v2.4.0.6
STOCK-BASED COMPENSATION (Details 4) (USD $)
12 Months Ended
Dec. 31, 2012
Y
Dec. 31, 2011
Dec. 31, 2010
Restricted and deferred stock units
     
Shares      
Outstanding at the beginning of the period (in shares) 792,815    
Granted (in shares) 409,351 290,003 154,048
Vested and released (in shares) (460,804)    
Forfeited (in shares) (24,455)    
Outstanding at the end of the period (in shares) 716,907 792,815  
Vested or expected to vest at the end of the period (in shares) 710,894    
Weighted Average Remaining Contractual Terms      
Outstanding at the end of the period (in years) 1.6    
Vested or expected to vest at the end of the period (in years) 1.5    
Weighted Average Grant Date Fair Value      
Outstanding at the beginning of the period (in dollars per share) $ 17.00    
Granted (in dollars per share) $ 30.18 $ 27.55 $ 16.37
Vested and released (in dollars per share) $ 11.35    
Forfeited (in dollars per share) $ 25.86    
Outstanding at the end of the period (in dollars per share) $ 27.86 $ 17.00  
Vested or expected to vest at the end of the period (in dollars per share) $ 27.84    
Aggregate Intrinsic Value      
Outstanding at the end of the period (in dollars) $ 29,594,000    
Vested or expected to vest at the end of the period (in dollars) 29,346,000    
Minimum vesting period P1Y    
Maximum vesting period P3Y    
Total intrinsic value of share awards vested (in dollars) $ 15,800,000 $ 8,100,000 $ 5,600,000
Restricted stock surrendered in satisfaction of required minimum tax withholding obligations 152,759 126,934 128,654
PRSUs
     
The weighted average assumptions used in the Monte Carlo simulation model      
Risk-free interest rate (as a percent) 0.44% 0.95%  
Expected life (in years) 3.0 3.0  
Expected volatility (as a percent) 45.00% 45.00%  
Expected dividend yield (as a percent) 1.07%    
PRSUs | Minimum
     
Aggregate Intrinsic Value      
Percentage multiplied to target award for determining the number of shares subject to award 0.00%    
PRSUs | Maximum
     
Aggregate Intrinsic Value      
Percentage multiplied to target award for determining the number of shares subject to award 150.00%