Intangible Assets - Finite Lived Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Finite-Lived Intangible Assets [Line Items]
Total amortized intangible assets, Gross Value	$ 48,570	$ 48,570	$ 48,570	$ 48,570	$ 48,570
Total amortized intangible assets, Accumulated Amortization	(28,091)	(25,953)	(28,091)	(25,953)	(26,454)
Total amortized intangible assets, Net Value	20,479	22,617	20,479	22,617	22,116
Amortization expense	500	600	1,600	1,800
Future amortization expense, Remainder of Fiscal Year	500		500
Future amortization expense, Year One	2,000		2,000
Future amortization expense, Year Two	1,800		1,800
Future amortization expense, Year Three	1,700		1,700
Future amortization expense, Year Four	1,700		1,700
Future amortization expense, after Year Four	12,700		12,700
Permits [Member]
Finite-Lived Intangible Assets [Line Items]
Total amortized intangible assets, Gross Value	29,713	29,713	29,713	29,713	29,713
Total amortized intangible assets, Accumulated Amortization	(13,958)	(12,835)	(13,958)	(12,835)	(13,115)
Total amortized intangible assets, Net Value	15,755	16,878	15,755	16,878	16,598
Order or Production Backlog [Member]
Finite-Lived Intangible Assets [Line Items]
Total amortized intangible assets, Gross Value	7,900	7,900	7,900	7,900	7,900
Total amortized intangible assets, Accumulated Amortization	(7,513)	(7,226)	(7,513)	(7,226)	(7,263)
Total amortized intangible assets, Net Value	387	674	387	674	637
Customer Lists [Member]
Finite-Lived Intangible Assets [Line Items]
Total amortized intangible assets, Gross Value	4,398	4,398	4,398	4,398	4,398
Total amortized intangible assets, Accumulated Amortization	(3,004)	(2,711)	(3,004)	(2,711)	(2,785)
Total amortized intangible assets, Net Value	1,394	1,687	1,394	1,687	1,613
Trade Names [Member]
Finite-Lived Intangible Assets [Line Items]
Total amortized intangible assets, Gross Value	4,100	4,100	4,100	4,100	4,100
Total amortized intangible assets, Accumulated Amortization	(1,187)	(755)	(1,187)	(755)	(863)
Total amortized intangible assets, Net Value	2,913	3,345	2,913	3,345	3,237
Covenants not to compete [Member]
Finite-Lived Intangible Assets [Line Items]
Total amortized intangible assets, Gross Value	2,459	2,459	2,459	2,459	2,459
Total amortized intangible assets, Accumulated Amortization	(2,429)	(2,426)	(2,429)	(2,426)	(2,428)
Total amortized intangible assets, Net Value	$ 30	$ 33	$ 30	$ 33	$ 31