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Income Taxes (Details) (USD $)
3 Months Ended
Mar. 31, 2012
Mar. 31, 2011
Income Taxes [Line Items]    
Effective tax rate 38.00% 37.00%
Number of weeks of new hire employment required for New Hire Retention Credit 52  
Maximum [Member]
   
Income Taxes [Line Items]    
Tax credit for each worker under New Hire Retention Credit 1,000