Southwestern Energy (SWN) 10-Q 29 Apr 21 2021 Q1 Quarterly report Financial data

COVER PAGE

COVER PAGE - shares	3 Months Ended
	Mar. 31, 2021	Apr. 27, 2021
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2021
Document Transition Report	false
Entity File Number	001-08246
Entity Registrant Name	Southwestern Energy Company
Amendment Flag	false
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q1
Entity Central Index Key	0000007332
Current Fiscal Year End Date	--12-31
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	71-0205415
Entity Address, Address Line One	10000 Energy Drive
Entity Address, City or Town	Spring
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	77389
City Area Code	832
Local Phone Number	796-1000
Title of 12(b) Security	Common Stock, Par Value $0.01
Trading Symbol	SWN
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		676,850,759

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating Revenues:
Total operating revenues	$ 1,072	$ 592
Operating Costs and Expenses:
Operating expenses	250	193
General and administrative expenses	38	26
Montage merger-related expenses	1	0
Restructuring charges	6	10
Depreciation, depletion and amortization	96	113
Impairments	0	1,479
Taxes, other than income taxes	24	13
Total operating costs and expense	771	2,082
Operating Income (Loss)	301	(1,490)
Interest Expense:
Interest on debt	50	40
Other interest charges	3	2
Interest capitalized	(22)	(23)
Total interest expense	31	19
Gain (Loss) on Derivatives	(191)	339
Gain on Early Extinguishment of Debt	0	28
Other Income, Net	1	1
Income (Loss) Before Income Taxes	80	(1,141)
Provision (Benefit) for Income Taxes:
Current	0	(2)
Deferred	0	408
Total provision (benefit) from income taxes	0	406
Net Income (Loss)	$ 80	$ (1,547)
Earnings (Loss) Per Common Share:
Basic (in dollars per share)	$ 0.12	$ (2.86)
Diluted (in dollars per share)	$ 0.12	$ (2.86)
Weighted Average Common Shares Outstanding:
Basic (in shares)	675,385,145	540,308,491
Diluted (in shares)	679,867,825	540,308,491
Gas sales
Operating Revenues:
Total operating revenues	$ 464	$ 248
Oil sales
Operating Revenues:
Total operating revenues	81	52
NGL sales
Operating Revenues:
Total operating revenues	173	50
Marketing
Operating Revenues:
Total operating revenues	352	239
Other
Operating Revenues:
Total operating revenues	2	3
Marketing purchases
Operating Costs and Expenses:
Marketing purchases	$ 356	$ 248

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2021	Mar. 31, 2020
Statement of Comprehensive Income [Abstract]
Net income (loss)		$ 80	$ (1,547)
Change in value of pension and other postretirement liabilities:
Amortization of prior service cost and net loss included in net periodic pension cost	[1]	0	0
Comprehensive income (loss)		$ 80	$ (1,547)
[1]	The amortization of prior service costs and net loss along with corresponding tax benefits for the three months ended March 31, 2021 and March 31, 2020 were immaterial.

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 4	$ 13
Accounts receivable, net	400	368
Derivative assets	157	241
Other current assets	41	49
Total current assets	602	671
Natural gas and oil properties, using the full cost method, including $1,488 million as of March 31, 2021 and $1,472 million as of December 31, 2020 excluded from amortization	27,532	27,261
Other	493	523
Less: Accumulated depreciation, depletion and amortization	(23,741)	(23,673)
Total property and equipment, net	4,284	4,111
Operating lease assets	155	163
Deferred tax assets	0	0
Other long-term assets	206	215
Total long-term assets	361	378
TOTAL ASSETS	5,247	5,160
Current liabilities:
Current portion of long-term debt	207	0
Accounts payable	639	573
Taxes payable	67	74
Interest payable	55	58
Derivative liabilities	338	245
Current operating lease liabilities	41	42
Other current liabilities	23	20
Total current liabilities	1,370	1,012
Long-term debt	2,812	3,150
Long-term operating lease liabilities	111	117
Long-term derivative liabilities	168	183
Pension and other postretirement liabilities	40	45
Other long-term liabilities	160	156
Total long-term liabilities	3,291	3,651
Commitments and contingencies (Note 12)
Equity:
Common stock, $0.01 par value; 1,250,000,000 shares authorized; issued 721,195,122 shares as of March 31, 2021 and 718,795,700 shares as of December 31, 2020	7	7
Additional paid-in capital	5,102	5,093
Accumulated deficit	(4,283)	(4,363)
Accumulated other comprehensive loss	(38)	(38)
Common stock in treasury, 44,353,224 shares as of March 31, 2021 and December 31, 2020	(202)	(202)
Total equity	586	497
TOTAL LIABILITIES AND EQUITY	$ 5,247	$ 5,160

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Natural gas and oil properties, using the full cost method, costs excluded from amortization	$ 1,488	$ 1,472
Common stock, par value (in dollars per shares)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	1,250,000,000	1,250,000,000
Common stock, shares issued (in shares)	721,195,122	718,795,700
Treasury stock, shares (in shares)	44,353,224	44,353,224

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Cash Flows From Operating Activities:
Net income (loss)	$ 80	$ (1,547)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation, depletion and amortization	96	113
Amortization of debt issuance costs	2	1
Impairments	0	1,479
Deferred income taxes	0	408
(Gain) loss on derivatives, unsettled	169	(246)
Stock-based compensation	0	1
Gain on early extinguishment of debt	0	(28)
Change in assets and liabilities:
Accounts receivable	(33)	53
Accounts payable	33	(86)
Taxes payable	(8)	(6)
Interest payable	(2)	1
Inventories	9	8
Other assets and liabilities	1	9
Net cash provided by operating activities	347	160
Cash Flows From Investing Activities:
Capital investments	(227)	(228)
Proceeds from sale of property and equipment	1	0
Other	(1)	0
Net cash used in investing activities	(227)	(228)
Cash Flows From Financing Activities:
Payments on long-term debt	0	(52)
Payments on revolving credit facility	(923)	(500)
Borrowings under revolving credit facility	790	615
Change in bank drafts outstanding	7	5
Cash paid for tax withholding	(3)	0
Net cash provided by (used in) financing activities	(129)	68
Decrease in cash and cash equivalents	(9)	0
Cash and cash equivalents at beginning of year	13	5
Cash and cash equivalents at end of period	$ 4	$ 5

CONSOLIDATED STATEMENTS OF CHAN

CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) $ in Millions	Total	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Income (Loss)	Common Stock in Treasury
Balance (in shares) at Dec. 31, 2019		585,555,923				44,353,224
Balance beginning at Dec. 31, 2019	$ 3,246	$ 6	$ 4,726	$ (1,251)	$ (33)	$ (202)
Comprehensive income:
Net (loss) income	(1,547)			(1,547)
Comprehensive income (loss)	(1,547)
Stock-based compensation	1		1
Issuance of restricted stock (in shares)		12,397
Cancellation of restricted stock (in shares)		(167,130)
Restricted units granted (in shares)		1,005,976
Restricted units granted	1		1
Tax withholding - stock compensation (in shares)		(383,731)
Balance (in shares) at Mar. 31, 2020		586,023,435				44,353,224
Balance ending at Mar. 31, 2020	1,701	$ 6	4,728	(2,798)	(33)	$ (202)
Balance (in shares) at Dec. 31, 2020		718,795,700				44,353,224
Balance beginning at Dec. 31, 2020	497	$ 7	5,093	(4,363)	(38)	$ (202)
Comprehensive income:
Net (loss) income	80			80
Comprehensive income (loss)	80
Issuance of restricted stock (in shares)		10,067
Cancellation of restricted stock (in shares)		(405)
Restricted units granted (in shares)		2,136,882
Restricted units granted	8		8
Performance units vested (in shares)		1,001,505
Performance units vested	4		4
Tax withholding - stock compensation (in shares)		(748,627)
Tax withholding – stock compensation	(3)		(3)
Balance (in shares) at Mar. 31, 2021		721,195,122				44,353,224
Balance ending at Mar. 31, 2021	$ 586	$ 7	$ 5,102	$ (4,283)	$ (38)	$ (202)

BASIS OF PRESENTATION

BASIS OF PRESENTATION	3 Months Ended
	Mar. 31, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
BASIS OF PRESENTATION	BASIS OF PRESENTATION Southwestern Energy Company (including its subsidiaries, collectively “Southwestern” or the “Company”) is an independent energy company engaged in natural gas, oil and NGL exploration, development and production (“E&P”). The Company is also focused on creating and capturing additional value through its marketing business (“Marketing”), which was previously referred to as “Midstream” when it included the operation of gathering systems. Southwestern conducts most of its business through subsidiaries and operates principally in two segments: E&P and Marketing. E&P. Southwestern’s primary business is the exploration for and production of natural gas, oil and NGLs, with ongoing operations focused on the development of unconventional natural gas and oil reservoirs located in Pennsylvania, West Virginia and Ohio. The Company’s operations in northeast Pennsylvania, herein referred to as “Northeast Appalachia,” are primarily focused on the unconventional natural gas reservoir known as the Marcellus Shale. Operations in West Virginia, Ohio and southwest Pennsylvania, herein referred to as “Southwest Appalachia,” are focused on the Marcellus Shale, the Utica and the Upper Devonian unconventional natural gas and oil reservoirs. Collectively, Southwestern refers to its properties located in Pennsylvania, Ohio and West Virginia as “Appalachia.” The Company also operates drilling rigs located in Appalachia, and provides certain oilfield products and services, principally serving the Company’s E&P activities through vertical integration. Marketing. Southwestern’s marketing activities capture opportunities that arise through the marketing and transportation of natural gas, oil and NGLs primarily produced in its E&P operations. The accompanying consolidated financial statements were prepared using accounting principles generally accepted in the United States of America (“GAAP”) for interim financial information and in accordance with the rules and regulations of the Securities and Exchange Commission. Certain information relating to the Company’s organization and footnote disclosures normally included in financial statements prepared in accordance with GAAP have been appropriately condensed or omitted in this Quarterly Report. The comparability of certain 2021 amounts to prior periods could be impacted as a result of the Merger (as defined below) with Montage Resources (“Montage”) in November 2020. The Company believes the disclosures made are adequate to make the information presented not misleading. The consolidated financial statements contained in this report include all normal and recurring material adjustments that, in the opinion of management, are necessary for a fair statement of the financial position, results of operations and cash flows for the interim periods presented herein. It is recommended that these consolidated financial statements be read in conjunction with the consolidated financial statements and the notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2020 (“2020 Annual Report”). The Company’s significant accounting policies, which have been reviewed and approved by the Audit Committee of the Company’s Board of Directors, are summarized in Note 1 in the Notes to the Consolidated Financial Statements included in the Company’s 2020 Annual Report.

ACQUISITION

ACQUISITION	3 Months Ended
	Mar. 31, 2021
Business Combinations [Abstract]
ACQUISITION	ACQUISITION Montage Resources Merger On August 12, 2020, Southwestern entered into an Agreement and Plan of Merger (the “Agreement and Plan of Merger”) with Montage whereby Montage would merge with and into Southwestern, with Southwestern continuing as the surviving company (the "Merger"). On November 12, 2020, Montage’s stockholders voted to approve the Merger and it was made effective on November 13, 2020. The Merger added to Southwestern’s oil and gas portfolio in Appalachia. In exchange for each share of Montage common stock, Montage stockholders received 1.8656 shares of Southwestern common stock, plus cash in lieu of any fractional share of Southwestern common stock that otherwise would have been issued, based on the average price of $3.05 per share of Southwestern common stock on the NYSE on November 13, 2020. Following the closing of the Merger, Southwestern's existing shareholders and Montage's existing shareholders owned approximately 90% and 10%, respectively, of the outstanding shares of the combined company. In anticipation of the Merger, in August 2020 Southwestern issued $350 million of new senior unsecured notes and 63,250,000 shares of common stock for $152 million after deducting underwriting discounts and offering expenses. The Company used the net proceeds from the debt and common stock offerings and borrowings under its revolving credit facility to fund a redemption of $510 million aggregate principal amount of Montage's outstanding 8.875% senior notes due 2023 (the "Montage Notes") and related accrued interest in connection with the closing of the Merger. See Note 7 and Note 11 for additional information. The Merger constituted a business combination and was accounted for using the acquisition method of accounting. The following table presents the fair value of consideration transferred to Montage stockholders as a result of the Merger: (in millions, except share, per share amounts) As of November 13, 2020 Shares of Southwestern common stock issued in respect of outstanding Montage common stock 67,311,166 Shares of Southwestern common stock issued in respect of Montage stock-based awards 2,429,682 69,740,848 NYSE closing price per share of Southwestern common shares on November 13, 2020 $ 3.05 Total consideration (fair value of Southwestern common shares issued) $ 213 Increase in Southwestern common stock ($0.01 par value per share) 1 Increase in Southwestern additional paid-in capital $ 212 The assets acquired and liabilities assumed were recorded at their preliminary estimated fair values at the date of the Merger. The following table sets forth the fair value of the assets acquired and liabilities assumed as of the acquisition date. Although the purchase price allocation is substantially complete as of the date of this filing, there may be further adjustments to the Company’s natural gas and oil properties as the studies necessary to determine the fair value are finalized. These amounts will be finalized no later than one year from the acquisition date. For the three months ended March 31, 2021 there were no changes to the allocation presented in the 2020 Form 10-K. (in millions) As of November 13, 2020 Consideration: Fair value of Southwestern’s stock issued on November 13, 2020 $ 213 Fair Value of Assets Acquired: Cash and cash equivalents 3 Accounts receivable 73 Other current assets 1 Commodity derivative assets 11 Evaluated oil and gas properties 1,012 Unevaluated oil and gas properties 90 Other property, plant and equipment 28 Other long-term assets 26 Total assets acquired 1,244 Fair Value of Liabilities Assumed: Accounts payable 145 Other current liabilities 49 Derivative liabilities 70 Revolving credit facility 200 Senior unsecured notes 522 Asset retirement obligations 28 Other noncurrent liabilities 17 Total liabilities assumed 1,031 Net Assets Acquired and Liabilities Assumed $ 213 For the three months ended March 31, 2021, revenues and operating income associated with the operations acquired through the Merger totaled $130 million and $61 million, respectively. The following table presents selected unaudited pro forma condensed financial information for the three months ended March 31, 2020 as if the Merger had occurred on January 1, 2019: (in millions, except per share amounts) Pro forma results for the three months ended March 31, 2020 Revenues $ 725 Net income (loss) attributable to common stock $ (1,498) The unaudited pro forma information is not necessarily indicative of the operating results that would have occurred had the Merger been completed at January 1, 2019, nor is it necessarily indicative of future operating results of the combined entity. The unaudited pro forma information gives effect to the Merger and related equity and debt issuances along with the use of proceeds therefrom as if they had occurred on January 1, 2019. The unaudited pro forma information for 2020 is a result of combining the statements of operations of Southwestern with the pre-Merger results of Montage from January 1, 2020, and 2019 and included adjustments for revenues and direct expenses. The pro forma results exclude any cost savings anticipated as a result of the Merger and the impact of any Merger-related costs. The pro forma results include adjustments to DD&A (depreciation, depletion and amortization) based on the purchase price allocated to property, plant, and equipment and the estimated useful lives as well as adjustments to interest expense. Interest expense was adjusted to reflect the retirement of the Montage senior notes, the Montage credit facility, all related accrued interest and the associated decrease in amortization of issuance costs related to the Montage notes and revolving line of credit. This decrease was partially offset by increases in interest on debt associated with the issuance of $350 million in new 8.375% Senior Notes due 2028 related to the Southwestern debt offering and borrowings under Southwestern’s credit facility used to pay off the Montage notes, Montage credit facility and related accrued interest. Management believes the estimates and assumptions are reasonable, and the relative effects of the Merger are properly reflected. Montage Merger-Related Expenses For the three months ended March 31, 2021, the Company incurred $1 million in Merger-related expenses primarily related to one-time severance costs and the accelerated vesting of certain Montage share-based awards, based on the terms of the Agreement and Plan of Merger, for former Montage employees that continued to assist with the transition into 2021.

RESTRUCTURING CHARGES

RESTRUCTURING CHARGES	3 Months Ended
	Mar. 31, 2021
Restructuring and Related Activities [Abstract]
RESTRUCTURING CHARGES	RESTRUCTURING CHARGES On February 24, 2021, the Company notified employees of a workforce reduction plan as part of an ongoing strategic effort to reposition its portfolio, optimize operational performance and improve margins. Affected employees were offered a severance package, which included a one-time payment depending on length of service and, if applicable, the current value of unvested long-term incentive awards that were forfeited. These costs were recognized as restructuring charges for the three months ended March 31, 2021, and were substantially complete by the end of the first quarter of 2021. In February 2020, the Company notified employees of a workforce reduction plan as a result of a strategic realignment of the Company’s organizational structure. Affected employees were offered a severance package, which included a one-time payment depending on length of service and, if applicable, the current value of unvested long-term incentive awards that were forfeited. These costs were recognized as restructuring charges for the three months ended March 31, 2020, and were substantially complete by the end of the first quarter of 2020. The following table presents a summary of the restructuring charges included in Operating Income (Loss) for the three months ended March 31, 2021 and 2020: For the three months ended March 31, (in millions) 2021 2020 Severance (including payroll taxes) (1) $ 6 $ 10 (1) Total restructuring charges were $6 million and $10 million for the Company’s E&P segment for the three months ended March 31, 2021 and March 31, 2020, respectively. The following table presents a reconciliation of the liability associated with the Company’s restructuring activities at March 31, 2021, which is reflected in accounts payable on the consolidated balance sheet: (in millions) Liability at December 31, 2020 $ 3 Additions 6 Distributions (9) Liability at March 31, 2021 $ —

REVENUE RECOGNITION

REVENUE RECOGNITION	3 Months Ended
	Mar. 31, 2021
Revenue from Contract with Customer [Abstract]
REVENUE RECOGNITION	REVENUE RECOGNITION Revenues from Contracts with Customers Natural gas and liquids. Natural gas, oil and NGL sales are recognized when control of the product is transferred to the customer at a designated delivery point. The pricing provisions of the Company’s contracts are primarily tied to a market index with certain adjustments based on factors such as delivery, quality of the product and prevailing supply and demand conditions in the geographic areas in which the Company operates. Under the Company’s sales contracts, the delivery of each unit of natural gas, oil and NGLs represents a separate performance obligation, and revenue is recognized at the point in time when the performance obligations are fulfilled. There is no significant financing component to the Company’s revenues as payment terms are typically within 30 to 60 days of control transfer. Furthermore, consideration from a customer corresponds directly with the value to the customer of the Company’s performance completed to date. As a result, the Company recognizes revenue in the amount for which the Company has a right to invoice and has not disclosed information regarding its remaining performance obligations. The Company records revenue from its natural gas and liquids production in the amount of its net revenue interest in sales from its properties. Accordingly, natural gas and liquid sales are not recognized for deliveries in excess of the Company’s net revenue interest, while natural gas and liquid sales are recognized for any under-delivered volumes. Production imbalances are generally recorded as receivables and payables and not contract assets or contract liabilities as the imbalances are between the Company and other working interest owners, not the end customer. Marketing. The Company, through its marketing affiliate, markets natural gas, oil and NGLs for its affiliated E&P company as well as other joint interest owners that choose to market with the Company. In addition, the Company markets some products purchased from third parties. Marketing revenues for natural gas, oil and NGL sales are recognized when control of the product is transferred to the customer at a designated delivery point. The pricing provisions of the Company’s contracts are primarily tied to market indices with certain adjustments based on factors such as delivery, quality of the product and prevailing supply and demand conditions. Under the Company’s marketing contracts, the delivery of each unit of natural gas, oil and NGLs represents a separate performance obligation, and revenue is recognized at the point in time when the performance obligations are fulfilled. Customers are invoiced and revenues are recorded each month as natural gas, oil and NGLs are delivered, and payment terms are typically within 30 to 60 days of control transfer. Furthermore, consideration from a customer corresponds directly with the value to the customer of the Company’s performance completed to date. As a result, the Company recognizes revenue in the amount for which the Company has a right to invoice and has not disclosed information regarding its remaining performance obligations. Disaggregation of Revenues The Company presents a disaggregation of E&P revenues by product on the consolidated statements of operations net of intersegment revenues. The following table reconciles operating revenues as presented on the consolidated statements of operations to the operating revenues by segment: (in millions) E&P Marketing Intersegment Total Three months ended March 31, 2021 Gas sales $ 451 $ — $ 13 $ 464 Oil sales 80 — 1 81 NGL sales 173 — — 173 Marketing — 996 (644) 352 Other (1) 1 1 — 2 Total $ 705 $ 997 $ (630) $ 1,072 Three months ended March 31, 2020 Gas sales $ 239 $ — $ 9 $ 248 Oil sales 52 — — 52 NGL sales 50 — — 50 Marketing — 548 (309) 239 Other (2) 3 — — 3 Total $ 344 $ 548 $ (300) $ 592 (1) For the three months ended March 31, 2021, other E&P revenues consists primarily of gains on purchaser imbalances associated with certain NGLs and other Marketing revenues consists primarily of sales of gas from storage. (2) For the three months ended March 31, 2020, other E&P revenues consists primarily of gains on purchaser imbalances associated with certain NGLs. Associated E&P revenues are also disaggregated for analysis on a geographic basis by the core areas in which the Company operates, which are in Pennsylvania, West Virginia and Ohio. For the three months ended March 31, (in millions) 2021 2020 Northeast Appalachia $ 263 $ 195 Southwest Appalachia 441 149 Other 1 — Total $ 705 $ 344 Receivables from Contracts with Customers The following table reconciles the Company’s receivables from contracts with customers to consolidated accounts receivable as presented on the consolidated balance sheet: (in millions) March 31, 2021 December 31, 2020 Receivables from contracts with customers $ 381 $ 350 Other accounts receivable 19 18 Total accounts receivable $ 400 $ 368 Amounts recognized against the Company’s allowance for doubtful accounts related to receivables arising from contracts with customers were immaterial for the three months ended March 31, 2021 and 2020. The Company has no contract assets or contract liabilities associated with its revenues from contracts with customers.

CASH AND CASH EQUIVALENTS

CASH AND CASH EQUIVALENTS	3 Months Ended
	Mar. 31, 2021
Cash and Cash Equivalents [Abstract]
CASH AND CASH EQUIVALENTS	CASH AND CASH EQUIVALENTS The following table presents a summary of cash and cash equivalents as of March 31, 2021 and December 31, 2020: (in millions) March 31, 2021 December 31, 2020 Cash $ 4 $ 13 Marketable securities (1) — — Total $ 4 $ 13 (1) Typically consists of government stable value money market funds.

