Intangible Assets (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Acquired Finite-Lived Intangible Assets [Line Items]
Net carrying amount	$ 230,568	$ 44,067
Customer Relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible Assets	229,300	38,300
Accumulated amortization	(18,839)	(8,600)
Net carrying amount	210,461	29,700
Customer Contracts
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible Assets	28,683	19,743
Accumulated amortization	(8,576)	(5,376)
Net carrying amount	$ 20,107	$ 14,367