Costs and Estimated Earnings on Uncompleted Contracts (Costs and Estimated Earnings on Uncompleted Contracts Accompanying Consolidated Balance Sheets) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Costs and Estimated Earnings on Uncompleted Contracts [Abstract]
Costs and estimated earnings in excess of billings on uncompleted contracts	$ 13,039	$ 17,437
Billings in excess of costs and estimated earnings on uncompleted contracts (included in Other current liabilities)	(466)	(263)
Costs and estimated earnings on uncompleted contracts	$ 12,573	$ 17,174