Costs and Estimated Earnings on Uncompleted Contracts (Summary of Costs and Estimated Earnings on Uncompleted Contracts) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Costs and Estimated Earnings on Uncompleted Contracts [Abstract]
Costs incurred on uncompleted contracts	$ 44,842	$ 38,464
Estimated earnings	18,678	16,655
Billings to date	(42,058)	(31,952)
Costs and estimated earnings on uncompleted contracts	$ 21,462	$ 23,167