Aggregate Purchase Price of the Acquisitions (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 Year
Schedule of Business Acquisitions, Cost of Acquired Entity [Line Items]
Acquired intangible assets, weighted-average amortization period (in years)	8
Contingent liability related to historic tax exposures	$ 38
Minimum
Schedule of Business Acquisitions, Cost of Acquired Entity [Line Items]
Acquired intangible assets, amortization period (in years)	2
Maximum
Schedule of Business Acquisitions, Cost of Acquired Entity [Line Items]
Acquired intangible assets, amortization period (in years)	10