Anadarko Petroleum 10-Q 4 May 15 2015 Q1 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	3 Months Ended
	Mar. 31, 2015	Apr. 27, 2015
Document And Entity Information [Abstract]
Trading Symbol	APC
Entity Registrant Name	ANADARKO PETROLEUM CORP
Entity Central Index Key	773910
Document Type	10-Q
Document Period End Date	31-Mar-15
Amendment Flag	FALSE
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	-19
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		507,935,794

CONSOLIDATED_STATEMENTS_OF_INC

CONSOLIDATED STATEMENTS OF INCOME (USD $)	3 Months Ended
In Millions, except Per Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Revenues and Other
Natural-gas sales	$641	$1,217
Oil and condensate sales	1,419	2,424
Natural-gas liquids sales	232	386
Gathering, processing, and marketing sales	293	311
Gains (losses) on divestitures and other, net	-264	1,506
Total	2,321	5,844
Costs and Expenses
Oil and gas operating	296	313
Oil and gas transportation and other	361	266
Exploration	1,083	299
Gathering, processing, and marketing	254	252
General and administrative	310	298
Depreciation, depletion, and amortization	1,256	1,124
Other taxes	182	314
Impairments	2,783	3
Total	6,529	2,869
Operating Income (Loss)	-4,208	2,975
Other (Income) Expense
Interest expense	216	183
(Gains) losses on derivatives, net	152	461
Other (income) expense, net	47	1
Total	420	4,937
Income (Loss) Before Income Taxes	-4,628	-1,962
Income tax expense (benefit)	-1,392	664
Net Income (Loss)	-3,236	-2,626
Net income attributable to noncontrolling interests	32	43
Net Income (Loss) Attributable to Common Stockholders	-3,268	-2,669
Per Common Share
Net income (loss) attributable to common stockholders—basic	($6.45)	($5.30)
Net income (loss) attributable to common stockholders—diluted	($6.45)	($5.30)
Average Number of Common Shares Outstanding—Basic	507	504
Average Number of Common Shares Outstanding—Diluted	507	504
Dividends (per common share)	$0.27	$0.18
Commodity Contract and Interest Rate Swap [Member]
Other (Income) Expense
(Gains) losses on derivatives, net	152	453
Deepwater Horizon [Member] | Pending Litigation [Member]
Costs and Expenses
Litigation-related contingent loss	4	0
Tronox Litigation [Member] | Judicial Ruling [Member]
Costs and Expenses
Litigation-related contingent loss	$5	$4,300

CONSOLIDATED_STATEMENTS_OF_COM

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Statement of Comprehensive Income [Abstract]
Net Income (Loss)	($3,236)	($2,626)
Adjustments for derivative instruments
Reclassification of previously deferred derivative losses to (gains) losses on derivatives, net	2	2
Income taxes on reclassification of previously deferred derivative losses to (gains) losses on derivatives, net	-1	-1
Total adjustments for derivative instruments, net of taxes	1	1
Adjustments for pension and other postretirement plans
Amortization of net actuarial (gain) loss to general and administrative expense	13	7
Income taxes on amortization of net actuarial (gain) loss to general and administrative expense	-4	-2
Total adjustments for pension and other postretirement plans, net of taxes	9	5
Total	10	6
Comprehensive Income (Loss)	-3,226	-2,620
Comprehensive income attributable to noncontrolling interests	32	43
Comprehensive Income (Loss) Attributable to Common Stockholders	($3,258)	($2,663)

CONSOLIDATED_BALANCE_SHEETS

CONSOLIDATED BALANCE SHEETS (USD $)	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014
In Millions, unless otherwise specified
Current Assets
Cash and cash equivalents	$2,308	$7,369	$5,924
Accounts receivable (net of allowance of $9 million and $7 million)
Customers	1,025	1,118
Others	1,149	1,409
Other current assets	683	1,325
Total	5,165	11,221
Properties and Equipment
Cost	76,040	75,107
Less accumulated depreciation, depletion, and amortization	37,770	33,518
Net properties and equipment	38,270	41,589
Other Assets	2,998	2,310
Goodwill and Other Intangible Assets	6,540	6,569
Total Assets	52,973	61,689
Current Liabilities
Accounts payable	3,252	3,683
Current asset retirement obligations	282	257
Accrued expenses	1,100	994
Short-term debt	500	0
Total	5,228	10,234
Long-term Debt	16,365	15,092
Other Long-term Liabilities
Deferred income taxes	7,521	9,249
Asset retirement obligations	1,803	1,796
Other	3,122	3,000
Total	12,446	14,045
Stockholders' equity
Common stock, par value $0.10 per share (1.0 billion shares authorized, 527.6 million and 525.9 million shares issued)	52	52
Paid-in capital	9,045	9,005
Retained earnings	8,718	12,125
Treasury stock (19.7 million and 19.3 million shares)	-976	-940
Accumulated other comprehensive income (loss)	-507	-517
Total Stockholders’ Equity	16,332	19,725
Noncontrolling interests	2,602	2,593
Total Equity	18,934	22,318
Total Liabilities and Equity	52,973	61,689
Pending Litigation [Member] | Deepwater Horizon [Member]
Current Liabilities
Litigation-related contingent liability	94	90
Judicial Ruling [Member] | Tronox Litigation [Member]
Current Liabilities
Litigation-related contingent liability	$0	$5,210	$5,150

CONSOLIDATED_BALANCE_SHEETS_Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Millions, except Share data, unless otherwise specified
Statement of Financial Position [Abstract]
Allowance for uncollectible accounts	$9	$7
Common stock, par value	$0.10	$0.10
Common stock, shares authorized	1,000,000,000	1,000,000,000
Common stock, shares issued	527,600,000	525,900,000
Treasury stock, shares	19,700,000	19,300,000

CONSOLIDATED_STATEMENT_OF_EQUI

CONSOLIDATED STATEMENT OF EQUITY (USD $)	Total	Common Stock [Member]	Paid-in Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Noncontrolling Interests [Member]
In Millions
Balance at Dec. 31, 2014	$22,318	$52	$9,005	$12,125	($940)	($517)	$2,593
Net income (loss)	-3,236			-3,268			32
Common stock issued	50		50
Dividends—common stock	-139			-139
Repurchase of common stock	-36				-36
Subsidiary equity transactions	34		-10				44
Distributions to noncontrolling interest owners	-67						-67
Reclassification of previously deferred derivative losses to (gains) losses on derivatives, net	1					1
Adjustments for pension and other postretirement plans	9					9
Balance at Mar. 31, 2015	$18,934	$52	$9,045	$8,718	($976)	($507)	$2,602

CONSOLIDATED_STATEMENTS_OF_CAS

CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Cash Flows from Operating Activities
Net income (loss)	($3,236)	($2,626)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities
Depreciation, depletion, and amortization	1,256	1,124
Deferred income taxes	-1,198	46
Dry hole expense and impairments of unproved properties	1,009	198
Impairments	2,783	3
(Gains) losses on divestitures, net	334	-1,459
Total (gains) losses on derivatives, net	152	461
Operating portion of net cash received (paid) in settlement of derivative instruments	91	-98
Other	45	54
Statement [Line Items]
(Increase) decrease in accounts receivable	357	-266
Increase (decrease) in accounts payable and accrued expenses	-283	-63
Other items—net	-608	55
Net cash provided by (used in) operating activities	-4,504	1,729
Cash Flows from Investing Activities
Additions to properties and equipment and dry hole costs	-1,957	-2,501
Acquisition of businesses	0	-4
Divestitures of properties and equipment and other assets	22	3,257
Other—net	10	-170
Net cash provided by (used in) investing activities	-1,925	582
Cash Flows from Financing Activities
Borrowings, net of issuance costs	4,583	918
Repayments of debt	-2,830	-930
Financing portion of net cash received (paid) for derivative instruments	-146	0
Increase (decrease) in outstanding checks	-39	97
Dividends paid	-139	-92
Repurchase of common stock	-36	-35
Issuance of common stock, including tax benefit on share-based compensation awards	12	13
Sale of subsidiary units	31	18
Distributions to noncontrolling interest owners	-67	-51
Net cash provided by (used in) financing activities	1,369	-62
Effect of Exchange Rate Changes on Cash	-1	-23
Net Increase (Decrease) in Cash and Cash Equivalents	-5,061	2,226
Cash and Cash Equivalents at Beginning of Period	7,369	3,698
Cash and Cash Equivalents at End of Period	2,308	5,924
Deepwater Horizon [Member] | Pending Litigation [Member]
Statement [Line Items]
Litigation-related contingent costs	4	0
Tronox Litigation [Member] | Judicial Ruling [Member]
Statement [Line Items]
Litigation-related contingent costs	($5,210)	$4,300

Summary_of_Significant_Account

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2015
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 marketing of natural gas, oil, condensate, natural gas liquids (NGLs), and anticipated production of liquefied natural gas (LNG). In addition, the Company engages in the gathering, processing, treating, and transporting of natural gas, oil, and NGLs. The Company also participates in the hard-minerals business through royalty arrangements. Unless the context otherwise requires, the terms “Anadarko” and “Company” refer to Anadarko Petroleum Corporation and its consolidated subsidiaries.
	Basis of Presentation  The information furnished herein reflects 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.
	Use of Estimates  The preparation of financial statements in accordance with generally accepted accounting principles in the United States requires management to make informed judgments and estimates that affect the reported amounts of assets, liabilities, revenues, and expenses. Management evaluates its estimates and related assumptions regularly, including those related to proved reserves; the value of properties and equipment; goodwill; intangible assets; asset retirement obligations; litigation liabilities; environmental liabilities; pension assets, liabilities, and costs; income taxes; and fair values. Changes in facts and circumstances or additional information may result in revised estimates, and actual results may differ from these estimates.
	Recently Issued Accounting Standards  The Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2015-02, Consolidation—Amendments to the Consolidation Analysis. This ASU will simplify existing requirements by reducing the number of consolidation models and placing more emphasis on risk of loss when determining a controlling financial interest. The provisions will affect how limited partnerships and similar entities are assessed for consolidation, including the elimination of the presumption that a general partner should consolidate a limited partnership. This ASU is effective for annual and interim periods beginning in 2016 and is required to be adopted using a retrospective or modified retrospective approach, with early adoption permitted. The Company is evaluating the impact of the adoption of this ASU on its consolidated financial statements.
	The FASB issued ASU 2014-09, Revenue from Contracts with Customers. This ASU supersedes the revenue recognition requirements in Topic 605, Revenue Recognition, and industry-specific guidance in Subtopic 932-605, Extractive Activities—Oil and Gas—Revenue Recognition, and 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. This ASU is effective for annual and interim periods beginning in 2017 and is required to be adopted using one of two retrospective application methods, with no early adoption permitted. The Company is evaluating the impact of the adoption of this ASU on its consolidated financial statements.

