Goodwill and Other Intangible Assets - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Intangible Assets by Major Class [Line Items]
Amortization	$ 5,561	$ 4,209	$ 15,675	$ 11,102
Customer relationships
Intangible Assets by Major Class [Line Items]
Finite lived intangible assets, weighted average remaining useful life			30 years
Customer relationships | Minimum
Intangible Assets by Major Class [Line Items]
Finite lived intangible assets useful life			15 years
Customer relationships | Maximum
Intangible Assets by Major Class [Line Items]
Finite lived intangible assets useful life			40 years
Covenants not-to-compete
Intangible Assets by Major Class [Line Items]
Finite lived intangible assets, weighted average remaining useful life			4 years 9 months 18 days
Covenants not-to-compete | Minimum
Intangible Assets by Major Class [Line Items]
Finite lived intangible assets useful life			4 years
Covenants not-to-compete | Maximum
Intangible Assets by Major Class [Line Items]
Finite lived intangible assets useful life			14 years
Tradenames
Intangible Assets by Major Class [Line Items]
Finite lived intangible assets useful life			15 years
Finite lived intangible assets, weighted average remaining useful life			16 years 9 months 18 days
Tradenames | Minimum
Intangible Assets by Major Class [Line Items]
Finite lived intangible assets useful life			15 years
Tradenames | Maximum
Intangible Assets by Major Class [Line Items]
Finite lived intangible assets useful life			40 years