NATURAL GAS AND OIL PROPERTIES

NATURAL GAS AND OIL PROPERTIES	3 Months Ended
	Mar. 31, 2021
Oil and Gas Exploration and Production Industries Disclosures [Abstract]
NATURAL GAS AND OIL PROPERTIES	NATURAL GAS AND OIL PROPERTIES The Company utilizes the full cost method of accounting for costs related to the exploration, development and acquisition of natural gas and oil properties. Under this method, all such costs (productive and nonproductive), including salaries, benefits and other internal costs directly attributable to these activities, are capitalized on a country-by-country basis and amortized over the estimated lives of the properties using the units-of-production method. These capitalized costs are subject to a ceiling test that limits such pooled costs, net of applicable deferred taxes, to the aggregate of the present value of future net revenues attributable to proved natural gas, oil and NGL reserves discounted at 10% (standardized measure). Any costs in excess of the ceiling are written off as a non-cash expense. The expense may not be reversed in future periods, even though higher natural gas, oil and NGL prices may subsequently increase the ceiling. Companies using the full cost method are required to use the average quoted price from the first day of each month from the previous 12 months, including the impact of derivatives designated for hedge accounting, to calculate the ceiling value of their reserves. The Company had no hedge positions that were designated for hedge accounting as of March 31, 2021. Prices used to calculate the ceiling value of reserves were as follows: March 31, 2021 March 31, 2020 Natural gas (per MMBtu) $ 2.16 $ 2.30 Oil (per Bbl) $ 40.01 $ 55.77 NGLs (per Bbl) $ 13.57 $ 9.96 Using the average quoted prices above, adjusted for market differentials, the Company’s net book value of its United States natural gas and oil properties did not exceed the ceiling amount at March 31, 2021, and the Company had no derivative positions that were designated for hedge accounting as of March 31, 2021. Decreases in market prices as well as changes in production rates, levels of reserves, evaluation of costs excluded from amortization, future development costs and production costs could result in future ceiling test impairments. No impairment expense was recorded for the three months ended March 31, 2021 in relation to the recently acquired Montage natural gas and oil properties. These properties were recorded at fair value as of November 13, 2020, in accordance with Accounting Standards Codification (“ASC”) Topic 820 – Fair Value Measurement. In the fourth quarter of 2020, pursuant to SEC guidance, the Company determined that the fair value of the properties acquired at the closing of the Merger clearly exceeded the related full-cost ceiling limitation beyond a reasonable doubt and received a waiver from the SEC to exclude the properties acquired in the Merger from the ceiling test calculation. This waiver was granted for all reporting periods through and including the quarter ending September 30, 2021, as long as the Company can continue to demonstrate that the fair value of properties acquired clearly exceeds the full cost ceiling limitation beyond a reasonable doubt in each reporting period. As part of the waiver received from the SEC, the Company is required to disclose what the full cost ceiling test impairment amounts for all periods presented in each applicable quarterly and annual filing would have been if the waiver had not been granted. The fair value of the properties acquired in the Merger was based on forward strip natural gas and oil pricing existing at the date of the Merger, and the Company affirmed that there has not been a material decline to the fair value of these acquired assets since the Merger. The properties acquired in the Merger have an unamortized cost at March 31, 2021 of $1,102 million. Due to the improvement in commodity prices in the first quarter of 2021, no impairment charge would have been recorded for the three months ended March 31, 2021 had the recently acquired Montage natural gas and oil properties been included in the full cost ceiling test. The Company’s net book value of its United States natural gas and oil properties exceeded the ceiling by $1.5 billion at March 31, 2020, resulting in a non-cash ceiling test impairment for the three months ended March 31, 2020.

EARNINGS PER SHARE

EARNINGS PER SHARE	3 Months Ended
	Mar. 31, 2021
Earnings Per Share [Abstract]
EARNINGS PER SHARE	EARNINGS PER SHARE Basic earnings per common share is computed by dividing net income by the weighted average number of common shares outstanding during the reportable period. The diluted earnings per share calculation adds to the weighted average number of common shares outstanding: the incremental shares that would have been outstanding assuming the exercise of dilutive stock options, the vesting of unvested restricted shares of common stock, restricted stock units and performance units. An antidilutive impact is an increase in earnings per share or a reduction in net loss per share resulting from the conversion, exercise or contingent issuance of certain securities. In August 2020, the Company completed an underwritten public offering of 63,250,000 shares of its common stock with an offering price to the public of $2.50 per share. Net proceeds after deducting underwriting discounts and offering expenses were approximately $152 million. See Note 2 for additional details regarding the Company’s use of proceeds from the equity offering. The following table presents the computation of earnings per share for the three months ended March 31, 2021 and 2020: For the three months ended March 31, (in millions, except share/per share amounts) 2021 2020 Net income (loss) $ 80 $ (1,547) Number of common shares: Weighted average outstanding 675,385,145 540,308,491 Issued upon assumed exercise of outstanding stock options — — Effect of issuance of non-vested restricted common stock 870,541 — Effect of issuance of non-vested restricted units 804,944 — Effect of issuance of non-vested performance units 2,807,195 — Weighted average and potential dilutive outstanding 679,867,825 540,308,491 Earnings per common share Basic $ 0.12 $ (2.86) Diluted $ 0.12 $ (2.86) The following table presents the common stock shares equivalent excluded from the calculation of diluted earnings per share for the three months ended March 31, 2021 and 2020, as they would have had an antidilutive effect: For the three months ended March 31, 2021 2020 Unexercised stock options 3,795,091 4,584,563 Unvested share-based payment — 1,006,860 Restricted stock units 3,987,291 1,312,293 Performance units — 2,275,498 Total 7,782,382 9,179,214

DERIVATIVES AND RISK MANAGEMENT

DERIVATIVES AND RISK MANAGEMENT	3 Months Ended
	Mar. 31, 2021
Derivative Instruments and Hedging Activities Disclosure [Abstract]
DERIVATIVES AND RISK MANAGEMENT	DERIVATIVES AND RISK MANAGEMENT The Company is exposed to volatility in market prices and basis differentials for natural gas, oil and NGLs which impacts the predictability of its cash flows related to the sale of those commodities. These risks are managed by the Company’s use of certain derivative financial instruments. As of March 31, 2021, the Company’s derivative financial instruments consisted of fixed price swaps, two-way costless collars, three-way costless collars, basis swaps, call options, swaptions and interest rate swaps. A description of the Company’s derivative financial instruments is provided below: Fixed price swaps If the Company sells a fixed price swap, the Company receives a fixed price for the contract and pays a floating market price to the counterparty. If the Company purchases a fixed price swap, the Company receives a floating market price for the contract and pays a fixed price to the counterparty. Two-way costless collars Arrangements that contain a fixed floor price (“purchased put option”) and a fixed ceiling price (“sold call option”) based on an index price which, in aggregate, have no net cost. At the contract settlement date, (1) if the index price is higher than the ceiling price, the Company pays the counterparty the difference between the index price and ceiling price, (2) if the index price is between the floor and ceiling prices, no payments are due from either party, and (3) if the index price is below the floor price, the Company will receive the difference between the floor price and the index price. Three-way costless collars Arrangements that contain a purchased put option, a sold call option and a sold put option based on an index price that, in aggregate, have no net cost. At the contract settlement date, (1) if the index price is higher than the sold call strike price, the Company pays the counterparty the difference between the index price and sold call strike price, (2) if the index price is between the purchased put strike price and the sold call strike price, no payments are due from either party, (3) if the index price is between the sold put strike price and the purchased put strike price, the Company will receive the difference between the purchased put strike price and the index price, and (4) if the index price is below the sold put strike price, the Company will receive the difference between the purchased put strike price and the sold put strike price. Basis swaps Arrangements that guarantee a price differential for natural gas from a specified delivery point. If the Company sells a basis swap, the Company receives a payment from the counterparty if the price differential is greater than the stated terms of the contract and pays the counterparty if the price differential is less than the stated terms of the contract. If the Company purchases a basis swap, the Company pays the counterparty if the price differential is greater than the stated terms of the contract and receives a payment from the counterparty if the price differential is less than the stated terms of the contract. Options (Calls and Puts) The Company purchases and sells options in exchange for premiums. If the Company purchases a call option, the Company receives from the counterparty the excess (if any) of the market price over the strike price of the call option at the time of settlement, but if the market price is below the call’s strike price, no payment is due from either party. If the Company sells a call option, the Company pays the counterparty the excess (if any) of the market price over the strike price of the call option at the time of settlement, but if the market price is below the call’s strike price, no payment is due from either party. If the Company purchases a put option, the Company receives from the counterparty the excess (if any) of the strike price over the market price of the put option at the time of settlement, but if the market price is above the put’s strike price, no payment is due from either party. If the Company sells a put option, the Company pays the counterparty the excess (if any) of the strike price over the market price of the put option at the time of settlement, but if the market price is above the put’s strike price, no payment is due from either party. Swaptions Instruments that refer to an option to enter into a fixed price swap. In exchange for an option premium, the purchaser gains the right but not the obligation to enter a specified swap agreement with the issuer for specified future dates. If the Company sells a swaption, the counterparty has the right to enter into a fixed price swap wherein the Company receives a fixed price for the contract and pays a floating market price to the counterparty. If the Company purchases a swaption, the Company has the right to enter into a fixed price swap wherein the Company receives a floating market price for the contract and pays a fixed price to the counterparty. Interest rate swaps Interest rate swaps are used to fix or float interest rates on existing or anticipated indebtedness. The purpose of these instruments is to manage the Company’s existing or anticipated exposure to unfavorable interest rate changes. The Company contracts with counterparties for its derivative instruments that it believes are creditworthy at the time the transactions are entered into, and the Company actively monitors the credit ratings and credit default swap rates of these counterparties where applicable. However, there can be no assurance that a counterparty will be able to meet its obligations to the Company. The fair value of the Company’s derivative assets and liabilities includes a non-performance risk factor. See Note 10 for additional details regarding the Company’s fair value measurements of its derivative positions. The Company presents its derivative positions on a gross basis and does not net the asset and liability positions. The following tables provide information about the Company’s financial instruments that are sensitive to changes in commodity prices and that are used to protect the Company’s exposure. None of the financial instruments below are designated for hedge accounting treatment. The tables present the notional amount, the weighted average contract prices and the fair value by expected maturity dates as of March 31, 2021: Financial Protection on Production Weighted Average Price per MMBtu Volume (Bcf) Swaps Sold Puts Purchased Puts Sold Calls Basis Differential Fair Value at March 31, 2021 (in millions) Natural Gas 2021 Fixed price swaps 176 $ 2.79 $ — $ — $ — $ — $ 14 Two-way costless collars 195 — — 2.57 2.93 — 1 Three-way costless collars 218 — 2.17 2.50 2.84 — (23) Total 589 $ (8) 2022 Fixed price swaps 112 $ 2.68 $ — $ — $ — $ — $ (2) Two-way costless collars 63 — — 2.52 3.03 — (3) Three-way costless collars 278 — 2.06 2.50 2.97 — (13) Total 453 $ (18) 2023 Three-way costless collars 103 $ — $ 2.05 $ 2.46 $ 3.01 $ — $ (4) Basis Swaps 2021 233 $ — $ — $ — $ — $ (0.49) $ 39 2022 220 — — — — (0.44) 24 2023 119 — — — — (0.56) 4 2024 24 — — — — (0.64) 1 2025 9 — — — — (0.64) — Total 605 $ 68 Volume (MBbls) Weighted Average Strike Price per Bbl Fair Value at March 31, 2021 (in millions) Swaps Sold Puts Purchased Puts Sold Calls Oil 2021 Fixed price swaps 3,272 $ 49.27 $ — $ — $ — $ (29) Two-way costless collars 156 — — 37.79 45.73 (2) Three-way costless collars 1,498 — 37.86 47.70 53.10 (10) Total 4,926 $ (41) 2022 Fixed price swaps 1,719 $ 48.54 $ — $ — $ — $ (10) Three-way costless collars 1,380 — 39.89 50.23 57.05 (4) Total 3,099 $ (14) 2023 Three-way costless collars 1,268 $ — $ 33.97 $ 45.51 $ 56.12 $ (4) Ethane 2021 Fixed price swaps 4,429 $ 7.17 $ — $ — $ — $ (11) Two-way costless collars 440 — — 7.14 10.40 — Total 4,869 $ (11) 2022 Fixed price swaps 1,758 $ 8.68 $ — $ — $ — $ (1) Two-way costless collars 135 — — 7.56 9.66 — Total 1,893 $ (1) Propane 2021 Fixed price swaps 5,443 $ 20.84 $ — $ — $ — $ (69) 2022 Fixed price swaps 2,723 $ 21.83 $ — $ — $ — $ (14) Three-way costless collars 305 — 16.80 21.00 31.92 (1) Total 3,028 (15) Normal Butane 2021 Fixed price swaps 1,568 $ 25.30 $ — $ — $ — $ (19) 2022 Fixed price swaps 888 $ 24.47 $ — $ — $ — $ (5) Natural Gasoline 2021 Fixed price swaps 1,513 $ 37.91 $ — $ — $ — $ (27) 2022 Fixed price swaps 857 $ 40.48 $ — $ — $ — $ (8) Other Derivative Contracts Volume (Bcf) Weighted Average Strike Price per MMBtu Fair Value at March 31, 2021 (in millions) Call Options – Natural Gas (Net) 2021 57 $ 3.19 $ (4) 2022 77 3.00 (16) 2023 46 2.94 (10) 2024 9 3.00 (3) Total 189 $ (33) Put Options – Natural Gas 2021 14 $ 2.00 $ — 2022 5 2.00 (1) Total 19 $ (1) Volume (MBbls) Weighted Average Strike Price per Bbl Fair Value at March 31, 2021 (in millions) Call Options – Oil 2021 171 $ 60.00 $ (1) Volume (Bcf) Weighted Average Strike Price per MMBtu Fair Value at March 31, 2021 (in millions) Swaptions – Natural Gas 2021 (1) 18 $ 3.00 $ (1) (1) The Company has sold swaptions with an underlying tenor of January 2022 to December 2022, with an exercise date of December 23, 2021. Volume (Bcf) Weighted Average Strike Price per MMBtu Fair Value at March 31, 2021 (in millions) Swaps Basis Differential Storage (1) 2021 Purchased fixed price swaps 2 $ 2.34 $ — $ — Purchased basis swaps 1 — (0.88) — Fixed price swaps — 2.23 — — Basis swaps — — (0.57) — Total 3 $ — 2022 Purchased fixed price swaps — $ 2.14 $ — $ — Fixed price swaps 2 2.82 — — Basis swaps 1 — (0.57) — Total 3 $ — (1) The Company has entered into certain derivatives to protect the value of volumes of natural gas injected into a storage facility that will be withdrawn and sold at a later date. Purchased Fixed Price Swaps – Marketing (Natural Gas) (1) Volume (Bcf) Weighted Average Strike Price per MMBtu Fair Value at March 31, 2021 (in millions) 2021 4 2.44 1 (1) The Company has entered into a limited number of derivatives to protect the value of certain long-term sales contracts. At March 31, 2021, the net fair value of the Company’s financial instruments related to commodities was a $211 million liability and included a net reduction of the liability of less than $1 million related to non-performance risk. See Note 10 for additional details regarding the Company’s fair value measurements of its derivative positions. As of March 31, 2021, the Company had no positions designated for hedge accounting treatment. Gains and losses on derivatives that are not designated for hedge accounting treatment, or do not meet hedge accounting requirements, are recorded as a component of gain (loss) on derivatives on the consolidated statements of operations. Accordingly, the gain (loss) on derivatives component of the statement of operations reflects the gain and losses on both settled and unsettled derivatives. Only the settled gains and losses are included in the Company’s realized commodity price calculations. The balance sheet classification of the assets and liabilities related to derivative financial instruments (none of which are designated for hedge accounting treatment) is summarized below as of March 31, 2021 and December 31, 2020: Derivative Assets Fair Value (in millions) Balance Sheet Classification March 31, 2021 December 31, 2020 Derivatives not designated as hedging instruments: Purchased fixed price swaps – natural gas Derivative assets $ 1 $ 1 Fixed price swaps – natural gas Derivative assets 25 37 Fixed price swaps – oil Derivative assets — 13 Two-way costless collars – natural gas Derivative assets 39 54 Three-way costless collars – natural gas Derivative assets 39 57 Three-way costless collars – oil Derivative assets 6 15 Basis swaps – natural gas Derivative assets 46 60 Call options – natural gas Derivative assets 1 4 Fixed price swaps – natural gas Other long-term assets — 7 Fixed price swaps – oil Other long-term assets — 2 Fixed price swaps – propane Other long-term assets 1 — Two-way costless collars – natural gas Other long-term assets 2 20 Three-way costless collars – natural gas Other long-term assets 82 87 Three-way costless collars – oil Other long-term assets 14 15 Basis swaps – natural gas Other long-term assets 39 15 Interest rate swaps Other long-term assets 1 — Total derivative assets $ 296 $ 387 Derivative Liabilities Fair Value (in millions) Balance Sheet Classification March 31, 2021 December 31, 2020 Derivatives not designated as hedging instruments: Fixed price swaps – natural gas Derivative liabilities $ 12 $ 7 Fixed price swaps – oil Derivative liabilities 32 12 Fixed price swaps – ethane Derivative liabilities 11 10 Fixed price swaps – propane Derivative liabilities 76 36 Fixed price swaps – normal butane Derivative liabilities 21 8 Fixed price swaps – natural gasoline Derivative liabilities 30 13 Two-way costless collars – natural gas Derivative liabilities 39 43 Two-way costless collars – oil Derivative liabilities 2 1 Three-way costless collars – natural gas Derivative liabilities 73 82 Three-way costless collars – oil Derivative liabilities 17 15 Basis swaps – natural gas Derivative liabilities 9 3 Call options – natural gas Derivative liabilities 13 12 Call options – oil Derivative liabilities 1 — Put options – natural gas Derivative liabilities 1 1 Swaptions – natural gas Derivative liabilities 1 2 Fixed price swaps – natural gas Long-term derivative liabilities 1 3 Fixed price swaps – oil Long-term derivative liabilities 7 2 Fixed price swaps – ethane Long-term derivative liabilities 1 — Fixed price swaps – propane Long-term derivative liabilities 8 2 Fixed price swaps – normal butane Long-term derivative liabilities 3 1 Fixed price swaps – natural gasoline Long-term derivative liabilities 5 2 Two-way costless collars – natural gas Long-term derivative liabilities 4 21 Three-way costless collars – natural gas Long-term derivative liabilities 88 102 Three-way costless collars – oil Long-term derivative liabilities 21 15 Three-way costless collars – propane Long-term derivative liabilities 1 — Basis swap – natural gas Long-term derivative liabilities 8 7 Call options – natural gas Long-term derivative liabilities 21 28 Total derivative liabilities $ 506 $ 428 The following tables summarize the before-tax effect of the Company’s derivative instruments on the consolidated statements of operations for the three months ended March 31, 2021 and 2020: Unsettled Gain (Loss) on Derivatives Recognized in Earnings Consolidated statement of Operations Classification of Gain (Loss) on Derivatives, Unsettled For the three months ended March 31, Derivative Instrument 2021 2020 (in millions) Purchased fixed price swaps – natural gas Gain (Loss) on Derivatives $ — $ (1) Purchased fixed price swaps – oil Gain (Loss) on Derivatives — (5) Fixed price swaps – natural gas Gain (Loss) on Derivatives (22) 103 Fixed price swaps – oil Gain (Loss) on Derivatives (40) 118 Fixed price swaps – ethane Gain (Loss) on Derivatives (2) 12 Fixed price swaps – propane Gain (Loss) on Derivatives (45) 36 Fixed price swaps – normal butane Gain (Loss) on Derivatives (15) — Fixed price swaps – natural gasoline Gain (Loss) on Derivatives (20) — Two-way costless collars – natural gas Gain (Loss) on Derivatives (12) (4) Two-way costless collars – oil Gain (Loss) on Derivatives (1) 19 Two-way costless collars – propane Gain (Loss) on Derivatives — 2 Three-way costless collars – natural gas Gain (Loss) on Derivatives — (51) Three-way costless collars – oil Gain (Loss) on Derivatives (18) 25 Three-way costless collars – propane Gain (Loss) on Derivatives (1) — Basis swaps – natural gas Gain (Loss) on Derivatives 3 (1) Call options – natural gas Gain (Loss) on Derivatives 3 (5) Call options – oil Gain (Loss) on Derivatives (1) 1 Swaptions – natural gas Gain (Loss) on Derivatives 1 — Purchased fixed price swap – natural gas storage Gain (Loss) on Derivatives — (1) Fixed price swap – natural gas storage Gain (Loss) on Derivatives — (1) Interest rate swaps Gain (Loss) on Derivatives 1 (1) Total gain (loss) on unsettled derivatives $ (169) $ 246 Settled Gain (Loss) on Derivatives Recognized in Earnings (1) Consolidated statement of Operations Classification of Gain (Loss) on Derivatives, Settled For the three months ended March 31, Derivative Instrument 2021 2020 (in millions) Purchased fixed price swaps – natural gas Gain (Loss) on Derivatives $ — $ (1) Fixed price swaps – natural gas Gain (Loss) on Derivatives 5 5 Fixed price swaps – oil Gain (Loss) on Derivatives (17) 9 Fixed price swaps – ethane Gain (Loss) on Derivatives (4) 6 Fixed price swaps – propane Gain (Loss) on Derivatives (30) 10 Fixed price swaps – normal butane Gain (Loss) on Derivatives (7) — Fixed price swaps – natural gasoline Gain (Loss) on Derivatives (9) — Two-way costless collars – natural gas Gain (Loss) on Derivatives 2 6 Two-way costless collars – oil Gain (Loss) on Derivatives (1) 3 Two-way costless collars – propane Gain (Loss) on Derivatives — 1 Three-way costless collars – natural gas Gain (Loss) on Derivatives 1 36 Three-way costless collars – oil Gain (Loss) on Derivatives (1) 1 Basis swaps – natural gas Gain (Loss) on Derivatives 41 16 Put options – natural gas Gain (Loss) on Derivatives (2) (2) — Fixed price swaps – natural gas storage Gain (Loss) on Derivatives — 1 Total gain (loss) on settled derivatives $ (22) $ 93 Total gain (loss) on derivatives $ (191) $ 339 (1) The Company calculates gain (loss) on derivatives, settled, as the summation of gains and losses on positions that settled within the period.

