Investment (Summary Financial Information Under Equity Method) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Amboy Aggregates [Member]
Schedule Of Equity Method Investments [Line Items]
Equity Method Investment, Summarized Financial Information, Revenue			$ 139
Equity Method Investment, Summarized Financial Information, Gross Profit (Loss)		$ 758	(1,363)
Equity Method Investment, Summarized Financial Information, Income (Loss) from Continuing Operations before Extraordinary Items	$ 34	758	(3,152)
Equity Method Investment, Summarized Financial Information, Net Income (Loss)	$ 34	758	(3,152)
TerraSea Environmental Solutions [Member]
Schedule Of Equity Method Investments [Line Items]
Equity Method Investment, Summarized Financial Information, Revenue			6,960
Equity Method Investment, Summarized Financial Information, Gross Profit (Loss)		(183)	(3,800)
Equity Method Investment, Summarized Financial Information, Net Income (Loss)		$ (183)	$ (3,800)