Quarterly report pursuant to Section 13 or 15(d)

Goodwill and Intangible Assets - Additional Information (Detail)

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Goodwill and Intangible Assets - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
3 Months Ended 9 Months Ended
Sep. 30, 2012
Sep. 30, 2011
Sep. 30, 2012
Sep. 30, 2011
Goodwill and Intangible Assets Disclosure [Line Items]        
Amortization expense related to purchased intangible assets $ 22.1 $ 21.9 $ 66.8 $ 67.9