SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - FAIR VALUE MEASUREMENTS (Details) - Recurring $ in Thousands	Sep. 30, 2018 USD ($)
Levels of fair value measurements of financial assets:
Restricted cash	$ 1,000
Fair Value, Inputs, Level 1
Levels of fair value measurements of financial assets:
Restricted cash	1,000
Fair Value, Inputs, Level 2
Levels of fair value measurements of financial assets:
Restricted cash	0
Fair Value, Inputs, Level 3
Levels of fair value measurements of financial assets:
Restricted cash	$ 0