Extraordinary Item - Additional Information (Detail) (USD $)	3 Months Ended	12 Months Ended
	Sep. 30, 2010	Dec. 31, 2012	Dec. 31, 2010
Extraordinary Item [Line Items]
Income from an extraordinary item net of tax	$ 1,300,000		$ 1,296,000
Receipt from Texas Department of Transportation for land and damages to our existing property		2,200,000
Net gain of before income taxes		$ 2,000,000