains	13,111	6,495
Gross Unrealized Losses	(1,881)	(12,694)
Fair Value	521,746	522,010
Equity securities
Available-for-sale
Cost or Amortized Cost	218,797	218,848
Gross Unrealized Gains	217,731	200,081
Gross Unrealized Losses	(66)	(275)
Fair Value	$ 436,462	$ 418,654