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Income Taxes - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
3 Months Ended 9 Months Ended
Sep. 30, 2012
Sep. 30, 2011
Sep. 30, 2012
Sep. 30, 2011
Income Tax [Line Items]        
Income tax provision (benefit) $ 48.0 $ (26.4) $ 55.4 $ (73.8)
Income tax benefit rate   26.00% 4.00% 27.00%
Settlement of tax disputes 2   12  
Increased valuation allowances 36   36  
Statutory U.S. federal tax rate   35.00%   35.00%
Unrecognized tax benefits $ 38