Financial Instruments - Schedule of Fair Value on Recurring and Non-recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Short-term available-for-sale investments	$ 499	$ 1,361
Total current assets recorded at fair value	499	1,361
Restricted cash	3,668	3,668
Total non-current assets recorded at fair value	3,668	3,668
Fair Value, Inputs, Level 1 [Member]
Short-term available-for-sale investments	499	1,361
Total current assets recorded at fair value	499	1,361
Restricted cash	3,668	3,668
Total non-current assets recorded at fair value	3,668	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