Anadarko Petroleum 10-Q 5 May 14 2014 Q1 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	3 Months Ended
	Mar. 31, 2014	Apr. 30, 2014
Document And Entity Information [Abstract]	'	'
Entity Registrant Name	'ANADARKO PETROLEUM CORP	'
Entity Central Index Key	'0000773910	'
Document Type	'10-Q	'
Document Period End Date	31-Mar-14	'
Amendment Flag	'false	'
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q1	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Large Accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	505,054,104

CONSOLIDATED_STATEMENTS_OF_INC

CONSOLIDATED STATEMENTS OF INCOME (USD $)	3 Months Ended
In Millions, except Per Share data, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Revenues and Other	'	'
Natural-gas sales	$1,217	$807
Oil and condensate sales	2,424	2,377
Natural-gas liquids sales	386	303
Gathering, processing, and marketing sales	311	231
Gains (losses) on divestitures and other, net	1,506	175
Total	5,844	3,893
Costs and Expenses	'	'
Oil and gas operating	313	247
Oil and gas transportation and other	266	255
Exploration	299	264
Gathering, processing, and marketing	252	199
General and administrative	298	275
Depreciation, depletion, and amortization	1,124	1,022
Other taxes	314	280
Impairments	3	29
Algeria exceptional profits tax settlement	0	33
Total	2,869	2,604
Operating Income (Loss)	2,975	1,289
Other (Income) Expense	'	'
Interest expense	183	164
Statement [Line Items]	'	'
(Gains) losses on derivatives, net	461	199
Other (income) expense, net	1	-6
Tronox-related contingent loss	4,300	0
Total	4,937	349
Income (Loss) Before Income Taxes	-1,962	940
Income tax expense (benefit)	664	456
Net Income (Loss)	-2,626	484
Net income attributable to noncontrolling interests	43	24
Net Income (Loss) Attributable to Common Stockholders	-2,669	460
Per Common Share	'	'
Net income (loss) attributable to common stockholders—basic	($5.30)	$0.91
Net income (loss) attributable to common stockholders—diluted	($5.30)	$0.91
Average Number of Common Shares Outstanding—Basic	504	501
Average Number of Common Shares Outstanding—Diluted	504	503
Dividends (per Common Share)	$0.18	$0.09
Commodity Contract and Interest Rate Swap [Member]	'	'
Statement [Line Items]	'	'
(Gains) losses on derivatives, net	$453	$191

CONSOLIDATED_STATEMENTS_OF_COM

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014		Mar. 31, 2013
Statement of Comprehensive Income [Abstract]	'		'
Net Income (Loss)	($2,626)		$484
Other Comprehensive Income (Loss), net of taxes	'		'
Reclassification of previously deferred derivative losses to (gains) losses on derivatives, net (1)	1	[1]	2	[1]
Amortization of net actuarial (gain) loss to general and administrative expense (2)	5	[2]	19	[2]
Total	6		21
Comprehensive Income (Loss)	-2,620		505
Comprehensive income attributable to noncontrolling interests	43		24
Comprehensive Income (Loss) Attributable to Common Stockholders	($2,663)		$481
[1]	Net of income tax benefit (expense) of $(1) million for the three months ended March 31, 2014 and 2013.
[2]	Net of income tax benefit (expense) of $(2) million for the three months ended March 31, 2014, and $(10) million for the three months ended March 31, 2013.

CONSOLIDATED_STATEMENTS_OF_COM1

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Statement of Comprehensive Income [Abstract]	'	'
Reclassification of previously deferred derivative losses to (gains) losses on derivatives, net, tax effect	($1)	($1)
Amortization of net actuarial (gain) loss to general and administrative expense, tax effect	($2)	($10)

CONSOLIDATED_BALANCE_SHEETS

CONSOLIDATED BALANCE SHEETS (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Current Assets	'	'
Cash and cash equivalents	$5,924	$3,698
Accounts receivable (net of allowance of $6 million and $5 million)	'	'
Customers	1,674	1,481
Others	1,375	1,241
Other current assets	691	688
Total	9,664	7,108
Properties and Equipment	'	'
Cost	70,573	71,244
Less accumulated depreciation, depletion, and amortization	30,009	30,315
Net properties and equipment	40,564	40,929
Other Assets	2,278	2,082
Goodwill and Other Intangible Assets	5,597	5,662
Total Assets	58,103	55,781
Current Liabilities	'	'
Accounts payable	3,940	3,530
Current asset retirement obligations	519	409
Accrued expenses	1,320	1,264
Current portion of long-term debt	0	500
Tronox-related contingent liability	5,150	0
Total	10,929	5,703
Long-term Debt	13,569	13,065
Other Long-term Liabilities	'	'
Deferred income taxes	9,343	9,245
Asset retirement obligations	1,573	1,613
Tronox-related contingent liability	0	850
Other	1,772	1,655
Total	12,688	13,363
Stockholders' equity	'	'
Common stock, par value $0.10 per share (1.0 billion shares authorized, 524.0 million and 522.5 million shares issued)	52	52
Paid-in capital	8,682	8,629
Retained earnings	11,595	14,356
Treasury stock (19.2 million and 18.8 million shares)	-930	-895
Accumulated other comprehensive income (loss)	-279	-285
Total Stockholders’ Equity	19,120	21,857
Noncontrolling interests	1,797	1,793
Total Equity	20,917	23,650
Total Liabilities and Equity	$58,103	$55,781

CONSOLIDATED_BALANCE_SHEETS_Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Millions, except Share data, unless otherwise specified
Statement of Financial Position [Abstract]	'	'
Allowance for uncollectible accounts	$6	$5
Common stock, par value	$0.10	$0.10
Common stock, shares authorized	1,000,000,000	1,000,000,000
Common stock, shares issued	524,000,000	522,500,000
Treasury stock, shares	19,200,000	18,800,000

CONSOLIDATED_STATEMENTS_OF_EQU

CONSOLIDATED STATEMENTS 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, 2013	$23,650		$52	$8,629	$14,356	($895)	($285)	$1,793
Net income (loss)	-2,626		'	'	-2,669	'	'	43
Common stock issued	49		'	49	'	'	'	'
Dividends—common stock	-92		'	'	-92	'	'	'
Repurchase of common stock	-35		'	'	'	-35	'	'
Subsidiary equity transactions	16		'	4	'	'	'	12
Distributions to noncontrolling interest owners	-51		'	'	'	'	'	-51
Reclassification of previously deferred derivative losses to (gains) losses on derivatives, net	1	[1]	'	'	'	'	1	'
Adjustments for pension and other postretirement plans	5		'	'	'	'	5	'
Balance at Mar. 31, 2014	$20,917		$52	$8,682	$11,595	($930)	($279)	$1,797
[1]	Net of income tax benefit (expense) of $(1) million for the three months ended March 31, 2014 and 2013.

CONSOLIDATED_STATEMENTS_OF_CAS

CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Cash Flows from Operating Activities	'	'
Net income (loss)	($2,626)	$484
Adjustments to reconcile net income (loss) to net cash provided by operating activities	'	'
Depreciation, depletion, and amortization	1,124	1,022
Deferred income taxes	46	162
Dry hole expense and impairments of unproved properties	198	177
Impairments	3	29
(Gains) losses on divestitures, net	-1,459	-144
Total (gains) losses on derivatives, net	461	199
Net cash from settlement of derivative instruments	-98	47
Other	54	44
Changes in assets and liabilities	'	'
Algeria exceptional profits tax settlement	0	450
Tronox-related contingent loss	4,300	0
(Increase) decrease in accounts receivable	-266	40
Increase (decrease) in accounts payable and accrued expenses	-63	-125
Other items—net	55	118
Net cash provided by (used in) operating activities	1,729	2,503
Cash Flows from Investing Activities	'	'
Additions to properties and equipment and dry hole costs	-2,501	-1,710
Acquisition of businesses	-4	-135
Divestitures of properties and equipment and other assets	3,257	361
Other—net	-170	-133
Net cash provided by (used in) investing activities	582	-1,617
Cash Flows from Financing Activities	'	'
Borrowings, net of issuance costs	918	385
Repayments of debt	-930	0
Increase (decrease) in outstanding checks	97	86
Dividends paid	-92	-46
Repurchase of common stock	-35	-27
Issuance of common stock, including tax benefit on share-based compensation awards	13	18
Sale of subsidiary units	18	'
Sale of subsidiary units	'	-1
Distributions to noncontrolling interest owners	-51	-33
Contributions from noncontrolling interest owners	0	1
Net cash provided by (used in) financing activities	-62	383
Effect of Exchange Rate Changes on Cash	-23	-5
Net Increase (Decrease) in Cash and Cash Equivalents	2,226	1,264
Cash and Cash Equivalents at Beginning of Period	3,698	2,471
Cash and Cash Equivalents at End of Period	$5,924	$3,735

Summary_of_Significant_Account

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2014
Disclosure Text Block [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, crude 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, crude 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 Balance Sheets at March 31, 2014, and December 31, 2013, the Consolidated Statements of Income, Comprehensive Income, and Cash Flows for the three months ended March 31, 2014 and 2013, and the Consolidated Statement of Equity for the three months ended March 31, 2014. 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 accounting principles generally accepted 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) 2014-08, Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity. The ASU changes the criteria for reporting discontinued operations and requires additional disclosures, both for discontinued operations and for individually significant dispositions and assets classified as held for sale not qualifying as discontinued operations. The ASU is effective for annual and interim periods beginning in 2015. Early adoption is permitted for disposals or for assets classified as held for sale that have not been reported in previously issued financial statements. Anadarko elected to early adopt the ASU on a prospective basis for the quarter ended March 31, 2014. The adoption did not have a material impact on the Company’s consolidated financial statements.
	The FASB issued ASU 2013-11, Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists. The ASU requires that an unrecognized tax benefit, or a portion of an unrecognized tax benefit, should be presented in the financial statements as a reduction to a deferred tax asset, except in certain circumstances as described in the ASU. The ASU is effective for annual and interim periods beginning in 2014. See Note 11—Income Taxes.

