Anadarko Petroleum 10-Q 30 Oct 18 2018 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Oct. 18, 2018
Document And Entity Information [Abstract]
Trading Symbol	APC
Entity Registrant Name	ANADARKO PETROLEUM CORP
Entity Central Index Key	773,910
Document Type	10-Q
Document Period End Date	Sep. 30, 2018
Amendment Flag	false
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		504,280,902

CONSOLIDATED STATEMENTS OF INCO

CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Millions, $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2018		Sep. 30, 2017	Sep. 30, 2018		Sep. 30, 2017
Revenues and Other
Revenues from Customers	$ 3,851			$ 10,501
Gains (losses) on divestitures and other, net	90		$ (114)	232		$ 1,052
Total	3,697		2,496	10,033		8,979
Costs and Expenses
Oil and gas operating	294		253	845		738
Oil and gas transportation	228		220	633		698
Exploration	118	[1]	750	380	[1]	2,366
General and administrative	248		261	814		768
Depreciation, depletion, and amortization	1,130		1,083	3,123		3,235
Production, property, and other taxes	246		159	637		449
Impairments	172		0	319		383
Other operating expense	26		123	188		157
Total	2,718		3,245	7,684		9,895
Operating Income (Loss)	979		(749)	2,349		(916)
Other (Income) Expense
Interest expense	240		230	705		682
(Gains) losses on derivatives, net	33		82	506		(33)
Other (income) expense, net	24		5	16		51
Total	296		317	1,224		700
Income (Loss) Before Income Taxes	683		(1,066)	1,125		(1,616)
Income tax expense (benefit)	256		(425)	507		(366)
Net Income (Loss)	427		(641)	618		(1,250)
Net income (loss) attributable to noncontrolling interests	64		58	105		182
Net Income (Loss) Attributable to Common Stockholders	$ 363		$ (699)	$ 513		$ (1,432)
Per Common Share
Net income (loss) attributable to common stockholders—basic (in usd per share)	$ 0.72		$ (1.27)	$ 0.99		$ (2.60)
Net income (loss) attributable to common stockholders—diluted (in usd per share)	$ 0.72		$ (1.27)	$ 0.99		$ (2.61)
Average Number of Common Shares Outstanding—Basic	499		553	507		552
Average Number of Common Shares Outstanding—Diluted	500		553	508		552
Dividends (in usd per share)	$ 0.25		$ 0.05	$ 0.75		$ 0.15
Commodity Contract and Interest Rate Swap [Member]
Other (Income) Expense
(Gains) losses on derivatives, net	$ 32		$ 82	$ 503		$ (33)
Oil sales [Member]
Revenues and Other
Revenues from Customers	2,572		1,567	6,964		4,652
Natural gas sales [Member]
Revenues and Other
Revenues from Customers	232		269	682		1,090
Natural-gas liquids sales [Member]
Revenues and Other
Revenues from Customers	382		265	992		768
Gathering, processing, and marketing [Member]
Revenues and Other
Revenues from Customers	421		509	1,163		1,417
Costs and Expenses
Gathering, processing, and marketing	$ 256		$ 396	$ 745		$ 1,101
[1]	Includes restructuring charges of $20 million for the three and nine months ended September 30, 2018.

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Net Income (Loss)	$ 427	$ (641)	$ 618	$ (1,250)
Adjustments for derivative instruments
Reclassification of previously deferred derivative losses to (gains) losses on derivatives, net	1	1	2	3
Income taxes on reclassification of previously deferred derivative losses	0	0	0	(1)
Total adjustments for derivative instruments, net of taxes	1	1	2	2
Adjustments for pension and other postretirement plans
Net gain (loss) incurred during period	25	(14)	25	1
Income taxes on net gain (loss) incurred during period	(6)	5	(6)	0
Amortization of net actuarial (gain) loss to other (income) expense, net	15	29	28	100
Income taxes on amortization of net actuarial (gain) loss	(4)	(11)	(7)	(37)
Amortization of net prior service (credit) cost to other (income) expense, net	(6)	(7)	(18)	(19)
Income taxes on amortization of net prior service (credit) cost	2	3	4	7
Total adjustments for pension and other postretirement plans, net of taxes	26	5	26	52
Total	27	6	28	54
Comprehensive Income (Loss)	454	(635)	646	(1,196)
Comprehensive income (loss) attributable to noncontrolling interests	64	58	105	182
Comprehensive Income (Loss) Attributable to Common Stockholders	$ 390	$ (693)	$ 541	$ (1,378)

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions		Sep. 30, 2018	Dec. 31, 2017
Current Assets
Cash and cash equivalents ($133 and $80 related to VIEs)		$ 1,883	$ 4,553
Accounts receivable (net of allowance of $11 and $14)
Customers ($159 and $106 related to VIEs)		1,644	1,222
Others ($15 and $19 related to VIEs)		547	607
Other current assets		397	380
Total		4,471	6,762
Net Properties and Equipment (net of accumulated depreciation, depletion, and amortization of $36,375 and $34,107) ($6,419 and $5,731 related to VIEs)		28,744	27,451
Other Assets ($801 and $579 related to VIEs)		2,292	2,211
Goodwill and Other Intangible Assets ($1,170 and $1,191 related to VIEs)		5,638	5,662
Total Assets		41,145	42,086
Accounts payable
Trade ($337 and $305 related to VIEs)		2,144	1,894
Other ($16 and $1 related to VIEs)		201	266
Short-term debt		938	142
Current asset retirement obligations		332	294
Other current liabilities		1,502	1,310
Total		5,117	3,906
Long-term Debt		15,755	15,547
Other Long-term Liabilities
Deferred income taxes		2,455	2,234
Asset retirement obligations ($158 and $143 related to VIEs)		2,538	2,500
Other		4,043	4,109
Total		9,036	8,843
Stockholders’ equity
Common stock, par value $0.10 per share (1.0 billion shares authorized, 576.2 million and 574.2 million shares issued)		57	57
Paid-in capital		12,344	12,000
Retained earnings		1,291	1,109
Treasury stock (82.3 million and 43.4 million shares)		(4,608)	(2,132)
Accumulated other comprehensive income (loss)		(383)	(338)
Total Stockholders’ Equity		8,701	10,696
Noncontrolling interests		2,536	3,094
Total Equity		11,237	13,790
Total Liabilities and Equity		41,145	42,086
Anadarko [Member]
Accounts payable
Short-term debt	[1]	910	142
Long-term Debt		11,189	12,054
WES and WGP [Member]
Accounts payable
Short-term debt		28	0
Long-term Debt		$ 4,566	$ 3,493
[1]	Excludes WES and WGP.

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Current Assets
Cash and cash equivalents	$ 1,883	$ 4,553
Accounts receivable
Allowance for uncollectible accounts	11	14
Customers	1,644	1,222
Others	547	607
Property, Plant and Equipment, Net [Abstract]
Net properties and equipment related to VIEs	28,744	27,451
Accumulated depreciation, depletion and amortization	36,375	34,107
Other Assets	2,292	2,211
Goodwill and Other Intangible Assets	5,638	5,662
Accounts payable
Trade	2,144	1,894
Other	201	266
Other Long-term Liabilities
Asset retirement obligations	$ 2,538	$ 2,500
Stockholders’ equity
Common stock, par value per share (in usd per share)	$ 0.1	$ 0.10
Common stock, shares authorized	1,000,000,000	1,000,000,000
Common stock, shares issued	576,200,000	574,200,000
Treasury stock, shares	82,300,000	43,400,000
Variable Interest Entity, Primary Beneficiary [Member]
Current Assets
Cash and cash equivalents	$ 133	$ 80
Accounts receivable
Customers	159	106
Others	15	19
Property, Plant and Equipment, Net [Abstract]
Net properties and equipment related to VIEs	6,419	5,731
Other Assets	801	579
Goodwill and Other Intangible Assets	1,170	1,191
Accounts payable
Trade	337	305
Other	16	1
Other Long-term Liabilities
Asset retirement obligations	$ 158	$ 143

CONSOLIDATED STATEMENT OF EQUIT

CONSOLIDATED STATEMENT OF EQUITY - 9 months ended Sep. 30, 2018 - USD ($) $ in Millions		Total	Subsidiary Equity Transactions [Member]	Equity Component of 7.50% Tangible Equity Units [Member]	Common Stock [Member]	Paid-in Capital [Member]	Paid-in Capital [Member]Subsidiary Equity Transactions [Member]	Paid-in Capital [Member]Equity Component of 7.50% Tangible Equity Units [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Noncontrolling Interests [Member]	Noncontrolling Interests [Member]Subsidiary Equity Transactions [Member]	Noncontrolling Interests [Member]Equity Component of 7.50% Tangible Equity Units [Member]
Balance at Dec. 31, 2017		$ 13,790			$ 57	$ 12,000			$ 1,109	$ (2,132)	$ (338)	$ 3,094
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)		618							513			105
Common stock issued		6				6
Share-based compensation expense		125				125
Dividends—common stock		(380)							(380)
Repurchases of common stock		(2,476)								(2,476)
Subsidiary equity transactions			$ 8				$ (17)						$ 25
Settlement of tangible equity units				$ (70)				$ 230						$ (300)
Distributions to noncontrolling interest owners		(365)										(365)
Reclassification of previously deferred derivative losses to (gains) losses on derivatives, net		2									2
Adjustments for pension and other postretirement plans		(26)									(26)
Balance at Sep. 30, 2018		11,237			$ 57	$ 12,344			1,291	$ (4,608)	(383)	2,536
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change	[1]	$ (47)							$ 49		$ (73)	$ (23)
[1]	Beginning January 1, 2018, the Company adopted ASU 2014-09, Revenue from Contracts with Customers (Topic 606), and ASU 2018-02, Income Statement - Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income. See Note 1—Summary of Significant Accounting Policies in the Notes to Consolidated Financial Statements for further information.

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash Flows from Operating Activities
Net income (loss)	$ 618	$ (1,250)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities
Depreciation, depletion, and amortization	3,123	3,235
Deferred income taxes	141	(1,026)
Dry hole expense and impairments of unproved properties	212	2,144
Impairments	319	383
(Gains) losses on divestitures, net	(31)	(815)
Total (gains) losses on derivatives, net	506	(33)
Operating portion of net cash received (paid) in settlement of derivative instruments	(433)	21
Other	224	227
Changes in assets and liabilities
(Increase) decrease in accounts receivable	(344)	(32)
Increase (decrease) in accounts payable and other current liabilities	230	(95)
Other items, net	(263)	(140)
Net cash provided by (used in) operating activities	4,302	2,619
Cash Flows from Investing Activities
Additions to properties and equipment	(4,891)	(3,538)
Divestitures of properties and equipment and other assets	393	3,480
Other, net	(161)	30
Net cash provided by (used in) investing activities	(4,659)	(28)
Cash Flows from Financing Activities
Borrowings, net of issuance costs	2,131	249
Repayments of debt	(1,176)	(42)
Financing portion of net cash received (paid) for derivative instruments	19	(160)
Increase (decrease) in outstanding checks	(13)	(58)
Dividends paid	(380)	(84)
Repurchases of common stock	(2,476)	(37)
Issuances of common stock	6	0
Distributions to noncontrolling interest owners	(365)	(327)
Payments of future hard-minerals royalty revenues conveyed	(50)	(50)
Other financing activities	(2)	(18)
Net cash provided by (used in) financing activities	(2,306)	(527)
Effect of exchange rate changes on cash, cash equivalents, restricted cash, and restricted cash equivalents	(18)	4
Net Increase (Decrease) in Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents	(2,681)	2,068
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents at Beginning of Period	4,674	3,308
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents at End of Period	$ 1,993	$ 5,376

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	1. Summary of Significant Accounting Policies General Anadarko Petroleum Corporation is engaged in the exploration, development, production, and sale of oil, natural gas, and NGLs and in advancing its Mozambique LNG project toward FID. In addition, the Company engages in gathering, compressing, treating, processing, and transporting of natural gas; gathering, stabilizing, and transporting of oil and NGLs; and gathering and disposing of produced water. The Company also participates in the hard-minerals business through royalty arrangements. Basis of Presentation The accompanying unaudited consolidated financial statements have been prepared in accordance with U.S. Generally Accepted Accounting Principles for interim financial information and the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, certain notes and other information have been condensed or omitted. The accompanying interim financial statements reflect all normal recurring adjustments that are, in the opinion of management, necessary for the fair presentation of the Company’s consolidated financial statements. Certain prior-period amounts have been reclassified to conform to the current-period presentation. These interim financial statements should be read in conjunction with the consolidated financial statements and accompanying notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017 . The consolidated financial statements include the accounts of Anadarko and subsidiaries in which Anadarko holds, directly or indirectly, more than 50% of the voting rights and VIEs for which Anadarko is the primary beneficiary. The Company has determined that WGP and WES are VIEs. Anadarko is considered the primary beneficiary and consolidates WGP and WES. WGP and WES function with capital structures that are separate from Anadarko, consisting of their own debt instruments and publicly traded common units. All intercompany transactions have been eliminated. Undivided interests in oil and natural-gas exploration and production joint ventures are consolidated on a proportionate basis. Investments in noncontrolled entities that Anadarko has the ability to exercise significant influence over operating and financial policies and VIEs for which Anadarko is not the primary beneficiary are accounted for using the equity method. In applying the equity method of accounting, the investments are initially recognized at cost and subsequently adjusted for the Company’s proportionate share of earnings, losses, and distributions. Investments are included in other assets. Recently Adopted Accounting Standards ASU 2017-07, Compensation—Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost , requires presentation of service cost in the same line item(s) as other compensation costs arising from services rendered by employees during the period and presentation of the remaining components of net benefit cost in a separate line item outside operating items. Additionally, only the service cost component of net benefit cost will be eligible for capitalization. The Company adopted this ASU on January 1, 2018, with retrospective presentation of the service cost component and the other components of net benefit cost in the income statement and prospective presentation for the capitalization of the service cost component of net benefit cost in assets. Upon adoption, non-service cost components of net periodic benefit costs of $107 million for 2017, including $94 million for the nine months ended September 30, 2017 , were reclassified to other (income) expense, net, from G&A; oil and gas operating; gathering, processing, and marketing; and exploration expense. ASU 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash , requires an entity to explain the changes in the total of cash, cash equivalents, restricted cash, and restricted cash equivalents on the statement of cash flows and to provide a reconciliation of the totals in that statement to the related captions in the balance sheet when the cash, cash equivalents, restricted cash, and restricted cash equivalents are presented in more than one line item on the balance sheet. The Company adopted this ASU using a retrospective approach on January 1, 2018. Adoption did not have a material impact on the Company’s consolidated financial statements. See Consolidated Statements of Cash Flows and Note 17—Supplemental Cash Flow Information for additional information. 1. Summary of Significant Accounting Policies (Continued) ASU 2014-09, Revenue from Contracts with Customers (Topic 606) , supersedes the revenue recognition requirements and industry-specific guidance under Revenue Recognition ( Topic 605) . Topic 606 requires an entity to recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration the entity expects to be entitled to in exchange for those goods or services. The Company adopted Topic 606 on January 1, 2018, using the modified retrospective method applied to contracts that were not completed as of January 1, 2018. Under the modified retrospective method, prior-period financial positions and results will not be adjusted. The cumulative effect adjustment recognized in the opening balances included a reduction to total equity of $47 million . While the Company does not expect 2018 net earnings to be materially impacted by revenue recognition timing changes, Topic 606 requires certain changes to the presentation of revenues and related expenses beginning January 1, 2018. See Note 2—Revenue from Contracts with Customers for additional information. The Company’s revenue recognition accounting policy effective January 1, 2018, is detailed below. • Exploration and Production —The Company’s oil is sold primarily to marketers, gatherers, and refiners. Natural gas is sold primarily to interstate and intrastate natural-gas pipelines, direct end-users, industrial users, local distribution companies, and natural-gas marketers. NGLs are sold primarily to direct end-users, refiners, and marketers. Payment is generally received from the customer in the month following delivery. Contracts with customers have varying terms, including spot sales or month-to-month contracts, contracts with a finite term, and life-of-field contracts where all production from a well or group of wells is sold to one or more customers. The Company recognizes sales revenues for oil, natural gas, and NGLs based on the amount of each product sold to a customer when control transfers to the customer. Generally, control transfers at the time of delivery to the customer at a pipeline interconnect, the tailgate of a processing facility, or as a tanker lifting is completed. Revenue is measured based on the contract price, which may be index-based or fixed, and may include adjustments for market differentials and downstream costs incurred by the customer, including gathering, transportation, and fuel costs. For natural gas and NGLs sold on our behalf by a processor, revenue is typically measured based on the price the processor receives for the sale, less certain costs withheld by the processor. Revenues are recognized for the sale of Anadarko’s net share of production volumes. Sales on behalf of other working interest owners and royalty interest owners are not recognized as revenues. The Company enters into buy/sell arrangements related to the transportation of a portion of its oil production. Under these arrangements, barrels are sold to a third party at a location-based contract price and subsequently repurchased by the Company at a downstream location. The difference in value between the sale and purchase price represents the transportation fee to move oil from the lease or certain gathering locations to more liquid markets. These arrangements are often required by private transporters. These buy/sell transactions are recorded net in oil and gas transportation expense in the Company’s Consolidated Statements of Income. 1. Summary of Significant Accounting Policies (Continued) • WES Midstream and Other Midstream —Anadarko provides gathering, compressing, treating, processing, stabilizing, transporting, and disposal services pursuant to a variety of contracts. Under these arrangements, the Company receives fees and/or retains a percentage of products or a percentage of the proceeds from the sale of the customer’s products. These revenues are included in gathering, processing, and marketing sales in the Company’s Consolidated Statements of Income. Payment is generally received from the customer in the month of service or the month following the service. Contracts with customers generally have initial terms ranging from 5 to 10 years. Revenue is recognized for fee-based gathering and processing services in the month of service based on the volumes delivered by the customer. Revenues are valued based on the rate in effect for the month of service when the fee is either the same rate per unit over the contract term or when the fee escalates and the escalation factor approximates inflation. The Company may charge additional service fees to customers for a portion of the contract term (i.e., for the first year of a contract or until reaching a volume threshold) due to the significant upfront capital investment. These fees are recognized as revenue over the expected period of customer benefit, generally the life of the related properties. Deficiency fees, which are charged to the customer if they do not meet minimum delivery requirements, are recognized over the performance period based on an estimate of the deficiency fees that will be billed upon completion of the performance period. The Company’s midstream business also purchases natural-gas volumes from producers at the wellhead or production facility, typically at an index price, and charges the producer fees associated with the downstream gathering and processing services. These fees are treated as a reduction of the purchase cost when the fees relate to services performed after control of the product has transferred to Anadarko. Revenue is recognized, along with cost of product expense related to the sale, when the purchased product is sold to a third party. Revenue from percentage of proceeds gathering and processing contracts is recognized net of the cost of product for purchases from service customers when the Company is acting as their agent in the product sale, and any fees charged on these percentage of proceeds contracts are recognized in service revenues. ASU 2018-02, Income Statement - Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income , provides entities the option to reclassify stranded tax effects resulting from the Tax Reform Legislation from accumulated other comprehensive income (AOCI) to retained earnings. In accordance with its accounting policy, the Company releases stranded income tax effects from AOCI in the period the underlying portfolio is liquidated. This ASU allows for the reclassification of stranded tax effects as a result of the change in tax rates from Tax Reform Legislation to be recorded upon adoption of the ASU, rather than at the actual portfolio liquidation date. The Company adopted this ASU on January 1, 2018, electing to reclassify $73 million from AOCI to retained earnings, including a $2 million federal benefit of state tax impact related to the Tax Reform Legislation. New Accounting Standards Issued But Not Yet Adopted ASU 2016-02, Leases (Topic 842), requires lessees to recognize a lease liability and a right-of-use (ROU) asset for all leases, including operating leases, with a term greater than 12 months on the balance sheet. This ASU modifies the definition of a lease and outlines the recognition, measurement, presentation, and disclosure of leasing arrangements by both lessees and lessors. The Company plans to make certain elections allowing the Company not to reassess contracts that commenced prior to adoption, to continue applying its current accounting policy for existing or expired land easements, and not to recognize ROU assets or lease liabilities for short-term leases. Anadarko continues to review contracts in its portfolio of leased assets to assess the impact of adopting this ASU. The Company expects the adoption of this ASU to primarily impact other assets and other long-term liabilities and does not expect a material impact on its consolidated results of operations. To facilitate compliance with this ASU, Anadarko expects to implement new accounting software and complete the evaluation of its systems, processes, and internal controls by the end of 2018. Anadarko will adopt this ASU on January 1, 2019, using a modified retrospective approach. As permitted by ASU 2018-11, Leases (Topic 842): Targeted Improvements , the Company does not expect to adjust comparative-period financial statements and will recognize a cumulative effect adjustment in the opening balance of retained earnings in the period of adoption.

