Costs and Estimated Earnings on Uncompleted Contracts (Summary of Costs and Estimated Earnings on Uncompleted Contracts) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Costs and Estimated Earnings on Uncompleted Contracts [Abstract]
Costs incurred on uncompleted contracts	$ 33,232	$ 31,404
Estimated earnings	11,836	10,541
Billings to date	(32,495)	(24,771)
Costs and estimated earnings on uncompleted contracts	$ 12,573	$ 17,174