Acquired Intangible Assets and Weighted Average Amortization Periods (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012
Acquired Finite-Lived Intangible Assets [Line Items]
Total	$ 24,827
Trade Names
Acquired Finite-Lived Intangible Assets [Line Items]
Total	8,973
Weighted Average Life	15 years
Noncompete Agreements
Acquired Finite-Lived Intangible Assets [Line Items]
Total	470
Weighted Average Life	3 years
Customer Relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Total	11,343
Weighted Average Life	6 years
Unpatented Technology
Acquired Finite-Lived Intangible Assets [Line Items]
Total	$ 4,041
Weighted Average Life	8 years