MARKETABLE SECURITIES (Details 2) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2012 investment	Jun. 30, 2011	Jun. 30, 2012 investment	Jun. 30, 2011	Dec. 31, 2011
Continuous unrealized loss position
Fair Value	$ 11,281,000		$ 11,281,000		$ 24,631,000
Gross Unrealized Losses	(18,000)		(18,000)		(37,000)
Proceeds from maturities and sales of current and non-current available-for-sale marketable securities and related gross realized gains and losses
Proceeds from maturities and sales of available-for-sale marketable securities	21,376,000	215,139,000	47,777,000	413,904,000
Gross realized gains	15,000	1,022,000	1,798,000	1,916,000
Gross realized losses				(18,000)
Net unrealized gains, net of tax, reclassified from other comprehensive income into earnings	100,000	1,300,000	700,000	1,400,000
Number of investments in continuous unrealized loss position for less than 12 months	6		6
Corporate debt securities
Continuous unrealized loss position
Fair Value					12,920,000
Gross Unrealized Losses					(15,000)
States of the U.S. and state political subdivisions
Continuous unrealized loss position
Fair Value	11,281,000		11,281,000		11,711,000
Gross Unrealized Losses	$ (18,000)		$ (18,000)		$ (22,000)