RECLASSIFICATIONS FROM ACCUMULA

RECLASSIFICATIONS FROM ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)	3 Months Ended
	Mar. 31, 2021
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
RECLASSIFICATIONS FROM ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)	RECLASSIFICATIONS FROM ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) Changes in accumulated other comprehensive income for the first three months of 2021 were related to the Company’s pension and other postretirement benefits. The following tables detail the components of accumulated other comprehensive income and the related tax effects for the three months ended March 31, 2021: (in millions) Pension and Other Postretirement Foreign Currency Total Beginning balance December 31, 2020 $ (24) $ (14) $ (38) Other comprehensive income before reclassifications — — — Amounts reclassified from other comprehensive income (1) — — — Net current-period other comprehensive income — — — Ending balance March 31, 2021 $ (24) $ (14) $ (38) Details about Accumulated Other Comprehensive Income Affected Line Item in the Consolidated Statement of Operations Amount Reclassified from Accumulated Other Comprehensive Income For the three months ended (in millions) Pension and other postretirement: Amortization of prior service cost and net gain (1) Other Income, Net $ — Provision (Benefit) for Income Taxes — Net Income (Loss) $ — Total reclassifications for the period Net Income (Loss) $ — (1) For the three months ended March 31, 2021, the amount reclassified from accumulated other comprehensive income was immaterial. See Note 14 for additional details regarding the Company’s pension and other postretirement benefit plans.

FAIR VALUE MEASUREMENTS

FAIR VALUE MEASUREMENTS	3 Months Ended
	Mar. 31, 2021
Fair Value Disclosures [Abstract]
FAIR VALUE MEASUREMENTS	FAIR VALUE MEASUREMENTS Assets and liabilities measured at fair value on a recurring basis The carrying amounts and estimated fair values of the Company’s financial instruments as of March 31, 2021 and December 31, 2020 were as follows: March 31, 2021 December 31, 2020 (in millions) Carrying Fair Carrying Fair Cash and cash equivalents $ 4 $ 4 $ 13 $ 13 2018 revolving credit facility due April 2024 567 567 700 700 Senior notes (1) 2,471 2,640 2,471 2,609 Derivative instruments, net (210) (210) (41) (41) (1) Excludes unamortized debt issuance costs and debt discounts. The fair value hierarchy prioritizes the inputs to valuation techniques used to measure fair value. As presented in the tables below, this hierarchy consists of three broad levels: Level 1 valuations - Consist of unadjusted quoted prices in active markets for identical assets and liabilities and have the highest priority. Level 2 valuations - Consist of quoted market information for the calculation of fair market value. Level 3 valuations - Consist of internal estimates and have the lowest priority. The carrying values of cash and cash equivalents, including marketable securities, accounts receivable, other current assets, accounts payable and other current liabilities on the consolidated balance sheets approximate fair value because of their short-term nature. For debt and derivative instruments, the following methods and assumptions were used to estimate fair value: Debt: The fair values of the Company’s senior notes are based on the market value of the Company’s publicly traded debt as determined based on the market prices of the Company’s senior notes. The fair value of the Company’s 4.10% Senior Notes due March 2022 is considered to be a Level 2 measurement on the fair value hierarchy. The fair values of the Company’s remaining senior notes are considered the be a Level 1 measurement. The carrying values of the borrowings under the Company’s revolving credit facility (to the extent utilized) approximates fair value because the interest rate is variable and reflective of market rates. The Company considers the fair value of its revolving credit facility to be a Level 1 measurement on the fair value hierarchy. Derivative Instruments: The Company measures the fair value of its derivative instruments based upon a pricing model that utilizes market-based inputs, including, but not limited to, the contractual price of the underlying position, current market prices, natural gas and liquids forward curves, discount rates such as the LIBOR curve for a similar duration of each outstanding position, volatility factors and non-performance risk. Non-performance risk considers the effect of the Company’s credit standing on the fair value of derivative liabilities and the effect of counterparty credit standing on the fair value of derivative assets. Both inputs to the model are based on published credit default swap rates and the duration of each outstanding derivative position. As of March 31, 2021 and December 31, 2020, the impact of non-performance risk on the fair value of the Company’s net derivative asset position was a decrease of the net liability of less than $1 million and $1 million, respectively. The Company has classified its derivative instruments into levels depending upon the data utilized to determine their fair values. The Company’s fixed price swaps (Level 2) are estimated using third-party discounted cash flow calculations using the New York Mercantile Exchange (“NYMEX”) futures index for natural gas and oil derivatives and Oil Price Information Service (“OPIS”) for ethane and propane derivatives. The Company utilizes discounted cash flow models for valuing its interest rate derivatives (Level 2). The net derivative values attributable to the Company’s interest rate derivative contracts as of December 31, 2020 are based on (i) the contracted notional amounts, (ii) active market-quoted London Interbank Offered Rate (“LIBOR”) yield curves and (iii) the applicable credit-adjusted risk-free rate yield curve. The Company’s call options, two-way costless collars and three-way costless collars (Level 2) are valued using the Black-Scholes model, an industry standard option valuation model that takes into account inputs such as contract terms, including maturity, and market parameters, including assumptions of the NYMEX and OPIS futures index, interest rates, volatility and credit worthiness. Inputs to the Black-Scholes model, including the volatility input, are obtained from a third-party pricing source, with independent verification of the most significant inputs on a monthly basis. An increase (decrease) in volatility would result in an increase (decrease) in fair value measurement, respectively. The Company’s basis swaps (Level 2) are estimated using third-party calculations based upon forward commodity price curves. Assets and liabilities measured at fair value on a recurring basis are summarized below: March 31, 2021 Fair Value Measurements Using: (in millions) Quoted Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets (Liabilities) at Fair Value Assets Purchased fixed price swaps $ — $ 1 $ — $ 1 Fixed price swaps — 26 — 26 Two-way costless collars — 41 — 41 Three-way costless collars — 141 — 141 Basis swaps — 85 — 85 Call options — 1 — 1 Interest rate swap — 1 — 1 Liabilities Fixed price swaps — (207) — (207) Two-way costless collars — (45) — (45) Three-way costless collars — (200) — (200) Basis swaps — (17) — (17) Call options — (35) — (35) Put options — (1) — (1) Swaptions — (1) — (1) Total (1) $ — $ (210) $ — $ (210) (1) Includes a net reduction to the liability fair value of less than $1 million related to estimated nonperformance risk. December 31, 2020 Fair Value Measurements Using: (in millions) Quoted Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets (Liabilities) at Fair Value Assets Purchased fixed price swaps $ — $ 1 $ — $ 1 Fixed price swaps — 59 — 59 Two-way costless collars — 74 — 74 Three-way costless collars — 174 — 174 Basis swaps — 75 — 75 Call options — 4 — 4 Liabilities Fixed price swaps — (96) — (96) Two-way costless collars — (65) — (65) Three-way costless collars — (214) — (214) Basis swaps — (10) — (10) Call options — (40) — (40) Put options — (1) — (1) Swaptions — (2) — (2) Total (1) $ — $ (41) $ — $ (41) (1) Includes a net reduction to the liability fair value of $1 million related to estimated nonperformance risk.

DEBT

DEBT	3 Months Ended
	Mar. 31, 2021
Debt Disclosure [Abstract]
DEBT	DEBT The components of debt as of March 31, 2021 and December 31, 2020 consisted of the following: March 31, 2021 (in millions) Debt Instrument Unamortized Issuance Expense Unamortized Debt Discount Total Current portion of long-term debt: 4.10% Senior Notes due March 2022 $ 207 $ — $ — $ 207 Total current portion of long-term debt $ 207 $ — $ — $ 207 Long-term debt: Variable rate (2.09% at March 31, 2021) 2018 revolving credit facility due April 2024 $ 567 $ — (1) $ — $ 567 4.95% Senior Notes due January 2025 (2) 856 (4) (1) 851 7.50% Senior Notes due April 2026 618 (5) — 613 7.75% Senior Notes due October 2027 440 (4) — 436 8.375% Senior Notes due September 2028 350 (5) — 345 Total long-term debt $ 2,831 $ (18) $ (1) $ 2,812 Total debt $ 3,038 $ (18) $ (1) $ 3,019 December 31, 2020 (in millions) Debt Instrument Unamortized Issuance Expense Unamortized Debt Discount Total Long-term debt: Variable rate (2.11% at December 31, 2020) 2018 term loan facility due April 2024 $ 700 $ — (1) $ — $ 700 4.10% Senior Notes due March 2022 207 — — 207 4.95% Senior Notes due January 2025 (2) 856 (4) (1) 851 7.50% Senior Notes due April 2026 618 (6) — 612 7.75% Senior Notes due October 2027 440 (5) — 435 8.375% Senior Notes due September 2028 350 (5) — 345 Total long-term debt $ 3,171 $ (20) $ (1) $ 3,150 (1) At March 31, 2021 and December 31, 2020, unamortized issuance expense of $11 million and $12 million, respectively, associated with the 2018 credit facility (as defined below) was classified as other long-term assets on the consolidated balance sheets. (2) Effective in July 2018, the interest rate was 6.20% for the 2025 Notes, reflecting a net downgrade in the Company’s bond ratings since the initial offering. On April 7, 2020, S&P downgraded the Company’s bond rating to BB-, which had the effect of increasing the interest rate on the 2025 Notes to 6.45% following the July 23, 2020 interest payment date. The first coupon payment to the bondholders at the higher interest rate was paid in January 2021. The following is a summary of scheduled debt maturities by year as of March 31, 2021: (in millions) 2021 $ — 2022 207 2023 — 2024 567 2025 856 Thereafter 1,408 $ 3,038 (1) The Company’s current revolving credit facility matures in 2024. Credit Facilities 2018 Revolving Credit Facility In April 2018, the Company replaced its credit facility that was entered into in 2016 with a new revolving credit facility (the “2018 credit facility”) with a group of banks that, as amended, has a maturity date of April 2024. The 2018 credit facility has an aggregate maximum revolving credit amount of $3.5 billion and, in March 2021, the banks participating in the 2018 credit facility reaffirmed the elected borrowing base and aggregate commitments to be $2.0 billion. The borrowing base is subject to redetermination at least twice a year, in April and October, and is secured by substantially all of the assets owned by the Company and its subsidiaries. The permitted lien provisions in certain senior note indentures currently limit liens securing indebtedness to the greater of $2.0 billion or 25% of adjusted consolidated net tangible assets. The Company may utilize the 2018 credit facility in the form of loans and letters of credit. Loans under the 2018 credit facility are subject to varying rates of interest based on whether the loan is a Eurodollar loan or an alternate base rate loan. Eurodollar loans bear interest at the Eurodollar rate, which is adjusted LIBOR for such interest period plus the applicable margin (as those terms are defined in the 2018 credit facility documentation). The applicable margin for Eurodollar loans under the 2018 credit facility, as amended, ranges from 1.75% to 2.75% based on the Company’s utilization of the 2018 credit facility. Alternate base rate loans bear interest at the alternate base rate plus the applicable margin. The applicable margin for alternate base rate loans under the 2018 credit facility, as amended, ranges from 0.75% to 1.75% based on the Company’s utilization of the 2018 credit facility. The 2018 credit facility contains customary representations and warranties and contains covenants including, among others, the following: • a prohibition against incurring debt, subject to permitted exceptions; • a restriction on creating liens on assets, subject to permitted exceptions; • restrictions on mergers and asset dispositions; • restrictions on use of proceeds, investments, transactions with affiliates, or change of principal business; and • maintenance of the following financial covenants, commencing with the fiscal quarter ending June 30, 2018: 1. Minimum current ratio of no less than 1.00 to 1.00, whereby current ratio is defined as the Company’s consolidated current assets (including unused commitments under the credit agreement, but excluding non-cash derivative assets) to consolidated current liabilities (excluding non-cash derivative obligations and current maturities of long-term debt). 2. Maximum total net leverage ratio of no greater than, with respect to each fiscal quarter ending on or after June 30, 2020, 4.00 to 1.00. Total net leverage ratio is defined as total debt less cash on hand (up to the lesser of 10% of credit limit or $150 million) divided by consolidated EBITDAX for the last four consecutive quarters. EBITDAX, as defined in the credit agreement governing the Company’s 2018 credit facility, excludes the effects of interest expense, depreciation, depletion and amortization, income tax, any non-cash impacts from impairments, certain non-cash hedging activities, stock-based compensation expense, non-cash gains or losses on asset sales, unamortized issuance cost, unamortized debt discount and certain restructuring costs. The 2018 credit facility contains customary events of default that include, among other things, the failure to comply with the financial covenants described above, non-payment of principal, interest or fees, violation of covenants, inaccuracy of representations and warranties, bankruptcy and insolvency events, material judgments and cross-defaults to material indebtedness. If an event of default occurs and is continuing, all amounts outstanding under the 2018 credit facility may become immediately due and payable. As of March 31, 2021, the Company was in compliance with all of the covenants contained in the credit agreement governing the 2018 credit facility. Each United States domestic subsidiary of the Company for which the Company owns 100% guarantees the 2018 credit facility. Pursuant to requirements under the indentures governing its senior notes, each subsidiary that became a guarantor of the 2018 credit facility also became a guarantor of each of the Company’s senior notes. As of March 31, 2021, the Company had $233 million in letters of credit and $567 million borrowings outstanding under the 2018 credit facility. The Company currently does not anticipate being required to supply a materially greater amount of letters of credit under its existing contracts. The Company’s debt exposure to the anticipated transition from LIBOR in late 2021 is limited to the 2018 credit facility. Upon announcement by the administrator of LIBOR identifying a specific date for LIBOR cessation, the credit agreement governing the 2018 credit facility will be amended to reference an alternative rate as established by JP Morgan, as Administrative Agent, and the Company. The alternative rate will be based on the prevailing market convention and is expected to be the Secured Overnight Financing Rate (“SOFR”). Senior Notes In January 2015, the Company completed a public offering of $1.0 billion aggregate principal amount of its 4.95% senior notes due 2025 (the “2025 Notes”). The interest rate on the 2025 Notes is determined based upon the public bond ratings from Moody’s and S&P. Downgrades on the 2025 Notes from either rating agency increase interest costs by 25 basis points per downgrade level and upgrades decrease interest costs by 25 basis points per upgrade level, up to the stated coupon rate, on the following semi-annual bond interest payment. Effective in July 2018, the interest rate for the 2025 Notes was 6.20%, reflecting a net downgrade in the Company’s bond ratings since the initial offering. On April 7, 2020, S&P downgraded the Company’s bond rating to BB-, which had the effect of increasing the interest rate on the 2025 Notes to 6.45% following the July 23, 2020 interest payment date. The first coupon payment to the 2025 Notes bondholders at the higher interest rate was paid in January 2021. In the event of future downgrades, the coupons for this series of notes have been capped at 6.95%. In the first quarter of 2020, the Company repurchased $3 million of its 4.10% Senior Notes due 2022, $28 million of its 4.95% Senior Notes due 2025, $18 million of its 7.50% Senior Notes due 2026 and $31 million of its 7.75% Senior Notes due 2027 for $52 million, and recognized a $28 million gain on the extinguishment of debt. In August 2020, the Company completed a public offering of $350 million aggregate principal amount of its 8.375% Senior Notes due 2028 (the “2028 Notes”), with net proceeds from the offering totaling approximately $345 million after underwriting discounts and offering expenses. The 2028 Notes were sold to the public at 100% of their face value. The net proceeds from the notes, in conjunction with the net proceeds from the August 2020 common stock offering and borrowings under the revolving credit facility, were utilized to fund a redemption of $510 million of Montage’s Notes in connection with the closing of the Merger.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	3 Months Ended
	Mar. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES Operating Commitments and Contingencies As of March 31, 2021, the Company’s contractual obligations for demand and similar charges under firm transportation and gathering agreements to guarantee access capacity on natural gas and liquids pipelines and gathering systems totaled approximately $8.4 billion, $436 million of which related to access capacity on future pipeline and gathering infrastructure projects that still require the granting of regulatory approvals and additional construction efforts. The Company also had guarantee obligations of up to $908 million of that amount. As of March 31, 2021, future payments under non-cancelable firm transportation and gathering agreements were as follows: Payments Due by Period (in millions) Total Less than 1 1 to 3 Years 3 to 5 Years 5 to 8 Years More than 8 Infrastructure currently in service $ 7,915 $ 789 $ 1,539 $ 1,295 $ 1,752 $ 2,540 Pending regulatory approval and/or construction (1) 436 2 30 38 81 285 Total transportation charges $ 8,351 $ 791 $ 1,569 $ 1,333 $ 1,833 $ 2,825 (1) Based on estimated in-service dates as of March 31, 2021. Environmental Risk The Company is subject to laws and regulations relating to the protection of the environment. Environmental and cleanup related costs of a non-capital nature are accrued when it is both probable that a liability has been incurred and when the amount can be reasonably estimated. Management believes any future remediation or other compliance related costs will not have a material effect on the financial position, results of operations or cash flows of the Company. Litigation The Company is subject to various litigation, claims and proceedings, most of which have arisen in the ordinary course of business, such as for alleged breaches of contract, miscalculation of royalties, employment matters, traffic accidents, pollution, contamination, encroachment on others’ property or nuisance. The Company accrues for litigation, claims and proceedings when a liability is both probable and the amount can be reasonably estimated. As of March 31, 2021, the Company does not currently have any material amounts accrued related to litigation matters. For any matters not accrued for, it is not possible at this time to estimate the amount of any additional loss, or range of loss, that is reasonably possible, but, based on the nature of the claims, management believes that current litigation, claims and proceedings, individually or in aggregate and after taking into account insurance, are not likely to have a material adverse impact on the Company’s financial position, results of operations or cash flows, for the period in which the effect of that outcome becomes reasonably estimable. Many of these matters are in early stages, so the allegations and the damage theories have not been fully developed, and are all subject to inherent uncertainties; therefore, management’s view may change in the future. St. Lucie County Fire District Firefighters’ Pension Trust On October 17, 2016, the St. Lucie County Fire District Firefighters’ Pension Trust filed a putative class action in the 61st District Court in Harris County, Texas, against the Company, certain of its former officers and current and former directors and the underwriters on behalf of itself and others that purchased certain depositary shares from the Company’s January 2015 equity offering, alleging material misstatements and omissions in the registration statement for that offering. The Company removed the case to federal court, but after a decision by the United States Supreme Court in an unrelated case that these types of cases are not subject to removal, the federal court remanded the case to the Texas state court. The Texas trial court denied the Company’s motion to dismiss, and in February 2020, the court of appeals declined to exercise discretion to reverse the trial court’s decision. The Company filed a petition to review the trial court’s decision with the Texas Supreme Court, and the Court requested a response from the plaintiff. The Court subsequently requested full briefing on the merits of the case. The Company carries insurance for the claims asserted against it and the officer and director defendants, and the carrier has accepted coverage. The Company denies all allegations and intends to continue to defend this case vigorously. The Company does not expect this case to have a material adverse effect on the results of operations, financial position or cash flows of the Company after taking insurance into account. Additionally, it is not possible at this time to estimate the amount of any additional loss, or range of loss, that is reasonably possible. Indemnifications The Company has provided certain indemnifications to various third parties, including in relation to asset and entity dispositions, securities offerings and other financings, and litigation, such as the St. Lucie County Fire District Firefighters’ Pension Trust case described above. In the case of asset dispositions, these indemnifications typically relate to disputes, litigation or tax matters existing at the date of disposition. The Company likewise obtains indemnification for future matters when it sells assets, although there is no assurance the buyer will be capable of performing those obligations. In the case of equity offerings, these indemnifications typically relate to claims asserted against underwriters in connection with an offering. No material liabilities have been recognized in connection with these indemnifications.

INCOME TAXES

INCOME TAXES	3 Months Ended
	Mar. 31, 2021
Income Tax Expense (Benefit), Continuing Operations [Abstract]
INCOME TAXES	INCOME TAXES The Company’s effective tax rate was approximately 0% for the three months ended March 31, 2021. The effective tax rate for the three months ended March 31, 2021 related to the effects a valuation allowance against the Company’s U.S. deferred tax assets. A valuation allowance for deferred tax assets, including net operating losses, is recognized when it is more likely than not that some or all of the benefit from the deferred tax assets will not be realized. To assess that likelihood, the Company uses estimates and judgment regarding future taxable income, and considers the tax consequences in the jurisdiction where such taxable income is generated, to determine whether a valuation allowance is required. Such evidence can include current financial position, results of operations, both actual and forecasted, the reversal of deferred tax liabilities and tax planning strategies as well as current and forecasted business economics of the oil and gas industry. In the first quarter of 2020, due to significant pricing declines and the material write-down of the carrying value of the Company’s natural gas and oil properties in addition to other negative evidence, the Company concluded that it was more likely than not that these deferred tax assets will not be realized and recorded a discrete tax expense of $408 million for the increase in its valuation allowance. The net change in valuation allowance is reflected as a component of income tax expense. The Company also retained a valuation allowance of $87 million related to net operating losses in jurisdictions in which it no longer operates. Management will continue to assess available positive and negative evidence to estimate whether sufficient future taxable income will be generated to permit the use of deferred tax assets. The amount of the deferred tax asset considered realizable, however, could be adjusted based on changes in subjective estimates of future taxable income or if objective negative evidence is no longer present. The Company’s effective tax rate was approximately (36)% for the three months ended March 31, 2020. The effective tax rate for the three months ended March 31, 2020 was primarily the effect of recording the valuation allowance discussed above. The Company adopted Accounting Standards Update No. 2019-12 (“ASU 2019-12”) in the current period. ASU 2019-12 addressed simplification to income tax accounting rules, such as removing a few exceptions to intraperiod allocation. There was no material impact to the financial statements as a result of this adoption.

