Business Acquisition - Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Aug. 05, 2015	Dec. 31, 2014	Dec. 31, 2013
Business Acquisition [Line Items]
Goodwill	$ 70,518		$ 33,798	$ 33,798
TAS Commercial Concrete
Business Acquisition [Line Items]
Accounts receivable		$ 54,344
Costs and estimated earnings in excess of billings on uncompleted contracts		4,372
Prepaid expenses and other current assets		828
Fixed assets, net		14,000
Investment in GLM Concrete Services, LLC		76
Goodwill		36,720
Other intangible assets		33,110
Accounts payable		(18,458)
Accrued expenses and other current liabilities		(13,015)
Total Acquisition Consideration		$ 111,977