Revenue from Contracts with Cus

Revenue from Contracts with Customers	9 Months Ended
	Sep. 30, 2018
Revenue from Contract with Customer [Abstract]
Revenue from Contracts with Customers	2. Revenue from Contracts with Customers Change in Accounting Policy The Company adopted ASU 2014-09, Revenue from Contracts with Customers (Topic 606) , on January 1, 2018, using the modified retrospective method applied to contracts that were not completed as of January 1, 2018. See Note 1—Summary of Significant Accounting Policies for additional information. Impacts on Financial Statements Exploration and Production There were no significant changes to the timing or valuation of revenue recognized for sales of production by the Exploration and Production segment. WES Midstream and Other Midstream Gathering and processing revenues decreased for contracts where the Company is acting as an agent for its processing customer in the sale of processed volumes and increased for contracts with noncash consideration, with an offset to gathering and processing expense upon product sale. The magnitude of these presentation changes in subsequent periods is dependent on future customer volumes subject to the impacted contracts and commodity prices for those volumes. These presentation changes do not impact net earnings. The following tables summarize the impacts of adopting Topic 606 on the Company’s consolidated financial statements: CONSOLIDATED BALANCE SHEET Impact of Change in Accounting Policy millions As Reported Without Adoption of Topic 606 Effect of Change Increase/(Decrease) September 30, 2018 Assets Other current assets $ 397 $ 395 $ 2 Net properties and equipment 28,744 28,697 47 Other assets 2,292 2,282 10 Liabilities Other current liabilities 1,502 1,494 8 Deferred income taxes 2,455 2,461 (6 ) Other 4,043 3,932 111 Equity Total equity 11,237 11,291 (54 ) 2. Revenue from Contracts with Customers (Continued) CONSOLIDATED STATEMENT OF INCOME Impact of Change in Accounting Policy millions As Reported Without Adoption of Topic 606 Effect of Change Increase/(Decrease) Three Months Ended September 30, 2018 Revenues Gathering, processing, and marketing sales $ 421 $ 717 $ (296 ) Gains (losses) on divestitures and other, net 90 89 1 Expenses Gathering, processing, and marketing 256 551 (295 ) Income tax expense (benefit) 256 254 2 Net income (loss) attributable to noncontrolling interests 64 71 (7 ) Net Income (Loss) Attributable to Common Stockholders $ 363 $ 358 $ 5 Nine Months Ended September 30, 2018 Revenues Gathering, processing, and marketing sales $ 1,163 $ 1,944 $ (781 ) Gains (losses) on divestitures and other, net 232 233 (1 ) Expenses Gathering, processing, and marketing 745 1,520 (775 ) Income tax expense (benefit) 507 507 — Net income (loss) attributable to noncontrolling interests 105 111 (6 ) Net Income (Loss) Attributable to Common Stockholders $ 513 $ 514 $ (1 ) 2. Revenue from Contracts with Customers (Continued) Disaggregation of Revenue from Contracts with Customers The following table disaggregates revenue by significant product type and segment: millions Exploration WES Midstream Other Midstream Other and Total Three Months Ended September 30, 2018 Oil sales $ 2,572 $ — $ — $ — $ 2,572 Natural-gas sales 232 — — — 232 Natural-gas liquids sales 382 — — — 382 Gathering, processing, and marketing sales (1) — 511 113 1 625 Other, net 9 — — 31 40 Total Revenue from Customers $ 3,195 $ 511 $ 113 $ 32 $ 3,851 Gathering, processing, and marketing sales (2) — (3 ) 3 (204 ) (204 ) Gains (losses) on divestitures, net 5 — 1 (3 ) 3 Other, net (8 ) 52 12 (9 ) 47 Total Revenue from Other than Customers $ (3 ) $ 49 $ 16 $ (216 ) $ (154 ) Total Revenue and Other $ 3,192 $ 560 $ 129 $ (184 ) $ 3,697 Nine Months Ended September 30, 2018 Oil sales $ 6,964 $ — $ — $ — $ 6,964 Natural-gas sales 682 — — — 682 Natural-gas liquids sales 992 — — — 992 Gathering, processing, and marketing sales (1) — 1,438 255 83 1,776 Other, net 16 — — 71 87 Total Revenue from Customers $ 8,654 $ 1,438 $ 255 $ 154 $ 10,501 Gathering, processing, and marketing sales (2) — (6 ) 6 (613 ) (613 ) Gains (losses) on divestitures, net 24 — 10 (3 ) 31 Other, net (21 ) 113 30 (8 ) 114 Total Revenue from Other than Customers $ 3 $ 107 $ 46 $ (624 ) $ (468 ) Total Revenue and Other $ 8,657 $ 1,545 $ 301 $ (470 ) $ 10,033 __________________________________________________________________ (1) The amount in Other and Intersegment Eliminations primarily represents sales of third-party natural gas and NGLs of $328 million and intercompany eliminations of $(312) million for the three months ended September 30, 2018 , and sales of third-party natural gas and NGLs of $813 million and intercompany eliminations of $(715) million for the nine months ended September 30, 2018 . (2) The amount in Other and Intersegment Eliminations represents purchases of third-party natural gas and NGLs. Although these purchases are reported net in gathering, processing, and marketing sales in the Company’s Consolidated Statements of Income, they are shown separately on this table, as the purchases are not considered revenue from customers. 2. Revenue from Contracts with Customers (Continued) Contract Liabilities Contract liabilities primarily relate to midstream fees and capital reimbursements that are charged to customers for only a portion of the contract term and must be recognized as revenues over the expected period of benefit, fixed and variable fees that are received from customers but revenue recognition is deferred under midstream cost of service contracts, and hard-minerals bonus payments received from customers that must be recognized as revenue over the expected period of benefit. The following table summarizes the current period activity related to contract liabilities from contracts with customers: millions Balance at December 31, 2017 $ 37 Increase due to cumulative effect of adopting Topic 606 98 Increase due to cash received, excluding revenues recognized in the period (1) 46 Decrease due to revenue recognized (2) (30 ) Balance at September 30, 2018 $ 151 Contract liabilities at September 30, 2018 Other current liabilities $ 23 Other long-term liabilities - other 128 Total contract liabilities from contracts with customers $ 151 __________________________________________________________________ (1) Includes $(6) million for the three months ended September 30, 2018 . (2) Includes $(9) million for the three months ended September 30, 2018 . Transaction Price Allocated to Remaining Performance Obligations Revenue expected to be recognized from certain performance obligations that are unsatisfied as of September 30, 2018 , is reflected in the table below. The Company applies the optional exemptions in Topic 606 and does not disclose consideration for remaining performance obligations with an original expected duration of one year or less or for variable consideration related to unsatisfied performance obligations. Therefore, the following table represents only a small portion of Anadarko’s expected future consolidated revenues as future revenue from the sale of most products and services is dependent on future production or variable customer volumes and variable commodity prices for those volumes. millions Exploration WES Midstream Other Midstream Other and Total Remainder of 2018 $ 27 $ 124 $ 31 $ (96 ) $ 86 2019 104 480 204 (441 ) 347 2020 103 545 293 (606 ) 335 2021 103 525 361 (672 ) 317 2022 7 529 417 (739 ) 214 Thereafter 65 2,192 3,107 (4,662 ) 702 Total $ 409 $ 4,395 $ 4,413 $ (7,216 ) $ 2,001

Commodity Inventories

Commodity Inventories	9 Months Ended
	Sep. 30, 2018
Energy Related Inventory [Abstract]
Inventories	3. Commodity Inventories The following summarizes the major classes of commodity inventories included in other current assets: September 30, December 31, millions 2018 2017 Oil $ 168 $ 165 Natural gas 19 29 NGLs 131 122 Total commodity inventories $ 318 $ 316

Divestitures

Divestitures	9 Months Ended
	Sep. 30, 2018
Property, Plant and Equipment [Abstract]
Divestitures	4. Divestitures Divestitures The following summarizes the proceeds received and gains (losses) recognized on divestitures: Nine Months Ended September 30, millions 2018 2017 Proceeds received, net of closing adjustments $ 393 $ 3,480 Gains (losses) on divestitures, net (1) 31 815 __________________________________________________________________ (1) Includes the $126 million gain related to the 2017 property exchange discussed below. 2018 During the nine months ended September 30, 2018, the Company divested of the following U.S. onshore and Gulf of Mexico assets: • Alaska nonoperated assets, included in the Exploration and Production and Other Midstream reporting segments, for net proceeds of $370 million and net losses of $33 million in 2018 and $154 million in the fourth quarter of 2017 . • Ram Powell nonoperated assets in the Gulf of Mexico, included in the Exploration and Production reporting segment, resulting in a net gain of $67 million . 2017 During the nine months ended September 30, 2017, the Company divested of the following U.S. onshore assets: • Eagleford assets in South Texas, included in the Exploration and Production reporting segment, for net proceeds of $2.1 billion and a net gain of $730 million • Marcellus assets in Pennsylvania, included in the Exploration and Production and Other Midstream reporting segments, for net proceeds of $758 million and net losses of $56 million in 2017 and $129 million in the fourth quarter of 2016 • Eaglebine assets in Southeast Texas, included in the Exploration and Production reporting segment, for net proceeds of $533 million and a net gain of $282 million • Utah CBM assets, included in the Exploration and Production and WES Midstream reporting segments, for net proceeds of $69 million and a net loss of $52 million Property Exchange On March 17, 2017, WES acquired a third party’s 50% nonoperated interest in the DBJV System in exchange for WES’s 33.75% interest in nonoperated Marcellus midstream assets and $155 million in cash. WES recognized a gain of $126 million as a result of this transaction. Following the acquisition, the DBJV System is 100% owned by WES and consolidated by Anadarko.

Impairments

Impairments	9 Months Ended
	Sep. 30, 2018
Asset Impairment Charges [Abstract]
Impairments	5. Impairments Impairments of Long-Lived Assets 2018 During the nine months ended September 30, 2018, the Company expensed $319 million primarily related to the following: • $145 million in the third quarter of 2018 related to hard-minerals properties due to the Company’s primary consumer of coal stating its intent to retire its existing coal-fired power generation plant earlier than expected, coupled with the outlook for limited new markets for the Company’s coal in the Rockies region. These coal assets had a post-impairment fair value of $15 million . • $126 million related to a gathering system in the DJ basin, included in the WES Midstream reporting segment that was permanently taken out of service in the second quarter of 2018. 2017 During the nine months ended September 30, 2017, the Company expensed $383 million primarily related to the following: • $211 million related to oil and gas properties in the Gulf of Mexico, included in the Exploration and Production reporting segment, due to lower forecasted commodity prices at that time. The assets had a post-impairment fair value of $231 million . • $168 million related to U.S. onshore midstream properties, included in the WES Midstream reporting segment, primarily due to a reduced throughput fee as a result of a producer’s bankruptcy. The assets had a post-impairment fair value of $58 million . Fair values were measured as of the impairment date using the income approach and Level 3 inputs. The primary assumptions used to estimate undiscounted future net cash flows include anticipated future production, commodity prices, and capital and operating costs. Impairments of Unproved Properties Impairments of unproved properties are included in exploration expense in the Company’s Consolidated Statements of Income. During the nine months ended September 30, 2018, the Company recognized $158 million of impairments of unproved Gulf of Mexico properties primarily related to blocks where the Company determined it would no longer pursue activities. The Company recognized $586 million of impairments of unproved Gulf of Mexico properties during the nine months ended September 30, 2017, of which $463 million related to the Shenandoah project. The unproved property balance related to the Shenandoah project originated from the purchase price allocated to the Gulf of Mexico exploration projects from the acquisition of Kerr-McGee Corporation in 2006. It is reasonably possible that significant declines in commodity prices, further changes to the Company’s drilling plans in response to lower prices, reduction of proved and probable reserve estimates, or increases in drilling or operating costs could result in other additional impairments.

Exploratory Well Costs

Exploratory Well Costs	9 Months Ended
	Sep. 30, 2018
Capitalized Exploratory Well Costs [Abstract]
Exploratory Well Costs	6. Suspended Exploratory Well Costs The Company’s suspended exploratory well costs were $510 million at September 30, 2018, and $525 million at December 31, 2017 . For exploratory wells, drilling costs are capitalized, or “suspended,” on the balance sheet when the well has found a sufficient quantity of reserves to justify its completion as a producing well and sufficient progress is being made in assessing the reserves and the economic and operating viability of the project. If additional information becomes available that raises substantial doubt as to the economic or operational viability of any of these projects, the associated costs will be expensed at that time. During the nine months ended September 30, 2018, there was no exploration expense recorded for suspended exploratory well costs previously capitalized for greater than one year at December 31, 2017 .

Current Liabilities

Current Liabilities	9 Months Ended
	Sep. 30, 2018
Payables and Accruals [Abstract]
Current Liabilities	7. Current Liabilities Accounts Payable Accounts payable, trade included liabilities of $205 million at September 30, 2018 , and $219 million at December 31, 2017 , representing the amount by which checks issued but not presented to the Company’s banks for collection exceeded balances in applicable bank accounts. Changes in these liabilities are classified as cash flows from financing activities. Other Current Liabilities The following summarizes the Company’s other current liabilities: September 30, December 31, millions 2018 2017 Accrued income taxes $ 79 $ 71 Interest payable 169 246 Production, property, and other taxes payable 344 216 Accrued employee benefits 270 210 Derivatives 491 384 Other 149 183 Total other current liabilities $ 1,502 $ 1,310

Derivative Instruments

Derivative Instruments	9 Months Ended
	Sep. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments	8. Derivative Instruments Objective and Strategy The Company uses derivative instruments to manage its exposure to cash-flow variability from commodity-price and interest-rate risks. Futures, swaps, and options are used to manage exposure to commodity-price risk inherent in the Company’s oil and natural-gas production and natural-gas processing operations (Oil and Natural-Gas Production/Processing Derivative Activities). Futures contracts and commodity-price swap agreements are used to fix the price of expected future oil and natural-gas sales at major industry trading locations, such as Cushing, Oklahoma or Sullom Voe, Scotland for oil and Henry Hub, Louisiana for natural gas. Basis swaps are periodically used to fix or float the price differential between product prices at one market location versus another. Options are used to establish a floor price, a ceiling price, or a floor and a ceiling price (collar) for expected future oil and natural-gas sales. Derivative instruments are also used to manage commodity-price risk inherent in customer price requirements and to fix margins on the future sale of natural gas and NGLs from the Company’s leased storage facilities. 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 interest-rate changes. The fair value of the Company’s current interest-rate swap portfolio is subject to changes in interest rates. The Company does not apply hedge accounting to any of its derivative instruments. As a result, gains and losses associated with derivative instruments are recognized currently in earnings. Net derivative losses attributable to derivatives previously subject to hedge accounting reside in accumulated other comprehensive income (loss) and are reclassified to earnings as the transactions to which the derivatives relate are recognized in earnings. 8. Derivative Instruments (Continued) Oil and Natural-Gas Production/Processing Derivative Activities The oil prices listed below are a combination of NYMEX WTI and Intercontinental Exchange, Inc. (ICE) Brent Blend prices. The natural-gas prices listed below are NYMEX Henry Hub prices. The following is a summary of the Company’s derivative instruments related to oil and natural-gas production/processing derivative activities at September 30, 2018 : 2018 Settlement 2019 Settlement Oil Two-Way Collars (MBbls/d) 108 — Average price per barrel (WTI) Ceiling sold price (call) $ 60.48 $ — Floor purchased price (put) $ 50.00 $ — Three-Way Collars (MBbls/d) — 87 Average price per barrel (WTI and Brent) Ceiling sold price (call) $ — $ 72.98 Floor purchased price (put) $ — $ 56.72 Floor sold price (put) $ — $ 46.72 Fixed-Price Contracts (MBbls/d) 84 — Average price per barrel (Brent) $ 61.45 $ — Natural Gas Three-Way Collars (thousand MMBtu/d) 250 — Average price per MMBtu (Henry Hub) Ceiling sold price (call) $ 3.54 $ — Floor purchased price (put) $ 2.75 $ — Floor sold price (put) $ 2.00 $ — Fixed-Price Contracts (thousand MMBtu/d) 280 — Average price per MMBtu (Henry Hub) $ 3.02 $ — A two-way collar is a combination of two options: a sold call and a purchased put. The sold call establishes the maximum price that the Company will receive for the contracted commodity volumes. The purchased put establishes the minimum price that the Company will receive for the contracted volumes. A three-way collar is a combination of three options: a sold call, a purchased put, and a sold put. The sold call establishes the maximum price that the Company will receive for the contracted commodity volumes. The purchased put establishes the minimum price that the Company will receive for the contracted volumes unless the market price for the commodity falls below the sold put strike price, at which point the minimum price equals the reference price (e.g., NYMEX) plus the excess of the purchased put strike price over the sold put strike price. 8. Derivative Instruments (Continued) Interest-Rate Derivatives Anadarko has outstanding interest-rate swap contracts to manage interest-rate risk associated with anticipated debt issuances. The Company has locked in a fixed interest rate in exchange for a floating interest rate indexed to the three-month LIBOR. In August 2018, the Company amended an interest-rate swap with a notional principal amount of $200 million , extending the mandatory termination date from 2018 to 2023 in exchange for a cash payment of approximately $10 million . At September 30, 2018 , the Company had outstanding interest-rate swaps with a notional amount of $1.6 billion due prior to or in September 2023 that manage interest-rate risk associated with potential future debt issuances. Depending on market conditions, liability-management actions, or other factors, the Company may enter into offsetting interest-rate swap positions or settle or amend certain or all of the currently outstanding interest-rate swaps. The Company had the following outstanding interest-rate swaps at September 30, 2018 : millions except percentages Mandatory Weighted-Average Notional Principal Amount Reference Period Termination Date Interest Rate $ 550 September 2016 - 2046 September 2020 6.418% $ 250 September 2016 - 2046 September 2022 6.809% $ 100 September 2017 - 2047 September 2020 6.891% $ 250 September 2017 - 2047 September 2021 6.570% $ 450 September 2017 - 2047 September 2023 6.445% Derivative settlements and collateralization are classified as cash flows from operating activities unless the derivatives contain an other-than-insignificant financing element, in which case the settlements and collateralization are classified as cash flows from financing activities. As a result of prior extensions of reference-period start dates without settlement of the related interest-rate derivative obligations, the interest-rate derivatives in the Company’s portfolio contain an other-than-insignificant financing element, and therefore, any settlements, collateralization, or cash payments for amendments related to these extended interest-rate derivatives are classified as cash flows from financing activities. Net cash payments related to settlements and amendments of interest-rate swap agreements were $101 million during the nine months ended September 30, 2018, and $118 million during the nine months ended September 30, 2017 . 8. Derivative Instruments (Continued) Effect of Derivative Instruments — Balance Sheet The following summarizes the fair value of the Company’s derivative instruments: Gross Derivative Assets Gross Derivative Liabilities millions September 30, December 31, September 30, December 31, Balance Sheet Classification 2018 2017 2018 2017 Commodity derivatives Other current assets $ 2 $ 7 $ — $ (1 ) Other assets — 2 — — Other current liabilities 20 45 (440 ) (206 ) Other liabilities 15 — (56 ) (2 ) 37 54 (496 ) (209 ) Interest-rate derivatives Other current assets 21 14 — — Other assets 54 40 — — Other current liabilities — — (80 ) (236 ) Other liabilities — — (1,028 ) (1,183 ) 75 54 (1,108 ) (1,419 ) Total derivatives $ 112 $ 108 $ (1,604 ) $ (1,628 ) Effect of Derivative Instruments — Statement of Income The following summarizes gains and losses related to derivative instruments: Three Months Ended Nine Months Ended millions September 30, September 30, Classification of (Gain) Loss Recognized 2018 2017 2018 2017 Commodity derivatives Gathering, processing, and marketing sales $ 1 $ — $ 3 $ — (Gains) losses on derivatives, net 104 43 734 (164 ) Interest-rate derivatives (Gains) losses on derivatives, net (72 ) 39 (231 ) 131 Total (gains) losses on derivatives, net $ 33 $ 82 $ 506 $ (33 ) 8. Derivative Instruments (Continued) Credit-Risk Considerations The financial integrity of exchange-traded contracts, which are subject to nominal credit risk, is assured by NYMEX or ICE through systems of financial safeguards and transaction guarantees. Over-the-counter traded swaps, options, and futures contracts expose the Company to counterparty credit risk. The Company monitors the creditworthiness of its counterparties, establishes credit limits according to the Company’s credit policies and guidelines, and assesses the impact on the fair value of its counterparties’ creditworthiness. The Company has the ability to require cash collateral or letters of credit to mitigate its credit-risk exposure. The Company has netting agreements with financial institutions that permit net settlement of gross commodity derivative assets against gross commodity derivative liabilities and routinely exercises its contractual right to offset gains and losses when settling with derivative counterparties. In addition, the Company has setoff agreements with certain financial institutions that may be exercised in the event of default and provide for contract termination and net settlement across derivative types. The Company’s derivative instruments are subject to individually negotiated credit provisions that may require collateral of cash or letters of credit depending on the derivative’s portfolio valuation versus negotiated credit thresholds. These credit thresholds generally require full or partial collateralization of the Company’s obligations depending on certain credit-risk-related provisions, such as the Company’s credit rating from S&P and Moody’s. As of September 30, 2018 , the Company’s long-term debt was rated investment grade (BBB) by both S&P and Fitch and below investment grade (Ba1) by Moody’s. The Company may be required to post additional collateral with respect to its derivative instruments if its credit ratings decline below current levels or if the liability associated with any such derivative instrument increases substantially. For example, based on the derivative positions as of September 30, 2018 , if Anadarko’s credit rating were to be downgraded one level by either S&P or Moody’s, the Company could be required to post additional collateral of up to approximately $124 million . The aggregate fair value of derivative instruments with credit-risk-related contingent features for which a net liability position existed was $1.4 billion (net of $49 million of collateral) at September 30, 2018 , and $1.4 billion (net of $170 million of collateral) at December 31, 2017 . 8. Derivative Instruments (Continued) Fair Value Fair value of futures contracts is based on unadjusted quoted prices in active markets for identical assets or liabilities, which represent Level 1 inputs. Valuations of physical-delivery purchase and sale agreements, over-the-counter financial swaps, and commodity option collars are based on similar transactions observable in active markets and industry-standard models that primarily rely on market-observable inputs. Inputs used to estimate fair value in industry-standard models are categorized as Level 2 inputs because substantially all assumptions and inputs are observable in active markets throughout the full term of the instruments. Inputs used to estimate the fair value of swaps and options include market-price curves; contract terms and prices; credit-risk adjustments; and, for Black-Scholes option valuations, discount factors and implied market volatility. The following summarizes the fair value of the Company’s derivative assets and liabilities by input level within the fair-value hierarchy: millions Level 1 Level 2 Level 3 Netting (1) Collateral Total September 30, 2018 Assets Commodity derivatives $ — $ 37 $ — $ (35 ) $ — $ 2 Interest-rate derivatives — 75 — — — 75 Total derivative assets $ — $ 112 $ — $ (35 ) $ — $ 77 Liabilities Commodity derivatives $ — $ (496 ) $ — $ 35 $ 6 $ (455 ) Interest-rate derivatives — (1,108 ) — — 49 (1,059 ) Total derivative liabilities $ — $ (1,604 ) $ — $ 35 $ 55 $ (1,514 ) December 31, 2017 Assets Commodity derivatives $ 1 $ 53 $ — $ (46 ) $ (1 ) $ 7 Interest-rate derivatives — 54 — — — 54 Total derivative assets $ 1 $ 107 $ — $ (46 ) $ (1 ) $ 61 Liabilities Commodity derivatives $ (1 ) $ (208 ) $ — $ 46 $ 3 $ (160 ) Interest-rate derivatives — (1,419 ) — — 170 (1,249 ) Total derivative liabilities $ (1 ) $ (1,627 ) $ — $ 46 $ 173 $ (1,409 ) __________________________________________________________________ (1) Represents the impact of netting commodity derivative assets and liabilities with counterparties where the Company has the contractual right and intends to net settle.

