SUPPLEMENTAL OIL AND GAS INFORMATION (UNAUDITED) - Future Net Cash Flows of Proved Reserves (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Extractive Industries [Abstract]
Future Cash Inflows	$ 7,059,586	$ 7,524,587	$ 3,143,604
Future Production Costs	(2,868,762)	(2,605,279)	(1,265,525)
Future Development Costs	(855,041)	(784,615)	(409,360)
Future Income Tax Expense	(320,528)	(611,989)	(27,476)
Future Net Cash Inflows	3,015,255	3,522,704	1,441,243
10% Annual Discount for Estimated Timing of Cash Flows	(1,337,194)	(1,643,061)	(687,257)
Standardized Measure of Discounted Future Net Cash Flows	$ 1,678,061	$ 1,879,643	$ 753,986	$ 379,026