Quarterly report pursuant to Section 13 or 15(d)

Income Taxes (Details)

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Income Taxes (Details) (USD $)
3 Months Ended 6 Months Ended
Jun. 30, 2012
Jun. 30, 2011
Jun. 30, 2012
Jun. 30, 2011
Summary of Provision for Income Taxes        
Provision for income taxes $ 49,286,000 $ 48,980,000 $ 101,463,000 $ 83,725,000
Gross Unrecognized Tax Benefits Reconcilement [Line Items]        
Unrecognized Tax Benefits, Ending Balance 11,900,000   11,900,000  
Provision (benefit) for income taxes reconcilement        
Provision for income taxes 49,286,000 48,980,000 101,463,000 83,725,000
Income Taxes Textuals [Abstract]        
Total interest accrued on the unrecognized tax benefits $ 2,600,000   $ 2,600,000