Divestitures_and_Assets_Held_f

Divestitures and Assets Held for Sale	3 Months Ended
	Mar. 31, 2014
Disclosure Text Block [Abstract]	'
Divestitures and Assets Held for Sale	'
	2. Divestitures and Assets Held for Sale
	Divestitures  During the first quarter of 2014, the Company received $3.3 billion in proceeds and recognized net gains of $1.5 billion, primarily related to the Mozambique and Pinedale/Jonah divestitures. The Company sold a 10% working interest in Rovuma Offshore Area 1 in Mozambique for $2.64 billion and recognized a gain of $1.5 billion. The Company sold its interest in the Pinedale/Jonah assets in Wyoming for $581 million. The Mozambique and Pinedale/Jonah assets were both included in the oil and gas exploration and production reporting segment.
	Assets Held for Sale  The Company is marketing certain domestic and international properties from the oil and gas exploration and production reporting segment to redirect its operating activities and capital investments to other areas. In February 2014, the Company entered into an agreement to sell its Chinese subsidiary for $1.075 billion. The transaction is expected to close later this year and is subject to regulatory approvals and other customary closing conditions. At March 31, 2014, the Company’s Consolidated Balance Sheet included current assets of $206 million, long-term assets of $458 million, current liabilities of $66 million, and long-term liabilities of $49 million associated with assets held for sale, primarily related to its Chinese subsidiary.

Inventories

Inventories	3 Months Ended
	Mar. 31, 2014
Disclosure Text Block [Abstract]	'
Inventories	'
	3. Inventories
	The following summarizes the major classes of inventories included in other current assets:
		March 31,		December 31,
	millions	2014		2013
	Crude oil	$	119	$	88
	Natural gas	2		43
	NGLs	96		79
	Total	$	217	$	210

Suspended_Exploratory_Well_Cos

Suspended Exploratory Well Costs	3 Months Ended
	Mar. 31, 2014
Disclosure Text Block [Abstract]	'
Suspended Exploratory Well Costs	'
	4. Suspended Exploratory Well Costs
	The Company’s suspended exploratory well costs were $1.6 billion at March 31, 2014, and $2.2 billion at December 31, 2013. The decrease in suspended exploratory well costs during 2014 primarily resulted from the Company’s sale of a 10% working interest in Rovuma Offshore Area 1 in Mozambique. Projects with suspended exploratory well costs are those identified by management as exhibiting sufficient quantities of hydrocarbons to justify potential development and which 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, 2014, no exploratory well costs previously capitalized as suspended exploratory well costs for greater than one year at December 31, 2013, were charged to dry hole expense.

Noncontrolling_Interests

Noncontrolling Interests	3 Months Ended
	Mar. 31, 2014
Disclosure Text Block [Abstract]	'
Noncontrolling Interests	'
	5. Noncontrolling Interests
	Western Gas Equity Partners, LP (WGP) is a publicly traded consolidated subsidiary formed to own substantially all of the partnership interests in Western Gas Partners, LP (WES) previously owned by Anadarko. At March 31, 2014, Anadarko’s ownership interest in WGP consisted of a 91.0% limited partner interest and the entire non-economic general partner interest. The remaining limited partner interest in WGP consisted of a 9.0% public ownership interest.
	WES, a publicly traded consolidated subsidiary, is a limited partnership formed by Anadarko to own, operate, acquire, and develop midstream assets. During the three months ended March 31, 2014, WES issued 300,000 common units to the public pursuant to the partial exercise of the underwriters’ over-allotment option granted in connection with WES’s December 2013 equity offering, raising additional net proceeds of $18 million. At March 31, 2014, WGP’s ownership interest in WES consisted of a 41.0% limited partner interest, the entire 2.0% general partner interest, and all WES incentive distribution rights. At March 31, 2014, Anadarko also owned a 0.6% limited partner interest in WES through other subsidiaries. The remaining limited partner interest in WES consisted of a 56.4% public ownership interest.

Derivative_Instruments

Derivative Instruments	3 Months Ended
	Mar. 31, 2014
Disclosure Text Block [Abstract]	'
Derivative Instruments	'
	6. 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).
	6. Derivative Instruments (Continued)
	Interest-rate swaps are used to fix or float interest rates on existing or anticipated indebtedness. The purpose of these instruments is to manage the Company’s existing or anticipated exposure to unfavorable interest-rate changes. The fair value of the Company’s 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 9—Accumulated Other Comprehensive Income (Loss).
	Oil and Natural-Gas Production/Processing Derivative Activities  The natural-gas prices listed below are New York Mercantile Exchange (NYMEX) Henry Hub prices. The crude-oil prices listed below are a combination of NYMEX West Texas Intermediate and IntercontinentalExchange, Inc. (ICE) Brent Blend prices. The following is a summary of the Company’s derivative instruments related to its Oil and Natural-Gas Production/Processing Activities at March 31, 2014:
		2014			2015
		Settlement			Settlement
	Natural Gas
	Three-Way Collars (thousand MMBtu/d)	600			635
	Average price per MMBtu
	Ceiling sold price (call)	$	5.01		$	4.76
	Floor purchased price (put)	$	3.75		$	3.75
	Floor sold price (put)	$	2.75		$	2.75
	Fixed-Price Contracts (thousand MMBtu/d)	600			—
	Average price per MMBtu	$	4.26		$	—
	Extendable Fixed-Price Contracts (thousand MMBtu/d) (1)	400			—
	Average price per MMBtu	$	4.19		$	—
	Crude Oil
	Fixed-Price Contracts (MBbls/d)	107			—
	Average price per barrel	$	100.58		$	—
	__________________________________________________________________
	(1)	The extendable fixed-price contracts have a remaining contract term of April 2014 to June 2014 with an option to extend the contract term to December 2014 at the same price.
	MMBtu—million British thermal units
	MMBtu/d—million British thermal units per day
	MBbls/d—thousand barrels 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 totaling 1 billion cubic feet (Bcf) of natural gas at March 31, 2014, and 16 Bcf at December 31, 2013, that were entered into to mitigate commodity-price risk related to fixed-price purchase and sales contracts and storage activity.
	6. Derivative Instruments (Continued)
	Interest-Rate Derivatives  Anadarko has outstanding interest-rate swap contracts as a fixed-rate payer to mitigate the interest-rate risk associated with anticipated debt issuances. The Company locked in a fixed interest rate in exchange for a floating interest rate indexed to the three-month London Interbank Offered Rate (LIBOR). The 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.
	The Company had the following outstanding interest-rate swaps at March 31, 2014:
	millions except percentages				Reference Period				Weighted-Average
	Notional Principal Amount				Start		End		Interest Rate
	$	750			Jun-14		Jun-24		6.00%
	$	1,100			Jun-14		Jun-44		5.57%
	$	50			Sep-16		Sep-26		5.91%
	$	750			Sep-16		Sep-46		5.86%
	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		2014			2013				2014				2013
	Commodity derivatives
	Other current assets		$	40		$	181			$	(15	)		$	(102	)
	Other assets		23			89				(9		)		(66		)
	Accrued expenses		52			106				(166		)		(149		)
	Other liabilities		1			4				(3		)		(15		)
			116			380				(193		)		(332		)
	Interest-rate and other derivatives
	Accrued expenses		—			—				(628		)		(480		)
	Other liabilities		—			—				(264		)		(174		)
			—			—				(892		)		(654		)
	Total derivatives		$	116		$	380			$	(1,085	)		$	(986	)
	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		2014			2013
	Commodity derivatives
	Gathering, processing, and marketing sales (1)		$	8		$	8
	(Gains) losses on derivatives, net		215			283
	Interest-rate and other derivatives
	(Gains) losses on derivatives, net		238			(92		)
	Total (gains) losses on derivatives, net		$	461		$	199
	__________________________________________________________________
(1)	Represents the effect of marketing and trading derivative activities.
6. Derivative Instruments (Continued)
Credit-Risk Considerations  The financial integrity of exchange-traded contracts, which are subject to nominal credit risk, is assured by NYMEX or ICE through systems of financial safeguards and transaction guarantees. Over-the-counter traded swaps, options, and futures contracts expose the Company to counterparty credit risk. The Company monitors the creditworthiness of its counterparties, establishes credit limits according to the Company’s credit policies and guidelines, and assesses the impact on 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, 2014, $73 million of the Company’s $1.1 billion gross derivative liability balance, and at December 31, 2013, $76 million of the Company’s $986 million 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.
Some of the Company’s derivative instruments are subject to provisions that can require full or partial collateralization or immediate settlement of the Company’s obligations if certain credit-risk-related provisions are triggered. However, most of the Company’s derivative counterparties maintain secured positions with respect to the Company’s derivative liabilities under the Company’s $5.0 billion senior secured revolving credit facility maturing in September 2015 ($5.0 billion Facility).
Unsecured derivative obligations may require immediate settlement or full collateralization if certain credit-risk-related provisions are triggered, such as the Company’s credit rating from major credit rating agencies declining to a level below investment grade. The aggregate fair value of derivative instruments with credit-risk-related contingent features for which a net liability position existed was $77 million (net of collateral) at March 31, 2014, and $42 million (net of collateral) at December 31, 2013. The current portion of these amounts was included in accrued expenses and the long-term portion of these amounts was included in other long-term liabilities—other on the Company’s Consolidated Balance Sheets.
6. Derivative Instruments (Continued)
Fair Value  Fair value of futures contracts is based on quoted prices in active markets for identical assets or liabilities, which represent Level 1 inputs. Valuations of physical-delivery purchase and sale agreements, over-the-counter financial swaps, and commodity option collars are based on similar transactions observable in active markets and industry-standard models that primarily rely on market-observable inputs. Inputs used to estimate the fair value of swaps and options include market-price curves; contract terms and prices; credit-risk adjustments; and, for Black-Scholes option valuations, implied market volatility and discount factors. 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.
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, 2014	Level 1			Level 2				Level 3				Netting (1)				Collateral		Total
Assets
Commodity derivatives
Financial institutions	$	—		$	90			$	—			$	(73	)		$	—	$	17
Other counterparties	—			26				—				(4		)		—		22
Total derivative assets	$	—		$	116			$	—			$	(77	)		$	—	$	39
Liabilities
Commodity derivatives
Financial institutions	$	—		$	(171	)		$	—			$	73			$	13	$	(85	)
Other counterparties	—			(22		)		—				4				—		(18		)
Interest-rate and other derivatives	—			(892		)		—				—				—		(892		)
Total derivative liabilities	$	—		$	(1,085	)		$	—			$	77			$	13	$	(995	)
December 31, 2013
Assets
Commodity derivatives
Financial institutions	$	—		$	211			$	—			$	(153	)		$	—	$	58
Other counterparties	—			169				—				(126		)		—		43
Total derivative assets	$	—		$	380			$	—			$	(279	)		$	—	$	101
Liabilities
Commodity derivatives
Financial institutions	$	—		$	(200	)		$	—			$	153			$	7	$	(40	)
Other counterparties	—			(132		)		—				126				—		(6		)
Interest-rate and other derivatives	—			(654		)		—				—				—		(654		)
Total derivative liabilities	$	—		$	(986	)		$	—			$	279			$	7	$	(700	)
__________________________________________________________________
(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, 2014
Disclosure Text Block [Abstract]	'
Debt and Interest Expense	'
	7. Debt and Interest Expense
	Debt  The Company’s outstanding debt is senior unsecured, except for borrowings, if any, under the $5.0 billion Facility. The following summarizes the Company’s outstanding debt:
		March 31,			December 31,
	millions	2014			2013
	Total debt at face value	$	15,202		$	15,202
	Net unamortized discounts and premiums (1)	(1,641		)	(1,645		)
	Total borrowings	$	13,561		$	13,557
	Capital lease obligation	8			8
	Less current portion of long-term debt	—			500
	Total long-term debt	$	13,569		$	13,065
	__________________________________________________________________
	(1)	Unamortized discounts and premiums are amortized over the term of the related debt.
	Anadarko’s $275 million aggregate principal amount of 5.750% Senior Notes due June 2014 and the Zero-Coupon Senior Notes due 2036, which can be put to the Company in October 2014 (the next potential put date) for up to the then-accreted value of $756 million, 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 interest rates are variable and reflective of market rates. The estimated fair value of the Company’s total borrowings was $15.7 billion at March 31, 2014, and $15.3 billion at December 31, 2013.
	Debt Activity  The following summarizes the Company’s debt activity during the three months ended March 31, 2014:
		Carrying
	millions	Value			Description
	Balance at December 31, 2013	$	13,557
	Issuances	101			WES 2.600% Senior Notes due 2018
		394			WES 5.450% Senior Notes due 2044
	Borrowings	430			WES revolving credit facility
	Repayments	(500		)	7.625% Senior Notes due 2014
		(430		)	WES revolving credit facility
	Other, net	9			Amortization of debt discounts and premiums
	Balance at March 31, 2014	$	13,561
	WES Borrowings  In February 2014, WES entered into a five-year $1.2 billion, expandable to $1.5 billion, senior unsecured revolving credit facility maturing in February 2019 (RCF), which amended and restated its then-existing $800 million senior unsecured revolving credit facility. Borrowings under the RCF bear interest at LIBOR plus an applicable margin ranging from 0.975% to 1.45%, or rates at a margin above the one-month LIBOR, the federal funds rate, or prime rates offered by certain designated banks. During the first quarter of 2014, WES repaid borrowings under its RCF with net proceeds from its public offerings of $100 million aggregate principal amount of 2.600% Senior Notes due 2018 and $400 million aggregate principal amount of 5.450% Senior Notes due 2044. At March 31, 2014, WES was in compliance with all covenants contained in its RCF.
	7. Debt and Interest Expense (Continued)
	Interest Expense  The following summarizes interest expense:
		Three Months Ended
		March 31,
	millions	2014			2013
	Debt and other	$	240		$	232
	Capitalized interest	(57		)	(68		)
	Interest expense	$	183		$	164

