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Income Taxes - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
Mar. 31, 2013
Dec. 31, 2012
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items]    
Liability for unrecognized tax benefit $ 7.8 $ 8.3
Items generating unrecognized tax benefits 6.6 7.2
Interest and related penalties $ 1.2 $ 1.1