INVESTMENTS (Details 3) (USD $)	3 Months Ended
	Mar. 31, 2013	Jun. 30, 2013	Dec. 31, 2012
INVESTMENTS
Realized gains on the sale of available-for-sale investments	$ 2,500,000
Disclosure of underlying contractual maturities of investments
Amortized Cost		160,150,000	115,952,000
Fair Value		160,195,000	118,424,000
U.S. Treasuries | Less than 1 year
Disclosure of underlying contractual maturities of investments
Amortized Cost		11,019,000	16,040,000
Fair Value		11,021,000	16,040,000
Certificates of deposit | Less than 1 year
Disclosure of underlying contractual maturities of investments
Amortized Cost		11,515,000	2,201,000
Fair Value		11,515,000	2,201,000
Municipal securities | Less than 1 year
Disclosure of underlying contractual maturities of investments
Amortized Cost		119,854,000	77,038,000
Fair Value		119,897,000	77,027,000
Auction rate securities | Due 11 - 20 years
Disclosure of underlying contractual maturities of investments
Amortized Cost		11,042,000	10,748,000
Fair Value		11,042,000	10,748,000
Auction rate securities | Due 21 - 30 years
Disclosure of underlying contractual maturities of investments
Amortized Cost		6,720,000	9,925,000
Fair Value		$ 6,720,000	$ 12,408,000