MARKETABLE SECURITIES (Details 2) (USD $)	3 Months Ended
	Mar. 31, 2012 investment	Mar. 31, 2011	Dec. 31, 2011
Continuous unrealized loss position
Fair Value	$ 15,678,000		$ 24,631,000
Gross Unrealized Losses	(86,000)		(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	26,401,000	198,765,000
Gross realized gains	1,783,000	894,000
Gross realized losses		(18,000)
Net unrealized gains, net of tax, reclassified from other comprehensive income into earnings	100,000	100,000
Number of investments in continuous unrealized loss position for less than 12 months	6
Corporate debt securities
Continuous unrealized loss position
Fair Value	2,000,000		12,920,000
Gross Unrealized Losses	(1,000)		(15,000)
States of the U.S. and state political subdivisions
Continuous unrealized loss position
Fair Value	13,678,000		11,711,000
Gross Unrealized Losses	$ (85,000)		$ (22,000)