Intangible Assets - Finite Lived Intangible Assets (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Finite-Lived Intangible Assets, Net [Abstract]
Total amortized intangible assets, Gross Value	$ 34,370,000	$ 34,370,000
Total amortized intangible assets, Accumulated Depreciation	(11,574,000)	(9,572,000)
Total amortized intangible assets, Net Value	22,796,000	24,798,000
Amortization expense	2,000,000	2,400,000	3,000,000
Finite-Lived Intangible Assets, Future Amortization Expense, Current and Five Succeeding Fiscal Years [Abstract]
Future amortization expense, 2012	1,900,000
Future amortization expense, 2013	1,600,000
Future amortization expense, 2014	1,500,000
Future amortization expense, 2015	1,500,000
Future amortization expense, 2016	1,400,000
Future amortization expense, thereafter	14,900,000
Permits [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Total amortized intangible assets, Gross Value	29,713,000	29,713,000
Total amortized intangible assets, Accumulated Depreciation	(7,573,000)	(6,100,000)
Total amortized intangible assets, Net Value	22,140,000	23,613,000
Customer lists [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Total amortized intangible assets, Gross Value	2,198,000	2,198,000
Total amortized intangible assets, Accumulated Depreciation	(1,942,000)	(1,715,000)
Total amortized intangible assets, Net Value	256,000	483,000
Covenants not to compete [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Total amortized intangible assets, Gross Value	1,588,000	1,588,000
Total amortized intangible assets, Accumulated Depreciation	(1,476,000)	(1,325,000)
Total amortized intangible assets, Net Value	112,000	263,000
Other [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Total amortized intangible assets, Gross Value	871,000	871,000
Total amortized intangible assets, Accumulated Depreciation	(583,000)	(432,000)
Total amortized intangible assets, Net Value	$ 288,000	$ 439,000