Costs and Estimated Earnings on Uncompleted Contracts (Costs and Estimated Earnings on Uncompleted Contracts Accompanying Consolidated Balance Sheets) (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Costs and Estimated Earnings on Uncompleted Contracts [Abstract]
Costs and estimated earnings in excess of billings on uncompleted contracts	$ 40,860	$ 34,796
Billings in excess of costs and estimated earnings on uncompleted contracts (included in Other current liabilities)	(2,977)	(1,794)
Costs and estimated earnings on uncompleted contracts	$ 37,883	$ 33,002