Summary of Significant Accounting Policies - Schedule of Financial Instruments Recognized at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Short-term available-for-sale investments	$ 415	$ 1,361
Total current assets recorded at fair value	415	1,361
Restricted cash	3,732	3,668
Total non-current assets recorded at fair value	3,732	3,668
Fair Value, Inputs, Level 1 [Member]
Short-term available-for-sale investments	415	1,361
Total current assets recorded at fair value	415	1,361
Restricted cash	3,732	3,668
Total non-current assets recorded at fair value	3,732	3,668
Fair Value, Inputs, Level 2 [Member]
Short-term available-for-sale investments
Total current assets recorded at fair value
Restricted cash
Total non-current assets recorded at fair value
Fair Value, Inputs, Level 3 [Member]
Short-term available-for-sale investments
Total current assets recorded at fair value
Restricted cash
Total non-current assets recorded at fair value