DERIVATIVES AND HEDGING ACTIVITIES - Effect of derivative contracts on the consolidated statement of operations (Details) - Realized (Gains)/Losses Reclassified from Accumulated Other Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating income (expenses) | Derivatives designated as hedging instruments
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (loss) on derivatives	$ 2,072	$ (4,787)	$ 7,034
Operating income (expenses) | Derivatives not designated as hedging instruments
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (loss) on derivatives	0	0	0
Other income (expenses) | Derivatives designated as hedging instruments
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (loss) on derivatives	0	0	0
Other income (expenses) | Derivatives not designated as hedging instruments
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (loss) on derivatives	$ 2,331	$ (4,553)	$ 3,248