Construction Contracts (Summary of Costs in Excess of Billings and Billings in Excess of Costs) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Change In Contract With Customer, Asset [Roll Forward]
Beginning balance	$ 249	$ 1,358
Transferred to receivables	(545)	(2,557)
Construction contract costs and estimated earnings not billed during the period	138	249
Changes due to cumulative catch-up adjustment arising from changes in the estimate of the stage of completion	296	1,199
Ending balance	138	249
Change In Contract With Customer, Liability [Roll Forward]
Beginning balance	5,306	3,037
Revenue recognized that was included in the balance at the beginning of the period	(5,306)	(3,037)
Increases due to new billings, excluding amounts recognized as revenue during the period	6,244	6,283
Changes due to cumulative catch-up adjustment arising from changes in the estimate of the stage of completion	(156)	(977)
Ending balance	$ 6,088	$ 5,306