Debt - Outstanding Debt Table (Detail) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Total borrowings at face value	$ 19,433	$ 17,661
Net unamortized discounts, premiums, and debt issuance costs	(1,465)	(1,492)
Total borrowings	17,968	16,169
Finance lease liabilities	261	248
Less short-term debt	31	947
Total long-term debt	18,198	15,470
WES [Member]
Debt Instrument [Line Items]
Total borrowings at face value	7,540	4,868
Net unamortized discounts, premiums, and debt issuance costs	(51)	(53)
Total borrowings	7,489	4,815
Finance lease liabilities	0	0
Less short-term debt	0	28
Total long-term debt	7,489	4,787
Anadarko [Member]
Debt Instrument [Line Items]
Total borrowings at face value	11,893	12,793
Net unamortized discounts, premiums, and debt issuance costs	(1,414)	(1,439)
Total borrowings	10,479	11,354
Finance lease liabilities	261	248
Less short-term debt	31	919
Total long-term debt	$ 10,709	$ 10,683