PENSION PLAN AND OTHER POSTRETI

PENSION PLAN AND OTHER POSTRETIREMENT BENEFITS	3 Months Ended
	Mar. 31, 2021
Retirement Benefits [Abstract]
PENSION PLAN AND OTHER POSTRETIREMENT BENEFITS	PENSION PLAN AND OTHER POSTRETIREMENT BENEFITS The Company maintains defined pension and other postretirement benefit plans, which cover substantially all of the Company’s employees. As part of ongoing effort to reduce costs, the Company elected to freeze its pension plan effective January 1, 2021. Employees that were participants in the pension plan prior to January 1, 2021 will continue to receive the interest component of the plan but will no longer receive the service component. Net periodic pension costs include the following components for the three months ended March 31, 2021 and 2020: Consolidated Statements of For the three months ended March 31, (in millions) 2021 2020 Service cost General and administrative expenses $ — $ 2 Interest cost Other Income (Loss), Net 1 1 Expected return on plan assets Other Income (Loss), Net (1) (1) Net periodic benefit cost $ — $ 2 The Company’s other postretirement benefit plan had a net periodic benefit cost of less than $1 million and $1 million for the three months ended March 31, 2021 and 2020, respectively. As of March 31, 2021, the Company has contributed $5 million to the pension and other postretirement benefit plans and expects to contribute an additional $7 million to its pension plan during the remainder of 2021. The Company recognized liabilities of $28 million and $13 million related to its pension and other postretirement benefits, respectively, as of March 31, 2021, compared to liabilities of $33 million and $13 million as of December 31, 2020, respectively.

LONG-TERM INCENTIVE COMPENSATIO

LONG-TERM INCENTIVE COMPENSATION	3 Months Ended
	Mar. 31, 2021
Share-based Payment Arrangement, Noncash Expense [Abstract]
LONG-TERM INCENTIVE COMPENSATION	LONG-TERM INCENTIVE COMPENSATION The Company’s long-term incentive compensation plans consist of a combination of stock-based awards that derive their value directly or indirectly from the Company’s common stock price, and cash-based awards that are fixed in amount but subject to meeting annual performance thresholds. Stock-Based Compensation The Company’s stock-based compensation is classified as either equity awards or liability awards in accordance with GAAP. The fair value of an equity-classified award is determined at the grant date and is amortized to general and administrative expense on a straight-line basis over the vesting period of the award. A portion of this general and administrative expense is capitalized into natural gas and oil properties, included in property and equipment. The fair value of a liability-classified award is determined on a quarterly basis beginning at the grant date until final vesting. Changes in the fair value of liability-classified awards are recorded to general and administrative expense and capitalized expense over the vesting period of the award. Generally, stock options granted to employees and directors vest ratably over three years from the grant date and expire seven years from the date of grant. The Company issues shares of restricted stock, restricted stock units or performance cash awards to employees and directors which generally vest over four years. Restricted stock, restricted stock units, performance cash awards and stock options granted to participants under the 2013 Incentive Plan, as amended and restated, immediately vest upon death, disability or retirement (subject to a minimum of three years of service). The Company issues performance unit awards to employees which historically have vested at or over three years. In February of 2021 and 2020, the Company notified employees of workforce reduction plans as a result of strategic realignments of the Company’s organizational structure. Theses reductions were substantially complete by the end of the first quarter of each respective year. Affected employees were offered a severance package which, if applicable, included the current value of unvested long-term incentive awards that were forfeited. The Company recognized the following amounts in total employee stock-based compensation costs for the three months ended March 31, 2021 and 2020: For the three months ended March 31, (in millions) 2021 2020 Stock-based compensation cost – expensed $ 13 $ — Stock-based compensation cost – capitalized 5 — Equity-Classified Awards The Company recognized the following amounts in employee equity-classified stock-based compensation costs for the three months ended March 31, 2021 and 2020: For the three months ended March 31, (in millions) 2021 2020 Equity-classified awards – expensed $ — $ 1 Equity-classified awards – capitalized — — As of March 31, 2021, there was less than $1 million of total unrecognized compensation cost related to the Company’s unvested equity-classified stock option grants, equity-classified restricted stock grants and equity-classified performance units. This cost is expected to be recognized over a weighted-average period of 1.0 year. Equity-Classified Stock Options The following table summarizes equity-classified stock option activity for the three months ended March 31, 2021 and provides information for options outstanding and options exercisable as of March 31, 2021: Number Weighted Average (in thousands) Outstanding at December 31, 2020 3,850 $ 13.39 Granted — $ — Exercised — $ — Forfeited or expired (61) $ 10.93 Outstanding at March 31, 2021 3,789 $ 13.43 Exercisable at March 31, 2021 3,789 $ 13.43 Equity-Classified Restricted Stock The following table summarizes equity-classified restricted stock activity for the three months ended March 31, 2021 and provides information for unvested shares as of March 31, 2021: Number Weighted Average (in thousands) Unvested shares at December 31, 2020 697 $ 5.97 Granted 10 $ 2.98 Vested (451) $ 7.61 Forfeited — $ 8.59 Unvested shares at March 31, 2021 256 $ 2.94 Equity-Classified Restricted Stock Units As a result of the Merger with Montage, certain employees became employees of Southwestern and retained their original equity awards. The following table summarizes equity-classified performance unit activity for the three months ended March 31, 2021 and provides information for unvested units as of March 31, 2021. Number Weighted Average (in thousands) Unvested units at December 31, 2020 134 $ 3.05 Granted — — Vested (45) 3.05 Forfeited — — Unvested Units at March 31, 2021 89 3.05 Liability-Classified Awards The Company recognized the following amounts in employee liability-classified stock-based compensation costs for the three months ended March 31, 2021: For the three months ended March 31, (in millions) 2021 2020 Liability-classified stock-based compensation cost – expensed $ 13 $ (1) Liability-classified stock-based compensation cost – capitalized 5 — Liability-Classified Restricted Stock Units In the first quarter of each year beginning with 2018, the Company granted restricted stock units that vest over a period of four years and are payable in either cash or shares at the option of the Compensation Committee of the Company’s Board of Directors. The awards granted in 2021 vest over a period of three years. The Company has accounted for these as liability-classified awards, and accordingly changes in the market value of the instruments will be recorded to general and administrative expense and capitalized expense over the vesting period of the award. As of March 31, 2021, there was $32 million of total unrecognized compensation cost related to liability-classified restricted stock units that is expected to be recognized over a weighted-average period of 2.2 years. The amount of unrecognized compensation cost for liability-classified awards will fluctuate over time as they are marked to market. Number Weighted Average (in thousands) Unvested units at December 31, 2020 11,613 $ 2.67 Granted 1,486 $ 4.23 Vested (4,522) $ 3.40 Forfeited (416) $ 4.31 Unvested units at March 31, 2021 8,161 $ 4.07 Liability-Classified Performance Units In each year beginning with 2018, the Company granted performance units that vest at the end of, or over, a three-year period and are payable in either cash or shares at the option of the Compensation Committee of the Company’s Board of Directors. The Company has accounted for these as liability-classified awards, and accordingly changes in the fair market value of the instruments will be recorded to general and administrative expense and capitalized expense over the vesting period of the awards. The performance unit awards granted in 2018 include a performance condition based on cash flow per debt-adjusted share and two market conditions, one based on absolute TSR and the other on relative TSR as compared to a group of the Company’s peers. The performance unit awards granted in 2019 include performance conditions based on return on average capital employed and two market conditions, one based on absolute TSR and the other on relative TSR. The performance units granted in 2020 include a performance condition based on return on average capital employed and a market condition based on relative TSR. In the first quarter of 2021, two types of performance unit awards were granted. One type of award includes a performance condition based on return on capital employed and a performance condition based on a reinvestment rate, and the second type of award includes one market condition based on relative TSR. The fair values of the market conditions are calculated by Monte Carlo models on a quarterly basis. As of March 31, 2021, there was $22 million of total unrecognized compensation cost related to liability-classified performance units. This cost is expected to be recognized over a weighted-average period of 2.1 years. The amount of unrecognized compensation cost for liability-classified awards will fluctuate over time as they are marked to market. The final value of the performance unit awards is contingent upon the Company’s actual performance against these performance measures. Number Weighted Average (in thousands) Unvested units at December 31, 2020 8,699 $ 2.57 Granted 3,580 $ 4.14 Vested (2,020) $ 4.05 Forfeited (622) $ 2.98 Unvested units at March 31, 2021 9,637 $ 2.88 Cash-Based Compensation Performance Cash Awards In 2021 and 2020, the Company granted performance cash awards that vest over a four-year period and are payable in cash on an annual basis. The value of each unit of the award equals one dollar. The Company recognizes the cost of these awards as general and administrative expense and capitalized expense over the vesting period of the awards. The performance cash awards granted in 2021 and 2020 include a performance condition determined annually by the Company. For both years, the performance measure is a targeted discretionary cash flow amount. If the Company, in its sole discretion, determines that the threshold was not met, the amount for that vesting period will not vest and will be cancelled. As of March 31, 2021, there was $30 million of total unrecognized compensation cost related to performance cash awards. This cost is expected to be recognized over a weighted average 3.5 years. The final value of the performance cash awards is contingent upon the Company’s actual performance against these performance measures. Number Weighted Average Fair Value (in thousands) Unvested units at December 31, 2020 18,353 $ 1.00 Granted 18,546 $ 1.00 Vested (4,319) $ 1.00 Forfeited (1,615) $ 1.00 Unvested units at March 31, 2021 30,965 $ 1.00

SEGMENT INFORMATION

SEGMENT INFORMATION	3 Months Ended
	Mar. 31, 2021
Segment Reporting [Abstract]
SEGMENT INFORMATION	SEGMENT INFORMATION The Company’s reportable business segments have been identified based on the differences in products or services provided. Revenues for the E&P segment are derived from the production and sale of natural gas and liquids. The Marketing segment generates revenue through the marketing of both Company and third-party produced natural gas and liquids volumes. Summarized financial information for the Company’s reportable segments is shown in the following table. The accounting policies of the segments are the same as those described in Note 1 of the Notes to Consolidated Financial Statements included in Item 8 of the 2020 Annual Report. Management evaluates the performance of its segments based on operating income, defined as operating revenues less operating costs. Income before income taxes, for the purpose of reconciling the operating income amount shown below to consolidated income before income taxes, is the sum of operating income, interest expense, gain (loss) on derivatives, gain on early extinguishment of debt and other income (loss). The “Other” column includes items not related to the Company’s reportable segments, including real estate and corporate items. Corporate general and administrative costs, depreciation expense and taxes, other than income taxes, are allocated to the segments. E&P Marketing Other Total Three months ended March 31, 2021 (in millions) Revenues from external customers $ 719 $ 353 $ — $ 1,072 Intersegment revenues (14) 644 — 630 Depreciation, depletion and amortization expense 94 2 — 96 Operating income 295 (1) 6 — 301 Interest expense (2) 31 — — 31 Loss on derivatives (191) — — (191) Other income, net 1 — — 1 Assets 4,741 (3) 396 110 5,247 Capital investments (4) 266 — — 266 Three months ended March 31, 2020 Revenues from external customers $ 353 $ 239 $ — $ 592 Intersegment revenues (9) 309 — 300 Depreciation, depletion and amortization expense 111 2 — 113 Impairments 1,479 — — 1,479 Operating loss (1,486) (1) (4) — (1,490) Interest expense (2) 19 — — 19 Gain on derivatives 339 — — 339 Gain on early extinguishment of debt — — 28 28 Other income, net 1 — — 1 Benefit from income taxes (2) 406 — — 406 Assets 4,900 (3) 214 161 5,275 Capital investments (4) 237 — — 237 (1) Operating income (loss) for the E&P segment includes $6 million and $10 million of restructuring charges for the three months ended March 31, 2021 and 2020, respectively. The E&P segment operating income (loss) also includes $1 million of merger-related charges for the three months ended March 31, 2021. (2) Interest expense and provision (benefit) for income taxes by segment is an allocation of corporate amounts as they are incurred at the corporate level. (3) E&P assets includes office, technology, water infrastructure, drilling rigs and other ancillary equipment not directly related to natural gas and oil properties. E&P assets also includes deferred tax assets which are an allocation of corporate amounts as they are incurred at the corporate level. (4) Capital investments include increases of $38 million and $8 million for the three months ended March 31, 2021 and 2020, respectively, relating to the change in accrued expenditures between periods. The following table presents the breakout of other assets, which represent corporate assets not allocated to segments and assets for non-reportable segments at March 31, 2021 and 2020: As of March 31, (in millions) 2021 2020 Cash and cash equivalents $ 4 $ 5 Income taxes receivable — 32 Prepayments 6 9 Property, plant and equipment 15 23 Unamortized debt expense 11 10 Right-of-use lease assets 70 77 Non-qualified retirement plan 4 5 $ 110 $ 161

NEW ACCOUNTING PRONOUNCEMENTS

NEW ACCOUNTING PRONOUNCEMENTS	3 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
NEW ACCOUNTING PRONOUNCEMENTS	NEW ACCOUNTING PRONOUNCEMENTS New Accounting Standards Implemented in this Report In August 2018, the Financial Accounting Standards Board (the “FASB”) issued ASU 2018-14, Disclosure Framework – Changes to the Disclosure Requirements for Defined Benefit Plans ("ASU 2018-14"). ASU 2018-14 amends, adds and removes certain disclosure requirements under FASB ASC Topic 715 – Compensation – Retirement Benefits. The guidance in ASU 2018-14 is effective for fiscal years beginning after December 15, 2020 and was adopted on January 1, 2021. Adoption of ASU 2018-14 will result in certain disclosure changes within the Company's footnote disclosures. The adoption of ASU 2018-14 did not have a material impact on the Company's consolidated financial statements. In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes. ASU 2019-12 eliminates certain exceptions to the guidance in Topic 740 related to the approach for intraperiod tax allocation, the methodology for calculating income taxes in an interim period, and the recognition of deferred tax liabilities for outside basis differences. The new guidance also clarifies certain aspects of the existing guidance, among other things. The standard became effective for interim and annual periods beginning after December 15, 2020 and shall be applied on either a prospective basis, a retrospective basis for all periods presented, or a modified retrospective basis through a cumulative-effect adjustment to retained earnings depending on which aspects of the new standard are applicable to an entity. The Company adopted the new standard on January 1, 2021 on a prospective basis, which did not have a material impact on its consolidated financial statements. New Accounting Standards Not Yet Adopted in this Report In March 2020, the FASB issued ASU 2020-04, Reference Rate Reform, as a new ASC Topic, ASC 848. The purpose of ASC 848 is to provide optional guidance to ease the potential effects on financial reporting of the market-wide migration away from Interbank Offered Rates, such as LIBOR, which is expected to be phased out at the end of calendar year 2021, to alternative reference rates. ASC 848 applies only to contracts, hedging relationships, debt arrangements and other transactions that reference a benchmark reference rate expected to be discontinued because of reference rate reform. ASC 848 contains optional expedients and exceptions for applying U.S. GAAP to transactions affected by this reform. The amendments in ASU 2020-04 are effective for all entities as of March 12, 2020 through December 31, 2022. The Company is currently assessing the impact of adopting this new guidance.

New Accounting Pronouncements (

New Accounting Pronouncements (Policies)	3 Months Ended
	Mar. 31, 2021
Accounting Policies [Abstract]
New Accounting Standards Implemented in this Report and New Accounting Standards Not Yet Adopted in this Report	New Accounting Standards Implemented in this Report In August 2018, the Financial Accounting Standards Board (the “FASB”) issued ASU 2018-14, Disclosure Framework – Changes to the Disclosure Requirements for Defined Benefit Plans ("ASU 2018-14"). ASU 2018-14 amends, adds and removes certain disclosure requirements under FASB ASC Topic 715 – Compensation – Retirement Benefits. The guidance in ASU 2018-14 is effective for fiscal years beginning after December 15, 2020 and was adopted on January 1, 2021. Adoption of ASU 2018-14 will result in certain disclosure changes within the Company's footnote disclosures. The adoption of ASU 2018-14 did not have a material impact on the Company's consolidated financial statements. In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes. ASU 2019-12 eliminates certain exceptions to the guidance in Topic 740 related to the approach for intraperiod tax allocation, the methodology for calculating income taxes in an interim period, and the recognition of deferred tax liabilities for outside basis differences. The new guidance also clarifies certain aspects of the existing guidance, among other things. The standard became effective for interim and annual periods beginning after December 15, 2020 and shall be applied on either a prospective basis, a retrospective basis for all periods presented, or a modified retrospective basis through a cumulative-effect adjustment to retained earnings depending on which aspects of the new standard are applicable to an entity. The Company adopted the new standard on January 1, 2021 on a prospective basis, which did not have a material impact on its consolidated financial statements. New Accounting Standards Not Yet Adopted in this Report In March 2020, the FASB issued ASU 2020-04, Reference Rate Reform, as a new ASC Topic, ASC 848. The purpose of ASC 848 is to provide optional guidance to ease the potential effects on financial reporting of the market-wide migration away from Interbank Offered Rates, such as LIBOR, which is expected to be phased out at the end of calendar year 2021, to alternative reference rates. ASC 848 applies only to contracts, hedging relationships, debt arrangements and other transactions that reference a benchmark reference rate expected to be discontinued because of reference rate reform. ASC 848 contains optional expedients and exceptions for applying U.S. GAAP to transactions affected by this reform. The amendments in ASU 2020-04 are effective for all entities as of March 12, 2020 through December 31, 2022. The Company is currently assessing the impact of adopting this new guidance.

ACQUISITION (Tables)

ACQUISITION (Tables)	3 Months Ended
	Mar. 31, 2021
Business Combinations [Abstract]
Schedule of Business Acquisitions by Acquisition, Equity Interest Issued or Issuable	The following table presents the fair value of consideration transferred to Montage stockholders as a result of the Merger: (in millions, except share, per share amounts) As of November 13, 2020 Shares of Southwestern common stock issued in respect of outstanding Montage common stock 67,311,166 Shares of Southwestern common stock issued in respect of Montage stock-based awards 2,429,682 69,740,848 NYSE closing price per share of Southwestern common shares on November 13, 2020 $ 3.05 Total consideration (fair value of Southwestern common shares issued) $ 213 Increase in Southwestern common stock ($0.01 par value per share) 1 Increase in Southwestern additional paid-in capital $ 212
Schedule of Business Acquisitions, by Acquisition	The following table sets forth the fair value of the assets acquired and liabilities assumed as of the acquisition date. Although the purchase price allocation is substantially complete as of the date of this filing, there may be further adjustments to the Company’s natural gas and oil properties as the studies necessary to determine the fair value are finalized. These amounts will be finalized no later than one year from the acquisition date. For the three months ended March 31, 2021 there were no changes to the allocation presented in the 2020 Form 10-K. (in millions) As of November 13, 2020 Consideration: Fair value of Southwestern’s stock issued on November 13, 2020 $ 213 Fair Value of Assets Acquired: Cash and cash equivalents 3 Accounts receivable 73 Other current assets 1 Commodity derivative assets 11 Evaluated oil and gas properties 1,012 Unevaluated oil and gas properties 90 Other property, plant and equipment 28 Other long-term assets 26 Total assets acquired 1,244 Fair Value of Liabilities Assumed: Accounts payable 145 Other current liabilities 49 Derivative liabilities 70 Revolving credit facility 200 Senior unsecured notes 522 Asset retirement obligations 28 Other noncurrent liabilities 17 Total liabilities assumed 1,031 Net Assets Acquired and Liabilities Assumed $ 213
Business Acquisition, Pro Forma Information	The following table presents selected unaudited pro forma condensed financial information for the three months ended March 31, 2020 as if the Merger had occurred on January 1, 2019: (in millions, except per share amounts) Pro forma results for the three months ended March 31, 2020 Revenues $ 725 Net income (loss) attributable to common stock $ (1,498)

Restructuring Charges (Tables)

Restructuring Charges (Tables)	3 Months Ended
	Mar. 31, 2021
Restructuring and Related Activities [Abstract]
Summary of Restructuring Charges	The following table presents a summary of the restructuring charges included in Operating Income (Loss) for the three months ended March 31, 2021 and 2020: For the three months ended March 31, (in millions) 2021 2020 Severance (including payroll taxes) (1) $ 6 $ 10 (1) Total restructuring charges were $6 million and $10 million for the Company’s E&P segment for the three months ended March 31, 2021 and March 31, 2020, respectively. The following table presents a reconciliation of the liability associated with the Company’s restructuring activities at March 31, 2021, which is reflected in accounts payable on the consolidated balance sheet: (in millions) Liability at December 31, 2020 $ 3 Additions 6 Distributions (9) Liability at March 31, 2021 $ —

Revenue Recognition (Tables)

Revenue Recognition (Tables)	3 Months Ended
	Mar. 31, 2021
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue by Segment	The following table reconciles operating revenues as presented on the consolidated statements of operations to the operating revenues by segment: (in millions) E&P Marketing Intersegment Total Three months ended March 31, 2021 Gas sales $ 451 $ — $ 13 $ 464 Oil sales 80 — 1 81 NGL sales 173 — — 173 Marketing — 996 (644) 352 Other (1) 1 1 — 2 Total $ 705 $ 997 $ (630) $ 1,072 Three months ended March 31, 2020 Gas sales $ 239 $ — $ 9 $ 248 Oil sales 52 — — 52 NGL sales 50 — — 50 Marketing — 548 (309) 239 Other (2) 3 — — 3 Total $ 344 $ 548 $ (300) $ 592 (1) For the three months ended March 31, 2021, other E&P revenues consists primarily of gains on purchaser imbalances associated with certain NGLs and other Marketing revenues consists primarily of sales of gas from storage. (2) For the three months ended March 31, 2020, other E&P revenues consists primarily of gains on purchaser imbalances associated with certain NGLs.
Disaggregation of Revenue on Geographic Basis	Associated E&P revenues are also disaggregated for analysis on a geographic basis by the core areas in which the Company operates, which are in Pennsylvania, West Virginia and Ohio. For the three months ended March 31, (in millions) 2021 2020 Northeast Appalachia $ 263 $ 195 Southwest Appalachia 441 149 Other 1 — Total $ 705 $ 344
Reconciliation of Accounts Receivable	The following table reconciles the Company’s receivables from contracts with customers to consolidated accounts receivable as presented on the consolidated balance sheet: (in millions) March 31, 2021 December 31, 2020 Receivables from contracts with customers $ 381 $ 350 Other accounts receivable 19 18 Total accounts receivable $ 400 $ 368

Cash and Cash Equivalents (Tabl

Cash and Cash Equivalents (Tables)	3 Months Ended
	Mar. 31, 2021
Cash and Cash Equivalents [Abstract]
Summary of Cash and Cash Equivalents	The following table presents a summary of cash and cash equivalents as of March 31, 2021 and December 31, 2020: (in millions) March 31, 2021 December 31, 2020 Cash $ 4 $ 13 Marketable securities (1) — — Total $ 4 $ 13 (1) Typically consists of government stable value money market funds.