Tangible Equity Units

Tangible Equity Units	9 Months Ended
	Sep. 30, 2018
Tangible Equity Units [Abstract]
Tangible Equity Units	9. Tangible Equity Units In June 2015, the Company issued 9.2 million 7.50% TEUs at a stated amount of $50.00 per TEU and raised net proceeds of $445 million . Each TEU was comprised of a prepaid equity purchase contract for common units of WGP and a senior amortizing note. The prepaid equity purchase contract was considered a freestanding financial instrument, indexed to WGP common units, and met the conditions for equity classification. Equity Component On June 7, 2018 , the mandatory settlement date, Anadarko settled 9.2 million outstanding TEUs in exchange for approximately 8.2 million WGP common units based on the determined final settlement rate of 0.8921 WGP common units per outstanding TEU. See settlement of tangible equity units in the Company’s Consolidated Statement of Equity. Debt Component Each senior amortizing note had an initial principal amount of $10.95 and bore interest at 1.50% per year. The final installment payment of $9 million was made on June 7, 2018 . For activity related to the senior amortizing notes, see Note 10—Debt .

Debt

Debt	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Debt	10. Debt Debt Activity The following summarizes the Company’s borrowing activity, after eliminating the effect of intercompany transactions, during the nine months ended September 30, 2018 : Carrying Value millions WES WGP (1) Anadarko (2) Anadarko Consolidated Description Balance at December 31, 2017 $ 3,465 $ 28 $ 11,965 $ 15,458 Issuances 394 — — 394 WES 4.500% Senior Notes due 2028 687 — — 687 WES 5.300% Senior Notes due 2048 396 — — 396 WES 4.750% Senior Notes due 2028 342 — — 342 WES 5.500% Senior Notes due 2048 Borrowings 320 — — 320 WES RCF Repayments (690 ) — — (690 ) WES RCF — — (114 ) (114 ) 7.050% Debentures due 2018 (350 ) — — (350 ) WES 2.600% Senior Notes due 2018 — — (17 ) (17 ) TEUs - senior amortizing notes Other, net 2 — 39 41 Amortization of discounts, premiums, and debt issuance costs Balance at September 30, 2018 $ 4,566 $ 28 $ 11,873 $ 16,467 __________________________________________________________________ (1) Excludes WES. (2) Excludes WES and WGP. 10. Debt (Continued) Debt The following summarizes the Company’s outstanding debt, including capital lease obligations, after eliminating the effect of intercompany transactions: millions WES WGP (1) Anadarko (2) Consolidated September 30, 2018 Total borrowings at face value $ 4,620 $ 28 $ 13,383 $ 18,031 Net unamortized discounts, premiums, and debt issuance costs (3) (54 ) — (1,510 ) (1,564 ) Total borrowings (4) 4,566 28 11,873 16,467 Capital lease obligations — — 226 226 Less short-term debt — 28 910 938 Total long-term debt $ 4,566 $ — $ 11,189 $ 15,755 December 31, 2017 Total borrowings at face value $ 3,490 $ 28 $ 13,514 $ 17,032 Net unamortized discounts, premiums, and debt issuance costs (3) (25 ) — (1,549 ) (1,574 ) Total borrowings (4) 3,465 28 11,965 15,458 Capital lease obligations — — 231 231 Less short-term debt — — 142 142 Total long-term debt $ 3,465 $ 28 $ 12,054 $ 15,547 __________________________________________________________________ (1) Excludes WES. (2) Excludes WES and WGP. (3) Unamortized discounts, premiums, and debt issuance costs are amortized over the term of the related debt. Debt issuance costs related to RCFs are included in other current assets and other assets on the Company’s Consolidated Balance Sheets. (4) The Company’s outstanding borrowings, except for borrowings under the WGP RCF, are senior unsecured. Fair Value The Company uses a market approach to determine the fair value of its fixed-rate debt using observable market data, which results in a Level 2 fair-value measurement. The carrying amount of floating-rate debt approximates fair value as the interest rates are variable and reflective of market rates. The estimated fair value of the Company’s total borrowings was $17.8 billion at September 30, 2018, and $17.7 billion at December 31, 2017 . 10. Debt (Continued) Anadarko Borrowings In January 2018 , the Company amended its $3.0 billion senior unsecured RCF to extend the maturity date to January 2022 (APC RCF) and amended its $2.0 billion 364 -day senior unsecured RCF to extend the maturity date to January 2019 ( 364 -Day Facility). At September 30, 2018, Anadarko had no outstanding borrowings under the APC RCF or the 364 -Day Facility and was in compliance with all covenants. At September 30, 2018, Anadarko had outstanding borrowings of $600 million of 8.700% Senior Notes due March 2019 and $300 million of 6.950% Senior Notes due June 2019 classified as short-term debt on the Company’s Consolidated Balance Sheet. Short-term debt also included the current portion of the Company’s capital lease obligations. Anadarko’s Zero Coupons can be put to the Company in October of each year, in whole or in part, for the then-accreted value of the outstanding Zero Coupons. None of the Zero Coupons were put to the Company in October 2018. The Zero Coupons can next be put to the Company in October 2019 , which, if put in whole, would be $980 million . The Company also has notes payable related to its ownership of certain noncontrolling mandatorily redeemable interests that are not included in the Company’s reported debt balance and do not affect consolidated interest expense. See Note 8—Equity-Method Investments in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017. WES and WGP Borrowings In February 2018, WES amended its RCF to extend the maturity date from February 2020 to February 2023 and expanded the borrowing capacity to $1.5 billion (WES RCF). As part of the amendment, the WES RCF is expandable to a maximum of $2.0 billion . During the nine months ended September 30, 2018, WES borrowed $320 million under its RCF, which was used for general partnership purposes, and made repayments of $690 million . At September 30, 2018, WES had no outstanding borrowings under its RCF, outstanding letters of credit of $5 million , available borrowing capacity of $1.495 billion , and was in compliance with all covenants. In August 2018, WES completed a public offering of $400 million aggregate principal amount of 4.750% Senior Notes due August 2028 and a public offering of $350 million aggregate principal amount of 5.500% Senior Notes due August 2048 . The net proceeds from the public offerings were used to repay the maturing WES $350 million of 2.600% Senior Notes due August 2018, and amounts outstanding under the WES RCF. The remaining net proceeds were used for general partnership purposes, including to fund capital expenditures. In March 2018, WES completed a public offering of $400 million aggregate principal amount of 4.500% Senior Notes due March 2028 and a public offering of $700 million aggregate principal amount of 5.300% Senior Notes due March 2048 . Net proceeds from the public offerings were used to repay amounts outstanding under the WES RCF and for general partnership purposes, including to fund capital expenditures. In February 2018, WGP voluntarily reduced the aggregate commitments of the lenders under its senior secured RCF maturing in March 2019 from $250 million to $35 million (WGP RCF). Obligations under the WGP RCF are secured by a first priority lien on all of WGP’s assets (not including the consolidated assets of WES) as well as all equity interests owned by WGP. At September 30, 2018, WGP had outstanding borrowings of $28 million at an interest rate of 4.25% , classified as short-term debt on the Company’s Consolidated Balance Sheet, and had available borrowing capacity of $7 million . At September 30, 2018, WGP was in compliance with all covenants.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	11. Income Taxes Upon enactment of the Tax Reform Legislation on December 22, 2017, the Company remeasured its U.S. deferred tax assets and liabilities based on the reduction of the U.S. corporate tax rate from 35% to 21% . During the third quarter of 2018, the Company recognized an additional net tax benefit of $5 million related to the adoption of the Tax Reform Legislation under Staff Accounting Bulletin 118. The Company expects to complete the accounting for the income tax effects related to the adoption of the Tax Reform Legislation, including its accounting policy related to Global Intangible Low Taxed Income, and record any remaining adjustments to provisional tax amounts, which could be material to income tax expense, before the end of the measurement period on December 21, 2018. See Note 13—Income Taxes in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017. The following summarizes income tax expense (benefit) and effective tax rates: Three Months Ended Nine Months Ended September 30, September 30, millions except percentages 2018 2017 2018 2017 Current income tax expense (benefit) $ 146 $ 430 $ 383 $ 670 Deferred income tax expense (benefit) 110 (855 ) 124 (1,036 ) Total income tax expense (benefit) $ 256 $ (425 ) $ 507 $ (366 ) Income (loss) before income taxes 683 (1,066 ) 1,125 (1,616 ) Effective tax rate 37 % 40 % 45 % 23 % The Company’s tax provision for interim periods is determined using an estimate of its annual current and deferred effective tax rates, adjusted for discrete items. Each quarter, the Company updates these rates and records a cumulative adjustment to current and deferred tax expense by applying the rates to the year-to-date pre-tax income excluding discrete items. The Company’s quarterly estimate of its annual current and deferred effective tax rates can vary significantly based on various forecasted items, including future commodity prices, capital expenditures, expenses for which tax benefits are not recognized, and the geographic mix of pre-tax income and losses. The variance from the U.S. federal statutory rate of 21% for the three and nine months ended September 30, 2018, was primarily attributable to the following items: • tax impact from foreign operations • non-deductible Algerian exceptional profits tax for Algerian income tax purposes The Company reported a loss before income taxes for the three and nine months ended September 30, 2017 . As a result, items that ordinarily increase or decrease the Company’s tax rate will have the opposite effect. The variance from the U.S. federal statutory rate of 35% for the three and nine months ended September 30, 2017 was primarily attributable to the following items: • tax impact from foreign operations • non-deductible Algerian exceptional profits tax for Algerian income tax purposes • net changes in uncertain tax positions • income attributable to noncontrolling interests 11. Income Taxes (Continued) The Company recognized a net tax benefit of $346 million as of September 30, 2018 and December 31, 2017 , related to the deduction of its 2015 settlement payment for the Tronox Adversary Proceeding. This benefit is net of uncertain tax positions of $1.2 billion as of September 30, 2018 and December 31, 2017 , due to uncertainty related to the deductibility of the settlement payment. Due to the deduction of the settlement payment, the Company had a net operating loss carryback for 2015, which resulted in a tentative tax refund of $881 million in 2016. The IRS has audited this position and, in April 2018, issued a final notice of proposed adjustment denying the deductibility of the settlement payment. In September 2018, the Company received a statutory notice of deficiency from the IRS disallowing the net operating loss carryback and rejecting the Company’s refund claim. As a result, the Company intends to file a petition with the U.S. Tax Court to dispute the disallowances, and pursuant to standard U.S. Tax Court procedures, the Company is not required to repay the $881 million refund to dispute the IRS’s position. Accordingly, the Company has not revised its estimate of the benefit that will ultimately be realized. After the case is tried and briefed in the Tax Court, the court will issue an opinion and then enter a decision. If the Company does not prevail on the issue, the earliest potential date the Company might be required to repay the refund received, plus interest, would be 91 days after entry of the decision. At such time, the Company would reverse the portion of the $346 million net benefit previously recognized in its consolidated financial statements to the extent necessary to reflect the result of the Tax Court decision. It is reasonably possible the amount of uncertain tax position and/or tax benefit could materially change as the Company asserts its position in the Tax Court proceedings. Although management cannot predict the timing of a final resolution of the Tax Court proceedings, the Company does not anticipate a decision to be entered within the next three years.

Contingencies

Contingencies	9 Months Ended
	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Contingencies	12. Contingencies Litigation There are no material developments in previously reported contingencies nor are there any other material matters that have arisen since the filing of the Company’s Annual Report on Form 10-K for the year ended December 31, 2017.

Pension Plans and Other Postret

Pension Plans and Other Postretirement Benefits	9 Months Ended
	Sep. 30, 2018
Retirement Benefits [Abstract]
Pension Plans and Other Postretirement Benefits	13. Pension Plans and Other Postretirement Benefits The Company has contributory and non-contributory defined-benefit pension plans, which include both qualified and supplemental plans. The Company also provides certain health care and life insurance benefits for certain retired employees. Retiree health care benefits are funded by contributions from the retiree and, in certain circumstances, contributions from the Company. The Company’s retiree life insurance plan is noncontributory. The following summarizes the Company’s pension and other postretirement benefit cost: Pension Benefits Other Benefits millions 2018 2017 2018 2017 Three Months Ended September 30 Service cost $ 23 $ 22 $ — $ — Interest cost 19 21 3 3 Expected (return) loss on plan assets (20 ) (21 ) — — Amortization of net actuarial loss (gain) 6 7 — — Amortization of net prior service cost (credit) — (1 ) (6 ) (6 ) Settlement expense 9 22 — — Termination benefits expense 7 — — — Net periodic benefit cost (1) $ 44 $ 50 $ (3 ) $ (3 ) Nine Months Ended September 30 Service cost $ 68 $ 64 $ 1 $ 1 Interest cost 57 63 8 9 Expected (return) loss on plan assets (61 ) (63 ) — — Amortization of net actuarial loss (gain) 19 20 — — Amortization of net prior service cost (credit) — (1 ) (18 ) (18 ) Settlement expense 9 80 — — Termination benefits expense 7 4 — — Net periodic benefit cost (1) $ 99 $ 167 $ (9 ) $ (8 ) __________________________________________________________________ (1) The service cost component of net periodic benefit cost is included in G&A; oil and gas operating expense; gathering, processing, and marketing expense; and exploration expense, and all other components of net periodic benefit cost are included in other (income) expense on the Company’s Consolidated Statements of Income. The Company contributed $161 million to funded pension plans and $36 million to unfunded pension plans during the nine months ended September 30, 2018 . The Company expects to contribute an additional $1 million to funded pension plans and $26 million to unfunded pension plans during 2018.

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Sep. 30, 2018
Stockholders' Equity Note [Abstract]
Stockholders' Equity	14. Stockholders’ Equity Earnings Per Share The Company’s basic earnings per share (EPS) is computed based on the average number of shares of common stock outstanding for the period and includes the effect of any participating securities and TEUs as appropriate. Diluted EPS includes the effect of the Company’s outstanding stock options, restricted stock awards, restricted stock units, and TEUs, if the inclusion of these items is dilutive. All outstanding TEUs were settled in June 2018. See Note 9—Tangible Equity Units for additional information. The following provides a reconciliation between basic and diluted EPS attributable to common stockholders: Three Months Ended Nine Months Ended September 30, September 30, millions except per-share amounts 2018 2017 2018 2017 Net income (loss) Net income (loss) attributable to common stockholders $ 363 $ (699 ) $ 513 $ (1,432 ) Income (loss) effect of TEUs — (2 ) (4 ) (6 ) Less distributions on participating securities 2 — 4 — Less undistributed income allocated to participating securities 2 — 1 — Basic $ 359 $ (701 ) $ 504 $ (1,438 ) Income (loss) effect of TEUs — — — (1 ) Diluted $ 359 $ (701 ) $ 504 $ (1,439 ) Shares Average number of common shares outstanding—basic 499 553 507 552 Dilutive effect of stock options 1 — 1 — Average number of common shares outstanding—diluted 500 553 508 552 Excluded due to anti-dilutive effect 8 11 9 11 Net income (loss) per common share Basic $ 0.72 $ (1.27 ) $ 0.99 $ (2.60 ) Diluted $ 0.72 $ (1.27 ) $ 0.99 $ (2.61 ) 14. Stockholders’ Equity (Continued) Common Stock The Company announced a $2.5 billion Share-Repurchase Program in September 2017, which was expanded to $3.0 billion in February 2018. In July 2018, the program was further expanded to $4.0 billion and extended through June 30, 2019. The Share-Repurchase Program authorizes the repurchase of the Company’s common stock in the open market or through private transactions. As of the end of the third quarter of 2018, the Company had completed $3.5 billion of the Share-Repurchase Program through ASR Agreements and open-market repurchases. These transactions were accounted for as equity transactions, with all of the repurchased shares classified as treasury stock. Additionally, the receipt of these shares reduced the average number of shares of common stock outstanding used to compute both basic and diluted EPS. During the nine months ended September 30, 2018 , the Company entered into and completed two ASR Agreements and open-market repurchases as presented below: millions except per-share amounts Agreement Date Settlement Date Amount Average Price per Share Initial Shares Delivered Additional Shares Delivered Total Shares Delivered ASR Agreements January 2018 February 2018 $ 500 $ 58.82 7.0 1.5 8.5 March 2018 June 2018 1,441 65.28 19.1 3.0 22.1 Total ASR Agreements 1,941 26.1 4.5 30.6 Open-market repurchases August 2018 August 2018 250 66.14 N/A N/A 3.8 September 2018 September 2018 250 63.11 N/A N/A 3.9 Total open-market repurchases 500 7.7 Total $ 2,441 38.3 Under each ASR Agreement, the Company paid a specific amount in cash and received an initial delivery of shares of the Company’s common stock. The initial delivery of shares represented the minimum number of shares to be repurchased under the agreement. The final number of shares delivered upon settlement of each ASR Agreement was determined with reference to the volume-weighted average price of the shares during the term of the agreement less a negotiated settlement price adjustment.

Noncontrolling Interests

Noncontrolling Interests	9 Months Ended
	Sep. 30, 2018
Noncontrolling Interest Items [Abstract]
Noncontrolling Interests	15. Noncontrolling Interests WES is a limited partnership formed by Anadarko to acquire, own, develop, and operate midstream assets. During 2016, WES issued 22 million Series A Preferred units to private investors. Pursuant to an agreement between WES and the holders of the Series A Preferred units, 50% of the Series A Preferred units converted into WES common units on a one-for-one basis on March 1, 2017, and all remaining Series A Preferred units were converted on May 2, 2017. WES Class C units issued to Anadarko will convert into WES common units on a one-for-one basis on the conversion date, which was extended in February 2017 from December 31, 2017, to March 1, 2020. The Class C units receive quarterly distributions in the form of additional Class C units until the March 1, 2020 conversion date, unless WES elects to convert the units to common units earlier or Anadarko elects to extend the conversion date. WES distributed 802 thousand Class C units to Anadarko during the nine months ended September 30, 2018, and 886 thousand Class C units to Anadarko during 2017. WGP is a limited partnership formed by Anadarko to own interests in WES. In June 2018, Anadarko settled 9.2 million outstanding TEUs, originally issued in 2015, in exchange for approximately 8.2 million WGP common units. See Note 9—Tangible Equity Units for additional information. At September 30, 2018, Anadarko’s ownership interest in WGP consisted of a 77.8% limited partner interest and the entire non-economic general partner interest. The remaining 22.2% limited partner interest in WGP was owned by the public. At September 30, 2018, WGP’s ownership interest in WES consisted of a 29.6% limited partner interest, the entire 1.5% general partner interest, and all of the WES incentive distribution rights. At September 30, 2018, Anadarko also owned a 9.5% limited partner interest in WES through other subsidiaries’ ownership of common and Class C units. The remaining 59.4% limited partner interest in WES was owned by the public.

Variable Interest Entities

Variable Interest Entities	9 Months Ended
	Sep. 30, 2018
Variable Interest Entities [Abstract]
Variable Interest Entities	16. Variable Interest Entities Consolidated VIEs The Company determined that the partners in WGP and WES with equity at risk lack the power, through voting rights or similar rights, to direct the activities that most significantly impact WGP’s and WES’s economic performance; therefore, WGP and WES are considered VIEs. Anadarko, through its ownership of the general partner interest in WGP, has the power to direct the activities that most significantly affect economic performance and the obligation to absorb losses or the right to receive benefits that could be potentially significant to WGP and WES; therefore, Anadarko is considered the primary beneficiary and consolidates WGP, WES, and all of their consolidated subsidiaries. For additional information on WGP and WES, see Note 15—Noncontrolling Interests . The following tables present selected financial data from the consolidated financial statements of WGP: Three Months Ended Nine Months Ended September 30, September 30, millions 2018 2017 2018 2017 Statement of Operations Data Total revenues and other $ 508 $ 575 $ 1,432 $ 1,616 Operating income (loss) 200 179 461 523 Net income (loss) 155 147 340 424 Nine Months Ended September 30, millions 2018 2017 Statement of Cash Flows Data Net cash provided by (used in) operating activities $ 749 $ 642 Net cash provided by (used in) investing activities (1,161 ) (515 ) Net cash provided by (used in) financing activities 465 (334 ) September 30, December 31, millions 2018 2017 Balance Sheet Data Cash and cash equivalents $ 133 $ 80 Net property, plant, and equipment 6,419 5,731 Total assets 9,034 8,016 Long-term debt 4,566 3,493 Total liabilities 5,417 4,071 Total equity and partners’ capital 3,617 3,945 Assets and Liabilities of VIEs The assets of WGP, WES, and their subsidiaries cannot be used by Anadarko for general corporate purposes and are included in and disclosed parenthetically on the Company’s Consolidated Balance Sheets. The carrying amounts of liabilities related to WGP, WES, and their subsidiaries for which the creditors do not have recourse to other assets of the Company are included in and disclosed parenthetically on the Company’s Consolidated Balance Sheets. All outstanding debt for WES at September 30, 2018 , and December 31, 2017 , including any borrowings under the WES RCF, is recourse to WES’s general partner, which in turn has been indemnified in certain circumstances by certain wholly owned subsidiaries of the Company for such liabilities. All outstanding debt for WGP at September 30, 2018 , and December 31, 2017 , including any borrowings under the WGP RCF, is recourse to WGP’s general partner, which is a wholly owned subsidiary of the Company. See Note 10—Debt for additional information on WGP and WES short-term and long-term debt balances. 16. Variable Interest Entities (Continued) VIE Financing WGP’s sources of liquidity include borrowings under its RCF and distributions from WES. WES’s sources of liquidity include cash and cash equivalents, cash flows generated from operations, interest income from a note receivable from Anadarko as discussed below, borrowings under its RCF, the issuance of additional partnership units, and debt offerings. See Note 10—Debt and Note 15—Noncontrolling Interests for additional information on WGP and WES financing activity. Financial Support Provided to VIEs Concurrent with the closing of its May 2008 IPO, WES loaned the Company $260 million in exchange for a 30 -year note bearing interest at a fixed annual rate of 6.50% , payable quarterly. The related interest income for WES was $13 million for the nine months ended September 30, 2018 and 2017 . The note receivable and related interest income are eliminated in consolidation. To reduce WES’s exposure to a majority of the commodity-price risk inherent in certain of its contracts, Anadarko has commodity price swap agreements in place with WES expiring on December 31, 2018 . WES recorded a capital contribution from Anadarko in its Consolidated Statement of Equity and Partners’ Capital for an amount equal to (i) the amount by which the swap price for product sales exceeds the applicable market price, minus (ii) the amount by which the swap price for product purchases exceeds the market price. WES recorded a capital contribution from Anadarko of $41 million for the nine months ended September 30, 2018 , and $47 million for the nine months ended September 30, 2017 .

