SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details) - USD ($) $ in Thousands, shares in Millions		3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 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	$ 243,900		$ 243,900		$ 243,900
Full-cost ceiling impairment		$ 0	324,001	$ 0	324,001
Deferred income tax benefit	$ 80,100	(5,349)	109,823	(8,189)	69,866
Capitalized general and administrative costs		9,200	8,100	18,700	16,300
Interest costs capitalized		$ 1,900	$ 1,800	$ 2,500	$ 3,200
Options
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Antidilutive securities (in shares)		0.5	2.5	1.5	2.6
Restricted Stock
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Antidilutive securities (in shares)			0.5		0.6