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Goodwill and Other Intangible Assets, Net - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Goodwill And Other Intangible Assets [Line Items]      
Amortization expense $ 6.1 $ 6.1 $ 6.1
Estimated annual amortization, 2013 6.1    
Estimated annual amortization, 2014 4.7    
Estimated annual amortization, 2015 4.7    
Estimated annual amortization, 2016 4.7    
Estimated annual amortization, 2017 $ 4.7