Investing Activities (Details) - USD ($) $ in Millions		3 Months Ended	12 Months Ended
		Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 15, 2018	Sep. 30, 2018	Mar. 31, 2017
Schedule of Investments [Line Items]
Impairment of equity-method investments (Note 17)			$ 32	$ 0	$ 430
Equity earnings (losses)			396	434	397
Investment income, nonoperating			219	282	63
Gain on sale of equity-method investment			0	269	27
Equity-method investments			7,821	6,552
Gain on deconsolidation of businesses (Note 6)			203	0	0
Proceeds from dispositions of equity-method investments			0	200	34
Equity-method investment, difference between carrying amount and underlying equity			1,800	1,800
Equity-method investment, payments to purchase or contributions			1,132	132	177
Distributions from unconsolidated affiliates			693	784	742
Summarized Financial Position of Equity Method Investments
Current assets			834	447
Noncurrent assets			13,199	9,181
Current liabilities			(605)	(295)
Noncurrent liabilities			(2,491)	(1,538)
Summarized Results of Operations of Equity Method Investments
Gross revenue			2,411	1,961	1,883
Operating income			804	871	799
Net income			795	806	726
Rocky Mountain Midstream Holdings LLC [Member]
Schedule of Investments [Line Items]
Equity-method investments			$ 776	0
Equity-method investment, ownership percentage			50.00%					40.00%
Equity-method investment, payments to purchase or contributions			$ 795	0	0
Jackalope Gas Gathering Services LLC [Member]
Schedule of Investments [Line Items]
Equity-method investments			$ 343	0
Equity-method investment, ownership percentage			50.00%
Equity-method investment, payments to purchase or contributions			$ 42	0	0
Caiman Energy II [Member]
Schedule of Investments [Line Items]
Equity-method investments			$ 412	429
Equity-method investment, ownership percentage			58.00%
Equity-method investment, payments to purchase or contributions			$ 0	24	22
Distributions from unconsolidated affiliates			46	49	40
Delaware Basin Gas Gathering System [Member]
Schedule of Investments [Line Items]
Equity-method investment, payments to purchase or contributions			0	32	105
Distributions from unconsolidated affiliates			0	39	39
Appalachia Midstream Investments [Member]
Schedule of Investments [Line Items]
Gain on sale of equity-method investment					27
Equity-method investments	[1]		$ 3,218	3,104
Equity-method investment, ownership percentage			66.00%
Equity-method investment, payments to purchase or contributions			$ 246	70	28
Distributions from unconsolidated affiliates			297	270	211
Utica East Ohio Midstream, LLC [Member]
Schedule of Investments [Line Items]
Equity-method investments			$ 1,293	1,383
Equity-method investment, ownership percentage			62.00%
Distributions from unconsolidated affiliates			$ 70	80	92
Discovery Producer Services LLC [Member]
Schedule of Investments [Line Items]
Equity-method investments			$ 507	534
Equity-method investment, ownership percentage			60.00%
Equity-method investment, payments to purchase or contributions			$ 5	1	0
Distributions from unconsolidated affiliates			45	127	141
Laurel Mountain Midstream, LLC [Member]
Schedule of Investments [Line Items]
Equity-method investments			$ 314	309
Equity-method investment, ownership percentage			69.00%
Equity-method investment, payments to purchase or contributions			$ 16	0	0
Distributions from unconsolidated affiliates			23	32	28
Overland Pass Pipeline Company LLC [Member]
Schedule of Investments [Line Items]
Equity-method investments			$ 415	422
Equity-method investment, ownership percentage			50.00%
Distributions from unconsolidated affiliates			$ 73	68	69
Gulfstream Natural Gas System, L.L.C.[Member]
Schedule of Investments [Line Items]
Equity-method investments			$ 225	244
Equity-method investment, ownership percentage			50.00%
Distributions from unconsolidated affiliates			$ 93	92	100
Special distribution from equity-method investment						$ 396
Contribution to equity-method investment for repayment of debt					148	248
Brazos Permian II, LLC [Member]
Schedule of Investments [Line Items]
Equity-method investments			$ 191	0
Equity-method investment, ownership percentage			15.00%
Equity-method investment, payments to purchase or contributions			$ 27	0	0
