Debt - Outstanding Debt Table (Detail) - USD ($) $ in Millions		Mar. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Total borrowings at face value		$ 17,754	$ 17,032
Net unamortized discounts, premiums, and debt issuance costs	[1]	(1,580)	(1,574)
Total borrowings	[2]	16,174	15,458
Capital lease obligations		230	231
Less short-term debt		761	142
Total long-term debt		15,643	15,547
Western Gas Partners, LP [Member]
Debt Instrument [Line Items]
Total borrowings at face value		4,220	3,490
Net unamortized discounts, premiums, and debt issuance costs	[1]	(44)	(25)
Total borrowings	[2]	4,176	3,465
Capital lease obligations		0	0
Less short-term debt		0	0
Total long-term debt		4,176	3,465
Western Gas Equity Partners, LP excluding WES [Member]
Debt Instrument [Line Items]
Total borrowings at face value	[3]	28	28
Net unamortized discounts, premiums, and debt issuance costs	[1],[3]	0	0
Total borrowings	[2],[3]	28	28
Capital lease obligations	[3]	0	0
Less short-term debt	[3]	28	0
Total long-term debt	[3]	0	28
Anadarko excluding WES and WGP [Member]
Debt Instrument [Line Items]
Total borrowings at face value	[4]	13,506	13,514
Net unamortized discounts, premiums, and debt issuance costs	[1],[4]	(1,536)	(1,549)
Total borrowings	[2],[4]	11,970	11,965
Capital lease obligations	[4]	230	231
Less short-term debt	[4]	733	142
Total long-term debt	[4]	$ 11,467	$ 12,054

[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.

[4] Excludes WES and WGP.