Basis of Presentation - Schedule of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Cash and cash equivalents	$ 2,715	$ 4,054	$ 7,152
Restricted cash - pledged deposits for performance bonds	3,668		3,941
Cash, cash equivalents and restricted cash shown in the statement of cash flows	$ 6,383	$ 7,722	$ 11,093	$ 7,273