FINANCIAL INSTRUMENTS - Schedule of Fair Value on Recurring and Non-recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Short-term available-for-sale investments		$ 415
Total current assets recorded at fair value		415
Restricted cash	$ 3,784	3,732
Total non-current assets recorded at fair value	3,784	3,732
Fair Value, Inputs, Level 1
Short-term available-for-sale investments		415
Total current assets recorded at fair value		415
Restricted cash	3,784	3,732
Total non-current assets recorded at fair value	$ 3,784	$ 3,732