Stockholders_Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2014
Disclosure Text Block [Abstract]	'
Stockholders' Equity	'
	8. 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	2014			2013
	Net income (loss)
	Net income (loss) attributable to common stockholders	$	(2,669	)	$	460
	Less undistributed income allocated to participating securities	—			3
	Basic	$	(2,669	)	$	457
	Diluted	$	(2,669	)	$	457
	Shares
	Average number of common shares outstanding—basic	504			501
	Dilutive effect of stock options	—			2
	Average number of common shares outstanding—diluted	504			503
	Excluded (1)	11			4
	Net income (loss) per common share
	Basic	$	(5.30	)	$	0.91
	Diluted	$	(5.30	)	$	0.91
	Dividends per common share	$	0.18		$	0.09
	__________________________________________________________________
	(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, 2014
Disclosure Text Block [Abstract]	'
Accumulated Other Comprehensive Income (Loss)	'
	9. 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, 2013	$	(54	)	$	(231	)	$	(285	)
	Reclassifications to Consolidated Statement of Income	1			5			6
	Balance at March 31, 2014	$	(53	)	$	(226	)	$	(279	)

Contingencies

Contingencies	3 Months Ended
	Mar. 31, 2014
Disclosure Text Block [Abstract]	'
Contingencies	'
	10. Contingencies
	Litigation  The Company is a defendant in a number of lawsuits and is involved in governmental proceedings and regulatory controls arising in the ordinary course of business, including, but not limited to, personal injury 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, with the possible exception of the Tronox Litigation discussed below, the resolution of pending proceedings will not have a material adverse effect on the Company’s consolidated financial position, 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, 2013.
	Tronox Litigation  On November 28, 2005, Tronox Incorporated (Tronox), at the time a subsidiary of Kerr-McGee Corporation, completed an initial public offering (IPO) and was subsequently spun-off from Kerr-McGee Corporation. In August 2006, Anadarko acquired all of the stock of Kerr-McGee Corporation. In January 2009, Tronox and certain of Tronox’s subsidiaries filed voluntary petitions for relief under Chapter 11 of the U.S. Bankruptcy Code in the U.S. Bankruptcy Court for the Southern District of New York (Bankruptcy Court), which is the court that is also hearing the Adversary Proceeding (defined below). In May 2009, Tronox and certain of its affiliates filed a lawsuit against Anadarko and Kerr-McGee Corporation and certain of its subsidiaries (collectively, Kerr-McGee) asserting several claims, including claims for actual and constructive fraudulent conveyance (Adversary Proceeding). Tronox alleged, among other things, that it was insolvent or undercapitalized at the date of its IPO and sought, among other things, to recover damages in excess of $18.85 billion from Kerr-McGee and Anadarko, as well as interest and attorneys’ fees and costs. In accordance with Tronox’s Bankruptcy Court-approved Plan of Reorganization (Plan), the Adversary Proceeding is being pursued by a litigation trust (Litigation Trust). Pursuant to the Plan, the Litigation Trust was “deemed substituted” for the Tronox plaintiffs in the Adversary Proceeding.
	The U.S. government intervened in the Adversary Proceeding, and in May 2009 asserted separate claims against Anadarko and Kerr-McGee under the Federal Debt Collection Procedures Act (FDCPA Complaint). The Litigation Trust and the U.S. government agreed that the recovery of damages under the Adversary Proceeding, if any, would cover both the Adversary Proceeding and the FDCPA Complaint.
	In February 2011, Tronox emerged from bankruptcy pursuant to the Plan. The terms of the Plan, which were confirmed by the Bankruptcy Court in the fourth quarter of 2010, contemplate that the claims of the U.S. government (together with other federal, state, local, and tribal governmental entities having regulatory authority or responsibilities for environmental laws, collectively, the Governmental Entities) related to Tronox’s environmental liabilities and tort claims asserted against Tronox by other creditors will be settled through certain environmental response trusts and the Litigation Trust. The Plan provides for an allocation of any proceeds from the Adversary Proceeding between the Governmental Entities and the other creditors.
	Liability Accrual  On April 3, 2014, Anadarko and Kerr-McGee entered into a settlement agreement with the Litigation Trust and the U.S. government (in its capacity as plaintiff-intervenor and acting for and on behalf of certain U.S. government agencies) to resolve all claims asserted in the Adversary Proceeding and FDCPA Complaint for $5.15 billion, which represents principal of approximately $3.98 billion plus 6% interest from the filing of the Adversary Proceeding on May 12, 2009, through April 3, 2014. In addition, interest will be paid on the above amount from April 3, 2014, through the date of payment of the settlement amount, with interest of 1.5% for the first 180 days and thereafter of 1.5% plus one-month LIBOR. Under the terms of the settlement agreement, the Litigation Trust, Anadarko, and Kerr-McGee have agreed to mutually release all claims that were or could have been asserted in the Adversary Proceeding. The U.S. government (representing federal agencies that filed claims in the Tronox bankruptcy) and Anadarko and Kerr-McGee have also provided covenants not to sue each other with respect to certain claims and causes of action. The U.S. government will also provide contribution protection from third-party claims seeking reimbursement from Anadarko and certain of its affiliates for the sites identified in the settlement agreement.
	10. Contingencies (Continued)
	The settlement agreement is subject to recommendation by the Bankruptcy Court, approval by the U.S. District Court for the Southern District of New York (District Court), and the issuance of an injunction by the District Court barring similar claims from third parties. The Adversary Proceeding has been stayed pending final approval of the settlement agreement. The settlement payment will be made after both the District Court’s approval of the settlement agreement and the issuance of the injunction are final and non-appealable. The Company currently expects this process to be completed during the second half of 2014. Anadarko recognized Tronox-related contingent losses in the Company’s Consolidated Statements of Income of $4.3 billion in the first quarter of 2014 and $850 million in the fourth quarter of 2013, for an aggregate $5.15 billion contingent liability related to the Adversary Proceeding at March 31, 2014. For information on the tax effects of the settlement agreement, see Note 11—Income Taxes.
	Other  In April 2014, the Company’s Board of Directors (Board) received a letter from a purported stockholder demanding that the Board investigate and commence derivative proceedings against certain officers and directors of the Company for alleged breach of fiduciary duty by causing the Company to be liable for damages based on environmental liabilities incurred in connection with the acquisition of Kerr-McGee Corporation. The Board will consider this demand and respond in due course.
	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 fines and penalties, 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, 2013.
	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 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 addresses liability only, and does not address the amount of any civil penalty. The assessment of a civil penalty against Anadarko will follow a bench trial scheduled to begin in January 2015. In August 2012, Anadarko filed a notice of appeal in the U.S. Court of Appeals for the Fifth Circuit (Fifth Circuit) concerning that portion of the February 2012 declaratory judgment finding Anadarko liable for civil penalties under the CWA. The appeal is pending and oral arguments were heard in December 2013. The Fifth Circuit has not yet issued a ruling.
	10. Contingencies (Continued)
	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. For example, eleven Louisiana Parish District Attorneys appealed that decision to the Fifth Circuit. In February 2014, the Fifth Circuit denied the appeal and upheld the Louisiana District Court’s decision. If any further appeal is taken and is successful, state and/or local laws and regulations could become sources of penalties or fines against the Company.
	Applicable accounting guidance requires the Company to accrue a liability if it is probable that a liability is 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. Notwithstanding the declaratory judgment, the Company currently cannot estimate the amount of any potential civil penalty. The CWA sets forth subjective criteria, including degree of fault and history of prior violations, among others, which significantly influence the magnitude of CWA penalty assessments. As a result of the subjective nature of CWA penalty assessments, the Company currently cannot estimate the amount of any such penalty nor determine a range of potential loss. Furthermore, neither the February 2012 settlement by the other nonoperating partner of Deepwater Horizon-related civil penalties (including those under the CWA) with the United States and five affected Gulf states (Texas, Louisiana, Mississippi, Alabama, and Florida) nor the January 2013 settlement of CWA civil and criminal penalties by the drilling contractor with the United States affect the Company’s current conclusion regarding its ability to estimate potential fines and penalties. The Company lacks insight into those settlements, retains legal counsel separate from the other parties, and was not involved in any manner with respect to those settlements. Events or factors that could assist the Company in estimating the amount of any potential civil penalty or a range of potential loss related to such penalties include (i) an assessment by the DOJ, (ii) a ruling by a court of competent jurisdiction, or (iii) the initiation of substantive settlement negotiations between the Company and the DOJ.
