FAIR VALUE MEASUREMENT - Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - Recurring - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Assets measured at fair value:
Total assets measured at fair value	$ 16,819	$ 8,813
Money market funds
Assets measured at fair value:
Cash and cash equivalents	15,011	7,007
Restricted cash	1,808	1,806
Fair value measurements at reporting date, level 1
Assets measured at fair value:
Total assets measured at fair value	16,819	8,813
Fair value measurements at reporting date, level 1 | Money market funds
Assets measured at fair value:
Cash and cash equivalents	15,011	7,007
Restricted cash	$ 1,808	$ 1,806