SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details) - USD ($) $ in Thousands, shares in Millions			3 Months Ended		9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Discount rate, present value of future revenue					10.00%
Amount exceeding full-cost ceiling	$ 189,100	$ 243,900		$ 189,100		$ 189,100
Full-cost ceiling impairment	251,200	324,000	$ 0	251,163	$ 0	575,164
Deferred income tax benefit	$ 62,100	$ 80,100	6,701	(26,497)	(1,488)	43,369
Capitalized general and administrative costs			9,900	7,600	28,600	23,900
Interest costs capitalized			$ 1,500	$ 2,000	$ 3,900	$ 5,200
Options
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Antidilutive securities (in shares)				2.5	1.3
Restricted Stock
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Antidilutive securities (in shares)				0.7		0.6