INVESTMENTS (Details 3) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
INVESTMENTS
Unrealized losses relative to total invested assets (as a percent)	1.30%
Fair value
Less than 12 months	$ 618,895	$ 88,007
12 Months and Greater		960
Total Fair value	618,895	88,967
Cost or amortized cost
Less than 12 months	643,345	89,232
12 Months and Greater		993
Total Cost or Amortized Cost	643,345	90,225
Unrealized Loss
Less than 12 months	(24,450)	(1,225)
12 Months and Greater		(33)
Total Unrealized Loss	(24,450)	(1,258)
Maximum
Unrealized Loss
Fair value of trading securities	100	100
U.S. Government
Fair value
Less than 12 months	2,244	749
Total Fair value	2,244	749
Cost or amortized cost
Less than 12 months	2,246	749
Total Cost or Amortized Cost	2,246	749
Unrealized Loss
Less than 12 months	(2)
Total Unrealized Loss	(2)
U.S. Agency
Fair value
Less than 12 months	3,943
Total Fair value	3,943
Cost or amortized cost
Less than 12 months	3,996
Total Cost or Amortized Cost	3,996
Unrealized Loss
Less than 12 months	(53)
Total Unrealized Loss	(53)
Mortgage-backed
Fair value
Less than 12 months	94,673
Total Fair value	94,673
Cost or amortized cost
Less than 12 months	97,854
Total Cost or Amortized Cost	97,854
Unrealized Loss
Less than 12 months	(3,181)
Total Unrealized Loss	(3,181)
ABS/CMBS
Fair value
Less than 12 months	48,449	18
Total Fair value	48,449	18
Cost or amortized cost
Less than 12 months	50,639	18
Total Cost or Amortized Cost	50,639	18
Unrealized Loss
Less than 12 months	(2,190)
Total Unrealized Loss	(2,190)
Corporate
Fair value
Less than 12 months	184,781	35,969
12 Months and Greater		960
Total Fair value	184,781	36,929
Cost or amortized cost
Less than 12 months	192,210	36,162
12 Months and Greater		993
Total Cost or Amortized Cost	192,210	37,155
Unrealized Loss
Less than 12 months	(7,429)	(193)
12 Months and Greater		(33)
Total Unrealized Loss	(7,429)	(226)
Municipal
Fair value
Less than 12 months	282,492	35,064
Total Fair value	282,492	35,064
Cost or amortized cost
Less than 12 months	293,731	35,221
Total Cost or Amortized Cost	293,731	35,221
Unrealized Loss
Less than 12 months	(11,239)	(157)
Total Unrealized Loss	(11,239)	(157)
Subtotal, debt securities
Fair value
Less than 12 months	616,582	71,800
12 Months and Greater		960
Total Fair value	616,582	72,760
Cost or amortized cost
Less than 12 months	640,676	72,150
12 Months and Greater		993
Total Cost or Amortized Cost	640,676	73,143
Unrealized Loss
Less than 12 months	(24,094)	(350)
12 Months and Greater		(33)
Total Unrealized Loss	(24,094)	(383)
Equity securities
Fair value
Less than 12 months	2,313	16,207
Total Fair value	2,313	16,207
Cost or amortized cost
Less than 12 months	2,669	17,082
Total Cost or Amortized Cost	2,669	17,082
Unrealized Loss
Less than 12 months	(356)	(875)
Total Unrealized Loss	$ (356)	$ (875)