Segment Information - Selected Financial Information for Anadarko's Reporting Segments Table (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016		Dec. 31, 2015
Segment Reporting Information [Line Items]
Sales revenues		$ 10,969	$ 8,447		$ 9,486
Other	[1]	265	179		234
Total revenues and other		11,908	7,869		8,698
Operating costs and expenses		12,580	10,468		17,507
Net cash from settlement of commodity derivatives		(25)	(267)		(335)
Other (income) expense, net		(53)	(101)		154
Net income (loss) attributable to noncontrolling interests	[1]	245	263		(120)
Total expenses and other		5,496	4,559		4,783
Adjusted EBITDAX		5,732	4,075		4,936
Net properties and equipment		27,451	32,168		33,751
Capital expenditures		5,300	3,314		5,888
Goodwill		4,789	5,000		5,395
(Gains) Losses on Derivatives, net [Member] | Commodity Derivatives [Member]
Segment Reporting Information [Line Items]
Net cash from settlement of commodity derivatives		(27)	(265)		(335)
Gathering, Processing, and Marketing Sales [Member] | Commodity Derivatives [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		(6)	8		(1)
Excluding Gains Losses On Divestitures Net [Member]
Segment Reporting Information [Line Items]
Total revenues and other	[2]	11,234	8,626		9,720
Excluding Certain Items [Member]
Segment Reporting Information [Line Items]
Operating costs and expenses	[3]	5,331	4,604		5,111
Excluding Certain Other Nonoperating Items [Member]
Segment Reporting Information [Line Items]
Other (income) expense, net		(53)	(43)	[4]	127	[4]
Other and Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Sales revenues		121	100		83
Other	[1]	67	51		69
Net income (loss) attributable to noncontrolling interests	[1]	245	263		(120)
Total expenses and other		377	(40)		(95)
Adjusted EBITDAX		(913)	(705)		(595)
Net properties and equipment		1,982	1,982		2,112
Capital expenditures		107	79		89
Goodwill		0	0		0
Other and Intersegment Eliminations [Member] | (Gains) Losses on Derivatives, net [Member] | Commodity Derivatives [Member]
Segment Reporting Information [Line Items]
Net cash from settlement of commodity derivatives		(27)	(265)		(335)
Other and Intersegment Eliminations [Member] | Gathering, Processing, and Marketing Sales [Member] | Commodity Derivatives [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		(6)	8		(1)
Other and Intersegment Eliminations [Member] | Excluding Gains Losses On Divestitures Net [Member]
Segment Reporting Information [Line Items]
Total revenues and other	[2]	(530)	(753)		(689)
Other and Intersegment Eliminations [Member] | Excluding Certain Items [Member]
Segment Reporting Information [Line Items]
Operating costs and expenses	[3]	212	5		233
Other and Intersegment Eliminations [Member] | Excluding Certain Other Nonoperating Items [Member]
Segment Reporting Information [Line Items]
Other (income) expense, net		(53)	(43)	[4]	127	[4]
Other and Intersegment Eliminations [Member] | Intersegment Revenues [Member]
Segment Reporting Information [Line Items]
Sales revenues		(718)	(904)		(841)
Exploration and Production Reporting Segment [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales revenues		8,946	7,146		8,250
Other	[1]	15	(5)		40
Net income (loss) attributable to noncontrolling interests	[1]	0	0		0
Total expenses and other		3,555	3,518		3,778
Adjusted EBITDAX		5,429	3,630		4,522
Net properties and equipment		18,598	24,251		25,742
Capital expenditures		3,779	2,685		5,029
Goodwill		4,343	4,550		4,945
Exploration and Production Reporting Segment [Member] | Operating Segments [Member] | (Gains) Losses on Derivatives, net [Member] | Commodity Derivatives [Member]
Segment Reporting Information [Line Items]
Net cash from settlement of commodity derivatives		0	0		0
Exploration and Production Reporting Segment [Member] | Operating Segments [Member] | Gathering, Processing, and Marketing Sales [Member] | Commodity Derivatives [Member] | Not Designated as Hedging Instrument [Member]
Segment Reporting Information [Line Items]
Total (gains) losses on derivatives, net included in marketing revenue, less net cash from settlement		0	0		0
Exploration and Production Reporting Segment [Member] | Operating Segments [Member] | Excluding Gains Losses On Divestitures Net [Member]
Segment Reporting Information [Line Items]
Total revenues and other	[2]	8,984	7,148		8,300
Exploration and Production Reporting Segment [Member] | Operating Segments [Member] | Excluding Certain Items [Member]
Segment Reporting Information [Line Items]
Operating costs and expenses	[3]	3,555	3,518		3,778
Exploration and Production Reporting Segment [Member] | Operating Segments [Member] | Excluding Certain Other Nonoperating Items [Member]
Segment Reporting Information [Line Items]
