Gross Carrying Amount and Accumulated Amortization of Intangible Assets (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 26,900	$ 26,900
Accumulated Amortization	(11,301)	(9,246)
Net Carrying Amount	15,599	17,654
Non-compete Agreement
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	1,400	1,400
Accumulated Amortization	(1,283)	(1,050)
Net Carrying Amount	117	350
Customer Relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	25,500	25,500
Accumulated Amortization	(10,018)	(8,196)
Net Carrying Amount	$ 15,482	$ 17,304