Intangible Assets - Finite Lived Intangible Assets (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2010
Finite-Lived Intangible Assets [Line Items]
Total amortized intangible assets, Gross Value	$ 34,370,000	$ 38,450,000	$ 34,370,000	$ 38,450,000	$ 34,370,000
Total amortized intangible assets, Accumulated Amortization	(11,074,000)	(9,951,000)	(11,074,000)	(9,951,000)	(9,572,000)
Total amortized intangible assets, Net Value	23,296,000	28,499,000	23,296,000	28,499,000	24,798,000
Amortization expense	500,000	600,000	1,500,000	1,800,000
Future amortization expense, Remainder of Fiscal Year			500,000
Future amortization expense, Year One			1,900,000
Future amortization expense, Year Two			1,600,000
Future amortization expense, Year Three			1,500,000
Future amortization expense, Year Four			1,500,000
Future amortization expense, after Year Four			16,300,000
Permits [Member]
Finite-Lived Intangible Assets [Line Items]
Total amortized intangible assets, Gross Value	29,713,000	33,582,000	29,713,000	33,582,000	29,713,000
Total amortized intangible assets, Accumulated Amortization	(7,205,000)	(6,401,000)	(7,205,000)	(6,401,000)	(6,100,000)
Total amortized intangible assets, Net Value	22,508,000	27,181,000	22,508,000	27,181,000	23,613,000
Customer Lists [Member]
Finite-Lived Intangible Assets [Line Items]
Total amortized intangible assets, Gross Value	2,198,000	2,198,000	2,198,000	2,198,000	2,198,000
Total amortized intangible assets, Accumulated Amortization	(1,885,000)	(1,658,000)	(1,885,000)	(1,658,000)	(1,715,000)
Total amortized intangible assets, Net Value	313,000	540,000	313,000	540,000	483,000
Covenants not to compete [Member]
Finite-Lived Intangible Assets [Line Items]
Total amortized intangible assets, Gross Value	1,588,000	1,588,000	1,588,000	1,588,000	1,588,000
Total amortized intangible assets, Accumulated Amortization	(1,439,000)	(1,286,000)	(1,439,000)	(1,286,000)	(1,325,000)
Total amortized intangible assets, Net Value	149,000	302,000	149,000	302,000	263,000
Other [Member]
Finite-Lived Intangible Assets [Line Items]
Total amortized intangible assets, Gross Value	871,000	1,082,000	871,000	1,082,000	871,000
Total amortized intangible assets, Accumulated Amortization	(545,000)	(606,000)	(545,000)	(606,000)	(432,000)
Total amortized intangible assets, Net Value	$ 326,000	$ 476,000	$ 326,000	$ 476,000	$ 439,000