Carrying Amount and Accumulated Amortization of Other Intangible Assets (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 52,419	$ 48,291
Accumulated Amortization	(34,076)	(27,843)
Net Balance	18,343	20,448
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	40,298	36,393
Accumulated Amortization	(23,392)	(18,855)
Net Balance	16,906	17,538
Purchased contracts
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	10,750	10,753
Accumulated Amortization	(10,023)	(8,504)
Net Balance	727	2,249
Trademarks and tradenames
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	1,291	1,062
Accumulated Amortization	(585)	(422)
Net Balance	706	640
Covenant not to compete
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	80	83
Accumulated Amortization	(76)	(62)
Net Balance	$ 4	$ 21