Accrued Liabilities (Details) - USD ($)	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Payables and Accruals [Abstract]
Contract liabilities (Note 3)	$ 902,000		$ 1,234,000
Accrued remediation contingency (Note 14)	1,223,000		0
Other accrued liabilities	2,775,000		4,865,000
Total other accrued liabilities	$ 4,900,000	$ 6,077,000	$ 6,099,000