INVESTMENTS Unrealized Losses (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013	Dec. 31, 2012
Investment positions with unrealized losses
Unrealized losses relative to total invested assets (as a percent)	0.30%
Fair value
Less than 12 months	$ 294,600	$ 682,254
12 Months and Greater	162,060	3,188
Total Fair value	456,660	685,442
Cost or amortized Cost
Less than 12 months	297,578	710,949
12 months and greater	166,147	3,426
Total Cost or Amortized Cost	463,725	714,375
Unrealized Loss
Less than 12 months	(2,978)	(28,695)
12 Months and Greater	(4,087)	(238)
Total Unrealized Loss	(7,065)	(28,933)
Cash and Short-term Investments
Cash	77,037	39,469	87,398	44,314
Short-term investments, at cost which approximates fair value	10,063	23,232
Debt securities
Fair value
Less than 12 months	282,965	679,860
12 Months and Greater	162,060	3,188
Total Fair value	445,025	683,048
Cost or amortized Cost
Less than 12 months	285,473	708,280
12 months and greater	166,147	3,426
Total Cost or Amortized Cost	451,620	711,706
Unrealized Loss
Less than 12 months	(2,508)	(28,420)
12 Months and Greater	(4,087)	(238)
Total Unrealized Loss	(6,595)	(28,658)
Percent to Total	100.00%
Debt securities | NAIC Rating 1 | AAA/AA/A | Aaa/Aa/A
Fair value
Total Fair value	349,481
Cost or amortized Cost
Total Cost or Amortized Cost	354,379
Unrealized Loss
Total Unrealized Loss	(4,898)
Percent to Total	74.30%
Debt securities | NAIC Rating 2 | BBB | Baa
Fair value
Total Fair value	37,081
Cost or amortized Cost
Total Cost or Amortized Cost	37,566
Unrealized Loss
Total Unrealized Loss	(485)
Percent to Total	7.40%
Debt securities | NAIC Rating 3 | BB | Ba
Fair value
Total Fair value	35,139
Cost or amortized Cost
Total Cost or Amortized Cost	35,807
Unrealized Loss
Total Unrealized Loss	(668)
Percent to Total	10.10%
Debt securities | NAIC Rating 4 | B
Fair value
Total Fair value	22,120
Cost or amortized Cost
Total Cost or Amortized Cost	22,598
Unrealized Loss
Total Unrealized Loss	(478)
Percent to Total	7.20%
Debt securities | NAIC Rating 5 | CCC or lower
Fair value
Total Fair value	1,204
Cost or amortized Cost
Total Cost or Amortized Cost	1,270
Unrealized Loss
Total Unrealized Loss	(66)
Percent to Total	1.00%
U.S. government
Fair value
Less than 12 months	18,556
Total Fair value	18,556
Cost or amortized Cost
Less than 12 months	18,595
Total Cost or Amortized Cost	18,595
Unrealized Loss
Less than 12 months	(39)
Total Unrealized Loss	(39)
U.S. Agency
Fair value
Less than 12 months	1,871	5,760
Total Fair value	1,871	5,760
Cost or amortized Cost
Less than 12 months	1,885	5,997
Total Cost or Amortized Cost	1,885	5,997
Unrealized Loss
Less than 12 months	(14)	(237)
Total Unrealized Loss	(14)	(237)
Non-U.S. govt. & agency
Fair value
Less than 12 months		1,825
Total Fair value		1,825
Cost or amortized Cost
Less than 12 months		1,890
Total Cost or Amortized Cost		1,890
Unrealized Loss
Less than 12 months		(65)
Total Unrealized Loss		(65)
Mortgage-backed
Fair value
Less than 12 months	27,741	118,283
12 Months and Greater	70,754
Total Fair value	98,495	118,283
Cost or amortized Cost
Less than 12 months	27,848	124,034
12 months and greater	73,223
Total Cost or Amortized Cost	101,071	124,034
Unrealized Loss
Less than 12 months	(107)	(5,751)
12 Months and Greater	(2,469)
Total Unrealized Loss	(2,576)	(5,751)
ABS/CMBS
Fair value
Less than 12 months	46,758	54,115
12 Months and Greater	19,100
Total Fair value	65,858	54,115
Cost or amortized Cost
Less than 12 months	47,038	56,014
12 months and greater	19,538
Total Cost or Amortized Cost	66,576	56,014
Unrealized Loss
Less than 12 months	(280)	(1,899)
12 Months and Greater	(438)
Total Unrealized Loss	(718)	(1,899)
Corporate Debt
Fair value
Less than 12 months	157,718	190,470
12 Months and Greater	22,591	2,245
Total Fair value	180,309	192,715
Cost or amortized Cost
Less than 12 months	159,729	198,250
12 months and greater	23,183	2,477
Total Cost or Amortized Cost	182,912	200,727
Unrealized Loss
Less than 12 months	(2,011)	(7,780)
12 Months and Greater	(592)	(232)
Total Unrealized Loss	(2,603)	(8,012)
Municipal
Fair value
Less than 12 months	30,321	309,407
12 Months and Greater	49,615	943
Total Fair value	79,936	310,350
Cost or amortized Cost
Less than 12 months	30,378	322,095
12 months and greater	50,203	949
Total Cost or Amortized Cost	80,581	323,044
Unrealized Loss
Less than 12 months	(57)	(12,688)
12 Months and Greater	(588)	(6)
Total Unrealized Loss	(645)	(12,694)
Equity securities
Fair value
Less than 12 months	11,635	2,394
Total Fair value	11,635	2,394
Cost or amortized Cost
Less than 12 months	12,105	2,669
Total Cost or Amortized Cost	12,105	2,669
Unrealized Loss
Less than 12 months	(470)	(275)
Total Unrealized Loss	$ (470)	$ (275)