Accrued Liabilities (Details) - USD ($)	Jun. 30, 2019	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Payables and Accruals [Abstract]
Contract liabilities (Note 3)	$ 1,147,000			$ 1,234,000
Accrued remediation contingency (Note 14)	2,228,000	$ 1,223,000		0
Other accrued liabilities	1,907,000			4,865,000
Total other accrued liabilities	$ 5,282,000		$ 6,077,000	$ 6,099,000