Southwestern Energy (SWN) 10-Q 4 May 18 2018 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2018	Apr. 30, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1
Entity Registrant Name	SOUTHWESTERN ENERGY CO
Entity Central Index Key	7,332
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		586,806,166
Trading Symbol	SWN

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018		Mar. 31, 2017
Operating Revenues:
Gas sales	$ 540		$ 503
Oil sales	35		23
NGL sales	65		40
Marketing	253		253
Gas gathering	24		27
Other	3
Total Operating Revenues	920		846
Operating Costs and Expenses:
Marketing purchases	255		251
Operating expenses	189		147
General and administrative expenses	55		50
Depreciation, depletion and amortization	143		106
Taxes, other than income taxes	23		26
Total Operating Costs and Expenses	665		580
Operating Income	255		266
Interest Expense:
Interest on debt	65		58
Other interest charges	2		2
Interest capitalized	(28)		(28)
Total Interest Expense	39		32
Gain (Loss) on Derivatives	(7)		116
Other Income (Loss), Net	(1)		1
Income Before Income Taxes	208		351
Provision (Benefit) for Income Taxes:
Current
Deferred
Total Provision (Benefit) for Income Taxes
Net Income	208	[1]	351
Mandatory convertible preferred stock dividend			27
Participating securities - mandatory convertible preferred stock	3		43
Net Income Attributable to Common Stock	$ 205		$ 281
Earnings Per Common Share:
Basic	$ 0.36		$ 0.57
Diluted	$ 0.36		$ 0.57
Weighted Average Common Shares Outstanding:
Basic	571,297,804		493,068,000
Diluted	573,844,459		494,494,995
[1]	In 2018, deferred tax activity incurred in other comprehensive income was offset by a valuation allowance.

CONDENSED CONSOLIDATED STATEME3

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	[1]	Mar. 31, 2017
CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) [Abstract]
Net income		$ 208		$ 351
Change in value of pension and other postretirement liabilities:
Amortization of prior service cost and net loss included in net periodic pension cost	[2]
Comprehensive income		$ 208		$ 351
[1]	In 2018, deferred tax activity incurred in other comprehensive income was offset by a valuation allowance.
[2]	Net of $1 million in taxes for the three months ended March 31, 2017.

CONDENSED CONSOLIDATED STATEME4

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Parenthetical) $ in Millions	3 Months Ended
	Mar. 31, 2017USD ($)
CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) [Abstract]
Amortization of prior service cost and net loss included in net periodic pension cost, tax	$ 1

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 958	$ 916
Accounts receivable, net	382	428
Derivative assets	110	130
Other current assets	38	35
Total current assets	1,488	1,509
Natural gas and oil properties, using the full cost method, including $1,822 million as of March 31, 2018 and $1,817 million as of December 31, 2017 excluded from amortization	24,224	23,890
Gathering systems	1,318	1,315
Other	562	564
Less: Accumulated depreciation, depletion and amortization	(20,136)	(19,997)
Total property and equipment, net	5,968	5,772
Other long-term assets	257	240
TOTAL ASSETS	7,713	7,521
Current liabilities:
Accounts payable	555	533
Taxes payable	50	62
Interest payable	64	70
Dividends payable		27
Derivative liabilities	40	64
Other current liabilities	23	24
Total current liabilities	732	780
Long-term debt	4,393	4,391
Pension and other postretirement liabilities	58	58
Other long-term liabilities	337	313
Total long-term liabilities	4,788	4,762
Commitments and contingencies (Note 10)
Equity:
Common stock, $0.01 par value; 1,250,000,000 shares authorized; issued 586,833,276 shares as of March 31, 2018 and 512,134,311 as of December 31, 2017	6	5
Preferred stock, $0.01 par value, 10,000,000 shares authorized, 6.25% Series B Mandatory Convertible, $1,000 per share liquidation preference, 1,725,000 shares issued and outstanding as of December 31, 2017, converted to common stock on January 12, 2018
Additional paid-in capital	4,703	4,698
Accumulated deficit	(2,471)	(2,679)
Accumulated other comprehensive loss	(44)	(44)
Common stock in treasury, 31,269 shares as of March 31, 2018 and December 31, 2017	(1)	(1)
Total equity	2,193	1,979
TOTAL LIABILITIES AND EQUITY	$ 7,713	$ 7,521

CONDENSED CONSOLIDATED BALANCE6

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
CONDENSED CONSOLIDATED BALANCE SHEETS [Abstract]
Natural gas and oil properties, using the full cost method, costs excluded from amortization	$ 1,822	$ 1,817
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	1,250,000,000	1,250,000,000
Common stock, shares issued	586,833,276	512,134,311
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, dividend rate	6.25%	6.25%
Liquidation preference per share	$ 1,000	$ 1,000
Preferred stock, shares issued		1,725,000
Preferred stock, shares outstanding		1,725,000
Treasury stock, shares	31,269	31,269

CONDENSED CONSOLIDATED STATEME7

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018		Mar. 31, 2017
Cash Flows From Operating Activities:
Net income	$ 208	[1]	$ 351
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, depletion and amortization	143		106
Amortization of debt issuance costs	2		2
Gain on derivatives, unsettled	(2)		(146)
Stock-based compensation	4		6
Other	3		(1)
Change in assets and liabilities:
Accounts receivable	46		53
Accounts payable	(17)		(13)
Taxes payable	(12)		(8)
Interest payable	(4)		(24)
Other assets and liabilities	(7)		(14)
Net cash provided by operating activities	364		312
Cash Flows From Investing Activities:
Capital investments	(302)		(340)
Proceeds from sale of property and equipment	6		2
Other	2		4
Net cash used in investing activities	(294)		(334)
Cash Flows From Financing Activities:
Payments on current portion of long-term debt			(25)
Change in bank drafts outstanding			6
Preferred stock dividend	(27)
Cash paid for tax withholding	(1)
Net cash used in financing activities	(28)		(19)
Increase (decrease) in cash and cash equivalents	42		(41)
Cash and cash equivalents at beginning of year	916		1,423
Cash and cash equivalents at end of period	$ 958		$ 1,382
[1]	In 2018, deferred tax activity incurred in other comprehensive income was offset by a valuation allowance.

CONDENSED CONSOLIDATED STATEME8

CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - 3 months ended Mar. 31, 2018 - USD ($) $ in Millions		Common Stock Outstanding [Member]	Preferred Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income [Member]	Common Stock in Treasury [Member]	Total
Balance, shares at Dec. 31, 2017		512,134,311	1,725,000
Balance at Dec. 31, 2017		$ 5		$ 4,698	$ (2,679)	$ (44)	$ (1)	$ 1,979
Comprehensive income:
Net income					208			208	[1]
Other comprehensive income
Comprehensive income	[1]							208
Stock-based compensation				7				7
Issuance of common stock, shares		74,998,614
Issuance of common stock		$ 1		(1)
Conversion of preferred stock, shares			(1,725,000)
Issuance of restricted stock, shares		5,076
Cancellation of restricted stock, shares		(160,168)
Performance units vested, shares		214,866
Tax withholding - stock compensation, shares		(338,808)
Tax withholding - stock compensation				(1)				(1)
Balance, shares at Mar. 31, 2018		586,853,891
Balance at Mar. 31, 2018		$ 6		$ 4,703	$ (2,471)	$ (44)	$ (1)	$ 2,193
[1]	In 2018, deferred tax activity incurred in other comprehensive income was offset by a valuation allowance.

Basis of Presentation

Basis of Presentation	3 Months Ended
	Mar. 31, 2018
Basis of Presentation [Abstract]
Basis of Presentation	(1) 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 natural gas gathering and m arketing businesses (“Midstream ”). Southwestern conducts most of its businesses through subsidiaries and operates principally in two segments: E&P and Midstream .  The accompanying unaudited condensed 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 Company believes the disclosures made are adequate to make the information presented not misleading.  The unaudited condensed 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 unaudited condensed 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, 201 7 (“201 7 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 2017 Annual Report.  Certain reclassifications have been made to the prior year financial statements to conform to the 2018 presentation. The effects of the reclassifications were not material to the Company’s unaudited condensed consolidated financial statements. 

Revenue Recognition

Revenue Recognition	3 Months Ended
	Mar. 31, 2018
Revenue Recognition [Abstract]
Revenue Recognition	(2) REVENUE RECOGNITION  Effective January 1, 2018, the Company adopted Accounting Standards Codification (“ ASC ”) 606, “Revenue from Contracts with Customers,” using the modified retrospective method applied to those contracts which were not completed as of January 1, 2018. Under the modified retrospective method, the Company recognizes the cumulative effect of initially applying the new revenue standard as an adjustment to the opening balance of retained earnings; however, no material adjustment was required as a result of adopting ASC 606. Results for reporting periods beginning on January 1, 2018 are presented under the new revenue standard. The comparative information has not been restated and continues to be reported under the accounting standards in effect for those periods. The Company performed an analysis of the impact of adopting ASC 606 across all revenue streams and did not identify any changes to its revenue recognition policies that would result in a material impact to its consolidated financial statements.  Revenues from Contracts with Customers  Natural gas and liquids. Natural gas, crude oil and natural gas liquid (“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, crude 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 to which the Company has a right to invoice and has not disclosed information regarding its rem aining 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 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, generally markets natural gas, crude oil and NGLs for its affiliated E&P companies as well as other joint interest owners who choose to market with Southwestern. In addition, the Company markets some products purchased from third parties. Marketing revenues for natural gas, crude 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. Under the Company’s marketing contracts, the delivery of each unit of natural gas, crude 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, crude 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 to which the Company has a right to invoice and has not disclosed information regarding its rem aining performance obligations.  Gas gathering. In certain areas, the Company, through its gathering affiliate, gathers natural gas pursuant to a variety of contracts with customers, including affiliated E&P companies. The performance obligations for gas gathering services include delivery of each unit of natural gas to the designated delivery point, which may include treating of certain natural gas units to meet interstate pipeline specifications. Revenue is recognized at the point in time when performance obligations are fulfilled. Under the Company’s gathering contracts, customers are invoiced and revenue is recognized each month based on the volume of natural gas transported and treated at a contractually agreed upon price per unit. Payment terms are typically within 30 to 60 days of completion of the performance obligations. 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 to which the Company has a right to invoice and has not disclosed information regarding its rem aining performance obligations. Any imbalances are settled on a monthly basis by cashing-out with the respective shipper. Accordingly, there are no contract assets or contract liabilities related to the Company’s gas gathering revenues.  Disaggregation of Revenues  The Company presents a disaggregation of E&P revenues by product on the condensed consolidated statements of operations net of intersegment revenues. The following table reconciles operating revenues as presented o n the unaudited condensed consolidated statements of operations to the operating revenues by segment:     Intersegment  (in millions) E&P Midstream Revenues Total  Three months ended March 31, 2018  Gas sales $ 535 $ – $ 5 $ 540  Oil sales 34 – 1 35  NGL sales 65 – – 65  Marketing – 829 (576) 253  Gas gathering – 67 (43) 24  Other (1) 3 – – 3  Total $ 637 $ 896 $ (613) $ 920   Three months ended March 31, 2017  Gas sales $ 500 $ – $ 3 $ 503  Oil sales 23 – – 23  NGL sales 40 – – 40  Marketing – 777 (524) 253  Gas gathering – 81 (54) 27  Other – – – –  Total $ 563 $ 858 $ (575) $ 846  (1) Other E &P revenues consists primarily of water sales to third-party operators. 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 Arkansas. Operations in northeast Pennsylvania are referred to as “Northeast Appalachia , ” operations in West Virginia and southwest Pennsylvania are referred to as “Southwest Appalachia” and operations in Arkansas are referred to as the “Fayetteville Shale.”     For the three months ended March 31,  (in millions) 2018 2017  Northeast Appalachia $ 327 $ 253  Southwest Appalachia 156 104  Fayetteville Shale 152 205  Other 2 1  Total $ 637 $ 563  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 unaudited condensed consolidated balance sheet:     (in millions) March 31, 2018 December 31, 2017  Receivables from contracts with customers $ 273 $ 322  Other accounts receivable 109 106  Total accounts receivable $ 382 $ 428   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, 2018 and 2017. 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, 2018
Cash and Cash Equivalents [Abstract]
Cash and Cash Equivalents	(3) CASH AND CASH EQUIVALENTS  The following table presents a summary of cash and cash equivalents as of March 31, 2018 and December 31, 2017:     (in millions) March 31, 2018 December 31, 2017  Cash $ 267 $ 261  Marketable securities (1) 691 605  Other cash equivalents – 50 (2)  Total $ 958 $ 916 (1) Primarily consists of government stable value money market funds. (2) Consists of time deposits.

Natural Gas and Oil Properties

Natural Gas and Oil Properties	3 Months Ended
	Mar. 31, 2018
Natural Gas and Oil Properties [Abstract]
Natural Gas and Oil Properties	(4) 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 futu re net revenues attributable to prove d 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.  Using the average quoted price from the first day of each month from the previous 12 months for Henry Hub natural gas of $3.00 per MMBtu, West Texas Intermediate oil of $49.94 per barrel and NGLs of $14.90 per barrel, adjusted for 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, 2018. The Company had no hedge positions that were designated for hedge accounting as of March 31, 2018. 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.  Using the average quoted price from the first day of each month from the previous 12 months for Henry Hub natural gas of $2.73 per MMBtu, West Texas Intermediate oil of $44.10 per barrel and NGLs of $10.17 per barrel, adjusted for 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, 2017. The Company had no hedge positions that were designated for hedge accounting as of March 31, 2017. 

