Intangible Assets - Finite Lived Intangible Assets (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Finite-Lived Intangible Assets, Net [Abstract]
Total amortized intangible assets, Gross Value	$ 49,370,000	$ 34,370,000
Total amortized intangible assets, Accumulated Depreciation	(15,319,000)	(11,574,000)
Total amortized intangible assets, Net Value	34,051,000	22,796,000
Amortization expense	3,700,000	2,000,000	2,400,000
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
Future amortization expense, 2012	9,400,000
Future amortization expense, 2013	2,600,000
Future amortization expense, 2014	2,200,000
Future amortization expense, 2015	1,800,000
Future amortization expense, 2016	1,800,000
Future amortization expense, thereafter	16,300,000
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	(10,869,000)	(7,573,000)
Total amortized intangible assets, Net Value	18,844,000	22,140,000
Customer lists [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Total amortized intangible assets, Gross Value	4,698,000	2,198,000
Total amortized intangible assets, Accumulated Depreciation	(2,170,000)	(1,942,000)
Total amortized intangible assets, Net Value	2,528,000	256,000
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	(1,546,000)	(1,476,000)
Total amortized intangible assets, Net Value	42,000	112,000
Order or Production Backlog [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Total amortized intangible assets, Gross Value	8,400,000
Total amortized intangible assets, Accumulated Depreciation	0
Total amortized intangible assets, Net Value	8,400,000
Trade Names [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Total amortized intangible assets, Gross Value	4,100,000
Total amortized intangible assets, Accumulated Depreciation	0
Total amortized intangible assets, Net Value	4,100,000
Other [Member]
Finite-Lived Intangible Assets, Net [Abstract]
Total amortized intangible assets, Gross Value	871,000	871,000
Total amortized intangible assets, Accumulated Depreciation	(734,000)	(583,000)
Total amortized intangible assets, Net Value	$ 137,000	$ 288,000