Construction Contracts (Summary of Costs in Excess of Billings and Billings in Excess of Costs) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($)
Change In Contract With Customer, Asset [Roll Forward]
Balance as of January 1, 2018	$ 245
Transferred to receivables	(245)
Construction contract costs and estimated earnings not billed during the period	352
Changes due to cumulative catch-up adjustment arising from changes in the estimate of the stage of completion	1,006
Balance as of December 31, 2018	1,358
Change In Contract With Customer, Liability [Roll Forward]
Balance as of January 1, 2018	3,591
Revenue recognized that was included in the balance at the beginning of the period	(3,591)
Increases due to new billings, excluding amounts recognized as revenue during the period	4,243
Changes due to cumulative catch-up adjustment arising from changes in the estimate of the stage of completion	(1,206)
Balance as of December 31, 2018	$ 3,037