FAIR VALUE (Details) (USD $)
 3 Months Ended 12 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Dec. 31, 2008
Unobservable inputs assets (level 3) [Roll forward]                  
Beginning balance $ 17,151,000 $ 21,990,000 $ 21,990,000            
Change in unrealized gain (loss) included in accumulated other comprehensive loss 168,000 178,000              
Settlements (650,000) 0              
Ending balance 16,669,000 22,168,000              
Auction rate securities variable rate debt instruments interest rate reset period 28 days                
The minimum contractual maturities on underlying securities involved in auction rate securities 20 years                
Par value of company held auction rate securities 18,000,000                
Temporary impairment of the auction rates security investments, net of unrealized gain (523,000)   (691,000)            
Fair Value, Measurements, Recurring [Member]                  
Assets:                  
Total assets measured at fair value 558,440,000   544,163,000            
Fair Value, Measurements, Recurring [Member] | Cash [Member]                  
Assets:                  
Total assets measured at fair value 336,204,000   160,275,000            
Fair Value, Measurements, Recurring [Member] | Money Market Funds [Member]                  
Assets:                  
Total assets measured at fair value 155,816,000   310,482,000            
Fair Value, Measurements, Recurring [Member] | Commercial Paper [Member]                  
Assets:                  
Total assets measured at fair value 49,751,000   56,255,000            
Fair Value, Measurements, Recurring [Member] | Auction Rate Securities [Member]                  
Assets:                  
Total assets measured at fair value 16,669,000   17,151,000            
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]                  
Assets:                  
Total assets measured at fair value 541,771,000   527,012,000            
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Cash [Member]                  
Assets:                  
Total assets measured at fair value 336,204,000   160,275,000            
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member]                  
Assets:                  
Total assets measured at fair value 155,816,000   310,482,000            
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Commercial Paper [Member]                  
Assets:                  
Total assets measured at fair value 49,751,000   56,255,000            
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Auction Rate Securities [Member]                  
Assets:                  
Total assets measured at fair value 0   0            
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]                  
Assets:                  
Total assets measured at fair value 0   0            
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Cash [Member]                  
Assets:                  
Total assets measured at fair value 0   0            
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Money Market Funds [Member]                  
Assets:                  
Total assets measured at fair value 0   0            
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Commercial Paper [Member]                  
Assets:                  
Total assets measured at fair value 0   0            
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Auction Rate Securities [Member]                  
Assets:                  
Total assets measured at fair value 0   0            
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]                  
Assets:                  
Total assets measured at fair value 16,669,000   17,151,000            
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Cash [Member]                  
Assets:                  
Total assets measured at fair value 0   0            
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Money Market Funds [Member]                  
Assets:                  
Total assets measured at fair value 0   0            
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Commercial Paper [Member]                  
Assets:                  
Total assets measured at fair value 0   0            
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Auction Rate Securities [Member]                  
Assets:                  
Total assets measured at fair value 16,669,000   17,151,000            
Auction Rate Securities [Member]                  
Unobservable inputs assets (level 3) [Roll forward]                  
Beginning balance 17,151,000 21,990,000 21,990,000 21,662,000 24,584,000 29,189,000 29,724,000 29,340,000 53,975,000
Change in unrealized gain (loss) included in accumulated other comprehensive loss 168,000   836,000 378,000 836,000 245,000 40,000 684,000 (3,710,000)
Settlements (650,000)   (5,675,000) (50,000) (4,200,000) (4,850,000) (575,000) (300,000) (20,925,000)
Auction rate securities upon acquisition         442,000        
Ending balance $ 16,669,000   $ 17,151,000 $ 21,990,000 $ 21,662,000 $ 24,584,000 $ 29,189,000 $ 29,724,000 $ 29,340,000
Discount rate (in percent) 4.00%   4.10%