FAIR VALUE MEASUREMENTS (Details) - Recurring basis $ in Thousands	Dec. 31, 2018 USD ($)
Carrying Amount
Assets:
Marketable equity securities	$ 17,681
Total assets	17,681
Liabilities:
Debt	440,795
Total liabilities	440,795
Amount of equity component of convertible notes	77,000
Fair Value
Assets:
Marketable equity securities	17,681
Total assets	17,681
Liabilities:
Debt	371,388
Total liabilities	371,388
Level 1
Assets:
Marketable equity securities	17,681
Total assets	17,681
Liabilities:
Debt	371,388
Total liabilities	$ 371,388