Prepaid Expenses and Other Current Assets (Details) $ in Thousands	Mar. 31, 2018 USD ($) Project	Dec. 31, 2017 USD ($)
Prepaid Expenses and Other Current Assets [Abstract]
Inventory	$ 733	$ 755
Income tax receivable	363	418
Prepaid expenses	628	549
Other current assets	956	1,073
Total prepaid expenses and other current assets	$ 2,680	$ 2,795
Number of projects | Project	3