	Given the Company’s lack of direct operational involvement in the event, as was confirmed by the Louisiana District Court in August 2011 and reconfirmed by the court in September 2013 and March 2014 by excluding any evidence of Anadarko’s alleged culpability or fault in the Phase I and II trials and in the January 2015 penalty phase trial, and the subjective criteria of the CWA, the Company believes that its exposure to CWA penalties will not materially impact the Company’s consolidated financial position, results of operations, or cash flows.
	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. In March 2012, BP and the Plaintiffs’ Steering Committee entered into a tentative settlement agreement to resolve the substantial majority of economic loss and medical claims stemming from the Deepwater Horizon events, which the Louisiana District Court approved in orders issued in December 2012 and January 2013. Only OPA claims seeking economic loss damages against the Company remain. In addition, certain state and local governments have appealed, or have 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. Certain Mexican states also have appealed the dismissal of their claims against BP, the Company, and others. The Company, pursuant to the Settlement Agreement, is fully indemnified by BP against losses arising as a result of claims for damages, irrespective of whether such claims are based on federal (including OPA) or state law.
	10. Contingencies (Continued)
	The first phase of the trial in the MDL (Phase I) commenced in February 2013. In April 2013, all parties rested their Phase I cases. Findings of fact, post-trial briefs, and responsive briefs were submitted in July 2013. BP, BP p.l.c., the United States, state and local governments, Halliburton Energy Services, Inc. (Halliburton), and Transocean Ltd. (Transocean) participated in Phase I. Anadarko was excused from participation in Phase I. The issues tried in Phase I included the cause of the blow-out and all related events leading up to April 22, 2010, the date the Deepwater Horizon sank, as well as allocation of fault. The allocation of fault remained in the Phase I trial because Halliburton and Transocean have not settled with any of the parties and each wishes to prove to the Louisiana District Court that their respective company was not at fault. Any fault ruling against BP will be binding against it in the penalty phase trial. The second phase of trial (Phase II) began in September 2013 and in November 2013 the parties rested their Phase II cases. 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. The Company, BP, BP p.l.c., the United States, state and local governments, Halliburton, and Transocean participated in Phase II of the trial. The penalty phase of the trial, which is scheduled to begin in January 2015, will include Anadarko, BP, and the United States, and will assess findings and penalties under the CWA. In March 2014, the Louisiana District Court ruled that no evidence of Anadarko’s alleged culpability or fault may be presented during the penalty phase trial.
	Two separate class-action complaints were filed in June and August 2010, in the U.S. District Court for the Southern District of New York on behalf of purported purchasers of the Company’s stock between June 9, 2009, and June 12, 2010, against Anadarko and certain of its officers. The complaints allege causes of action arising pursuant to the Securities Exchange Act of 1934 for purported misstatements and omissions regarding, among other things, the Company’s liability related to the Deepwater Horizon events. The plaintiffs seek an unspecified amount of compensatory damages, including interest thereon, as well as litigation fees and costs. The parties reached a tentative settlement in this matter in March 2014, subject to approval by the court. The tentative settlement amount will be directly funded by the Company’s insurers. As a result, offsetting payables and receivables have been recorded to reflect the impact of the tentative settlement of this matter.
	Remaining Liability Outlook  It is possible that the Company may recognize additional Deepwater Horizon event-related liabilities for potential fines and penalties, shareholder claims, 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 consolidated financial position, 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, BP’s creditworthiness, the merits of the shareholder claims, and directors’ and officers’ insurance coverage related to outstanding shareholder claims.
	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 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, 2014
Disclosure Text Block [Abstract]	'
Income Taxes	'
	11. Income Taxes
	The following summarizes income tax expense (benefit) and effective tax rates:
		Three Months Ended
		March 31,
	millions except percentages	2014			2013
	Income tax expense (benefit)	$	664		$	456
	Effective tax rate	(34		)%	49		%
	The Company reported a loss before income taxes for the three months ended March 31, 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, 2014, was primarily attributable to net changes in uncertain tax positions related to the settlement agreement associated with the Adversary Proceeding, tax expense associated with Algerian exceptional profits taxes, and the tax impact from foreign operations.
	The Company previously recognized a deferred tax benefit of $274 million related to the $850 million loss recognized in 2013 with respect to the Tronox-related contingent liability. In the first quarter of 2014, the Company recognized an additional tax benefit of $282 million related to the additional $4.3 billion loss with respect to the Adversary Proceeding. This benefit is net of a $1.1 billion uncertain tax position due to the uncertainty related to the deductibility of the final settlement payment. This uncertain tax position is presented in deferred income taxes on the Company’s Consolidated Balance Sheet as a reduction to the associated deferred tax asset. The Company is a participant in the Internal Revenue Service’s (IRS) Compliance Assurance Process and has regular discussions with the IRS concerning its 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 materially change. See Note 10—Contingencies—Tronox Litigation.
	The increase from the 35% U.S. federal statutory rate for the three months ended March 31, 2013, was primarily attributable to the tax impact from foreign operations and Algerian exceptional profits taxes.

Supplemental_Cash_Flow_Informa

Supplemental Cash Flow Information	3 Months Ended
	Mar. 31, 2014
Disclosure Text Block [Abstract]	'
Supplemental Cash Flow Information	'
	12. Supplemental Cash Flow Information
	The following summarizes cash paid (received) for interest (net of amounts capitalized) and income taxes, as well as non-cash investing and financing transactions:
		Three Months Ended
		March 31,
	millions	2014		2013
	Cash paid (received)
	Interest	$	265	$	251
	Income taxes	$	598	$	28
	Non-cash investing activities
	Fair value of properties and equipment exchanged in non-cash transactions	$	—	$	13
	Non-cash investing and financing activities
	Floating production, storage, and offloading vessel construction period obligation	$	34	$	—

Segment_Information

Segment Information	3 Months Ended
	Mar. 31, 2014
Disclosure Text Block [Abstract]	'
Segment Information	'
	13. 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, crude 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 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, certain items not related to the Company’s normal operations included Algeria exceptional profits tax settlement and Tronox-related contingent loss. 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	2014			2013
	Income (loss) before income taxes	$	(1,962	)	$	940
	Exploration expense	299			264
	DD&A	1,124			1,022
	Impairments	3			29
	Interest expense	183			164
	Total (gains) losses on derivatives, net, less net cash from settlement of	363			246
	commodity derivatives
	Algeria exceptional profits tax settlement	—			33
	Tronox-related contingent loss	4,300			—
	Less net income attributable to noncontrolling interests	43			24
	Consolidated Adjusted EBITDAX	$	4,267		$	2,674
	13. Segment Information (Continued)
	Information presented below as “Other and Intersegment Eliminations” includes results from hard-minerals royalty arrangements and corporate, financing, and certain derivative activities. 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, 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 (2)	—			—			—			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
	Three Months Ended March 31, 2013
	Sales revenues	$	1,541		$	84		$	2,093		$	—		$	3,718
	Intersegment revenues	1,862			253			(1,966		)	(149		)	—
	Gains (losses) on divestitures and other, net	4			—			—			171			175
	Total revenues and other	3,407			337			127			22			3,893
	Operating costs and expenses (1)	884			188			164			20			1,256
	Net cash from settlement of commodity	—			—			—			(51		)	(51		)
	derivatives
	Other (income) expense, net	—			—			—			(6		)	(6		)
	Net income attributable to noncontrolling interests	—			24			—			—			24
	Total expenses and other	884			212			164			(37		)	1,223
	Total (gains) losses on derivatives, net	—			—			4			—			4
	included in marketing revenue, less net
	cash from settlement
	Adjusted EBITDAX	$	2,523		$	125		$	(33	)	$	59		$	2,674
	__________________________________________________________________
	(1)	Operating costs and expenses excludes exploration expense, DD&A, impairments, and Algeria exceptional profits tax settlement since these expenses are excluded from Adjusted EBITDAX.
	(2)	Other (income) expense, net excludes Tronox-related contingent loss since this expense is excluded from Adjusted EBITDAX.

