FAIR VALUE MEASUREMENT - Assets and Liabilities (Details) - Fair Value, Recurring - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Liabilities measured at fair value
Liabilities measured at fair value	$ (8,099)	$ (8,063)
Net fair value	80,903	(5,970)
Derivative commodity contracts
Assets measured at fair value
Derivative assets	89,002	2,093
Liabilities measured at fair value
Liabilities measured at fair value	(34)	(2,300)
Derivative interest rate swaps
Liabilities measured at fair value
Liabilities measured at fair value	(8,065)	(5,763)
Level 2
Liabilities measured at fair value
Liabilities measured at fair value	(8,099)	(8,063)
Net fair value	80,903	(5,970)
Level 2 | Derivative commodity contracts
Assets measured at fair value
Derivative assets	89,002	2,093
Liabilities measured at fair value
Liabilities measured at fair value	(34)	(2,300)
Level 2 | Derivative interest rate swaps
Liabilities measured at fair value
Liabilities measured at fair value	$ (8,065)	$ (5,763)