Quarterly report pursuant to Section 13 or 15(d)

STOCKHOLDERS' EQUITY (Details 2)

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STOCKHOLDERS' EQUITY (Details 2) (USD $)
 3 Months Ended 12 Months Ended
Mar. 31, 2013
Mar. 31, 2012
Dec. 31, 2012
Aggregate Intrinsic Value      
Proceeds received upon exercise of stock options $ 6,000    
Tax benefits from share-based payments 2,700,000 2,600,000  
Stock options
      
Employee stock incentive plans      
Award vesting period 5 years    
Expiration term 10 years    
Common stock issued upon exercise of stock options by employees (in shares) 1,000 13,000  
Options activity outstanding of stock option plan      
Balance outstanding at the beginning of the period (in shares) 1,000    
Exercised (in shares) (1,000) (13,000)  
Balance outstanding at the end of the period (in shares)     1,000
Weighted-Average Exercise Price      
Balance at the beginning of the period (in dollars per share) $ 5.52    
Exercised (in dollars per share) $ 5.52    
Balance at the end of the period (in dollars per share)     $ 5.52
Weighted-Average Remaining Contractual Term      
Balance at the beginning of the period     3 months 29 days
Balance at the end of the period     3 months 29 days
Aggregate Intrinsic Value      
Balance at the beginning of the period 18,000    
Exercised 20,000 217,000  
Balance at the end of the period     18,000
Proceeds received upon exercise of stock options 10,000 10,000  
Time lapse restricted shares (TLRS's)
      
Aggregate Intrinsic Value      
Pre-tax compensation expense 2,546,000 2,372,000  
Tax benefit (980,000) (913,000)  
Restricted stock expense, net of tax 1,566,000 1,459,000  
Weighted-Average Grant-Date Fair Value      
Unrecognized compensation cost $ 39,300,000   $ 30,900,000
Unrecognized compensation cost, period for recognition 4 years 4 months 24 days   4 years 1 month 6 days
Restricted Stock Units
      
Unvested restricted stock activity      
Balance outstanding at the beginning of the period (in shares) 2,743,000    
Forfeited (in shares) (17,000)    
Vested (in shares) (572,000)    
Granted (in shares) 463,000    
Balance outstanding at the end of the period (in shares) 2,617,000    
Weighted-Average Grant-Date Fair Value      
Balance at the beginning of the period (in dollars per share) $ 16.41    
Forfeited (in dollars per share) $ 18.03    
Vested (in dollars per share) $ 12.95    
Granted (in dollars per share) $ 23.75    
Balance at the end of the period (in dollars per share) $ 18.45