CASH, CASH EQUIVALENTS AND SHORT AND LONG TERM INVESTMENTS - Schedule of Financial Assets Measured and Recognized at Fair Value on a Recurring Basis and Classified under the Appropriate Level of the Fair Value Hierarchy (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair value, assets and liabilities on a recurring and non-recurring basis
Long-term investments	$ 5,856	$ 7,753
Recurring
Fair value, assets and liabilities on a recurring and non-recurring basis
Short-term investments		479
Long-term investments		1,700
Level 3 \| Recurring
Fair value, assets and liabilities on a recurring and non-recurring basis
Short-term investments		479
Long-term investments		$ 1,700

CASH, CASH EQUIVALENTS AND SHORT AND LONG TERM INVESTMENTS - Schedule of Financial Assets Measured and Recognized at Fair Value on a Recurring Basis and Classified under the Appropriate Level of the Fair Value Hierarchy (Details) - USD ($)
$ in Thousands

Dec. 31, 2017

Dec. 31, 2016

Fair value, assets and liabilities on a recurring and non-recurring basis

Long-term investments

$ 5,856

$ 7,753

Recurring

Fair value, assets and liabilities on a recurring and non-recurring basis

Short-term investments

479

Long-term investments

1,700

Level 3 | Recurring

Fair value, assets and liabilities on a recurring and non-recurring basis

Short-term investments

479

Long-term investments

$ 1,700