Investing Activities (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended	12 Months Ended
		Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 20, 2012	Jun. 30, 2013
Schedule of Investments [Line Items]
Gain on remeasurement of equity-method investment					$ 0	$ 2,544	$ 0
Impairment of equity-method investments					1,359	0	0
Equity earnings (losses)					335	144	134
Investment Income, Nonoperating					27	43	81
Equity Method Investments		$ 7,336			7,336	8,400
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity		2,400			2,400	3,700
Equity Method Investment, payments to purchase or contributions					595	482	455
Equity method investment, dividends or distributions					633	440	247
Special distribution from equity-method investment					396	0	0
Contribution to equity-method investment for repayment of debt					248	0	0
Special distribution repayable to equity-method investment		149			149	0
Summarized Financial Position of Equity Method Investments
Current assets		773			773	599
Noncurrent assets		9,549			9,549	9,135
Current liabilities		(633)			(633)	(850)
Noncurrent liabilities		(1,450)			(1,450)	(954)
Summarized Results of Operations of Equity Method Investments
Gross revenue					1,707	1,623	2,406
Operating income					690	534	699
Net income					611	460	627
Delaware Basin Gas Gathering System [Member]
Schedule of Investments [Line Items]
Equity Method Investments		$ 977			$ 977	1,478
Equity Method Investment, Ownership Percentage		50.00%			50.00%
Equity Method Investment, payments to purchase or contributions					$ 57	20	0
Equity method investment, dividends or distributions					33	0	0
Appalachia Midstream Investments [Member]
Schedule of Investments [Line Items]
Equity Method Investments	[1]	$ 2,464			$ 2,464	3,033
Equity Method Investment, Ownership Percentage		45.00%			45.00%
Equity Method Investment, payments to purchase or contributions					$ 93	84	0
Equity method investment, dividends or distributions					219	130	0
Utica East Ohio Midstream, LLC [Member]
Schedule of Investments [Line Items]
Equity Method Investments	[2]	$ 1,525			$ 1,525	1,411
Equity Method Investment, Ownership Percentage		62.00%			62.00%
Equity Method Investment, payments to purchase or contributions	[3]				$ 357	57	0
Equity method investment, dividends or distributions					42	0	0
Discovery Producer Services LLC [Member]
Schedule of Investments [Line Items]
Equity Method Investments		$ 602			$ 602	602
Equity Method Investment, Ownership Percentage		60.00%			60.00%
Equity Method Investment, payments to purchase or contributions					$ 35	106	193
Equity method investment, dividends or distributions					116	36	12
Laurel Mountain Midstream, LLC [Member]
Schedule of Investments [Line Items]
Equity Method Investments		$ 391			$ 391	459
Equity Method Investment, Ownership Percentage		69.00%			69.00%
Equity method investment, dividends or distributions					$ 31	39	0
Overland Pass Pipeline Company LLC [Member]
Schedule of Investments [Line Items]
Equity Method Investments		$ 445			$ 445	453
Equity Method Investment, Ownership Percentage		50.00%			50.00%
Equity method investment, dividends or distributions					$ 45	27	27
Caiman Energy II, LLC [Member]
Schedule of Investments [Line Items]
Equity Method Investments		$ 418			$ 418	432
Equity Method Investment, Ownership Percentage		58.00%			58.00%
Equity Method Investment, payments to purchase or contributions					$ 0	175	192
Equity method investment, dividends or distributions					33	13	0
Gulfstream Natural Gas System, L.L.C.[Member]
Schedule of Investments [Line Items]
Equity Method Investments		$ 293			$ 293	317
Equity Method Investment, Ownership Percentage		50.00%			50.00%
Equity method investment, dividends or distributions					$ 88	81	81
Special distribution from equity-method investment					396
Contribution to equity-method investment for repayment of debt					248
Special distribution repayable to equity-method investment		$ 149			149
Access Midstream Partners [Member]
Schedule of Investments [Line Items]
Equity earnings (losses)						(7)	93
Income (loss) from investments							$ 31
Equity Method Investment, Ownership Percentage							23.00%		24.00%
Equity Method Investment, payments to purchase or contributions								$ 2,190
Equity method investment, dividends or distributions					0	64	$ 93
Access Midstream Partners [Member] | Adjustment For Amortization Of Difference Between Carrying Amount And Underlying Equity [Member]
Schedule of Investments [Line Items]
Equity earnings (losses)				$ (30)			(63)
Other [Member]
Schedule of Investments [Line Items]
Equity Method Investments		221			221	215
Equity Method Investment, payments to purchase or contributions					53	40	70
Equity method investment, dividends or distributions					26	50	34
Bluegrass Pipeline [Member]
Schedule of Investments [Line Items]
Equity earnings (losses)						(67)
Moss Lake [Member]
Schedule of Investments [Line Items]
Equity earnings (losses)						(4)
Former Venezuela Operations [Member]
Schedule of Investments [Line Items]
Investment Income, Nonoperating					27	41	$ 50
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			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			$ 300
Additional Investment [Member] | Utica East Ohio Midstream, LLC [Member]
Schedule of Investments [Line Items]
Equity Method Investment, Ownership Percentage		13.00%			13.00%
Access Midstream Partners Acquisition [Member]
Schedule of Investments [Line Items]
Gain on remeasurement of equity-method investment						2,544
Access Midstream Partners Acquisition [Member] | Income Loss From Equity Method Investment [Member]
Schedule of Investments [Line Items]
Business Combination, Integration Related Costs						$ 19
Williams Partners L.P. [Member] | Income Loss From Equity Method Investment [Member] | Appalachia Midstream Investments [Member]
Schedule of Investments [Line Items]
Equity earnings (losses)					$ (19)
Williams Partners L.P. [Member] | Impairment Of Equity-Method Investments [Member] | Delaware Basin Gas Gathering System [Member]
Schedule of Investments [Line Items]
Impairment of equity-method investments		$ 45	$ 458
Williams Partners L.P. [Member] | Impairment Of Equity-Method Investments [Member] | Appalachia Midstream Investments [Member]
Schedule of Investments [Line Items]
Impairment of equity-method investments		559	$ 3
Williams Partners L.P. [Member] | Impairment Of Equity-Method Investments [Member] | Utica East Ohio Midstream, LLC [Member]
Schedule of Investments [Line Items]
Impairment of equity-method investments		241
Williams Partners L.P. [Member] | Impairment Of Equity-Method Investments [Member] | Laurel Mountain Midstream, LLC [Member]
Schedule of Investments [Line Items]
Impairment of equity-method investments		$ 45

[1] Includes equity-method investments in multiple gathering systems in the Marcellus Shale with an approximate average 45 percent interest.

[2] WPZ acquired an approximate 13 percent additional interest in UEOM in 2015. (See Note 2 – Acquisitions).

[3] 2015 includes additional interest in UEOM acquired by WPZ. (See Note 2 – Acquisitions.)