Carrying Amount and Accumulated Amortization of Other Intangible Assets (Detail) (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Indefinite-lived Intangible Assets by Major Class [Line Items]
Gross Carrying Amount	$ 52,697	$ 48,291
Accumulated Amortization	(32,914)	(27,843)
Net Balance	19,783	20,448
Customer relationships
Indefinite-lived Intangible Assets by Major Class [Line Items]
Gross Carrying Amount	40,516	36,393
Accumulated Amortization	(22,358)	(18,855)
Net Balance	18,158	17,538
Purchased contracts
Indefinite-lived Intangible Assets by Major Class [Line Items]
Gross Carrying Amount	10,772	10,753
Accumulated Amortization	(9,924)	(8,504)
Net Balance	848	2,249
Trademarks and tradenames
Indefinite-lived Intangible Assets by Major Class [Line Items]
Gross Carrying Amount	1,329	1,062
Accumulated Amortization	(560)	(422)
Net Balance	769	640
Covenant not to compete
Indefinite-lived Intangible Assets by Major Class [Line Items]
Gross Carrying Amount	80	83
Accumulated Amortization	(72)	(62)
Net Balance	$ 8	$ 21