FAIR VALUE MEASUREMENTS (Details) - Recurring basis $ in Thousands	Dec. 31, 2017 USD ($)
Carrying Amount
Assets:
Marketable equity securities	$ 3,450
Liabilities:
Debt	427,890
Amount of equity component of convertible notes	77,000
Fair Value
Assets:
Marketable equity securities	3,450
Total assets	3,450
Liabilities:
Debt	401,309
Total liabilities	401,309
Level 1
Assets:
Marketable equity securities	3,450
Total assets	3,450
Liabilities:
Debt	401,309
Total liabilities	$ 401,309