Acquisitions_Divestitures_and_

Acquisitions, Divestitures, and Assets Held for Sale	3 Months Ended
	Mar. 31, 2015
Property, Plant and Equipment [Abstract]
Acquisitions, Divestitures, and Assets Held for Sale	2. Acquisitions, Divestitures, and Assets Held for Sale
	In November 2014, Western Gas Partners, LP (WES) acquired Nuevo Midstream, LLC (Nuevo) for $1.554 billion. Following the acquisition, WES changed the name of Nuevo to Delaware Basin Midstream, LLC (DBM). The acquisition constitutes a business combination and was accounted for using the acquisition method of accounting. The fair-value measurements of the assets acquired and liabilities assumed at the acquisition date were still preliminary as of March 31, 2015, pending final review of support related to the acquired entity’s assets. There were no material changes to the fair value of assets acquired and liabilities assumed from the amounts included on the Company’s Consolidated Balance Sheet at December 31, 2014.
	2. Acquisitions, Divestitures, and Assets Held for Sale (Continued)
	For the three months ended March 31, 2015, the Company recognized net losses on divestitures of $334 million related to assets included in the oil and gas exploration and production reporting segment. During the first quarter of 2015, certain U.S. onshore assets in the Rocky Mountains Region (Rockies) satisfied criteria to be considered held for sale. These assets were remeasured to their current fair value using a market approach and Level 2 fair-value measurement, and the Company recognized a loss of $340 million. Gains and losses on assets held for sale are included in gains (losses) on divestitures and other, net in the Company’s Consolidated Statements of Income. At March 31, 2015, the Company’s Consolidated Balance Sheet included current assets of $29 million, long-term assets of $743 million, current liabilities of $17 million, and long-term liabilities of $78 million associated with assets held for sale. The sale of these assets closed in April 2015 for proceeds of $703 million.

Inventories

Inventories	3 Months Ended
	Mar. 31, 2015
Energy Related Inventory [Abstract]
Inventories	3. Inventories
	The following summarizes the major classes of inventories included in other current assets:
	millions	March 31,		December 31,
		2015		2014
	Oil	$	97	$	133
	Natural gas	3		27
	NGLs	70		83
	Total inventories	$	170	$	243

Impairments

Impairments	3 Months Ended
	Mar. 31, 2015
Asset Impairment Charges [Abstract]
Impairments	4. Impairments
	The following summarizes impairments of proved properties and the related post-impairment fair values by segment:
		Three Months Ended
	millions	Impairment		Fair Value (1)
	March 31, 2015
	Oil and gas exploration and production
	Long-lived assets held for use
	U.S. onshore properties	$	2,307	$	1,299
	Midstream
	Long-lived assets held for use	476		206
	Total	$	2,783	$	1,505
	March 31, 2014
	Oil and gas exploration and production
	Cost-method investment (2)	$	1	$	32
	Midstream
	Long-lived assets held for use	2		—
	Total	$	3	$	32
	__________________________________________________________________
	(1)	Measured using the income approach and Level 3 inputs.
	(2)	Represents the after-tax net investment.
	Impairments during the first quarter of 2015 were primarily related to the Company’s Greater Natural Buttes oil and gas and midstream properties in the Rockies, which were impaired due to lower commodity prices. Impairments of proved properties are included in impairment expense in the Company’s Consolidated Statements of Income. In addition to the proved property impairments above, the Company also recognized a $935 million impairment of unproved Greater Natural Buttes properties as a result of lower commodity prices during the first quarter of 2015. Impairments of unproved properties are included in exploration expense in the Company’s Consolidated Statements of Income.

Suspended_Exploratory_Well_Cos

Suspended Exploratory Well Costs	3 Months Ended
	Mar. 31, 2015
Capitalized Exploratory Well Costs [Abstract]
Suspended Exploratory Well Costs	5. Suspended Exploratory Well Costs
	The Company’s suspended exploratory well costs were $1.6 billion at March 31, 2015, and $1.5 billion at December 31, 2014. Projects with suspended exploratory well costs are those identified by management as exhibiting sufficient quantities of hydrocarbons to justify potential development and where management is actively pursuing efforts to assess whether reserves can be attributed to these projects. 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 three months ended March 31, 2015, no exploratory well costs previously capitalized as suspended exploratory well costs for greater than one year at December 31, 2014, were charged to dry hole expense.

Noncontrolling_Interests

Noncontrolling Interests	3 Months Ended
	Mar. 31, 2015
Noncontrolling Interest Items [Abstract]
Noncontrolling Interests	6. Noncontrolling Interests
	Western Gas Equity Partners, LP (WGP) is a publicly traded consolidated subsidiary that owns partnership interests in WES. At March 31, 2015, Anadarko’s ownership interest in WGP consisted of an 88.3% limited partner interest and the entire non-economic general partner interest. The remaining 11.7% limited partner interest in WGP was owned by the public.
	WES, a publicly traded consolidated subsidiary, is a limited partnership that acquires, owns, develops, and operates midstream assets. During the three months ended March 31, 2015, WES issued 480 thousand common units to the public under its continuous offering program, raising net proceeds of $31 million. In 2014, WES issued 11 million Class C units to Anadarko to partially fund the acquisition of DBM. These Class C units receive distributions in the form of additional Class C units until the end of 2017 unless WES elects to convert the units earlier or Anadarko extends the conversion date. During the three months ended March 31, 2015, WES distributed 46 thousand Class C units to Anadarko. At March 31, 2015, WGP’s ownership interest in WES consisted of a 34.8% limited partner interest, the entire 1.8% general partner interest, and all of the WES incentive distribution rights. At March 31, 2015, Anadarko also owned an 8.3% limited partner interest in WES through other subsidiaries’ ownership of common and Class C units. The remaining 55.1% limited partner interest in WES was owned by the public.

Derivative_Instruments

Derivative Instruments	3 Months Ended
	Mar. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments	7. 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 Henry Hub, Louisiana, for natural gas and Cushing, Oklahoma, or Sullom Voe, Scotland, for oil. 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 (Marketing and Trading Derivative Activities).
	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 increases (decreases) when interest rates increase (decrease).
	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. See Note 10—Accumulated Other Comprehensive Income (Loss).
	7. Derivative Instruments (Continued)
	Oil and Natural-Gas Production/Processing Derivative Activities  The natural-gas prices listed below are New York Mercantile Exchange (NYMEX) Henry Hub prices. The following is a summary of the Company’s derivative instruments related to natural-gas production/processing derivative activities at March 31, 2015:
		2015
		Settlement
	Natural Gas
	Three-Way Collars (thousand MMBtu/d)	635
	Average price per MMBtu
	Ceiling sold price (call)	$	4.76
	Floor purchased price (put)	$	3.75
	Floor sold price (put)	$	2.75
	Extendable Fixed-Price Contracts (thousand MMBtu/d) (1)	170
	Average price per MMBtu	$	4.17
	__________________________________________________________________
	(1)	The extendable fixed-price contracts have a contract term of January 2015 to December 2015 with an option for the counterparty to extend the contract term to December 2016 at the same price.
	MMBtu—million British thermal units
	MMBtu/d—million British thermal units per day
	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.
	Marketing and Trading Derivative Activities  The Company had financial derivative transactions with notional volumes of natural gas totaling 3 billion cubic feet (Bcf) at March 31, 2015, and 6 Bcf at December 31, 2014, that were entered into to mitigate commodity-price risk related to fixed-price purchase and sales contracts and storage activity.
	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 London Interbank Offered Rate (LIBOR). These swap instruments include a provision that requires both the termination of the swaps and cash settlement in full at the start of the reference period.
	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 or collateralization related to these extended interest-rate derivatives are classified as cash flows from financing activities.
	The Company had the following outstanding interest-rate swaps at March 31, 2015:
	millions except percentages					Reference Period			Weighted-Average
	Notional Principal Amount					Start		End	Interest Rate
	$	50				Sep-16		Sep-26	5.91%
	$	1,850				Sep-16		Sep-46	6.06%
	7. 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		March 31,				December 31,			March 31,				December 31,
	Balance Sheet Classification		2015				2014			2015				2014
	Commodity derivatives
	Other current assets		$	351			$	421		$	(86	)		$	(118	)
	Other assets		35				1			—				—
	Accrued expenses		65				71			(117		)		(114		)
	Other liabilities		—				—			(31		)		(6		)
			451				493			(234		)		(238		)
	Interest-rate derivatives
	Other liabilities		—				—			(1,422		)		(1,217		)
	Total derivatives		$	451			$	493		$	(1,656	)		$	(1,455	)
	Effect of Derivative Instruments—Statement of Income  The following summarizes gains and losses related to derivative instruments:
	millions		Three Months Ended
			March 31,
	Classification of (Gain) Loss Recognized		2015				2014
	Commodity derivatives
	Gathering, processing, and marketing sales (1)		$	—			$	8
	(Gains) losses on derivatives, net		(53		)		215
	Interest-rate derivatives
	(Gains) losses on derivatives, net		205				238
	Total (gains) losses on derivatives, net		$	152			$	461
	__________________________________________________________________
	(1)	Represents the effect of Marketing and Trading Derivative Activities.
	Credit-Risk Considerations  The financial integrity of exchange-traded contracts, which are subject to nominal credit risk, is assured by NYMEX or IntercontinentalExchange, Inc. 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 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. At March 31, 2015, $237 million of the Company’s $1.656 billion gross derivative liability balance, and at December 31, 2014, $289 million of the Company’s $1.455 billion gross derivative liability balance would have been eligible for setoff against the Company’s gross derivative asset balance in the event of default. Other than in the event of default, the Company does not net settle across derivative types.
	7. Derivative Instruments (Continued)
	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 valuation versus negotiated credit thresholds. These credit thresholds may also require full or partial collateralization or immediate settlement of the Company’s obligations if certain credit-risk-related provisions are triggered, such as if the Company’s credit rating from major credit rating agencies declines to below investment grade. The aggregate fair value of derivative instruments with credit-risk-related contingent features for which a net liability position existed was $1.2 billion (net of collateral) at March 31, 2015, and $97 million (net of collateral) at December 31, 2014. The increase is primarily a result of additional derivative counterparties no longer maintaining secured positions under the Company’s credit facilities and, therefore, the derivative instruments are now subject to credit-risk-related provisions. For information on the Company’s revolving credit facilities, see Note 8—Debt and Interest Expense—Anadarko Revolving Credit Facilities and Commercial Paper Program.
	Fair Value  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
	March 31, 2015	Level 1				Level 2			Level 3				Netting (1)				Collateral			Total
	Assets
Commodity derivatives
Financial institutions	$	—			$	431		$	—			$	(151	)		$	(4	)	$	276
Other counterparties	—				20			—				—				—			20
Total derivative assets	$	—			$	451		$	—			$	(151	)		$	(4	)	$	296
Liabilities
Commodity derivatives
Financial institutions	$	—			$	(183	)	$	—			$	151			$	1		$	(31	)
Other counterparties	—				(51		)	—				—				—			(51		)
Interest-rate derivatives	—				(1,422		)	—				—				169			(1,253		)
Total derivative liabilities	$	—			$	(1,656	)	$	—			$	151			$	170		$	(1,335	)
December 31, 2014
Assets
Commodity derivatives
Financial institutions	$	—			$	471		$	—			$	(187	)		$	(13	)	$	271
Other counterparties	—				22			—				(2		)		—			20
Total derivative assets	$	—			$	493		$	—			$	(189	)		$	(13	)	$	291
Liabilities
Commodity derivatives
Financial institutions	$	—			$	(234	)	$	—			$	187			$	—		$	(47	)
Other counterparties	—				(4		)	—				2				—			(2		)
Interest-rate derivatives	—				(1,217		)	—				—				23			(1,194		)
Total derivative liabilities	$	—			$	(1,455	)	$	—			$	189			$	23		$	(1,243	)
__________________________________________________________________
(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_and_Interest_Expense