Supplemental Cash Flow Informat

Supplemental Cash Flow Information	9 Months Ended
	Sep. 30, 2018
Supplemental Cash Flow Information [Abstract]
Supplemental Cash Flow Information	17. Supplemental Cash Flow Information Additions to properties and equipment as presented within Anadarko’s cash flows from investing activities include cash payments for cost of properties, equipment, and facilities. The cost of properties includes the initial capitalization of drilling costs associated with all exploratory wells whether or not they were deemed to have a commercially sufficient quantity of proved reserves. The following summarizes cash paid (received) for interest and income taxes as well as non-cash investing and financing activities: Nine Months Ended September 30, millions 2018 2017 Cash paid (received) Interest, net of amounts capitalized $ 813 $ 764 Income taxes, net of refunds 48 169 Non-cash investing activities Fair value of properties and equipment acquired $ 8 $ 619 Asset retirement cost additions 261 228 Accruals of property, plant, and equipment 886 786 Net liabilities assumed (divested) in acquisitions and divestitures (97 ) (115 ) Non-cash investing and financing activities Deferred drilling lease liability $ — $ 14 Non-cash financing activities Settlement of tangible equity units $ 300 $ — The following table provides a reconciliation of Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents as reported in the Consolidated Statement of Cash Flows to the line items within the Consolidated Balance Sheets: September 30, December 31, millions 2018 2017 Cash and cash equivalents $ 1,883 $ 4,553 Restricted cash and restricted cash equivalents included in Other Assets 110 121 Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents $ 1,993 $ 4,674 Included in cash and cash equivalents is restricted cash and restricted cash equivalents of $134 million at September 30, 2018, and $255 million at December 31, 2017 . Total restricted cash and restricted cash equivalents are primarily associated with certain international joint venture operations, payments of future hard-minerals royalty revenues conveyed, like-kind exchanges of property, and a judicially-controlled account related to a Brazilian tax dispute. See Note 17—Contingencies in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017.

Segment Information

Segment Information	9 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Segment Information	18. Segment Information Anadarko’s business segments are separately managed due to distinct operational differences. Anadarko has three reporting segments: Exploration and Production, WES Midstream, and Other Midstream, which include their respective marketing results. The Company has reclassified prior-period amounts to conform to the current-period presentation. The Exploration and Production reporting segment is engaged in the exploration, development, production, and sale of oil, natural gas, and NGLs and in advancing its Mozambique LNG project toward FID. The WES Midstream and Other Midstream reporting segments engage in gathering, compressing, treating, processing, and transporting of natural gas; gathering, stabilizing, and transporting of oil and NGLs; and gathering and disposing of produced water. The WES Midstream segment consists of WES midstream assets, and the Other Midstream segment consists of the Company’s other midstream assets. To assess the performance of Anadarko’s operating segments, the chief operating decision maker analyzes Adjusted EBITDAX. The Company defines Adjusted EBITDAX as income (loss) before income taxes; interest expense; DD&A; exploration expense; gains (losses) on divestitures, net; impairments; total (gains) losses on derivatives, net, less net cash from settlement of commodity derivatives; restructuring charges; and less net income (loss) attributable to noncontrolling interests. The Company’s definition of Adjusted EBITDAX excludes gains (losses) on divestitures, net and exploration expense as they are not indicators of operating efficiency for a given reporting period. DD&A and impairments are excluded from Adjusted EBITDAX as a measure of segment operating performance because capital expenditures are evaluated at the time capital costs are incurred. Adjusted EBITDAX also excludes interest expense to allow for assessment of segment operating results without regard to Anadarko’s financing methods or capital structure. Total (gains) losses on derivatives, net, less net cash from settlement of commodity derivatives are excluded from Adjusted EBITDAX because these (gains) losses are not considered a measure of asset operating performance. Finally, net income (loss) attributable to noncontrolling interests is excluded from the Company’s measure of Adjusted EBITDAX because it represents earnings that are not attributable to the Company’s common stockholders. Management believes Adjusted EBITDAX provides information useful in assessing the Company’s operating and financial performance across periods. Adjusted EBITDAX as defined by Anadarko may not be comparable to similarly titled measures used by other companies and should be considered in conjunction with net income (loss) attributable to common stockholders and other performance measures, such as operating income. Below is a reconciliation of consolidated Adjusted EBITDAX to income (loss) before income taxes: Three Months Ended Nine Months Ended September 30, September 30, millions 2018 2017 2018 2017 Income (loss) before income taxes $ 683 $ (1,066 ) $ 1,125 $ (1,616 ) Interest expense 240 230 705 682 DD&A 1,130 1,083 3,123 3,235 Exploration expense (1) 118 750 380 2,366 (Gains) losses on divestitures, net (3 ) 194 (31 ) (815 ) Impairments 172 — 319 383 Total (gains) losses on derivatives, net, less net cash from settlement of commodity derivatives (167 ) 98 73 (12 ) Restructuring charges 13 3 13 20 Less net income (loss) attributable to noncontrolling interests 64 58 105 182 Consolidated Adjusted EBITDAX $ 2,122 $ 1,234 $ 5,602 $ 4,061 __________________________________________________________________ (1) Includes restructuring charges of $20 million for the three and nine months ended September 30, 2018 . 18. Segment Information (Continued) Information presented below as “Other and Intersegment Eliminations” includes corporate costs, margin on sales of third-party commodity purchases, deficiency fee expenses, results from hard-minerals royalties, net cash from settlement of commodity derivatives, and net income (loss) attributable to noncontrolling interests. The following summarizes selected financial information for Anadarko’s reporting segments: millions Exploration & Production WES Midstream Other Midstream Other and Intersegment Eliminations Total Three Months Ended September 30, 2018 Sales revenues $ 3,161 $ 394 $ 39 $ 13 $ 3,607 Intersegment revenues 25 114 78 (217 ) — Other 1 52 11 23 87 Total revenues and other (1) 3,187 560 128 (181 ) 3,694 Operating costs and expenses (2) 1,059 245 55 (67 ) 1,292 Net cash from settlement of commodity derivatives — — — 199 199 Other (income) expense, net (3) — — — 17 17 Net income (loss) attributable to noncontrolling interests — — — 64 64 Total expenses and other 1,059 245 55 213 1,572 Total (gains) losses on derivatives, net included in marketing revenue, less net cash from settlement — — — — — Adjusted EBITDAX $ 2,128 $ 315 $ 73 $ (394 ) $ 2,122 Three Months Ended September 30, 2017 Sales revenues $ 2,097 $ 445 $ 53 $ 15 $ 2,610 Intersegment revenues 4 119 43 (166 ) — Other 6 39 7 28 80 Total revenues and other (1) 2,107 603 103 (123 ) 2,690 Operating costs and expenses (2) 956 345 62 49 1,412 Net cash from settlement of commodity derivatives — — — (16 ) (16 ) Other (income) expense, net — — — 2 2 Net income (loss) attributable to noncontrolling interests — — — 58 58 Total expenses and other 956 345 62 93 1,456 Adjusted EBITDAX $ 1,151 $ 258 $ 41 $ (216 ) $ 1,234 __________________________________________________________________ (1) Total revenues and other excludes gains (losses) on divestitures, net since these gains and losses are excluded from Adjusted EBITDAX. (2) Operating costs and expenses excludes exploration expense, DD&A, impairments, restructuring charges, and certain other operating expenses since these expenses are excluded from Adjusted EBITDAX. (3) Other (income) expense, net excludes restructuring charges since these expenses are excluded from Adjusted EBITDAX. 18. Segment Information (Continued) millions Exploration & Production WES Midstream Other Midstream Other and Intersegment Eliminations Total Nine Months Ended September 30, 2018 Sales revenues $ 8,589 $ 1,063 $ 73 $ 76 $ 9,801 Intersegment revenues 49 369 188 (606 ) — Other (5 ) 113 30 63 201 Total revenues and other (1) 8,633 1,545 291 (467 ) 10,002 Operating costs and expenses (2) 2,840 687 134 195 3,856 Net cash from settlement of commodity derivatives — — — 437 437 Other (income) expense, net (3) — — — 9 9 Net income (loss) attributable to noncontrolling interests — — — 105 105 Total expenses and other 2,840 687 134 746 4,407 Total (gains) losses on derivatives, net included in marketing revenue, less net cash from settlement — — — 7 7 Adjusted EBITDAX $ 5,793 $ 858 $ 157 $ (1,206 ) $ 5,602 Nine Months Ended September 30, 2017 Sales revenues $ 6,500 $ 1,213 $ 134 $ 80 $ 7,927 Intersegment revenues 10 387 125 (522 ) — Other 16 124 20 77 237 Total revenues and other (1) 6,526 1,724 279 (365 ) 8,164 Operating costs and expenses (2) 2,679 936 168 135 3,918 Net cash from settlement of commodity derivatives — — — (23 ) (23 ) Other (income) expense, net — — — 24 24 Net income (loss) attributable to noncontrolling interests — — — 182 182 Total expenses and other 2,679 936 168 318 4,101 Total (gains) losses on derivatives, net included in marketing revenue, less net cash from settlement — — — (2 ) (2 ) Adjusted EBITDAX $ 3,847 $ 788 $ 111 $ (685 ) $ 4,061 __________________________________________________________________ (1) Total revenues and other excludes gains (losses) on divestitures, net since these gains and losses are excluded from Adjusted EBITDAX. (2) Operating costs and expenses excludes exploration expense, DD&A, impairments, restructuring charges, and certain other operating expenses since these expenses are excluded from Adjusted EBITDAX. (3) Other (income) expense, net excludes restructuring charges since these expenses are excluded from Adjusted EBITDAX.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2018
Accounting Policies [Abstract]
Consolidation	The consolidated financial statements include the accounts of Anadarko and subsidiaries in which Anadarko holds, directly or indirectly, more than 50% of the voting rights and VIEs for which Anadarko is the primary beneficiary. The Company has determined that WGP and WES are VIEs. Anadarko is considered the primary beneficiary and consolidates WGP and WES. WGP and WES function with capital structures that are separate from Anadarko, consisting of their own debt instruments and publicly traded common units. All intercompany transactions have been eliminated. Undivided interests in oil and natural-gas exploration and production joint ventures are consolidated on a proportionate basis. Investments in noncontrolled entities that Anadarko has the ability to exercise significant influence over operating and financial policies and VIEs for which Anadarko is not the primary beneficiary are accounted for using the equity method. In applying the equity method of accounting, the investments are initially recognized at cost and subsequently adjusted for the Company’s proportionate share of earnings, losses, and distributions. Investments are included in other assets.
Recently Issued Accounting Standards	Recently Adopted Accounting Standards ASU 2017-07, Compensation—Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost , requires presentation of service cost in the same line item(s) as other compensation costs arising from services rendered by employees during the period and presentation of the remaining components of net benefit cost in a separate line item outside operating items. Additionally, only the service cost component of net benefit cost will be eligible for capitalization. The Company adopted this ASU on January 1, 2018, with retrospective presentation of the service cost component and the other components of net benefit cost in the income statement and prospective presentation for the capitalization of the service cost component of net benefit cost in assets. Upon adoption, non-service cost components of net periodic benefit costs of $107 million for 2017, including $94 million for the nine months ended September 30, 2017 , were reclassified to other (income) expense, net, from G&A; oil and gas operating; gathering, processing, and marketing; and exploration expense. ASU 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash , requires an entity to explain the changes in the total of cash, cash equivalents, restricted cash, and restricted cash equivalents on the statement of cash flows and to provide a reconciliation of the totals in that statement to the related captions in the balance sheet when the cash, cash equivalents, restricted cash, and restricted cash equivalents are presented in more than one line item on the balance sheet. The Company adopted this ASU using a retrospective approach on January 1, 2018. Adoption did not have a material impact on the Company’s consolidated financial statements. See Consolidated Statements of Cash Flows and Note 17—Supplemental Cash Flow Information for additional information. 1. Summary of Significant Accounting Policies (Continued) ASU 2014-09, Revenue from Contracts with Customers (Topic 606) , supersedes the revenue recognition requirements and industry-specific guidance under Revenue Recognition ( Topic 605) . Topic 606 requires an entity to recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration the entity expects to be entitled to in exchange for those goods or services. The Company adopted Topic 606 on January 1, 2018, using the modified retrospective method applied to contracts that were not completed as of January 1, 2018. Under the modified retrospective method, prior-period financial positions and results will not be adjusted. The cumulative effect adjustment recognized in the opening balances included a reduction to total equity of $47 million . While the Company does not expect 2018 net earnings to be materially impacted by revenue recognition timing changes, Topic 606 requires certain changes to the presentation of revenues and related expenses beginning January 1, 2018. See Note 2—Revenue from Contracts with Customers for additional information. The Company’s revenue recognition accounting policy effective January 1, 2018, is detailed below. • Exploration and Production —The Company’s oil is sold primarily to marketers, gatherers, and refiners. Natural gas is sold primarily to interstate and intrastate natural-gas pipelines, direct end-users, industrial users, local distribution companies, and natural-gas marketers. NGLs are sold primarily to direct end-users, refiners, and marketers. Payment is generally received from the customer in the month following delivery. Contracts with customers have varying terms, including spot sales or month-to-month contracts, contracts with a finite term, and life-of-field contracts where all production from a well or group of wells is sold to one or more customers. The Company recognizes sales revenues for oil, natural gas, and NGLs based on the amount of each product sold to a customer when control transfers to the customer. Generally, control transfers at the time of delivery to the customer at a pipeline interconnect, the tailgate of a processing facility, or as a tanker lifting is completed. Revenue is measured based on the contract price, which may be index-based or fixed, and may include adjustments for market differentials and downstream costs incurred by the customer, including gathering, transportation, and fuel costs. For natural gas and NGLs sold on our behalf by a processor, revenue is typically measured based on the price the processor receives for the sale, less certain costs withheld by the processor. Revenues are recognized for the sale of Anadarko’s net share of production volumes. Sales on behalf of other working interest owners and royalty interest owners are not recognized as revenues. The Company enters into buy/sell arrangements related to the transportation of a portion of its oil production. Under these arrangements, barrels are sold to a third party at a location-based contract price and subsequently repurchased by the Company at a downstream location. The difference in value between the sale and purchase price represents the transportation fee to move oil from the lease or certain gathering locations to more liquid markets. These arrangements are often required by private transporters. These buy/sell transactions are recorded net in oil and gas transportation expense in the Company’s Consolidated Statements of Income. 1. Summary of Significant Accounting Policies (Continued) • WES Midstream and Other Midstream —Anadarko provides gathering, compressing, treating, processing, stabilizing, transporting, and disposal services pursuant to a variety of contracts. Under these arrangements, the Company receives fees and/or retains a percentage of products or a percentage of the proceeds from the sale of the customer’s products. These revenues are included in gathering, processing, and marketing sales in the Company’s Consolidated Statements of Income. Payment is generally received from the customer in the month of service or the month following the service. Contracts with customers generally have initial terms ranging from 5 to 10 years. Revenue is recognized for fee-based gathering and processing services in the month of service based on the volumes delivered by the customer. Revenues are valued based on the rate in effect for the month of service when the fee is either the same rate per unit over the contract term or when the fee escalates and the escalation factor approximates inflation. The Company may charge additional service fees to customers for a portion of the contract term (i.e., for the first year of a contract or until reaching a volume threshold) due to the significant upfront capital investment. These fees are recognized as revenue over the expected period of customer benefit, generally the life of the related properties. Deficiency fees, which are charged to the customer if they do not meet minimum delivery requirements, are recognized over the performance period based on an estimate of the deficiency fees that will be billed upon completion of the performance period. The Company’s midstream business also purchases natural-gas volumes from producers at the wellhead or production facility, typically at an index price, and charges the producer fees associated with the downstream gathering and processing services. These fees are treated as a reduction of the purchase cost when the fees relate to services performed after control of the product has transferred to Anadarko. Revenue is recognized, along with cost of product expense related to the sale, when the purchased product is sold to a third party. Revenue from percentage of proceeds gathering and processing contracts is recognized net of the cost of product for purchases from service customers when the Company is acting as their agent in the product sale, and any fees charged on these percentage of proceeds contracts are recognized in service revenues. ASU 2018-02, Income Statement - Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income , provides entities the option to reclassify stranded tax effects resulting from the Tax Reform Legislation from accumulated other comprehensive income (AOCI) to retained earnings. In accordance with its accounting policy, the Company releases stranded income tax effects from AOCI in the period the underlying portfolio is liquidated. This ASU allows for the reclassification of stranded tax effects as a result of the change in tax rates from Tax Reform Legislation to be recorded upon adoption of the ASU, rather than at the actual portfolio liquidation date. The Company adopted this ASU on January 1, 2018, electing to reclassify $73 million from AOCI to retained earnings, including a $2 million federal benefit of state tax impact related to the Tax Reform Legislation. New Accounting Standards Issued But Not Yet Adopted ASU 2016-02, Leases (Topic 842), requires lessees to recognize a lease liability and a right-of-use (ROU) asset for all leases, including operating leases, with a term greater than 12 months on the balance sheet. This ASU modifies the definition of a lease and outlines the recognition, measurement, presentation, and disclosure of leasing arrangements by both lessees and lessors. The Company plans to make certain elections allowing the Company not to reassess contracts that commenced prior to adoption, to continue applying its current accounting policy for existing or expired land easements, and not to recognize ROU assets or lease liabilities for short-term leases. Anadarko continues to review contracts in its portfolio of leased assets to assess the impact of adopting this ASU. The Company expects the adoption of this ASU to primarily impact other assets and other long-term liabilities and does not expect a material impact on its consolidated results of operations. To facilitate compliance with this ASU, Anadarko expects to implement new accounting software and complete the evaluation of its systems, processes, and internal controls by the end of 2018. Anadarko will adopt this ASU on January 1, 2019, using a modified retrospective approach. As permitted by ASU 2018-11, Leases (Topic 842): Targeted Improvements , the Company does not expect to adjust comparative-period financial statements and will recognize a cumulative effect adjustment in the opening balance of retained earnings in the period of adoption.

