DERIVATIVE INSTRUMENTS AND PRICE RISK MANAGEMENT - Reconciliation between the gross assets and liabilities and the amounts reflected on the balance sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets (Liabilities), Offsetting of Derivative Assets	$ 36,233	$ 178,477
Gross Amounts Offset in the Balance Sheet, Offsetting of Derivative Assets	(22,051)	(764)
Net Amounts of Assets Presented in the Balance Sheet, Offsetting of Derivative Assets	14,182	177,713
Gross Amounts of Recognized Assets (Liabilities), Offsetting of Derivative Liabilities	(41,428)	(764)
Gross Amounts Offset in the Balance Sheet, Offsetting of Derivative Liabilities	22,051	764
Net Amount of Assets (Liabilities) Presented in Balance Sheet, Offsetting of Derivative Liabilities	(19,377)	0
Current Assets
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets (Liabilities), Offsetting of Derivative Assets	20,164	116,620
Gross Amounts Offset in the Balance Sheet, Offsetting of Derivative Assets	(14,536)	(750)
Net Amounts of Assets Presented in the Balance Sheet, Offsetting of Derivative Assets	5,628	115,870
Noncurrent Assets
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets (Liabilities), Offsetting of Derivative Assets	16,069	61,857
Gross Amounts Offset in the Balance Sheet, Offsetting of Derivative Assets	(7,515)	(15)
Net Amounts of Assets Presented in the Balance Sheet, Offsetting of Derivative Assets	8,554	61,843
Current Liabilities
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets (Liabilities), Offsetting of Derivative Liabilities	(25,834)	(750)
Gross Amounts Offset in the Balance Sheet, Offsetting of Derivative Liabilities	14,536	750
Net Amount of Assets (Liabilities) Presented in Balance Sheet, Offsetting of Derivative Liabilities	(11,298)	0
Noncurrent Liabilities
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets (Liabilities), Offsetting of Derivative Liabilities	(15,594)	(15)
Gross Amounts Offset in the Balance Sheet, Offsetting of Derivative Liabilities	7,515	15
Net Amount of Assets (Liabilities) Presented in Balance Sheet, Offsetting of Derivative Liabilities	$ (8,079)	$ 0