Debt and Interest Expense	3 Months Ended
	Mar. 31, 2015
Debt Disclosure [Abstract]
Debt and Interest Expense	8. Debt and Interest Expense
	Debt  The Company’s outstanding debt is senior unsecured. The following summarizes the Company’s outstanding debt:
	millions	March 31,			December 31,
		2015			2014
	Total debt at face value	$	18,450		$	16,687
	Net unamortized discounts and premiums (1)	(1,606		)	(1,616		)
	Total borrowings	$	16,844		$	15,071
	Capital lease obligation	21			21
	Less short-term debt	500			—
	Total long-term debt	$	16,365		$	15,092
	__________________________________________________________________
	(1)	Unamortized discounts and premiums are amortized over the term of the related debt.
	Anadarko’s Zero-Coupon Senior Notes due 2036 (Zero Coupons) can be put to the Company in October of each year, in whole or in part, for the then-accreted value, which will be $796 million at the next put date in October 2015. Anadarko’s Zero Coupons are classified as long-term debt on the Company’s Consolidated Balance Sheets, as the Company has the ability and intent to refinance these obligations using long-term debt.
	Fair Value  The Company uses a market approach to determine 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 variable interest rates are reflective of market rates. The estimated fair value of the Company’s total borrowings was $19.3 billion at March 31, 2015, and $17.4 billion at December 31, 2014.
	Debt Activity  The following summarizes the Company’s debt activity during the three months ended March 31, 2015:
		Carrying
	millions	Value			Description
	Balance at December 31, 2014	$	15,071
	Borrowings	1,500			$5.0 billion revolving credit facility
		1,800			364-Day Facility
		140			WES revolving credit facility
		1,153			Commercial paper notes
	Repayments	(1,500		)	$5.0 billion revolving credit facility
		(1,300		)	364-Day Facility
		(30		)	WES revolving credit facility
	Other, net	10			Amortization of debt discounts and premiums
	Balance at March 31, 2015	$	16,844
	8. Debt and Interest Expense (Continued)
	Anadarko Revolving Credit Facilities and Commercial Paper Program  In January 2015, upon satisfaction of certain conditions, including the settlement payment related to the Tronox Adversary Proceeding, the Company’s $5.0 billion senior secured revolving credit facility was replaced by a $3.0 billion five-year senior unsecured revolving credit facility (Five-Year Facility), which is expandable to $4.0 billion, and a $2.0 billion 364-day senior unsecured revolving credit facility (364-Day Facility). For additional information, see Note 11—Contingencies—Tronox Litigation.
	Borrowings under the Five-Year and 364-Day Facilities generally bear interest under one of two rate options, at Anadarko’s election, using either LIBOR (or Euro Interbank Offered Rate in the case of borrowings under the Five-Year Facility denominated in Euro) or an alternate base rate, in each case plus an applicable margin ranging from 0.00% to 1.65% for the Five-Year Facility and 0.00% to 1.675% for the 364-Day Facility. The applicable margin will vary depending on Anadarko’s credit ratings.
	The Five-Year and 364-Day Facilities contain certain customary affirmative and negative covenants, including a financial covenant requiring maintenance of a consolidated indebtedness to total capitalization ratio of no greater than 65% and limitations on certain secured indebtedness, sale-and-leaseback transactions, and mergers and other fundamental changes. At March 31, 2015, the Company was in compliance with all covenants contained in its Five-Year and 364-Day Facilities.
	At March 31, 2015, the Company had no outstanding borrowings under the Five-Year Facility and had $500 million of outstanding borrowings under its 364-Day Facility at an interest rate of 1.29%. The Company had available borrowing capacity of $1.5 billion under its 364-Day Facility.
	During the first quarter of 2015, the Company initiated a commercial paper program, which allows a maximum of $3.0 billion of unsecured commercial paper notes and is supported by the Company’s Five-Year Facility. The maturities of the commercial paper notes vary, but may not exceed 397 days. The commercial paper notes are sold under customary terms in the commercial paper market and are issued either at a discounted price to their principal face value or will bear interest at varying interest rates on a fixed or floating basis. Such discounted price or interest amounts are dependent on market conditions and the ratings assigned to the commercial paper program by credit rating agencies at the time of issuance of the commercial paper notes. At March 31, 2015, the Company had $1.2 billion of commercial paper notes outstanding at a weighted-average interest rate of 0.67%. The Company classified the outstanding commercial paper notes as long-term debt on the Company’s Consolidated Balance Sheet, as the Company currently intends to refinance these obligations at maturity with additional commercial paper notes supported by the Company’s Five-Year Facility.
	WES Borrowings  At March 31, 2015, WES was in compliance with all covenants contained in its five-year $1.2 billion senior unsecured revolving credit facility maturing in February 2019 (RCF), which is expandable to $1.5 billion. At March 31, 2015, WES had outstanding borrowings under its RCF of $620 million at an interest rate of 1.48%, had outstanding letters of credit of $13 million, and had available borrowing capacity of $567 million.
	Interest Expense  The following summarizes interest expense:
		Three Months Ended
		March 31,
	millions	2015			2014
	Debt and other	$	254		$	240
	Capitalized interest	(38		)	(57		)
	Total interest expense	$	216		$	183

Stockholders_Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2015
Stockholders' Equity Note [Abstract]
Stockholders' Equity	9. Stockholders’ Equity
	The following provides a reconciliation between basic and diluted earnings per share attributable to common stockholders:
		Three Months Ended
		March 31,
	millions except per-share amounts	2015			2014
	Net income (loss)
	Net income (loss) attributable to common stockholders	$	(3,268	)	$	(2,669	)
	Less distributions on participating securities	1			—
	Basic	$	(3,269	)	$	(2,669	)
	Diluted	$	(3,269	)	$	(2,669	)
	Shares
	Average number of common shares outstanding—basic	507			504
	Average number of common shares outstanding—diluted	507			504
	Excluded (1)	11			11
	Net income (loss) per common share
	Basic	$	(6.45	)	$	(5.30	)
	Diluted	$	(6.45	)	$	(5.30	)
	Dividends per common share	$	0.27		$	0.18
	__________________________________________________________________
	(1)	Inclusion of certain shares would have had an anti-dilutive effect.

Accumulated_Other_Comprehensiv

Accumulated Other Comprehensive Income (Loss)	3 Months Ended
	Mar. 31, 2015
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Accumulated Other Comprehensive Income (Loss)	10. Accumulated Other Comprehensive Income (Loss)
	The following summarizes the after-tax changes in the balances of accumulated other comprehensive income (loss):
	millions	Interest-rate			Pension and Other Postretirement			Total
		Derivatives			Plans
		Previously
		Subject to Hedge
		Accounting
	Balance at December 31, 2014	$	(48	)	$	(469	)	$	(517	)
	Reclassifications to Consolidated Statement of Income	1			9			10
	Balance at March 31, 2015	$	(47	)	$	(460	)	$	(507	)

