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Employee Benefit Plans (Details 2) (USD $)
9 Months Ended
Sep. 30, 2011
Per share weighted average fair value assumptions for stock options and employee stock purchase rights 
Weighted average fair value$ 11.72[1]
Employee Stock Purchase Rights [Member]
 
Per share weighted average fair value assumptions for stock options and employee stock purchase rights 
Expected life (in years)1.77
Implied Volatility36.00%
Risk-free interest rate0.53%
Expected dividend yield0.99%
Weighted average fair value$ 11.07
Employee Stock Option [Member]
 
Per share weighted average fair value assumptions for stock options and employee stock purchase rights 
Expected life (in years)3.60
Implied Volatility34.00%
Risk-free interest rate1.56%
Expected dividend yield0.80%
Weighted average fair value$ 11.72
[1]Less than one million stock options were granted in the nine months ended September 30, 2011.