MARKETABLE SECURITIES AND FAIR VALUE MEASUREMENTS - Summary of unobservable inputs of fair value measurements (Details 4) (Fair Value, Inputs, Level 3, Auction rate securities, USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Auction rate securities-long term	$ 1,789
Fair value measurements, valuation techniques	Discounted cash flow
Discounted cash flow
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Maximum rate	1.62%
Discounted cash flow | Minimum
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Liquidity risk premium	3.50%
Probability of earning maximum rate until maturity	0.06%
Probability of principal returned prior to maturity	86.34%
Probability of default	11.57%
Discounted cash flow | Maximum
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Liquidity risk premium	4.50%
Probability of earning maximum rate until maturity	0.09%
Probability of principal returned prior to maturity	88.38%
Probability of default	13.57%