Contingencies

Contingencies	3 Months Ended
	Mar. 31, 2015
Contingencies Disclosure [Abstract]
Contingencies	11. Contingencies
	Litigation  The Company is a defendant in a number of lawsuits, is involved in governmental proceedings, and is subject to regulatory controls arising in the ordinary course of business, including, but not limited to, personal injury claims; property damage claims; title disputes; tax disputes; royalty claims; contract claims; contamination claims relating to oil and gas production, transportation, and processing; and environmental claims, including claims involving assets owned by acquired companies and claims involving assets previously sold to third parties and no longer a part of the Company’s current operations. Anadarko is also subject to various environmental-remediation and reclamation obligations arising from federal, state, and local laws and regulations. While the ultimate outcome and impact on the Company cannot be predicted with certainty, after consideration of recorded expense and liability accruals, management believes that the resolution of pending proceedings will not have a material adverse effect on the Company’s financial condition, results of operations, or cash flows.
	The following is a discussion of any material developments in previously reported contingencies and 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, 2014.
	Tronox Litigation  On April 3, 2014, Anadarko and Kerr-McGee Corporation and certain of its subsidiaries entered into a settlement agreement to resolve all claims asserted by Tronox Incorporated (Tronox) and certain of its affiliates, including claims for actual and constructive fraudulent conveyance (Adversary Proceeding), for $5.15 billion. In addition, the Company agreed to pay interest on that amount from April 3, 2014, through the payment of the settlement. In January 2015, the Company paid $5.2 billion after the settlement agreement became effective. For additional disclosure of the Tronox Adversary Proceeding, see Note 17—Contingencies—Tronox Litigation in the Notes to Consolidated Financial Statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2014.
	Anadarko recognized Tronox-related contingent losses of $850 million in the fourth quarter of 2013 and $4.3 billion in the first quarter of 2014. In addition, Anadarko recognized settlement-related interest expense, included in Tronox-related contingent loss in the Company’s Consolidated Statement of Income, of $60 million during the year ended December 31, 2014, and $5 million during the three months ended March 31, 2015. For information on the tax effects of the settlement agreement, see Note 12—Income Taxes.
	Deepwater Horizon Events  In April 2010, the Macondo well in the Gulf of Mexico blew out and an explosion occurred on the Deepwater Horizon drilling rig, resulting in an oil spill. The well was operated by BP Exploration and Production Inc. (BP) and Anadarko held a 25% nonoperated interest. In October 2011, the Company and BP entered into a settlement agreement relating to the Deepwater Horizon events (Settlement Agreement). Pursuant to the Settlement Agreement, the Company is fully indemnified by BP against all claims and damages arising under the Oil Pollution Act of 1990 (OPA), claims for natural resource damages (NRD) and assessment costs, and any claims arising under the Operating Agreement with BP. This indemnification is guaranteed by BP Corporation North America Inc. (BPCNA) and, in the event that the net worth of BPCNA declines below an agreed-upon amount, BP p.l.c. has agreed to become the sole guarantor. Under the Settlement Agreement, BP does not indemnify the Company against penalties and fines, punitive damages, shareholder derivative or securities laws claims, or certain other claims. The Company has not recorded a liability for any costs that are subject to indemnification by BP. For additional disclosure of the Deepwater Horizon events, the Company’s Settlement Agreement with BP, environmental claims under OPA, NRD claims, potential penalties and fines, and civil litigation, see Note 17—Contingencies—Deepwater Horizon Events in the Notes to Consolidated Financial Statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2014.
	Penalties and Fines  In December 2010, the U.S. Department of Justice (DOJ), on behalf of the United States, filed a civil lawsuit in the U.S. District Court for the Eastern District of Louisiana in New Orleans, Louisiana (Louisiana District Court) against several parties, including the Company, seeking an assessment of civil penalties under the Clean Water Act (CWA) in an amount to be determined by the Louisiana District Court. In February 2012, the Louisiana District Court entered a declaratory judgment that, as a partial owner of the Macondo well, Anadarko is liable for civil penalties under Section 311 of the CWA. The declaratory judgment, which was affirmed in June 2014 by the U.S. Court of Appeals for the Fifth Circuit (Fifth Circuit), addresses liability only, and does not address the amount of any civil penalty. In March 2015, Anadarko filed a petition for a writ of certiorari with the U.S. Supreme Court appealing the Fifth Circuit’s decision.
	11. Contingencies (Continued)
	Applicable accounting guidance requires the Company to accrue a liability if it is probable that a liability has been incurred and the amount of the liability can be reasonably estimated. The Louisiana District Court’s declaratory judgment in February 2012 satisfies the requirement that a liability arising from the future assessment of a civil penalty against Anadarko is probable. In an effort to resolve this matter, the Company made a settlement offer to the DOJ in July 2014 of $90 million and recorded a contingent liability for this amount at June 30, 2014. The Company subsequently engaged in further discussions regarding settlement, but the parties have not been able to reach agreement on either the amount of, or the terms and conditions governing, a settlement. The Company’s settlement offer of $90 million remains outstanding and the Company remains open to resolving the matter through settlement discussions. The Company believes that $90 million under a settlement scenario is a better estimate of loss at this time than any other amount. Based on the above accounting guidance, the Company’s contingent liability for CWA penalties and fines remains $90 million at March 31, 2015. However, the Company may ultimately incur a liability related to CWA penalties in excess of the current accrued liability.
	The actual amount of a CWA penalty is subject to uncertainty, including whether the Company will be able to reach a settlement with the DOJ or will await the Louisiana District Court’s opinion. The CWA sets forth subjective criteria to be considered by the court in assessing the magnitude of any CWA penalty, including the degree of fault of the owner. For the Phase I and II trials (defined in Civil Litigation Damage Claims below) and again for the penalty phase trial in January 2015, the Louisiana District Court ruled that no evidence of Anadarko’s alleged culpability or fault could be presented. In addition, in its Phase I Findings of Fact and Conclusions of Law (Phase I Findings and Conclusions), the Louisiana District Court did not allocate any fault to Anadarko. Given the subjective nature of the CWA criteria used to determine penalty assessments and the Louisiana District Court’s prior rulings related to culpability and allocation of fault, the Company currently cannot reasonably estimate the amount of any such penalty to be assessed or determine a reasonable range of potential loss if the matter is resolved by the Louisiana District Court following trial. However, given the Company’s lack of direct operational involvement in the event, the Louisiana District Court’s rulings excluding any evidence of Anadarko’s alleged culpability or fault, the Phase I Findings and Conclusions that did not allocate any fault to Anadarko, and the subjective criteria of the CWA, the Company believes that any CWA penalties assessed to it will not materially impact the Company’s financial condition, results of operations, or cash flows.
	Events or factors that could assist the Company in estimating the amount of settlement or potential civil penalty or a range of potential loss related to such penalty include (i) an assessment by the DOJ, (ii) a ruling by a court of competent jurisdiction, or (iii) substantive settlement negotiations between the Company and the DOJ.
	As discussed below, numerous Deepwater Horizon event-related civil lawsuits have been filed against BP and other parties, including the Company. Certain state and local governments appealed, or provided indication of a likely appeal of, the Louisiana District Court’s decision that only federal law, and not state law, applies to Deepwater Horizon event-related claims. If any appeal is successful, state and/or local laws and regulations could become sources of penalties or fines against the Company.
	Civil Litigation Damage Claims  Numerous Deepwater Horizon event-related civil lawsuits have been filed against BP and other parties, including the Company. This litigation has been consolidated into a federal Multidistrict Litigation (MDL) action pending before Judge Carl Barbier in the Louisiana District Court.
	The first phase of the trial in the MDL (Phase I) commenced in February 2013. The issues tried in Phase I included the cause of the blowout and all related events leading up to April 22, 2010, the date the Deepwater Horizon sank, as well as allocation of fault. In September 2014, the Louisiana District Court issued its Phase I Findings and Conclusions. The Louisiana District Court found that BP and BP America Production Company (BPAP), Transocean Ltd. (Transocean), and Halliburton Energy Services, Inc. (Halliburton), but not Anadarko, are each liable under general maritime law for the blowout, explosion, and oil spill. The court determined that BP’s and BPAP’s conduct was reckless and that both Transocean’s and Halliburton’s conduct was negligent. The Louisiana District Court apportioned 67% of the fault to BP and BPAP, 30% to Transocean, and 3% to Halliburton. No fault was allocated to Anadarko. The plaintiffs and BP have appealed the Phase I Findings and Conclusions.
	11. Contingencies (Continued)
	The second phase of trial (Phase II) began in September 2013. The issues tried in Phase II included spill-source control and quantification of the spill for the period from April 20, 2010, until the well was capped. In January 2015, the Louisiana District Court issued its Phase II Findings of Fact and Conclusions of Law (Phase II Findings and Conclusions). The Louisiana District Court found that, for purposes of calculating the maximum possible civil penalty under the CWA, 3.19 million barrels of oil were discharged into the Gulf of Mexico. The United States has appealed the Phase II Findings and Conclusions.
	The penalty phase of the trial began in January 2015. In March 2014, the Louisiana District Court ruled that no evidence of Anadarko’s alleged culpability or fault could be presented during the penalty phase trial. The parties rested their case in February 2015, post-trial briefing concluded in April 2015, and the matter is pending before the Louisiana District Court. The trial included Anadarko, BP, and the United States, and will assess findings and penalties under the CWA.
	Remaining Liability Outlook  It is possible that the Company may recognize additional Deepwater Horizon event-related liabilities for potential fines and penalties and certain other claims not covered by the indemnification provisions of the Settlement Agreement; however, the Company does not believe that any potential liability attributable to the foregoing items, individually or in the aggregate, will have a material impact on the Company’s financial condition, results of operations, or cash flows. This assessment takes into account certain qualitative factors, including the subjective and fault-based nature of CWA penalties, the Company’s indemnification by BP against certain damage claims as discussed above and BP’s creditworthiness.
	Although the Company is fully indemnified by BP against OPA damage claims, NRD claims and assessment costs, and certain other potential liabilities, the Company may be required to recognize a liability for these amounts in advance of or in connection with recognizing a receivable from BP for the related indemnity payment. In all circumstances, however, the Company expects that any additional indemnified liability that may be recognized by the Company will be subsequently recovered from BP itself or through the guarantees of BPCNA or BP p.l.c.
	The Company will continue to monitor the MDL and other legal proceedings discussed above, as well as federal investigations related to the Deepwater Horizon events. The Company cannot predict the nature of additional evidence that may be discovered during the course of legal proceedings or the timing of completion of any legal proceedings.
	Environmental Matters  Anadarko is also subject to various environmental-remediation and reclamation obligations arising from federal, state, and local laws and regulations. The Company continually monitors remediation and reclamation processes and adjusts its liability for these obligations as necessary.

Income_Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2015
Income Tax Disclosure [Abstract]
Income Taxes	12. Income Taxes
	The following summarizes income tax expense (benefit) and effective tax rates:
		Three Months Ended
		March 31,
	millions except percentages	2015			2014
	Income tax expense (benefit)	$	(1,392	)	$	664
	Effective tax rate	30		%	(34		)%
	The Company reported a loss before income taxes for the three months ended March 31, 2015 and 2014. As a result, items that ordinarily increase or decrease the tax rate will have the opposite effect.
	The decrease from the 35% U.S. federal statutory rate for the three months ended March 31, 2015, was primarily attributable to net changes in uncertain tax positions, Algerian exceptional profits taxes, and the tax impact from foreign operations. The decrease from the 35% U.S. federal statutory rate for the three months ended March 31, 2014, was primarily attributable to net changes in uncertain tax positions related to the settlement agreement associated with the Tronox Adversary Proceeding, Algerian exceptional profits taxes, and the tax impact from foreign operations.
	At March 31, 2015, the Company had recorded a $577 million tax benefit related to the Tronox settlement. This benefit was net of a $1.3 billion uncertain tax position due to the uncertainty related to the deductibility of the settlement payment. At March 31, 2015, $561 million of this net benefit was presented in other assets and the remainder was presented in deferred income taxes on the Company’s Consolidated Balance Sheet. The Company is a participant in the U.S. Internal Revenue Service’s (IRS) Compliance Assurance Process and has regular discussions with the IRS concerning the Company’s tax positions. Depending on the outcome of such discussions, it is reasonably possible that the amount of the uncertain tax position related to the settlement could change, perhaps materially. See Note 11—Contingencies—Tronox Litigation.
	At March 31, 2015, accrued expenses on the Company’s Consolidated Balance Sheet included $388 million of accrued income taxes.

Supplemental_Cash_Flow_Informa

Supplemental Cash Flow Information	3 Months Ended
	Mar. 31, 2015
Supplemental Cash Flow Information [Abstract]
Supplemental Cash Flow Information	13. Supplemental Cash Flow Information
	For the three months ended March 31, 2015, other items—net in the Company’s Consolidated Statements of Cash Flows includes a $561 million current tax benefit associated with the Tronox settlement. The following summarizes cash paid (received) for interest and income taxes, as well as non-cash investing and financing activities:
		Three Months Ended
		March 31,
	millions	2015			2014
	Cash paid (received)
	Interest, net of amounts capitalized (1)	$	1,532		$	265
	Income taxes, net of refunds	(5		)	598
	Non-cash investing activities
	Fair value of properties and equipment from non-cash transactions	$	54		$	—
	Asset retirement cost additions	63			47
	Accruals of property, plant, and equipment	1,061			1,544
	Net liabilities assumed (divested) in acquisitions and divestitures	19			(25		)
	Non-cash investing and financing activities
	Floating production, storage, and offloading vessel construction period obligation	$	18		$	34
	__________________________________________________________________
	(1)	Includes $1.2 billion of interest related to the Tronox settlement payment in 2015.

Segment_Information

Segment Information	3 Months Ended
	Mar. 31, 2015
Segment Reporting [Abstract]
Segment Information	14. Segment Information
	Anadarko’s business segments are separately managed due to distinct operational differences and unique technology, distribution, and marketing requirements. The Company’s three reporting segments are oil and gas exploration and production, midstream, and marketing. The oil and gas exploration and production segment explores for and produces natural gas, oil, condensate, and NGLs, and plans for the development and operation of the Company’s LNG project in Mozambique. The midstream segment engages in gathering, processing, treating, and transporting Anadarko and third-party oil, natural-gas, and NGLs production. The midstream reporting segment consists of two operating segments, WES and other midstream, which are aggregated into one reporting segment due to similar financial and operating characteristics. The marketing segment sells much of Anadarko’s oil, natural-gas, and NGLs production, as well as third-party purchased volumes.
	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; exploration expense; depreciation, depletion, and amortization (DD&A); impairments; interest expense; total (gains) losses on derivatives, net, less net cash from settlement of commodity derivatives; and certain items not related to the Company’s normal operations, less net income attributable to noncontrolling interests. During the periods presented, items not related to the Company’s normal operations included Deepwater Horizon settlement and related costs, Tronox-related contingent loss, and certain other nonoperating items included in other (income) expense, net. The Company’s definition of Adjusted EBITDAX excludes exploration expense as it is not an indicator of operating efficiency for a given reporting period. However, exploration expense is monitored by management as part of costs incurred in exploration and development activities. Similarly, 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 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 that the presentation of Adjusted EBITDAX provides information useful in assessing the Company’s financial condition and results of operations and that Adjusted EBITDAX is a widely accepted financial indicator of a company’s ability to incur and service debt, fund capital expenditures, and make distributions to stockholders. 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 or cash flows from operating activities. Below is a reconciliation of consolidated Adjusted EBITDAX to income (loss) before income taxes:
		Three Months Ended
		March 31,
	millions	2015			2014
	Income (loss) before income taxes	$	(4,628	)	$	(1,962	)
	Exploration expense	1,083			299
	DD&A	1,256			1,124
	Impairments	2,783			3
	Interest expense	216			183
	Total (gains) losses on derivatives, net, less net cash from settlement of	243			363
	commodity derivatives
	Deepwater Horizon settlement and related costs	4			—
	Tronox-related contingent loss	5			4,300
	Certain other nonoperating items	22			—
	Less net income attributable to noncontrolling interests	32			43
	Consolidated Adjusted EBITDAX	$	952		$	4,267
	14. Segment Information (Continued)
	Information presented below as “Other and Intersegment Eliminations” includes corporate costs, results from hard-minerals royalties, and net cash from settlement of commodity derivatives. The following summarizes selected financial information for Anadarko’s reporting segments:
	millions	Oil and Gas			Midstream			Marketing			Other and			Total
		Exploration									Intersegment
		& Production									Eliminations
	Three Months Ended March 31, 2015
	Sales revenues	$	1,070		$	174		$	1,341		$	—		$	2,585
	Intersegment revenues	1,117			302			(1,191		)	(228		)	—
	Gains (losses) on divestitures and other, net	(338		)	—			—			74			(264		)
	Total revenues and other	1,849			476			150			(154		)	2,321
	Operating costs and expenses (1)	1,002			240			198			(37		)	1,403
	Net cash from settlement of commodity	—			—			—			(90		)	(90		)
	derivatives
	Other (income) expense, net (2)	—			—			—			25			25
	Net income attributable to noncontrolling interests	—			32			—			—			32
	Total expenses and other	1,002			272			198			(102		)	1,370
	Total (gains) losses on derivatives, net	—			—			1			—			1
	included in marketing revenue, less net
	cash from settlement
	Adjusted EBITDAX	$	847		$	204		$	(47	)	$	(52	)	$	952
	Three Months Ended March 31, 2014
	Sales revenues	$	2,389		$	120		$	1,829		$	—		$	4,338
	Intersegment revenues	1,553			320			(1,689		)	(184		)	—
	Gains (losses) on divestitures and other, net	1,460			(2		)	—			48			1,506
	Total revenues and other	5,402			438			140			(136		)	5,844
	Operating costs and expenses (1)	1,012			232			181			18			1,443
	Net cash from settlement of commodity	—			—			—			92			92
	derivatives
	Other (income) expense, net	—			—			—			1			1
	Net income attributable to noncontrolling interests	—			43			—			—			43
	Total expenses and other	1,012			275			181			111			1,579
	Total (gains) losses on derivatives, net	—			—			2			—			2
	included in marketing revenue, less net
	cash from settlement
	Adjusted EBITDAX	$	4,390		$	163		$	(39	)	$	(247	)	$	4,267
	__________________________________________________________________
	(1)	Operating costs and expenses excludes exploration expense, DD&A, impairments, and Deepwater Horizon settlement and related costs since these expenses are excluded from Adjusted EBITDAX.
	(2)	Other (income) expense, net excludes certain other nonoperating items since these items are excluded from Adjusted EBITDAX.

