Debt - Outstanding Debt Table (Detail) - USD ($) $ in Millions		Sep. 30, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Total borrowings at face value		$ 16,921	$ 16,706
Net unamortized discounts, premiums, and debt issuance costs	[1]	(1,589)	(1,628)
Total borrowings	[2]	15,332	15,078
Capital lease obligations		241	245
Less short-term debt	[3]	149	42
Total long-term debt		15,424	15,281
Western Gas Partners, LP [Member]
Debt Instrument [Line Items]
Total borrowings at face value		3,370	3,120
Net unamortized discounts, premiums, and debt issuance costs	[1]	(26)	(29)
Total borrowings	[2]	3,344	3,091
Capital lease obligations		0	0
Less short-term debt		0	0
Total long-term debt		3,344	3,091
Western Gas Equity Partners, LP excluding WES [Member]
Debt Instrument [Line Items]
Total borrowings at face value	[4]	28	28
Net unamortized discounts, premiums, and debt issuance costs	[1],[4]	0	0
Total borrowings	[2],[4]	28	28
Capital lease obligations	[4]	0	0
Less short-term debt	[4]	0	0
Total long-term debt	[4]	28	28
Anadarko excluding WES and WGP [Member]
Debt Instrument [Line Items]
Total borrowings at face value	[5]	13,523	13,558
Net unamortized discounts, premiums, and debt issuance costs	[1],[5]	(1,563)	(1,599)
Total borrowings	[2],[5]	11,960	11,959
Capital lease obligations	[5]	241	245
Less short-term debt	[5]	149	42
Total long-term debt	[5]	$ 12,052	$ 12,162

[1] Unamortized discounts, premiums, and debt issuance costs are amortized over the term of the related debt. Debt issuance costs related to RCFs are included in other current assets and other assets on the Company’s Consolidated Balance Sheets.

[2] The Company’s outstanding borrowings, except for borrowings under the WGP RCF, are senior unsecured.

[3] Excludes WES and WGP.

[4] Excludes WES.

[5] Excludes WES and WGP.