FAIR VALUE MEASUREMENTS (Details) - Recurring basis $ in Thousands	Mar. 31, 2019 USD ($)
Carrying Amount
Assets:
Marketable equity securities	$ 19,465
Total assets	19,465
Liabilities:
Debt	444,156
Total liabilities	444,156
Amount of equity component of convertible notes	77,000
Fair Value
Assets:
Marketable equity securities	19,465
Total assets	19,465
Liabilities:
Debt	370,000
Total liabilities	370,000
Level 1
Assets:
Marketable equity securities	19,465
Total assets	19,465
Liabilities:
Debt	370,000
Total liabilities	$ 370,000