Variable Interest Entities - Financial Data of WGP (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement of Operations Data
Total revenues and other		$ 11,908	$ 7,869	$ 8,698
Operating income (loss)		(672)	(2,599)	(8,809)
Net Income (Loss)		(211)	(2,808)	(6,812)
Statement of Cash Flow Data
Net cash provided by (used in) operating activities		4,009	3,000	(1,877)
Net cash provided by (used in) investing activities		(1,028)	(2,762)	(4,771)
Net cash provided by (used in) financing activities		(1,613)	2,008	220
Balance Sheet Data
Net property, plant, and equipment		27,451	32,168	33,751
Total assets		42,086	45,564
Long-term debt		15,547	15,281
Total equity and partners’ capital		13,790	15,497	15,457	$ 22,318
Variable Interest Entity, Primary Beneficiary [Member]
Balance Sheet Data
Net property, plant, and equipment		5,731	5,050
WGP [Member]
Balance Sheet Data
Long-term debt	[1]	28	28
WGP [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Statement of Operations Data
Total revenues and other		2,248	1,804	1,752
Operating income (loss)		704	705	154
Net Income (Loss)		573	597	11
Statement of Cash Flow Data
Net cash provided by (used in) operating activities		897	913	783
Net cash provided by (used in) investing activities		(764)	(1,106)	(500)
Net cash provided by (used in) financing activities		(413)	452	$ (250)
Balance Sheet Data
Net property, plant, and equipment		5,731	5,050
Total assets		8,016	7,736
Long-term debt		3,493	3,119
Total liabilities		4,071	3,625
Total equity and partners’ capital		$ 3,945	$ 4,111

[1] Excludes WES.