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Income Taxes - Summary of Information Related to Interest and Penalties on Uncertain Tax Positions (Detail) (USD $)
In Millions, unless otherwise specified
9 Months Ended
Sep. 30, 2014
Sep. 30, 2013
Dec. 31, 2013
Income Tax Disclosure [Abstract]      
Interest expense $ 0.1 $ (0.1)  
Accrued interest payable $ 0.7   $ 0.6