Accounting for the Impairment or Disposal of Long-Lived Assets - Impairment (Details) (USD $)	3 Months Ended
	Mar. 31, 2012 South Region [Member]	Mar. 31, 2011 Central Region [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment charges	$ 57,000	$ 550,000