Revenue from Contracts with C_2

Revenue from Contracts with Customers (Tables)	9 Months Ended
	Sep. 30, 2018
Revenue from Contract with Customer [Abstract]
Schedule of Impact of New Accounting Pronouncements	The following tables summarize the impacts of adopting Topic 606 on the Company’s consolidated financial statements: CONSOLIDATED BALANCE SHEET Impact of Change in Accounting Policy millions As Reported Without Adoption of Topic 606 Effect of Change Increase/(Decrease) September 30, 2018 Assets Other current assets $ 397 $ 395 $ 2 Net properties and equipment 28,744 28,697 47 Other assets 2,292 2,282 10 Liabilities Other current liabilities 1,502 1,494 8 Deferred income taxes 2,455 2,461 (6 ) Other 4,043 3,932 111 Equity Total equity 11,237 11,291 (54 ) 2. Revenue from Contracts with Customers (Continued) CONSOLIDATED STATEMENT OF INCOME Impact of Change in Accounting Policy millions As Reported Without Adoption of Topic 606 Effect of Change Increase/(Decrease) Three Months Ended September 30, 2018 Revenues Gathering, processing, and marketing sales $ 421 $ 717 $ (296 ) Gains (losses) on divestitures and other, net 90 89 1 Expenses Gathering, processing, and marketing 256 551 (295 ) Income tax expense (benefit) 256 254 2 Net income (loss) attributable to noncontrolling interests 64 71 (7 ) Net Income (Loss) Attributable to Common Stockholders $ 363 $ 358 $ 5 Nine Months Ended September 30, 2018 Revenues Gathering, processing, and marketing sales $ 1,163 $ 1,944 $ (781 ) Gains (losses) on divestitures and other, net 232 233 (1 ) Expenses Gathering, processing, and marketing 745 1,520 (775 ) Income tax expense (benefit) 507 507 — Net income (loss) attributable to noncontrolling interests 105 111 (6 ) Net Income (Loss) Attributable to Common Stockholders $ 513 $ 514 $ (1 )
Schedule of Disaggregation of Revenue	The following table disaggregates revenue by significant product type and segment: millions Exploration WES Midstream Other Midstream Other and Total Three Months Ended September 30, 2018 Oil sales $ 2,572 $ — $ — $ — $ 2,572 Natural-gas sales 232 — — — 232 Natural-gas liquids sales 382 — — — 382 Gathering, processing, and marketing sales (1) — 511 113 1 625 Other, net 9 — — 31 40 Total Revenue from Customers $ 3,195 $ 511 $ 113 $ 32 $ 3,851 Gathering, processing, and marketing sales (2) — (3 ) 3 (204 ) (204 ) Gains (losses) on divestitures, net 5 — 1 (3 ) 3 Other, net (8 ) 52 12 (9 ) 47 Total Revenue from Other than Customers $ (3 ) $ 49 $ 16 $ (216 ) $ (154 ) Total Revenue and Other $ 3,192 $ 560 $ 129 $ (184 ) $ 3,697 Nine Months Ended September 30, 2018 Oil sales $ 6,964 $ — $ — $ — $ 6,964 Natural-gas sales 682 — — — 682 Natural-gas liquids sales 992 — — — 992 Gathering, processing, and marketing sales (1) — 1,438 255 83 1,776 Other, net 16 — — 71 87 Total Revenue from Customers $ 8,654 $ 1,438 $ 255 $ 154 $ 10,501 Gathering, processing, and marketing sales (2) — (6 ) 6 (613 ) (613 ) Gains (losses) on divestitures, net 24 — 10 (3 ) 31 Other, net (21 ) 113 30 (8 ) 114 Total Revenue from Other than Customers $ 3 $ 107 $ 46 $ (624 ) $ (468 ) Total Revenue and Other $ 8,657 $ 1,545 $ 301 $ (470 ) $ 10,033 __________________________________________________________________ (1) The amount in Other and Intersegment Eliminations primarily represents sales of third-party natural gas and NGLs of $328 million and intercompany eliminations of $(312) million for the three months ended September 30, 2018 , and sales of third-party natural gas and NGLs of $813 million and intercompany eliminations of $(715) million for the nine months ended September 30, 2018 . (2) The amount in Other and Intersegment Eliminations represents purchases of third-party natural gas and NGLs. Although these purchases are reported net in gathering, processing, and marketing sales in the Company’s Consolidated Statements of Income, they are shown separately on this table, as the purchases are not considered revenue from customers.
Schedule of Contract with Customer Liabilities Activity	The following table summarizes the current period activity related to contract liabilities from contracts with customers: millions Balance at December 31, 2017 $ 37 Increase due to cumulative effect of adopting Topic 606 98 Increase due to cash received, excluding revenues recognized in the period (1) 46 Decrease due to revenue recognized (2) (30 ) Balance at September 30, 2018 $ 151 Contract liabilities at September 30, 2018 Other current liabilities $ 23 Other long-term liabilities - other 128 Total contract liabilities from contracts with customers $ 151 __________________________________________________________________ (1) Includes $(6) million for the three months ended September 30, 2018 . (2) Includes $(9) million for the three months ended September 30, 2018 .
Schedule of Expected Revenue Recognition from Satisfaction of Performance Obligations	Therefore, the following table represents only a small portion of Anadarko’s expected future consolidated revenues as future revenue from the sale of most products and services is dependent on future production or variable customer volumes and variable commodity prices for those volumes. millions Exploration WES Midstream Other Midstream Other and Total Remainder of 2018 $ 27 $ 124 $ 31 $ (96 ) $ 86 2019 104 480 204 (441 ) 347 2020 103 545 293 (606 ) 335 2021 103 525 361 (672 ) 317 2022 7 529 417 (739 ) 214 Thereafter 65 2,192 3,107 (4,662 ) 702 Total $ 409 $ 4,395 $ 4,413 $ (7,216 ) $ 2,001

Commodity Inventories (Tables)

Commodity Inventories (Tables)	9 Months Ended
	Sep. 30, 2018
Energy Related Inventory [Abstract]
Inventory Disclosure Table	The following summarizes the major classes of commodity inventories included in other current assets: September 30, December 31, millions 2018 2017 Oil $ 168 $ 165 Natural gas 19 29 NGLs 131 122 Total commodity inventories $ 318 $ 316

Divestitures (Tables)

Divestitures (Tables)	9 Months Ended
	Sep. 30, 2018
Property, Plant and Equipment [Abstract]
Schedule of Proceeds Received and Gains (Losses) Recognized on Divestitures	The following summarizes the proceeds received and gains (losses) recognized on divestitures: Nine Months Ended September 30, millions 2018 2017 Proceeds received, net of closing adjustments $ 393 $ 3,480 Gains (losses) on divestitures, net (1) 31 815 __________________________________________________________________ (1) Includes the $126 million gain related to the 2017 property exchange discussed below.

Current Liabilities (Tables)

Current Liabilities (Tables)	9 Months Ended
	Sep. 30, 2018
Payables and Accruals [Abstract]
Schedule of Other Current Liabilities	The following summarizes the Company’s other current liabilities: September 30, December 31, millions 2018 2017 Accrued income taxes $ 79 $ 71 Interest payable 169 246 Production, property, and other taxes payable 344 216 Accrued employee benefits 270 210 Derivatives 491 384 Other 149 183 Total other current liabilities $ 1,502 $ 1,310

Derivative Instruments (Tables)

Derivative Instruments (Tables)	9 Months Ended
	Sep. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Derivative Instruments	The following is a summary of the Company’s derivative instruments related to oil and natural-gas production/processing derivative activities at September 30, 2018 : 2018 Settlement 2019 Settlement Oil Two-Way Collars (MBbls/d) 108 — Average price per barrel (WTI) Ceiling sold price (call) $ 60.48 $ — Floor purchased price (put) $ 50.00 $ — Three-Way Collars (MBbls/d) — 87 Average price per barrel (WTI and Brent) Ceiling sold price (call) $ — $ 72.98 Floor purchased price (put) $ — $ 56.72 Floor sold price (put) $ — $ 46.72 Fixed-Price Contracts (MBbls/d) 84 — Average price per barrel (Brent) $ 61.45 $ — Natural Gas Three-Way Collars (thousand MMBtu/d) 250 — Average price per MMBtu (Henry Hub) Ceiling sold price (call) $ 3.54 $ — Floor purchased price (put) $ 2.75 $ — Floor sold price (put) $ 2.00 $ — Fixed-Price Contracts (thousand MMBtu/d) 280 — Average price per MMBtu (Henry Hub) $ 3.02 $ — The Company had the following outstanding interest-rate swaps at September 30, 2018 : millions except percentages Mandatory Weighted-Average Notional Principal Amount Reference Period Termination Date Interest Rate $ 550 September 2016 - 2046 September 2020 6.418% $ 250 September 2016 - 2046 September 2022 6.809% $ 100 September 2017 - 2047 September 2020 6.891% $ 250 September 2017 - 2047 September 2021 6.570% $ 450 September 2017 - 2047 September 2023 6.445%
Schedule of Other Derivatives Not Designated as Hedging Instruments, Statements of Financial Performance and Financial Position, Location	The following summarizes the fair value of the Company’s derivative instruments: Gross Derivative Assets Gross Derivative Liabilities millions September 30, December 31, September 30, December 31, Balance Sheet Classification 2018 2017 2018 2017 Commodity derivatives Other current assets $ 2 $ 7 $ — $ (1 ) Other assets — 2 — — Other current liabilities 20 45 (440 ) (206 ) Other liabilities 15 — (56 ) (2 ) 37 54 (496 ) (209 ) Interest-rate derivatives Other current assets 21 14 — — Other assets 54 40 — — Other current liabilities — — (80 ) (236 ) Other liabilities — — (1,028 ) (1,183 ) 75 54 (1,108 ) (1,419 ) Total derivatives $ 112 $ 108 $ (1,604 ) $ (1,628 ) The following summarizes gains and losses related to derivative instruments: millions Three Months Ended September 30, Nine Months Ended September 30, Classification of (Gain) Loss Recognized 2018 2017 2018 2017 Commodity derivatives Gathering, processing, and marketing sales $ 1 $ — $ 3 $ — (Gains) losses on derivatives, net 104 43 734 (164 ) Interest-rate derivatives (Gains) losses on derivatives, net (72 ) 39 (231 ) 131 Total (gains) losses on derivatives, net $ 33 $ 82 $ 506 $ (33 ) ________________________________
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis	The following summarizes the fair value of the Company’s derivative assets and liabilities by input level within the fair-value hierarchy: millions Level 1 Level 2 Level 3 Netting (1) Collateral Total September 30, 2018 Assets Commodity derivatives $ — $ 37 $ — $ (35 ) $ — $ 2 Interest-rate derivatives — 75 — — — 75 Total derivative assets $ — $ 112 $ — $ (35 ) $ — $ 77 Liabilities Commodity derivatives $ — $ (496 ) $ — $ 35 $ 6 $ (455 ) Interest-rate derivatives — (1,108 ) — — 49 (1,059 ) Total derivative liabilities $ — $ (1,604 ) $ — $ 35 $ 55 $ (1,514 ) December 31, 2017 Assets Commodity derivatives $ 1 $ 53 $ — $ (46 ) $ (1 ) $ 7 Interest-rate derivatives — 54 — — — 54 Total derivative assets $ 1 $ 107 $ — $ (46 ) $ (1 ) $ 61 Liabilities Commodity derivatives $ (1 ) $ (208 ) $ — $ 46 $ 3 $ (160 ) Interest-rate derivatives — (1,419 ) — — 170 (1,249 ) Total derivative liabilities $ (1 ) $ (1,627 ) $ — $ 46 $ 173 $ (1,409 ) __________________________________________________________________ (1) Represents the impact of netting commodity derivative assets and liabilities with counterparties where the Company has the contractual right and intends to net settle.

Debt (Tables)

Debt (Tables)	9 Months Ended
	Sep. 30, 2018
Debt Disclosure [Abstract]
Schedule or Debt Outstanding	The following summarizes the Company’s borrowing activity, after eliminating the effect of intercompany transactions, during the nine months ended September 30, 2018 : Carrying Value millions WES WGP (1) Anadarko (2) Anadarko Consolidated Description Balance at December 31, 2017 $ 3,465 $ 28 $ 11,965 $ 15,458 Issuances 394 — — 394 WES 4.500% Senior Notes due 2028 687 — — 687 WES 5.300% Senior Notes due 2048 396 — — 396 WES 4.750% Senior Notes due 2028 342 — — 342 WES 5.500% Senior Notes due 2048 Borrowings 320 — — 320 WES RCF Repayments (690 ) — — (690 ) WES RCF — — (114 ) (114 ) 7.050% Debentures due 2018 (350 ) — — (350 ) WES 2.600% Senior Notes due 2018 — — (17 ) (17 ) TEUs - senior amortizing notes Other, net 2 — 39 41 Amortization of discounts, premiums, and debt issuance costs Balance at September 30, 2018 $ 4,566 $ 28 $ 11,873 $ 16,467 __________________________________________________________________ (1) Excludes WES. (2) Excludes WES and WGP. 10. Debt (Continued) Debt The following summarizes the Company’s outstanding debt, including capital lease obligations, after eliminating the effect of intercompany transactions: millions WES WGP (1) Anadarko (2) Consolidated September 30, 2018 Total borrowings at face value $ 4,620 $ 28 $ 13,383 $ 18,031 Net unamortized discounts, premiums, and debt issuance costs (3) (54 ) — (1,510 ) (1,564 ) Total borrowings (4) 4,566 28 11,873 16,467 Capital lease obligations — — 226 226 Less short-term debt — 28 910 938 Total long-term debt $ 4,566 $ — $ 11,189 $ 15,755 December 31, 2017 Total borrowings at face value $ 3,490 $ 28 $ 13,514 $ 17,032 Net unamortized discounts, premiums, and debt issuance costs (3) (25 ) — (1,549 ) (1,574 ) Total borrowings (4) 3,465 28 11,965 15,458 Capital lease obligations — — 231 231 Less short-term debt — — 142 142 Total long-term debt $ 3,465 $ 28 $ 12,054 $ 15,547 __________________________________________________________________ (1) Excludes WES. (2) Excludes WES and WGP. (3) Unamortized discounts, premiums, and debt issuance costs are amortized over the term of the related debt. Debt issuance costs related to RCFs are included in other current assets and other assets on the Company’s Consolidated Balance Sheets. (4) The Company’s outstanding borrowings, except for borrowings under the WGP RCF, are senior unsecured.

Income Taxes (Tables)

Income Taxes (Tables)	9 Months Ended
	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Schedule of Income Taxes and Effective Tax Rate	The following summarizes income tax expense (benefit) and effective tax rates: Three Months Ended Nine Months Ended September 30, September 30, millions except percentages 2018 2017 2018 2017 Current income tax expense (benefit) $ 146 $ 430 $ 383 $ 670 Deferred income tax expense (benefit) 110 (855 ) 124 (1,036 ) Total income tax expense (benefit) $ 256 $ (425 ) $ 507 $ (366 ) Income (loss) before income taxes 683 (1,066 ) 1,125 (1,616 ) Effective tax rate 37 % 40 % 45 % 23 %

Pension Plans and Other Postr_2

Pension Plans and Other Postretirement Benefits (Tables)	9 Months Ended
	Sep. 30, 2018
Retirement Benefits [Abstract]
Components of Net Periodic Benefit Cost Table	The following summarizes the Company’s pension and other postretirement benefit cost: Pension Benefits Other Benefits millions 2018 2017 2018 2017 Three Months Ended September 30 Service cost $ 23 $ 22 $ — $ — Interest cost 19 21 3 3 Expected (return) loss on plan assets (20 ) (21 ) — — Amortization of net actuarial loss (gain) 6 7 — — Amortization of net prior service cost (credit) — (1 ) (6 ) (6 ) Settlement expense 9 22 — — Termination benefits expense 7 — — — Net periodic benefit cost (1) $ 44 $ 50 $ (3 ) $ (3 ) Nine Months Ended September 30 Service cost $ 68 $ 64 $ 1 $ 1 Interest cost 57 63 8 9 Expected (return) loss on plan assets (61 ) (63 ) — — Amortization of net actuarial loss (gain) 19 20 — — Amortization of net prior service cost (credit) — (1 ) (18 ) (18 ) Settlement expense 9 80 — — Termination benefits expense 7 4 — — Net periodic benefit cost (1) $ 99 $ 167 $ (9 ) $ (8 ) __________________________________________________________________ (1) The service cost component of net periodic benefit cost is included in G&A; oil and gas operating expense; gathering, processing, and marketing expense; and exploration expense, and all other components of net periodic benefit cost are included in other (income) expense on the Company’s Consolidated Statements of Income.

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	9 Months Ended
	Sep. 30, 2018
Stockholders' Equity Note [Abstract]
Earnings Per Share Table	The following provides a reconciliation between basic and diluted EPS attributable to common stockholders: Three Months Ended Nine Months Ended September 30, September 30, millions except per-share amounts 2018 2017 2018 2017 Net income (loss) Net income (loss) attributable to common stockholders $ 363 $ (699 ) $ 513 $ (1,432 ) Income (loss) effect of TEUs — (2 ) (4 ) (6 ) Less distributions on participating securities 2 — 4 — Less undistributed income allocated to participating securities 2 — 1 — Basic $ 359 $ (701 ) $ 504 $ (1,438 ) Income (loss) effect of TEUs — — — (1 ) Diluted $ 359 $ (701 ) $ 504 $ (1,439 ) Shares Average number of common shares outstanding—basic 499 553 507 552 Dilutive effect of stock options 1 — 1 — Average number of common shares outstanding—diluted 500 553 508 552 Excluded due to anti-dilutive effect 8 11 9 11 Net income (loss) per common share Basic $ 0.72 $ (1.27 ) $ 0.99 $ (2.60 ) Diluted $ 0.72 $ (1.27 ) $ 0.99 $ (2.61 )
Schedule of Accelerated Share Repurchases	During the nine months ended September 30, 2018 , the Company entered into and completed two ASR Agreements and open-market repurchases as presented below: millions except per-share amounts Agreement Date Settlement Date Amount Average Price per Share Initial Shares Delivered Additional Shares Delivered Total Shares Delivered ASR Agreements January 2018 February 2018 $ 500 $ 58.82 7.0 1.5 8.5 March 2018 June 2018 1,441 65.28 19.1 3.0 22.1 Total ASR Agreements 1,941 26.1 4.5 30.6 Open-market repurchases August 2018 August 2018 250 66.14 N/A N/A 3.8 September 2018 September 2018 250 63.11 N/A N/A 3.9 Total open-market repurchases 500 7.7 Total $ 2,441 38.3

Variable Interest Entities (Tab

Variable Interest Entities (Tables)	9 Months Ended
	Sep. 30, 2018
Variable Interest Entities [Abstract]
Schedule of Financial Data of VIE	The following tables present selected financial data from the consolidated financial statements of WGP: Three Months Ended Nine Months Ended September 30, September 30, millions 2018 2017 2018 2017 Statement of Operations Data Total revenues and other $ 508 $ 575 $ 1,432 $ 1,616 Operating income (loss) 200 179 461 523 Net income (loss) 155 147 340 424 Nine Months Ended September 30, millions 2018 2017 Statement of Cash Flows Data Net cash provided by (used in) operating activities $ 749 $ 642 Net cash provided by (used in) investing activities (1,161 ) (515 ) Net cash provided by (used in) financing activities 465 (334 ) September 30, December 31, millions 2018 2017 Balance Sheet Data Cash and cash equivalents $ 133 $ 80 Net property, plant, and equipment 6,419 5,731 Total assets 9,034 8,016 Long-term debt 4,566 3,493 Total liabilities 5,417 4,071 Total equity and partners’ capital 3,617 3,945

Supplemental Cash Flow Inform_2

Supplemental Cash Flow Information (Tables)	9 Months Ended
	Sep. 30, 2018
Supplemental Cash Flow Information [Abstract]
Supplemental Cash Flow Table	The following summarizes cash paid (received) for interest and income taxes as well as non-cash investing and financing activities: Nine Months Ended September 30, millions 2018 2017 Cash paid (received) Interest, net of amounts capitalized $ 813 $ 764 Income taxes, net of refunds 48 169 Non-cash investing activities Fair value of properties and equipment acquired $ 8 $ 619 Asset retirement cost additions 261 228 Accruals of property, plant, and equipment 886 786 Net liabilities assumed (divested) in acquisitions and divestitures (97 ) (115 ) Non-cash investing and financing activities Deferred drilling lease liability $ — $ 14 Non-cash financing activities Settlement of tangible equity units $ 300 $ —
Schedule of Cash and Cash Equivalents Balance Sheet Locations	The following table provides a reconciliation of Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents as reported in the Consolidated Statement of Cash Flows to the line items within the Consolidated Balance Sheets: September 30, December 31, millions 2018 2017 Cash and cash equivalents $ 1,883 $ 4,553 Restricted cash and restricted cash equivalents included in Other Assets 110 121 Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents $ 1,993 $ 4,674

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Reconciliation of Consolidated Adjusted EBITDAX to Income (Loss) Before Income Taxes	Below is a reconciliation of consolidated Adjusted EBITDAX to income (loss) before income taxes: Three Months Ended Nine Months Ended September 30, September 30, millions 2018 2017 2018 2017 Income (loss) before income taxes $ 683 $ (1,066 ) $ 1,125 $ (1,616 ) Interest expense 240 230 705 682 DD&A 1,130 1,083 3,123 3,235 Exploration expense (1) 118 750 380 2,366 (Gains) losses on divestitures, net (3 ) 194 (31 ) (815 ) Impairments 172 — 319 383 Total (gains) losses on derivatives, net, less net cash from settlement of commodity derivatives (167 ) 98 73 (12 ) Restructuring charges 13 3 13 20 Less net income (loss) attributable to noncontrolling interests 64 58 105 182 Consolidated Adjusted EBITDAX $ 2,122 $ 1,234 $ 5,602 $ 4,061 __________________________________________________________________ (1) Includes restructuring charges of $20 million for the three and nine months ended September 30, 2018 .
Schedule of Segment Reporting Information, by Segment	The following summarizes selected financial information for Anadarko’s reporting segments: millions Exploration & Production WES Midstream Other Midstream Other and Intersegment Eliminations Total Three Months Ended September 30, 2018 Sales revenues $ 3,161 $ 394 $ 39 $ 13 $ 3,607 Intersegment revenues 25 114 78 (217 ) — Other 1 52 11 23 87 Total revenues and other (1) 3,187 560 128 (181 ) 3,694 Operating costs and expenses (2) 1,059 245 55 (67 ) 1,292 Net cash from settlement of commodity derivatives — — — 199 199 Other (income) expense, net (3) — — — 17 17 Net income (loss) attributable to noncontrolling interests — — — 64 64 Total expenses and other 1,059 245 55 213 1,572 Total (gains) losses on derivatives, net included in marketing revenue, less net cash from settlement — — — — — Adjusted EBITDAX $ 2,128 $ 315 $ 73 $ (394 ) $ 2,122 Three Months Ended September 30, 2017 Sales revenues $ 2,097 $ 445 $ 53 $ 15 $ 2,610 Intersegment revenues 4 119 43 (166 ) — Other 6 39 7 28 80 Total revenues and other (1) 2,107 603 103 (123 ) 2,690 Operating costs and expenses (2) 956 345 62 49 1,412 Net cash from settlement of commodity derivatives — — — (16 ) (16 ) Other (income) expense, net — — — 2 2 Net income (loss) attributable to noncontrolling interests — — — 58 58 Total expenses and other 956 345 62 93 1,456 Adjusted EBITDAX $ 1,151 $ 258 $ 41 $ (216 ) $ 1,234 __________________________________________________________________ (1) Total revenues and other excludes gains (losses) on divestitures, net since these gains and losses are excluded from Adjusted EBITDAX. (2) Operating costs and expenses excludes exploration expense, DD&A, impairments, restructuring charges, and certain other operating expenses since these expenses are excluded from Adjusted EBITDAX. (3) Other (income) expense, net excludes restructuring charges since these expenses are excluded from Adjusted EBITDAX. 18. Segment Information (Continued) millions Exploration & Production WES Midstream Other Midstream Other and Intersegment Eliminations Total Nine Months Ended September 30, 2018 Sales revenues $ 8,589 $ 1,063 $ 73 $ 76 $ 9,801 Intersegment revenues 49 369 188 (606 ) — Other (5 ) 113 30 63 201 Total revenues and other (1) 8,633 1,545 291 (467 ) 10,002 Operating costs and expenses (2) 2,840 687 134 195 3,856 Net cash from settlement of commodity derivatives — — — 437 437 Other (income) expense, net (3) — — — 9 9 Net income (loss) attributable to noncontrolling interests — — — 105 105 Total expenses and other 2,840 687 134 746 4,407 Total (gains) losses on derivatives, net included in marketing revenue, less net cash from settlement — — — 7 7 Adjusted EBITDAX $ 5,793 $ 858 $ 157 $ (1,206 ) $ 5,602 Nine Months Ended September 30, 2017 Sales revenues $ 6,500 $ 1,213 $ 134 $ 80 $ 7,927 Intersegment revenues 10 387 125 (522 ) — Other 16 124 20 77 237 Total revenues and other (1) 6,526 1,724 279 (365 ) 8,164 Operating costs and expenses (2) 2,679 936 168 135 3,918 Net cash from settlement of commodity derivatives — — — (23 ) (23 ) Other (income) expense, net — — — 24 24 Net income (loss) attributable to noncontrolling interests — — — 182 182 Total expenses and other 2,679 936 168 318 4,101 Total (gains) losses on derivatives, net included in marketing revenue, less net cash from settlement — — — (2 ) (2 ) Adjusted EBITDAX $ 3,847 $ 788 $ 111 $ (685 ) $ 4,061 __________________________________________________________________ (1) Total revenues and other excludes gains (losses) on divestitures, net since these gains and losses are excluded from Adjusted EBITDAX. (2) Operating costs and expenses excludes exploration expense, DD&A, impairments, restructuring charges, and certain other operating expenses since these expenses are excluded from Adjusted EBITDAX. (3) Other (income) expense, net excludes restructuring charges since these expenses are excluded from Adjusted EBITDAX.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Detail) - USD ($) $ in Millions		Jan. 01, 2018	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of accounting change	[1]		$ (47)
Accounting Standards Update 2014-09 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of accounting change		$ 47
Accounting Standards Update 2018-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification from AOCI to retained earnings		73
Accounting Standards Update 2018-02 [Member] | State tax impacts [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification from AOCI to retained earnings		$ 2
Costs and expenses [Member] | Accounting Standards Update 2017-07 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Non-service cost component of net periodic benefit cost				$ (94)	$ (107)
WES Midstream and Other Midstream [Member] | Maximum [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Contract terms			Payment is generally received from the customer in the month of service or the month following the service. Contracts with customers generally have initial terms ranging from 5 to 10 years.
[1]	Beginning January 1, 2018, the Company adopted ASU 2014-09, Revenue from Contracts with Customers (Topic 606), and ASU 2018-02, Income Statement - Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income. See Note 1—Summary of Significant Accounting Policies in the Notes to Consolidated Financial Statements for further information.

