Accrued Liabilities (Details) - USD ($)	Jun. 30, 2020	Dec. 31, 2019
Payables and Accruals [Abstract]
Contract liabilities (Note 3)	$ 1,168,000	$ 712,000
Accrued remediation contingency (Note 13)	0	146,000
Other accrued liabilities	936,000	1,118,000
Total other accrued liabilities	$ 2,104,000	$ 1,976,000