Summary of Significant Accounting Policies - Schedule of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounting Policies [Abstract]
Cash and cash equivalents	$ 4,054	$ 3,309
Restricted cash - pledged deposits for performance bonds	3,668	3,964
Cash, cash equivalents and restricted cash shown in the statement of cash flows	$ 7,722	$ 7,273	$ 4,891