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Supplemental Information on Oil and Gas Exploration and Production Activities (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2020

Extractive Industries [Abstract]

Schedule of capitalized costs related to oil and gas producing activities

Capitalized Costs Related to Oil and Gas Producing Activities

			2020						2019
			(In thousands)
Proved properties			$	9,359,866					$	8,909,069
Unproved properties			1,457,043						1,686,666
			10,816,909						10,595,735
Accumulated depreciation, depletion, amortization and impairment			(8,778,759)						(7,191,957)
Net capitalized costs			$	2,038,150					$	3,403,778

Schedule of cost incurred in oil and gas property acquisition and development activities

Costs Incurred in Oil and Gas Property Acquisition and Development Activities

			2020						2019						2018
			(In thousands)
Acquisition			$	15,260					$	37,598					$	119,444
Development			276,622						594,673						714,269
Exploratory			—						9,762						22,081
Total			$	291,882					$	642,033					$	855,794

Schedule of results of operations for oil and gas production activities

The results of operations exclude general office overhead and interest expense attributable to oil and gas production.

			2020						2019						2018
			(In thousands)
Revenues			$	801,251					$	1,354,766					$	1,675,180
Production costs			(537,609)						(620,412)						(611,965)
Depletion			(229,702)						(539,379)						(476,517)
Impairment			(1,357,099)						(2,039,770)						—
Income tax (expense) benefit			(7,290)						7,563						68
Results of operations from producing activities			$	(1,330,449)					$	(1,837,232)					$	586,766
Depletion per Mcf of gas equivalent (Mcfe)			$	0.61					$	1.08					$	0.96

Schedule of oil and gas reserves

These estimates are reviewed annually and revised, either upward or downward, as warranted by additional performance data.

			Oil (MMBbl)						Natural Gas (Bcf)						NGL (MMBbl)						Natural Gas Equivalent (Bcfe)
Proved Reserves
December 31, 2017			19						4,825						76						5,395
Purchases of reserves			—						—						—						—
Extensions and discoveries			5						622						10						711
Sales of reserves			—						(43)						—						(45)
Revisions of prior reserve estimates			—						(827)						1						(821)
Current production			(3)						(444)						(6)						(497)
December 31, 2018			21						4,134						81						4,743
Purchases of reserves			—						—						—						—
Extensions and discoveries			4						997						13						1,097
Sales of reserves			(2)						(63)						—						(77)
Revisions of prior reserve estimates			(2)						(562)						(27)						(734)
Current production			(2)						(458)						(5)						(502)
December 31, 2019			18						4,048						62						4,528
Purchases of reserves			—						—						—						—
Extensions and discoveries			1						216						3						240
Sales of reserves			—						(74)						—						(75)
Revisions of prior reserve estimates			(4)						(1,564)						(23)						(1,725)
Current production			(2)						(345)						(4)						(380)
December 31, 2020			13						2,281						38						2,588
Proved developed reserves
December 31, 2018			10						1,813						41						2,115
December 31, 2019			8						1,757						30						1,984
December 31, 2020			7						1,358						22						1,527
Proved undeveloped reserves
December 31, 2018			11						2,321						40						2,628
December 31, 2019			10						2,291						32						2,544
December 31, 2020			7						923						16						1,061
Totals may not sum or recalculate due to rounding.

Schedule of standardized measure of discounted future net cash flows relating to proved oil and gas reserves

Standardized Measure of Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves  

			Year ended December 31,
			2020						2019						2018
			(In millions)
Future cash flows			$	4,079					$	10,451					$	14,483
Future development and abandonment costs			(652)						(2,058)						(2,438)
Future production costs			(2,325)						(4,513)						(5,068)
Future production taxes			(137)						(333)						(456)
Future income taxes			—						—						(943)
Future net cash flows			965						3,547						5,578
10% discount to reflect timing of cash flows			(425)						(1,844)						(2,596)
Standardized measure of discounted future net cash flows			$	540					$	1,703					$	2,982

Schedule of changes in standardized measure of discounted future net cash flows relating to proved oil and gas reserves

Changes in Standardized Measure of Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves

			Year ended December 31,
			2020						2019						2018
			(In millions)
Sales and transfers of oil and gas produced, net of production costs			$	(264)					$	(734)					$	(1,063)
Net changes in prices, production costs, and development costs			(954)						(1,372)						591
Acquisition of oil and gas reserves in place			—						—						—
Extensions and discoveries			38						388						519
Previously estimated development costs incurred during the period			215						406						402
Revisions of previous quantity estimates, less related production costs			(255)						(321)						(357)
Sales of oil and gas reserves in place			(6)						(49)						(26)
Accretion of discount			170						298						264
Net changes in income taxes			—						425						(185)
Change in production rates and other			(109)						(319)						194
Total change in standardized measure of discounted future net cash flows			$	(1,165)					$	(1,278)					$	339

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Tabular disclosure of the net quantities of an enterprise's interests in proved developed and undeveloped reserves of (a) crude oil (including condensate and natural gas liquids), (b) natural gas (including coal bed methane), (c) synthetic oil, (d) synthetic gas, and (e) other nonrenewable natural resources that are intended to be upgraded during the period as of the beginning of the period, changes in quantities during the period, and as of the end of the period.

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Tabular disclosure of the future net cash flows relating to proved oil and gas reserves and oil and gas subject to purchase under long-term agreements in which the enterprise participates in the operation of the properties on which the oil and gas is located or otherwise serves as the producer. This information is presented in aggregate and for each geographic area for which reserve quantities are disclosed.

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