Earnings Per Share

Earnings Per Share	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Earnings Per Share	(5) EARNINGS PER SHARE  Basic earnings per common share is computed by dividing net income (loss) attributable to common stock 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, performance units and the assumed conversion of mandatory convertible preferred stock. 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 January 2015, the Company issued 34,500,000 depositary shares that entitled the holder to a proportional fractional interest in the rights and preferences of the mandatory convertible preferred stock, including conversion, dividend, liquidation and voting rights. The mandatory convertible preferred stock had the non-forfeitable right to participate on an as-converted basis at the conversion rate then in effect in any common stock dividends declared and as such, is considered a participating security. Accordingly, it has been included in the computation of basic and diluted earnings per share, pursuant to the two-class method. In the calculation of basic earnings per share attributable to common shareholders, participating securities are allocated earnings based on actual dividend distributions received plus a proportionate share of undistributed net income attributable to common shareholders, if any, after recognizing distributed earnings. The Company’s participating securities do not participate in undistributed net losses because they are not contractually obligate d to do so. On January 12, 2018, all outstanding shares of mandatory convertible preferred stock converted to 74,998,614 shares of the Company’s common stock. On December 18, 2017 , the Company declared the quarterly dividend, which was paid to holders of the mandatory convertible preferred stock in cash on January 16, 2018 . Dividends declared in the first, second and third quarters of 2017 were settled partially in common stock for a total of 10,040,306 shares . The following table presents the computation of earnings per share for the three months ended March 31, 2018 and 2017:    For the three months ended March 31,  (in millions, except share/ per share amounts) 2018 2017  Net income $ 208 $ 351  Mandatory convertible preferred stock dividend − 27  Participating securities - mandatory convertible preferred stock 3 43  Net income attributable to common stock $ 205 $ 281   Number of common shares:  Weighted average outstanding 571,297,804 493,068,000  Issued upon assumed exercise of outstanding stock options – 82,845  Effect of issuance of non-vested restricted common stock 914,096 770,429  Effect of issuance of non-vested performance units 1,632,559 573,721  Weighted average and potential dilutive outstanding 573,844,459 494,494,995   Earnings per common share:  Basic $ 0.36 $ 0.57  Diluted $ 0.36 $ 0.57  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, 2018 and 2017 , as they would have had an antidilutive effect:     For the three months ended March 31,  2018 2017  Unexercised stock options − 1,854,004  Unvested share-based payment 5,292,454 1,212,396  Performance units 574,944 –  Mandatory convertible preferred stock 9,999,815 74,999,895  Total 15,867,213 78,066,295 

Derivatives and Risk Management

Derivatives and Risk Management	3 Months Ended
	Mar. 31, 2018
Derivatives and Risk Management [Abstract]
Derivatives and Risk Management	(6) 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, 2018 and December 31, 2017, the Company’s derivative financial instruments consisted of fixed price swaps, two-way costless collars, three-way costless collars, basis swaps, call options 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, t he 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 which, 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, t he 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.  Call options The Company purchases and sells call options in exchange for a premium. 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 i s 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.  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 chooses counterparties for its derivative instruments that it believes are creditworthy at the time the transactions are entered into, and the Company closely monitors the credit ratings of these counterparties. Additionally, the Company performs both quantitative and qualitative assessments of these counterparties based on their credit ratings and credit default swap rates where applicable. However, there can be no assurance that a counterparty will be able to meet its obligations to the Company.  The following table s 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 table s present the notional amount, the weighted average contract prices and the fair value by expected maturity dates as of March 31, 2018 :      Financial Protection on Production Weighted Average Price per MMBtu Fair Value at  Volume (Bcf) Swaps Sold Puts Purchased Puts Sold Calls Basis Differential March 31, 2018 ($ in millions)  Natural gas  2018  Fixed price swaps 215 $ 2.97 $ – $ – $ – $ – $ 33  Two-way costless collars 6 – – 2.90 3.27 – 1  Three-way costless collars 213 – 2.40 2.97 3.37 – 39  Total 434 $ 73  2019  Fixed price swaps 93 $ 3.00 $ – $ – $ – $ – $ 19  Two-way costless collars 53 – – 2.80 2.98 – 6  Three-way costless collars 133 – 2.49 2.93 3.34 – 11  Total 279 $ 36   Basis swaps  2018 73 $ – $ – $ – $ – $ (0.59) $ –  2019 6 – – – – 1.01 (1)  Total 79 $ (1)     Volume (MBbls) Weighted Average Strike Price per Bbl Fair Value at March 31, 2018 ($ in millions)  Propane  2018  Fixed price swaps 1,100 $ 34.64 $ 3   Ethane  2018  Fixed price swaps 413 $ 11.19 $ –  2019  Fixed price swaps 91 $ 11.61 $ –      Other Derivative Contracts  Volume (Bcf) Weighted Average Strike Price per MMBtu Fair Value at March 31, 2018 ($ in millions)  Purchased call options  2020 68 $ 3.63 $ 7  2021 57 3.52 11  Total 125 $ 18   Sold call options  2018 47 $ 3.50 $ (1)  2019 52 3.50 (4)  2020 137 3.39 (21)  2021 114 3.33 (27)  Total 350 $ (53)     Volume (Bcf) Weighted Average Strike Price per MMBtu Basis Differential Fair Value at March 31, 2018 ($ in millions)  Storage (1)  2018  Fixed price swaps 1 $ 2.76 $ – $ –  Basis swaps 1 – (0.88) –  Total 2 $ –  2019  Fixed price swaps 1 $ 3.03 $ – $ –  Basis swaps 1 – (0.44) –  Total 2 $ –  (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 at a later date.  The Company is a party to interest rate swaps that were entered into to mitigate the Company’s exposure to volatility in interest rates. The interest rate swaps have a notional amount of $170 million and expire in June 2020 . The Company did not designate the interest rate swaps for hedge accounting treatment. Changes in the fair value of the interest rate swaps are included in gain (loss) on derivatives on the unaudited condensed consolidated statements of operations.  The balance sheet classification of the assets and liabilities related to derivative financial instruments (none of which are designated for hedge accounting treatment) are summarized below as of March 31 , 201 8 and December 31, 2017 :     Derivative Assets  Balance Sheet Classification Fair Value  March 31, 2018 December 31, 2017  Derivatives not designated as hedging instruments: (in millions)  Fixed price swaps - natural gas Derivative assets $ 34 $ 38  Fixed price swaps - propane Derivative assets 3 –  Two-way costless collars Derivative assets 4 5  Three-way costless collars Derivative assets 63 82  Basis swaps Derivative assets 6 2  Purchased call options Derivative assets – 2  Fixed price swaps - natural gas Other long-term assets 20 18  Two-way costless collars Other long-term assets 12 –  Three-way costless collars Other long-term assets 28 39  Purchased call options Other long-term assets 18 –  Interest rate swaps Other long-term assets 1 –  Total derivative assets $ 189 $ 186 (1)   Derivative Liabilities  Balance Sheet Classification Fair Value  March 31, 2018 December 31, 2017  Derivatives not designated as hedging instruments: (in millions)  Fixed price swaps - natural gas Derivative liabilities $ 2 $ –  Two-way costless collars Derivative liabilities 3 1  Three-way costless collars Derivative liabilities 25 36  Basis swaps Derivative liabilities 7 23  Sold call options Derivative liabilities 3 3  Interest rate swaps Derivative liabilities – 1  Fixed price swaps - natural gas Other long-term liabilities – 1  Two-way costless collars Other long-term liabilities 6 –  Three-way costless collars Other long-term liabilities 16 30  Sold call options Other long-term liabilities 49 15  Total derivative liabilities $ 111 $ 110 (1) Excludes $1 million in premiums paid related to certain call options recognized as a component of derivative assets within current assets on the condensed consolidated balance sheet at December 31, 2017. As certain call options settled, the premium was amortized and recognized as a component of gain (loss) on derivatives on the unaudited condensed statement of operations.  At March 31, 2018 , the net fair value of the Company’s financial instruments related to commodities was a $77 million asset. The net fair value of the Company’s interest rate swaps was a $1 million asset as of March 31, 2018.  Derivative Contracts Not Designated for Hedge Accounting  As of March 31, 2018 , the Company had no positions designated for hedge accounting treatment. Gains and losses on derivatives that are not designated for hedge accounting treatment, or that do not meet hedge accounting requirements, are recorded as a component of gain (loss) on derivatives on the unaudited condensed consolidated statements of operations. Accordingly, the gain (loss) on derivatives component of the statement of operations reflects the gains and losses on both settled and unsettled derivatives. The Company calculates gains and losses on settled derivatives as the summation of gains and losses on positions which have settled within the reporting period. Only the settled gains and losses are included in the Company’s realized commodity price calculations.  The following tables summarize the before-tax effect of the Company’s derivative instruments not designated for hedge accounting on the unaudited condensed consolidated statements of operations for the three months ended March 31, 2018 and 2017 :     Gain (Loss) on Derivatives, Unsettled Recognized in Earnings  Consolidated Statement of Operations For the three months ended  Classification of Gain (Loss) March 31,  Derivative Instrument on Derivatives, Unsettled 2018 2017  (in millions)  Fixed price swaps - natural gas Gain (Loss) on Derivatives $ (3) $ 118  Fixed price swaps - propane Gain (Loss) on Derivatives 3 –  Two-way costless collars Gain (Loss) on Derivatives 3 31  Three-way costless collars Gain (Loss) on Derivatives (5) 57  Basis swaps Gain (Loss) on Derivatives 20 (103)  Purchased call options Gain (Loss) on Derivatives 16 –  Sold call options Gain (Loss) on Derivatives (34) 42  Interest rate swaps Gain (Loss) on Derivatives 2 1  Total gain on unsettled derivatives $ 2 $ 146   Gain (Loss) on Derivatives, Settled (1)  Recognized in Earnings  Consolidated Statement of Operations For the three months ended  Classification of Gain (Loss) March 31,  Derivative Instrument on Derivatives, Settled 2018 2017  (in millions)  Fixed price swaps - natural gas Gain (Loss) on Derivatives $ – $ (16)  Two-way costless collars Gain (Loss) on Derivatives 4 (3)  Three-way costless collars Gain (Loss) on Derivatives 7 (4)  Basis swaps Gain (Loss) on Derivatives (21) (1)  Purchased call options Gain (Loss) on Derivatives 2 (2) –  Sold call options Gain (Loss) on Derivatives (1) (6)  Total loss on settled derivatives $ (9) $ (30)   Total gain (loss) on derivatives $ (7) $ 116  (1) The Company calculates gain (loss) on derivatives, settled, as the summation of gains and losses on positions that settled within the period.  (2) Includes $1 million amortization of premiums paid related to certain call options for the three months ended March 31, 201 8 , which is included in gain (loss) on derivatives on the unaudited condensed consolidated statement s of operation s .

Reclassifications from Accumula

Reclassifications from Accumulated Other Comprehensive Income (Loss)	3 Months Ended
	Mar. 31, 2018
Reclassifications from Accumulated Other Comprehensive Income (Loss) [Abstract]
Reclassifications from Accumulated Other Comprehensive Income (Loss)	 (7) RECLASSIFICATIONS FROM ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS)  The following tables detail the components of accumulated other comprehensive income (loss) and the related tax effects for the three months ended March 31, 2018 :     (in millions) Pension and Other Postretirement Foreign Currency Total  Beginning balance, December 31, 2017 $ (30) $ (14) $ (44)  Other comprehensive income (loss) before reclassifications (1) – – –  Amounts reclassified from other comprehensive income (loss) (1) (2) – – –  Net current-period other comprehensive income (loss) – – –  Ending balance, March 31, 2018 $ (30) $ (14) $ (44) (1) Deferred tax activity related to pension and other postretirement benefits was offset by a valuation allowance, resulting in no tax expense recorded for the period. (2) See separate table below for details about these reclassifications.     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 March 31, 2018  Pension and other postretirement: (in millions)  Amortization of prior service cost and net loss (1) Other Income (Loss), Net $ –  Provision (benefit) for income taxes –  Net income $ –   Total reclassifications for the period Net income $ –  (1) See Note 11 for additional details regarding the Company’s pension and other postretirement benefit plans.    

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2018
Fair Value Measurements [Abstract]
Fair Value Measurements	(8) FAIR VALUE MEASUREMENTS  The carrying amounts and estimated fair values of the Company’s financial instruments as of March 31, 2018 and December 31, 2017 were as follows:     March 31, 2018 December 31, 2017  Carrying Fair Carrying Fair  (in millions) Amount Value Amount Value  Cash and cash equivalents $ 958 $ 958 $ 916 $ 916  2018 term loan facility due December 2020 (1)(2) 1,191 1,191 1,191 1,191  Senior notes (2) 3,242 3,199 3,242 3,358  Derivative instruments, net 78 78 76 (3) 76 (3)  (1) Concurrent with the closing of the new 2018 credit facility agreement, the Company repaid the $1,191 million secured term loan balance on April 26, 2018. See Note 16 – Subsequent Events for more information on the 2018 credit facility.  (2) Excludes unamortized debt issuance costs and debt discounts.  (3) Excludes $1 million in premiums paid related to certain call options recognized as a component of derivatives assets within current assets on the condensed consolidated balance sheet.  The carrying values of cash and cash equivalents, accounts receivable, other current assets, accounts payable and other current liabilities on the unaudited condensed 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 were 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 carrying values of the borrowings under the Company’s term loan facilities and unsecured revolving credit facility (to the extent utilized) approximate fair value because the interest rate is variable and reflective of market rates. The Company considers the fair value of its debt to be a Level 2 measurement on the fair value hierarchy.  Derivative Instruments: The fair value of all derivative instruments is the amount at which the instrument could be exchanged currently between willing parties. The amounts are based on quoted market prices, best estimates obtained from counterparties and an option pricing model, when necessary, for price option contracts.  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 Company has classified its derivatives into these levels depending upon the data utilized to determine their fair values. The Company’s natural gas fixed price swaps (Level 2) are estimated using third-party discounted cash flow calculations using the NYMEX futures index. The Company utilized 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 March 31, 2018 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 3) 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 futures index, interest rates, volatility and credit worthiness. The Company’s basis swaps (Level 3) are estimated using third-party calculations based upon forward commodity price curves.  Inputs to the Black-Scholes model, including the volatility input, which is the significant unobservable input for Level 3 fair value measurements, 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.  Assets and liabilities measured at fair value on a recurring basis are summarized below (in millions):   March 31, 2018  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  Fixed price swap - natural gas assets $ – $ 54 $ – $ 54  Fixed price swap - propane assets – 3 – 3  Two-way costless collar assets – – 16 16  Three-way costless collar assets – – 91 91  Basis swap assets – – 6 6  Purchased call option assets – – 18 18  Interest rate swap assets – 1 – 1  Fixed price swap - natural gas liabilities – (2) – (2)  Two-way costless collar liabilities – – (9) (9)  Three-way costless collar liabilities – – (41) (41)  Basis swap liabilities – – (7) (7)  Sold call option liabilities – – (52) (52)  Total $ – $ 56 $ 22 $ 78     December 31, 2017  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  Fixed price swap assets $ – $ 56 $ – $ 56  Two-way costless collar assets – – 5 5  Three-way costless collar assets – – 121 121  Purchased call option assets – – 2 2  Basis swap assets – – 2 2  Fixed price swap liabilities – (1) – (1)  Two-way costless collar liabilities – – (1) (1)  Three-way costless collar liabilities – – (66) (66)  Basis swap liabilities – – (23) (23)  Sold call option liabilities – – (18) (18)  Interest rate swap liabilities – (1) – (1)  Total $ – $ 54 $ 22 $ 76  The t able below presents reconciliations for the change in net fair value of derivative assets and liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3) for the three months ended March 31, 2018 and 2017 . The fair values of Level 3 derivative instruments are estimated using proprietary valuation models that utilize both market observable and unobservable parameters. Level 3 instruments presented in the table consist of net derivatives valued using pricing models incorporating assumptions that, in the Company’s judgment, reflect reasonable assumptions a marketplace participant would have used as of March 31, 2018 and 2017 .     For the three months ended  March 31,  (in millions) 2018 2017  Balance at beginning of period $ 22 $ (195)  Total gains (losses):  Included in earnings (9) 13  Settlements (1) 9 14  Transfers into/out of Level 3 – –  Balance at end of period $ 22 $ (168)  Change in gains included in earnings relating to derivatives still held as of March 31 $ – $ 27  (1) Includes $1 million amortization of premiums paid related to certain call options for the three months ended March 31, 2018. 

