Segment Information - Selected Financial Information for Anadarko's Reporting Segments Table (Detail) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Segment Reporting Information [Line Items]
Sales revenues	$ 3,338	$ 3,236
Other	97	43
Total revenues and other	3,218	3,045
Operating costs and expenses	2,384	2,494
Net cash from settlement of commodity derivatives	(1)	63
Other (income) expense, net	6	(12)
Net income (loss) attributable to noncontrolling interests	111	53
Total expenses and other	1,347	1,426
Consolidated Adjusted EBITDAX	1,873	1,649
Net properties and equipment	28,936		$ 28,615
Capital expenditures	1,296		6,185
Goodwill	4,789		4,789
(Gains) losses on derivatives, net [Member] | Commodity Contract [Member]
Segment Reporting Information [Line Items]
Net cash from settlement of commodity derivatives	(6)	68
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	(3)	6
Excluding Gains Losses On Divestitures Net [Member]
Segment Reporting Information [Line Items]
Total revenues and other	3,223	3,069
Excluding Certain Items [Member]
Segment Reporting Information [Line Items]
Operating costs and expenses	1,240	1,317
Excluding Certain Other Nonoperating Items [Member]
Segment Reporting Information [Line Items]
Other (income) expense, net	2	(12)
Operating Segments [Member] | Exploration and Production [Member]
Segment Reporting Information [Line Items]
Sales revenues	2,666	2,669
Other	8	(9)
Total revenues and other	2,665	2,624
Net income (loss) attributable to noncontrolling interests	0	0
Total expenses and other	992	870
Consolidated Adjusted EBITDAX	1,673	1,787
Net properties and equipment	18,342		18,267
Capital expenditures	922		4,103
Goodwill	4,343		4,343
Operating Segments [Member] | Exploration and Production [Member] | (Gains) losses on derivatives, net [Member] | Commodity Contract [Member]
Segment Reporting Information [Line Items]
Net cash from settlement of commodity derivatives	0	0
Operating Segments [Member] | Exploration and Production [Member] | Gathering, processing, and marketing sales [Member] | Commodity Contract [Member] | Not Designated as Hedging Instrument [Member]
Segment Reporting Information [Line Items]
Total (gains) losses on derivatives, net included in marketing revenue, less net cash from settlement	0	0
Operating Segments [Member] | Exploration and Production [Member] | Excluding Gains Losses On Divestitures Net [Member]
Segment Reporting Information [Line Items]
Total revenues and other	2,665	2,657
Operating Segments [Member] | Exploration and Production [Member] | Excluding Certain Items [Member]
Segment Reporting Information [Line Items]
Operating costs and expenses	992	870
Operating Segments [Member] | Exploration and Production [Member] | Excluding Certain Other Nonoperating Items [Member]
Segment Reporting Information [Line Items]
Other (income) expense, net	0	0
Operating Segments [Member] | WES Midstream [Member]
Segment Reporting Information [Line Items]
Sales revenues	672	502
Other	58	37
Total revenues and other	729	545
Net income (loss) attributable to noncontrolling interests	0	0
Total expenses and other	301	233
Consolidated Adjusted EBITDAX	428	312
Net properties and equipment	8,630		8,410
Capital expenditures	315		1,912
Goodwill	446		446
Operating Segments [Member] | WES Midstream [Member] | (Gains) losses on derivatives, net [Member] | Commodity Contract [Member]
Segment Reporting Information [Line Items]
Net cash from settlement of commodity derivatives	0	0
Operating Segments [Member] | WES Midstream [Member] | Gathering, processing, and marketing sales [Member] | Commodity Contract [Member] | Not Designated as Hedging Instrument [Member]
Segment Reporting Information [Line Items]
Total (gains) losses on derivatives, net included in marketing revenue, less net cash from settlement	0	0
Operating Segments [Member] | WES Midstream [Member] | Excluding Gains Losses On Divestitures Net [Member]
Segment Reporting Information [Line Items]
Total revenues and other	729	545
Operating Segments [Member] | WES Midstream [Member] | Excluding Certain Items [Member]
Segment Reporting Information [Line Items]
Operating costs and expenses	337	233
Operating Segments [Member] | WES Midstream [Member] | Excluding Certain Other Nonoperating Items [Member]
Segment Reporting Information [Line Items]
Other (income) expense, net	(36)	0
Operating Segments [Member] | WES Midstream, Capitalized Cost incurred prior to sale of Midstream Assets [Member]
Segment Reporting Information [Line Items]
Capital expenditures	49		734
Other and Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Sales revenues	0	65
Other	31	15
Total revenues and other	(176)	(124)
Net income (loss) attributable to noncontrolling interests	111	53
Total expenses and other	54	323
Consolidated Adjusted EBITDAX	(228)	(450)
Net properties and equipment	1,964		1,938
Capital expenditures	59		170
Goodwill	0		$ 0
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	(6)	68
Other and Intersegment Eliminations [Member] | Gathering, processing, and marketing sales [Member] | Commodity Contract [Member] | Not Designated as Hedging Instrument [Member]
Segment Reporting Information [Line Items]
Total (gains) losses on derivatives, net included in marketing revenue, less net cash from settlement	(3)	6
Other and Intersegment Eliminations [Member] | Excluding Gains Losses On Divestitures Net [Member]
Segment Reporting Information [Line Items]
Total revenues and other	(171)	(133)
Other and Intersegment Eliminations [Member] | Excluding Certain Items [Member]
Segment Reporting Information [Line Items]
Operating costs and expenses	(89)	214
Other and Intersegment Eliminations [Member] | Excluding Certain Other Nonoperating Items [Member]
Segment Reporting Information [Line Items]
Other (income) expense, net	38	(12)
Oil and Gas [Member]
Segment Reporting Information [Line Items]
Sales revenues	3,126	3,026
Oil and Gas [Member] | Operating Segments [Member] | Exploration and Production [Member]
Segment Reporting Information [Line Items]
Sales revenues	2,606	2,656
Oil and Gas [Member] | Operating Segments [Member] | Exploration and Production [Member] | Intersegment Revenues [Member]
Segment Reporting Information [Line Items]
Sales revenues	51	10
Oil and Gas [Member] | Operating Segments [Member] | WES Midstream [Member]
Segment Reporting Information [Line Items]
Sales revenues	499	355
Oil and Gas [Member] | Operating Segments [Member] | WES Midstream [Member] | Intersegment Revenues [Member]
Segment Reporting Information [Line Items]
Sales revenues	172	153
Oil and Gas [Member] | Other and Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Sales revenues	21	15
Oil and Gas [Member] | Other and Intersegment Eliminations [Member] | Intersegment Revenues [Member]
Segment Reporting Information [Line Items]
Sales revenues	$ (223)	$ (163)