Natural Gas and Oil Properties

Natural Gas and Oil Properties (Tables)	3 Months Ended
	Mar. 31, 2021
Oil and Gas Exploration and Production Industries Disclosures [Abstract]
Oil and Gas Exploration and Production Industries Disclosures	Prices used to calculate the ceiling value of reserves were as follows: March 31, 2021 March 31, 2020 Natural gas (per MMBtu) $ 2.16 $ 2.30 Oil (per Bbl) $ 40.01 $ 55.77 NGLs (per Bbl) $ 13.57 $ 9.96

Earnings Per Share (Tables)

Earnings Per Share (Tables)	3 Months Ended
	Mar. 31, 2021
Earnings Per Share [Abstract]
Schedule of Earnings Per Share	The following table presents the computation of earnings per share for the three months ended March 31, 2021 and 2020: For the three months ended March 31, (in millions, except share/per share amounts) 2021 2020 Net income (loss) $ 80 $ (1,547) Number of common shares: Weighted average outstanding 675,385,145 540,308,491 Issued upon assumed exercise of outstanding stock options — — Effect of issuance of non-vested restricted common stock 870,541 — Effect of issuance of non-vested restricted units 804,944 — Effect of issuance of non-vested performance units 2,807,195 — Weighted average and potential dilutive outstanding 679,867,825 540,308,491 Earnings per common share Basic $ 0.12 $ (2.86) Diluted $ 0.12 $ (2.86)
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	The following table presents the common stock shares equivalent excluded from the calculation of diluted earnings per share for the three months ended March 31, 2021 and 2020, as they would have had an antidilutive effect: For the three months ended March 31, 2021 2020 Unexercised stock options 3,795,091 4,584,563 Unvested share-based payment — 1,006,860 Restricted stock units 3,987,291 1,312,293 Performance units — 2,275,498 Total 7,782,382 9,179,214

Derivatives and Risk Manageme_2

Derivatives and Risk Management (Tables)	3 Months Ended
	Mar. 31, 2021
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Derivative Instruments Notional Amount, Weighted Average Contract Prices and Fair Value	The following tables provide information about the Company’s financial instruments that are sensitive to changes in commodity prices and that are used to protect the Company’s exposure. None of the financial instruments below are designated for hedge accounting treatment. The tables present the notional amount, the weighted average contract prices and the fair value by expected maturity dates as of March 31, 2021: Financial Protection on Production Weighted Average Price per MMBtu Volume (Bcf) Swaps Sold Puts Purchased Puts Sold Calls Basis Differential Fair Value at March 31, 2021 (in millions) Natural Gas 2021 Fixed price swaps 176 $ 2.79 $ — $ — $ — $ — $ 14 Two-way costless collars 195 — — 2.57 2.93 — 1 Three-way costless collars 218 — 2.17 2.50 2.84 — (23) Total 589 $ (8) 2022 Fixed price swaps 112 $ 2.68 $ — $ — $ — $ — $ (2) Two-way costless collars 63 — — 2.52 3.03 — (3) Three-way costless collars 278 — 2.06 2.50 2.97 — (13) Total 453 $ (18) 2023 Three-way costless collars 103 $ — $ 2.05 $ 2.46 $ 3.01 $ — $ (4) Basis Swaps 2021 233 $ — $ — $ — $ — $ (0.49) $ 39 2022 220 — — — — (0.44) 24 2023 119 — — — — (0.56) 4 2024 24 — — — — (0.64) 1 2025 9 — — — — (0.64) — Total 605 $ 68 Volume (MBbls) Weighted Average Strike Price per Bbl Fair Value at March 31, 2021 (in millions) Swaps Sold Puts Purchased Puts Sold Calls Oil 2021 Fixed price swaps 3,272 $ 49.27 $ — $ — $ — $ (29) Two-way costless collars 156 — — 37.79 45.73 (2) Three-way costless collars 1,498 — 37.86 47.70 53.10 (10) Total 4,926 $ (41) 2022 Fixed price swaps 1,719 $ 48.54 $ — $ — $ — $ (10) Three-way costless collars 1,380 — 39.89 50.23 57.05 (4) Total 3,099 $ (14) 2023 Three-way costless collars 1,268 $ — $ 33.97 $ 45.51 $ 56.12 $ (4) Ethane 2021 Fixed price swaps 4,429 $ 7.17 $ — $ — $ — $ (11) Two-way costless collars 440 — — 7.14 10.40 — Total 4,869 $ (11) 2022 Fixed price swaps 1,758 $ 8.68 $ — $ — $ — $ (1) Two-way costless collars 135 — — 7.56 9.66 — Total 1,893 $ (1) Propane 2021 Fixed price swaps 5,443 $ 20.84 $ — $ — $ — $ (69) 2022 Fixed price swaps 2,723 $ 21.83 $ — $ — $ — $ (14) Three-way costless collars 305 — 16.80 21.00 31.92 (1) Total 3,028 (15) Normal Butane 2021 Fixed price swaps 1,568 $ 25.30 $ — $ — $ — $ (19) 2022 Fixed price swaps 888 $ 24.47 $ — $ — $ — $ (5) Natural Gasoline 2021 Fixed price swaps 1,513 $ 37.91 $ — $ — $ — $ (27) 2022 Fixed price swaps 857 $ 40.48 $ — $ — $ — $ (8) Other Derivative Contracts Volume (Bcf) Weighted Average Strike Price per MMBtu Fair Value at March 31, 2021 (in millions) Call Options – Natural Gas (Net) 2021 57 $ 3.19 $ (4) 2022 77 3.00 (16) 2023 46 2.94 (10) 2024 9 3.00 (3) Total 189 $ (33) Put Options – Natural Gas 2021 14 $ 2.00 $ — 2022 5 2.00 (1) Total 19 $ (1) Volume (MBbls) Weighted Average Strike Price per Bbl Fair Value at March 31, 2021 (in millions) Call Options – Oil 2021 171 $ 60.00 $ (1) Volume (Bcf) Weighted Average Strike Price per MMBtu Fair Value at March 31, 2021 (in millions) Swaptions – Natural Gas 2021 (1) 18 $ 3.00 $ (1) (1) The Company has sold swaptions with an underlying tenor of January 2022 to December 2022, with an exercise date of December 23, 2021. Volume (Bcf) Weighted Average Strike Price per MMBtu Fair Value at March 31, 2021 (in millions) Swaps Basis Differential Storage (1) 2021 Purchased fixed price swaps 2 $ 2.34 $ — $ — Purchased basis swaps 1 — (0.88) — Fixed price swaps — 2.23 — — Basis swaps — — (0.57) — Total 3 $ — 2022 Purchased fixed price swaps — $ 2.14 $ — $ — Fixed price swaps 2 2.82 — — Basis swaps 1 — (0.57) — Total 3 $ — (1) The Company has entered into certain derivatives to protect the value of volumes of natural gas injected into a storage facility that will be withdrawn and sold at a later date. Purchased Fixed Price Swaps – Marketing (Natural Gas) (1) Volume (Bcf) Weighted Average Strike Price per MMBtu Fair Value at March 31, 2021 (in millions) 2021 4 2.44 1 (1) The Company has entered into a limited number of derivatives to protect the value of certain long-term sales contracts.
Balance Sheet Classification of Derivative Financial Instruments	The balance sheet classification of the assets and liabilities related to derivative financial instruments (none of which are designated for hedge accounting treatment) is summarized below as of March 31, 2021 and December 31, 2020: Derivative Assets Fair Value (in millions) Balance Sheet Classification March 31, 2021 December 31, 2020 Derivatives not designated as hedging instruments: Purchased fixed price swaps – natural gas Derivative assets $ 1 $ 1 Fixed price swaps – natural gas Derivative assets 25 37 Fixed price swaps – oil Derivative assets — 13 Two-way costless collars – natural gas Derivative assets 39 54 Three-way costless collars – natural gas Derivative assets 39 57 Three-way costless collars – oil Derivative assets 6 15 Basis swaps – natural gas Derivative assets 46 60 Call options – natural gas Derivative assets 1 4 Fixed price swaps – natural gas Other long-term assets — 7 Fixed price swaps – oil Other long-term assets — 2 Fixed price swaps – propane Other long-term assets 1 — Two-way costless collars – natural gas Other long-term assets 2 20 Three-way costless collars – natural gas Other long-term assets 82 87 Three-way costless collars – oil Other long-term assets 14 15 Basis swaps – natural gas Other long-term assets 39 15 Interest rate swaps Other long-term assets 1 — Total derivative assets $ 296 $ 387 Derivative Liabilities Fair Value (in millions) Balance Sheet Classification March 31, 2021 December 31, 2020 Derivatives not designated as hedging instruments: Fixed price swaps – natural gas Derivative liabilities $ 12 $ 7 Fixed price swaps – oil Derivative liabilities 32 12 Fixed price swaps – ethane Derivative liabilities 11 10 Fixed price swaps – propane Derivative liabilities 76 36 Fixed price swaps – normal butane Derivative liabilities 21 8 Fixed price swaps – natural gasoline Derivative liabilities 30 13 Two-way costless collars – natural gas Derivative liabilities 39 43 Two-way costless collars – oil Derivative liabilities 2 1 Three-way costless collars – natural gas Derivative liabilities 73 82 Three-way costless collars – oil Derivative liabilities 17 15 Basis swaps – natural gas Derivative liabilities 9 3 Call options – natural gas Derivative liabilities 13 12 Call options – oil Derivative liabilities 1 — Put options – natural gas Derivative liabilities 1 1 Swaptions – natural gas Derivative liabilities 1 2 Fixed price swaps – natural gas Long-term derivative liabilities 1 3 Fixed price swaps – oil Long-term derivative liabilities 7 2 Fixed price swaps – ethane Long-term derivative liabilities 1 — Fixed price swaps – propane Long-term derivative liabilities 8 2 Fixed price swaps – normal butane Long-term derivative liabilities 3 1 Fixed price swaps – natural gasoline Long-term derivative liabilities 5 2 Two-way costless collars – natural gas Long-term derivative liabilities 4 21 Three-way costless collars – natural gas Long-term derivative liabilities 88 102 Three-way costless collars – oil Long-term derivative liabilities 21 15 Three-way costless collars – propane Long-term derivative liabilities 1 — Basis swap – natural gas Long-term derivative liabilities 8 7 Call options – natural gas Long-term derivative liabilities 21 28 Total derivative liabilities $ 506 $ 428
Summary of Before Tax Effect of Fair Value Hedges not Designated for Hedge Accounting	The following tables summarize the before-tax effect of the Company’s derivative instruments on the consolidated statements of operations for the three months ended March 31, 2021 and 2020: Unsettled Gain (Loss) on Derivatives Recognized in Earnings Consolidated statement of Operations Classification of Gain (Loss) on Derivatives, Unsettled For the three months ended March 31, Derivative Instrument 2021 2020 (in millions) Purchased fixed price swaps – natural gas Gain (Loss) on Derivatives $ — $ (1) Purchased fixed price swaps – oil Gain (Loss) on Derivatives — (5) Fixed price swaps – natural gas Gain (Loss) on Derivatives (22) 103 Fixed price swaps – oil Gain (Loss) on Derivatives (40) 118 Fixed price swaps – ethane Gain (Loss) on Derivatives (2) 12 Fixed price swaps – propane Gain (Loss) on Derivatives (45) 36 Fixed price swaps – normal butane Gain (Loss) on Derivatives (15) — Fixed price swaps – natural gasoline Gain (Loss) on Derivatives (20) — Two-way costless collars – natural gas Gain (Loss) on Derivatives (12) (4) Two-way costless collars – oil Gain (Loss) on Derivatives (1) 19 Two-way costless collars – propane Gain (Loss) on Derivatives — 2 Three-way costless collars – natural gas Gain (Loss) on Derivatives — (51) Three-way costless collars – oil Gain (Loss) on Derivatives (18) 25 Three-way costless collars – propane Gain (Loss) on Derivatives (1) — Basis swaps – natural gas Gain (Loss) on Derivatives 3 (1) Call options – natural gas Gain (Loss) on Derivatives 3 (5) Call options – oil Gain (Loss) on Derivatives (1) 1 Swaptions – natural gas Gain (Loss) on Derivatives 1 — Purchased fixed price swap – natural gas storage Gain (Loss) on Derivatives — (1) Fixed price swap – natural gas storage Gain (Loss) on Derivatives — (1) Interest rate swaps Gain (Loss) on Derivatives 1 (1) Total gain (loss) on unsettled derivatives $ (169) $ 246 Settled Gain (Loss) on Derivatives Recognized in Earnings (1) Consolidated statement of Operations Classification of Gain (Loss) on Derivatives, Settled For the three months ended March 31, Derivative Instrument 2021 2020 (in millions) Purchased fixed price swaps – natural gas Gain (Loss) on Derivatives $ — $ (1) Fixed price swaps – natural gas Gain (Loss) on Derivatives 5 5 Fixed price swaps – oil Gain (Loss) on Derivatives (17) 9 Fixed price swaps – ethane Gain (Loss) on Derivatives (4) 6 Fixed price swaps – propane Gain (Loss) on Derivatives (30) 10 Fixed price swaps – normal butane Gain (Loss) on Derivatives (7) — Fixed price swaps – natural gasoline Gain (Loss) on Derivatives (9) — Two-way costless collars – natural gas Gain (Loss) on Derivatives 2 6 Two-way costless collars – oil Gain (Loss) on Derivatives (1) 3 Two-way costless collars – propane Gain (Loss) on Derivatives — 1 Three-way costless collars – natural gas Gain (Loss) on Derivatives 1 36 Three-way costless collars – oil Gain (Loss) on Derivatives (1) 1 Basis swaps – natural gas Gain (Loss) on Derivatives 41 16 Put options – natural gas Gain (Loss) on Derivatives (2) (2) — Fixed price swaps – natural gas storage Gain (Loss) on Derivatives — 1 Total gain (loss) on settled derivatives $ (22) $ 93 Total gain (loss) on derivatives $ (191) $ 339 (1) The Company calculates gain (loss) on derivatives, settled, as the summation of gains and losses on positions that settled within the period.

Reclassifications from Accumu_2

Reclassifications from Accumulated Other Comprehensive Income (Loss) (Tables)	3 Months Ended
	Mar. 31, 2021
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Components of Accumulated Other Comprehensive Income (Loss)	The following tables detail the components of accumulated other comprehensive income and the related tax effects for the three months ended March 31, 2021: (in millions) Pension and Other Postretirement Foreign Currency Total Beginning balance December 31, 2020 $ (24) $ (14) $ (38) Other comprehensive income before reclassifications — — — Amounts reclassified from other comprehensive income (1) — — — Net current-period other comprehensive income — — — Ending balance March 31, 2021 $ (24) $ (14) $ (38)
Reclassification out of Accumulated Other Comprehensive Income	Details about Accumulated Other Comprehensive Income Affected Line Item in the Consolidated Statement of Operations Amount Reclassified from Accumulated Other Comprehensive Income For the three months ended (in millions) Pension and other postretirement: Amortization of prior service cost and net gain (1) Other Income, Net $ — Provision (Benefit) for Income Taxes — Net Income (Loss) $ — Total reclassifications for the period Net Income (Loss) $ — (1) For the three months ended March 31, 2021, the amount reclassified from accumulated other comprehensive income was immaterial. See Note 14 for additional details regarding the Company’s pension and other postretirement benefit plans.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2021
Fair Value Disclosures [Abstract]
Carrying Amount and Estimated Fair Values of Financial Instruments	The carrying amounts and estimated fair values of the Company’s financial instruments as of March 31, 2021 and December 31, 2020 were as follows: March 31, 2021 December 31, 2020 (in millions) Carrying Fair Carrying Fair Cash and cash equivalents $ 4 $ 4 $ 13 $ 13 2018 revolving credit facility due April 2024 567 567 700 700 Senior notes (1) 2,471 2,640 2,471 2,609 Derivative instruments, net (210) (210) (41) (41) (1) Excludes unamortized debt issuance costs and debt discounts.
Summary of Assets and Liabilities Measured at Fair Value on Recurring Basis	Assets and liabilities measured at fair value on a recurring basis are summarized below: March 31, 2021 Fair Value Measurements Using: (in millions) Quoted Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets (Liabilities) at Fair Value Assets Purchased fixed price swaps $ — $ 1 $ — $ 1 Fixed price swaps — 26 — 26 Two-way costless collars — 41 — 41 Three-way costless collars — 141 — 141 Basis swaps — 85 — 85 Call options — 1 — 1 Interest rate swap — 1 — 1 Liabilities Fixed price swaps — (207) — (207) Two-way costless collars — (45) — (45) Three-way costless collars — (200) — (200) Basis swaps — (17) — (17) Call options — (35) — (35) Put options — (1) — (1) Swaptions — (1) — (1) Total (1) $ — $ (210) $ — $ (210) (1) Includes a net reduction to the liability fair value of less than $1 million related to estimated nonperformance risk. December 31, 2020 Fair Value Measurements Using: (in millions) Quoted Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets (Liabilities) at Fair Value Assets Purchased fixed price swaps $ — $ 1 $ — $ 1 Fixed price swaps — 59 — 59 Two-way costless collars — 74 — 74 Three-way costless collars — 174 — 174 Basis swaps — 75 — 75 Call options — 4 — 4 Liabilities Fixed price swaps — (96) — (96) Two-way costless collars — (65) — (65) Three-way costless collars — (214) — (214) Basis swaps — (10) — (10) Call options — (40) — (40) Put options — (1) — (1) Swaptions — (2) — (2) Total (1) $ — $ (41) $ — $ (41) (1) Includes a net reduction to the liability fair value of $1 million related to estimated nonperformance risk.

Debt (Tables)

Debt (Tables)	3 Months Ended
	Mar. 31, 2021
Debt Disclosure [Abstract]
Components of Debt	The components of debt as of March 31, 2021 and December 31, 2020 consisted of the following: March 31, 2021 (in millions) Debt Instrument Unamortized Issuance Expense Unamortized Debt Discount Total Current portion of long-term debt: 4.10% Senior Notes due March 2022 $ 207 $ — $ — $ 207 Total current portion of long-term debt $ 207 $ — $ — $ 207 Long-term debt: Variable rate (2.09% at March 31, 2021) 2018 revolving credit facility due April 2024 $ 567 $ — (1) $ — $ 567 4.95% Senior Notes due January 2025 (2) 856 (4) (1) 851 7.50% Senior Notes due April 2026 618 (5) — 613 7.75% Senior Notes due October 2027 440 (4) — 436 8.375% Senior Notes due September 2028 350 (5) — 345 Total long-term debt $ 2,831 $ (18) $ (1) $ 2,812 Total debt $ 3,038 $ (18) $ (1) $ 3,019 December 31, 2020 (in millions) Debt Instrument Unamortized Issuance Expense Unamortized Debt Discount Total Long-term debt: Variable rate (2.11% at December 31, 2020) 2018 term loan facility due April 2024 $ 700 $ — (1) $ — $ 700 4.10% Senior Notes due March 2022 207 — — 207 4.95% Senior Notes due January 2025 (2) 856 (4) (1) 851 7.50% Senior Notes due April 2026 618 (6) — 612 7.75% Senior Notes due October 2027 440 (5) — 435 8.375% Senior Notes due September 2028 350 (5) — 345 Total long-term debt $ 3,171 $ (20) $ (1) $ 3,150 (1) At March 31, 2021 and December 31, 2020, unamortized issuance expense of $11 million and $12 million, respectively, associated with the 2018 credit facility (as defined below) was classified as other long-term assets on the consolidated balance sheets. (2) Effective in July 2018, the interest rate was 6.20% for the 2025 Notes, reflecting a net downgrade in the Company’s bond ratings since the initial offering. On April 7, 2020, S&P downgraded the Company’s bond rating to BB-, which had the effect of increasing the interest rate on the 2025 Notes to 6.45% following the July 23, 2020 interest payment date. The first coupon payment to the bondholders at the higher interest rate was paid in January 2021.
Schedule of Maturities of Long-term Debt	The following is a summary of scheduled debt maturities by year as of March 31, 2021: (in millions) 2021 $ — 2022 207 2023 — 2024 567 2025 856 Thereafter 1,408 $ 3,038 (1) The Company’s current revolving credit facility matures in 2024.

Commitments and Contingencies (

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Schedule of Future Obligation under Transportation Agreements	As of March 31, 2021, future payments under non-cancelable firm transportation and gathering agreements were as follows: Payments Due by Period (in millions) Total Less than 1 1 to 3 Years 3 to 5 Years 5 to 8 Years More than 8 Infrastructure currently in service $ 7,915 $ 789 $ 1,539 $ 1,295 $ 1,752 $ 2,540 Pending regulatory approval and/or construction (1) 436 2 30 38 81 285 Total transportation charges $ 8,351 $ 791 $ 1,569 $ 1,333 $ 1,833 $ 2,825 (1) Based on estimated in-service dates as of March 31, 2021.