Debt

Debt	3 Months Ended
	Mar. 31, 2018
Debt [Abstract]
Debt	(9) DEBT  The components of debt as of March 31, 2018 and December 31, 2017 consisted of the following:    March 31, 2018  (in millions) Debt Instrument Unamortized Issuance Expense Unamortized Debt Discount Total  Variable rate ( 4.240% at March 31, 2018) 2016 term loan facility, due December 2020 (1) $ 1,191 $ (8) $ − $ 1,183  4.05% Senior Notes due January 2020 (2) 92 − − 92  4.10% Senior Notes due March 2022 1,000 (6) − 994  4.95% Senior Notes due January 2025 (2) 1,000 (8) (2) 990  7.50 % Senior Notes due April 2026 650 (9) − 641  7.75 % Senior Notes due October 2027 500 (7) − 493  Total debt $ 4,433 $ (38) $ (2) $ 4,393      December 31, 2017  (in millions) Debt Instrument Unamortized Issuance Expense Unamortized Debt Discount Total  Variable rate ( 3.980% at December 31, 2017) 2016 term loan facility, due December 2020 (1) $ 1,191 $ (8) $ − $ 1,183  4.05% Senior Notes due January 2020 (2) 92 − – 92  4.10% Senior Notes due March 2022 1,000 (7) – 993  4.95% Senior Notes due January 2025 (2) 1,000 (8) (2) 990  7.50% Senior Notes due April 2026 650 (10) − 640  7.75% Senior Notes due October 2027 500 (7) – 493  Total debt $ 4,433 $ (40) $ (2) $ 4,391  (1) Concurrent with the closing of the new 2018 credit facility agreement on April 26, 2018, the Company repaid the $1,191 million secured term loan balance with cash on hand and borrowings under the new credit facility. The Company’s initial borrowings under the 2018 credit facility were $360 m illion, a portion of which related to other working capital needs. See Note 16 – Subsequent Events for more information on the 2018 credit facility.  (2) In February and June 2016, Moody’s and S&P downgraded certain senior notes, increasing the interest rates by 175 basis points effective July 2016. As a result of the downgrades, interest rates increased to 5.80% for the 2020 Notes and 6.70% for the 2025 Notes.  Senior Notes  In January 2015, the Company completed a public offering of $350 million aggregate principal amount of its 3.30% senior notes due 2018 (the “2018 Notes”), $850 million aggregate principal amount of its 4.05% senior notes due 2020 (the “2020 Notes”) and $1.0 billion aggregate principal amount of its 4.95% senior notes due 2025 (the “2025 Notes” together with the 2018 and 2020 Notes, the “Notes”), with net proceeds from the offering totaling approximately $2.2 billion after underwriting discounts and offering expenses. The interest rates on the Notes are determined based upon the public bond ratings from Moody’s and S&P. Downgrades on the 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 interes t payment. In February and June 2016, Moody’s and S&P downgraded the Notes, increasing the interest rates by 175 basis points effective July 2016. As a result of these downgrades, interest rates increased to 5.80% for the 2020 Notes and 6.70% for the 2025 Notes. In the event of future downgrades, the coupons for this series of notes are capped at 6.05% and 6.95% , respectively. The first coupon payment to the bondholders at the higher interest rates was paid in January 2017.  During the first half of 2017, the Company redeemed or repurchased (i) $38 million principal amount of its outstanding 2018 Notes, (ii) $212 million principal amount of its outstanding 7.50% Senior Notes due February 2018 and (iii) $26 million principal amount of its outstanding 7.15% Senior Notes due June 2018 , and recognized an $11 million loss on the extinguishm ent of debt, $1 million of which was recognized in the three months ended March 31, 2017 and reported in other income (loss), net on the unaudited condensed consolidated statements of operations.  In September 2017, the Company completed a public offering of $650 million aggregate principal amount of its 7.50% senior notes due 2026 (the “2026 Notes”) and $500 million aggregate principal amount of its 7.75% senior notes due 2027 (the “2027 Notes”), with net proceeds from the offering totaling approximately $1.1 billion after underwriting discounts and offering expenses. Both series of senior notes were sold to the public at face value. The proceeds from this offering were used to purchase $758 million of the Company’s 2020 Notes in a tender offer and to repay the outstanding balance of $327 million on the Company’s 2015 t erm l oan. The Company recognized a loss on extinguishment of debt of $59 million, which included $53 million of premiums paid.  In October 2017, the Company retired $40 million principal amount outstanding on its 2017 senior notes.  In November 2017, the Company solicited and received consent to amend certain restrictive covenants contained in the indentures governing the Company’s 2022 Notes and the 2025 Notes. These amendments conform certain covenants of the 2022 Notes and 2025 Notes to all other series of senior notes.  201 8 Credit Facility  On April 26, 2018 the Company replaced its 2016 credit facility with a new credit facility . S ee Note 16 – Subsequent Events for more information on the new credit facility.  2016 Credit Facility  In June 2016, the Company reduced its existing $2.0 billion unsecured revolving credit facility entered into in December 2013 to $66 million and entered into a new credit agreement for $1,934 million, consisting of a $1,191 million secured term loan and a new $743 million unsecured revolving credit facility, matur ing in December 2020 . At March 31, 2018 t he $1,191 million secured term loan wa s fully drawn and there were no borrowings under either revolving credit facility; however, $323 million in letters of credit was outstanding under th e 2016 revolving credit facility. Concurrent with the closing of the new 2018 credit facility agreement on April 26, 2018, the Company repaid the $1,191 million secured term loan balance. See Note 16 – Subsequent Events for more information on the 2018 credit facility.  Loans under the 2016 credit agreement were subject to varying rates of interest based on whether the loan was a Eurodollar loan or an alternate base rate loan. Eurodollar loans b ore interest at the Eurodollar rate, which was adjusted LIBOR plus applicable margins ranging from 1.750% to 2.500% . Alternate base rate loans b ore interest at the alternate base rate plus the applicable margin ranging from 0.750% to 1.500% . The interest rate on the term loan was determined based upon the Company’s public debt ratings and was 250 basis points over LIBOR as of March 31, 2018 .  The 2016 term loan and revolving credit facility contain ed financial covenants that impose d certain restrictions on the Company. In September 2017, the Company and the lenders amended the 2016 credit agreement to reflect the following:  · I ncrease d the minimum interest coverage ratio to 2.00x c ommencing with the fiscal quarter ended June 30, 2017 and continued over the life of the 2016 Credit Agreement;  · Modified the minimum liquidity covenant such that either (1) if leverage wa s less than 4.00x or if the 2016 revolving credit facility has been terminated, there would be no minimum liquidity covenant, or (2) the Company could elect to replace the minimum liquidity covenant with a maximum leverage ratio of no more than 5.00x for the fiscal quarters ending March 31, 2018 and June 30, 2018 and 4.50x thereafter; and  · M odif ied the mandatory prepayment and commitment reduction provisions to permit the Company to retain the first $500 million of net cash proceeds from asset sales that would have otherwise been required to prepay amounts outstanding under the 2016 revolving credit facility and/or reduce commitments under the 2016 revolving credit facility.  As of March 31, 2018 , the Company ha d not elected to replace the minimum liquidity covenant with a maximum leverage covenant. Therefore, under the credit agreement as amended in September 2017 , should the leverage ratio have exceed ed 4.0 0 x, the Company would have be en subject to a minimum liquidity requirement of $300 million. The financial covenant with respect to the maximum leverage ratio consist ed of total debt divided by EBITDAX. The financial covenant with respect to minimum interest coverage consist ed of EBITDAX divided by consolidated interest expense. EBITDAX, as defined in the Company’s 2016 credit agreement, exclude d the effects of interest expense, income taxes, depreciation, depletion and amortization, 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. Collateral for the secured term loan wa s principally the Company’s E&P properties in the Fayetteville Shale area, the equity of its subsidiaries and cash and marketable securities on hand, and the credit agreement require d a minimum collateral coverage ratio of 1.50x for the 2016 secured term loan. This collateral could also have support ed all or a part of revolving credit extensions depending on restrictions in the Company’s senior notes indentures.  As of March 31, 2018 , the Company was in compliance with all of the coven ants of this credit agreement.  2013 Credit Facility  In December 2013, the Company entered into a credit agreement that exchanged its previous revol ving credit facility. Under the revolving credit facility, the Company had a borrowing capacity of $2.0 billion. The revolving credit facility was unsecured and was not guaranteed by any subsidiaries. In June 2016, this credit facility was substantially exchanged for a new credit facility comprised of a $1,191 million secured term loan and a new $743 million revolving credit facility. The borrowing capacity of the original 2013 credit agreement was reduced from $2.0 billion to $66 million, remain ed unsecured and the maturity remain ed December 2018 . As of March 31, 2018 , there were no borrowings under this facility.  The existing unsecured 2013 revolving credit facilit y includes a f inancial covenant under which the Company may not have total debt in excess of 60% of its total adjusted book capital. This financial covenant with respect to capitalization percentages exclude s the effects of any full cost ceiling impairments, certain hedging activities and the Company’s pension and other postretirement liabilities. At March 31, 2018 , debt constitute d 29% o f the Company’s adjusted book capital.  On April 26, 2018 the Company replaced its 2016 credit facility with a new credit facility . Concurrently, the 2013 credit facility was terminated. S ee Note 16 – Subsequent Events for more information on the new credit facility. 

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2018
Commitments and Contingencies [Abstract]
Commitments and Contingencies	(10) COMMITMENTS AND CONTINGENCIES  Operating Commitments and Contingencies  As of March 31, 2018 , 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 $9.1 billion, $3.1 billion 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 $832 million of that amount. As of March 31, 2018, future payments under non-cancelable firm transportation and gathering agree ments were as follows:     Payments Due by Period  Less than 1 More than 8  (in millions) Total Year 1 to 3 Years 3 to 5 Years 5 to 8 Years Years  Infrastructure Currently in Service $ 5,986 $ 639 $ 1,208 $ 894 $ 1,151 $ 2,094  Pending Regulatory Approval and/or Construction (1) 3,139 46 317 389 626 1,761  Total Transportation Charges $ 9,125 $ 685 $ 1,525 $ 1,283 $ 1,777 $ 3,855 (1) Based on estimated in-service dates as of March 31, 2018.  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 or results of operations of the Company.  Litigation  The Company is subject to various litigation, claims and proceedings that 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 such items when a liability is both probable and the amount can be reasonably estimated. 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.  Arkansas Royalty Litigation  In June 2017, the jury returned a verdict in favor of the Company on all counts in Smith v. SEECO, Inc. et al. , a class action in the United States District Court for the Eastern District of Arkansas. The plaintiff had alleged that the Company had underpaid lessors of lands in Arkansas by deducting from royalty payments costs for gathering, transportation and compression of natural gas in excess of what is permitted by the relevant leases and asserted claims for, among other things, breach of contract, fraud, civil conspiracy, unjust enrichment and violation of certain Arkansas statutes. Following the verdict, the court entered judgment in favor of the Company on all claims. The trial court denied the plaintiff’s motion for a new trial, and the plaintiff has filed a notice of appeal with the United States Court of Appeals for the Eighth Circuit. The court of appeals has not yet determined whether to hear oral argument. Independent of the plaintiff’s appeal, several different parties sought to intervene in the Smith case prior to or shortly after trial, and have appealed the trial court’s order denying their request to intervene. Briefing is complete in the intervenor’s appeal, and oral argument is expected to occur sometime in the second quarter of 2018.  The plaintiff class in Smith comprises the vast majority of lessors of lands in Arkansas for which leases permit deductions for these types of costs. Most of the remaining lessors are named plaintiffs or members of classes in other pending lawsuits. In particular, two actions on behalf of certified classes of only Arkansas residents pending in state courts in Arkansas ( one is set for trial during the third quarter of 2018; the other does not have a trial date) and three cases (all currently stayed) that were filed in Arkansas state court on behalf of a total of 248 individually named plaintiffs, two of which have been removed to federal court, have been assigned to the same court that held the Smith trial. Management believes that, as the Smith jury concluded, the deductions from royalty payments were calculated in accordance with the leases. The Company currently does not anticipate that these other cases are likely to have a material adverse effect on the results of operations, financial position or cash flows of the Company.  Indemnifications  The Company provides certain indemnifications in relation to dispositions of assets. These indemnifications typically relate to disputes, litigation or tax matters existing at the date of disposition. No material liabilities have been recognized in connection with these indemnifications. 

Pension Plan and Other Postreti

Pension Plan and Other Postretirement Benefits	3 Months Ended
	Mar. 31, 2018
Pension Plan and Other Postretirement Benefits [Abstract]
Pension Plan and Other Postretirement Benefits	(11) PENSION PLAN AND OTHER POSTRETIREMENT BENEFITS  The Company maintains defined pension and postretirement benefit plans, which cover substantially all of the Company’s employees. Net periodic pension costs include the following components for the three months ended March 31, 2018 and 2017 :    Pension Benefits  Condensed Consolidated Statement s of For the three months ended  Operations Classification of March 31,  (in millions) Net Periodic Benefit Cost (1) 2018 2017  Service cost General and administrative expenses $ 3 $ 2  Interest cost Other Income (Loss), Net 2 1  Expected return on plan assets Other Income (Loss), Net (2) (1)  Amortization of prior service cost Other Income (Loss), Net − −  Amortization of net loss Other Income (Loss), Net – 1  Net periodic benefit cost $ 3 $ 3  (1) In the first quarter of 2018, the Company adopted Accounting Standards Update No. 2017-07, which requires the service cost component to be disaggregated from the other components of net benefit cost, which are to be presented outside of income from operations. See Note 15 – New Accounting Pronouncements for more information regarding this update.  The Company’s other postretirement benefit plan had a net periodic benefit cost of $1 million for the three months ended March 31, 2018 and 2017 .  As of March 31, 2018 , the Company has contribute d $3 m illion to the pension and other post retirement benefit plans in 2018 . The Company expects to contribute an additional $9 million to its pension plan during the remainder of 201 8 . The Company recognized a liability o f $41 million and $18 mi llion related to its pension and other postretirement benefits, respectively, as of March 31, 2018, compared to a liability of $42 million and $17 million as of December 31, 2017 .  The Company maintains a non-qualified deferred compensation supplemental retirement savings plan (“Non-Qualified Plan”) for certain key employees who may elect to defer and contribute a portion of their compensation, as permitted by the Non-Qualified Plan. Shares of the Company’s common stock purchased under the terms of the Non-Qualified Plan are presented as treasury stock and totaled 31,269 shares at March 31, 2018 and December 31, 2017. 

