MARKETABLE SECURITIES AND FAIR VALUE MEASUREMENTS - Roll forward auction rate securities (Details 3) (Auction rate securities, Fair Value, Inputs, Level 3, USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Auction rate securities | Fair Value, Inputs, Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance	$ 1,789	$ 1,676
Gain (loss) on auction rate securities	(2)	85
Balance	$ 1,787	$ 1,761