Carrying Amount and Accumulated Amortization of Other Intangible Assets (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 281,942	$ 174,459
Accumulated Amortization	(49,828)	(46,559)
Net Balance	232,114	127,900
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	261,971	157,364
Accumulated Amortization	(36,523)	(33,727)
Net Balance	225,448	123,637
Purchased contracts
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	10,722	10,823
Accumulated Amortization	(10,570)	(10,549)
Net Balance	152	274
Trademarks and tradenames
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	8,807	5,830
Accumulated Amortization	(2,518)	(2,096)
Net Balance	6,289	3,734
Covenant not to compete
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	442	442
Accumulated Amortization	(217)	(187)
Net Balance	$ 225	$ 255