Accrued Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Accrued payroll and related costs	$ 980	$ 1,088
Warranty reserve	209	142
Restructuring charges	185	185
Payable to joint venture partner (see Note 13 - Joint Venture)	438	0
Other accrued liabilities	444	463
Accrued liabilities	$ 2,256	$ 1,878