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Income Taxes - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
3 Months Ended 12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Sep. 30, 2012
Income Taxes [Line Items]      
United States statutory tax rate 35.00% 35.00%  
Company's effective tax rates 30.60% 32.80%  
Additional research experimentation tax credits     $ 0.3
Effective Income Tax Rate Excluding Impact of Prior Period Credits
     
Income Taxes [Line Items]      
Company's effective tax rates 31.60%