INVESTMENTS (Details 4) (USD $)	3 Months Ended
	Mar. 31, 2013	Jun. 30, 2012	Jun. 30, 2013	Dec. 31, 2012	Dec. 31, 2011
Fixed income securities in unrealized loss positions
Total Cost or Amortized Cost			$ 643,345,000	$ 90,225,000
Fair Value			618,895,000	88,967,000
Unrealized Loss			(24,450,000)	(1,258,000)
Cash		32,175,000	12,757,000	44,314,000	81,184,000
Short-term investments, at cost			10,816,000	30,462,000
Other-than-temporary impairment (OTTI) losses recognized in net earnings or other comprehensive earnings	0	1,200,000
Unrealized loss on securities in unrealized loss position for twelve consecutive month or longer				33,000
Other-than-temporary impairment charges for equity securities no longer intended to be held until recovery		1,200,000
Subtotal, debt securities
Fixed income securities in unrealized loss positions
Total Cost or Amortized Cost			640,676,000	73,143,000
Fair Value			616,582,000	72,760,000
Unrealized Loss			(24,094,000)	(383,000)
Percent to Total			100.00%
Number of unrealized loss positions			283
Number of securities in unrealized loss positions for 12 months or longer			0
Unrealized loss on securities in unrealized loss position for twelve consecutive month or longer				33,000
Subtotal, debt securities | Maximum
Fixed income securities in unrealized loss positions
Unrealized losses as percentage of fixed income portfolio cost basis			1.70%
Subtotal, debt securities | NAIC Rating 1
Fixed income securities in unrealized loss positions
Total Cost or Amortized Cost			618,529,000
Fair Value			595,416,000
Unrealized Loss			(23,113,000)
Percent to Total			95.90%
Subtotal, debt securities | NAIC Rating 2
Fixed income securities in unrealized loss positions
Total Cost or Amortized Cost			22,147,000
Fair Value			21,166,000
Unrealized Loss			(981,000)
Percent to Total			4.10%
Common Stock
Fixed income securities in unrealized loss positions
Unrealized Loss			$ (400,000)
Number of unrealized loss positions			1
Number of securities in unrealized loss positions for 12 months or longer			0