Gross Carrying Amount and Accumulated Amortization of Intangible Assets (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 26,900	$ 26,900
Accumulated Amortization	(12,329)	(9,246)
Net Carrying Amount	14,571	17,654
Non-compete Agreement
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	1,400	1,400
Accumulated Amortization	(1,400)	(1,050)
Net Carrying Amount		350
Customer Relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	25,500	25,500
Accumulated Amortization	(10,929)	(8,196)
Net Carrying Amount	$ 14,571	$ 17,304