Pension_Plans_and_Other_Postre

Pension Plans and Other Postretirement Benefits	3 Months Ended
	Mar. 31, 2015
Compensation and Retirement Disclosure [Abstract]
Pension Plans and Other Postretirement Benefits	15. 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	2015			2014			2015		2014
	Three Months Ended March 31
	Service cost	$	30		$	25		$	3	$	2
	Interest cost	25			25			4		4
	Expected return on plan assets	(27		)	(27		)	—		—
	Amortization of net actuarial loss (gain)	13			9			—		(2		)
	Net periodic benefit cost	$	41		$	32		$	7	$	4

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2015
Accounting Policies [Abstract]
Use of Estimates	Use of Estimates  The preparation of financial statements in accordance with generally accepted accounting principles in the United States requires management to make informed judgments and estimates that affect the reported amounts of assets, liabilities, revenues, and expenses. Management evaluates its estimates and related assumptions regularly, including those related to proved reserves; the value of properties and equipment; goodwill; intangible assets; asset retirement obligations; litigation liabilities; environmental liabilities; pension assets, liabilities, and costs; income taxes; and fair values. Changes in facts and circumstances or additional information may result in revised estimates, and actual results may differ from these estimates.
Recently Issued Accounting Standards	Recently Issued Accounting Standards  The Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2015-02, Consolidation—Amendments to the Consolidation Analysis. This ASU will simplify existing requirements by reducing the number of consolidation models and placing more emphasis on risk of loss when determining a controlling financial interest. The provisions will affect how limited partnerships and similar entities are assessed for consolidation, including the elimination of the presumption that a general partner should consolidate a limited partnership. This ASU is effective for annual and interim periods beginning in 2016 and is required to be adopted using a retrospective or modified retrospective approach, with early adoption permitted. The Company is evaluating the impact of the adoption of this ASU on its consolidated financial statements.
	The FASB issued ASU 2014-09, Revenue from Contracts with Customers. This ASU supersedes the revenue recognition requirements in Topic 605, Revenue Recognition, and industry-specific guidance in Subtopic 932-605, Extractive Activities—Oil and Gas—Revenue Recognition, and 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. This ASU is effective for annual and interim periods beginning in 2017 and is required to be adopted using one of two retrospective application methods, with no early adoption permitted. The Company is evaluating the impact of the adoption of this ASU on its consolidated financial statements.

Inventories_Tables

Inventories (Tables)	3 Months Ended
	Mar. 31, 2015
Energy Related Inventory [Abstract]
Inventory Disclosure Table	The following summarizes the major classes of inventories included in other current assets:
	millions	March 31,		December 31,
		2015		2014
	Oil	$	97	$	133
	Natural gas	3		27
	NGLs	70		83
	Total inventories	$	170	$	243

Impairments_Tables

Impairments (Tables)	3 Months Ended
	Mar. 31, 2015
Asset Impairment Charges [Abstract]
Schedule of Impairment Expense	The following summarizes impairments of proved properties and the related post-impairment fair values by segment:
		Three Months Ended
	millions	Impairment		Fair Value (1)
	March 31, 2015
	Oil and gas exploration and production
	Long-lived assets held for use
	U.S. onshore properties	$	2,307	$	1,299
	Midstream
	Long-lived assets held for use	476		206
	Total	$	2,783	$	1,505
	March 31, 2014
	Oil and gas exploration and production
	Cost-method investment (2)	$	1	$	32
	Midstream
	Long-lived assets held for use	2		—
	Total	$	3	$	32
	__________________________________________________________________
	(1)	Measured using the income approach and Level 3 inputs.
	(2)	Represents the after-tax net investment.

Derivative_Instruments_Tables

Derivative Instruments (Tables)	3 Months Ended
	Mar. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Derivative Instruments	The following is a summary of the Company’s derivative instruments related to natural-gas production/processing derivative activities at March 31, 2015:
		2015
		Settlement
	Natural Gas
	Three-Way Collars (thousand MMBtu/d)	635
	Average price per MMBtu
	Ceiling sold price (call)	$	4.76
	Floor purchased price (put)	$	3.75
	Floor sold price (put)	$	2.75
	Extendable Fixed-Price Contracts (thousand MMBtu/d) (1)	170
	Average price per MMBtu	$	4.17
	__________________________________________________________________
	(1)	The extendable fixed-price contracts have a contract term of January 2015 to December 2015 with an option for the counterparty to extend the contract term to December 2016 at the same price.
	MMBtu—million British thermal units
	MMBtu/d—million British thermal units per day
	The Company had the following outstanding interest-rate swaps at March 31, 2015:
	millions except percentages					Reference Period			Weighted-Average
	Notional Principal Amount					Start		End	Interest Rate
	$	50				Sep-16		Sep-26	5.91%
	$	1,850				Sep-16		Sep-46	6.06%
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		March 31,				December 31,			March 31,				December 31,
	Balance Sheet Classification		2015				2014			2015				2014
	Commodity derivatives
	Other current assets		$	351			$	421		$	(86	)		$	(118	)
	Other assets		35				1			—				—
	Accrued expenses		65				71			(117		)		(114		)
	Other liabilities		—				—			(31		)		(6		)
			451				493			(234		)		(238		)
	Interest-rate derivatives
	Other liabilities		—				—			(1,422		)		(1,217		)
	Total derivatives		$	451			$	493		$	(1,656	)		$	(1,455	)
	The following summarizes gains and losses related to derivative instruments:
	millions		Three Months Ended
			March 31,
	Classification of (Gain) Loss Recognized		2015				2014
	Commodity derivatives
	Gathering, processing, and marketing sales (1)		$	—			$	8
	(Gains) losses on derivatives, net		(53		)		215
	Interest-rate derivatives
	(Gains) losses on derivatives, net		205				238
	Total (gains) losses on derivatives, net		$	152			$	461
	__________________________________________________________________
	(1)	Represents the effect of Marketing and Trading Derivative Activities.
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
	March 31, 2015	Level 1				Level 2			Level 3				Netting (1)				Collateral			Total
	Assets
	Commodity derivatives
	Financial institutions	$	—			$	431		$	—			$	(151	)		$	(4	)	$	276
	Other counterparties	—				20			—				—				—			20
	Total derivative assets	$	—			$	451		$	—			$	(151	)		$	(4	)	$	296
	Liabilities
	Commodity derivatives
	Financial institutions	$	—			$	(183	)	$	—			$	151			$	1		$	(31	)
	Other counterparties	—				(51		)	—				—				—			(51		)
	Interest-rate derivatives	—				(1,422		)	—				—				169			(1,253		)
	Total derivative liabilities	$	—			$	(1,656	)	$	—			$	151			$	170		$	(1,335	)
	December 31, 2014
	Assets
	Commodity derivatives
	Financial institutions	$	—			$	471		$	—			$	(187	)		$	(13	)	$	271
	Other counterparties	—				22			—				(2		)		—			20
	Total derivative assets	$	—			$	493		$	—			$	(189	)		$	(13	)	$	291
	Liabilities
	Commodity derivatives
	Financial institutions	$	—			$	(234	)	$	—			$	187			$	—		$	(47	)
	Other counterparties	—				(4		)	—				2				—			(2		)
	Interest-rate derivatives	—				(1,217		)	—				—				23			(1,194		)
	Total derivative liabilities	$	—			$	(1,455	)	$	—			$	189			$	23		$	(1,243	)
	__________________________________________________________________
	(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_and_Interest_Expense_Tabl

Debt and Interest Expense (Tables)	3 Months Ended
	Mar. 31, 2015
Debt Disclosure [Abstract]
Debt Outstanding and Debt Activity Tables	The following summarizes the Company’s outstanding debt:
	millions	March 31,			December 31,
		2015			2014
	Total debt at face value	$	18,450		$	16,687
	Net unamortized discounts and premiums (1)	(1,606		)	(1,616		)
	Total borrowings	$	16,844		$	15,071
	Capital lease obligation	21			21
	Less short-term debt	500			—
	Total long-term debt	$	16,365		$	15,092
	__________________________________________________________________
	(1)	Unamortized discounts and premiums are amortized over the term of the related debt.
	The following summarizes the Company’s debt activity during the three months ended March 31, 2015:
		Carrying
	millions	Value			Description
	Balance at December 31, 2014	$	15,071
	Borrowings	1,500			$5.0 billion revolving credit facility
		1,800			364-Day Facility
		140			WES revolving credit facility
		1,153			Commercial paper notes
	Repayments	(1,500		)	$5.0 billion revolving credit facility
		(1,300		)	364-Day Facility
		(30		)	WES revolving credit facility
	Other, net	10			Amortization of debt discounts and premiums
	Balance at March 31, 2015	$	16,844
Interest Expense Table	The following summarizes interest expense:
		Three Months Ended
		March 31,
	millions	2015			2014
	Debt and other	$	254		$	240
	Capitalized interest	(38		)	(57		)
	Total interest expense	$	216		$	183

Stockholders_Equity_Tables

Stockholders' Equity (Tables)	3 Months Ended
	Mar. 31, 2015
Stockholders' Equity Note [Abstract]
Earnings Per Share Table	The following provides a reconciliation between basic and diluted earnings per share attributable to common stockholders:
		Three Months Ended
		March 31,
	millions except per-share amounts	2015			2014
	Net income (loss)
	Net income (loss) attributable to common stockholders	$	(3,268	)	$	(2,669	)
	Less distributions on participating securities	1			—
	Basic	$	(3,269	)	$	(2,669	)
	Diluted	$	(3,269	)	$	(2,669	)
	Shares
	Average number of common shares outstanding—basic	507			504
	Average number of common shares outstanding—diluted	507			504
	Excluded (1)	11			11
	Net income (loss) per common share
	Basic	$	(6.45	)	$	(5.30	)
	Diluted	$	(6.45	)	$	(5.30	)
	Dividends per common share	$	0.27		$	0.18
	__________________________________________________________________
	(1)	Inclusion of certain shares would have had an anti-dilutive effect.