Pension_Plans_and_Other_Postre

Pension Plans and Other Postretirement Benefits	3 Months Ended
	Mar. 31, 2014
Disclosure Text Block [Abstract]	'
Pension Plans and Other Postretirement Benefits	'
	14. 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	2014			2013			2014			2013
	Three Months Ended March 31
	Service cost	$	25		$	21		$	2		$	2
	Interest cost	25			20			4			4
	Expected return on plan assets	(27		)	(23		)	—			—
	Amortization of net actuarial loss (gain)	9			29			(2		)	—
	Net periodic benefit cost	$	32		$	47		$	4		$	6

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2014
Policy Text Block [Abstract]	'
Use of Estimates	'
	Use of Estimates  The preparation of financial statements in accordance with accounting principles generally accepted 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.

Inventories_Tables

Inventories (Tables)	3 Months Ended
	Mar. 31, 2014
Table Text Block [Abstract]	'
Inventory Disclosure Table	'
	The following summarizes the major classes of inventories included in other current assets:
		March 31,		December 31,
	millions	2014		2013
	Crude oil	$	119	$	88
	Natural gas	2		43
	NGLs	96		79
	Total	$	217	$	210

Derivative_Instruments_Tables

Derivative Instruments (Tables)	3 Months Ended
	Mar. 31, 2014
Table Text Block [Abstract]	'
Schedule of Derivative Instruments	'
	The following is a summary of the Company’s derivative instruments related to its Oil and Natural-Gas Production/Processing Activities at March 31, 2014:
		2014			2015
		Settlement			Settlement
	Natural Gas
	Three-Way Collars (thousand MMBtu/d)	600			635
	Average price per MMBtu
	Ceiling sold price (call)	$	5.01		$	4.76
	Floor purchased price (put)	$	3.75		$	3.75
	Floor sold price (put)	$	2.75		$	2.75
	Fixed-Price Contracts (thousand MMBtu/d)	600			—
	Average price per MMBtu	$	4.26		$	—
	Extendable Fixed-Price Contracts (thousand MMBtu/d) (1)	400			—
	Average price per MMBtu	$	4.19		$	—
	Crude Oil
	Fixed-Price Contracts (MBbls/d)	107			—
	Average price per barrel	$	100.58		$	—
	__________________________________________________________________
	(1)	The extendable fixed-price contracts have a remaining contract term of April 2014 to June 2014 with an option to extend the contract term to December 2014 at the same price.
	MMBtu—million British thermal units
	MMBtu/d—million British thermal units per day
	MBbls/d—thousand barrels per day
	The Company had the following outstanding interest-rate swaps at March 31, 2014:
	millions except percentages				Reference Period				Weighted-Average
	Notional Principal Amount				Start		End		Interest Rate
	$	750			Jun-14		Jun-24		6.00%
	$	1,100			Jun-14		Jun-44		5.57%
	$	50			Sep-16		Sep-26		5.91%
	$	750			Sep-16		Sep-46		5.86%
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		2014			2013				2014				2013
	Commodity derivatives
	Other current assets		$	40		$	181			$	(15	)		$	(102	)
	Other assets		23			89				(9		)		(66		)
	Accrued expenses		52			106				(166		)		(149		)
	Other liabilities		1			4				(3		)		(15		)
			116			380				(193		)		(332		)
	Interest-rate and other derivatives
	Accrued expenses		—			—				(628		)		(480		)
	Other liabilities		—			—				(264		)		(174		)
			—			—				(892		)		(654		)
	Total derivatives		$	116		$	380			$	(1,085	)		$	(986	)
	The following summarizes gains and losses related to derivative instruments:
	millions		Three Months Ended
			March 31,
	Classification of (Gain) Loss Recognized		2014			2013
	Commodity derivatives
	Gathering, processing, and marketing sales (1)		$	8		$	8
	(Gains) losses on derivatives, net		215			283
	Interest-rate and other derivatives
	(Gains) losses on derivatives, net		238			(92		)
	Total (gains) losses on derivatives, net		$	461		$	199
	__________________________________________________________________
	-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, 2014	Level 1			Level 2				Level 3				Netting (1)				Collateral		Total
	Assets
	Commodity derivatives
	Financial institutions	$	—		$	90			$	—			$	(73	)		$	—	$	17
	Other counterparties	—			26				—				(4		)		—		22
	Total derivative assets	$	—		$	116			$	—			$	(77	)		$	—	$	39
	Liabilities
	Commodity derivatives
	Financial institutions	$	—		$	(171	)		$	—			$	73			$	13	$	(85	)
	Other counterparties	—			(22		)		—				4				—		(18		)
	Interest-rate and other derivatives	—			(892		)		—				—				—		(892		)
	Total derivative liabilities	$	—		$	(1,085	)		$	—			$	77			$	13	$	(995	)
	December 31, 2013
	Assets
	Commodity derivatives
	Financial institutions	$	—		$	211			$	—			$	(153	)		$	—	$	58
	Other counterparties	—			169				—				(126		)		—		43
	Total derivative assets	$	—		$	380			$	—			$	(279	)		$	—	$	101
	Liabilities
	Commodity derivatives
	Financial institutions	$	—		$	(200	)		$	—			$	153			$	7	$	(40	)
	Other counterparties	—			(132		)		—				126				—		(6		)
	Interest-rate and other derivatives	—			(654		)		—				—				—		(654		)
	Total derivative liabilities	$	—		$	(986	)		$	—			$	279			$	7	$	(700	)
	__________________________________________________________________
	(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, 2014
Table Text Block [Abstract]	'
Debt Outstanding and Debt Activity Tables	'
	The following summarizes the Company’s outstanding debt:
		March 31,			December 31,
	millions	2014			2013
	Total debt at face value	$	15,202		$	15,202
	Net unamortized discounts and premiums (1)	(1,641		)	(1,645		)
	Total borrowings	$	13,561		$	13,557
	Capital lease obligation	8			8
	Less current portion of long-term debt	—			500
	Total long-term debt	$	13,569		$	13,065
	__________________________________________________________________
	-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, 2014:
		Carrying
	millions	Value			Description
	Balance at December 31, 2013	$	13,557
	Issuances	101			WES 2.600% Senior Notes due 2018
		394			WES 5.450% Senior Notes due 2044
	Borrowings	430			WES revolving credit facility
	Repayments	(500		)	7.625% Senior Notes due 2014
		(430		)	WES revolving credit facility
	Other, net	9			Amortization of debt discounts and premiums
	Balance at March 31, 2014	$	13,561
Interest Expense Table	'
	The following summarizes interest expense:
		Three Months Ended
		March 31,
	millions	2014			2013
	Debt and other	$	240		$	232
	Capitalized interest	(57		)	(68		)
	Interest expense	$	183		$	164

Stockholders_Equity_Tables

Stockholders' Equity (Tables)	3 Months Ended
	Mar. 31, 2014
Table Text Block [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	2014			2013
	Net income (loss)
	Net income (loss) attributable to common stockholders	$	(2,669	)	$	460
	Less undistributed income allocated to participating securities	—			3
	Basic	$	(2,669	)	$	457
	Diluted	$	(2,669	)	$	457
	Shares
	Average number of common shares outstanding—basic	504			501
	Dilutive effect of stock options	—			2
	Average number of common shares outstanding—diluted	504			503
	Excluded (1)	11			4
	Net income (loss) per common share
	Basic	$	(5.30	)	$	0.91
	Diluted	$	(5.30	)	$	0.91
	Dividends per common share	$	0.18		$	0.09
	__________________________________________________________________
	(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, 2014
Table Text Block [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, 2013	$	(54	)	$	(231	)	$	(285	)
	Reclassifications to Consolidated Statement of Income	1			5			6
	Balance at March 31, 2014	$	(53	)	$	(226	)	$	(279	)

Income_Taxes_Tables

Income Taxes (Tables)	3 Months Ended
	Mar. 31, 2014
Table Text Block [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	2014			2013
	Income tax expense (benefit)	$	664		$	456
	Effective tax rate	(34		)%	49		%

Supplemental_Cash_Flow_Informa1

Supplemental Cash Flow Information (Tables)	3 Months Ended
	Mar. 31, 2014
Table Text Block [Abstract]	'
Supplemental Cash Flow Table	'
	The following summarizes cash paid (received) for interest (net of amounts capitalized) and income taxes, as well as non-cash investing and financing transactions:
		Three Months Ended
		March 31,
	millions	2014		2013
	Cash paid (received)
	Interest	$	265	$	251
	Income taxes	$	598	$	28
	Non-cash investing activities
	Fair value of properties and equipment exchanged in non-cash transactions	$	—	$	13
	Non-cash investing and financing activities
	Floating production, storage, and offloading vessel construction period obligation	$	34	$	—

Segment_Information_Tables

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2014
Table Text Block [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	2014			2013
	Income (loss) before income taxes	$	(1,962	)	$	940
	Exploration expense	299			264
	DD&A	1,124			1,022
	Impairments	3			29
	Interest expense	183			164
	Total (gains) losses on derivatives, net, less net cash from settlement of	363			246
	commodity derivatives
	Algeria exceptional profits tax settlement	—			33
	Tronox-related contingent loss	4,300			—
	Less net income attributable to noncontrolling interests	43			24
	Consolidated Adjusted EBITDAX	$	4,267		$	2,674
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, 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 (2)	—			—			—			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
	Three Months Ended March 31, 2013
	Sales revenues	$	1,541		$	84		$	2,093		$	—		$	3,718
	Intersegment revenues	1,862			253			(1,966		)	(149		)	—
	Gains (losses) on divestitures and other, net	4			—			—			171			175
	Total revenues and other	3,407			337			127			22			3,893
	Operating costs and expenses (1)	884			188			164			20			1,256
	Net cash from settlement of commodity	—			—			—			(51		)	(51		)
	derivatives
	Other (income) expense, net	—			—			—			(6		)	(6		)
	Net income attributable to noncontrolling interests	—			24			—			—			24
	Total expenses and other	884			212			164			(37		)	1,223
	Total (gains) losses on derivatives, net	—			—			4			—			4
	included in marketing revenue, less net
	cash from settlement
	Adjusted EBITDAX	$	2,523		$	125		$	(33	)	$	59		$	2,674
	__________________________________________________________________
	(1)	Operating costs and expenses excludes exploration expense, DD&A, impairments, and Algeria exceptional profits tax settlement since these expenses are excluded from Adjusted EBITDAX.
	(2)	Other (income) expense, net excludes Tronox-related contingent loss since this expense is excluded from Adjusted EBITDAX.

