Annual report pursuant to Section 13 and 15(d)

Estimated Fair Value of Net Assets Acquired and Liabilities Assumed at Acquisition Dates (Parenthetical) (Detail)

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Estimated Fair Value of Net Assets Acquired and Liabilities Assumed at Acquisition Dates (Parenthetical) (Detail) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2011
Dec. 31, 2010
Schedule of Business Acquisitions, Purchase Price Allocation [Line Items]    
Goodwill, tax deductible $ 44.7 $ 4.4