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2018
Stock-Based Compensation [Abstract]
Stock-Based Compensation	   (12) STOCK-BASED COMPENSATION  The Compa ny recognized the following amounts in total employee stock-based compensation costs for the three months ended March 31, 2018 and 2017 :     For the three months ended March 31, (in millions) 2018 2017  Stock-based compensation cost – expensed $ 5 $ 6  Stock-based compensation cost – capitalized $ 3 $ 4  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 expen se and capital ized expense on a straight-line basis over the vesting period of the award. 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 capital ized expense over th e vesting period of the award.  Equity Awards  The Compa ny recognized the following amounts in employee equity-classified stock-based compensation costs for the three months ended March 31, 2018 and 2017 :    For the three months ended March 31,  (in millions) 2018 2017  Equity-classified stock-based compensation cost – expensed $ 4 $ 6  Equity-classified stock-based compensation cost – capitalized $ 3 $ 4  As of March 31, 2018 , the re was $49 million of tota l 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 2 years.  Equity-Classified Stock Options  The following table summarizes equity-classified stock option activity for the three months ended March 31, 2018 and provides information for options outstanding and options exercisable as of March 31, 2018 :     Number Weighted Average  of Options Exercise Price  (in thousands)  Outstanding at December 31, 2017 6,020 $ 19.43  Granted − −  Exercised – –  Forfeited or expired (3) 38.65  Outstanding at March 31, 2018 6,017 $ 19.42  Exercisable at March 31, 2018 4,379 $ 23.80  Equity-Classified Restricted Stock  The following table summarizes equity-classified restri cted stock activity for the three months ended March 31, 2018 and provides information for unvested shares as of March 31, 2018 :     Number Weighted Average  of Shares Fair Value  (in thousands)  Unvested shares at December 31, 2017 6,254 $ 8.85  Granted 5 5.91  Vested (1,033) 8.77  Forfeited (160) 9.07  Unvested shares at March 31, 2018 5,066 $ 8.85  Equity-Classified Performance Units  The following table summarizes equity-classified performance unit activity for the three months ended March 31, 2018 and provides information for unvested units as of March 31, 2018 . The performance unit awards granted in 2015, 2016 and 2017 include a market condition based exclusively on t he fair valu e of the Total Shareholder Return (“TSR”), as calculated by a Monte Carlo model. The total fair value of the performance units is amortized to compensation expense on a straight line basis over the vesting period of the award. The grant date fair value is calculated using the closing price of the Company’s common stock at the grant date.     Number Weighted Average  of Units (1) Fair Value  (in thousands)  Unvested units at December 31, 2017 1,084 $ 10.12  Granted − −  Vested − −  Forfeited (18) 9.99  Unvested units at March 31, 2018 1,066 $ 10.12 (1) These amounts reflect the number of performance units granted in thousands. The actual payout of shares may range from a minimum of zero shares to a maximum of two s hares per unit contingent upon TSR . The performance units have a three -year vesting term and the actual disbursement of shares, if any, is determined during the first quarter following the end of the three-year vesting period.  Liability Awards  The Compa ny recognized the following amounts in employee liability-classified stock-based compensation costs for the three months ended March 31, 2018 and 2017 :     For the three months ended March 31, (in millions) 2018  Liability-classified s tock-based compensation cost – expensed $ 1  Liability-classified s tock-based compensation cost – capitalized (1) $ –  (1) For the three months ended March 31, 2018, the liability-classified stock-based compensation amount capitalized was less than $1 million.  Liability-Classified Restricted Stock  In the first quar ter of 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 Company has accounted for these as liability-classified awards and as such, 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, 2018, the Company had approximately 12 million unvested liability-classified restricted stock units with a tota l unr ecognized compensation cost of $51 million. This cost is expected to be recognized over a weighted-average period of four ye ars.  Liability-Classified Performance Units  In the first quar ter of 2018, the Company granted performance units that vest 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 as such, 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 201 8 include a performance condition based on cash flow per debt-adjusted share and two market condition s, one based on absolute TSR and the other on relative TSR as compared to a group of the Company’s peers, collectively the “Performance Measures.” The fair values of the two market conditions are calculated by Monte Carlo models on a quarterly basis. As of March 31, 2018, the Company had approximately 3 million unvested liability-classified performance units with a tota l unrecognized compensation cost of $14 million . This cost is expected to be recognized over a weighted-average period of three years. The final value of the performance unit awards is contingent upon the Company’s actual performance against the Performance Measures.  

Segment Information

Segment Information	3 Months Ended
	Mar. 31, 2018
Segment Information [Abstract]
Segment Information	 (13) 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 Midstream segment generates revenue through the marketing of both Company and third-party produced natural gas and liquids volumes and through gathering fees associated with the transportation of natural gas to market.  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 201 7 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 and other income (loss). The “Other” column includes items not related to the Company’s reportable segments, including real estate and corporate items.     E&P Midstream Other Total  Three months ended March 31, 2018: (in millions)  Revenues from external customers $ 643 $ 277 $ – $ 920  Intersegment revenues (6) 619 – 613  Depreciation, depletion and amortization expense 117 26 ( 1 ) – 143  Operating income 238 17 – 255  Interest expense (2) 39 – – 39  Loss on derivatives (7) – – (7)  Other income (loss), net – (1) – (1)  Assets 5,346 1,217 1,150 (3) 7,713  Capital investments (4) 334 4 – 338   Three months ended March 31, 2017:  Revenues from external customers $ 566 $ 280 $ – $ 846  Intersegment revenues (3) 578 – 575  Depreciation, depletion and amortization expense 90 16 – 106  Operating income 225 41 – 266  Interest expense (2) 32 – – 32  Gain on derivatives 116 – – 116  Other income, net 2 – (1) 1  Assets 4,413 1,268 1,515 (3) 7,196  Capital investments (4) 283 6 1 290  (1) Includes a $10 million impairment related to certain non-core gathering asset s.  (2) Interest expense by segment is an allocation of corporate amounts as they are incurred at the corporate level.  (3) Other assets represent corporate assets not allocated to segments and assets for non-reportable segments. At March 31, 2018 and 2017, other assets includes approximately $958 million and $1.4 billion in cash and cash equivalents, respectively.  (4) Capital investments includes an increase of $33 million and a decrease of $52 m illion for the three months ended March 31, 2018 and 2017, respectively, relating to the change in ca pital accruals between periods.  Included in intersegment revenues of the Midstream segment are $576 million and $524 million for the three months ended March 31, 2018 and 2017, respectively for marketing of the Company’s E&P sales. Corporate assets include cash and cash equivalents, furniture and fixtures and other costs. Corporate general and administrative costs, depreciation expense and taxes , other than income taxes, are allocated to the segments. 

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2018
Income Taxes [Abstract]
Income Taxes	(14) INCOME TAXES  The Company’s effective tax rate was approximately 0% for the three months ended March 31, 2018 and 2017 primarily as a result of the recognition of a valuation allowance . 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 the current and forecasted business economics of the oil and gas industry.  The Company maintained its net deferred tax asset position at March 31, 2018 primarily due to the write-downs of the carrying value of natural gas and oil properties in 2015 and 2016. The Company recorded decreases in its valuation allowance of $5 1 million and $ 75 million for the three months ended March 31, 2018 and 2017, respectively. Management assesses the available positive and negative evidence to estimate whether sufficient future taxable income will be generated to permit the use of deferred tax assets. In management’s view, the cumulative loss incurred over recent years outweighs any positive factors, such as the possibility of future growth. The amount of the deferred tax assets considered realizable, however, could be adjusted if estimates of future taxable income are increased or if objective negative evidence in the form of cumulative losses is no longer present and additional weight is given to subjective evidence such as future expected growth.  On December 22, 2017 the Tax Cuts and Jobs Act (Tax Reform) was enacted , which made significant changes to the U.S. federal income tax law affecting the Company. Major changes in this legislation applicable to the Company relate to the reduction in tax rate for corporations to 21% , repeal of the corporate alternative minimum tax, interest deductibility and net operating loss carryforward limitations, changes to certain executive compensation and full expensing provisions related to business assets. The Company included tax reform impacts in its 2017 Annual Report and continues to examine the impact of this legislation and future regulations. The first quarter 2018 tax accrual calculated under the estimated annual effective tax rate method reflects the law changes that are effective January 1, 2018. Due to the tax valuation allowance currently in place, any adjustments required to deferred taxes in the current interim period would be fully offset by valuation allowance adjustments and are immaterial to the financial statements.  In February 2018, the FASB issued Accounting Standards Update No. 2018-02 amend ing the FASB Accounting Standards relating to tax effects in accumulated other comprehensive income . See Note 15 – New Accounting Pronouncements for more information regarding this update. 

New Accounting Pronouncements

New Accounting Pronouncements	3 Months Ended
	Mar. 31, 2018
New Accounting Pronouncements [Abstract]
New Accounting Pronouncements	(15) NEW ACCOUNTING PRONOUNCEMENTS  New Accounting Standards Implemented  In May 2014, the FASB issued Accounting Standards Update No. 2014-09, Revenue with Contracts from Customers (Topic 606) (ASC 606, as subsequently amended). ASC 606 supersedes the revenue recognition requirements in Topic 605, Revenue Recognition, and requires entities to recognize revenue when control of the promised goods or services is transferred to customers at an amount that reflects the consideration to which an entity expects to be entitled to in exchange for those goods and services. For public entities, ASC 606 became effective for fiscal years beginning after December 15, 2017. The Company adopted ASC 606 with an effective date of January 1, 2018 using the modified retrospective approach. The adoption of this standard did not have a material effect on the Company’s unaudited condensed consolidated results of operations, financial position or cash flows. Additional disclosures regarding the nature, amount, timing and uncertainty of revenue and cash flow from contracts with customers are available in Note 2 –Revenue Recognition .  In March 2017, the FASB issued Accounting Standards Update No. 2017-07, Compensation - Retirement Benefits (Topic 715) (“Update 2017-07”), which provides additional guidance on the presentation of net benefit cost in the statement of operations and on the components eligible for capitalization in assets. The guidance requires employers to disaggregate the service cost component from the other components of net benefit cost. The service cost component of the net periodic benefit cost shall be reported in the same line item as other compensation costs arising from services rendered by the employees during the period, except for amounts capitalized. All other components of net benefit cost shall be presented outside of a subtotal for income from operations. The Company adopted Update 2017-07 during the first quarter of 2018 resulting in no material impact to its unaudited condensed consolidated statements of operations, financial position or cash flows. The non-service cost components of net periodic benefit cost are presented as a component of Other Income (Loss), Net for the three months ended March 31, 2018 and 2017, and are disclosed in Note 11 – Pension Plan and Other Postretirement Benefits . The Company ceased capitalizing the non-service cost components of net periodic benefit costs prospectively as of the beginning of the first quarter of 2018.  In August 2016, the FASB issued Accounting Standards Update No. 2016-15, Statement of Cash Flows (Topic 230) (“Update 2016-15”), which seeks to reduce the existing diversity in practice in how certain cash receipts and cash payments are presented and classified in the statement of cash flows. The Company adopted this Update during the first quarter of 2018 resulting in no impact on its unaudited condensed consolidated statements of cash flows.  In February 2018, the FASB issued Accounting Standards Update No. 2018-02 that will amend the FASB Accounting Standards relating to tax effects in accumulated other comprehensive income (Topic 220) (“Update 2018-02”) . U pdate 2018-02 permits a company to reclassify the stranded income tax effects of the Tax Cuts and Jobs Act of 2017 on items within accumulated comprehensive income to retained earnings. Although the amendments in Update 2018-02 are effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years, the Company has elected to early adopt the amendments of Update 2018-02 for the current period. The implementation did not have a material impact on the Company’s unaudited condensed consolidated statement of o perations, financial position or cash flows due to the tax valuation allowance currently in place. Any a djustments required under this U pdate would be fully offset by valuation allowance adjustments for both continuing operations and accumulated other comprehensive income.  New Accounting Standards Not Yet Implemented  In February 2016, the FASB issued Accounting Standards Update No. 2016-02, Leases (Topic 842) (“Update 2016-02”), which seeks to increase transparency and comparability among organizations by, among other things, recognizing lease assets and lease liabilities on the balance sheet for leases classified as operating leases under previous GAAP and disclosing key information about leasing arrangements. The codification was amended through additional ASUs. Through March 2018 , the Company made progress on contract reviews, drafting its accounting policies and evaluating the new disclosure requirements. The Company will continue assessing the effect that Update 2016-02 and related ASUs may have on its consolidated financial statements and related disclosures, and anticipates that its assessment will be complete in 2018. For public entities, Update 2016-02 becomes effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years, with early adoption permitted. 

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2018
Subsequent Events [Abstract]
Subsequent Events	(16) SUBSEQUENT EVENTS  On April 26, 2018, as part of the Company’s strategic effort to simplify the capital structure, increase financial flexibility and reduce costs, the Company replaced its 2016 credit facility (which consisted of a $1,191 million secured term loan and an unsecured $743 million revolving credit facility) with a new credit facility (the “2018 credit facility”), with initial aggregate commitments of $2,000 million, an initial borrowing base of $3,200 million and an aggregate maximum revolving credit amount of $3,500 million. The 2018 credit facility is secured by substantially all of the assets owned by the Company and its subsidiaries.  The 2018 credit facility matures on April 26, 2023 , provided that if the Company has not amended, redeemed or refinanced at least $700 million of its 2022 Senior Notes on or before December 14, 2021, the 2018 credit facility will mature on December 14, 2021 .  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 LIBO R 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 ranges from 1.50% to 2.50% based on the Company’s utilization of the borrowing base under 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 ranges from 0.50% to 1.50% based on the Company’s utilization of the borrowing base under 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 c urrent r atio 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 t otal n et l everage r atio of no less than (i) with respect to each fiscal quarter ending during the period from June 30, 2018 through March 31, 2019, 4.50 to 1.00, (ii) with respect to each fiscal quarter ending during the period from June 30, 2019 through March 31, 2020, 4.25 to 1.00, and (iii) 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 Company’s 201 8 credit agreement, exclude s 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 s ales, 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.  The foregoing description of the 2018 credit facility is a summary only and is qualified in its entirety by reference to the Credit Agreement, a copy of which is attached as Exhibits 10.1, to the Company’s Current Report on Form 8-K dated April 26, 2018, and is incorporated herein by reference.  Pursuant to requirements under the indentures governing its senior notes, the Company will cause each subsidiary that becomes a guarantor of the 2018 credit facility to also become a guarantor of each of the Company’s senior notes.  Concurrent with the closing of the 2018 credit facility agreement, the Company repaid the $1,191 million secured term loan balance with cash on hand and borrowings under the new credit facility. The Company’s initial borrowings under the 2018 credit facility were $360 million , a portion of which related to other working capital need s . Additionally, the $323 million in letters of credit outstanding under th e 2016 revolving credit facility at March 31, 2018 were converted to letters of credit under the new 2018 credit facility. 

Revenue Recognition (Tables)

Revenue Recognition (Tables)	3 Months Ended
	Mar. 31, 2018
Revenue Recognition [Abstract]
Disaggregation of Revenue by Segment	  Intersegment  (in millions) E&P Midstream Revenues Total  Three months ended March 31, 2018  Gas sales $ 535 $ – $ 5 $ 540  Oil sales 34 – 1 35  NGL sales 65 – – 65  Marketing – 829 (576) 253  Gas gathering – 67 (43) 24  Other (1) 3 – – 3  Total $ 637 $ 896 $ (613) $ 920   Three months ended March 31, 2017  Gas sales $ 500 $ – $ 3 $ 503  Oil sales 23 – – 23  NGL sales 40 – – 40  Marketing – 777 (524) 253  Gas gathering – 81 (54) 27  Other – – – –  Total $ 563 $ 858 $ (575) $ 846  (1) Other E &P revenues consists primarily of water sales to third-party operators.
Disaggregation of Revenue on Geographic Basis	  For the three months ended March 31,  (in millions) 2018 2017  Northeast Appalachia $ 327 $ 253  Southwest Appalachia 156 104  Fayetteville Shale 152 205  Other 2 1  Total $ 637 $ 563 
Reconciliation of Accounts Receivable	   (in millions) March 31, 2018 December 31, 2017  Receivables from contracts with customers $ 273 $ 322  Other accounts receivable 109 106  Total accounts receivable $ 382 $ 428 

Cash and Cash Equivalents (Tabl

Cash and Cash Equivalents (Tables)	3 Months Ended
	Mar. 31, 2018
Cash and Cash Equivalents [Abstract]
Summary of Cash and Cash Equivalents	   (in millions) March 31, 2018 December 31, 2017  Cash $ 267 $ 261  Marketable securities (1) 691 605  Other cash equivalents – 50 (2)  Total $ 958 $ 916 (1) Primarily consists of government stable value money market funds. (2) Consists of time deposits.

