Basis of Presentation, Liquidity and Summary of Significant Accounting Policie - Schedule of Reconciliation of Cash, Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Cash and cash equivalents	$ 8,210	$ 23,587	$ 27,207	$ 36,838
Restricted cash included in prepaid expenses and other current assets		346	346
Restricted cash included in deposits and other long-term assets	586	466	78	847
Total cash, cash equivalents, and restricted cash as shown in the condensed consolidated statements of cash flows	$ 8,796	$ 24,399	$ 27,631	$ 37,685