Pension_Plans_and_Other_Postre1

Pension Plans and Other Postretirement Benefits (Tables)	3 Months Ended
	Mar. 31, 2014
Table Text Block [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	2014			2013			2014			2013
	Three Months Ended March 31
	Service cost	$	25		$	21		$	2		$	2
	Interest cost	25			20			4			4
	Expected return on plan assets	(27		)	(23		)	—			—
	Amortization of net actuarial loss (gain)	9			29			(2		)	—
	Net periodic benefit cost	$	32		$	47		$	4		$	6

Divestitures_and_Assets_Held_f1

Divestitures and Assets Held for Sale - Divestitures (Detail) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Property, Plant, and Equipment [Line Items]	'	'
Proceeds from divestitures	$3,257	$361
Net gains (losses) on divestitures	1,459	144
Rovuma Offshore Area 1 In Mozambique [Member] | Oil and Gas Exploration and Production Reporting Segment [Member]	'	'
Property, Plant, and Equipment [Line Items]	'	'
Working interest sold	10.00%	'
Proceeds from divestitures	2,640	'
Net gains (losses) on divestitures	1,500	'
Pinedale/Jonah Assets [Member] | Oil and Gas Exploration and Production Reporting Segment [Member]	'	'
Property, Plant, and Equipment [Line Items]	'	'
Proceeds from divestitures	$581	'

Divestitures_and_Assets_Held_f2

Divestitures and Assets Held for Sale - Assets Held for Sale (Details) (Assets Held For Sale [Member], Oil and Gas Exploration and Production Reporting Segment [Member], USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014
Long Lived Assets Held-for-sale [Line Items]	'
Current assets associated with assets held for sale	$206
Long-term assets associated with assets held for sale	458
Current liabilities associated with assets held for sale	66
Long-term liabilities associated with assets held for sale	49
Chinese Subsidiary [Member]	'
Long Lived Assets Held-for-sale [Line Items]	'
Expected proceeds from divestiture	$1,075

Inventories_Detail

Inventories (Detail) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Energy Related Inventory [Abstract]	'	'
Crude oil	$119	$88
Natural gas	2	43
NGLs	96	79
Total	$217	$210

Suspended_Exploratory_Well_Cos1

Suspended Exploratory Well Costs (Detail) (USD $)	3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Capitalized Exploratory Well Costs [Abstract]	'	'
Suspended exploratory well costs	$1,600,000,000	$2,200,000,000
Exploratory well costs previously capitalized as suspended exploratory well costs for greater than one year at December 31, 2013, charged to dry hole expense	$0	'
Rovuma Offshore Area 1 In Mozambique [Member] | Oil and Gas Exploration and Production Reporting Segment [Member]	'	'
Property, Plant, and Equipment [Line Items]	'	'
Working interest sold	10.00%	'

Noncontrolling_Interests_Detai

Noncontrolling Interests (Detail) (USD $)	3 Months Ended
In Millions, except Share data, unless otherwise specified	Mar. 31, 2014
Noncontrolling Interest [Line Items]	'
Net proceeds raised from offering by subsidiary	$18
Western Gas Equity Partners, LP [Member] | Limited Partner [Member]	'
Noncontrolling Interest [Line Items]	'
Ownership interest in subsidiary	91.00%
Public ownership interest in subsidiary	9.00%
Western Gas Partners, LP [Member]	'
Noncontrolling Interest [Line Items]	'
Common units issued to the public	300,000
Net proceeds raised from offering by subsidiary	$18
Western Gas Partners, LP [Member] | Limited Partner [Member]	'
Noncontrolling Interest [Line Items]	'
Public ownership interest in subsidiary	56.40%
Western Gas Partners, LP [Member] | Limited Partner [Member] | Western Gas Equity Partners, LP, Ownership Interest [Member]	'
Noncontrolling Interest [Line Items]	'
Ownership interest in subsidiary	41.00%
Western Gas Partners, LP [Member] | Limited Partner [Member] | Other Anadarko Subsidiaries, Ownership Interest [Member]	'
Noncontrolling Interest [Line Items]	'
Ownership interest in subsidiary	0.60%
Western Gas Partners, LP [Member] | General Partner [Member] | Western Gas Equity Partners, LP, Ownership Interest [Member]	'
Noncontrolling Interest [Line Items]	'
Ownership interest in subsidiary	2.00%

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, 2014
Three-Way Collars Natural Gas 2014 [Member]	'
Derivative [Line Items]	'
Derivative nonmonetary notional amount per day	600,000
Three Way Collars Natural Gas 2015 [Member]	'
Derivative [Line Items]	'
Derivative nonmonetary notional amount per day	635,000
Fixed-Price Contracts Natural Gas 2014 [Member]	'
Derivative [Line Items]	'
Derivative nonmonetary notional amount per day	600,000
Average price per MMBtu or barrel	'
Average price per MMBtu or barrel	4.26
Extendable Fixed-Price Contracts Natural Gas April 2014 to June 2014 [Member]	'
Derivative [Line Items]	'
Derivative nonmonetary notional amount per day	400,000	[1]
Average price per MMBtu or barrel	'
Average price per MMBtu or barrel	4.19
Fixed-Price Contracts Crude Oil 2014 [Member]	'
Derivative [Line Items]	'
Derivative nonmonetary notional amount per day	107
Average price per MMBtu or barrel	'
Average price per MMBtu or barrel	100.58
Call Option [Member] | Short [Member] | Three-Way Collars Natural Gas 2014 [Member]	'
Average price per MMBtu or barrel	'
Average ceiling price	5.01
Call Option [Member] | Short [Member] | Three Way Collars Natural Gas 2015 [Member]	'
Average price per MMBtu or barrel	'
Average ceiling price	4.76
Put Option [Member] | Short [Member] | Three-Way Collars Natural Gas 2014 [Member]	'
Average price per MMBtu or barrel	'
Average floor price	2.75
Put Option [Member] | Short [Member] | Three Way Collars Natural Gas 2015 [Member]	'
Average price per MMBtu or barrel	'
Average floor price	2.75
Put Option [Member] | Long [Member] | Three-Way Collars Natural Gas 2014 [Member]	'
Average price per MMBtu or barrel	'
Average floor price	3.75
Put Option [Member] | Long [Member] | Three Way Collars Natural Gas 2015 [Member]	'
Average price per MMBtu or barrel	'
Average floor price	3.75
[1]	The extendable fixed-price contracts have a remaining contract term of April 2014 to June 2014 with an option to extend the contract term to December 2014 at the same price.

Derivative_Instruments_Additio

Derivative Instruments - Additional Information (Detail) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
	Mcf	Mcf
Revolving Credit Facility [Member] | Revolving Credit Facility 1 [Member]	'	'
Derivative [Line Items]	'	'
Five billion dollar facility	5,000,000,000	'
Securing most derivative counterparties [Member] | Revolving Credit Facility [Member] | Revolving Credit Facility 1 [Member]	'	'
Derivative [Line Items]	'	'
Five billion dollar facility	5,000,000,000	'
Not Designated as Hedging Instrument [Member]	'	'
Derivative [Line Items]	'	'
Gross derivative liability	-1,085,000,000	-986,000,000
Aggregate fair value of derivative instruments with credit-risk-related contingent features for which a net liability position existed, net of collateral	77,000,000	42,000,000
Not Designated as Hedging Instrument [Member] | Permitted to Offset Gross Derivative Asset with Financial Institutions [Member]	'	'
Derivative [Line Items]	'	'
Gross derivative liability	-73,000,000	-76,000,000
Commodity [Member] | Natural Gas [Member] | Not Designated as Hedging Instrument [Member]	'	'
Derivative [Line Items]	'	'
Financial derivative transactions	1,000,000	16,000,000

Derivative_Instruments_Interes

Derivative Instruments - Interest-Rate Derivatives Table (Detail) (Not Designated as Hedging Instrument [Member], USD $)	3 Months Ended
	Mar. 31, 2014
Interest-Rate Swap 1 [Member]	'
Derivative [Line Items]	'
Notional principal amount of interest-rate swap	750,000,000
Weighted-average interest rate for interest-rate swap	6.00%
Interest-Rate Swap 1 [Member] | Minimum [Member]	'
Derivative [Line Items]	'
Reference period for interest-rate swap	1-Jun-14
Interest-Rate Swap 1 [Member] | Maximum [Member]	'
Derivative [Line Items]	'
Reference period for interest-rate swap	1-Jun-24
Interest-Rate Swap 2 [Member]	'
Derivative [Line Items]	'
Notional principal amount of interest-rate swap	1,100,000,000
Weighted-average interest rate for interest-rate swap	5.57%
Interest-Rate Swap 2 [Member] | Minimum [Member]	'
Derivative [Line Items]	'
Reference period for interest-rate swap	1-Jun-14
Interest-Rate Swap 2 [Member] | Maximum [Member]	'
Derivative [Line Items]	'
Reference period for interest-rate swap	1-Jun-44
Interest-Rate Swap 3 [Member]	'
Derivative [Line Items]	'
Notional principal amount of interest-rate swap	50,000,000
Weighted-average interest rate for interest-rate swap	5.91%
Interest-Rate Swap 3 [Member] | Minimum [Member]	'
Derivative [Line Items]	'
Reference period for interest-rate swap	1-Sep-16
Interest-Rate Swap 3 [Member] | Maximum [Member]	'
Derivative [Line Items]	'
Reference period for interest-rate swap	1-Sep-26
Interest-Rate Swap 4 [Member]	'
Derivative [Line Items]	'
Notional principal amount of interest-rate swap	750,000,000
Weighted-average interest rate for interest-rate swap	5.86%
Interest-Rate Swap 4 [Member] | Minimum [Member]	'
Derivative [Line Items]	'
Reference period for interest-rate swap	1-Sep-16
Interest-Rate Swap 4 [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, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Derivatives Fair Value [Line Items]	'	'
Gross derivative assets	$116	$380
Gross derivative liabilities	-1,085	-986
Commodity Derivatives [Member]	'	'
Derivatives Fair Value [Line Items]	'	'
Gross derivative assets	116	380
Gross derivative liabilities	-193	-332
Commodity Derivatives [Member] | Other Current Assets [Member]	'	'
Derivatives Fair Value [Line Items]	'	'
Gross derivative assets	40	181
Gross derivative liabilities	-15	-102
Commodity Derivatives [Member] | Other Assets [Member]	'	'
Derivatives Fair Value [Line Items]	'	'
Gross derivative assets	23	89
Gross derivative liabilities	-9	-66
Commodity Derivatives [Member] | Accrued Expenses [Member]	'	'
Derivatives Fair Value [Line Items]	'	'
Gross derivative assets	52	106
Gross derivative liabilities	-166	-149
Commodity Derivatives [Member] | Other Liabilities [Member]	'	'
Derivatives Fair Value [Line Items]	'	'
Gross derivative assets	1	4
Gross derivative liabilities	-3	-15
Interest-Rate and Other Derivatives [Member]	'	'
Derivatives Fair Value [Line Items]	'	'
Gross derivative assets	0	0
Gross derivative liabilities	-892	-654
Interest-Rate and Other Derivatives [Member] | Accrued Expenses [Member]	'	'
Derivatives Fair Value [Line Items]	'	'
Gross derivative assets	0	0
Gross derivative liabilities	-628	-480
Interest-Rate and Other Derivatives [Member] | Other Liabilities [Member]	'	'
Derivatives Fair Value [Line Items]	'	'
Gross derivative assets	0	0
Gross derivative liabilities	($264)	($174)