Earnings Per Share (Tables)

Earnings Per Share (Tables)	3 Months Ended
	Mar. 31, 2018
Earnings Per Share [Abstract]
Schedule of Earnings Per Share	  For the three months ended March 31,  (in millions, except share/ per share amounts) 2018 2017  Net income $ 208 $ 351  Mandatory convertible preferred stock dividend − 27  Participating securities - mandatory convertible preferred stock 3 43  Net income attributable to common stock $ 205 $ 281   Number of common shares:  Weighted average outstanding 571,297,804 493,068,000  Issued upon assumed exercise of outstanding stock options – 82,845  Effect of issuance of non-vested restricted common stock 914,096 770,429  Effect of issuance of non-vested performance units 1,632,559 573,721  Weighted average and potential dilutive outstanding 573,844,459 494,494,995   Earnings per common share:  Basic $ 0.36 $ 0.57  Diluted $ 0.36 $ 0.57 
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	  For the three months ended March 31,  2018 2017  Unexercised stock options − 1,854,004  Unvested share-based payment 5,292,454 1,212,396  Performance units 574,944 –  Mandatory convertible preferred stock 9,999,815 74,999,895  Total 15,867,213 78,066,295 

Derivatives and Risk Manageme28

Derivatives and Risk Management (Tables)	3 Months Ended
	Mar. 31, 2018
Derivatives and Risk Management [Abstract]
Schedule of Derivative Instruments, Notional Amount, Weighted Average Contract Prices and Fair Value	   Financial Protection on Production Weighted Average Price per MMBtu Fair Value at  Volume (Bcf) Swaps Sold Puts Purchased Puts Sold Calls Basis Differential March 31, 2018 ($ in millions)  Natural gas  2018  Fixed price swaps 215 $ 2.97 $ – $ – $ – $ – $ 33  Two-way costless collars 6 – – 2.90 3.27 – 1  Three-way costless collars 213 – 2.40 2.97 3.37 – 39  Total 434 $ 73  2019  Fixed price swaps 93 $ 3.00 $ – $ – $ – $ – $ 19  Two-way costless collars 53 – – 2.80 2.98 – 6  Three-way costless collars 133 – 2.49 2.93 3.34 – 11  Total 279 $ 36   Basis swaps  2018 73 $ – $ – $ – $ – $ (0.59) $ –  2019 6 – – – – 1.01 (1)  Total 79 $ (1)     Volume (MBbls) Weighted Average Strike Price per Bbl Fair Value at March 31, 2018 ($ in millions)  Propane  2018  Fixed price swaps 1,100 $ 34.64 $ 3   Ethane  2018  Fixed price swaps 413 $ 11.19 $ –  2019  Fixed price swaps 91 $ 11.61 $ –      Other Derivative Contracts  Volume (Bcf) Weighted Average Strike Price per MMBtu Fair Value at March 31, 2018 ($ in millions)  Purchased call options  2020 68 $ 3.63 $ 7  2021 57 3.52 11  Total 125 $ 18   Sold call options  2018 47 $ 3.50 $ (1)  2019 52 3.50 (4)  2020 137 3.39 (21)  2021 114 3.33 (27)  Total 350 $ (53)     Volume (Bcf) Weighted Average Strike Price per MMBtu Basis Differential Fair Value at March 31, 2018 ($ in millions)  Storage (1)  2018  Fixed price swaps 1 $ 2.76 $ – $ –  Basis swaps 1 – (0.88) –  Total 2 $ –  2019  Fixed price swaps 1 $ 3.03 $ – $ –  Basis swaps 1 – (0.44) –  Total 2 $ –  (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 at a later date.
Balance Sheet Classification of Derivative Financial Instruments	  Derivative Assets  Balance Sheet Classification Fair Value  March 31, 2018 December 31, 2017  Derivatives not designated as hedging instruments: (in millions)  Fixed price swaps - natural gas Derivative assets $ 34 $ 38  Fixed price swaps - propane Derivative assets 3 –  Two-way costless collars Derivative assets 4 5  Three-way costless collars Derivative assets 63 82  Basis swaps Derivative assets 6 2  Purchased call options Derivative assets – 2  Fixed price swaps - natural gas Other long-term assets 20 18  Two-way costless collars Other long-term assets 12 –  Three-way costless collars Other long-term assets 28 39  Purchased call options Other long-term assets 18 –  Interest rate swaps Other long-term assets 1 –  Total derivative assets $ 189 $ 186 (1)   Derivative Liabilities  Balance Sheet Classification Fair Value  March 31, 2018 December 31, 2017  Derivatives not designated as hedging instruments: (in millions)  Fixed price swaps - natural gas Derivative liabilities $ 2 $ –  Two-way costless collars Derivative liabilities 3 1  Three-way costless collars Derivative liabilities 25 36  Basis swaps Derivative liabilities 7 23  Sold call options Derivative liabilities 3 3  Interest rate swaps Derivative liabilities – 1  Fixed price swaps - natural gas Other long-term liabilities – 1  Two-way costless collars Other long-term liabilities 6 –  Three-way costless collars Other long-term liabilities 16 30  Sold call options Other long-term liabilities 49 15  Total derivative liabilities $ 111 $ 110 (1) Excludes $1 million in premiums paid related to certain call options recognized as a component of derivative assets within current assets on the condensed consolidated balance sheet at December 31, 2017. As certain call options settled, the premium was amortized and recognized as a component of gain (loss) on derivatives on the unaudited condensed statement of operations.
Summary of Before Tax Effect of Fair Value Hedges not Designated for Hedge Accounting	  Gain (Loss) on Derivatives, Unsettled Recognized in Earnings  Consolidated Statement of Operations For the three months ended  Classification of Gain (Loss) March 31,  Derivative Instrument on Derivatives, Unsettled 2018 2017  (in millions)  Fixed price swaps - natural gas Gain (Loss) on Derivatives $ (3) $ 118  Fixed price swaps - propane Gain (Loss) on Derivatives 3 –  Two-way costless collars Gain (Loss) on Derivatives 3 31  Three-way costless collars Gain (Loss) on Derivatives (5) 57  Basis swaps Gain (Loss) on Derivatives 20 (103)  Purchased call options Gain (Loss) on Derivatives 16 –  Sold call options Gain (Loss) on Derivatives (34) 42  Interest rate swaps Gain (Loss) on Derivatives 2 1  Total gain on unsettled derivatives $ 2 $ 146   Gain (Loss) on Derivatives, Settled (1)  Recognized in Earnings  Consolidated Statement of Operations For the three months ended  Classification of Gain (Loss) March 31,  Derivative Instrument on Derivatives, Settled 2018 2017  (in millions)  Fixed price swaps - natural gas Gain (Loss) on Derivatives $ – $ (16)  Two-way costless collars Gain (Loss) on Derivatives 4 (3)  Three-way costless collars Gain (Loss) on Derivatives 7 (4)  Basis swaps Gain (Loss) on Derivatives (21) (1)  Purchased call options Gain (Loss) on Derivatives 2 (2) –  Sold call options Gain (Loss) on Derivatives (1) (6)  Total loss on settled derivatives $ (9) $ (30)   Total gain (loss) on derivatives $ (7) $ 116  (1) The Company calculates gain (loss) on derivatives, settled, as the summation of gains and losses on positions that settled within the period.  (2) Includes $1 million amortization of premiums paid related to certain call options for the three months ended March 31, 201 8 , which is included in gain (loss) on derivatives on the unaudited condensed consolidated statement s of operation s .

Reclassifications from Accumu29

Reclassifications from Accumulated Other Comprehensive Income (Loss) (Tables)	3 Months Ended
	Mar. 31, 2018
Reclassifications from Accumulated Other Comprehensive Income (Loss) [Abstract]
Components of Accumulated Other Comprehensive Income (Loss)	  (in millions) Pension and Other Postretirement Foreign Currency Total  Beginning balance, December 31, 2017 $ (30) $ (14) $ (44)  Other comprehensive income (loss) before reclassifications (1) – – –  Amounts reclassified from other comprehensive income (loss) (1) (2) – – –  Net current-period other comprehensive income (loss) – – –  Ending balance, March 31, 2018 $ (30) $ (14) $ (44) (1) Deferred tax activity related to pension and other postretirement benefits was offset by a valuation allowance, resulting in no tax expense recorded for the period. (2) See separate table below for details about these reclassifications.
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	  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 March 31, 2018  Pension and other postretirement: (in millions)  Amortization of prior service cost and net loss (1) Other Income (Loss), Net $ –  Provision (benefit) for income taxes –  Net income $ –   Total reclassifications for the period Net income $ –  (1) See Note 11 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, 2018
Fair Value Measurements [Abstract]
Carrying Amount and Estimated Fair Values of Financial Instruments	  March 31, 2018 December 31, 2017  Carrying Fair Carrying Fair  (in millions) Amount Value Amount Value  Cash and cash equivalents $ 958 $ 958 $ 916 $ 916  2018 term loan facility due December 2020 (1)(2) 1,191 1,191 1,191 1,191  Senior notes (2) 3,242 3,199 3,242 3,358  Derivative instruments, net 78 78 76 (3) 76 (3)  (1) Concurrent with the closing of the new 2018 credit facility agreement, the Company repaid the $1,191 million secured term loan balance on April 26, 2018. See Note 16 – Subsequent Events for more information on the 2018 credit facility.  (2) Excludes unamortized debt issuance costs and debt discounts.  (3) Excludes $1 million in premiums paid related to certain call options recognized as a component of derivatives assets within current assets on the condensed consolidated balance sheet.
Summary of Assets and Liabilities Measured at Fair Value on Recurring Basis	  March 31, 2018  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  Fixed price swap - natural gas assets $ – $ 54 $ – $ 54  Fixed price swap - propane assets – 3 – 3  Two-way costless collar assets – – 16 16  Three-way costless collar assets – – 91 91  Basis swap assets – – 6 6  Purchased call option assets – – 18 18  Interest rate swap assets – 1 – 1  Fixed price swap - natural gas liabilities – (2) – (2)  Two-way costless collar liabilities – – (9) (9)  Three-way costless collar liabilities – – (41) (41)  Basis swap liabilities – – (7) (7)  Sold call option liabilities – – (52) (52)  Total $ – $ 56 $ 22 $ 78     December 31, 2017  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  Fixed price swap assets $ – $ 56 $ – $ 56  Two-way costless collar assets – – 5 5  Three-way costless collar assets – – 121 121  Purchased call option assets – – 2 2  Basis swap assets – – 2 2  Fixed price swap liabilities – (1) – (1)  Two-way costless collar liabilities – – (1) (1)  Three-way costless collar liabilities – – (66) (66)  Basis swap liabilities – – (23) (23)  Sold call option liabilities – – (18) (18)  Interest rate swap liabilities – (1) – (1)  Total $ – $ 54 $ 22 $ 76 
Reconciliations for Change in Net Fair Value of Derivative Assets and Liabilities Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs (Level 3)	  For the three months ended  March 31,  (in millions) 2018 2017  Balance at beginning of period $ 22 $ (195)  Total gains (losses):  Included in earnings (9) 13  Settlements (1) 9 14  Transfers into/out of Level 3 – –  Balance at end of period $ 22 $ (168)  Change in gains included in earnings relating to derivatives still held as of March 31 $ – $ 27  (1) Includes $1 million amortization of premiums paid related to certain call options for the three months ended March 31, 2018.

Debt (Tables)

Debt (Tables)	3 Months Ended
	Mar. 31, 2018
Debt [Abstract]
Components of Debt	  March 31, 2018  (in millions) Debt Instrument Unamortized Issuance Expense Unamortized Debt Discount Total  Variable rate ( 4.240% at March 31, 2018) 2016 term loan facility, due December 2020 (1) $ 1,191 $ (8) $ − $ 1,183  4.05% Senior Notes due January 2020 (2) 92 − − 92  4.10% Senior Notes due March 2022 1,000 (6) − 994  4.95% Senior Notes due January 2025 (2) 1,000 (8) (2) 990  7.50 % Senior Notes due April 2026 650 (9) − 641  7.75 % Senior Notes due October 2027 500 (7) − 493  Total debt $ 4,433 $ (38) $ (2) $ 4,393      December 31, 2017  (in millions) Debt Instrument Unamortized Issuance Expense Unamortized Debt Discount Total  Variable rate ( 3.980% at December 31, 2017) 2016 term loan facility, due December 2020 (1) $ 1,191 $ (8) $ − $ 1,183  4.05% Senior Notes due January 2020 (2) 92 − – 92  4.10% Senior Notes due March 2022 1,000 (7) – 993  4.95% Senior Notes due January 2025 (2) 1,000 (8) (2) 990  7.50% Senior Notes due April 2026 650 (10) − 640  7.75% Senior Notes due October 2027 500 (7) – 493  Total debt $ 4,433 $ (40) $ (2) $ 4,391  (1) Concurrent with the closing of the new 2018 credit facility agreement on April 26, 2018, the Company repaid the $1,191 million secured term loan balance with cash on hand and borrowings under the new credit facility. The Company’s initial borrowings under the 2018 credit facility were $360 m illion, a portion of which related to other working capital needs. See Note 16 – Subsequent Events for more information on the 2018 credit facility.  (2) In February and June 2016, Moody’s and S&P downgraded certain senior notes, increasing the interest rates by 175 basis points effective July 2016. As a result of the downgrades, interest rates increased to 5.80% for the 2020 Notes and 6.70% for the 2025 Notes.

Commitments and Contingencies (

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2018
Commitments and Contingencies [Abstract]
Schedule of Future Obligation under Transportation Agreements	  Payments Due by Period  Less than 1 More than 8  (in millions) Total Year 1 to 3 Years 3 to 5 Years 5 to 8 Years Years  Infrastructure Currently in Service $ 5,986 $ 639 $ 1,208 $ 894 $ 1,151 $ 2,094  Pending Regulatory Approval and/or Construction (1) 3,139 46 317 389 626 1,761  Total Transportation Charges $ 9,125 $ 685 $ 1,525 $ 1,283 $ 1,777 $ 3,855 (1) Based on estimated in-service dates as of March 31, 2018.

Pension Plan and Other Postre33

Pension Plan and Other Postretirement Benefits (Tables)	3 Months Ended
	Mar. 31, 2018
Pension Plan and Other Postretirement Benefits [Abstract]
Pension and Other Postretirement Benefit Costs	  Pension Benefits  Condensed Consolidated Statement s of For the three months ended  Operations Classification of March 31,  (in millions) Net Periodic Benefit Cost (1) 2018 2017  Service cost General and administrative expenses $ 3 $ 2  Interest cost Other Income (Loss), Net 2 1  Expected return on plan assets Other Income (Loss), Net (2) (1)  Amortization of prior service cost Other Income (Loss), Net − −  Amortization of net loss Other Income (Loss), Net – 1  Net periodic benefit cost $ 3 $ 3  (1) In the first quarter of 2018, the Company adopted Accounting Standards Update No. 2017-07, which requires the service cost component to be disaggregated from the other components of net benefit cost, which are to be presented outside of income from operations. See Note 15 – New Accounting Pronouncements for more information regarding this update.