Accumulated_Other_Comprehensiv1

Accumulated Other Comprehensive Income (Loss) (Tables)	3 Months Ended
	Mar. 31, 2015
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Schedule Of Accumulated Other Comprehensive Income (Loss)	The following summarizes the after-tax changes in the balances of accumulated other comprehensive income (loss):
	millions	Interest-rate			Pension and Other Postretirement			Total
		Derivatives			Plans
		Previously
		Subject to Hedge
		Accounting
	Balance at December 31, 2014	$	(48	)	$	(469	)	$	(517	)
	Reclassifications to Consolidated Statement of Income	1			9			10
	Balance at March 31, 2015	$	(47	)	$	(460	)	$	(507	)

Income_Taxes_Tables

Income Taxes (Tables)	3 Months Ended
	Mar. 31, 2015
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
		March 31,
	millions except percentages	2015			2014
	Income tax expense (benefit)	$	(1,392	)	$	664
	Effective tax rate	30		%	(34		)%

Supplemental_Cash_Flow_Informa1

Supplemental Cash Flow Information (Tables)	3 Months Ended
	Mar. 31, 2015
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:
		Three Months Ended
		March 31,
	millions	2015			2014
	Cash paid (received)
	Interest, net of amounts capitalized (1)	$	1,532		$	265
	Income taxes, net of refunds	(5		)	598
	Non-cash investing activities
	Fair value of properties and equipment from non-cash transactions	$	54		$	—
	Asset retirement cost additions	63			47
	Accruals of property, plant, and equipment	1,061			1,544
	Net liabilities assumed (divested) in acquisitions and divestitures	19			(25		)
	Non-cash investing and financing activities
	Floating production, storage, and offloading vessel construction period obligation	$	18		$	34
	__________________________________________________________________
	(1)	Includes $1.2 billion of interest related to the Tronox settlement payment in 2015.

Segment_Information_Tables

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2015
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
		March 31,
	millions	2015			2014
	Income (loss) before income taxes	$	(4,628	)	$	(1,962	)
	Exploration expense	1,083			299
	DD&A	1,256			1,124
	Impairments	2,783			3
	Interest expense	216			183
	Total (gains) losses on derivatives, net, less net cash from settlement of	243			363
	commodity derivatives
	Deepwater Horizon settlement and related costs	4			—
	Tronox-related contingent loss	5			4,300
	Certain other nonoperating items	22			—
	Less net income attributable to noncontrolling interests	32			43
	Consolidated Adjusted EBITDAX	$	952		$	4,267
Schedule of Segment Reporting Information, by Segment	The following summarizes selected financial information for Anadarko’s reporting segments:
	millions	Oil and Gas			Midstream			Marketing			Other and			Total
		Exploration									Intersegment
		& Production									Eliminations
	Three Months Ended March 31, 2015
	Sales revenues	$	1,070		$	174		$	1,341		$	—		$	2,585
	Intersegment revenues	1,117			302			(1,191		)	(228		)	—
	Gains (losses) on divestitures and other, net	(338		)	—			—			74			(264		)
	Total revenues and other	1,849			476			150			(154		)	2,321
	Operating costs and expenses (1)	1,002			240			198			(37		)	1,403
	Net cash from settlement of commodity	—			—			—			(90		)	(90		)
	derivatives
	Other (income) expense, net (2)	—			—			—			25			25
	Net income attributable to noncontrolling interests	—			32			—			—			32
	Total expenses and other	1,002			272			198			(102		)	1,370
	Total (gains) losses on derivatives, net	—			—			1			—			1
	included in marketing revenue, less net
	cash from settlement
	Adjusted EBITDAX	$	847		$	204		$	(47	)	$	(52	)	$	952
	Three Months Ended March 31, 2014
	Sales revenues	$	2,389		$	120		$	1,829		$	—		$	4,338
	Intersegment revenues	1,553			320			(1,689		)	(184		)	—
	Gains (losses) on divestitures and other, net	1,460			(2		)	—			48			1,506
	Total revenues and other	5,402			438			140			(136		)	5,844
	Operating costs and expenses (1)	1,012			232			181			18			1,443
	Net cash from settlement of commodity	—			—			—			92			92
	derivatives
	Other (income) expense, net	—			—			—			1			1
	Net income attributable to noncontrolling interests	—			43			—			—			43
	Total expenses and other	1,012			275			181			111			1,579
	Total (gains) losses on derivatives, net	—			—			2			—			2
	included in marketing revenue, less net
	cash from settlement
	Adjusted EBITDAX	$	4,390		$	163		$	(39	)	$	(247	)	$	4,267
	__________________________________________________________________
	(1)	Operating costs and expenses excludes exploration expense, DD&A, impairments, and Deepwater Horizon settlement and related costs since these expenses are excluded from Adjusted EBITDAX.
	(2)	Other (income) expense, net excludes certain other nonoperating items since these items are excluded from Adjusted EBITDAX.

Pension_Plans_and_Other_Postre1

Pension Plans and Other Postretirement Benefits (Tables)	3 Months Ended
	Mar. 31, 2015
Compensation and Retirement Disclosure [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	2015			2014			2015		2014
	Three Months Ended March 31
	Service cost	$	30		$	25		$	3	$	2
	Interest cost	25			25			4		4
	Expected return on plan assets	(27		)	(27		)	—		—
	Amortization of net actuarial loss (gain)	13			9			—		(2		)
	Net periodic benefit cost	$	41		$	32		$	7	$	4

Acquisitions_Divestitures_and_1

Acquisitions, Divestitures, and Assets Held for Sale (Detail) (USD $)	3 Months Ended		1 Months Ended	0 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Apr. 30, 2015	Nov. 25, 2014
Property, Plant, and Equipment [Line Items]
Purchase price	$0	$4
(Gains) losses on divestitures, net	334	-1,459
Proceeds from divestitures	22	3,257
Oil and Gas Exploration and Production Reporting Segment [Member] | Held-for-sale [Member]
Property, Plant, and Equipment [Line Items]
Current assets associated with assets held for sale	29
Long-term assets associated with assets held for sale	743
Current liabilities associated with assets held for sale	17
Long-term liabilities associated with assets held for sale	78
Oil and Gas Exploration and Production Reporting Segment [Member] | Held-for-sale [Member] | Certain U.S. Onshore Rockies Assets [Member] | Nonrecurring [Member] | Market Approach Valuation Technique [Member] | Fair Value, Inputs, Level 2 [Member]
Property, Plant, and Equipment [Line Items]
Loss on assets held for sale	340
Oil and Gas Exploration and Production Reporting Segment [Member] | Assets Disposed of by Sale [Member] | Certain U.S. Onshore Rockies Assets [Member] | Subsequent Event [Member]
Property, Plant, and Equipment [Line Items]
Proceeds from divestitures			703
Gathering and Processing Assets in the Delaware basin [Member]
Property, Plant, and Equipment [Line Items]
Purchase price				1,554
Changes to the fair value of assets acquired and liabilities assumed

Inventories_Detail

Inventories (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Millions, unless otherwise specified
Energy Related Inventory [Abstract]
Oil	$97	$133
Natural gas	3	27
NGLs	70	83
Total inventories	$170	$243

Impairments_Impairments_and_Fa

Impairments - Impairments and Fair Values by Segment Table (Detail) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Impaired Long Lived Assets Held and Used [Line Items]
Total impairments	$2,783		$3
Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | Income Approach Valuation Technique [Member]
Impaired Long Lived Assets Held and Used [Line Items]
Total fair value	1,505	[1]	32	[1]
Oil and Gas Exploration and Production Reporting Segment [Member]
Impaired Long Lived Assets Held and Used [Line Items]
Impairment of cost-method investment			1
Oil and Gas Exploration and Production Reporting Segment [Member] | Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | Income Approach Valuation Technique [Member]
Impaired Long Lived Assets Held and Used [Line Items]
Fair value of cost-method investment			32	[1],[2]
Oil and Gas Exploration and Production Reporting Segment [Member] | U.S. Onshore Properties [Member]
Impaired Long Lived Assets Held and Used [Line Items]
Impairment of long-lived assets held for use	2,307
Oil and Gas Exploration and Production Reporting Segment [Member] | U.S. Onshore Properties [Member] | Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | Income Approach Valuation Technique [Member]
Impaired Long Lived Assets Held and Used [Line Items]
Fair value of long-lived assets held for use	1,299	[1]
Midstream Reporting Segment [Member]
Impaired Long Lived Assets Held and Used [Line Items]
Impairment of long-lived assets held for use	476		2
Midstream Reporting Segment [Member] | Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | Income Approach Valuation Technique [Member]
Impaired Long Lived Assets Held and Used [Line Items]
Fair value of long-lived assets held for use	$206	[1]	$0	[1]
[1]	Measured using the income approach and Level 3 inputs.
[2]	Represents the after-tax net investment.

Impairments_Impairments_of_Unp

Impairments - Impairments of Unproved Properties (Detail) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Property, Plant, and Equipment [Line Items]
Impairment of unproved properties	$1,009	$198
U.S. Onshore Properties [Member]
Property, Plant, and Equipment [Line Items]
Impairment of unproved properties	$935

Suspended_Exploratory_Well_Cos1

Suspended Exploratory Well Costs (Detail) (USD $)	3 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Capitalized Exploratory Well Costs [Abstract]
Suspended exploratory well costs	$1,600,000,000	$1,500,000,000
Exploratory well costs previously capitalized as suspended exploratory well costs for greater than one year at December 31, 2014, charged to dry hole expense	$0

Noncontrolling_Interests_Detai

Noncontrolling Interests (Detail) (USD $)	3 Months Ended		12 Months Ended
In Millions, except Share data in Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Noncontrolling Interest [Line Items]
Net proceeds raised from offering	$31	$18
Western Gas Equity Partners, LP [Member] | Limited Partner [Member]
Noncontrolling Interest [Line Items]
Ownership interest in subsidiary	88.30%
Public ownership interest in subsidiary	11.70%
Western Gas Partners, LP [Member] | Class C Units [Member]
Noncontrolling Interest [Line Items]
Units issued in private placement	46		11,000
Western Gas Partners, LP [Member] | Continuous Offering Program [Member]
Noncontrolling Interest [Line Items]
Units issued to the public	480
Net proceeds raised from offering	$31
Western Gas Partners, LP [Member] | Limited Partner [Member]
Noncontrolling Interest [Line Items]
Public ownership interest in subsidiary	55.10%
Western Gas Partners, LP [Member] | Limited Partner [Member] | Western Gas Equity Partners, LP, Ownership Interest [Member]
Noncontrolling Interest [Line Items]
Ownership interest in subsidiary	34.80%
Western Gas Partners, LP [Member] | Limited Partner [Member] | Other Anadarko Subsidiaries, Ownership Interest [Member]
Noncontrolling Interest [Line Items]
Ownership interest in subsidiary	8.30%
Western Gas Partners, LP [Member] | General Partner [Member] | Western Gas Equity Partners, LP, Ownership Interest [Member]
Noncontrolling Interest [Line Items]
Ownership interest in subsidiary	1.80%

Derivative_Instruments_Oil_and

Derivative Instruments - Oil and Natural-Gas Production/Processing Derivative Activities Table (Detail) (Not Designated as Hedging Instrument [Member], Price Risk Derivative [Member])	3 Months Ended
	Mar. 31, 2015
Three-Way Collars Natural Gas 2015 [Member]
Derivative [Line Items]
Natural-gas derivative nonmonetary notional amount per day	635,000
Extendable Fixed Price Contracts Natural Gas 2015 [Member]
Derivative [Line Items]
Natural-gas derivative nonmonetary notional amount per day	170,000	[1]
Average price per MMBtu
Average price per MMBtu	4.17
Call Option [Member] | Short [Member] | Three-Way Collars Natural Gas 2015 [Member]
Average price per MMBtu
Average ceiling price	4.76
Put Option [Member] | Short [Member] | Three-Way Collars Natural Gas 2015 [Member]
Average price per MMBtu
Average floor price	2.75
Put Option [Member] | Long [Member] | Three-Way Collars Natural Gas 2015 [Member]
Average price per MMBtu
Average floor price	3.75
[1]	The extendable fixed-price contracts have a contract term of January 2015 to December 2015 with an option for the counterparty to extend the contract term to December 2016 at the same price.

