Carrying Amount and Accumulated Amortization of Other Intangible Assets (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 166,565	$ 52,419
Accumulated Amortization	(36,791)	(34,076)
Net Balance	129,774	18,343
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	149,388	40,298
Accumulated Amortization	(25,564)	(23,392)
Net Balance	123,824	16,906
Purchased contracts
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	10,920	10,750
Accumulated Amortization	(10,298)	(10,023)
Net Balance	622	727
Trade Marks and Trade Names
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	5,814	1,291
Accumulated Amortization	(831)	(585)
Net Balance	4,983	706
Covenant not to compete
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	443	80
Accumulated Amortization	(98)	(76)
Net Balance	$ 345	$ 4