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2018
Stock-Based Compensation [Abstract]
Schedule of Stock-Based Compensation Costs	   For the three months ended March 31, (in millions) 2018 2017  Stock-based compensation cost – expensed $ 5 $ 6  Stock-based compensation cost – capitalized $ 3 $ 4 
Schedule of Equity-Classified Stock-Based Compensation Costs	  For the three months ended March 31,  (in millions) 2018 2017  Equity-classified stock-based compensation cost – expensed $ 4 $ 6  Equity-classified stock-based compensation cost – capitalized $ 3 $ 4 
Summary of Equity-Classified Stock Option Activity	  Number Weighted Average  of Options Exercise Price  (in thousands)  Outstanding at December 31, 2017 6,020 $ 19.43  Granted − −  Exercised – –  Forfeited or expired (3) 38.65  Outstanding at March 31, 2018 6,017 $ 19.42  Exercisable at March 31, 2018 4,379 $ 23.80 
Summary of Equity-Classified Restricted Stock Activity	   Number Weighted Average  of Shares Fair Value  (in thousands)  Unvested shares at December 31, 2017 6,254 $ 8.85  Granted 5 5.91  Vested (1,033) 8.77  Forfeited (160) 9.07  Unvested shares at March 31, 2018 5,066 $ 8.85 
Summary of Equity-Classified Performance Units Activity	   Number Weighted Average  of Units (1) Fair Value  (in thousands)  Unvested units at December 31, 2017 1,084 $ 10.12  Granted − −  Vested − −  Forfeited (18) 9.99  Unvested units at March 31, 2018 1,066 $ 10.12 (1) These amounts reflect the number of performance units granted in thousands. The actual payout of shares may range from a minimum of zero shares to a maximum of two s hares per unit contingent upon TSR . The performance units have a three -year vesting term and the actual disbursement of shares, if any, is determined during the first quarter following the end of the three-year vesting period.
Schedule of Liability-Classified Stock-Based Compensation Costs	  For the three months ended March 31, (in millions) 2018  Liability-classified s tock-based compensation cost – expensed $ 1  Liability-classified s tock-based compensation cost – capitalized (1) $ –  (1) For the three months ended March 31, 2018, the liability-classified stock-based compensation amount capitalized was less than $1 million.

Segment Information (Tables)

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2018
Segment Information [Abstract]
Summary of Financial Information for Company's Reportable Segments	    E&P Midstream Other Total  Three months ended March 31, 2018: (in millions)  Revenues from external customers $ 643 $ 277 $ – $ 920  Intersegment revenues (6) 619 – 613  Depreciation, depletion and amortization expense 117 26 ( 1 ) – 143  Operating income 238 17 – 255  Interest expense (2) 39 – – 39  Loss on derivatives (7) – – (7)  Other income (loss), net – (1) – (1)  Assets 5,346 1,217 1,150 (3) 7,713  Capital investments (4) 334 4 – 338   Three months ended March 31, 2017:  Revenues from external customers $ 566 $ 280 $ – $ 846  Intersegment revenues (3) 578 – 575  Depreciation, depletion and amortization expense 90 16 – 106  Operating income 225 41 – 266  Interest expense (2) 32 – – 32  Gain on derivatives 116 – – 116  Other income, net 2 – (1) 1  Assets 4,413 1,268 1,515 (3) 7,196  Capital investments (4) 283 6 1 290  (1) Includes a $10 million impairment related to certain non-core gathering asset s.  (2) Interest expense by segment is an allocation of corporate amounts as they are incurred at the corporate level.  (3) Other assets represent corporate assets not allocated to segments and assets for non-reportable segments. At March 31, 2018 and 2017, other assets includes approximately $958 million and $1.4 billion in cash and cash equivalents, respectively.  (4) Capital investments includes an increase of $33 million and a decrease of $52 m illion for the three months ended March 31, 2018 and 2017, respectively, relating to the change in ca pital accruals between periods.

Basis of Presentation (Narrativ

Basis of Presentation (Narrative) (Details)	3 Months Ended
	Mar. 31, 2018segment
Basis of Presentation [Abstract]
Number of segments	2

Revenue Recognition (Narrative)

Revenue Recognition (Narrative) (Details)	Mar. 31, 2018USD ($)
Revenue Recognition [Abstract]
Contract asset associated with revenues from contracts with customers	$ 0
Contract liability associated with revenues from contracts with customers	$ 0

Revenue Recognition (Disaggrega

Revenue Recognition (Disaggregation of Revenue by Segment) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Disaggregation of Revenue [Line Items]
Gas sales	$ 540	$ 503
Oil sales	35	23
NGL sales	65	40
Marketing	253	253
Gas gathering	24	27
Other	3
Total Operating Revenues	920	846
E&P [Member]
Disaggregation of Revenue [Line Items]
Gas sales	535	500
Oil sales	34	23
NGL sales	65	40
Other	3
Total	637	563
Total Operating Revenues	643	566
Midstream [Member]
Disaggregation of Revenue [Line Items]
Marketing	829	777
Gas gathering	67	81
Total	896	858
Total Operating Revenues	277	280
Intersegment Eliminations [Member]
Disaggregation of Revenue [Line Items]
Gas sales	5	3
Oil sales	1
Marketing	(576)	(524)
Gas gathering	(43)	(54)
Total Operating Revenues	(613)	(575)
Intersegment Eliminations [Member] | E&P [Member]
Disaggregation of Revenue [Line Items]
Total Operating Revenues	6	3
Intersegment Eliminations [Member] | Midstream [Member]
Disaggregation of Revenue [Line Items]
Marketing	576	524
Total Operating Revenues	$ (619)	$ (578)

Revenue Recognition (Disaggre39

Revenue Recognition (Disaggregation of Revenue on Geographic Basis) (Details) - E&P [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Disaggregation of Revenue [Line Items]
Revenues	$ 637	$ 563
Northeast Appalachia [Member]
Disaggregation of Revenue [Line Items]
Revenues	327	253
Southwest Appalachia [Member]
Disaggregation of Revenue [Line Items]
Revenues	156	104
Fayetteville Shale [Member]
Disaggregation of Revenue [Line Items]
Revenues	152	205
Other Property [Member]
Disaggregation of Revenue [Line Items]
Revenues	$ 2	$ 1

Revenue Recognition (Reconcilia

Revenue Recognition (Reconciliation of Accounts Receivable) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Revenue Recognition [Abstract]
Receivables from contracts with customers	$ 273	$ 322
Other accounts receivable	109	106
Total accounts receivable	$ 382	$ 428

Cash and Cash Equivalents (Summ

Cash and Cash Equivalents (Summary of Cash and Cash Equivalents) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Cash and Cash Equivalents [Abstract]
Cash	$ 267	$ 261
Marketable securities	691	605
Other cash equivalents		50
Total	$ 958	$ 916	$ 1,382	$ 1,423

Natural Gas and Oil Properties

Natural Gas and Oil Properties (Narrative) (Details)	3 Months Ended
	Mar. 31, 2018item$ / bbl$ / MMBTU	Mar. 31, 2017item$ / 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 | item	0	0
Natural Gas [Member] | Henry Hub [Member]
Natural Gas and Oil Properties [Line Items]
Full cost ceiling test, price | $ / MMBTU	3	2.73
Oil [Member] | West Texas Intermediate [Member]
Natural Gas and Oil Properties [Line Items]
Full cost ceiling test, price	49.94	44.10
NGL [Member] | West Texas Intermediate [Member]
Natural Gas and Oil Properties [Line Items]
Full cost ceiling test, price	14.90	10.17

Earnings Per Share (Narrative)

Earnings Per Share (Narrative) (Details) - shares	1 Months Ended	3 Months Ended	9 Months Ended
	Jan. 31, 2015	Mar. 31, 2018	Sep. 30, 2017	Jan. 12, 2018
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Preferred stock, date dividend declared		Dec. 18, 2017
Preferred stock, date dividend to be paid		Jan. 16, 2018
Preferred stock, common shares issued as stock dividend			10,040,306
Common Stock [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Shares issued upon conversion				74,998,614
Depositary Shares [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Shares issued	34,500,000

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, 2018		Mar. 31, 2017
Earnings Per Share [Abstract]
Net income	$ 208	[1]	$ 351
Mandatory convertible preferred stock dividend			27
Participating securities - mandatory convertible preferred stock	3		43
Net Income Attributable to Common Stock	$ 205		$ 281
Number of common shares: Weighted average outstanding	571,297,804		493,068,000
Number of common shares: Issued upon assumed exercise of outstanding stock options			82,845
Number of common shares: Effect of issuance of non-vested restricted common stock	914,096		770,429
Number of common shares: Effect of issuance of non-vested performance units	1,632,559		573,721
Number of common shares: Weighted average and potential dilutive outstanding	573,844,459		494,494,995
Earnings per common share: Basic	$ 0.36		$ 0.57
Earnings per common share: Diluted	$ 0.36		$ 0.57
[1]	In 2018, deferred tax activity incurred in other comprehensive income was offset by a valuation allowance.

Earnings Per Share (Schedule 45

Earnings Per Share (Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share) (Details) - shares	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, shares	15,867,213	78,066,295
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, shares		1,854,004
Unvested Share-Based Payment [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, shares	5,292,454	1,212,396
Performance Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, shares	574,944
Mandatory Convertible Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, shares	9,999,815	74,999,895

Derivatives and Risk Manageme46

Derivatives and Risk Management (Narrative) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)item
Derivative [Line Items]
Number of derivative positions designated for hedge accounting | item	0
Interest Rate Swaps [Member]
Derivative [Line Items]
Derivative assets	$ 1
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative assets	77
Not Designated as Hedging Instrument [Member] | Interest Rate Swaps [Member]
Derivative [Line Items]
Notional amount	$ 170
Derivative, expiration	Jun. 30, 2020
Derivative assets	$ 1

Derivatives and Risk Manageme47

Derivatives and Risk Management (Schedule of Derivative Instruments, Notional Amount in BCF, Weighted Average Contract Prices and Fair Value) (Details) - Not Designated as Hedging Instrument [Member] $ in Millions, ft³ in Billions	3 Months Ended
	Mar. 31, 2018USD ($)$ / bbl$ / MMBTUMBblsft³
Fixed Price Swaps - 2018 [Member] | Natural Gas [Member]
Derivative [Line Items]
Volume	215
Average price | $ / MMBTU	2.97
Fair Value | $	$ 33
Fixed Price Swaps - 2018 [Member] | Propane [Member]
Derivative [Line Items]
Volume | MBbls	1,100
Average price | $ / bbl	34.64
Fair Value | $	$ 3
Fixed Price Swaps - 2018 [Member] | Ethane [Member]
Derivative [Line Items]
Volume | MBbls	413
Average price | $ / bbl	11.19
Two-Way Costless Collars - 2018 [Member] | Natural Gas [Member]
Derivative [Line Items]
Volume	6
Fair Value | $	$ 1
Two-Way Costless Collars - 2018 Purchased Puts [Member] | Natural Gas [Member]
Derivative [Line Items]
Floor price per MMBtu | $ / MMBTU	2.90
Two-Way Costless Collars - 2018 Sold Calls [Member] | Natural Gas [Member]
Derivative [Line Items]
Cap price per MMBtu | $ / MMBTU	3.27
Three-Way Costless Collars - 2018 [Member] | Natural Gas [Member]
Derivative [Line Items]
Volume	213
Fair Value | $	$ 39
Three-Way Costless Collars - 2018 Sold Puts [Member] | Natural Gas [Member]
Derivative [Line Items]
Floor price per MMBtu | $ / MMBTU	2.40
Three-Way Costless Collars - 2018 Purchased Puts [Member] | Natural Gas [Member]
Derivative [Line Items]
Floor price per MMBtu | $ / MMBTU	2.97
Three-Way Costless Collars - 2018 Sold Calls [Member] | Natural Gas [Member]
Derivative [Line Items]
Cap price per MMBtu | $ / MMBTU	3.37
Financial protection on production - 2018 [Member] | Natural Gas [Member]
Derivative [Line Items]
Volume	434
Fair Value | $	$ 73
Fixed Price Swaps - 2019 [Member] | Natural Gas [Member]
Derivative [Line Items]
Volume	93
Average price | $ / MMBTU	3
Fair Value | $	$ 19
Fixed Price Swaps - 2019 [Member] | Ethane [Member]
Derivative [Line Items]
Volume | MBbls	91
Average price | $ / bbl	11.61
Two-Way Costless Collars - 2019 [Member] | Natural Gas [Member]
Derivative [Line Items]
Volume	53
Fair Value | $	$ 6
Two-Way Costless Collars - 2019 Purchased Puts [Member] | Natural Gas [Member]
Derivative [Line Items]
Floor price per MMBtu | $ / MMBTU	2.80
Two-Way Costless Collars - 2019 Sold Calls [Member] | Natural Gas [Member]
Derivative [Line Items]
Cap price per MMBtu | $ / MMBTU	2.98
Three-Way Costless Collars - 2019 [Member] | Natural Gas [Member]
Derivative [Line Items]
Volume	133
Fair Value | $	$ 11
Three-Way Costless Collars - 2019 Sold Puts [Member] | Natural Gas [Member]
Derivative [Line Items]
Floor price per MMBtu | $ / MMBTU	2.49
Three-Way Costless Collars - 2019 Purchased Puts [Member] | Natural Gas [Member]
Derivative [Line Items]
Floor price per MMBtu | $ / MMBTU	2.93
Three-Way Costless Collars - 2019 Sold Calls [Member] | Natural Gas [Member]
Derivative [Line Items]
Cap price per MMBtu | $ / MMBTU	3.34
Financial protection on production - 2019 [Member] | Natural Gas [Member]
Derivative [Line Items]
Volume	279
Fair Value | $	$ 36
Basis Swaps - 2018 [Member] | Natural Gas [Member]
Derivative [Line Items]
Volume	73
Basis differential per MMBtu | $ / MMBTU	(0.59)
Basis Swaps - 2019 [Member] | Natural Gas [Member]
Derivative [Line Items]
Volume	6
Basis differential per MMBtu | $ / MMBTU	1.01
Fair Value | $	$ (1)
Basis Swaps [Member] | Natural Gas [Member]
Derivative [Line Items]
Volume	79
Fair Value | $	$ (1)
Purchased Call Options - 2020 [Member] | Natural Gas [Member]
Derivative [Line Items]
Volume	68
Cap price per MMBtu | $ / MMBTU	3.63
Fair Value | $	$ 7
Purchased Call Options - 2021 [Member] | Natural Gas [Member]
Derivative [Line Items]
Volume	57
Cap price per MMBtu | $ / MMBTU	3.52
Fair Value | $	$ 11
Purchased Call Options [Member] | Natural Gas [Member]
Derivative [Line Items]
Volume	125
Fair Value | $	$ 18
Sold Call Options - 2018 [Member] | Natural Gas [Member]
Derivative [Line Items]
Volume	47
Cap price per MMBtu | $ / MMBTU	3.50
Fair Value | $	$ (1)
Sold Call Options - 2019 [Member] | Natural Gas [Member]
Derivative [Line Items]
Volume	52
Cap price per MMBtu | $ / MMBTU	3.50
Fair Value | $	$ (4)
Sold Call Options - 2020 [Member] | Natural Gas [Member]
Derivative [Line Items]
Volume	137
Cap price per MMBtu | $ / MMBTU	3.39
Fair Value | $	$ (21)
Sold Call Options - 2021 [Member] | Natural Gas [Member]
Derivative [Line Items]
Volume	114
Cap price per MMBtu | $ / MMBTU	3.33
Fair Value | $	$ (27)
Sold Call Options [Member] | Natural Gas [Member]
Derivative [Line Items]
Volume	350
Fair Value | $	$ (53)
Storage Fixed Price Swaps - 2018 [Member]
Derivative [Line Items]
Volume	1
Average price | $ / MMBTU	2.76
Storage Basis Swaps - 2018 [Member]
Derivative [Line Items]
Volume	1
Basis differential per MMBtu | $ / MMBTU	(0.88)
Financial protection on storage - 2018 [Member]
Derivative [Line Items]
Volume	2
Storage Fixed Price Swaps -2019 [Member]
Derivative [Line Items]
Volume	1
Average price | $ / MMBTU	3.03
Storage Basis Swaps - 2019 [Member]
Derivative [Line Items]
Volume	1
Basis differential per MMBtu | $ / MMBTU	(0.44)
Financial protection on storage - 2019 [Member]
Derivative [Line Items]
Volume	2