Other (income) expense, net		0	0	[4]	0	[4]
Exploration and Production Reporting Segment [Member] | Operating Segments [Member] | Intersegment Revenues [Member]
Segment Reporting Information [Line Items]
Sales revenues		23	7		10
WES Midstream Reporting Segment [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales revenues		1,715	1,055		958
Other	[1]	153	114		109
Net income (loss) attributable to noncontrolling interests	[1]	0	0		0
Total expenses and other		1,330	853		818
Adjusted EBITDAX		1,061	1,028		908
Net properties and equipment		5,731	5,050		4,859
Capital expenditures		956	491		525
Goodwill		416	418		388
WES Midstream Reporting Segment [Member] | Operating Segments [Member] | (Gains) Losses on Derivatives, net [Member] | Commodity Derivatives [Member]
Segment Reporting Information [Line Items]
Net cash from settlement of commodity derivatives		0	0		0
WES Midstream Reporting Segment [Member] | Operating Segments [Member] | Gathering, Processing, and Marketing Sales [Member] | Commodity Derivatives [Member] | Not Designated as Hedging Instrument [Member]
Segment Reporting Information [Line Items]
Total (gains) losses on derivatives, net included in marketing revenue, less net cash from settlement		0	0		0
WES Midstream Reporting Segment [Member] | Operating Segments [Member] | Excluding Gains Losses On Divestitures Net [Member]
Segment Reporting Information [Line Items]
Total revenues and other	[2]	2,391	1,881		1,726
WES Midstream Reporting Segment [Member] | Operating Segments [Member] | Excluding Certain Items [Member]
Segment Reporting Information [Line Items]
Operating costs and expenses	[3]	1,330	853		818
WES Midstream Reporting Segment [Member] | Operating Segments [Member] | Excluding Certain Other Nonoperating Items [Member]
Segment Reporting Information [Line Items]
Other (income) expense, net		0	0	[4]	0	[4]
WES Midstream Reporting Segment [Member] | Operating Segments [Member] | Intersegment Revenues [Member]
Segment Reporting Information [Line Items]
Sales revenues		523	712		659
Other Midstream Reporting Segment [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Sales revenues		187	146		195
Other	[1]	30	19		16
Net income (loss) attributable to noncontrolling interests	[1]	0	0		0
Total expenses and other		234	228		282
Adjusted EBITDAX		155	122		101
Net properties and equipment		1,140	885		1,038
Capital expenditures		458	59		245
Goodwill		30	32		62
Other Midstream Reporting Segment [Member] | Operating Segments [Member] | (Gains) Losses on Derivatives, net [Member] | Commodity Derivatives [Member]
Segment Reporting Information [Line Items]
Net cash from settlement of commodity derivatives		0	0		0
Other Midstream Reporting Segment [Member] | Operating Segments [Member] | Gathering, Processing, and Marketing Sales [Member] | Commodity Derivatives [Member] | Not Designated as Hedging Instrument [Member]
Segment Reporting Information [Line Items]
Total (gains) losses on derivatives, net included in marketing revenue, less net cash from settlement		0	0		0
Other Midstream Reporting Segment [Member] | Operating Segments [Member] | Excluding Gains Losses On Divestitures Net [Member]
Segment Reporting Information [Line Items]
Total revenues and other	[2]	389	350		383
Other Midstream Reporting Segment [Member] | Operating Segments [Member] | Excluding Certain Items [Member]
Segment Reporting Information [Line Items]
Operating costs and expenses	[3]	234	228		282
Other Midstream Reporting Segment [Member] | Operating Segments [Member] | Excluding Certain Other Nonoperating Items [Member]
Segment Reporting Information [Line Items]
Other (income) expense, net		0	0	[4]	0	[4]
Other Midstream Reporting Segment [Member] | Operating Segments [Member] | Intersegment Revenues [Member]
Segment Reporting Information [Line Items]
Sales revenues		$ 172	$ 185		$ 172

[1] Presentation has been adjusted to align with the current analysis of segment performance. Net income (loss) attributable to noncontrolling interests, previously reported within the Midstream segment, is now presented within Other and Intersegment Eliminations. Other revenues, previously reported within Other and Intersegment Eliminations, is now presented within the applicable segments.

[2] Total revenues and other excludes gains (losses) on divestitures, net since these gains and losses are excluded from Adjusted EBITDAX.

[3] Operating costs and expenses excludes exploration expense, DD&A, impairments, restructuring charges, and certain other operating expenses since these expenses are excluded from Adjusted EBITDAX.

[4] Other (income) expense, net excludes certain other nonoperating items since these items are excluded from Adjusted EBITDAX.