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, 2014		Mar. 31, 2013
Derivative [Line Items]	'		'
Total (gains) losses on derivatives, net	$461		$199
Gathering, Processing, and Marketing Sales and Gains (Losses) on Derivatives, Net [Member]	'		'
Derivative [Line Items]	'		'
Total (gains) losses on derivatives, net	461		199
Commodity Derivatives [Member] | Gathering, Processing, and Marketing Sales [Member]	'		'
Derivative [Line Items]	'		'
Total (gains) losses on derivatives, net	8	[1]	8	[1]
Commodity Derivatives [Member] | (Gains) Losses on Derivatives, net [Member]	'		'
Derivative [Line Items]	'		'
Total (gains) losses on derivatives, net	215		283
Interest-Rate and Other Derivatives [Member] | (Gains) Losses on Derivatives, net [Member]	'		'
Derivative [Line Items]	'		'
Total (gains) losses on derivatives, net	$238		($92)
[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, 2014		Dec. 31, 2013
In Millions, unless otherwise specified
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Gross derivative assets	$116		$380
Gross derivative liabilities	-1,085		-986
Derivative assets netting	-77	[1]	-279	[1]
Derivative liabilities netting	77	[1]	279	[1]
Cash collateral from counterparties	0		0
Cash collateral held by counterparties	13		7
Derivative assets	39		101
Derivative liabilities	-995		-700
Commodity Derivatives [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Gross derivative assets	116		380
Gross derivative liabilities	-193		-332
Interest-Rate and Other Derivatives [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Gross derivative assets	0		0
Gross derivative liabilities	-892		-654
Derivative liabilities netting	0	[1]	0	[1]
Cash collateral held by counterparties	0		0
Derivative liabilities	-892		-654
Financial Institutions [Member] | Commodity Derivatives [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Derivative assets netting	-73	[1]	-153	[1]
Derivative liabilities netting	73	[1]	153	[1]
Cash collateral from counterparties	0		0
Cash collateral held by counterparties	13		7
Derivative assets	17		58
Derivative liabilities	-85		-40
Other Counterparties [Member] | Commodity Derivatives [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Derivative assets netting	-4	[1]	-126	[1]
Derivative liabilities netting	4	[1]	126	[1]
Cash collateral from counterparties	0		0
Cash collateral held by counterparties	0		0
Derivative assets	22		43
Derivative liabilities	-18		-6
Fair Value, Inputs, Level 1 [Member] | Recurring [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Gross derivative assets	0		0
Gross derivative liabilities	0		0
Fair Value, Inputs, Level 1 [Member] | Interest-Rate and Other Derivatives [Member] | Recurring [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Gross derivative liabilities	0		0
Fair Value, Inputs, Level 1 [Member] | Financial Institutions [Member] | Commodity Derivatives [Member] | Recurring [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Gross derivative assets	0		0
Gross derivative liabilities	0		0
Fair Value, Inputs, Level 1 [Member] | Other Counterparties [Member] | Commodity Derivatives [Member] | Recurring [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Gross derivative assets	0		0
Gross derivative liabilities	0		0
Fair Value, Inputs, Level 2 [Member] | Recurring [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Gross derivative assets	116		380
Gross derivative liabilities	-1,085		-986
Fair Value, Inputs, Level 2 [Member] | Interest-Rate and Other Derivatives [Member] | Recurring [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Gross derivative liabilities	-892		-654
Fair Value, Inputs, Level 2 [Member] | Financial Institutions [Member] | Commodity Derivatives [Member] | Recurring [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Gross derivative assets	90		211
Gross derivative liabilities	-171		-200
Fair Value, Inputs, Level 2 [Member] | Other Counterparties [Member] | Commodity Derivatives [Member] | Recurring [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Gross derivative assets	26		169
Gross derivative liabilities	-22		-132
Fair Value, Inputs, Level 3 [Member] | Recurring [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Gross derivative assets	0		0
Gross derivative liabilities	0		0
Fair Value, Inputs, Level 3 [Member] | Interest-Rate and Other Derivatives [Member] | Recurring [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Gross derivative liabilities	0		0
Fair Value, Inputs, Level 3 [Member] | Financial Institutions [Member] | Commodity Derivatives [Member] | Recurring [Member]	'		'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'		'
Gross derivative assets	0		0
Gross derivative liabilities	0		0
Fair Value, Inputs, Level 3 [Member] | Other Counterparties [Member] | Commodity Derivatives [Member] | Recurring [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, 2014		Dec. 31, 2013
In Millions, unless otherwise specified
Debt Disclosure [Abstract]	'		'
Total debt at face value	$15,202		$15,202
Net unamortized discounts and premiums (1)	-1,641	[1]	-1,645	[1]
Total borrowings	13,561		13,557
Capital lease obligation	8		8
Less current portion of long-term debt	0		500
Total long-term debt	$13,569		$13,065
[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 $)

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Feb. 25, 2014

Mar. 31, 2014

Mar. 31, 2014

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 2 [Member]

Senior Notes 1 [Member]

Senior Notes Zero Coupon [Member]

Senior Notes Zero Coupon [Member]

Senior Notes 2 [Member]

Senior Notes 3 [Member]

Revolving Credit Facility [Member]

Revolving Credit Facility [Member]

Revolving Credit Facility [Member]

Revolving Credit Facility [Member]

Revolving Credit Facility [Member]

Market Approach Valuation Technique [Member]

Market Approach Valuation Technique [Member]

Senior Notes [Member]

Senior Notes [Member]

Senior Notes [Member]

Senior Notes [Member]

Senior Notes [Member]

Revolving Credit Facility 1 [Member]

Revolving Credit Facility 2 [Member]

Revolving Credit Facility 2 [Member]

Revolving Credit Facility 2 [Member]

Revolving Credit Facility 2 [Member]

Accreted Value At Next Potential Put Date [Member]

Western Gas Partners, LP [Member]

Western Gas Partners, LP [Member]

Western Gas Partners, LP [Member]

Western Gas Partners, LP [Member]

Western Gas Partners, LP [Member]

Western Gas Partners, LP [Member]

Minimum [Member]

Maximum [Member]

London Interbank Offered Rate (LIBOR) [Member]

London Interbank Offered Rate (LIBOR) [Member]

Debt Instrument [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Line of credit, maximum capacity

'

'

'

'

'

'

'

'

'

$5,000,000,000

$1,200,000,000

$800,000,000

'

'

Debt instrument, principal amount

15,202,000,000

15,202,000,000

'

'

275,000,000

'

'

100,000,000

400,000,000

'

'

'

'

'

Debt instrument, stated interest rate

'

'

'

'

5.75%

'

'

2.60%

5.45%

'

'

'

'

'

Debt instrument, maturity date

'

'

'

'

15-Jun-14

10-Oct-36

'

15-Aug-18

1-Apr-44

'

'

'

'

'

Debt Instrument, earliest call date

'

'

'

'

'

10-Oct-14

'

'

'

'

'

'

'

'

Debt instrument, accreted value

13,561,000,000

13,557,000,000

'

'

'

'

756,000,000

'

'

'

'

'

'

'

Estimated fair value of total borrowings

'

'

15,700,000,000

15,300,000,000

'

'

'

'

'

'

'

'

'

'

Line of credit, expandable maximum capacity

'

'

'

'

'

'

'

'

'

'

$1,500,000,000

'

'

'

Line of credit, expiration date

'

'

'

'

'

'

'

'

'

'

26-Feb-19

'

'

'

Margin added to LIBOR

'

'

'

'

'

'

'

'

'

'

'

'

0.98%

1.45%

Debt_and_Interest_Expense_Debt

Debt and Interest Expense - Debt Activity Table (Detail) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014
Debt Disclosure [Abstract]	'
Carrying value, beginning balance	$13,557
Debt Instrument [Line Items]	'
Other, net	9
Carrying value, ending balance	13,561
Senior Notes 2 [Member] | Western Gas Partners, LP [Member] | Senior Notes [Member]	'
Debt Instrument [Line Items]	'
Issuance	101
Debt instrument, stated interest rate	2.60%
Debt instrument, maturity date	15-Aug-18
Senior Notes 3 [Member] | Western Gas Partners, LP [Member] | Senior Notes [Member]	'
Debt Instrument [Line Items]	'
Issuance	394
Debt instrument, stated interest rate	5.45%
Debt instrument, maturity date	1-Apr-44
Revolving Credit Facility 2 [Member] | Western Gas Partners, LP [Member] | Revolving Credit Facility [Member]	'
Debt Instrument [Line Items]	'
Borrowings	430
Repayments	-430
Senior Notes 4 [Member] | Senior Notes [Member]	'
Debt Instrument [Line Items]	'
Repayments of Debt	($500)
Debt instrument, stated interest rate	7.63%
Debt instrument, maturity date	15-Jun-14

