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Employee Benefit Plans (Details 2) (USD $)
6 Months Ended
Jun. 30, 2011
Per share weighted average fair value assumptions for stock options and employee stock purchase rights  
Weighted average fair value $ 11.72
Employee Stock Purchase Rights [Member]
 
Per share weighted average fair value assumptions for stock options and employee stock purchase rights  
Expected life (in years) $ 1.85
Implied Volatility 36.00%
Risk-free interest rate 0.56%
Expected dividend yield 0.99%
Weighted average fair value $ 11.11
Employee Stock Option [Member]
 
Per share weighted average fair value assumptions for stock options and employee stock purchase rights  
Expected life (in years) $ 3.6
Implied Volatility 34.00%
Risk-free interest rate 1.56%
Expected dividend yield 0.80%
Weighted average fair value $ 11.72