Aggregate Allocation of the Purchase Price of Acquisitions to Intangible Assets (Parenthetical) (Detail)	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Developed technology
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted-average useful life (in years)	3.2	4.7	3.5
Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted-average useful life (in years)	4.0	6.4	6.1
Tradename and trademark
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted-average useful life (in years)	2.6	2.5	5.6
Non-competition agreements
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted-average useful life (in years)			2.5
Other
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted-average useful life (in years)		2.1