Revenue from Contracts with C_3

Revenue from Contracts with Customers - Impact on Financial Statements (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Revenues
Revenues from Customers	$ 3,851		$ 10,501
Gains (losses) on divestitures and other, net	90	$ (114)	232	$ 1,052
Expenses
Income tax expense (benefit)	256	(425)	507	(366)
Net income (loss) attributable to noncontrolling interests	64	58	105	182
Net income (loss) attributable to common stockholders	363	(699)	513	(1,432)
Assets
Other current assets	397		397		$ 380
Net properties and equipment	28,744		28,744		27,451
Other Assets	2,292		2,292		2,211
Liabilities
Other current liabilities	1,502		1,502		1,310
Deferred income taxes	2,455		2,455		2,234
Other	4,043		4,043		4,109
Equity
Total equity	11,237		11,237		$ 13,790
Accounting Standards Update 2014-09 [Member] | Without Adoption of Topic 606 [Member]
Revenues
Gains (losses) on divestitures and other, net	89		233
Expenses
Income tax expense (benefit)	254		507
Net income (loss) attributable to noncontrolling interests	71		111
Net income (loss) attributable to common stockholders	358		514
Assets
Other current assets	395		395
Net properties and equipment	28,697		28,697
Other Assets	2,282		2,282
Liabilities
Other current liabilities	1,494		1,494
Deferred income taxes	2,461		2,461
Other	3,932		3,932
Equity
Total equity	11,291		11,291
Accounting Standards Update 2014-09 [Member] | Effect of Change Increase/ (Decrease) [Member]
Revenues
Gains (losses) on divestitures and other, net	1		(1)
Expenses
Income tax expense (benefit)	2		0
Net income (loss) attributable to noncontrolling interests	(7)		(6)
Net income (loss) attributable to common stockholders	5		(1)
Assets
Other current assets	2		2
Net properties and equipment	47		47
Other Assets	10		10
Liabilities
Other current liabilities	8		8
Deferred income taxes	(6)		(6)
Other	111		111
Equity
Total equity	(54)		(54)
Gathering, processing, and marketing [Member]
Revenues
Revenues from Customers	421	509	1,163	1,417
Expenses
Gathering, processing, and marketing	256	$ 396	745	$ 1,101
Gathering, processing, and marketing [Member] | Accounting Standards Update 2014-09 [Member] | Without Adoption of Topic 606 [Member]
Revenues
Revenues from Customers	717		1,944
Expenses
Gathering, processing, and marketing	551		1,520
Gathering, processing, and marketing [Member] | Accounting Standards Update 2014-09 [Member] | Effect of Change Increase/ (Decrease) [Member]
Revenues
Revenues from Customers	(296)		(781)
Expenses
Gathering, processing, and marketing	$ (295)		$ (775)

Revenue from Contracts with C_4

Revenue from Contracts with Customers - Disaggregation of Revenue (Detail) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Revenues from Customers		$ 3,851		$ 10,501
Revenue from Other than Customers		(154)		(468)
Total		3,697	$ 2,496	10,033	$ 8,979
Oil sales [Member]
Disaggregation of Revenue [Line Items]
Revenues from Customers		2,572		6,964
Natural gas sales [Member]
Disaggregation of Revenue [Line Items]
Revenues from Customers		232	269	682	1,090
Natural-gas liquids sales [Member]
Disaggregation of Revenue [Line Items]
Revenues from Customers		382	$ 265	992	$ 768
Gathering, processing, and marketing sales [Member]
Disaggregation of Revenue [Line Items]
Revenues from Customers	[1]	625		1,776
Revenue from Other than Customers	[2]	(204)		(613)
Gains (losses) on divestitures, net [Member]
Disaggregation of Revenue [Line Items]
Revenue from Other than Customers		3		31
Other, net [Member]
Disaggregation of Revenue [Line Items]
Revenues from Customers		40		87
Revenue from Other than Customers		47		114
Operating Segments [Member] | Exploration and Production [Member]
Disaggregation of Revenue [Line Items]
Revenues from Customers		3,195		8,654
Revenue from Other than Customers		(3)		3
Total		3,192		8,657
Operating Segments [Member] | Exploration and Production [Member] | Oil sales [Member]
Disaggregation of Revenue [Line Items]
Revenues from Customers		2,572		6,964
Operating Segments [Member] | Exploration and Production [Member] | Natural gas sales [Member]
Disaggregation of Revenue [Line Items]
Revenues from Customers		232		682
Operating Segments [Member] | Exploration and Production [Member] | Natural-gas liquids sales [Member]
Disaggregation of Revenue [Line Items]
Revenues from Customers		382		992
Operating Segments [Member] | Exploration and Production [Member] | Gathering, processing, and marketing sales [Member]
Disaggregation of Revenue [Line Items]
Revenues from Customers	[1]	0		0
Revenue from Other than Customers	[2]	0		0
Operating Segments [Member] | Exploration and Production [Member] | Gains (losses) on divestitures, net [Member]
Disaggregation of Revenue [Line Items]
Revenue from Other than Customers		5		24
Operating Segments [Member] | Exploration and Production [Member] | Other, net [Member]
Disaggregation of Revenue [Line Items]
Revenues from Customers		9		16
Revenue from Other than Customers		(8)		(21)
Operating Segments [Member] | WES Midstream [Member]
Disaggregation of Revenue [Line Items]
Revenues from Customers		511		1,438
Revenue from Other than Customers		49		107
Total		560		1,545
Operating Segments [Member] | WES Midstream [Member] | Oil sales [Member]
Disaggregation of Revenue [Line Items]
Revenues from Customers		0		0
Operating Segments [Member] | WES Midstream [Member] | Natural gas sales [Member]
Disaggregation of Revenue [Line Items]
Revenues from Customers		0		0
Operating Segments [Member] | WES Midstream [Member] | Natural-gas liquids sales [Member]
Disaggregation of Revenue [Line Items]
Revenues from Customers		0		0
Operating Segments [Member] | WES Midstream [Member] | Gathering, processing, and marketing sales [Member]
Disaggregation of Revenue [Line Items]
Revenues from Customers	[1]	511		1,438
Revenue from Other than Customers	[2]	(3)		(6)
Operating Segments [Member] | WES Midstream [Member] | Gains (losses) on divestitures, net [Member]
Disaggregation of Revenue [Line Items]
Revenue from Other than Customers		0		0
Operating Segments [Member] | WES Midstream [Member] | Other, net [Member]
Disaggregation of Revenue [Line Items]
Revenues from Customers		0		0
Revenue from Other than Customers		52		113
Operating Segments [Member] | Other Midstream [Member]
Disaggregation of Revenue [Line Items]
Revenues from Customers		113		255
Revenue from Other than Customers		16		46
Total		129		301
Operating Segments [Member] | Other Midstream [Member] | Oil sales [Member]
Disaggregation of Revenue [Line Items]
Revenues from Customers		0		0
Operating Segments [Member] | Other Midstream [Member] | Natural gas sales [Member]
Disaggregation of Revenue [Line Items]
Revenues from Customers		0		0
Operating Segments [Member] | Other Midstream [Member] | Natural-gas liquids sales [Member]
Disaggregation of Revenue [Line Items]
Revenues from Customers		0		0
Operating Segments [Member] | Other Midstream [Member] | Gathering, processing, and marketing sales [Member]
Disaggregation of Revenue [Line Items]
Revenues from Customers	[1]	113		255
Revenue from Other than Customers	[2]	3		6
Operating Segments [Member] | Other Midstream [Member] | Gains (losses) on divestitures, net [Member]
Disaggregation of Revenue [Line Items]
Revenue from Other than Customers		1		10
Operating Segments [Member] | Other Midstream [Member] | Other, net [Member]
Disaggregation of Revenue [Line Items]
Revenues from Customers		0		0
Revenue from Other than Customers		12		30
Other and Intersegment Eliminations [Member]
Disaggregation of Revenue [Line Items]
Revenues from Customers		32		154
Revenue from Other than Customers		(216)		(624)
Total		(184)		(470)
Other and Intersegment Eliminations [Member] | Oil sales [Member]
Disaggregation of Revenue [Line Items]
Revenues from Customers		0		0
Other and Intersegment Eliminations [Member] | Natural gas sales [Member]
Disaggregation of Revenue [Line Items]
Revenues from Customers		0		0
Other and Intersegment Eliminations [Member] | Natural-gas liquids sales [Member]
Disaggregation of Revenue [Line Items]
Revenues from Customers		0		0
Other and Intersegment Eliminations [Member] | Gathering, processing, and marketing sales [Member]
Disaggregation of Revenue [Line Items]
Revenues from Customers	[1]	1		83
Revenue from Other than Customers	[2]	(204)		(613)
Intercompany eliminations		(312)		(715)
Third-party marketing revenue		328		813
Other and Intersegment Eliminations [Member] | Gains (losses) on divestitures, net [Member]
Disaggregation of Revenue [Line Items]
Revenue from Other than Customers		(3)		(3)
Other and Intersegment Eliminations [Member] | Other, net [Member]
Disaggregation of Revenue [Line Items]
Revenues from Customers		31		71
Revenue from Other than Customers		$ (9)		$ (8)
[1]	The amount in Other and Intersegment Eliminations primarily represents sales of third-party natural gas and NGLs of $328 million and intercompany eliminations of $(312) million for the three months ended September 30, 2018, and sales of third-party natural gas and NGLs of $813 million and intercompany eliminations of $(715) million for the nine months ended September 30, 2018.
[2]	The amount in Other and Intersegment Eliminations represents purchases of third-party natural gas and NGLs. Although these purchases are reported net in gathering, processing, and marketing sales in the Company’s Consolidated Statements of Income, they are shown separately on this table, as the purchases are not considered revenue from customers.

Revenue from Contracts with C_5

Revenue from Contracts with Customers - Contract Liabilities (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2018	Sep. 30, 2018
Change in Contract with Customer, Liability [Roll Forward]
Balance at December 31, 2017		$ 37
Increase due to cumulative effect of adopting Topic 606		98
Increase due to cash received, excluding revenues recognized in the period (1)	$ (6)	46
Decrease due to revenue recognized (2)	9	(30)
Balance at September 30, 2018	151	151
Contract liabilities at September 30, 2018
Other current liabilities			$ 23
Other long-term liabilities - other			128
Total contract liabilities from contracts with customers	$ 151	$ 37	$ 151

Revenue from Contracts with C_6

Revenue from Contracts with Customers - Revenue Recognition Expected (Detail) $ in Millions	Sep. 30, 2018USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected to be satisfied	$ 86
Performance obligation expected to be satisfied, expected timing	3 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected to be satisfied	$ 347
Performance obligation expected to be satisfied, expected timing	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected to be satisfied	$ 335
Performance obligation expected to be satisfied, expected timing	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected to be satisfied	$ 317
Performance obligation expected to be satisfied, expected timing	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected to be satisfied	$ 214
Performance obligation expected to be satisfied, expected timing	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected to be satisfied	$ 702
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected to be satisfied	2,001
Operating Segments [Member] | Exploration and Production [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected to be satisfied	$ 27
Performance obligation expected to be satisfied, expected timing	3 months
Operating Segments [Member] | Exploration and Production [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected to be satisfied	$ 104
Performance obligation expected to be satisfied, expected timing	1 year
Operating Segments [Member] | Exploration and Production [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected to be satisfied	$ 103
Performance obligation expected to be satisfied, expected timing	1 year
Operating Segments [Member] | Exploration and Production [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected to be satisfied	$ 103
Performance obligation expected to be satisfied, expected timing	1 year
Operating Segments [Member] | Exploration and Production [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected to be satisfied	$ 7
Performance obligation expected to be satisfied, expected timing	1 year
Operating Segments [Member] | Exploration and Production [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected to be satisfied	$ 65
Operating Segments [Member] | Exploration and Production [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected to be satisfied	409
Operating Segments [Member] | WES Midstream [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected to be satisfied	$ 124
Performance obligation expected to be satisfied, expected timing	3 months
Operating Segments [Member] | WES Midstream [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected to be satisfied	$ 480
Performance obligation expected to be satisfied, expected timing	1 year
Operating Segments [Member] | WES Midstream [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected to be satisfied	$ 545
Performance obligation expected to be satisfied, expected timing	1 year
Operating Segments [Member] | WES Midstream [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected to be satisfied	$ 525
Performance obligation expected to be satisfied, expected timing	1 year
Operating Segments [Member] | WES Midstream [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected to be satisfied	$ 529
Performance obligation expected to be satisfied, expected timing	1 year
Operating Segments [Member] | WES Midstream [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected to be satisfied	$ 2,192
Operating Segments [Member] | WES Midstream [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected to be satisfied	4,395
Operating Segments [Member] | Other Midstream [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected to be satisfied	$ 31
Performance obligation expected to be satisfied, expected timing	3 months
Operating Segments [Member] | Other Midstream [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected to be satisfied	$ 204
Performance obligation expected to be satisfied, expected timing	1 year
Operating Segments [Member] | Other Midstream [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected to be satisfied	$ 293
Performance obligation expected to be satisfied, expected timing	1 year
Operating Segments [Member] | Other Midstream [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected to be satisfied	$ 361
Performance obligation expected to be satisfied, expected timing	1 year
Operating Segments [Member] | Other Midstream [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected to be satisfied	$ 417
Performance obligation expected to be satisfied, expected timing	1 year
Operating Segments [Member] | Other Midstream [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected to be satisfied	$ 3,107
Operating Segments [Member] | Other Midstream [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected to be satisfied	4,413
Other and Intersegment Eliminations [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected to be satisfied	$ (96)
Performance obligation expected to be satisfied, expected timing	3 months
Other and Intersegment Eliminations [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected to be satisfied	$ (441)
Performance obligation expected to be satisfied, expected timing	1 year
Other and Intersegment Eliminations [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected to be satisfied	$ (606)
Performance obligation expected to be satisfied, expected timing	1 year
Other and Intersegment Eliminations [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected to be satisfied	$ (672)
Performance obligation expected to be satisfied, expected timing	1 year
Other and Intersegment Eliminations [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected to be satisfied	$ (739)
Performance obligation expected to be satisfied, expected timing	1 year
Other and Intersegment Eliminations [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected to be satisfied	$ (4,662)
Other and Intersegment Eliminations [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: (nil)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Performance obligation expected to be satisfied	$ (7,216)

Commodity Inventories (Detail)

Commodity Inventories (Detail) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Energy Related Inventory [Abstract]
Oil	$ 168	$ 165
Natural gas	19	29
NGLs	131	122
Total commodity inventories	$ 318	$ 316

Divestitures - Divestitures (De

Divestitures - Divestitures (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2018	Sep. 30, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net proceeds from divestitures			$ 393	$ 3,480
Gain (loss) on divestitures			31	815	[1]
Exploration and Production [Member] | Certain Onshore Domestic Assets Ram Powell [Member] | Asset Disposed of by Sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain (loss) on divestitures			67
Exploration and Production [Member] | Certain U.S. Onshore Assets in Eagleford, South Texas [Member] | Asset Disposed of by Sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net proceeds from divestitures				2,100
Gain (loss) on divestitures				730
Exploration and Production [Member] | Certain Onshore Domestic Assets, Eaglebine, Southeast Texas [Member] | Asset Disposed of by Sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net proceeds from divestitures				533
Gain (loss) on divestitures				282
Exploration And Production And Other Midstream Reporting Segment [Member] | Certain Onshore Domestic Assets Alaska [Member] | Asset Disposed of by Sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net proceeds from divestitures			370
Gain (loss) on divestitures	$ (154)		$ (33)
Exploration And Production And Other Midstream Reporting Segment [Member] | Certain U.S. Onshore Assets in Marcellus, Pennsylvania [Member] | Asset Disposed of by Sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net proceeds from divestitures				758
Gain (loss) on divestitures		$ (129)		(56)
Exploration And Production And Other Midstream Reporting Segment [Member] | Certain Onshore Domestic Assets, CBM, Utah [Member] | Asset Disposed of by Sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net proceeds from divestitures				69
Gain (loss) on divestitures				$ (52)
[1]	Includes the $126 million gain related to the 2017 property exchange discussed below.

Divestitures - Property Exchang

Divestitures - Property Exchange (Detail) - USD ($) $ in Millions	Mar. 17, 2017	Sep. 30, 2018	Sep. 30, 2017
Nonmonetary Transaction [Line Items]
Cash payment to acquire a third party's interest in the DBJV system		$ 4,891	$ 3,538
Delaware Basin Joint Venture System [Member]
Nonmonetary Transaction [Line Items]
Third party nonoperated interest percentage to be acquired	50.00%
Western Gas Partners, LP [Member] | Delaware Basin Joint Venture System [Member]
Nonmonetary Transaction [Line Items]
Cash payment to acquire a third party's interest in the DBJV system	$ 155
Gain on exchange	$ 126
Operated interest percentage		100.00%
Western Gas Partners, LP [Member] | Marcellus Assets [Member]
Nonmonetary Transaction [Line Items]
Non operated interest percentage	33.75%

Impairments - Additional Inform

Impairments - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Property, Plant, and Equipment [Line Items]
Impairments	$ 172	$ 0	$ 319	$ 383
Impairment of unproved properties			212	2,144
Assets Impaired During Fiscal Year to Date [Member]
Property, Plant, and Equipment [Line Items]
Impairments			319	383
Hard-minerals Properties [Member] | Assets Impaired During Fiscal Year to Date [Member]
Property, Plant, and Equipment [Line Items]
Impairment of long-lived assets held for use			145
Unproved Gulf of Mexico Properties [Member]
Property, Plant, and Equipment [Line Items]
Impairment of unproved properties			158	586
Unproved Shenandoah Properties [Member]
Property, Plant, and Equipment [Line Items]
Impairment of unproved properties				463
Exploration and Production [Member] | Gulf of Mexico Properties [Member] | Assets Impaired During Fiscal Year to Date [Member]
Property, Plant, and Equipment [Line Items]
Impairment of long-lived assets held for use				211
WES Midstream [Member] | DJ Basin Complex [Member] | Assets Impaired During Fiscal Year to Date [Member]
Property, Plant, and Equipment [Line Items]
Impairment of long-lived assets held for use			126
WES Midstream [Member] | Onshore Domestic [Member] | Assets Impaired During Fiscal Year to Date [Member]
Property, Plant, and Equipment [Line Items]
Impairment of long-lived assets held for use				168
Valuation, Income Approach [Member] | Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | Hard-minerals Properties [Member] | Assets Impaired During Fiscal Year to Date [Member]
Property, Plant, and Equipment [Line Items]
Fair value of long-lived assets held for use	$ 15		$ 15
Valuation, Income Approach [Member] | Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | Exploration and Production [Member] | Gulf of Mexico Properties [Member] | Assets Impaired During Fiscal Year to Date [Member]
Property, Plant, and Equipment [Line Items]
Fair value of long-lived assets held for use		231		231
Valuation, Income Approach [Member] | Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | WES Midstream [Member] | Onshore Domestic [Member] | Assets Impaired During Fiscal Year to Date [Member]
Property, Plant, and Equipment [Line Items]
Fair value of long-lived assets held for use		$ 58		$ 58

Exploratory Well Costs (Detail)

Exploratory Well Costs (Detail) - USD ($)	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Capitalized Exploratory Well Costs [Abstract]
Suspended exploratory well costs	$ 510,000,000	$ 525,000,000
Suspended exploratory well costs previously capitalized for a period greater than one year since the completion of drilling at December 31, 2016, charged to exploration expense	$ 0

Current Liabilities (Detail)

Current Liabilities (Detail) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Outstanding checks in excess of bank account balances	$ 205	$ 219
Other Current Liabilities
Accrued income taxes	79	71
Interest payable	169	246
Production, property, and other taxes payable	344	216
Accrued employee benefits	270	210
Derivatives	491	384
Other	149	183
Total other current liabilities	$ 1,502	$ 1,310

