Goodwill and Intangible Assets - Additional Information (Detail) (USD $)			1 Months Ended	3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	Oct. 31, 2010 Non-compete Agreement	Sep. 30, 2013 Non-compete Agreement	Sep. 30, 2012 Non-compete Agreement	Sep. 30, 2013 Non-compete Agreement	Sep. 30, 2012 Non-compete Agreement	Sep. 30, 2013 Customer Relationships	Sep. 30, 2012 Customer Relationships	Sep. 30, 2013 Customer Relationships	Sep. 30, 2012 Customer Relationships
Goodwill and Intangible Assets Disclosure [Line Items]
Accumulated impairment losses	$ 0	$ 0
Contract term			3 years
Amortization period (in years)						3 years				7 years
Amortization expense				$ 117,000	$ 117,000	$ 350,000	$ 350,000	$ 911,000	$ 911,000	$ 2,700,000	$ 2,700,000