INVESTMENTS, AVAILABLE-FOR-SALE SECURITIES (Details) (USD $)
In Thousands, unless otherwise specified
Mar. 31, 2015
Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale securities, continuous unrealized loss position, less than 12 months, accumulated loss $ 0 $ 0
Available-for-sale Securities Reconciliation [Abstract]    
Amortized Cost 17,192 17,842
Gross Unrealized Gains 402 380
Gross Unrealized Losses (925) (1,071)
Fair Value 16,669 17,151
Available-for-sale securities, unrealized loss positions    
Aggregate Fair Value 15,825 16,329
Auction Rate Securities [Member]    
Available-for-sale Securities Reconciliation [Abstract]    
Amortized Cost 17,192 17,842
Gross Unrealized Gains 402 380
Gross Unrealized Losses (925) (1,071)
Fair Value 16,669 17,151
Available-for-sale securities, unrealized loss positions    
Aggregate Fair Value $ 15,825 $ 16,329