Derivative Instruments - Oil an

Derivative Instruments - Oil and Natural-Gas Production/Processing Derivative Activities Table (Detail) - Not Designated as Hedging Instrument [Member]	9 Months Ended
	Sep. 30, 2018MMBTU / dMBbls / d$ / bbl$ / MMBTU
Two Way Collars Oil 2018 [Member]
Derivative [Line Items]
Oil or NGL derivative nonmonetary notional amount per day | MBbls / d	108
Two Way Collars Oil 2018 [Member] | Call Option [Member] | Short [Member]
Average price per MMBtu or barrel
Average ceiling price | $ / bbl	60.48
Two Way Collars Oil 2018 [Member] | Put Option [Member] | Long [Member]
Average price per MMBtu or barrel
Average floor price | $ / bbl	50
Three Way Collars Oil 2019 [Member]
Derivative [Line Items]
Oil or NGL derivative nonmonetary notional amount per day | MBbls / d	87
Three Way Collars Oil 2019 [Member] | Call Option [Member] | Short [Member]
Average price per MMBtu or barrel
Average ceiling price | $ / bbl	72.98
Three Way Collars Oil 2019 [Member] | Put Option [Member] | Short [Member]
Average price per MMBtu or barrel
Average floor price	46.72
Three Way Collars Oil 2019 [Member] | Put Option [Member] | Long [Member]
Average price per MMBtu or barrel
Average floor price | $ / bbl	56.72
Forward Contracts Oil 2018 [Member]
Derivative [Line Items]
Oil or NGL derivative nonmonetary notional amount per day | MBbls / d	84
Average price per MMBtu or barrel
Average fixed price	61.45
Three Way Collars Natural Gas 2018 [Member]
Derivative [Line Items]
Natural-gas derivative nonmonetary notional amount per day | MMBTU / d	250
Three Way Collars Natural Gas 2018 [Member] | Call Option [Member] | Short [Member]
Average price per MMBtu or barrel
Average ceiling price	3.54
Three Way Collars Natural Gas 2018 [Member] | Put Option [Member] | Short [Member]
Average price per MMBtu or barrel
Average floor price	2
Three Way Collars Natural Gas 2018 [Member] | Put Option [Member] | Long [Member]
Average price per MMBtu or barrel
Average floor price	2.75
Forward Contracts Natural Gas 2018 [Member]
Derivative [Line Items]
Natural-gas derivative nonmonetary notional amount per day | MMBTU / d	280
Average price per MMBtu or barrel
Average fixed price	3.02

Derivative Instruments - Additi

Derivative Instruments - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	9 Months Ended
	Aug. 31, 2018	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Derivative [Line Items]
Additional collateral if credit rating downgraded		$ 124
Amount of collateral posted related to derivative instruments with credit-risk-related contingent features		49		$ 170
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Aggregate fair value of derivative instruments with credit-risk-related contingent features for which a net liability position existed (net of collateral)		(1,400)		$ (1,400)
Not Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Cash payment for interest-rate swap agreements		101	$ 118
Not Designated as Hedging Instrument [Member] | Interest-Rate Swap 3 [Member]
Derivative [Line Items]
Notional principal amount of interest-rate swap	$ 200	100
Not Designated as Hedging Instrument [Member] | Interest-Rate Swap 3 [Member] | Cash Payments To Amend Interest Rate Swap Agreements [Member]
Derivative [Line Items]
Cash payment for interest-rate swap agreements	$ 10
Not Designated as Hedging Instrument [Member] | Interest Rate Swaps 1 Through 5 [Member]
Derivative [Line Items]
Notional principal amount of interest-rate swap		$ 1,600

Derivative Instruments - Intere

Derivative Instruments - Interest-Rate Derivatives Table (Detail) - Not Designated as Hedging Instrument [Member] - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Aug. 31, 2018
Interest-Rate Swap 1 [Member]
Derivative [Line Items]
Notional principal amount of interest-rate swap	$ 550
Reference period start date for interest-rate swap	Sep. 15, 2016
Reference period end date for interest-rate swap	Sep. 15, 2046
Mandatory termination date for interest-rate swap	Sep. 1, 2020
Weighted-average interest rate for interest-rate swap	6.418%
Interest-Rate Swap 2 [Member]
Derivative [Line Items]
Notional principal amount of interest-rate swap	$ 250
Reference period start date for interest-rate swap	Sep. 15, 2016
Reference period end date for interest-rate swap	Sep. 15, 2046
Mandatory termination date for interest-rate swap	Sep. 1, 2022
Weighted-average interest rate for interest-rate swap	6.809%
Interest-Rate Swap 3 [Member]
Derivative [Line Items]
Notional principal amount of interest-rate swap	$ 100	$ 200
Reference period start date for interest-rate swap	Sep. 15, 2017
Reference period end date for interest-rate swap	Sep. 15, 2047
Mandatory termination date for interest-rate swap	Sep. 1, 2020
Weighted-average interest rate for interest-rate swap	6.891%
Interest-Rate Swap 4 [Member]
Derivative [Line Items]
Notional principal amount of interest-rate swap	$ 250
Reference period start date for interest-rate swap	Sep. 15, 2017
Reference period end date for interest-rate swap	Sep. 15, 2047
Mandatory termination date for interest-rate swap	Sep. 1, 2021
Weighted-average interest rate for interest-rate swap	6.57%
Interest-Rate Swap 5 [Member]
Derivative [Line Items]
Notional principal amount of interest-rate swap	$ 450
Reference period start date for interest-rate swap	Sep. 15, 2017
Reference period end date for interest-rate swap	Sep. 15, 2047
Mandatory termination date for interest-rate swap	Sep. 1, 2023
Weighted-average interest rate for interest-rate swap	6.445%

Derivative Instruments - Effect

Derivative Instruments - Effect of Derivative Instruments - Balance Sheet Table (Detail) - Not Designated as Hedging Instrument [Member] - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Derivatives Fair Value [Line Items]
Gross derivative assets	$ 112	$ 108
Gross derivative liabilities	(1,604)	(1,628)
Commodity derivatives [Member]
Derivatives Fair Value [Line Items]
Gross derivative assets	37	54
Gross derivative liabilities	(496)	(209)
Commodity derivatives [Member] | Other current assets [Member]
Derivatives Fair Value [Line Items]
Gross derivative assets	2	7
Gross derivative liabilities	0	(1)
Commodity derivatives [Member] | Other assets [Member]
Derivatives Fair Value [Line Items]
Gross derivative assets	0	2
Gross derivative liabilities	0	0
Commodity derivatives [Member] | Other current liabilities [Member]
Derivatives Fair Value [Line Items]
Gross derivative assets	20	45
Gross derivative liabilities	(440)	(206)
Commodity derivatives [Member] | Other liabilities [Member]
Derivatives Fair Value [Line Items]
Gross derivative assets	15	0
Gross derivative liabilities	(56)	(2)
Interest-rate derivatives [Member]
Derivatives Fair Value [Line Items]
Gross derivative assets	75	54
Gross derivative liabilities	(1,108)	(1,419)
Interest-rate derivatives [Member] | Other current assets [Member]
Derivatives Fair Value [Line Items]
Gross derivative assets	21	14
Gross derivative liabilities	0	0
Interest-rate derivatives [Member] | Other assets [Member]
Derivatives Fair Value [Line Items]
Gross derivative assets	54	40
Gross derivative liabilities	0	0
Interest-rate derivatives [Member] | Other current liabilities [Member]
Derivatives Fair Value [Line Items]
Gross derivative assets	0	0
Gross derivative liabilities	(80)	(236)
Interest-rate derivatives [Member] | Other liabilities [Member]
Derivatives Fair Value [Line Items]
Gross derivative assets	0	0
Gross derivative liabilities	$ (1,028)	$ (1,183)

Derivative Instruments - Effe_2

Derivative Instruments - Effect of Derivative Instruments - Statement of Income Table (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Derivative [Line Items]
Total (gains) losses on derivatives, net	$ 33	$ 82	$ 506	$ (33)
Commodity derivatives [Member] | Gathering, processing, and marketing sales [Member]
Derivative [Line Items]
Total (gains) losses on derivatives, net	1	0	3	0
Commodity derivatives [Member] | (Gains) losses on derivatives, net [Member]
Derivative [Line Items]
Total (gains) losses on derivatives, net	104	43	734	(164)
Interest-rate derivatives [Member] | (Gains) losses on derivatives, net [Member]
Derivative [Line Items]
Total (gains) losses on derivatives, net	$ (72)	$ 39	$ (231)	$ 131

Derivative Instruments - Fair V

Derivative Instruments - Fair Value Table (Detail) - Not Designated as Hedging Instrument [Member] - USD ($) $ in Millions	Sep. 30, 2018		Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gross derivative assets	$ 112		$ 108
Gross derivative liabilities	(1,604)		(1,628)
Derivative assets Netting	(35)	[1]	(46)
Derivative liabilities Netting	35	[1]	46
Derivative assets, Collateral	0		(1)
Derivative liabilities, Collateral	55		173
Derivative assets	77		61
Derivative liabilities	(1,514)		(1,409)
Commodity derivatives [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gross derivative assets	37		54
Gross derivative liabilities	(496)		(209)
Derivative assets Netting	(35)	[1]	(46)
Derivative liabilities Netting	35	[1]	46
Derivative assets, Collateral	0		(1)
Derivative liabilities, Collateral	6		3
Derivative assets	2		7
Derivative liabilities	(455)		(160)
Interest-rate derivatives [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gross derivative assets	75		54
Gross derivative liabilities	(1,108)		(1,419)
Derivative assets Netting	0	[1]	0
Derivative liabilities Netting	0	[1]	0
Derivative assets, Collateral	0		0
Derivative liabilities, Collateral	49		170
Derivative assets	75		54
Derivative liabilities	(1,059)		(1,249)
Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gross derivative assets	0		1
Gross derivative liabilities	0		(1)
Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gross derivative assets	112		107
Gross derivative liabilities	(1,604)		(1,627)
Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gross derivative assets	0		0
Gross derivative liabilities	0		0
Recurring [Member] | Commodity derivatives [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gross derivative assets	0		1
Gross derivative liabilities	0		(1)
Recurring [Member] | Commodity derivatives [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gross derivative assets	37		53
Gross derivative liabilities	(496)		(208)
Recurring [Member] | Commodity derivatives [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gross derivative assets	0		0
Gross derivative liabilities	0		0
Recurring [Member] | Interest-rate derivatives [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gross derivative assets	0		0
Gross derivative liabilities	0		0
Recurring [Member] | Interest-rate derivatives [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gross derivative assets	75		54
Gross derivative liabilities	(1,108)		(1,419)
Recurring [Member] | Interest-rate derivatives [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gross derivative assets	0		0
Gross derivative liabilities	$ 0		$ 0
[1]	Represents the impact of netting commodity derivative assets and liabilities with counterparties where the Company has the contractual right and intends to net settle.

Tangible Equity Units - Additio

Tangible Equity Units - Additional Information (Detail) shares in Millions, $ in Millions	Jun. 07, 2018USD ($)$ / unitshares	Jun. 30, 2015USD ($)$ / unitshares	Sep. 30, 2018USD ($)
TEUs - senior amortizing notes due 2018 [Member]
Tangible Equity Units [Line Items]
Principal amount per amortizing note | $ / unit	10.95
Debt instrument, stated interest rate	1.50%
Final payment | $	$ 9		$ 17
Debt instrument, maturity date	Jun. 7, 2018
7.50% Tangible Equity Units [Member]
Tangible Equity Units [Line Items]
Number of tangible equity units issued		9.2
Tangible equity unit rate		7.50%
Stated amount per tangible equity unit | $ / unit		50
Total net proceeds | $		$ 445
Equity Component of 7.50% Tangible Equity Units [Member] | Settled in WGP Common Units [Member]
Tangible Equity Units [Line Items]
Purchase contract, mandatory settlement date	Jun. 7, 2018
Number of tangible equity units settled	9.2
Shares, Issued	8.2
Settlement rate	0.8921

Debt - Debt Activity Table (Det

Debt - Debt Activity Table (Detail) - USD ($) $ in Millions		Jun. 07, 2018	Sep. 30, 2018	Aug. 31, 2018	Mar. 31, 2018
Changes in Debt Outstanding [Roll Forward]
Balance at December 31, 2017	[1]		$ 15,458
Other, net			41
Balance at September 30, 2018	[1]		16,467
Western Gas Partners, LP [Member]
Changes in Debt Outstanding [Roll Forward]
Balance at December 31, 2017	[1]		3,465
Other, net			2
Balance at September 30, 2018	[1]		4,566
Western Gas Equity Partners, LP excluding WES [Member]
Changes in Debt Outstanding [Roll Forward]
Balance at December 31, 2017	[1],[2]		28
Balance at September 30, 2018	[1],[2]		28
Anadarko excluding WES and WGP [Member]
Changes in Debt Outstanding [Roll Forward]
Balance at December 31, 2017	[1],[3]		11,965
Other, net	[3]		39
Balance at September 30, 2018	[1],[3]		11,873
WES RCF [Member]
Changes in Debt Outstanding [Roll Forward]
Borrowings, credit facility			320
Repayments, credit facility			(690)
WES RCF [Member] | Western Gas Partners, LP [Member]
Changes in Debt Outstanding [Roll Forward]
Borrowings, credit facility			320
Repayments, credit facility			(690)
WES 4.500% Senior Notes due 2028 [Member]
Changes in Debt Outstanding [Roll Forward]
Issuances			394
WES 4.500% Senior Notes due 2028 [Member] | Western Gas Partners, LP [Member]
Changes in Debt Outstanding [Roll Forward]
Issuances			$ 394
Debt instrument, stated interest rate			4.50%		4.50%
Debt instrument, maturity date			Mar. 1, 2028
WES 5.300% Senior Notes due 2048 [Member]
Changes in Debt Outstanding [Roll Forward]
Issuances			$ 687
WES 5.300% Senior Notes due 2048 [Member] | Western Gas Partners, LP [Member]
Changes in Debt Outstanding [Roll Forward]
Issuances			$ 687
Debt instrument, stated interest rate			5.30%		5.30%
Debt instrument, maturity date			Mar. 1, 2048
WES 4.750% Senior Notes due 2028 [Member]
Changes in Debt Outstanding [Roll Forward]
Issuances			$ 396
WES 4.750% Senior Notes due 2028 [Member] | Western Gas Partners, LP [Member]
Changes in Debt Outstanding [Roll Forward]
Issuances			$ 396
Debt instrument, stated interest rate			4.75%	4.75%
Debt instrument, maturity date			Aug. 1, 2028
WES 5.500% Senior Notes due 2048 [Member]
Changes in Debt Outstanding [Roll Forward]
Issuances			$ 342
WES 5.500% Senior Notes due 2048 [Member] | Western Gas Partners, LP [Member]
Changes in Debt Outstanding [Roll Forward]
Issuances			$ 342
Debt instrument, stated interest rate			5.50%	5.50%
Debt instrument, maturity date			Aug. 1, 2048
Senior Note Component of 7.50% Tangible Equity Units [Member]
Changes in Debt Outstanding [Roll Forward]
Repayments, senior notes		$ (9)	$ (17)
Debt instrument, stated interest rate		1.50%
Debt instrument, maturity date		Jun. 7, 2018
Senior Note Component of 7.50% Tangible Equity Units [Member] | Anadarko excluding WES and WGP [Member]
Changes in Debt Outstanding [Roll Forward]
Repayments, senior notes	[3]		(17)
7.050% Debentures due 2018 [Member]
Changes in Debt Outstanding [Roll Forward]
Repayments, senior notes			(114)
7.050% Debentures due 2018 [Member] | Anadarko excluding WES and WGP [Member]
Changes in Debt Outstanding [Roll Forward]
Repayments, senior notes	[3]		$ (114)
Debt instrument, stated interest rate			7.05%
Debt instrument, maturity date			Mar. 1, 2018
WES 2.600% Senior Notes due 2018 [Member]
Changes in Debt Outstanding [Roll Forward]
Repayments, credit facility			$ (350)
WES 2.600% Senior Notes due 2018 [Member] | Western Gas Partners, LP [Member]
Changes in Debt Outstanding [Roll Forward]
Repayments, credit facility			$ (350)
Debt instrument, stated interest rate			2.60%
Debt instrument, maturity date			Aug. 1, 2018
[1]	The Company’s outstanding borrowings, except for borrowings under the WGP RCF, are senior unsecured.
[2]	Excludes WES.
[3]	Excludes WES and WGP.

Debt - Outstanding Debt Table (

Debt - Outstanding Debt Table (Detail) - USD ($) $ in Millions		Sep. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Total borrowings at face value		$ 18,031	$ 17,032
Net unamortized discounts, premiums, and debt issuance costs	[1]	(1,564)	(1,574)
Total borrowings	[2]	16,467	15,458
Capital lease obligations		226	231
Less short-term debt		938	142
Total long-term debt		15,755	15,547
Western Gas Partners, LP [Member]
Debt Instrument [Line Items]
Total borrowings at face value		4,620	3,490
Net unamortized discounts, premiums, and debt issuance costs	[1]	(54)	(25)
Total borrowings	[2]	4,566	3,465
Capital lease obligations		0	0
Less short-term debt		0	0
Total long-term debt		4,566	3,465
Western Gas Equity Partners, LP excluding WES [Member]
Debt Instrument [Line Items]
Total borrowings at face value	[3]	28	28
Net unamortized discounts, premiums, and debt issuance costs	[1],[3]	0	0
Total borrowings	[2],[3]	28	28
Capital lease obligations	[3]	0	0
Less short-term debt	[3]	28	0
Total long-term debt	[3]	0	28
Anadarko excluding WES and WGP [Member]
Debt Instrument [Line Items]
Total borrowings at face value	[4]	13,383	13,514
Net unamortized discounts, premiums, and debt issuance costs	[1],[4]	(1,510)	(1,549)
Total borrowings	[2],[4]	11,873	11,965
Capital lease obligations	[4]	226	231
Less short-term debt	[4]	910	142
Total long-term debt	[4]	$ 11,189	$ 12,054
[1]	Unamortized discounts, premiums, and debt issuance costs are amortized over the term of the related debt. Debt issuance costs related to RCFs are included in other current assets and other assets on the Company’s Consolidated Balance Sheets.
[2]	The Company’s outstanding borrowings, except for borrowings under the WGP RCF, are senior unsecured.
[3]	Excludes WES.
[4]	Excludes WES and WGP.

Debt - Additional Information (

Debt - Additional Information (Detail) - USD ($)		1 Months Ended		9 Months Ended
		Feb. 28, 2018	Jan. 31, 2018	Sep. 30, 2018	Aug. 31, 2018	Jun. 07, 2018	Mar. 31, 2018	Feb. 01, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Total borrowings at face value				$ 18,031,000,000					$ 17,032,000,000
APC RCF [Member]
Debt Instrument [Line Items]
Line of credit, maximum capacity			$ 3,000,000,000
Line of credit, expiration date			Jan. 23, 2022
Line of credit, outstanding borrowings				$ 0
364-Day Credit Facility Due 2017 [Member]
Debt Instrument [Line Items]
Line of credit, maximum capacity			$ 2,000,000,000
Line of credit, expiration date			Jan. 12, 2019
Debt instrument, term				364 days
Line of credit, outstanding borrowings				$ 0
WES RCF [Member]
Debt Instrument [Line Items]
Borrowings, credit facility				320,000,000
Repayments, credit facility				(690,000,000)
Fair Value, Inputs, Level 2 [Member] | Valuation, Market Approach [Member]
Debt Instrument [Line Items]
Estimated fair value of total borrowings				17,800,000,000					17,700,000,000
TEUs - senior amortizing notes due 2018 [Member]
Debt Instrument [Line Items]
Debt instrument, stated interest rate						1.50%
8.70% Senior Notes due March 2019
Debt Instrument [Line Items]
Outstanding borrowings				$ 600,000,000
Line of credit, interest rate				8.70%
6.950% Senior Notes Due June 2019 [Member]
Debt Instrument [Line Items]
Outstanding borrowings				$ 300,000,000
Line of credit, interest rate				6.95%
Zero-Coupon Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, earliest call date				Oct. 10, 2019
Zero-Coupon Senior Notes [Member] | Accreted Value at Next Potential Put Date [Member]
Debt Instrument [Line Items]
Debt instrument, accreted value				$ 980,000,000
WES 4.750% Senior Notes due 2028 [Member]
Debt Instrument [Line Items]
Borrowings during period				396,000,000
WES 5.500% Senior Notes due 2048 [Member]
Debt Instrument [Line Items]
Borrowings during period				342,000,000
WES 2.600% Senior Notes due 2018 [Member]
Debt Instrument [Line Items]
Repayments, credit facility				(350,000,000)
WES 4.500% Senior Notes due 2028 [Member]
Debt Instrument [Line Items]
Borrowings during period				394,000,000
WES 5.300% Senior Notes due 2048 [Member]
Debt Instrument [Line Items]
Borrowings during period				687,000,000
Western Gas Partners, LP [Member]
Debt Instrument [Line Items]
Total borrowings at face value				4,620,000,000					3,490,000,000
Western Gas Partners, LP [Member] | WES RCF [Member]
Debt Instrument [Line Items]
Line of credit, maximum capacity		$ 1,500,000,000
Line of credit, expiration date		Feb. 26, 2023	Feb. 26, 2020
Line of credit, outstanding borrowings				0
Line of credit, expandable maximum capacity		$ 2,000,000,000
Borrowings, credit facility				320,000,000
Repayments, credit facility				(690,000,000)
Letters of credit, outstanding				5,000,000
Line of credit, available borrowing capacity				$ 1,495,000,000
Western Gas Partners, LP [Member] | WES 4.750% Senior Notes due 2028 [Member]
Debt Instrument [Line Items]
Debt instrument, stated interest rate				4.75%	4.75%
Total borrowings at face value					$ 400,000,000
Borrowings during period				$ 396,000,000
Western Gas Partners, LP [Member] | WES 5.500% Senior Notes due 2048 [Member]
Debt Instrument [Line Items]
Debt instrument, stated interest rate				5.50%	5.50%
Total borrowings at face value					$ 350,000,000
Borrowings during period				$ 342,000,000
Western Gas Partners, LP [Member] | WES 2.600% Senior Notes due 2018 [Member]
Debt Instrument [Line Items]
Debt instrument, stated interest rate				2.60%
Repayments, credit facility				$ (350,000,000)
Total borrowings at face value				$ 350,000,000
Western Gas Partners, LP [Member] | WES 4.500% Senior Notes due 2028 [Member]
Debt Instrument [Line Items]
Debt instrument, stated interest rate				4.50%			4.50%
Total borrowings at face value							$ 400,000,000
Borrowings during period				$ 394,000,000
Western Gas Partners, LP [Member] | WES 5.300% Senior Notes due 2048 [Member]
Debt Instrument [Line Items]
Debt instrument, stated interest rate				5.30%			5.30%
Total borrowings at face value							$ 700,000,000
Borrowings during period				$ 687,000,000
Western Gas Equity Partners, LP excluding WES [Member]
Debt Instrument [Line Items]
Total borrowings at face value	[1]			28,000,000					$ 28,000,000
Western Gas Equity Partners, LP excluding WES [Member] | WGP RCF [Member]
Debt Instrument [Line Items]
Line of credit, expiration date		Mar. 14, 2019
Line of credit, outstanding borrowings				28,000,000
Line of credit, available borrowing capacity			$ 250,000,000	$ 7,000,000				$ 35,000,000
Line of credit, interest rate				4.25%
[1]	Excludes WES.