Derivative_Instruments_Additio

Derivative Instruments - Additional Information (Detail) (Not Designated as Hedging Instrument [Member], USD $)	3 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
	Mcf	Mcf
Derivative [Line Items]
Gross derivative liability	1,656	1,455
Aggregate fair value of derivative instruments with credit-risk-related contingent features for which a net liability position existed (net of collateral)	1,200	97
Permitted to Offset Gross Derivative Asset with Financial Institutions [Member]
Derivative [Line Items]
Gross derivative liability	237	289
Natural Gas [Member] | Commodity [Member]
Derivative [Line Items]
Financial derivative transactions	3,000,000	6,000,000

Derivative_Instruments_Interes

Derivative Instruments - Interest-Rate Derivatives Table (Detail) (Not Designated as Hedging Instrument [Member], USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015
Interest-Rate Swap 1 [Member]
Derivative [Line Items]
Notional principal amount of interest-rate swap	50
Weighted-average interest rate for interest-rate swap	5.91%
Interest-Rate Swap 1 [Member] | Minimum [Member]
Derivative [Line Items]
Reference period for interest-rate swap	1-Sep-16
Interest-Rate Swap 1 [Member] | Maximum [Member]
Derivative [Line Items]
Reference period for interest-rate swap	1-Sep-26
Interest-Rate Swap 2 [Member]
Derivative [Line Items]
Notional principal amount of interest-rate swap	1,850
Weighted-average interest rate for interest-rate swap	6.06%
Interest-Rate Swap 2 [Member] | Minimum [Member]
Derivative [Line Items]
Reference period for interest-rate swap	1-Sep-16
Interest-Rate Swap 2 [Member] | Maximum [Member]
Derivative [Line Items]
Reference period for interest-rate swap	1-Sep-46

Derivative_Instruments_Effect_

Derivative Instruments - Effect of Derivative Instruments - Balance Sheet Table (Detail) (Not Designated as Hedging Instrument [Member], USD $)	Mar. 31, 2015	Dec. 31, 2014
In Millions, unless otherwise specified
Derivatives Fair Value [Line Items]
Gross derivative assets	$451	$493
Gross derivative liabilities	-1,656	-1,455
Commodity Derivatives [Member]
Derivatives Fair Value [Line Items]
Gross derivative assets	451	493
Gross derivative liabilities	-234	-238
Commodity Derivatives [Member] | Other Current Assets [Member]
Derivatives Fair Value [Line Items]
Gross derivative assets	351	421
Gross derivative liabilities	-86	-118
Commodity Derivatives [Member] | Other Assets [Member]
Derivatives Fair Value [Line Items]
Gross derivative assets	35	1
Gross derivative liabilities	0	0
Commodity Derivatives [Member] | Accrued Expenses [Member]
Derivatives Fair Value [Line Items]
Gross derivative assets	65	71
Gross derivative liabilities	-117	-114
Commodity Derivatives [Member] | Other Liabilities [Member]
Derivatives Fair Value [Line Items]
Gross derivative assets	0	0
Gross derivative liabilities	-31	-6
Interest-Rate Derivatives [Member] | Other Liabilities [Member]
Derivatives Fair Value [Line Items]
Gross derivative assets	0	0
Gross derivative liabilities	($1,422)	($1,217)

Derivative_Instruments_Effect_1

Derivative Instruments - Effect of Derivative Instruments - Statement of Income Table (Detail) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Derivative [Line Items]
Total (gains) losses on derivatives, net	$152		$461
Commodity Derivatives [Member] | Gathering, Processing, and Marketing Sales [Member]
Derivative [Line Items]
Total (gains) losses on derivatives, net	0	[1]	8	[1]
Commodity Derivatives [Member] | (Gains) Losses on Derivatives, Net [Member]
Derivative [Line Items]
Total (gains) losses on derivatives, net	-53		215
Interest-Rate Derivatives [Member] | (Gains) Losses on Derivatives, Net [Member]
Derivative [Line Items]
Total (gains) losses on derivatives, net	$205		$238
[1]	Represents the effect of Marketing and Trading Derivative Activities.

Derivative_Instruments_Fair_Va

Derivative Instruments - Fair Value Table (Detail) (Not Designated as Hedging Instrument [Member], USD $)	Mar. 31, 2015		Dec. 31, 2014
In Millions, unless otherwise specified
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gross derivative assets	$451		$493
Gross derivative liabilities	-1,656		-1,455
Derivative assets netting	-151	[1]	-189	[1]
Derivative liabilities netting	151	[1]	189	[1]
Cash collateral from counterparties	-4		-13
Cash collateral held by counterparties	170		23
Derivative assets	296		291
Derivative liabilities	-1,335		-1,243
Commodity Derivatives [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gross derivative assets	451		493
Gross derivative liabilities	-234		-238
Interest-Rate Derivatives [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liabilities netting	0	[1]	0	[1]
Cash collateral held by counterparties	169		23
Derivative liabilities	-1,253		-1,194
Financial Institutions [Member] | Commodity Derivatives [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets netting	-151	[1]	-187	[1]
Derivative liabilities netting	151	[1]	187	[1]
Cash collateral from counterparties	-4		-13
Cash collateral held by counterparties	1		0
Derivative assets	276		271
Derivative liabilities	-31		-47
Other Counterparties [Member] | Commodity Derivatives [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets netting	0	[1]	-2	[1]
Derivative liabilities netting	0	[1]	2	[1]
Cash collateral from counterparties	0		0
Cash collateral held by counterparties	0		0
Derivative assets	20		20
Derivative liabilities	-51		-2
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		0
Gross derivative liabilities	0		0
Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Interest-Rate Derivatives [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gross derivative liabilities	0		0
Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Financial Institutions [Member] | Commodity Derivatives [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] | Fair Value, Inputs, Level 1 [Member] | Other Counterparties [Member] | Commodity Derivatives [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] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gross derivative assets	451		493
Gross derivative liabilities	-1,656		-1,455
Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Interest-Rate Derivatives [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gross derivative liabilities	-1,422		-1,217
Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Financial Institutions [Member] | Commodity Derivatives [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gross derivative assets	431		471
Gross derivative liabilities	-183		-234
Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Other Counterparties [Member] | Commodity Derivatives [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gross derivative assets	20		22
Gross derivative liabilities	-51		-4
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] | Fair Value, Inputs, Level 3 [Member] | Interest-Rate Derivatives [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gross derivative liabilities	0		0
Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Financial Institutions [Member] | Commodity Derivatives [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] | Fair Value, Inputs, Level 3 [Member] | Other Counterparties [Member] | Commodity Derivatives [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.

Debt_and_Interest_Expense_Outs

Debt and Interest Expense - Outstanding Debt Table (Detail) (USD $)	Mar. 31, 2015		Dec. 31, 2014
In Millions, unless otherwise specified
Debt Disclosure [Abstract]
Total debt at face value	$18,450		$16,687
Net unamortized discounts and premiums (1)	-1,606	[1]	-1,616	[1]
Total borrowings	16,844		15,071
Capital lease obligation	21		21
Less short-term debt	500		0
Total long-term debt	$16,365		$15,092
[1]	Unamortized discounts and premiums are amortized over the term of the related debt.

Debt_and_Interest_Expense_Addi

Debt and Interest Expense - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2015	Dec. 31, 2014	Jan. 23, 2015
Commercial Paper [Member]
Debt Instrument [Line Items]
Line of credit, maximum capacity	$3,000,000,000
Commercial paper, outstanding borrowings	1,200,000,000
Commercial paper, weighted-average interest rate	0.67%
Amount of commercial paper outstanding classified as long-term debt on the Company's Consolidated Balance Sheet	1,200,000,000
Commercial Paper [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt instrument, term	397 days
Fair Value, Inputs, Level 2 [Member] | Market Approach Valuation Technique [Member]
Debt Instrument [Line Items]
Estimated fair value of total borrowings	19,300,000,000	17,400,000,000
Zero-Coupon Senior Notes [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Debt instrument, maturity date	10-Oct-36
Debt Instrument, earliest call date	10-Oct-15
Zero-Coupon Senior Notes [Member] | Senior Notes [Member] | Accreted Value at Next Potential Put Date [Member]
Debt Instrument [Line Items]
Debt instrument, accreted value	796,000,000
$5.0 billion Facility [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit, maximum capacity			5,000,000,000
Five-Year Credit Facility [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit, maximum capacity	3,000,000,000
Debt instrument, term	5 years
Line of credit, expandable maximum capacity	4,000,000,000
Line of credit, outstanding borrowings	0
Five-Year Credit Facility [Member] | Revolving Credit Facility [Member] | Minimum [Member]
Debt Instrument [Line Items]
Applicable margin added	0.00%
Five-Year Credit Facility [Member] | Revolving Credit Facility [Member] | Maximum [Member]
Debt Instrument [Line Items]
Applicable margin added	1.65%
Ratio of indebtedness to total capital	0.65
364-Day Credit Facility [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit, maximum capacity	2,000,000,000
Debt instrument, term	364 days
Line of credit, outstanding borrowings	500,000,000
Line of credit, interest rate	1.29%
Line of credit, available borrowing capacity	1,500,000,000
364-Day Credit Facility [Member] | Revolving Credit Facility [Member] | Minimum [Member]
Debt Instrument [Line Items]
Applicable margin added	0.00%
364-Day Credit Facility [Member] | Revolving Credit Facility [Member] | Maximum [Member]
Debt Instrument [Line Items]
Applicable margin added	1.68%
Ratio of indebtedness to total capital	0.65
WES RCF [Member] | Revolving Credit Facility [Member] | Western Gas Partners, LP [Member]
Debt Instrument [Line Items]
Line of credit, maximum capacity	1,200,000,000
Line of credit, expandable maximum capacity	1,500,000,000
Line of credit, outstanding borrowings	620,000,000
Line of credit, interest rate	1.48%
Line of credit, available borrowing capacity	567,000,000
Line of credit, expiration date	26-Feb-19
Letters of credit, outstanding	$13,000,000

Debt_and_Interest_Expense_Debt

Debt and Interest Expense - Debt Activity Table (Detail) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015
Debt Disclosure [Abstract]
Carrying value, beginning balance	$15,071
Debt Instrument [Line Items]
Other, net	10
Carrying value, ending balance	16,844
Commercial Paper [Member]
Debt Instrument [Line Items]
Borrowings, commercial paper	1,153
$5.0 billion Facility [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Borrowings, credit facility	1,500
Repayments, credit facility	-1,500
364-Day Credit Facility [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Borrowings, credit facility	1,800
Repayments, credit facility	-1,300
WES RCF [Member] | Revolving Credit Facility [Member] | Western Gas Partners, LP [Member]
Debt Instrument [Line Items]
Borrowings, credit facility	140
Repayments, credit facility	($30)

Debt_and_Interest_Expense_Inte

Debt and Interest Expense - Interest Expense Table (Detail) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Debt Disclosure [Abstract]
Debt and other	$254	$240
Capitalized interest	-38	-57
Total interest expense	$216	$183

Stockholders_Equity_Detail

Stockholders' Equity (Detail) (USD $)	3 Months Ended
In Millions, except Per Share data, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Net income (loss)
Net income (loss) attributable to common stockholders	($3,268)		($2,669)
Less distributions on participating securities	1		0
Basic	-3,269		-2,669
Diluted	($3,269)		($2,669)
Shares
Average number of common shares outstanding—basic	507		504
Average number of common shares outstanding—diluted	507		504
Excluded (1)	11	[1]	11	[1]
Net income (loss) per common share
Basic	($6.45)		($5.30)
Diluted	($6.45)		($5.30)
Dividends per common share	$0.27		$0.18
[1]	Inclusion of certain shares would have had an anti-dilutive effect.

