(Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Loss Contingencies [Line Items]
Expected insurance proceeds	$ 973,000
Accrued remediation contingency (Note 14)	1,223,000		$ 0
Insurance deductible	250,000
Accounts receivable	17,787,000		$ 18,399,000
Change in warranty liability balance	0	$ 0
Warranty liability balance	159,000	$ 159,000
Customer One
Loss Contingencies [Line Items]
Accounts receivable	$ 500,000