FAIR VALUE MEASUREMENTS (Details) - Recurring basis $ in Thousands	Sep. 30, 2018 USD ($)
Carrying Amount
Assets:
Marketable equity securities	$ 17,771
Total assets	17,771
Liabilities:
Debt	437,488
Total liabilities	437,488
Amount of equity component of convertible notes	77,000
Fair Value
Assets:
Marketable equity securities	17,771
Total assets	17,771
Liabilities:
Debt	373,393
Total liabilities	373,393
Level 1
Assets:
Marketable equity securities	17,771
Total assets	17,771
Liabilities:
Debt	373,393
Total liabilities	$ 373,393