Accumulated_Other_Comprehensiv2

Accumulated Other Comprehensive Income (Loss) (Detail) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at December 31, 2014	($517)
Reclassifications to Consolidated Statement of Income	10
Balance at March 31, 2015	-507
Interest-rate Derivatives Previously Subject to Hedge Accounting [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at December 31, 2014	-48
Reclassifications to Consolidated Statement of Income	1
Balance at March 31, 2015	-47
Pension and Other Postretirement Plans [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at December 31, 2014	-469
Reclassifications to Consolidated Statement of Income	9
Balance at March 31, 2015	($460)

Contingencies_Tronox_Litigatio

Contingencies - Tronox Litigation (Detail) (Tronox Litigation [Member], Judicial Ruling [Member], USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2013	Dec. 31, 2014
Loss Contingencies [Line Items]
Litigation-related contingent liability	$0	$5,150,000,000		$5,210,000,000
Payment for Tronox settlement	5,200,000,000
Litigation-related contingent loss	5,000,000	4,300,000,000	850,000,000
Post Settlement Interest Expense [Member]
Loss Contingencies [Line Items]
Litigation-related contingent loss	$5,000,000			$60,000,000

Contingencies_Deepwater_Horizo

Contingencies - Deepwater Horizon Events (Detail) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014	Sep. 30, 2011	Jun. 30, 2014
Macondo Exploration Well [Member]
Loss Contingencies [Line Items]
Anadarko's nonoperated interest				25.00%
Deepwater Horizon [Member] | Pending Litigation [Member]
Loss Contingencies [Line Items]
Litigation-related contingent loss	$4,000,000	$0
Litigation-related contingent liability	94,000,000		90,000,000
Allocation of fault assigned in Phase I Findings and Conclusions	0.00%
Deepwater Horizon [Member] | Pending Litigation [Member] | BP and BPAP [Member]
Loss Contingencies [Line Items]
Allocation of fault assigned in Phase I Findings and Conclusions	67.00%
Deepwater Horizon [Member] | Pending Litigation [Member] | Transocean [Member]
Loss Contingencies [Line Items]
Allocation of fault assigned in Phase I Findings and Conclusions	30.00%
Deepwater Horizon [Member] | Pending Litigation [Member] | Halliburton Energy Services [Member]
Loss Contingencies [Line Items]
Allocation of fault assigned in Phase I Findings and Conclusions	3.00%
Deepwater Horizon [Member] | Pending Litigation [Member] | Clean Water Act [Member]
Loss Contingencies [Line Items]
Litigation-related contingent loss			90,000,000
Litigation-related contingent liability	90,000,000				90,000,000
Barrels of oil discharged	3,190,000
Deepwater Horizon [Member] | BP indemnification liability [Member]
Loss Contingencies [Line Items]
Loss contingency accrual	$0

Income_Taxes_Income_Tax_Expens

Income Taxes - Income Tax Expense (Benefit) Table (Detail) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Income Tax Disclosure [Abstract]
Income tax expense (benefit)	($1,392)	$664
Effective tax rate	30.00%	-34.00%

Income_Taxes_Additional_Inform

Income Taxes - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Income Tax Disclosure [Abstract]
U.S. federal statutory rate	35.00%	35.00%
Accrued Expenses [Member]
Income Tax Disclosure [Line Items]
Accrued income taxes	388,000,000
Tronox Litigation [Member] | Judicial Ruling [Member]
Income Tax Disclosure [Line Items]
Deferred tax benefit related to the Tronox settlement	577,000,000
Uncertain tax position	1,300,000,000
Tronox Litigation [Member] | Judicial Ruling [Member] | Other Assets [Member]
Income Tax Disclosure [Line Items]
Deferred tax benefit related to the Tronox settlement	561,000,000

Supplemental_Cash_Flow_Informa2

Supplemental Cash Flow Information (Detail) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Loss Contingencies [Line Items]
Interest, net of amounts capitalized (1)	$1,532	[1]	$265
Income taxes, net of refunds	-5		598
Non-cash investing activities
Fair value of properties and equipment from non-cash transactions	54		0
Asset retirement cost additions	63		47
Accruals of property, plant, and equipment	1,061		1,544
Net liabilities assumed (divested) in acquisitions and divestitures	19		-25
Non-cash investing and financing activities
Floating production, storage, and offloading vessel construction period obligation	18		34
Tronox Litigation [Member] | Judicial Ruling [Member]
Loss Contingencies [Line Items]
Deferred tax benefit related to the Tronox settlement	577
Interest, net of amounts capitalized (1)	1,200
Other Assets [Member] | Tronox Litigation [Member] | Judicial Ruling [Member]
Loss Contingencies [Line Items]
Deferred tax benefit related to the Tronox settlement	$561
[1]	Includes $1.2 billion of interest related to the Tronox settlement payment in 2015.

Segment_Information_Additional

Segment Information - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2015
	Segment
Segment Reporting [Abstract]
Number of reporting segments	3
Midstream Reporting Segment [Member]
Segment Reporting Information [Line Items]
Number of operating segments	2

Segment_Information_Reconcilia

Segment Information - Reconciliation of Consolidated Adjusted EBITDAX to Income (Loss) Before Income Taxes Table (Detail) (USD $)	3 Months Ended		12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2013
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income (loss) before income taxes	($4,628)	($1,962)
Exploration expense	1,083	299
DD&A	1,256	1,124
Impairments	2,783	3
Interest expense	216	183
Total (gains) losses on derivatives, net, less net cash from settlement of commodity derivatives	243	363
Less net income attributable to noncontrolling interests	32	43
Adjusted EBITDAX	952	4,267
Certain Other Nonoperating Items [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Certain other nonoperating items	22	0
Deepwater Horizon [Member] | Pending Litigation [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Litigation-related contingent loss	4	0
Certain other nonoperating items	4	0
Tronox Litigation [Member] | Judicial Ruling [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Litigation-related contingent loss	5	4,300	850
Certain other nonoperating items	($5,210)	$4,300

Segment_Information_Selected_F

Segment Information - Selected Financial Information for Anadarko's Reporting Segments Table (Detail) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014
Segment Reporting Information [Line Items]
Revenues	$2,585		$4,338
Gains (losses) on divestitures and other, net	-264		1,506
Total revenues and other	2,321		5,844
Operating costs and expenses (1)	1,403	[1]	1,443	[1]
Net cash from settlement of commodity derivatives	-91		98
Other (income) expense, net	47		1
Net income attributable to noncontrolling interests	32		43
Total expenses and other	1,370		1,579
Adjusted EBITDAX	952		4,267
(Gains) Losses on Derivatives, Net [Member] | Commodity Contract [Member]
Segment Reporting Information [Line Items]
Net cash from settlement of commodity derivatives	-90		92
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	1		2
Excluding Certain Other Nonoperating Items [Member]
Segment Reporting Information [Line Items]
Other (income) expense, net	25	[2]	1
Other and Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenues	0		0
Gains (losses) on divestitures and other, net	74		48
Total revenues and other	-154		-136
Operating costs and expenses (1)	-37	[1]	18	[1]
Total expenses and other	-102		111
Adjusted EBITDAX	-52		-247
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	-90		92
Other and Intersegment Eliminations [Member] | Excluding Certain Other Nonoperating Items [Member]
Segment Reporting Information [Line Items]
Other (income) expense, net	25	[2]	1
Other and Intersegment Eliminations [Member] | Intersegment Revenues [Member]
Segment Reporting Information [Line Items]
Revenues	-228		-184
Oil and Gas Exploration and Production Reporting Segment [Member]
Segment Reporting Information [Line Items]
Revenues	1,070		2,389
Gains (losses) on divestitures and other, net	-338		1,460
Oil and Gas Exploration and Production Reporting Segment [Member] | Intersegment Revenues [Member]
Segment Reporting Information [Line Items]
Revenues	1,117		1,553
Oil and Gas Exploration and Production Reporting Segment [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues and other	1,849		5,402
Operating costs and expenses (1)	1,002	[1]	1,012	[1]
Total expenses and other	1,002		1,012
Adjusted EBITDAX	847		4,390
Midstream Reporting Segment [Member]
Segment Reporting Information [Line Items]
Revenues	174		120
Gains (losses) on divestitures and other, net	0		-2
Midstream Reporting Segment [Member] | Intersegment Revenues [Member]
Segment Reporting Information [Line Items]
Revenues	302		320
Midstream Reporting Segment [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues and other	476		438
Operating costs and expenses (1)	240	[1]	232	[1]
Net income attributable to noncontrolling interests	32		43
Total expenses and other	272		275
Adjusted EBITDAX	204		163
Marketing Reporting Segment [Member]
Segment Reporting Information [Line Items]
Revenues	1,341		1,829
Gains (losses) on divestitures and other, net	0		0
Marketing Reporting Segment [Member] | Intersegment Revenues [Member]
Segment Reporting Information [Line Items]
Revenues	-1,191		-1,689
Marketing Reporting Segment [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues and other	150		140
Operating costs and expenses (1)	198	[1]	181	[1]
Total expenses and other	198		181
Adjusted EBITDAX	-47		-39
Marketing Reporting Segment [Member] | Operating Segments [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	$1		$2
[1]	Operating costs and expenses excludes exploration expense, DD&A, impairments, and Deepwater Horizon settlement and related costs since these expenses are excluded from Adjusted EBITDAX.
[2]	Other (income) expense, net excludes certain other nonoperating items since these items are excluded from Adjusted EBITDAX.

Pension_Plans_and_Other_Postre2

Pension Plans and Other Postretirement Benefits (Detail) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Pension Plans, Defined Benefit [Member]
Components of net periodic benefit cost
Service cost	$30	$25
Interest cost	25	25
Expected return on plan assets	-27	-27
Amortization of net actuarial loss (gain)	13	9
Net periodic benefit cost	41	32
Other Postretirement Benefit Plans, Defined Benefit [Member]
Components of net periodic benefit cost
Service cost	3	2
Interest cost	4	4
Expected return on plan assets	0	0
Amortization of net actuarial loss (gain)	0	-2
Net periodic benefit cost	$7	$4