Income Taxes - Income Tax Expen

Income Taxes - Income Tax Expense (Benefit) Table (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Current income tax expense (benefit)	$ 146	$ 430	$ 383	$ 670
Deferred income tax expense (benefit)	110	(855)	124	(1,036)
Total income tax expense (benefit)	256	(425)	507	(366)
Income (loss) before income taxes	$ 683	$ (1,066)	$ 1,125	$ (1,616)
Effective tax rate	37.00%	40.00%	45.00%	23.00%

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Line Items]
Tax reform legislation income tax benefit	$ 5
Income tax benefit	(256)	$ 425	$ (507)	$ 366
Tronox Litigation [Member] | Judicial Ruling [Member]
Income Tax Disclosure [Line Items]
Income tax benefit			346		$ 346
Unrecognized tax benefits	$ 1,200		$ 1,200		$ 1,200
Income tax refunds						$ 881

Pension Plans and Other Postr_3

Pension Plans and Other Postretirement Benefits - Components of Net Periodic Benefit Cost Table (Detail) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2018		Sep. 30, 2017	Sep. 30, 2018		Sep. 30, 2017
Pension Benefits [Member]
Components of net periodic benefit cost
Service cost	$ 23		$ 22	$ 68		$ 64
Interest cost	19		21	57		63
Expected (return) loss on plan assets	(20)		(21)	(61)		(63)
Amortization of net actuarial loss (gain)	6		7	19		20
Amortization of net prior service cost (credit)	0		(1)	0		(1)
Settlement expense	9	[1]	22	9		80
Termination benefits expense	7		0	7		4
Net periodic benefit cost	44		50	99	[1]	167
Other Benefits [Member]
Components of net periodic benefit cost
Service cost	0		0	1		1
Interest cost	3		3	8		9
Expected (return) loss on plan assets	0		0	0		0
Amortization of net actuarial loss (gain)	0		0	0		0
Amortization of net prior service cost (credit)	(6)		(6)	(18)		(18)
Settlement expense	0	[1]	0	0		0
Termination benefits expense	0		0	0		0
Net periodic benefit cost	$ (3)		$ (3)	$ (9)	[1]	$ (8)
[1]	The service cost component of net periodic benefit cost is included in G&A; oil and gas operating expense; gathering, processing, and marketing expense; and exploration expense, and all other components of net periodic benefit cost are included in other (income) expense on the Company’s Consolidated Statements of Income.

Pension Plans and Other Postr_4

Pension Plans and Other Postretirement Benefits - Additional Information (Detail) - Pension Benefits [Member] $ in Millions	9 Months Ended
	Sep. 30, 2018USD ($)
Funded Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 161
Expected employer contributions in 2018	1
Unfunded Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	36
Expected employer contributions in 2018	$ 26

Stockholders' Equity - Earnings

Stockholders' Equity - Earnings Per Share Reconciliation (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Net income (loss)
Net income (loss) attributable to common stockholders	$ 363	$ (699)	$ 513	$ (1,432)
Income (loss) effect of TEUs	0	(2)	(4)	(6)
Less distributions on participating securities	2	0	4	0
Less undistributed income allocated to participating securities	2	0	1	0
Basic	359	(701)	504	(1,438)
Income (loss) effect of TEUs	0	0	0	(1)
Diluted	$ 359	$ (701)	$ 504	$ (1,439)
Shares
Average number of common shares outstanding—basic	499	553	507	552
Dilutive effect of stock options	1	0	1	0
Average number of common shares outstanding—diluted	500	553	508	552
Excluded due to anti-dilutive effect	8	11	9	11
Net income (loss) per common share
Basic (in usd per share)	$ 0.72	$ (1.27)	$ 0.99	$ (2.60)
Diluted (in usd per share)	$ 0.72	$ (1.27)	$ 0.99	$ (2.61)

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	1 Months Ended				9 Months Ended	12 Months Ended
	Sep. 30, 2018	Aug. 31, 2018	Jun. 30, 2018	Feb. 28, 2018	Sep. 30, 2018	Sep. 30, 2018	Jul. 31, 2018	Sep. 30, 2017
Equity, Class of Treasury Stock [Line Items]
Authorized share-repurchase program				$ 3,000			$ 4,000	$ 2,500
Total Shares Delivered					38.3
Amount of share repurchase program completed					$ 2,441	$ 3,500
Accelerated Stock Repurchase Program [Member]
Equity, Class of Treasury Stock [Line Items]
Amount	$ 1,941		$ 1,441	$ 500	$ 1,941	$ 1,941
Average Price per Share (in usd per share)			$ 65.28	$ 58.82
Initial Shares Delivered			19.1	7	26.1
Additional Shares Delivered			3	1.5	4.5
Total Shares Delivered			22.1	8.5	30.6
Open-market Stock Purchases [Member]
Equity, Class of Treasury Stock [Line Items]
Amount	$ 250	$ 250			$ 500
Average Price per Share (in usd per share)	$ 63.11	$ 66.14
Total Shares Delivered	3.9	3.8			7.7

Noncontrolling Interests (Detai

Noncontrolling Interests (Detail) - shares shares in Thousands	Jun. 07, 2018	Mar. 01, 2017	Sep. 30, 2018	Dec. 31, 2017	Dec. 31, 2016
Western Gas Partners, LP [Member] | Limited Partner [Member]
Noncontrolling Interest [Line Items]
Public ownership interest in subsidiary			59.40%
Western Gas Partners, LP [Member] | Limited Partner [Member] | Western Gas Equity Partners, LP Ownership Interest in Western Gas Partners, LP [Member]
Noncontrolling Interest [Line Items]
Ownership interest in subsidiary			29.60%
Western Gas Partners, LP [Member] | Limited Partner [Member] | Anadarko Limited Partner Interest in WES Owned Through Other Subsidiaries [Member]
Noncontrolling Interest [Line Items]
Ownership interest in subsidiary			9.50%
Western Gas Partners, LP [Member] | General Partner [Member] | Western Gas Equity Partners, LP Ownership Interest in Western Gas Partners, LP [Member]
Noncontrolling Interest [Line Items]
Ownership interest in subsidiary			1.50%
Western Gas Equity Partners, LP [Member] | Limited Partner [Member]
Noncontrolling Interest [Line Items]
Ownership interest in subsidiary			77.80%
Public ownership interest in subsidiary			22.20%
Series A Preferred Units [Member] | Western Gas Partners, LP [Member]
Noncontrolling Interest [Line Items]
Units issued in private placement					22,000
Percentage of units converted		50.00%
Class C Units [Member] | Western Gas Partners, LP [Member]
Noncontrolling Interest [Line Items]
Units issued in private placement			802	886
Equity Component of 7.50% Tangible Equity Units [Member] | Settled in WGP Common Units [Member]
Noncontrolling Interest [Line Items]
Number of tangible equity units settled	9,200
Shares, Issued	8,200

Variable Interest Entities (Det

Variable Interest Entities (Detail) - Variable Interest Entity, Primary Beneficiary [Member] - Western Gas Partners, LP [Member] - USD ($) $ in Millions	1 Months Ended	9 Months Ended
	May 31, 2008	Sep. 30, 2018	Sep. 30, 2017
Variable Interest Entity [Line Items]
Note receivable for WES	$ 260
Debt instrument, term	30 years
Fixed annual rate	6.50%
Interest income for WES		$ 13	$ 13
Above-market component of swap extensions with Anadarko		$ 41	$ 47

Variable Interest Entities - Fi

Variable Interest Entities - Financial Data of WGP (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Statement of Operations Data
Total revenues and other		$ 3,697,000	$ 2,496,000	$ 10,033,000	$ 8,979,000
Operating income (loss)		979,000	(749,000)	2,349,000	(916,000)
Net Income (Loss)		427,000	(641,000)	618,000	(1,250,000)
Statement of Cash Flow Data
Net cash provided by (used in) operating activities				4,302,000	2,619,000
Net cash provided by (used in) investing activities				(4,659,000)	(28,000)
Net cash provided by (used in) financing activities				(2,306,000)	(527,000)
Balance Sheet Data
Cash and cash equivalents		1,883,000		1,883,000		$ 4,553,000
Net properties and equipment related to VIEs		28,744,000		28,744,000		27,451,000
Total assets		41,145,000		41,145,000		42,086,000
Long-term debt		15,755,000		15,755,000		15,547,000
Total equity		11,237,000		11,237,000		13,790,000
Variable Interest Entity, Primary Beneficiary [Member]
Balance Sheet Data
Cash and cash equivalents		133,000		133,000		80,000
Net properties and equipment related to VIEs		6,419,000		6,419,000		5,731,000
WGP [Member]
Balance Sheet Data
Long-term debt	[1]	0		0		28,000
WGP [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Statement of Operations Data
Total revenues and other		508	575	1,432	1,616
Operating income (loss)		200	179	461	523
Net Income (Loss)		155	$ 147	340	424
Statement of Cash Flow Data
Net cash provided by (used in) operating activities				749	642
Net cash provided by (used in) investing activities				(1,161)	(515)
Net cash provided by (used in) financing activities				465	$ (334)
Balance Sheet Data
Cash and cash equivalents		133		133		80
Net properties and equipment related to VIEs		6,419		6,419		5,731
Total assets		9,034		9,034		8,016
Long-term debt		4,566		4,566		3,493
Total liabilities		5,417		5,417		4,071
Total equity		$ 3,617		$ 3,617		$ 3,945
[1]	Excludes WES.

Supplemental Cash Flow Inform_3

Supplemental Cash Flow Information (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash paid (received)
Interest, net of amounts capitalized	$ 813	$ 764
Income taxes, net of refunds	48	169
Non-cash investing activities
Fair value of properties and equipment acquired	8	619
Asset retirement cost additions	261	228
Accruals of property, plant, and equipment	886	786
Net liabilities assumed (divested) in acquisitions and divestitures	(97)	(115)
Non-cash investing and financing activities
Deferred drilling lease liability	0	14
Settlement of tangible equity units	$ 300	$ 0

Supplemental Cash Flow Inform_4

Supplemental Cash Flow Information - Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents (Detail) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Cash and Cash Equivalents [Line Items]
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents	$ 1,993	$ 4,674	$ 5,376	$ 3,308
Cash and Cash Equivalents [Member]
Cash and Cash Equivalents [Line Items]
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents	1,883	4,553
Restricted cash and restricted cash equivalents	134	255
Other Assets [Member]
Cash and Cash Equivalents [Line Items]
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents	$ 110	$ 121

Segment Information - Additiona

Segment Information - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2018Segment
Segment Reporting [Abstract]
Number of reporting segments	3

Segment Information - Reconcili

Segment Information - Reconciliation of Consolidated Adjusted EBITDAX to Income (Loss) Before Income Taxes (Detail) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2018		Sep. 30, 2017	Sep. 30, 2018		Sep. 30, 2017
Segment Reporting Information [Line Items]
Income (loss) before income taxes	$ 683		$ (1,066)	$ 1,125		$ (1,616)
Interest expense	240		230	705		682
DD&A	1,130		1,083	3,123		3,235
Exploration expense	118	[1]	750	380	[1]	2,366
(Gains) losses on divestitures, net	(3)		194	(31)		(815)
Impairments	172		0	319		383
Total (gains) losses on derivatives, net, less net cash from settlement of commodity derivatives	(167)		98	73		(12)
Restructuring charges	13		3	13		20
Less net income (loss) attributable to noncontrolling interests	64		58	105		182
Consolidated Adjusted EBITDAX	2,122		$ 1,234	5,602		$ 4,061
Exploration Expense [Member]
Segment Reporting Information [Line Items]
Restructuring charges	$ 20			$ 20
[1]	Includes restructuring charges of $20 million for the three and nine months ended September 30, 2018.

Segment Information - Selected

Segment Information - Selected Financial Information for Anadarko's Reporting Segments Table (Detail) - USD ($) $ in Millions		3 Months Ended			9 Months Ended
		Sep. 30, 2018		Sep. 30, 2017	Sep. 30, 2018		Sep. 30, 2017
Segment Reporting Information [Line Items]
Sales Revenues		$ 3,851			$ 10,501
Other		87		$ 80	201		$ 237
Total revenues and other		3,697		2,496	10,033		8,979
Operating costs and expenses		2,718		3,245	7,684		9,895
Net cash from settlement of commodity derivatives					433		(21)
Other (income) expense, net		24		5	16		51
Net income (loss) attributable to noncontrolling interests		64		58	105		182
Total expenses and other		1,572		1,456	4,407		4,101
Consolidated Adjusted EBITDAX		2,122		1,234	5,602		4,061
(Gains) losses on derivatives, net [Member] | Commodity Contract [Member]
Segment Reporting Information [Line Items]
Net cash from settlement of commodity derivatives		199		(16)	437		(23)
Gathering, processing, and marketing sales [Member] | Commodity Contract [Member] | Not Designated as Hedging Instrument [Member]
Segment Reporting Information [Line Items]
Total (gains) losses on derivatives, net included in marketing revenue, less net cash from settlement		0			7		(2)
Excluding Gains Losses On Divestitures Net [Member]
Segment Reporting Information [Line Items]
Total revenues and other	[1]	3,694		2,690	10,002		8,164
Excluding Certain Items [Member]
Segment Reporting Information [Line Items]
Operating costs and expenses	[2]	1,292		1,412	3,856		3,918
Excluding Certain Other Nonoperating Items [Member]
Segment Reporting Information [Line Items]
Other (income) expense, net		17	[3]	2	9	[3]	24
Operating Segments [Member] | Exploration and Production [Member]
Segment Reporting Information [Line Items]
Sales Revenues		3,195			8,654
Other		1		6	(5)		16
Total revenues and other		3,192			8,657
Net income (loss) attributable to noncontrolling interests		0		0	0		0
Total expenses and other		1,059		956	2,840		2,679
Consolidated Adjusted EBITDAX		2,128		1,151	5,793		3,847
Operating Segments [Member] | Exploration and Production [Member] | (Gains) losses on derivatives, net [Member] | Commodity Contract [Member]
Segment Reporting Information [Line Items]
Net cash from settlement of commodity derivatives		0		0	0		0
Operating Segments [Member] | Exploration and Production [Member] | Gathering, processing, and marketing sales [Member] | Commodity Contract [Member] | Not Designated as Hedging Instrument [Member]
Segment Reporting Information [Line Items]
Total (gains) losses on derivatives, net included in marketing revenue, less net cash from settlement		0			0		0
Operating Segments [Member] | Exploration and Production [Member] | Excluding Gains Losses On Divestitures Net [Member]
Segment Reporting Information [Line Items]
Total revenues and other	[1]	3,187		2,107	8,633		6,526
Operating Segments [Member] | Exploration and Production [Member] | Excluding Certain Items [Member]
Segment Reporting Information [Line Items]
Operating costs and expenses	[2]	1,059		956	2,840		2,679
Operating Segments [Member] | Exploration and Production [Member] | Excluding Certain Other Nonoperating Items [Member]
Segment Reporting Information [Line Items]
Other (income) expense, net		0	[3]	0	0	[3]	0
Operating Segments [Member] | WES Midstream [Member]
Segment Reporting Information [Line Items]
Sales Revenues		511			1,438
Other		52		39	113		124
Total revenues and other		560			1,545
Net income (loss) attributable to noncontrolling interests		0		0	0		0
Total expenses and other		245		345	687		936
Consolidated Adjusted EBITDAX		315		258	858		788
Operating Segments [Member] | WES Midstream [Member] | (Gains) losses on derivatives, net [Member] | Commodity Contract [Member]
Segment Reporting Information [Line Items]
Net cash from settlement of commodity derivatives		0		0	0		0
Operating Segments [Member] | WES Midstream [Member] | Gathering, processing, and marketing sales [Member] | Commodity Contract [Member] | Not Designated as Hedging Instrument [Member]
Segment Reporting Information [Line Items]
Total (gains) losses on derivatives, net included in marketing revenue, less net cash from settlement		0			0		0
Operating Segments [Member] | WES Midstream [Member] | Excluding Gains Losses On Divestitures Net [Member]
Segment Reporting Information [Line Items]
Total revenues and other	[1]	560		603	1,545		1,724
Operating Segments [Member] | WES Midstream [Member] | Excluding Certain Items [Member]
Segment Reporting Information [Line Items]
Operating costs and expenses	[2]	245		345	687		936
Operating Segments [Member] | WES Midstream [Member] | Excluding Certain Other Nonoperating Items [Member]
Segment Reporting Information [Line Items]
Other (income) expense, net		0	[3]	0	0	[3]	0
Operating Segments [Member] | Other Midstream [Member]
Segment Reporting Information [Line Items]
Sales Revenues		113			255
Other		11		7	30		20
Total revenues and other		129			301
Net income (loss) attributable to noncontrolling interests		0		0	0		0
Total expenses and other		55		62	134		168
Consolidated Adjusted EBITDAX		73		41	157		111
Operating Segments [Member] | Other Midstream [Member] | (Gains) losses on derivatives, net [Member] | Commodity Contract [Member]
Segment Reporting Information [Line Items]
Net cash from settlement of commodity derivatives		0		0	0		0
Operating Segments [Member] | Other Midstream [Member] | Gathering, processing, and marketing sales [Member] | Commodity Contract [Member] | Not Designated as Hedging Instrument [Member]
Segment Reporting Information [Line Items]
Total (gains) losses on derivatives, net included in marketing revenue, less net cash from settlement		0			0		0
Operating Segments [Member] | Other Midstream [Member] | Excluding Gains Losses On Divestitures Net [Member]
Segment Reporting Information [Line Items]
Total revenues and other	[1]	128		103	291		279
Operating Segments [Member] | Other Midstream [Member] | Excluding Certain Items [Member]
Segment Reporting Information [Line Items]
Operating costs and expenses	[2]	55		62	134		168
Operating Segments [Member] | Other Midstream [Member] | Excluding Certain Other Nonoperating Items [Member]
Segment Reporting Information [Line Items]
Other (income) expense, net		0	[3]	0	0	[3]	0
Other and Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Sales Revenues		32			154
Other		23		28	63		77
Total revenues and other		(184)			(470)
Net income (loss) attributable to noncontrolling interests		64		58	105		182
Total expenses and other		213		93	746		318
Consolidated Adjusted EBITDAX		(394)		(216)	(1,206)		(685)
Other and Intersegment Eliminations [Member] | (Gains) losses on derivatives, net [Member] | Commodity Contract [Member]
Segment Reporting Information [Line Items]
Net cash from settlement of commodity derivatives		199		(16)	437		(23)
Other and Intersegment Eliminations [Member] | Gathering, processing, and marketing sales [Member] | Commodity Contract [Member] | Not Designated as Hedging Instrument [Member]
Segment Reporting Information [Line Items]
Total (gains) losses on derivatives, net included in marketing revenue, less net cash from settlement		0			7		(2)
Other and Intersegment Eliminations [Member] | Excluding Gains Losses On Divestitures Net [Member]
Segment Reporting Information [Line Items]
Total revenues and other	[1]	(181)		(123)	(467)		(365)
Other and Intersegment Eliminations [Member] | Excluding Certain Items [Member]
Segment Reporting Information [Line Items]
Operating costs and expenses	[2]	(67)		49	195		135
Other and Intersegment Eliminations [Member] | Excluding Certain Other Nonoperating Items [Member]
Segment Reporting Information [Line Items]
Other (income) expense, net		17	[3]	2	9	[3]	24
Oil and Gas [Member]
Segment Reporting Information [Line Items]
Sales Revenues		3,607		2,610	9,801		7,927
Oil and Gas [Member] | Operating Segments [Member] | Exploration and Production [Member]
Segment Reporting Information [Line Items]
Sales Revenues		3,161		2,097	8,589		6,500
Oil and Gas [Member] | Operating Segments [Member] | Exploration and Production [Member] | Intersegment Revenues [Member]
Segment Reporting Information [Line Items]
Sales Revenues		25		4	49		10
Oil and Gas [Member] | Operating Segments [Member] | WES Midstream [Member]
Segment Reporting Information [Line Items]
Sales Revenues		394		445	1,063		1,213
Oil and Gas [Member] | Operating Segments [Member] | WES Midstream [Member] | Intersegment Revenues [Member]
Segment Reporting Information [Line Items]
Sales Revenues		114		119	369		387
Oil and Gas [Member] | Operating Segments [Member] | Other Midstream [Member]
Segment Reporting Information [Line Items]
Sales Revenues		39		53	73		134
Oil and Gas [Member] | Operating Segments [Member] | Other Midstream [Member] | Intersegment Revenues [Member]
Segment Reporting Information [Line Items]
Sales Revenues		78		43	188		125
Oil and Gas [Member] | Other and Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Sales Revenues		13		15	76		80
Oil and Gas [Member] | Other and Intersegment Eliminations [Member] | Intersegment Revenues [Member]
Segment Reporting Information [Line Items]
Sales Revenues		$ (217)		$ (166)	$ (606)		$ (522)
[1]	Total revenues and other excludes gains (losses) on divestitures, net since these gains and losses are excluded from Adjusted EBITDAX.
[2]	Operating costs and expenses excludes exploration expense, DD&A, impairments, restructuring charges, and certain other operating expenses since these expenses are excluded from Adjusted EBITDAX
[3]	Other (income) expense, net excludes restructuring charges since these expenses are excluded from Adjusted EBITDAX.