Derivatives and Risk Manageme48

Derivatives and Risk Management (Balance Sheet Classification of Derivative Financial Instruments) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Mar. 31, 2018
Purchased Call Options - 2017 [Member]
Derivatives, Fair Value [Line Items]
Premium paid	$ 1
Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	186	$ 189
Derivative liabilities	110	111
Not Designated as Hedging Instrument [Member] | Two-Way Costless Collars [Member] | Derivative Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	5	4
Not Designated as Hedging Instrument [Member] | Two-Way Costless Collars [Member] | Other Long-Term Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative assets		12
Not Designated as Hedging Instrument [Member] | Two-Way Costless Collars [Member] | Derivative Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liabilities	1	3
Not Designated as Hedging Instrument [Member] | Two-Way Costless Collars [Member] | Other Long-Term Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liabilities		6
Not Designated as Hedging Instrument [Member] | Three-Way Costless Collars [Member] | Derivative Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	82	63
Not Designated as Hedging Instrument [Member] | Three-Way Costless Collars [Member] | Other Long-Term Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	39	28
Not Designated as Hedging Instrument [Member] | Three-Way Costless Collars [Member] | Derivative Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liabilities	36	25
Not Designated as Hedging Instrument [Member] | Three-Way Costless Collars [Member] | Other Long-Term Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liabilities	30	16
Not Designated as Hedging Instrument [Member] | Basis Swaps [Member] | Derivative Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	2	6
Not Designated as Hedging Instrument [Member] | Basis Swaps [Member] | Derivative Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liabilities	23	7
Not Designated as Hedging Instrument [Member] | Purchased Call Options [Member] | Derivative Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	2
Not Designated as Hedging Instrument [Member] | Purchased Call Options [Member] | Other Long-Term Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative assets		18
Not Designated as Hedging Instrument [Member] | Sold Call Options [Member] | Derivative Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liabilities	3	3
Not Designated as Hedging Instrument [Member] | Sold Call Options [Member] | Other Long-Term Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liabilities	15	49
Not Designated as Hedging Instrument [Member] | Interest Rate Swaps [Member] | Other Long-Term Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative assets		1
Not Designated as Hedging Instrument [Member] | Interest Rate Swaps [Member] | Derivative Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liabilities	1
Not Designated as Hedging Instrument [Member] | Purchased Call Options - 2017 [Member]
Derivatives, Fair Value [Line Items]
Premium paid	1
Natural Gas [Member] | Not Designated as Hedging Instrument [Member] | Fixed Price Swaps [Member] | Derivative Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	38	34
Natural Gas [Member] | Not Designated as Hedging Instrument [Member] | Fixed Price Swaps [Member] | Other Long-Term Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	18	20
Natural Gas [Member] | Not Designated as Hedging Instrument [Member] | Fixed Price Swaps [Member] | Derivative Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liabilities		2
Natural Gas [Member] | Not Designated as Hedging Instrument [Member] | Fixed Price Swaps [Member] | Other Long-Term Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative liabilities	$ 1
Propane [Member] | Not Designated as Hedging Instrument [Member] | Fixed Price Swaps [Member] | Derivative Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative assets		$ 3

Derivatives and Risk Manageme49

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, 2018	Mar. 31, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instrument, Gain (Loss) on Derivatives, Unsettled	$ 2	$ 146
Derivative Instrument, Gain (Loss) on Derivatives, Settled	(9)	(30)
Total gain (loss) on derivatives	(7)	116
Two-Way Costless Collars [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instrument, Gain (Loss) on Derivatives, Unsettled	3	31
Derivative Instrument, Gain (Loss) on Derivatives, Settled	4	(3)
Three-Way Costless Collars [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instrument, Gain (Loss) on Derivatives, Unsettled	(5)	57
Derivative Instrument, Gain (Loss) on Derivatives, Settled	7	(4)
Basis Swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instrument, Gain (Loss) on Derivatives, Unsettled	20	(103)
Derivative Instrument, Gain (Loss) on Derivatives, Settled	(21)	(1)
Purchased Call Options [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instrument, Gain (Loss) on Derivatives, Unsettled	16
Derivative Instrument, Gain (Loss) on Derivatives, Settled	2
Sold Call Options [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instrument, Gain (Loss) on Derivatives, Unsettled	(34)	42
Derivative Instrument, Gain (Loss) on Derivatives, Settled	(1)	(6)
Amortization of premium paid	1
Interest Rate Swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instrument, Gain (Loss) on Derivatives, Unsettled	2	1
Purchased Call Options - 2018 [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amortization of premium paid	1
Natural Gas [Member] | Fixed Price Swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instrument, Gain (Loss) on Derivatives, Unsettled	(3)	118
Derivative Instrument, Gain (Loss) on Derivatives, Settled		(16)
Propane [Member] | Fixed Price Swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instrument, Gain (Loss) on Derivatives, Unsettled	$ 3

Reclassifications from Accumu50

Reclassifications from Accumulated Other Comprehensive Income (Loss) (Components of Accumulated Other Comprehensive Income (Loss)) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, December 31, 2017	$ (44)
Other comprehensive income (loss) before reclassifications
Amounts reclassified from other comprehensive income (loss)
Net current-period other comprehensive income (loss)
Ending balance, March 31, 2018	(44)
Pension And Other Postretirement [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, December 31, 2017	(30)
Other comprehensive income (loss) before reclassifications
Amounts reclassified from other comprehensive income (loss)
Net current-period other comprehensive income (loss)
Ending balance, March 31, 2018	(30)
Foreign Currency [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance, December 31, 2017	(14)
Other comprehensive income (loss) before reclassifications
Amounts reclassified from other comprehensive income (loss)
Net current-period other comprehensive income (loss)
Ending balance, March 31, 2018	$ (14)

Reclassifications from Accumu51

Reclassifications from Accumulated Other Comprehensive Income (Loss) (Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018		Mar. 31, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other income (loss), net	$ (1)		$ 1
Provision (benefit) for income taxes
Net Income	208	[1]	$ 351
Reclassified from Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net Income
Pension And Other Postretirement [Member] | Reclassified from Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other income (loss), net
Provision (benefit) for income taxes
Net Income
[1]	In 2018, deferred tax activity incurred in other comprehensive income was offset by a valuation allowance.

Fair Value Measurements (Carryi

Fair Value Measurements (Carrying Amount and Estimated Fair Values of Financial Instruments) (Details) - USD ($) $ in Millions	Apr. 26, 2018	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative instruments, net		$ 78	$ 76
Carrying Amount [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents		958	916
Derivative instruments, net		78	76
Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents		958	916
Derivative instruments, net		$ 78	$ 76
Long-term Debt [Member] | 2016 Term Loan due December 2020 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Maturity date, year and month		2020-12	2020-12
Long-term Debt [Member] | 2018 Term Loan due December 2020 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Maturity date, year and month		2020-12
Long-term Debt [Member] | Carrying Amount [Member] | 2018 Term Loan due December 2020 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans		$ 1,191	$ 1,191
Long-term Debt [Member] | Fair Value [Member] | 2018 Term Loan due December 2020 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans		1,191	1,191
Senior Notes [Member] | Carrying Amount [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior notes		3,242	3,242
Senior Notes [Member] | Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior notes		$ 3,199	3,358
Purchased Call Options - 2017 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Premium paid			1
Purchased Call Options - 2017 [Member] | Not Designated as Hedging Instrument [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Premium paid			$ 1
Subsequent Event [Member] | Long-term Debt [Member] | 2016 Term Loan due December 2020 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Repayments of long-term debt	$ 1,191

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, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	$ 78	$ 76
Significant Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	56	54
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	22	22
Fixed Price Swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		56
Derivative liabilities		(1)
Fixed Price Swaps [Member] | Significant Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		56
Derivative liabilities		(1)
Two-Way Costless Collars [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	16	5
Derivative liabilities	(9)	(1)
Two-Way Costless Collars [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	16	5
Derivative liabilities	(9)	(1)
Three-Way Costless Collars [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	91	121
Derivative liabilities	(41)	(66)
Three-Way Costless Collars [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	91	121
Derivative liabilities	(41)	(66)
Basis Swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	6	2
Derivative liabilities	(7)	(23)
Basis Swaps [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	6	2
Derivative liabilities	(7)	(23)
Purchased Call Options [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	18	2
Purchased Call Options [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	18	2
Sold Call Options [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	(52)	(18)
Sold Call Options [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities	(52)	(18)
Interest Rate Swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	1
Derivative liabilities		(1)
Interest Rate Swaps [Member] | Significant Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	1
Derivative liabilities		$ (1)
Not Designated as Hedging Instrument [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	77
Not Designated as Hedging Instrument [Member] | Interest Rate Swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	1
Natural Gas [Member] | Fixed Price Swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	54
Derivative liabilities	(2)
Natural Gas [Member] | Fixed Price Swaps [Member] | Significant Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	54
Derivative liabilities	(2)
Propane [Member] | Fixed Price Swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	3
Propane [Member] | Fixed Price Swaps [Member] | Significant Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	$ 3

Fair Value Measurements (Reconc

Fair Value Measurements (Reconciliations for Change in Net Fair Value of Derivative Assets and Liabilities Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs (Level 3)) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	$ 22	$ (195)
Included in earnings	(9)	13
Settlements	9	14
Transfers into/out of Level 3
Balance at end of period	22	(168)
Change in gains included in earnings relating to derivatives still held as of March 31		$ 27
Sold Call Options [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Amortization of premium paid	$ 1

Debt (Senior Notes - Narrative)

Debt (Senior Notes - Narrative) (Details) - USD ($) $ in Millions	1 Months Ended				3 Months Ended		6 Months Ended	12 Months Ended
	Oct. 31, 2017	Sep. 30, 2017	Jul. 31, 2016	Jan. 31, 2015	Mar. 31, 2018	Mar. 31, 2017	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Loss on extinguishment of debt		$ 59				$ 1	$ 11
Payment of premiums		53
Senior Notes [Member]
Debt Instrument [Line Items]
Proceeds from issuance of debt		1,100		$ 2,200
Increase in basis spread			1.75%
Senior Notes [Member] | Over LIBOR [Member]
Debt Instrument [Line Items]
Incremental increase in basis points resulting from downgrades				0.25%
Incremental decrease in basis points resulting from upgrades				0.25%
Increase in basis spread			1.75%
3.30% Senior Notes due January 2018 [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
Senior notes				$ 350
Stated interest rate				3.30%
Maturity date, year and month				2018-01
Repayments of long-term debt							$ 38
4.05% Senior Notes due January 2020 [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
Senior notes				$ 850
Stated interest rate			5.80%	4.05%	4.05%			4.05%
Maturity date, year and month				2020-01	2020-01			2020-01
Repayments of long-term debt		758
4.95% Senior Notes due January 2025 [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
Senior notes				$ 1,000
Stated interest rate			6.70%	4.95%	4.95%			4.95%
Maturity date, year and month				2025-01	2025-01			2025-01
7.50% Senior Notes due February 2018 [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
Stated interest rate							7.50%
Maturity date, year and month							2018-02
Repayments of long-term debt							$ 212
7.15% Senior Notes due June 2018 [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
Stated interest rate							7.15%
Maturity date, year and month							2018-06
Repayments of long-term debt							$ 26
7.50% Senior Notes due April 2026 [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
Senior notes		$ 650
Stated interest rate		7.50%			7.50%			7.50%
Maturity date, year and month		2026-04			2026-04			2026-04
2015 Term Loan due December 2020 [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
Repayments of long-term debt		$ 327
7.75% Senior Notes due October 2027 [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
Senior notes		$ 500
Stated interest rate		7.75%			7.75%			7.75%
Maturity date, year and month		2027-10			2027-10			2027-10
4.10% Senior Notes due March 2022 [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
Stated interest rate					4.10%			4.10%
Maturity date, year and month					2022-03			2022-03
2017 Senior Notes [Member] | Short-term Debt [Member]
Debt Instrument [Line Items]
Repayment of short-term debt	$ 40
Maximum [Member] | 4.05% Senior Notes due January 2020 [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
Stated interest rate									6.05%
Maximum [Member] | 4.95% Senior Notes due January 2025 [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
Stated interest rate									6.95%

Debt (2016 Credit Facility - Na

Debt (2016 Credit Facility - Narrative) (Details)	Apr. 26, 2018USD ($)	Sep. 30, 2017USD ($)	Jun. 30, 2016USD ($)	Mar. 31, 2018USD ($)	Jun. 30, 2017	Dec. 31, 2018	Dec. 31, 2017USD ($)	Dec. 31, 2013USD ($)
Long-term Debt [Member]
Debt Instrument [Line Items]
Debt instrument				$ 4,433,000,000			$ 4,433,000,000
Long-term Debt [Member] | 2013 Credit Facility [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity			$ 66,000,000					$ 2,000,000,000
Line of credit, amount borrowed				0
Long-term Debt [Member] | 2016 Credit Facility [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity			$ 743,000,000	743,000,000
Line of credit, amount borrowed				0
Long-term Debt [Member] | Letter of Credit [Member]
Debt Instrument [Line Items]
Amount outstanding	$ 323,000,000			$ 323,000,000
Revolving Credit Facility And Term Loan Facility [Member]
Debt Instrument [Line Items]
Maturity date, year and month			2020-12
Revolving Credit Facility And Term Loan Facility [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity			$ 1,934,000,000
Leverage ratio		4		5
Net cash proceeds from asset sales allowed to be retained		$ 500,000,000
Revolving Credit Facility And Term Loan Facility [Member] | Long-term Debt [Member] | Scenario, Forecast [Member]
Debt Instrument [Line Items]
Leverage ratio						4.50
Revolving Credit Facility And Term Loan Facility [Member] | Long-term Debt [Member] | Minimum [Member]
Debt Instrument [Line Items]
Minimum interest coverage ratio					2
Liquidity requirement				$ 300,000,000
Revolving Credit Facility And Term Loan Facility [Member] | Long-term Debt [Member] | Eurodollar [Member] | Minimum [Member]
Debt Instrument [Line Items]
Basis points				1.75%
Revolving Credit Facility And Term Loan Facility [Member] | Long-term Debt [Member] | Eurodollar [Member] | Maximum [Member]
Debt Instrument [Line Items]
Basis points				2.50%
Revolving Credit Facility And Term Loan Facility [Member] | Long-term Debt [Member] | Base Rate [Member] | Minimum [Member]
Debt Instrument [Line Items]
Basis points				0.75%
Revolving Credit Facility And Term Loan Facility [Member] | Long-term Debt [Member] | Base Rate [Member] | Maximum [Member]
Debt Instrument [Line Items]
Basis points				1.50%
Revolving Credit Facility And Term Loan Facility [Member] | Long-term Debt [Member] | Over LIBOR [Member]
Debt Instrument [Line Items]
Basis points				2.50%
2016 Term Loan due December 2020 [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
Debt instrument			$ 1,191,000,000	$ 1,191,000,000			$ 1,191,000,000
Maturity date, year and month				2020-12			2020-12
Collateral coverage ratio				1.50
Subsequent Event [Member] | 2016 Term Loan due December 2020 [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
Repayments of long-term debt	$ 1,191,000,000

