Quarterly report pursuant to Section 13 or 15(d)

STOCKHOLDERS' EQUITY (Details 2)

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STOCKHOLDERS' EQUITY (Details 2) (USD $)
Share data in Thousands, except Per Share data, unless otherwise specified
 3 Months Ended 12 Months Ended
Mar. 31, 2012
Y
Mar. 31, 2011
Dec. 31, 2011
Y
Options activity outstanding of stock option plan      
Exercised (in shares) (13) (10)  
Aggregate Intrinsic Value      
Tax benefits from share-based payments $ 2,600,000 $ 70,000  
Time lapse restricted shares (TLRS's)
      
Employee stock incentive plans      
Pre-tax compensation expense 2,372,000 1,882,000  
Tax benefit (913,000) (724,000)  
Restricted stock expense, net of tax 1,459,000 1,158,000  
Weighted-Average Grant-Date Fair Value      
Unrecognized compensation cost 39,400,000   24,400,000
Unrecognized compensation cost, period for recognition (in years) 4.3   4.1
Restricted Stock Units
      
Unvested restricted stock activity      
Balance outstanding at the beginning of the period (in shares) 2,686    
Forfeited (in shares) (15)    
Vested (in shares) (564)    
Granted (in shares) 776    
Balance outstanding at the end of the period (in shares) 2,883    
Weighted-Average Grant-Date Fair Value      
Balance at the beginning of the period (in dollars per share) $ 13.31    
Forfeited (in dollars per share) $ 19.30    
Vested (in dollars per share) $ 10.88    
Granted (in dollars per share) $ 22.69    
Balance at the end of the period (in dollars per share) $ 16.28    
Stock options
      
Employee stock incentive plans      
Award vesting period (in years)     5 years
Award expiration period (in years)     P10Y
Options activity outstanding of stock option plan      
Balance outstanding at the beginning of the period (in shares) 33    
Exercised (in shares) (13)    
Balance outstanding at the end of the period (in shares) 20   33
Exercisable (in shares) 20    
Weighted-Average Exercise Price      
Balance at the beginning of the period (in dollars per share) $ 5.26    
Exercised (in dollars per share) $ 4.86    
Balance at the end of the period (in dollars per share) $ 5.52   $ 5.26
Exercisable (in dollars per share) $ 5.52    
Weighted-Average Remaining Contractual Term (in years)      
Balance at the beginning of the period (in years) 0.93    
Balance at the end of the period (in years) 0.83   0.93
Exercisable (in years) 0.83    
Aggregate Intrinsic Value      
Balance at the beginning of the period 553,000    
Exercised 217,000 34,000  
Balance at the end of the period 311,000   553,000
Exercisable 311,000    
Cash receipts from options exercised $ 10,000 $ 10,000