Debt - Debt Activity Table (Detail) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
Feb. 28, 2019	Mar. 31, 2019
Changes in Debt Outstanding [Roll Forward]
Balance at December 31, 2018		$ 16,169
Other, net		13
Balance at March 31, 2019		17,674
Anadarko excluding WES [Member]
Changes in Debt Outstanding [Roll Forward]
Balance at December 31, 2018		11,354
Other, net		12
Balance at March 31, 2019		10,466
Western Midstream Partners, LP [Member]
Changes in Debt Outstanding [Roll Forward]
Balance at December 31, 2018		4,815
Other, net		1
Balance at March 31, 2019		7,208
WES 364-Day Facility [Member]
Changes in Debt Outstanding [Roll Forward]
Borrowings, credit facility		2,000
WES 364-Day Facility [Member] \| Western Midstream Partners, LP [Member]
Changes in Debt Outstanding [Roll Forward]
Borrowings, credit facility	$ 2,000	2,000
WES RCF [Member]
Changes in Debt Outstanding [Roll Forward]
Borrowings, credit facility		420
WES RCF [Member] \| Western Midstream Partners, LP [Member]
Changes in Debt Outstanding [Roll Forward]
Borrowings, credit facility		420
WGP RCF [Member]
Changes in Debt Outstanding [Roll Forward]
Repayments, credit facility		(28)
WGP RCF [Member] \| Western Midstream Partners, LP [Member]
Changes in Debt Outstanding [Roll Forward]
Repayments, credit facility		(28)
8.700 % Senior Notes due 2019 [Member]
Changes in Debt Outstanding [Roll Forward]
Repayments, senior notes		$ (600)
Debt instrument, stated interest rate		8.70%
8.700 % Senior Notes due 2019 [Member] \| Anadarko excluding WES [Member]
Changes in Debt Outstanding [Roll Forward]
Repayments, senior notes		$ (600)
6.950% Senior Notes due 2019 [Member]
Changes in Debt Outstanding [Roll Forward]
Repayments, senior notes		$ (300)
Debt instrument, stated interest rate		6.95%
6.950% Senior Notes due 2019 [Member] \| Anadarko excluding WES [Member]
Changes in Debt Outstanding [Roll Forward]
Repayments, senior notes		$ (300)

Changes in Debt Outstanding [Roll Forward]

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- Definition

Amount of amortization expense attributable to debt discount (premium) and debt issuance costs.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28555-108399

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
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- Definition

Represents the aggregate of total long-term debt, including current maturities and short-term debt.

+ References

No definition available.

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- Definition

Amount of cash inflow from contractual arrangement with the lender, including but not limited to, letter of credit, standby letter of credit and revolving credit arrangements.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
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- Definition

The cash outflow during the period from the repayment of aggregate short-term and long-term debt. Excludes payment of capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3291-108585

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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-Section 45
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