Pension Plan and Other Postre_2

Pension Plan and Other Postretirement Benefits (Tables)	3 Months Ended
	Mar. 31, 2021
Retirement Benefits [Abstract]
Pension and Other Postretirement Benefit Costs	The Company maintains defined pension and other postretirement benefit plans, which cover substantially all of the Company’s employees. As part of ongoing effort to reduce costs, the Company elected to freeze its pension plan effective January 1, 2021. Employees that were participants in the pension plan prior to January 1, 2021 will continue to receive the interest component of the plan but will no longer receive the service component. Net periodic pension costs include the following components for the three months ended March 31, 2021 and 2020: Consolidated Statements of For the three months ended March 31, (in millions) 2021 2020 Service cost General and administrative expenses $ — $ 2 Interest cost Other Income (Loss), Net 1 1 Expected return on plan assets Other Income (Loss), Net (1) (1) Net periodic benefit cost $ — $ 2

Long-term Incentive Compensat_2

Long-term Incentive Compensation (Tables)	3 Months Ended
	Mar. 31, 2021
Share-based Payment Arrangement, Noncash Expense [Abstract]
Schedule of Stock-Based Compensation Costs	The Company recognized the following amounts in total employee stock-based compensation costs for the three months ended March 31, 2021 and 2020: For the three months ended March 31, (in millions) 2021 2020 Stock-based compensation cost – expensed $ 13 $ — Stock-based compensation cost – capitalized 5 —
Schedule of Equity-Classified Stock-Based Compensation Costs	The Company recognized the following amounts in employee equity-classified stock-based compensation costs for the three months ended March 31, 2021 and 2020: For the three months ended March 31, (in millions) 2021 2020 Equity-classified awards – expensed $ — $ 1 Equity-classified awards – capitalized — —
Summary of Equity-Classified Stock Option Activity	The following table summarizes equity-classified stock option activity for the three months ended March 31, 2021 and provides information for options outstanding and options exercisable as of March 31, 2021: Number Weighted Average (in thousands) Outstanding at December 31, 2020 3,850 $ 13.39 Granted — $ — Exercised — $ — Forfeited or expired (61) $ 10.93 Outstanding at March 31, 2021 3,789 $ 13.43 Exercisable at March 31, 2021 3,789 $ 13.43
Summary of Equity-Classified Restricted Stock Activity	The following table summarizes equity-classified restricted stock activity for the three months ended March 31, 2021 and provides information for unvested shares as of March 31, 2021: Number Weighted Average (in thousands) Unvested shares at December 31, 2020 697 $ 5.97 Granted 10 $ 2.98 Vested (451) $ 7.61 Forfeited — $ 8.59 Unvested shares at March 31, 2021 256 $ 2.94
Summary of Equity-Classified Performance Units Activity	The following table summarizes equity-classified performance unit activity for the three months ended March 31, 2021 and provides information for unvested units as of March 31, 2021. Number Weighted Average (in thousands) Unvested units at December 31, 2020 134 $ 3.05 Granted — — Vested (45) 3.05 Forfeited — — Unvested Units at March 31, 2021 89 3.05
Schedule of Liability-Classified Stock-Based Compensation Costs	The Company recognized the following amounts in employee liability-classified stock-based compensation costs for the three months ended March 31, 2021: For the three months ended March 31, (in millions) 2021 2020 Liability-classified stock-based compensation cost – expensed $ 13 $ (1) Liability-classified stock-based compensation cost – capitalized 5 —
Summary of Liability-Classified Restricted Stock Unit Activity	As of March 31, 2021, there was $32 million of total unrecognized compensation cost related to liability-classified restricted stock units that is expected to be recognized over a weighted-average period of 2.2 years. The amount of unrecognized compensation cost for liability-classified awards will fluctuate over time as they are marked to market. Number Weighted Average (in thousands) Unvested units at December 31, 2020 11,613 $ 2.67 Granted 1,486 $ 4.23 Vested (4,522) $ 3.40 Forfeited (416) $ 4.31 Unvested units at March 31, 2021 8,161 $ 4.07
Summary of Liability-Classified Performance Unit Activity	Number Weighted Average (in thousands) Unvested units at December 31, 2020 8,699 $ 2.57 Granted 3,580 $ 4.14 Vested (2,020) $ 4.05 Forfeited (622) $ 2.98 Unvested units at March 31, 2021 9,637 $ 2.88
Summary of Liability-Classified Performance Unit Activity	Number Weighted Average Fair Value (in thousands) Unvested units at December 31, 2020 18,353 $ 1.00 Granted 18,546 $ 1.00 Vested (4,319) $ 1.00 Forfeited (1,615) $ 1.00 Unvested units at March 31, 2021 30,965 $ 1.00

Segment Information (Tables)

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2021
Segment Reporting [Abstract]
Summary of Financial Information for Company's Reportable Segments	Summarized financial information for the Company’s reportable segments is shown in the following table. The accounting policies of the segments are the same as those described in Note 1 of the Notes to Consolidated Financial Statements included in Item 8 of the 2020 Annual Report. Management evaluates the performance of its segments based on operating income, defined as operating revenues less operating costs. Income before income taxes, for the purpose of reconciling the operating income amount shown below to consolidated income before income taxes, is the sum of operating income, interest expense, gain (loss) on derivatives, gain on early extinguishment of debt and other income (loss). The “Other” column includes items not related to the Company’s reportable segments, including real estate and corporate items. Corporate general and administrative costs, depreciation expense and taxes, other than income taxes, are allocated to the segments. E&P Marketing Other Total Three months ended March 31, 2021 (in millions) Revenues from external customers $ 719 $ 353 $ — $ 1,072 Intersegment revenues (14) 644 — 630 Depreciation, depletion and amortization expense 94 2 — 96 Operating income 295 (1) 6 — 301 Interest expense (2) 31 — — 31 Loss on derivatives (191) — — (191) Other income, net 1 — — 1 Assets 4,741 (3) 396 110 5,247 Capital investments (4) 266 — — 266 Three months ended March 31, 2020 Revenues from external customers $ 353 $ 239 $ — $ 592 Intersegment revenues (9) 309 — 300 Depreciation, depletion and amortization expense 111 2 — 113 Impairments 1,479 — — 1,479 Operating loss (1,486) (1) (4) — (1,490) Interest expense (2) 19 — — 19 Gain on derivatives 339 — — 339 Gain on early extinguishment of debt — — 28 28 Other income, net 1 — — 1 Benefit from income taxes (2) 406 — — 406 Assets 4,900 (3) 214 161 5,275 Capital investments (4) 237 — — 237 (1) Operating income (loss) for the E&P segment includes $6 million and $10 million of restructuring charges for the three months ended March 31, 2021 and 2020, respectively. The E&P segment operating income (loss) also includes $1 million of merger-related charges for the three months ended March 31, 2021. (2) Interest expense and provision (benefit) for income taxes by segment is an allocation of corporate amounts as they are incurred at the corporate level. (3) E&P assets includes office, technology, water infrastructure, drilling rigs and other ancillary equipment not directly related to natural gas and oil properties. E&P assets also includes deferred tax assets which are an allocation of corporate amounts as they are incurred at the corporate level. (4) Capital investments include increases of $38 million and $8 million for the three months ended March 31, 2021 and 2020, respectively, relating to the change in accrued expenditures between periods. The following table presents the breakout of other assets, which represent corporate assets not allocated to segments and assets for non-reportable segments at March 31, 2021 and 2020: As of March 31, (in millions) 2021 2020 Cash and cash equivalents $ 4 $ 5 Income taxes receivable — 32 Prepayments 6 9 Property, plant and equipment 15 23 Unamortized debt expense 11 10 Right-of-use lease assets 70 77 Non-qualified retirement plan 4 5 $ 110 $ 161

Basis of Presentation (Narrativ

Basis of Presentation (Narrative) (Details)	3 Months Ended
	Mar. 31, 2021segment
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of segments	2

ACQUISITION (Narrative) (Detail

ACQUISITION (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	Nov. 13, 2020	Aug. 31, 2020	Mar. 31, 2021	Dec. 31, 2020
Montage Resources Corporation
Business Acquisition [Line Items]
Number of Southwestern Energy common stock for each share of Montage Resources Corporation common stock converted (in shares)	1.8656
Offering price (in dollars per share)	$ 3.05
Percentage of voting interest	90.00%
Revenues associated with the operations acquired through the Merger			$ 130
Net income attributable to common stockholders associated with the operations acquired through the Merger			61
Employee severance and related costs			$ 1
Montage Resources Corporation | Public Stock Offering
Business Acquisition [Line Items]
Offering price (in dollars per share)		$ 2.50
Underwritten public offering of common stock (in shares)		63,250,000
Net proceeds from public offering		$ 152
Montage Resources Corporation | Montage Resources Corporation
Business Acquisition [Line Items]
Percentage of voting interest	10.00%
Senior Notes | 8.375% Senior Notes due September 2028
Business Acquisition [Line Items]
Senior notes		$ 350
Stated interest rate		8.375%	8.375%	8.375%
Senior Notes | Montage Resources Corporation | Eight Point Eight Seven Five Percent Senior Notes Due 2023
Business Acquisition [Line Items]
Senior notes		$ 510
Stated interest rate		8.875%
Senior Notes | Montage Resources Corporation | 8.375% Senior Notes due September 2028
Business Acquisition [Line Items]
Senior notes		$ 350
Stated interest rate		8.375%

ACQUISITION - (Schedule of cons

ACQUISITION - (Schedule of consideration Paid to Stockholders of Montage) (Details) - USD ($) $ / shares in Units, $ in Millions	Nov. 13, 2020	Mar. 31, 2021	Dec. 31, 2020
Business Acquisition, Equity Interests Issued or Issuable [Line Items]
Common stock, par value (in dollars per shares)	$ 0.01	$ 0.01	$ 0.01
Montage Resources Corporation
Business Acquisition, Equity Interests Issued or Issuable [Line Items]
Shares of Southwestern common stock issued in respect of outstanding Montage common stock	67,311,166
Shares of Southwestern common stock issued in respect of Montage stock-based awards	2,429,682
Shares of Southwestern common stock issued during Merger	69,740,848
NYSE closing price per share of Southwestern common shares on November 13, 2020 (in dollars per share)	$ 3.05
Total consideration (fair value of Southwestern common shares issued)	$ 213
Montage Resources Corporation | Additional Paid-In Capital
Business Acquisition, Equity Interests Issued or Issuable [Line Items]
Montage merger exchange	212
Montage Resources Corporation | Common Stock
Business Acquisition, Equity Interests Issued or Issuable [Line Items]
Montage merger exchange	$ 1

ACQUISITION - (Schedule of the

ACQUISITION - (Schedule of the Allocation of Purchase Price) (Details) - Montage Resources Corporation $ in Millions	Nov. 13, 2020USD ($)
Consideration:
Fair value of Southwestern’s stock issued on November 13, 2020	$ 213
Cash and cash equivalents	3
Accounts receivable	73
Other current assets	1
Derivative assets	11
Evaluated natural gas and oil properties	1,012
Unevaluated natural gas and oil properties	90
Other property, plant and equipment	28
Other long-term assets	26
Total assets acquired	1,244
Accounts payable	145
Other current liabilities	49
Derivative liabilities	70
Revolving credit facility	200
Senior unsecured notes	522
Asset retirement obligations	28
Other long-term liabilities	17
Total liabilities assumed	1,031
Net assets acquired and liabilities assumed	$ 213

ACQUISITION - (Schedule of Pro

ACQUISITION - (Schedule of Pro Forma) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2020USD ($)
Pro forma results for the three months ended March 31, 2020
Revenues	$ 725
Net income (loss) attributable to common stock	$ (1,498)

Restructuring Charges (Summary

Restructuring Charges (Summary of Restructuring Charges) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 6	$ 10
E&P
Restructuring Cost and Reserve [Line Items]
Restructuring charges	6	10
Workforce Reduction
Restructuring Cost and Reserve [Line Items]
Severance (including payroll taxes)	6	10
Restructuring charges	6
Workforce Reduction | E&P
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 6	$ 10

Restructuring Charges (Restruct

Restructuring Charges (Restructuring Reserve Rollforward) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Restructuring Reserve [Roll Forward]
Additions	$ 6	$ 10
Workforce Reduction
Restructuring Reserve [Roll Forward]
Liability at December 31, 2020	3
Additions	6
Distributions	(9)
Liability at March 31, 2021	$ 0

Revenue Recognition (Narrative)

Revenue Recognition (Narrative) (Details)	3 Months Ended
	Mar. 31, 2021USD ($)
Disaggregation of Revenue [Line Items]
Contract asset associated with revenues from contracts with customers	$ 0
Contract liability associated with revenues from contracts with customers	$ 0
Minimum | NGL sales
Disaggregation of Revenue [Line Items]
Payment terms	30 days
Minimum | Marketing
Disaggregation of Revenue [Line Items]
Payment terms	30 days
Maximum | NGL sales
Disaggregation of Revenue [Line Items]
Payment terms	60 days
Maximum | Marketing
Disaggregation of Revenue [Line Items]
Payment terms	60 days

Revenue Recognition (Disaggrega

Revenue Recognition (Disaggregation of Revenue by Segment) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Disaggregation of Revenue [Line Items]
Total operating revenues	$ 1,072	$ 592
E&P
Disaggregation of Revenue [Line Items]
Total operating revenues	719	353
Marketing
Disaggregation of Revenue [Line Items]
Total operating revenues	353	239
Operating Segments | E&P
Disaggregation of Revenue [Line Items]
Total operating revenues	705	344
Operating Segments | Marketing
Disaggregation of Revenue [Line Items]
Total operating revenues	997	548
Intersegment Revenues
Disaggregation of Revenue [Line Items]
Total operating revenues	630	300
Intersegment Revenues | E&P
Disaggregation of Revenue [Line Items]
Total operating revenues	(14)	(9)
Intersegment Revenues | Marketing
Disaggregation of Revenue [Line Items]
Total operating revenues	644	309
Gas sales
Disaggregation of Revenue [Line Items]
Total operating revenues	464	248
Gas sales | Operating Segments | E&P
Disaggregation of Revenue [Line Items]
Total operating revenues	451	239
Gas sales | Operating Segments | Marketing
Disaggregation of Revenue [Line Items]
Total operating revenues	0	0
Gas sales | Intersegment Revenues
Disaggregation of Revenue [Line Items]
Total operating revenues	(13)	(9)
Oil sales
Disaggregation of Revenue [Line Items]
Total operating revenues	81	52
Oil sales | Operating Segments | E&P
Disaggregation of Revenue [Line Items]
Total operating revenues	80	52
Oil sales | Operating Segments | Marketing
Disaggregation of Revenue [Line Items]
Total operating revenues	0	0
Oil sales | Intersegment Revenues
Disaggregation of Revenue [Line Items]
Total operating revenues	(1)	0
NGL sales
Disaggregation of Revenue [Line Items]
Total operating revenues	173	50
NGL sales | Operating Segments | E&P
Disaggregation of Revenue [Line Items]
Total operating revenues	173	50
NGL sales | Operating Segments | Marketing
Disaggregation of Revenue [Line Items]
Total operating revenues	0	0
NGL sales | Intersegment Revenues
Disaggregation of Revenue [Line Items]
Total operating revenues	0	0
Marketing
Disaggregation of Revenue [Line Items]
Total operating revenues	352	239
Marketing | Operating Segments | E&P
Disaggregation of Revenue [Line Items]
Total operating revenues	0	0
Marketing | Operating Segments | Marketing
Disaggregation of Revenue [Line Items]
Total operating revenues	996	548
Marketing | Intersegment Revenues
Disaggregation of Revenue [Line Items]
Total operating revenues	644	309
Other
Disaggregation of Revenue [Line Items]
Total operating revenues	2	3
Other | Operating Segments | E&P
Disaggregation of Revenue [Line Items]
Total operating revenues	1	3
Other | Operating Segments | Marketing
Disaggregation of Revenue [Line Items]
Total operating revenues	1	0
Other | Intersegment Revenues
Disaggregation of Revenue [Line Items]
Total operating revenues	$ 0	$ 0

Revenue Recognition (Disaggre_2

Revenue Recognition (Disaggregation of Revenue on Geographic Basis) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Disaggregation of Revenue [Line Items]
Total operating revenues	$ 1,072	$ 592
E&P
Disaggregation of Revenue [Line Items]
Total operating revenues	719	353
Operating Segments | E&P
Disaggregation of Revenue [Line Items]
Total operating revenues	705	344
Operating Segments | E&P | Northeast Appalachia
Disaggregation of Revenue [Line Items]
Total operating revenues	263	195
Operating Segments | E&P | Southwest Appalachia
Disaggregation of Revenue [Line Items]
Total operating revenues	441	149
Operating Segments | E&P | Other
Disaggregation of Revenue [Line Items]
Total operating revenues	$ 1	$ 0

Revenue Recognition (Reconcilia

Revenue Recognition (Reconciliation of Accounts Receivable) (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Receivables from contracts with customers	$ 381	$ 350
Other accounts receivable	19	18
Total accounts receivable	$ 400	$ 368

Cash and Cash Equivalents (Summ

Cash and Cash Equivalents (Summary of Cash and Cash Equivalents) (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Cash and Cash Equivalents [Abstract]
Cash	$ 4	$ 13
Marketable securities	0	0
Total	$ 4	$ 13

Natural Gas and Oil Propertie_2

Natural Gas and Oil Properties (Narrative) (Details)	3 Months Ended
	Mar. 31, 2021USD ($)derivative_position$ / MMBTU$ / bbl	Mar. 31, 2020USD ($)$ / bbl$ / MMBTU
Natural Gas and Oil Properties [Line Items]
Natural gas, oil and NGL reserves discount	10.00%
Period of time needed to calculate ceiling value of reserves	12 months
Number of hedge positions designated for hedge accounting | derivative_position	0
Impairments	$ 0	$ 1,479,000,000
Net book value adjusted for market differentials		$ 1,500,000,000
Montage Resources Corporation
Natural Gas and Oil Properties [Line Items]
Impairments	0
Unamortized cost of properties acquired	1,102,000,000
Montage Resources Corporation | Pro Forma
Natural Gas and Oil Properties [Line Items]
Impairments	$ 0
Natural Gas
Natural Gas and Oil Properties [Line Items]
Full cost ceiling test, price per MMBtu (in dollars per MMBtu) | $ / MMBTU	2.16	2.30
Oil
Natural Gas and Oil Properties [Line Items]
Full cost ceiling test, price per barrel (in dollars per bbl) | $ / bbl	40.01	55.77
NGL
Natural Gas and Oil Properties [Line Items]
Full cost ceiling test, price per barrel (in dollars per bbl) | $ / bbl	13.57	9.96

Earnings Per Share (Narrative)

Earnings Per Share (Narrative) (Details) - Montage Resources Corporation - USD ($) $ / shares in Units, $ in Millions	1 Months Ended
	Aug. 31, 2020	Nov. 13, 2020
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Offering price (in dollars per share)		$ 3.05
Public Stock Offering
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Underwritten public offering of common stock (in shares)	63,250,000
Offering price (in dollars per share)	$ 2.50
Net proceeds from public offering	$ 152

Earnings Per Share (Schedule of

Earnings Per Share (Schedule of Earnings Per Share) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net income (loss)	$ 80	$ (1,547)
Number of common shares:
Weighted average outstanding (in shares)	675,385,145	540,308,491
Weighted average and potential dilutive outstanding (in shares)	679,867,825	540,308,491
Earnings per common share
Basic (in dollars per share)	$ 0.12	$ (2.86)
Diluted (in dollars per share)	$ 0.12	$ (2.86)
Stock options
Number of common shares:
Issued upon assumed exercise of outstanding stock options (in shares)	0	0
Restricted Common Stock
Number of common shares:
Effect of issuance of non-vested restricted common stock (in shares)	870,541	0
Restricted stock units
Number of common shares:
Effect of issuance of non-vested restricted common stock (in shares)	804,944	0
Performance units
Number of common shares:
Effect of issuance of non-vested performance units (in shares)	2,807,195	0

Earnings Per Share (Schedule _2

Earnings Per Share (Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share) (Details) - shares	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	7,782,382	9,179,214
Unexercised stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	3,795,091	4,584,563
Unvested share-based payment
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	0	1,006,860
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	3,987,291	1,312,293
Performance units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	0	2,275,498