Debt (2013 Credit Facility - Na

Debt (2013 Credit Facility - Narrative) (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Jun. 30, 2016	Dec. 31, 2013
Debt Instrument [Line Items]
Adjusted debt capital structure, percentage	29.00%
Long-term Debt [Member]
Debt Instrument [Line Items]
Debt instrument	$ 4,433,000,000	$ 4,433,000,000
Long-term Debt [Member] | 2013 Credit Facility [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity			$ 66,000,000	$ 2,000,000,000
Line of credit, amount borrowed	$ 0
Credit facility, maturity date	Dec. 1, 2018
Debt percentage of adjusted book capital structure covenant	60.00%
Long-term Debt [Member] | 2016 Credit Facility [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 743,000,000		743,000,000
Line of credit, amount borrowed	0
2016 Term Loan due December 2020 [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
Debt instrument	$ 1,191,000,000	$ 1,191,000,000	$ 1,191,000,000

Debt (Components of Debt) (Deta

Debt (Components of Debt) (Details) - USD ($) $ in Millions	Apr. 26, 2018	Sep. 30, 2017	Jul. 31, 2016	Jan. 31, 2015	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jun. 30, 2016
Long-term Debt [Member]
Debt Instrument [Line Items]
Debt Instrument					$ 4,433	$ 4,433
Unamortized Issuance Expense					(38)	(40)
Unamortized Debt Discount					(2)	(2)
Total					4,393	4,391
Long-term Debt [Member] | 2016 Term Loan due December 2020 [Member]
Debt Instrument [Line Items]
Debt Instrument					1,191	1,191		$ 1,191
Unamortized Issuance Expense					(8)	(8)
Total					$ 1,183	$ 1,183
Variable interest rate					4.24%	3.98%
Maturity date, year and month					2020-12	2020-12
Long-term Debt [Member] | 4.05% Senior Notes due January 2020 [Member]
Debt Instrument [Line Items]
Debt Instrument					$ 92	$ 92
Total					$ 92	$ 92
Stated interest rate			5.80%	4.05%	4.05%	4.05%
Maturity date, year and month				2020-01	2020-01	2020-01
Repayments of long-term debt		$ 758
Long-term Debt [Member] | 4.05% Senior Notes due January 2020 [Member] | Maximum [Member]
Debt Instrument [Line Items]
Stated interest rate							6.05%
Long-term Debt [Member] | 4.10% Senior Notes due March 2022 [Member]
Debt Instrument [Line Items]
Debt Instrument					$ 1,000	$ 1,000
Unamortized Issuance Expense					(6)	(7)
Total					$ 994	$ 993
Stated interest rate					4.10%	4.10%
Maturity date, year and month					2022-03	2022-03
Long-term Debt [Member] | 4.95% Senior Notes due January 2025 [Member]
Debt Instrument [Line Items]
Debt Instrument					$ 1,000	$ 1,000
Unamortized Issuance Expense					(8)	(8)
Unamortized Debt Discount					(2)	(2)
Total					$ 990	$ 990
Stated interest rate			6.70%	4.95%	4.95%	4.95%
Maturity date, year and month				2025-01	2025-01	2025-01
Long-term Debt [Member] | 4.95% Senior Notes due January 2025 [Member] | Maximum [Member]
Debt Instrument [Line Items]
Stated interest rate							6.95%
Long-term Debt [Member] | 7.50% Senior Notes due April 2026 [Member]
Debt Instrument [Line Items]
Debt Instrument					$ 650	$ 650
Unamortized Issuance Expense					(9)	(10)
Total					$ 641	$ 640
Stated interest rate		7.50%			7.50%	7.50%
Maturity date, year and month		2026-04			2026-04	2026-04
Long-term Debt [Member] | 7.75% Senior Notes due October 2027 [Member]
Debt Instrument [Line Items]
Debt Instrument					$ 500	$ 500
Unamortized Issuance Expense					(7)	(7)
Total					$ 493	$ 493
Stated interest rate		7.75%			7.75%	7.75%
Maturity date, year and month		2027-10			2027-10	2027-10
Senior Notes [Member]
Debt Instrument [Line Items]
Increase in basis spread			1.75%
Subsequent Event [Member] | 2018 Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit, amount borrowed	$ 360
Subsequent Event [Member] | Long-term Debt [Member] | 2018 Credit Facility [Member]
Debt Instrument [Line Items]
Amount to be amended, redeemed or refinanced to avoid acceleration	700
Line of credit, amount borrowed	360
Subsequent Event [Member] | Long-term Debt [Member] | 2016 Term Loan due December 2020 [Member]
Debt Instrument [Line Items]
Repayments of long-term debt	$ 1,191
Over LIBOR [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Increase in basis spread			1.75%

Commitments and Contingencies59

Commitments and Contingencies (Narrative) (Details)	3 Months Ended
	Mar. 31, 2018USD ($)plaintiffitem
Commitments And Contingencies [Line Items]
Obligation under transportation agreements | $	$ 9,125,000,000
Guarantee obligations relative to the firms transportation agreements and gathering project and services | $	832,000,000
Indemnification liability | $	$ 0
Arkansas Royalty Litigation [Member] | Arkansas State Court [Member]
Commitments And Contingencies [Line Items]
Number of actions | item	2
Number of state cases set for trial | item	1
Number of cases | item	3
Number of plaintiffs | plaintiff	248
Number of cases removed to federal court | item	2
Pending Regulatory Approval and/or Construction [Member]
Commitments And Contingencies [Line Items]
Obligation under transportation agreements | $	$ 3,139,000,000

Commitments and Contingencies60

Commitments and Contingencies (Schedule of Future Obligation under Transportation Agreements) (Details) $ in Millions	Mar. 31, 2018USD ($)
Other Commitments [Line Items]
Total	$ 9,125
Less than 1 year	685
1 to 3 years	1,525
3 to 5 years	1,283
5 to 8 years	1,777
More than 8 years	3,855
Infrastructure Currently in Service [Member]
Other Commitments [Line Items]
Total	5,986
Less than 1 year	639
1 to 3 years	1,208
3 to 5 years	894
5 to 8 years	1,151
More than 8 years	2,094
Pending Regulatory Approval and/or Construction [Member]
Other Commitments [Line Items]
Total	3,139
Less than 1 year	46
1 to 3 years	317
3 to 5 years	389
5 to 8 years	626
More than 8 years	$ 1,761

Pension Plan and Other Postre61

Pension Plan and Other Postretirement Benefits (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 3
Company's expected additional annual contribution	9
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost (gain)	3	$ 3
Benefit obligation	41		$ 42
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost (gain)	1	$ 1
Benefit obligation	$ 18		$ 17
Supplemental Employee Retirement Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Common stock purchased under the terms of the Non-Qualified Plan presented as treasury stock	31,269		31,269

Pension Plan and Other Postre62

Pension Plan and Other Postretirement Benefits (Pension and Other Postretirement Benefit Costs) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 3	$ 2
Interest cost	2	1
Expected return on plan assets	(2)	(1)
Amortization of prior service cost
Amortization of net loss		1
Net periodic benefit cost	3	3
Other Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost	$ 1	$ 1

Stock-Based Compensation (Narra

Stock-Based Compensation (Narrative) (Details) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)shares
Stock-Based Compensation [Abstract]
Equity-classified awards, unrecognized compensation cost	$ 49
Equity-classified awards, weighted average period over which unrecognized cost is recognized, years	2 years
Liability-classified restricted stock, vesting period	4 years
Liability-classified restricted stock, unvested | shares	12
Liability-classified restricted stock, unrecognized compensation cost	$ 51
Liability-classified restricted stock, weighted average period over which unrecognized cost is recognized, years	4 years
Liability-classified performance units, vesting period	3 years
Liability-classified performance units, unvested | shares	3
Liability-classified performance units, unrecognized compensation cost	$ 14
Liability-classified performance units, weighted average period over which unrecognized cost is recognized, years	3 years

Stock-Based Compensation (Sched

Stock-Based Compensation (Schedule of Stock-Based Compensation Costs) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Stock-Based Compensation [Abstract]
Stock-based compensation cost - expensed	$ 5	$ 6
Stock-based compensation cost - capitalized	$ 3	$ 4

Stock-Based Compensation (Sch65

Stock-Based Compensation (Schedule of Equity-Classified Stock-Based Compensation Costs) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Stock-Based Compensation [Abstract]
Equity-classified stock-based compensation cost - expensed	$ 4	$ 6
Equity-classified stock-based compensation cost - capitalized	$ 3	$ 4

Stock-Based Compensation (Summa

Stock-Based Compensation (Summary of Equity-Classified Stock Option Activity) (Details) - Stock Options [Member] shares in Thousands	3 Months Ended
	Mar. 31, 2018$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding at December 31, 2017, Number of Options | shares	6,020
Granted, Number of Options | shares
Exercised, Number of Options | shares
Forfeited or expired, Number of Options | shares	(3)
Outstanding at March 31, 2018, Number of Options | shares	6,017
Exercisable at March 31, 2018, Number of Options | shares	4,379
Outstanding at December 31, 2017, Weighted Average Exercise Price | $ / shares	$ 19.43
Granted, Weighted Average Exercise Price | $ / shares
Exercised, Weighted Average Exercise Price | $ / shares
Forfeited or expired, Weighted Average Exercise Price | $ / shares	38.65
Outstanding at March 31, 2018, Weighted Average Exercise Price | $ / shares	19.42
Exercisable at March 31, 2018, Weighted Average Exercise Price | $ / shares	$ 23.80

Stock-Based Compensation (Sum67

Stock-Based Compensation (Summary of Equity-Classified Restricted Stock Activity) (Details) - Restricted Stock [Member] shares in Thousands	3 Months Ended
	Mar. 31, 2018$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested shares/units at December 31, 2017, Number of Shares/Units | shares	6,254
Granted, Number of Shares/Units | shares	5
Vested, Number of Shares/Units | shares	(1,033)
Forfeited, Number of Shares/Units | shares	(160)
Unvested shares/units at March 31, 2018, Number of Shares/Units | shares	5,066
Unvested shares/units at December 31, 2017, Weighted Average Fair Value | $ / shares	$ 8.85
Granted, Weighted Average Fair Value | $ / shares	5.91
Vested, Weighted Average Fair Value | $ / shares	8.77
Forfeited, Weighted Average Fair Value | $ / shares	9.07
Unvested shares at March 31, 2018, Weighted Average Fair Value | $ / shares	$ 8.85

Stock-Based Compensation (Sum68

Stock-Based Compensation (Summary of Equity-Classified Performance Units Activity) (Details) - Performance Units [Member]	3 Months Ended
	Mar. 31, 2018$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested shares/units at December 31, 2017, Number of Shares/Units	1,084,000
Granted, Number of Shares/Units
Vested, Number of Shares/Units
Forfeited, Number of Shares/Units	(18,000)
Unvested shares/units at March 31, 2018, Number of Shares/Units	1,066,000
Unvested shares/units at December 31, 2017, Weighted Average Fair Value | $ / shares	$ 10.12
Granted, Weighted Average Fair Value | $ / shares
Vested, Weighted Average Fair Value | $ / shares
Forfeited, Weighted Average Fair Value | $ / shares	9.99
Unvested shares at March 31, 2018, Weighted Average Fair Value | $ / shares	$ 10.12
Vesting period for stock awards from grant date	3 years
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, Number of Shares/Units	0
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, Number of Shares/Units	2

Stock-Based Compensation (Sch69

Stock-Based Compensation (Schedule of Liability-Classified Stock-Based Compensation Costs) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)
Liability-classified stock-based compensation cost - expensed	$ 1
Liability-classified stock-based compensation cost - capitalized
Maximum [Member]
Liability-classified stock-based compensation cost - capitalized	$ 1

Segment Information (Details)

Segment Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Revenues	$ 920	$ 846
Depreciation, depletion and amortization expense	143	106
Operating income	255	266
Interest expense	39	32
Gain (loss) on derivatives	(7)	116
Other income (loss), net	(1)	1
Assets	7,713	7,196	$ 7,521
Capital investments	338	290
Cash and cash equivalents	958	1,382	$ 916	$ 1,423
Change in accrued expenditures	33	(52)
Marketing	253	253
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	(613)	(575)
Marketing	(576)	(524)
E&P [Member]
Segment Reporting Information [Line Items]
Revenues	643	566
Depreciation, depletion and amortization expense	117	90
Operating income	238	225
Interest expense	39	32
Gain (loss) on derivatives	(7)	116
Other income (loss), net		2
Assets	5,346	4,413
Capital investments	334	283
E&P [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	6	3
Midstream [Member]
Segment Reporting Information [Line Items]
Revenues	277	280
Depreciation, depletion and amortization expense	26	16
Operating income	17	41
Other income (loss), net	(1)
Assets	1,217	1,268
Capital investments	4	6
Impairment of natural gas and oil properties	10
Marketing	829	777
Midstream [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	(619)	(578)
Marketing	576	524
Other [Member]
Segment Reporting Information [Line Items]
Other income (loss), net		(1)
Assets	1,150	1,515
Capital investments		1
Cash and cash equivalents	$ 958	$ 1,400

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2018
Income Taxes [Line Items]
Effective tax rate	0.00%	0.00%
Decrease in valuation allowance	$ 51	$ 75
Scenario, Plan [Member]
Income Taxes [Line Items]
Corporate income tax rate			21.00%

Subsequent Events (Narrative) (

Subsequent Events (Narrative) (Details)	Apr. 26, 2018USD ($)	Jun. 30, 2020	Mar. 31, 2018USD ($)	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2017USD ($)	Jun. 30, 2016USD ($)
2018 Credit Facility [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Line of credit, amount borrowed	$ 360,000,000
Long-term Debt [Member]
Debt Instrument [Line Items]
Debt instrument			$ 4,433,000,000			$ 4,433,000,000
Long-term Debt [Member] | 2016 Credit Facility [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity			743,000,000				$ 743,000,000
Line of credit, amount borrowed			0
Long-term Debt [Member] | 2018 Credit Facility [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Maximum borrowing capacity	3,500,000,000
Amount outstanding	2,000,000,000
Current borrowing capacity	$ 3,200,000,000
Credit facility, maturity date	Apr. 26, 2023
Amount to be amended, redeemed or refinanced to avoid acceleration	$ 700,000,000
Accelerated maturity date if not amended, redeemed or refinanced	Dec. 14, 2021
Line of credit, amount borrowed	$ 360,000,000
Long-term Debt [Member] | 2018 Credit Facility [Member] | Minimum [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Minimum interest coverage ratio	1
Long-term Debt [Member] | 2018 Credit Facility [Member] | Maximum [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Leverage ratio, percentage of credit limit	10.00%
Leverage ratio, amount of credit limit	$ 150,000,000
Long-term Debt [Member] | 2018 Credit Facility [Member] | Maximum [Member] | Scenario, Forecast [Member]
Debt Instrument [Line Items]
Leverage ratio		4		4.25	4.50
Long-term Debt [Member] | 2018 Credit Facility [Member] | Eurodollar [Member] | Minimum [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Basis points	1.50%
Long-term Debt [Member] | 2018 Credit Facility [Member] | Eurodollar [Member] | Maximum [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Basis points	2.50%
Long-term Debt [Member] | 2018 Credit Facility [Member] | Base Rate [Member] | Minimum [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Basis points	0.50%
Long-term Debt [Member] | 2018 Credit Facility [Member] | Base Rate [Member] | Maximum [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Basis points	1.50%
Long-term Debt [Member] | Letter of Credit [Member]
Debt Instrument [Line Items]
Amount outstanding	$ 323,000,000		323,000,000
2016 Term Loan due December 2020 [Member] | Long-term Debt [Member]
Debt Instrument [Line Items]
Debt instrument			$ 1,191,000,000			$ 1,191,000,000	$ 1,191,000,000
2016 Term Loan due December 2020 [Member] | Long-term Debt [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Repayments of long-term debt	$ 1,191,000,000