Debt_and_Interest_Expense_Inte

Debt and Interest Expense - Interest Expense Table (Detail) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Interest Expense [Abstract]	'	'
Debt and other	$240	$232
Capitalized interest	-57	-68
Interest expense	$183	$164

Stockholders_Equity_Detail

Stockholders' Equity (Detail) (USD $)	3 Months Ended
In Millions, except Per Share data, unless otherwise specified	Mar. 31, 2014		Mar. 31, 2013
Net income (loss)	'		'
Net income (loss) attributable to common stockholders	($2,669)		$460
Less undistributed income allocated to participating securities	0		3
Basic	-2,669		457
Diluted	($2,669)		$457
Shares	'		'
Average number of common shares outstanding—basic	504		501
Dilutive effect of stock options	0		2
Average number of common shares outstanding—diluted	504		503
Excluded (1)	11	[1]	4	[1]
Net income (loss) per common share	'		'
Basic	($5.30)		$0.91
Diluted	($5.30)		$0.91
Dividends per common share	$0.18		$0.09
[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, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]	'
Balance at December 31, 2013	($285)
Reclassifications to Consolidated Statement of Income	6
Balance at March 31, 2014	-279
Interest-rate Derivatives Previously Subject to Hedge Accounting [Member]	'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'
Balance at December 31, 2013	-54
Reclassifications to Consolidated Statement of Income	1
Balance at March 31, 2014	-53
Pension and Other Postretirement Plans [Member]	'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'
Balance at December 31, 2013	-231
Reclassifications to Consolidated Statement of Income	5
Balance at March 31, 2014	($226)

Contingencies_Tronox_Litigatio

Contingencies - Tronox Litigation (Detail) (USD $)	3 Months Ended			3 Months Ended	12 Months Ended		3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2014
				Tronox Litigation [Member]	Tronox Litigation [Member]	Tronox Litigation [Member]	Tronox Litigation [Member]	Tronox Litigation [Member]
				Pending Litigation [Member]	Pending Litigation [Member]	Pending Litigation [Member]	Pending Litigation [Member]	Pending Litigation [Member]
						London Interbank Offered Rate (LIBOR) [Member]	Excluding interest and attorneys' fees and costs [Member]	Principal portion of loss contingency accrual [Member]
Loss Contingencies [Line Items]	'	'	'	'	'	'	'	'
Damages sought, in excess of	'	'	'	'	'	'	$18,850,000,000	'
Tronox-related contingent liability	5,150,000,000	'	0	5,150,000,000	'	'	'	3,980,000,000
Pre-settlement interest rate	'	'	'	6.00%	'	'	'	'
Post-settlement interest rate, first 180 days	'	'	'	1.50%	'	'	'	'
Post-settlement interest rate, after 180 days	'	'	'	'	'	1.50%	'	'
Tronox-related contingent loss	$4,300,000,000	$0	'	$4,300,000,000	$850,000,000	'	'	'

Contingencies_Deepwater_Horizo

Contingencies - Deepwater Horizon Events (Detail) (USD $)	Sep. 30, 2011	Mar. 31, 2014
	Macondo Exploration Well [Member]	Deepwater Horizon [Member]
		BP indemnification liability [Member]
Loss Contingencies [Line Items]	'	'
Anadarko's nonoperated interest	25.00%	'
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, 2014	Mar. 31, 2013
Effective Income Tax Rate Reconciliation, Amount [Abstract]	'	'
Income tax expense (benefit)	$664	$456
Effective tax rate	-34.00%	49.00%

Income_Taxes_Additional_Inform

Income Taxes - Additional Information (Detail) (USD $)	3 Months Ended			12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Dec. 31, 2013
			Tronox Litigation [Member]	Tronox Litigation [Member]
			Pending Litigation [Member]	Pending Litigation [Member]
Income Tax Disclosure [Abstract]	'	'	'	'
U.S. federal statutory rate	35.00%	35.00%	'	'
Income Tax Disclosure [Line Items]	'	'	'	'
Deferred tax benefit	'	'	$282,000,000	$274,000,000
Tronox-related contingent loss	4,300,000,000	0	4,300,000,000	850,000,000
Uncertain tax position	'	'	$1,100,000,000	'

Supplemental_Cash_Flow_Informa2

Supplemental Cash Flow Information (Detail) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Cash paid (received)	'	'
Interest	$265	$251
Income taxes	598	28
Non-cash investing activities	'	'
Fair value of properties and equipment exchanged in non-cash transactions	0	13
Non-cash investing and financing activities	'	'
Floating production, storage, and offloading vessel construction period obligation	$34	$0

Segment_Information_Additional

Segment Information - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2014
	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
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Abstract]	'	'
Income (loss) before income taxes	($1,962)	$940
Exploration expense	299	264
DD&A	1,124	1,022
Impairments	3	29
Interest expense	183	164
Total (gains) losses on derivatives, net, less net cash from settlement of commodity derivatives	363	246
Algeria exceptional profits tax settlement	0	33
Tronox-related contingent loss	4,300	0
Less net income attributable to noncontrolling interests	43	24
Consolidated Adjusted EBITDAX	$4,267	$2,674

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, 2014		Mar. 31, 2013
Segment Reporting Information [Line Items]	'		'
Revenues	$4,338		$3,718
Gains (losses) on divestitures and other, net	1,506		175
Total revenues and other	5,844		3,893
Operating costs and expenses (1)	1,443	[1]	1,256	[1]
Net cash from settlement of commodity derivatives	98		-47
Other (income) expense, net	1		-6
Net income attributable to noncontrolling interests	43		24
Total expenses and other	1,579		1,223
Adjusted EBITDAX	4,267		2,674
(Gains) Losses on Derivatives, net [Member] | Commodity Contract [Member]	'		'
Segment Reporting Information [Line Items]	'		'
Net cash from settlement of commodity derivatives	92		-51
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	2		4
Excluding Certain Other Nonoperating Items [Member]	'		'
Segment Reporting Information [Line Items]	'		'
Other (income) expense, net	1	[2]	-6	[2]
Other and Intersegment Eliminations [Member]	'		'
Segment Reporting Information [Line Items]	'		'
Revenues	0		0
Gains (losses) on divestitures and other, net	48		171
Total revenues and other	-136		22
Operating costs and expenses (1)	18	[1]	20	[1]
Total expenses and other	111		-37
Adjusted EBITDAX	-247		59
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	92		-51
Other and Intersegment Eliminations [Member] | Excluding Certain Other Nonoperating Items [Member]	'		'
Segment Reporting Information [Line Items]	'		'
Other (income) expense, net	1	[2]	-6	[2]
Other and Intersegment Eliminations [Member] | Intersegment Revenues [Member]	'		'
Segment Reporting Information [Line Items]	'		'
Revenues	-184		-149
Oil and Gas Exploration and Production Reporting Segment [Member]	'		'
Segment Reporting Information [Line Items]	'		'
Revenues	2,389		1,541
Gains (losses) on divestitures and other, net	1,460		4
Oil and Gas Exploration and Production Reporting Segment [Member] | Intersegment Revenues [Member]	'		'
Segment Reporting Information [Line Items]	'		'
Revenues	1,553		1,862
Oil and Gas Exploration and Production Reporting Segment [Member] | Operating Segments [Member]	'		'
Segment Reporting Information [Line Items]	'		'
Total revenues and other	5,402		3,407
Operating costs and expenses (1)	1,012	[1]	884	[1]
Total expenses and other	1,012		884
Adjusted EBITDAX	4,390		2,523
Midstream Reporting Segment [Member]	'		'
Segment Reporting Information [Line Items]	'		'
Revenues	120		84
Gains (losses) on divestitures and other, net	-2		0
Midstream Reporting Segment [Member] | Intersegment Revenues [Member]	'		'
Segment Reporting Information [Line Items]	'		'
Revenues	320		253
Midstream Reporting Segment [Member] | Operating Segments [Member]	'		'
Segment Reporting Information [Line Items]	'		'
Total revenues and other	438		337
Operating costs and expenses (1)	232	[1]	188	[1]
Net income attributable to noncontrolling interests	43		24
Total expenses and other	275		212
Adjusted EBITDAX	163		125
Marketing Reporting Segment [Member]	'		'
Segment Reporting Information [Line Items]	'		'
Revenues	1,829		2,093
Gains (losses) on divestitures and other, net	0		0
Marketing Reporting Segment [Member] | Intersegment Revenues [Member]	'		'
Segment Reporting Information [Line Items]	'		'
Revenues	-1,689		-1,966
Marketing Reporting Segment [Member] | Operating Segments [Member]	'		'
Segment Reporting Information [Line Items]	'		'
Total revenues and other	140		127
Operating costs and expenses (1)	181	[1]	164	[1]
Total expenses and other	181		164
Adjusted EBITDAX	-39		-33
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	$2		$4
[1]	Operating costs and expenses excludes exploration expense, DD&A, impairments, and Algeria exceptional profits tax settlement since these expenses are excluded from Adjusted EBITDAX.
[2]	Other (income) expense, net excludes Tronox-related contingent loss since this expense is 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, 2014	Mar. 31, 2013
Pension Plans, Defined Benefit [Member]	'	'
Components of net periodic benefit cost	'	'
Service cost	$25	$21
Interest cost	25	20
Expected return on plan assets	-27	-23
Amortization of net actuarial loss (gain)	9	29
Net periodic benefit cost	32	47
Other Postretirement Benefit Plans, Defined Benefit [Member]	'	'
Components of net periodic benefit cost	'	'
Service cost	2	2
Interest cost	4	4
Expected return on plan assets	0	0
Amortization of net actuarial loss (gain)	-2	0
Net periodic benefit cost	$4	$6