Derivatives and Risk Manageme_3

Derivatives and Risk Management (Schedule of Derivative Instruments Notional Amount, Weighted Average Contract Prices and Fair Value) (Details) bbl in Thousands, Mcf in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2021USD ($)$ / bbl$ / MMBTUMcfbbl
Financial protection on production - 2021 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	589
Fair value	$ (8)
Financial protection on production - 2021 | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	4,926
Fair value	$ (41)
Financial protection on production - 2021 | Not Designated as Hedging Instrument | Ethane
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	4,869
Fair value	$ (11)
Fixed Price Swaps - 2021 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	176
Weighted average price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.79
Fair value	$ 14
Fixed Price Swaps - 2021 | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	3,272
Weighted average price (in dollars per MMBtu, Bbl) | $ / bbl	49.27
Fair value	$ (29)
Fixed Price Swaps - 2021 | Not Designated as Hedging Instrument | Ethane
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	4,429
Weighted average price (in dollars per MMBtu, Bbl) | $ / bbl	7.17
Fair value	$ (11)
Fixed Price Swaps - 2021 | Not Designated as Hedging Instrument | Propane
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	5,443
Weighted average price (in dollars per MMBtu, Bbl) | $ / bbl	20.84
Fair value	$ (69)
Fixed Price Swaps - 2021 | Not Designated as Hedging Instrument | Normal Butane
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	1,568
Weighted average price (in dollars per MMBtu, Bbl) | $ / bbl	25.30
Fair value	$ (19)
Fixed Price Swaps - 2021 | Not Designated as Hedging Instrument | Natural Gasoline
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	1,513
Weighted average price (in dollars per MMBtu, Bbl) | $ / bbl	37.91
Fair value	$ (27)
Two-way Costless Collars-2021 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	195
Fair value	$ 1
Two-way Costless Collars-2021 | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	156
Fair value	$ (2)
Two-way Costless Collars-2021 | Not Designated as Hedging Instrument | Ethane
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	440
Fair value	$ 0
Two-way Costless Collars - 2021 Sold Calls | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Cap price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.93
Two-way Costless Collars - 2021 Sold Calls | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Cap price (in dollars per MMBtu, Bbl) | $ / bbl	45.73
Two-way Costless Collars - 2021 Sold Calls | Not Designated as Hedging Instrument | Ethane
Derivative [Line Items]
Cap price (in dollars per MMBtu, Bbl) | $ / bbl	10.40
Three-way Costless-collars - 2021 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	218
Fair value	$ (23)
Three-way Costless-collars - 2021 | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	1,498
Fair value	$ (10)
Three-Way Costless Collars - 2021 Sold Calls | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Cap price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.84
Three-Way Costless Collars - 2021 Sold Calls | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Cap price (in dollars per MMBtu, Bbl) | $ / bbl	53.10
Financial protection on production - 2022 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	453
Fair value	$ (18)
Financial protection on production - 2022 | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	3,099
Fair value	$ (14)
Financial protection on production - 2022 | Not Designated as Hedging Instrument | Ethane
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	1,893
Fair value	$ (1)
Financial protection on production - 2022 | Not Designated as Hedging Instrument | Propane
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	3,028
Fair value	$ (15)
Fixed Price Swaps - 2022 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	112
Weighted average price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.68
Fair value	$ (2)
Fixed Price Swaps - 2022 | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	1,719
Weighted average price (in dollars per MMBtu, Bbl) | $ / bbl	48.54
Fair value	$ (10)
Fixed Price Swaps - 2022 | Not Designated as Hedging Instrument | Ethane
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	1,758
Weighted average price (in dollars per MMBtu, Bbl) | $ / bbl	8.68
Fair value	$ (1)
Fixed Price Swaps - 2022 | Not Designated as Hedging Instrument | Propane
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	2,723
Weighted average price (in dollars per MMBtu, Bbl) | $ / bbl	21.83
Fair value	$ (14)
Fixed Price Swaps - 2022 | Not Designated as Hedging Instrument | Normal Butane
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	888
Weighted average price (in dollars per MMBtu, Bbl) | $ / bbl	24.47
Fair value	$ (5)
Fixed Price Swaps - 2022 | Not Designated as Hedging Instrument | Natural Gasoline
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	857
Weighted average price (in dollars per MMBtu, Bbl) | $ / bbl	40.48
Fair value	$ (8)
Two Way Costless Collars - 2022 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	63
Fair value	$ (3)
Two Way Costless Collars - 2022 | Not Designated as Hedging Instrument | Ethane
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	135
Fair value	$ 0
Two Way Costless Collars - 2022 Sold Calls | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Cap price (in dollars per MMBtu, Bbl) | $ / MMBTU	3.03
Two Way Costless Collars - 2022 Sold Calls | Not Designated as Hedging Instrument | Ethane
Derivative [Line Items]
Cap price (in dollars per MMBtu, Bbl) | $ / bbl	9.66
Three-Way Costless Collars - 2022 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	278
Fair value	$ (13)
Three-Way Costless Collars - 2022 | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	1,380
Fair value	$ (4)
Three-Way Costless Collars - 2022 | Not Designated as Hedging Instrument | Propane
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	305
Fair value	$ (1)
Three-way Costless Collars 2022 - Sold Calls | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Cap price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.97
Three-way Costless Collars 2022 - Sold Calls | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Cap price (in dollars per MMBtu, Bbl) | $ / bbl	57.05
Three-way Costless Collars 2022 - Sold Calls | Not Designated as Hedging Instrument | Propane
Derivative [Line Items]
Cap price (in dollars per MMBtu, Bbl) | $ / bbl	31.92
Three Way Costless Collars - 2023 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	103
Fair value	$ (4)
Three Way Costless Collars - 2023 | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	1,268
Fair value	$ (4)
Three Way Costless Collars - 2023 Sold Calls | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Cap price (in dollars per MMBtu, Bbl) | $ / MMBTU	3.01
Three Way Costless Collars - 2023 Sold Calls | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Cap price (in dollars per MMBtu, Bbl) | $ / bbl	56.12
Basis Swaps | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	605
Fair value	$ 68
Basis Swaps - 2021 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	233
Basis differential per MMBtu | $ / MMBTU	(0.49)
Fair value	$ 39
Basis Swaps - 2022 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	220
Basis differential per MMBtu | $ / MMBTU	(0.44)
Fair value	$ 24
Basis Swap - 2023 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	119
Basis differential per MMBtu | $ / MMBTU	(0.56)
Fair value	$ 4
Basis Swap - 2024 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	24
Basis differential per MMBtu | $ / MMBTU	(0.64)
Fair value	$ 1
Basis Swap - 2025 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	9
Basis differential per MMBtu | $ / MMBTU	(0.64)
Fair value	$ 0
Call options | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	189
Fair value	$ (33)
Call Options 2021 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	57
Cap price (in dollars per MMBtu, Bbl) | $ / MMBTU	3.19
Fair value	$ (4)
Call Options 2021 | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Volume (Bcf, MBbls) | bbl	171
Cap price (in dollars per MMBtu, Bbl) | $ / bbl	60
Fair value	$ (1)
Call Options 2022 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	77
Cap price (in dollars per MMBtu, Bbl) | $ / MMBTU	3
Fair value	$ (16)
Call Options 2023 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	46
Cap price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.94
Fair value	$ (10)
Call Options 2024 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	9
Cap price (in dollars per MMBtu, Bbl) | $ / MMBTU	3
Fair value	$ (3)
Put options | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	19
Fair value	$ (1)
Put Option 2021 | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	14
Floor price (in dollars per MMBtu, Bbl) | $ / MMBTU	2
Fair value	$ 0
Put Option 2022 | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	5
Floor price (in dollars per MMBtu, Bbl) | $ / MMBTU	2
Fair value	$ (1)
Swaption 2021 | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	18
Cap price (in dollars per MMBtu, Bbl) | $ / MMBTU	3
Fair value	$ (1)
Storage 2021 | Not Designated as Hedging Instrument
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	3
Fair value	$ 0
Purchased Fixed Price Swaps, Storage, 2021 | Not Designated as Hedging Instrument
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	2
Weighted average price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.34
Basis differential per MMBtu | $ / MMBTU	0
Fair value	$ 0
Purchased Basis Swaps Storage, 2021 | Not Designated as Hedging Instrument
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	1
Weighted average price (in dollars per MMBtu, Bbl) | $ / MMBTU	0
Basis differential per MMBtu | $ / MMBTU	(0.88)
Fair value	$ 0
Fixed Price Swap, Storage, 2021 | Not Designated as Hedging Instrument
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	0
Weighted average price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.23
Basis differential per MMBtu | $ / MMBTU	0
Fair value	$ 0
Basis Swaps Storage, 2021 | Not Designated as Hedging Instrument
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	0
Weighted average price (in dollars per MMBtu, Bbl) | $ / MMBTU	0
Basis differential per MMBtu | $ / MMBTU	(0.57)
Fair value	$ 0
Storage 2022 | Not Designated as Hedging Instrument
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	3
Fair value	$ 0
Purchased Fixed Price Swaps, Storage, 2022 | Not Designated as Hedging Instrument
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	0
Weighted average price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.14
Basis differential per MMBtu | $ / MMBTU	0
Fair value	$ 0
Fixed Price Swap, Storage, 2022 | Not Designated as Hedging Instrument
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	2
Weighted average price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.82
Basis differential per MMBtu | $ / MMBTU	0
Fair value	$ 0
Basis Swaps Storage, 2022 | Not Designated as Hedging Instrument
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	1
Weighted average price (in dollars per MMBtu, Bbl) | $ / MMBTU	0
Basis differential per MMBtu | $ / MMBTU	(0.57)
Fair value	$ 0
Purchased Fixed Price Swaps, Marketing, 2022 | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Volume (Bcf, MBbls) | Mcf	4
Weighted average price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.44
Fair value	$ 1
Sold Puts | Three-Way Costless Collars - 2021 Sold Puts | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.17
Sold Puts | Three-Way Costless Collars - 2021 Sold Puts | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / bbl	37.86
Sold Puts | Three-Way Costless Collars - 2022 Sold Puts | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.06
Sold Puts | Three-Way Costless Collars - 2022 Sold Puts | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / bbl	39.89
Sold Puts | Three-Way Costless Collars - 2022 Sold Puts | Not Designated as Hedging Instrument | Propane
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / bbl	16.80
Sold Puts | Three Way Costless Collars - 2023 Sold Puts | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.05
Sold Puts | Three Way Costless Collars - 2023 Sold Puts | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / bbl	33.97
Purchased Puts | Two-way Costless Collars - 2021 Purchased Puts | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.57
Purchased Puts | Two-way Costless Collars - 2021 Purchased Puts | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / bbl	37.79
Purchased Puts | Two-way Costless Collars - 2021 Purchased Puts | Not Designated as Hedging Instrument | Ethane
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / bbl	7.14
Purchased Puts | Three-Way Costless Collars - 2021 Purchased Puts | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.50
Purchased Puts | Three-Way Costless Collars - 2021 Purchased Puts | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / bbl	47.70
Purchased Puts | Two Way Costless Collars - 2022 Purchased Puts | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.52
Purchased Puts | Two Way Costless Collars - 2022 Purchased Puts | Not Designated as Hedging Instrument | Ethane
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / bbl	7.56
Purchased Puts | Three Way Costless Collars 2022 - Purchased Puts | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.50
Purchased Puts | Three Way Costless Collars 2022 - Purchased Puts | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / bbl	50.23
Purchased Puts | Three Way Costless Collars 2022 - Purchased Puts | Not Designated as Hedging Instrument | Propane
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / bbl	21
Purchased Puts | Three Way Costless Collars - 2023 Purchased Puts | Not Designated as Hedging Instrument | Natural Gas
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / MMBTU	2.46
Purchased Puts | Three Way Costless Collars - 2023 Purchased Puts | Not Designated as Hedging Instrument | Oil
Derivative [Line Items]
Floor price (in dollars per MMBtu, Bbl) | $ / bbl	45.51

Derivatives and Risk Manageme_4

Derivatives and Risk Management (Narrative) (Details) - Not Designated as Hedging Instrument - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Derivative [Line Items]
Fair value of net derivative liability position	$ 1	$ 1
Commodities
Derivative [Line Items]
Derivative liability	$ (211)

Derivatives and Risk Manageme_5

Derivatives and Risk Management (Balance Sheet Classification of Derivative Financial Instruments) (Details) - Not Designated as Hedging Instrument - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Derivatives, Fair Value [Line Items]
Derivative assets	$ 296	$ 387
Derivative liabilities	506	428
Interest rate swaps | Other long-term assets
Derivatives, Fair Value [Line Items]
Derivative assets	1	0
Natural Gas | Purchased fixed price swaps | Derivative assets
Derivatives, Fair Value [Line Items]
Derivative assets	1	1
Natural Gas | Fixed price swaps | Derivative assets
Derivatives, Fair Value [Line Items]
Derivative assets	25	37
Natural Gas | Fixed price swaps | Other long-term assets
Derivatives, Fair Value [Line Items]
Derivative assets	0	7
Natural Gas | Fixed price swaps | Derivative liabilities
Derivatives, Fair Value [Line Items]
Derivative liabilities	12	7
Natural Gas | Fixed price swaps | Long-term derivative liabilities
Derivatives, Fair Value [Line Items]
Derivative liabilities	1	3
Natural Gas | Two-way costless collars | Derivative assets
Derivatives, Fair Value [Line Items]
Derivative assets	39	54
Natural Gas | Two-way costless collars | Other long-term assets
Derivatives, Fair Value [Line Items]
Derivative assets	2	20
Natural Gas | Two-way costless collars | Derivative liabilities
Derivatives, Fair Value [Line Items]
Derivative liabilities	39	43
Natural Gas | Two-way costless collars | Long-term derivative liabilities
Derivatives, Fair Value [Line Items]
Derivative liabilities	4	21
Natural Gas | Three-way costless collars | Derivative assets
Derivatives, Fair Value [Line Items]
Derivative assets	39	57
Natural Gas | Three-way costless collars | Other long-term assets
Derivatives, Fair Value [Line Items]
Derivative assets	82	87
Natural Gas | Three-way costless collars | Derivative liabilities
Derivatives, Fair Value [Line Items]
Derivative liabilities	73	82
Natural Gas | Three-way costless collars | Long-term derivative liabilities
Derivatives, Fair Value [Line Items]
Derivative liabilities	88	102
Natural Gas | Basis swaps | Derivative assets
Derivatives, Fair Value [Line Items]
Derivative assets	46	60
Natural Gas | Basis swaps | Other long-term assets
Derivatives, Fair Value [Line Items]
Derivative assets	39	15
Natural Gas | Basis swaps | Derivative liabilities
Derivatives, Fair Value [Line Items]
Derivative liabilities	9	3
Natural Gas | Basis swaps | Long-term derivative liabilities
Derivatives, Fair Value [Line Items]
Derivative liabilities	8	7
Natural Gas | Call options | Derivative assets
Derivatives, Fair Value [Line Items]
Derivative assets	1	4
Natural Gas | Call options | Derivative liabilities
Derivatives, Fair Value [Line Items]
Derivative liabilities	13	12
Natural Gas | Call options | Long-term derivative liabilities
Derivatives, Fair Value [Line Items]
Derivative liabilities	21	28
Natural Gas | Put options | Derivative liabilities
Derivatives, Fair Value [Line Items]
Derivative liabilities	1	1
Natural Gas | Swaptions | Derivative liabilities
Derivatives, Fair Value [Line Items]
Derivative liabilities	1	2
Oil | Fixed price swaps | Derivative assets
Derivatives, Fair Value [Line Items]
Derivative assets	0	13
Oil | Fixed price swaps | Other long-term assets
Derivatives, Fair Value [Line Items]
Derivative assets	0	2
Oil | Fixed price swaps | Derivative liabilities
Derivatives, Fair Value [Line Items]
Derivative liabilities	32	12
Oil | Fixed price swaps | Long-term derivative liabilities
Derivatives, Fair Value [Line Items]
Derivative liabilities	7	2
Oil | Two-way costless collars | Derivative liabilities
Derivatives, Fair Value [Line Items]
Derivative liabilities	2	1
Oil | Three-way costless collars | Derivative assets
Derivatives, Fair Value [Line Items]
Derivative assets	6	15
Oil | Three-way costless collars | Other long-term assets
Derivatives, Fair Value [Line Items]
Derivative assets	14	15
Oil | Three-way costless collars | Derivative liabilities
Derivatives, Fair Value [Line Items]
Derivative liabilities	17	15
Oil | Three-way costless collars | Long-term derivative liabilities
Derivatives, Fair Value [Line Items]
Derivative liabilities	21	15
Oil | Call options | Derivative liabilities
Derivatives, Fair Value [Line Items]
Derivative liabilities	1	0
Propane | Fixed price swaps | Other long-term assets
Derivatives, Fair Value [Line Items]
Derivative assets	1	0
Propane | Fixed price swaps | Derivative liabilities
Derivatives, Fair Value [Line Items]
Derivative liabilities	76	36
Propane | Fixed price swaps | Long-term derivative liabilities
Derivatives, Fair Value [Line Items]
Derivative liabilities	8	2
Propane | Three-way costless collars | Long-term derivative liabilities
Derivatives, Fair Value [Line Items]
Derivative liabilities	1	0
Ethane | Fixed price swaps | Derivative liabilities
Derivatives, Fair Value [Line Items]
Derivative liabilities	11	10
Ethane | Fixed price swaps | Long-term derivative liabilities
Derivatives, Fair Value [Line Items]
Derivative liabilities	1	0
Normal Butane | Fixed price swaps | Derivative liabilities
Derivatives, Fair Value [Line Items]
Derivative liabilities	21	8
Normal Butane | Fixed price swaps | Long-term derivative liabilities
Derivatives, Fair Value [Line Items]
Derivative liabilities	3	1
Natural Gasoline | Fixed price swaps | Derivative liabilities
Derivatives, Fair Value [Line Items]
Derivative liabilities	30	13
Natural Gasoline | Fixed price swaps | Long-term derivative liabilities
Derivatives, Fair Value [Line Items]
Derivative liabilities	$ 5	$ 2

Derivatives and Risk Manageme_6

Derivatives and Risk Management (Summary of Before Tax Effect of Fair Value Hedges not Designated for Hedge Accounting) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Derivative Instruments, Gain (Loss) [Line Items]
Unsettled Gain (Loss) on Derivatives Recognized in Earnings	$ (169)	$ 246
Settled Gain (Loss) on Derivatives Recognized in Earnings	(22)	93
Total gain (loss) on derivatives	(191)	339
Purchased fixed price swaps | Natural Gas
Derivative Instruments, Gain (Loss) [Line Items]
Unsettled Gain (Loss) on Derivatives Recognized in Earnings	0	(1)
Settled Gain (Loss) on Derivatives Recognized in Earnings	0	(1)
Purchased fixed price swaps | Oil
Derivative Instruments, Gain (Loss) [Line Items]
Unsettled Gain (Loss) on Derivatives Recognized in Earnings	0	(5)
Purchased fixed price swaps | Natural Gas Storage
Derivative Instruments, Gain (Loss) [Line Items]
Unsettled Gain (Loss) on Derivatives Recognized in Earnings	0	(1)
Fixed price swaps | Natural Gas
Derivative Instruments, Gain (Loss) [Line Items]
Unsettled Gain (Loss) on Derivatives Recognized in Earnings	(22)	103
Settled Gain (Loss) on Derivatives Recognized in Earnings	5	5
Fixed price swaps | Oil
Derivative Instruments, Gain (Loss) [Line Items]
Unsettled Gain (Loss) on Derivatives Recognized in Earnings	(40)	118
Settled Gain (Loss) on Derivatives Recognized in Earnings	(17)	9
Fixed price swaps | Ethane
Derivative Instruments, Gain (Loss) [Line Items]
Unsettled Gain (Loss) on Derivatives Recognized in Earnings	(2)	12
Settled Gain (Loss) on Derivatives Recognized in Earnings	(4)	6
Fixed price swaps | Propane
Derivative Instruments, Gain (Loss) [Line Items]
Unsettled Gain (Loss) on Derivatives Recognized in Earnings	(45)	36
Settled Gain (Loss) on Derivatives Recognized in Earnings	(30)	10
Fixed price swaps | Normal Butane
Derivative Instruments, Gain (Loss) [Line Items]
Unsettled Gain (Loss) on Derivatives Recognized in Earnings	(15)	0
Settled Gain (Loss) on Derivatives Recognized in Earnings	(7)	0
Fixed price swaps | Natural Gasoline
Derivative Instruments, Gain (Loss) [Line Items]
Unsettled Gain (Loss) on Derivatives Recognized in Earnings	(20)	0
Settled Gain (Loss) on Derivatives Recognized in Earnings	(9)	0
Two-way costless collars | Natural Gas
Derivative Instruments, Gain (Loss) [Line Items]
Unsettled Gain (Loss) on Derivatives Recognized in Earnings	(12)	(4)
Settled Gain (Loss) on Derivatives Recognized in Earnings	2	6
Two-way costless collars | Oil
Derivative Instruments, Gain (Loss) [Line Items]
Unsettled Gain (Loss) on Derivatives Recognized in Earnings	(1)	19
Settled Gain (Loss) on Derivatives Recognized in Earnings	(1)	3
Two-way costless collars | Propane
Derivative Instruments, Gain (Loss) [Line Items]
Unsettled Gain (Loss) on Derivatives Recognized in Earnings	0	2
Settled Gain (Loss) on Derivatives Recognized in Earnings	0	1
Three-way costless collars | Natural Gas
Derivative Instruments, Gain (Loss) [Line Items]
Unsettled Gain (Loss) on Derivatives Recognized in Earnings	0	(51)
Settled Gain (Loss) on Derivatives Recognized in Earnings	1	36
Three-way costless collars | Oil
Derivative Instruments, Gain (Loss) [Line Items]
Unsettled Gain (Loss) on Derivatives Recognized in Earnings	(18)	25
Settled Gain (Loss) on Derivatives Recognized in Earnings	(1)	1
Three-way costless collars | Propane
Derivative Instruments, Gain (Loss) [Line Items]
Unsettled Gain (Loss) on Derivatives Recognized in Earnings	(1)	0
Basis swaps | Natural Gas
Derivative Instruments, Gain (Loss) [Line Items]
Unsettled Gain (Loss) on Derivatives Recognized in Earnings	3	(1)
Settled Gain (Loss) on Derivatives Recognized in Earnings	41	16
Call options | Natural Gas
Derivative Instruments, Gain (Loss) [Line Items]
Unsettled Gain (Loss) on Derivatives Recognized in Earnings	3	(5)
Call options | Oil
Derivative Instruments, Gain (Loss) [Line Items]
Unsettled Gain (Loss) on Derivatives Recognized in Earnings	(1)	1
Swaptions | Natural Gas
Derivative Instruments, Gain (Loss) [Line Items]
Unsettled Gain (Loss) on Derivatives Recognized in Earnings	1	0
Fixed price swaps – storage | Natural Gas Storage
Derivative Instruments, Gain (Loss) [Line Items]
Unsettled Gain (Loss) on Derivatives Recognized in Earnings	0	(1)
Settled Gain (Loss) on Derivatives Recognized in Earnings	0	1
Interest rate swaps
Derivative Instruments, Gain (Loss) [Line Items]
Unsettled Gain (Loss) on Derivatives Recognized in Earnings	1	(1)
Put options | Natural Gas
Derivative Instruments, Gain (Loss) [Line Items]
Settled Gain (Loss) on Derivatives Recognized in Earnings	(2)	$ 0
Amortization of premium paid	$ 2

Reclassifications from Accumu_3

Reclassifications from Accumulated Other Comprehensive Income (Loss) (Components of Accumulated Other Comprehensive Income (Loss)) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2021USD ($)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance beginning	$ 497
Balance ending	586
Pension and Other Postretirement
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance beginning	(24)
Other comprehensive income before reclassifications	0
Amounts reclassified from other comprehensive income	0
Net current-period other comprehensive income	0
Balance ending	(24)
Foreign Currency
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance beginning	(14)
Other comprehensive income before reclassifications	0
Amounts reclassified from other comprehensive income	0
Net current-period other comprehensive income	0
Balance ending	(14)
Total
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance beginning	(38)
Other comprehensive income before reclassifications	0
Amounts reclassified from other comprehensive income	0
Net current-period other comprehensive income	0
Balance ending	$ (38)

Reclassifications from Accumu_4

Reclassifications from Accumulated Other Comprehensive Income (Loss) (Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other Income, Net	$ 1	$ 1
Provision (Benefit) for Income Taxes	0	406
Net income (loss)	80	$ (1,547)
Amount Reclassified from Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income (loss)	0
Amortization of prior service cost and net loss | Amount Reclassified from Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other Income, Net	0
Provision (Benefit) for Income Taxes	0
Net income (loss)	$ 0

Fair Value Measurements (Carryi

Fair Value Measurements (Carrying Amount and Estimated Fair Values of Financial Instruments) (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative instruments, net	$ (210)	$ (41)
Carrying Amount
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	4	13
Derivative instruments, net	(210)	(41)
Carrying Amount | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior notes	2,471	2,471
Fair Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	4	13
Derivative instruments, net	(210)	(41)
Fair Value | Senior Notes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior notes	2,640	2,609
2018 revolving credit facility due April 2024 | Carrying Amount | Long-term debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
2018 revolving credit facility due April 2024	567	700
2018 revolving credit facility due April 2024 | Fair Value | Long-term debt
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
2018 revolving credit facility due April 2024	$ 567	$ 700

Fair Value Measurements (Narrat

Fair Value Measurements (Narrative) (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Not Designated as Hedging Instrument
Debt Instrument [Line Items]
Fair value of net derivative liability position	$ 1	$ 1
Senior Notes | 4.20% Senior Notes Due March 2022
Debt Instrument [Line Items]
Stated interest rate	4.10%

