Acquired Intangible Assets and Weighted Average Amortization Periods (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Acquired Finite-Lived Intangible Assets [Line Items]
2011 acquired intangible assets Total	$ 24,827	$ 89,921	$ 29,861
Trade Names
Acquired Finite-Lived Intangible Assets [Line Items]
2011 acquired intangible assets Total	8,973	4,168	6,802
Weighted Average Life	15 years	15 years	13 years
Non-Compete Agreements
Acquired Finite-Lived Intangible Assets [Line Items]
2011 acquired intangible assets Total	470	793	276
Weighted Average Life	3 years	2 years	3 years
Customer Relationships
Acquired Finite-Lived Intangible Assets [Line Items]
2011 acquired intangible assets Total	11,343	53,895	14,832
Weighted Average Life	6 years	7 years	8 years
Unpatented technology and other
Acquired Finite-Lived Intangible Assets [Line Items]
2011 acquired intangible assets Total	4,041	28,048	7,951
Weighted Average Life	8 years	6 years	14 years
Patents
Acquired Finite-Lived Intangible Assets [Line Items]
2011 acquired intangible assets Total		$ 3,017
Weighted Average Life		10 years