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Goodwill And Other Intangible Assets - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Goodwill And Intangible Assets [Line Items]      
Intangible asset amortization expense $ 3.1 $ 1.4 $ 0.8
Estimated amortization of intangible assets, 2013 3.4    
Estimated amortization of intangible assets, 2014 3.2    
Estimated amortization of intangible assets, 2015 3.1    
Estimated amortization of intangible assets, 2016 3.0    
Estimated amortization of intangible assets, 2017 $ 3.0