Fair Value Measurements (Summar

Fair Value Measurements (Summary of Assets and Liabilities Measured at Fair Value on Recurring Basis) (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative instruments, net	$ (210)	$ (41)
Quoted Prices in Active Markets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative instruments, net	0	0
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative instruments, net	(210)	(41)
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative instruments, net	0	0
Purchased fixed price swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	1	1
Purchased fixed price swaps | Quoted Prices in Active Markets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	0	0
Purchased fixed price swaps | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	1	1
Purchased fixed price swaps | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	0	0
Fixed price swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	26	59
Derivative liabilities	(207)	(96)
Fixed price swaps | Quoted Prices in Active Markets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	0	0
Derivative liabilities	0	0
Fixed price swaps | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	26	59
Derivative liabilities	(207)	(96)
Fixed price swaps | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	0	0
Derivative liabilities	0	0
Two-way costless collars
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	41	74
Derivative liabilities	(45)	(65)
Two-way costless collars | Quoted Prices in Active Markets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	0	0
Derivative liabilities	0	0
Two-way costless collars | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	41	74
Derivative liabilities	(45)	(65)
Two-way costless collars | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	0	0
Derivative liabilities	0	0
Three-way costless collars
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	141	174
Derivative liabilities	(200)	(214)
Three-way costless collars | Quoted Prices in Active Markets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	0	0
Derivative liabilities	0	0
Three-way costless collars | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	141	174
Derivative liabilities	(200)	(214)
Three-way costless collars | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	0	0
Derivative liabilities	0	0
Basis swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	85	75
Derivative liabilities	(17)	(10)
Basis swaps | Quoted Prices in Active Markets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	0	0
Derivative liabilities	0	0
Basis swaps | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	85	75
Derivative liabilities	(17)	(10)
Basis swaps | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	0	0
Derivative liabilities	0	0
Call options
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	1	4
Derivative liabilities	(35)	(40)
Call options | Quoted Prices in Active Markets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	0	0
Derivative liabilities	0	0
Call options | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	1	4
Derivative liabilities	(35)	(40)
Call options | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	0	0
Derivative liabilities	0	0
Interest rate swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	1
Interest rate swaps | Quoted Prices in Active Markets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	0
Interest rate swaps | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	1
Interest rate swaps | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	0
Put options
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	(1)	(1)
Put options | Quoted Prices in Active Markets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	0	0
Put options | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	(1)	(1)
Put options | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	0	0
Swaptions
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	(1)	(2)
Swaptions | Quoted Prices in Active Markets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	0	0
Swaptions | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	(1)	(2)
Swaptions | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	$ 0	$ 0

Debt (Components of Debt) (Deta

Debt (Components of Debt) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020	Aug. 31, 2020	Jul. 24, 2020	Mar. 31, 2020	Jul. 31, 2018	Jan. 31, 2015
Debt Instrument [Line Items]
Debt Instrument	$ 3,038	$ 3,171
Unamortized Issuance Expense	18	20
Unamortized Debt Discount	(1)	(1)
Current portion of long-term debt	207	0
Total debt	3,019	3,150
Long-term debt
Debt Instrument [Line Items]
Debt Instrument	2,831
Unamortized Issuance Expense	18
Unamortized Debt Discount	(1)
Total debt	$ 2,812
Line of Credit | Variable rate (2.09% at March 31, 2021) 2018 revolving credit facility due April 2024
Debt Instrument [Line Items]
Variable interest rate	2.09%
Line of Credit | Variable rate (2.09% at March 31, 2021) 2018 revolving credit facility due April 2024 | Revolving Credit Facility
Debt Instrument [Line Items]
Debt Instrument	$ 567
Unamortized Issuance Expense	0
Unamortized Debt Discount	0
Total debt	567
Line of Credit | Variable rate (2.11% at December 31, 2020) 2018 term loan facility due April 2024
Debt Instrument [Line Items]
Debt Instrument		700
Unamortized Issuance Expense		0
Unamortized Debt Discount		0
Total debt		$ 700
Variable interest rate		2.11%
Senior Notes
Debt Instrument [Line Items]
Debt Instrument, current portion of long-term debt	207
Unamortized Issuance Expense	0
Unamortized Debt Discount	0
Current portion of long-term debt	207
Senior Notes | 4.10% Senior Notes due March 2022
Debt Instrument [Line Items]
Debt Instrument, current portion of long-term debt	207
Debt Instrument		$ 207
Unamortized Issuance Expense	0	0
Unamortized Debt Discount	0	0
Current portion of long-term debt	$ 207
Total debt		$ 207
Stated interest rate	4.10%	4.10%			4.10%
Senior Notes | 4.95% Senior Notes due January 2025
Debt Instrument [Line Items]
Debt Instrument	$ 856	$ 856
Unamortized Issuance Expense	4	4
Unamortized Debt Discount	(1)	(1)
Total debt	$ 851	$ 851
Stated interest rate	4.95%	4.95%		6.45%	4.95%	6.20%	4.95%
Senior notes							$ 1,000
Senior Notes | 7.50% Senior Notes due April 2026
Debt Instrument [Line Items]
Debt Instrument	$ 618	$ 618
Unamortized Issuance Expense	5	6
Unamortized Debt Discount	0	0
Total debt	$ 613	$ 612
Stated interest rate	7.50%	7.50%			7.50%
Senior Notes | 7.75% Senior Notes due October 2027
Debt Instrument [Line Items]
Debt Instrument	$ 440	$ 440
Unamortized Issuance Expense	4	5
Unamortized Debt Discount	0	0
Total debt	$ 436	$ 435
Stated interest rate	7.75%	7.75%			7.75%
Senior Notes | 8.375% Senior Notes due September 2028
Debt Instrument [Line Items]
Debt Instrument	$ 350	$ 350
Unamortized Issuance Expense	5	5
Unamortized Debt Discount	0	0
Total debt	$ 345	$ 345
Stated interest rate	8.375%	8.375%	8.375%
Senior notes			$ 350
Other long-term assets | Line of Credit | Variable rate (2.09% at March 31, 2021) 2018 revolving credit facility due April 2024
Debt Instrument [Line Items]
Unamortized Issuance Expense	$ 11	$ 12

Debt (Schedule of Debt Maturiti

Debt (Schedule of Debt Maturities) (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Long-term Debt, Fiscal Year Maturity [Abstract]
2021	$ 0
2022	207
2023	0
2024	567
2025	856
Thereafter	1,408
Total	$ 3,038	$ 3,171

Debt (2018 Revolving Credit Fac

Debt (2018 Revolving Credit Facility - Narrative) (Details)	1 Months Ended	3 Months Ended
	Apr. 30, 2018USD ($)	Mar. 31, 2021USD ($)	Jun. 30, 2018USD ($)	Dec. 31, 2020USD ($)	Oct. 31, 2020USD ($)
Debt Instrument [Line Items]
Subsidiary ownership		100.00%
Letters of credit		$ 233,000,000
Debt instrument		3,038,000,000		$ 3,171,000,000
Long-term debt
Debt Instrument [Line Items]
Debt instrument		2,831,000,000
Long-term debt | 2018 revolving credit facility due April 2024
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 3,500,000,000
Current borrowing base					$ 2,000,000,000
Aggregate commitment					$ 2,000,000,000
Limit on securing indebtedness	$ 2,000,000,000
Percentage of consolidated net tangible assets	25.00%
Minimum interest coverage ratio			1
Long-term debt | 2018 revolving credit facility due April 2024 | Maximum
Debt Instrument [Line Items]
Leverage ratio, percentage of credit limit			10.00%
Leverage ratio, amount of credit limit			$ 150,000,000
Long-term debt | 2018 revolving credit facility due April 2024 | Eurodollar | Minimum
Debt Instrument [Line Items]
Basis points	1.75%
Long-term debt | 2018 revolving credit facility due April 2024 | Eurodollar | Maximum
Debt Instrument [Line Items]
Basis points	2.75%
Long-term debt | 2018 revolving credit facility due April 2024 | Base Rate | Minimum
Debt Instrument [Line Items]
Basis points	0.75%
Long-term debt | 2018 revolving credit facility due April 2024 | Base Rate | Maximum
Debt Instrument [Line Items]
Basis points	1.75%
Line of Credit | Revolving Credit Facility | 2018 Revolving Credit Facility
Debt Instrument [Line Items]
Debt instrument		$ 567,000,000
After June 30, 2020 | Long-term debt | 2018 revolving credit facility due April 2024 | Maximum
Debt Instrument [Line Items]
Leverage ratio			4

Debt (Senior Notes - Narrative)

Debt (Senior Notes - Narrative) (Details) - USD ($) $ in Millions	1 Months Ended		3 Months Ended
	Aug. 31, 2020	Jan. 31, 2015	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020	Jul. 24, 2020	Apr. 07, 2020	Jul. 31, 2018
Debt Instrument [Line Items]
Gain on extinguishment of debt			$ 0	$ 28
Senior Notes
Debt Instrument [Line Items]
Gain on extinguishment of debt				28
Repayments of Long-term Debt				$ 52
Senior Notes | LIBOR
Debt Instrument [Line Items]
Incremental increase in basis points resulting from downgrades		0.25%
Incremental decrease in basis points resulting from upgrades		0.25%
4.95% Senior Notes due January 2025 | Senior Notes
Debt Instrument [Line Items]
Senior notes		$ 1,000
Stated interest rate		4.95%	4.95%	4.95%	4.95%	6.45%		6.20%
Stated interest rate cap							6.95%
Repurchased amount				$ 28
4.10% Senior Notes due March 2022 | Senior Notes
Debt Instrument [Line Items]
Stated interest rate			4.10%	4.10%	4.10%
Repurchased amount				$ 3
7.50% Senior Notes Due April 2026 | Senior Notes
Debt Instrument [Line Items]
Stated interest rate			7.50%	7.50%	7.50%
Repurchased amount				$ 18
7.75% Senior Notes due October 2027 | Senior Notes
Debt Instrument [Line Items]
Stated interest rate			7.75%	7.75%	7.75%
Repurchased amount				$ 31
8.375% Senior Notes due September 2028 | Senior Notes
Debt Instrument [Line Items]
Senior notes	$ 350
Stated interest rate	8.375%		8.375%		8.375%
Proceeds from issuance of long-term debt	$ 345
Percentage price of face value of the notes sold to the public	100.00%
Eight Point Eight Seven Five Percent Senior Notes Due 2023 | Senior Notes | Montage Resources Corporation
Debt Instrument [Line Items]
Senior notes	$ 510
Stated interest rate	8.875%

Commitments and Contingencies_2

Commitments and Contingencies (Narrative) (Details)	Mar. 31, 2021USD ($)
Commitments And Contingencies [Line Items]
Obligation under transportation agreements	$ 8,351,000,000
Guarantee obligations relative to the firms transportation agreements and gathering project and services	908,000,000
Material liabilities recognized	0
Pending regulatory approval and/or construction
Commitments And Contingencies [Line Items]
Obligation under transportation agreements	$ 436,000,000

Commitments and Contingencies_3

Commitments and Contingencies (Schedule of Future Obligation under Transportation Agreements) (Details) $ in Millions	Mar. 31, 2021USD ($)
Other Commitments [Line Items]
Total	$ 8,351
Less than 1 Year	791
1 to 3 Years	1,569
3 to 5 Years	1,333
5 to 8 Years	1,833
More than 8 Years	2,825
Infrastructure currently in service
Other Commitments [Line Items]
Total	7,915
Less than 1 Year	789
1 to 3 Years	1,539
3 to 5 Years	1,295
5 to 8 Years	1,752
More than 8 Years	2,540
Pending regulatory approval and/or construction
Other Commitments [Line Items]
Total	436
Less than 1 Year	2
1 to 3 Years	30
3 to 5 Years	38
5 to 8 Years	81
More than 8 Years	$ 285

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Income Tax Expense (Benefit), Continuing Operations [Abstract]
Effective tax rate	0.00%	(36.00%)
Discrete tax benefit		$ 408
Valuation allowance related to operating loss		$ 87

Pension Plan and Other Postre_3

Pension Plan and Other Postretirement Benefits (Pension and Other Postretirement Benefit Costs) (Details) - Pension - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0	$ 2
Interest cost	1	1
Expected return on plan assets	(1)	(1)
Net periodic benefit cost	$ 0	$ 2

Pension Plan and Other Postre_4

Pension Plan and Other Postretirement Benefits (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 5
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost	1	$ 1
Benefit obligation	13		$ 13
Pension
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost	0	$ 2
Expected future employer contributions, remainder of fiscal year	7
Benefit obligation	$ 28		$ 33
Non-Qualified Supplemental Employee Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Treasury stock acquired (in shares)	2,035		3,632

Long-term Incentive Compensat_3

Long-term Incentive Compensation (Narrative) (Details) $ in Millions	3 Months Ended				12 Months Ended
	Mar. 31, 2021USD ($)award_plan	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Stock Based Compensation 2013 Plan
Long-term Incentive Compensation [Line Items]
Service period	3 years
Stock options
Long-term Incentive Compensation [Line Items]
Vesting period	3 years
Expiration period	7 years
Restricted stock
Long-term Incentive Compensation [Line Items]
Vesting period	4 years
Performance units
Long-term Incentive Compensation [Line Items]
Vesting period	3 years				3 years	3 years	3 years
Weighted average period over which unrecognized cost is recognized, years	2 years 1 month 6 days
Liability classified awards, unrecognized compensation costs	$ 22
Number of award plans granted | award_plan	2
Share-based payment arrangement
Long-term Incentive Compensation [Line Items]
Equity-classified awards, unrecognized compensation cost	$ 1
Weighted average period over which unrecognized cost is recognized, years	1 year
Restricted stock units
Long-term Incentive Compensation [Line Items]
Vesting period	3 years	4 years	4 years	4 years
Weighted average period over which unrecognized cost is recognized, years	2 years 2 months 12 days
Liability classified awards, unrecognized compensation costs	$ 32
Performance cash awards
Long-term Incentive Compensation [Line Items]
Vesting period	4 years				4 years
Weighted average period over which unrecognized cost is recognized, years	3 years 6 months
Liability classified awards, unrecognized compensation costs	$ 30

Long-term Incentive Compensat_4

Long-term Incentive Compensation (Schedule of Stock-Based Compensation Costs) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Share-based Payment Arrangement, Noncash Expense [Abstract]
Stock-based compensation cost – expensed	$ 13	$ 0
Stock-based compensation cost – capitalized	$ 5	$ 0

Long-term Incentive Compensat_5

Long-term Incentive Compensation (Schedule of Equity-Classified Stock-Based Compensation Costs) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Share-based Payment Arrangement, Noncash Expense [Abstract]
Equity-classified awards – expensed	$ 0	$ 1
Equity-classified awards – capitalized	$ 0	$ 0

Long-term Incentive Compensat_6

Long-term Incentive Compensation (Summary of Equity-Classified Stock Option Activity) (Details) - Stock options shares in Thousands	3 Months Ended
	Mar. 31, 2021$ / sharesshares
Number of Options
Beginning balance (in shares) | shares	3,850
Granted (in shares) | shares	0
Exercised (in shares) | shares	0
Forfeited or expired (in shares) | shares	(61)
Ending balance (in shares) | shares	3,789
Exercisable (in shares) | shares	3,789
Weighted Average Exercise Price
Beginning balance (in dollars per share) | $ / shares	$ 13.39
Granted (in dollars per share) | $ / shares	0
Exercised (in dollars per share) | $ / shares	0
Forfeited or expired (in dollars per share) | $ / shares	10.93
Ending balance (in dollars per share) | $ / shares	13.43
Exercisable (in dollars per share) | $ / shares	$ 13.43

Long-term Incentive Compensat_7

Long-term Incentive Compensation (Summary of Equity-Classified Restricted Stock Activity) (Details) - Restricted stock shares in Thousands	3 Months Ended
	Mar. 31, 2021$ / sharesshares
Number of Units
Beginning balance (in shares) | shares	697
Granted (in shares) | shares	10
Vested (in shares) | shares	(451)
Forfeited (in shares) | shares	0
Ending balance (in shares) | shares	256
Weighted Average Fair Value
Beginning balance (in dollars per share) | $ / shares	$ 5.97
Granted (in dollars per share) | $ / shares	2.98
Vested (in dollars per share) | $ / shares	7.61
Forfeited (in dollars per share) | $ / shares	8.59
Ending balance (in dollars per share) | $ / shares	$ 2.94

Long-term Incentive Compensat_8

Long-term Incentive Compensation (Summary of Equity-Classified Restricted Stock Units Activity) (Details) - Restricted stock units shares in Thousands	3 Months Ended
	Mar. 31, 2021$ / sharesshares
Number of Units
Beginning balance (in shares) | shares	134
Granted (in shares) | shares	0
Vested (in shares) | shares	(45)
Forfeited (in shares) | shares	0
Ending balance (in shares) | shares	89
Weighted Average Fair Value
Beginning balance (in dollars per share) | $ / shares	$ 3.05
Granted (in dollars per share) | $ / shares	0
Vested (in dollars per share) | $ / shares	3.05
Forfeited (in dollars per share) | $ / shares	0
Ending balance (in dollars per share) | $ / shares	$ 3.05

Long-term Incentive Compensat_9

Long-term Incentive Compensation (Schedule of Liability-Classified Stock-Based Compensation Costs) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Share-based Payment Arrangement, Noncash Expense [Abstract]
Liability-classified stock-based compensation cost – expensed	$ 13	$ (1)
Liability-classified stock-based compensation cost – capitalized	$ 5	$ 0

Long-term Incentive Compensa_10

Long-term Incentive Compensation (Summary of Liability-Classified Restricted Stock Unit Activity) (Details) - Restricted stock units shares in Thousands	3 Months Ended
	Mar. 31, 2021$ / sharesshares
Number of Units
Beginning balance (in shares) | shares	11,613
Granted (in shares) | shares	1,486
Vested (in shares) | shares	(4,522)
Forfeited (in shares) | shares	(416)
Ending balance (in shares) | shares	8,161
Weighted Average Fair Value
Beginning balance (in dollars per share) | $ / shares	$ 2.67
Granted (in dollars per share) | $ / shares	4.23
Vested (in dollars per share) | $ / shares	3.40
Forfeited (in dollars per share) | $ / shares	4.31
Ending balance (in dollars per share) | $ / shares	$ 4.07

Long-term Incentive Compensa_11

Long-term Incentive Compensation (Summary of Liability-Classified Performance Cash Awards ) (Details) - Performance units shares in Thousands	3 Months Ended
	Mar. 31, 2021$ / sharesshares
Number of Units
Beginning balance (in shares) | shares	8,699
Granted (in shares) | shares	3,580
Vested (in shares) | shares	(2,020)
Forfeited (in shares) | shares	(622)
Ending balance (in shares) | shares	9,637
Weighted Average Fair Value
Beginning balance (in dollars per share) | $ / shares	$ 2.57
Granted (in dollars per share) | $ / shares	4.14
Vested (in dollars per share) | $ / shares	4.05
Forfeited (in dollars per share) | $ / shares	2.98
Ending balance (in dollars per share) | $ / shares	$ 2.88

Long-term Incentive Compensa_12

Long-term Incentive Compensation (Summary of Liability-Classified Restricted Cash Unit Activity) (Details) - Performance cash awards shares in Thousands	3 Months Ended
	Mar. 31, 2021$ / sharesshares
Number of Units
Beginning balance (in shares) | shares	18,353
Granted (in shares) | shares	18,546
Vested (in shares) | shares	(4,319)
Forfeited (in shares) | shares	(1,615)
Ending balance (in shares) | shares	30,965
Weighted Average Fair Value
Beginning balance (in dollars per share) | $ / shares	$ 1
Granted (in dollars per share) | $ / shares	1
Vested (in dollars per share) | $ / shares	1
Forfeited (in dollars per share) | $ / shares	1
Ending balance (in dollars per share) | $ / shares	$ 1

Segment Information (Details)

Segment Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Segment Reporting Information [Line Items]
Total operating revenues	$ 1,072	$ 592
Depreciation, depletion and amortization expense	96	113
Impairments	0	1,479
Operating income (loss)	301	(1,490)
Interest expense	31	19
(Loss) gain on derivatives	(191)	339
Gain on early extinguishment of debt	0	28
Other income, net	1	1
Benefit from income taxes	0	406
Assets	5,247	5,275	$ 5,160
Capital investments	266	237
Restructuring charges	6	10
Montage merger-related expenses	1	0
Change in accrued expenditures	38	8
Intersegment Revenues
Segment Reporting Information [Line Items]
Total operating revenues	630	300
E&P
Segment Reporting Information [Line Items]
Total operating revenues	719	353
Depreciation, depletion and amortization expense	94	111
Impairments		1,479
Operating income (loss)	295	(1,486)
Interest expense	31	19
(Loss) gain on derivatives	(191)	339
Gain on early extinguishment of debt		0
Other income, net	1	1
Benefit from income taxes		406
Assets	4,741	4,900
Capital investments	266	237
Restructuring charges	6	10
Montage merger-related expenses	1
E&P | Intersegment Revenues
Segment Reporting Information [Line Items]
Total operating revenues	(14)	(9)
Marketing
Segment Reporting Information [Line Items]
Total operating revenues	353	239
Depreciation, depletion and amortization expense	2	2
Impairments		0
Operating income (loss)	6	(4)
Interest expense	0	0
(Loss) gain on derivatives	0	0
Gain on early extinguishment of debt		0
Other income, net	0	0
Benefit from income taxes		0
Assets	396	214
Capital investments	0	0
Marketing | Intersegment Revenues
Segment Reporting Information [Line Items]
Total operating revenues	644	309
Other
Segment Reporting Information [Line Items]
Total operating revenues	0	0
Depreciation, depletion and amortization expense	0	0
Impairments		0
Operating income (loss)	0	0
Interest expense	0	0
(Loss) gain on derivatives	0	0
Gain on early extinguishment of debt		28
Other income, net	0	0
Benefit from income taxes		0
Assets	110	161
Capital investments	0	0
Other | Intersegment Revenues
Segment Reporting Information [Line Items]
Total operating revenues	$ 0	$ 0

Segment Information (Schedule o

Segment Information (Schedule of Other Assets) (Details) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020
Segment Reporting Information [Line Items]
Cash and cash equivalents	$ 4	$ 13
Property, plant and equipment	4,284	4,111
Unamortized debt expense	18	20
Right-of-use lease assets	155	163
TOTAL ASSETS	5,247	$ 5,160	$ 5,275
Other
Segment Reporting Information [Line Items]
Cash and cash equivalents	4		5
Income taxes receivable	0		32
Prepayments	6		9
Property, plant and equipment	15		23
Unamortized debt expense	11		10
Right-of-use lease assets	70		77
Non-qualified retirement plan	4		5
TOTAL ASSETS	$ 110		$ 161