Other [Member]
Schedule of Investments [Line Items]
Equity-method investments			127	127
Equity-method investment, payments to purchase or contributions			1	5	22
Distributions from unconsolidated affiliates			46	27	22
Former Venezuela Operations [Member]
Schedule of Investments [Line Items]
Investment income, nonoperating					36
Total Equity Method Investment [Member]
Schedule of Investments [Line Items]
Distributions from unconsolidated affiliates			$ 693	784	742
Equity-Method Investment Debt Due November 1, 2015 [Member] | Gulfstream Natural Gas System, L.L.C.[Member]
Schedule of Investments [Line Items]
Equity-method investment debt						$ 500
Equity-Method Investment Debt Due June 1, 2016 [Member] | Gulfstream Natural Gas System, L.L.C.[Member]
Schedule of Investments [Line Items]
Equity-method investment debt					300
Northeast G And P [Member] | Caiman Energy II [Member]
Schedule of Investments [Line Items]
Equity-method investment, ownership percentage			58.00%
Northeast G And P [Member] | Appalachia Midstream Services, LLC [Member]
Schedule of Investments [Line Items]
Equity-method investment, ownership percentage			66.00%
Northeast G And P [Member] | Appalachia Midstream Investments [Member]
Schedule of Investments [Line Items]
Impairment of equity-method investments (Note 17)			$ 0	0	294
Northeast G And P [Member] | Utica East Ohio Midstream, LLC [Member]
Schedule of Investments [Line Items]
Impairment of equity-method investments (Note 17)			$ 32	0	0
Equity-method investment, ownership percentage			62.00%
Northeast G And P [Member] | Laurel Mountain Midstream, LLC [Member]
Schedule of Investments [Line Items]
Impairment of equity-method investments (Note 17)			$ 0	0	50
Equity-method investment, ownership percentage			69.00%
West [Member] | Rocky Mountain Midstream Holdings LLC [Member]
Schedule of Investments [Line Items]
Equity-method investment, ownership percentage			50.00%
West [Member] | Jackalope Gas Gathering Services LLC [Member]
Schedule of Investments [Line Items]
Goodwill, Period Increase (Decrease)		$ 47
Equity-method investment, ownership percentage			50.00%
Gain on deconsolidation of businesses (Note 6)			$ 62
West [Member] | Delaware Basin Gas Gathering System [Member]
Schedule of Investments [Line Items]
Impairment of equity-method investments (Note 17)			$ 0	0	59
Gain on sale of equity-method investment				269
Equity-method investment, ownership percentage									50.00%
Proceeds from dispositions of equity-method investments				155
West [Member] | Overland Pass Pipeline Company LLC [Member]
Schedule of Investments [Line Items]
Equity-method investment, ownership percentage			50.00%
West [Member] | Brazos Permian II, LLC [Member]
Schedule of Investments [Line Items]
Equity-method investment, ownership percentage			15.00%
Gain on deconsolidation of businesses (Note 6)			$ 141
West [Member] | Ranch Westex JV LLC [Member]
Schedule of Investments [Line Items]
Impairment of equity-method investments (Note 17)			0	0	24
Proceeds from dispositions of equity-method investments				45
Corporate and Other [Member] | Other [Member]
Schedule of Investments [Line Items]
Impairment of equity-method investments (Note 17)			$ 0	$ 0	$ 3
Brazos Permian II, LLC [Member] | West [Member]
Schedule of Investments [Line Items]
Investments, Fair Value Disclosure							$ 192
Jackalope Gas Gathering Services LLC [Member] | West [Member]
Schedule of Investments [Line Items]
Investments, Fair Value Disclosure		$ 310
Appalachia Midstream Services, LLC [Member] | Northeast G And P [Member]
Schedule of Investments [Line Items]
Investments, Fair Value Disclosure									$ 1,100
Measurement Input, Discount Rate [Member] | Jackalope Gas Gathering Services LLC [Member] | West [Member]
Schedule of Investments [Line Items]
Property Plant And Equipment And Intangibles Fair Value Inputs		10.90%
Measurement Input, Discount Rate [Member] | Appalachia Midstream Services, LLC [Member] | Northeast G And P [Member]
Schedule of Investments [Line Items]
Property Plant And Equipment And Intangibles Fair Value Inputs									9.50%

[1] Includes equity-method investments in multiple gathering systems in the Marcellus Shale with an approximate average 66 percent interest.