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Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=wmb_RockyMountainMidstreamHoldingsLLCMember
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Data Type:	na
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General, Description of Business, and Basis of Presentation (Details) - USD ($) $ / shares in Units, $ in Millions			1 Months Ended		3 Months Ended		6 Months Ended	9 Months Ended
	Aug. 10, 2018	Jan. 09, 2017	Feb. 03, 2017	Jan. 31, 2017	Sep. 30, 2018	Sep. 30, 2017	Jun. 30, 2018	Sep. 30, 2018	Sep. 30, 2017	Jul. 30, 2018	Jan. 01, 2018	Dec. 31, 2017	Mar. 31, 2017
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Operating Costs and Expenses					$ 389	$ 403		$ 1,134	$ 1,166
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Changes, Net								(4)
Other Nonoperating Income (Expense)					52	23		99	124
Operating Income (Loss)					(501)	(274)		(1,402)	(1,082)
Net Cash Provided by (Used in) Operating Activities								2,331	2,231
Net Cash Provided by (Used in) Investing Activities								2,983	(662)
Stock Issued During Period, Value, New Issues								35
Additional Paid in Capital, Common Stock					24,680			24,680				$ 18,508
Other Assets, Noncurrent					744			744				619
Accumulated Other Comprehensive Income (Loss), Net of Tax					291			291				238
Stockholders' Equity Attributable to Noncontrolling Interest					(1,349)			(1,349)				(6,519)
Deferred Tax Liabilities, Net, Noncurrent					$ (1,648)			(1,648)				$ (3,147)
Noncontrolling Interest [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Changes, Net								(18)
Stock Issued During Period, Value, New Issues								0
Capital in excess of par value [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Changes, Net								14
Stock Issued During Period, Value, New Issues								$ 0
Financial Repositioning [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Sale of Stock, Number of Shares Issued in Transaction		277,000	59,000,000	289,000,000
Payments to Acquire Limited Partnership Interests		$ 10							56
Sale of Stock, Price Per Share			$ 36.08586
Financial Repositioning [Member] \| Williams Partners L.P. [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Limited Liability Company (LLC) or Limited Partnership (LP), Managing Member or General Partner, Ownership Interest				2.00%
Dividend Reinvestment Program [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Sale of Stock, Number of Shares Issued in Transaction							1,230,657
Sale of Stock, Consideration Received on Transaction							$ 46
Accounting Standards Update 2017-07 [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Operating Costs and Expenses						3			9
Other Nonoperating Income (Expense)						3			9
Operating Income (Loss)						$ 3			9
Accounting Standards Update 2016-15 [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Net Cash Provided by (Used in) Operating Activities									394
Net Cash Provided by (Used in) Investing Activities									$ 394
Accounting Standards Update 2014-09 [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets											$ 121
Reclassification out of Accumulated Other Comprehensive Income [Member] \| Accounting Standards Update 2018-02 [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets											61
Retained Deficit \| Accounting Standards Update 2018-02 [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets											$ (61)
WPZ Merger Agreement [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Limited Partners' Capital Account, Units Outstanding	256,000,000
Stock Issued During Period, Shares, New Issues	382,000,000
Stock Issued During Period, Value, New Issues	$ 382
Additional Paid in Capital, Common Stock	6,112
Other Assets, Noncurrent	33
Accumulated Other Comprehensive Income (Loss), Net of Tax	3
Stockholders' Equity Attributable to Noncontrolling Interest	4,629
Deferred Tax Liabilities, Net, Noncurrent	$ 1,829
Northeast G And P [Member] \| Cardinal Gas Services LLC [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Variable Interest Entity Ownership Percentage								66.00%
Northeast G And P [Member] \| Appalachia Midstream Services, LLC [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Subsidiary of Limited Liability Company or Limited Partnership, Ownership Interest								66.00%
Atlantic Gulf [Member] \| Constitution Pipeline Company LLC [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Variable Interest Entity Ownership Percentage								41.00%
Atlantic Gulf [Member] \| Gulfstar One [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Variable Interest Entity Ownership Percentage								51.00%
Conway Fractionator [Member] \| West [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Subsidiary of Limited Liability Company or Limited Partnership, Ownership Interest								50.00%
Geismar [Member] \| Other [Member]
Subsidiary of Limited Liability Company or Limited Partnership [Line Items]
Subsidiary of Limited Liability Company or Limited Partnership, Ownership Interest									88.50%
Gulfstream Natural Gas System, L.L.C.[Member] \| Atlantic Gulf [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage					50.00%			50.00%
Utica East Ohio Midstream, LLC [Member] \| Northeast G And P [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage					62.00%			62.00%
Delaware Basin Gas Gathering System [Member] \| West [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage													50.00%
Laurel Mountain Midstream, LLC [Member] \| Northeast G And P [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage					69.00%			69.00%
Caiman Energy II [Member] \| Northeast G And P [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage					58.00%			58.00%
Discovery Producer Services LLC [Member] \| Atlantic Gulf [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage					60.00%			60.00%
Overland Pass Pipeline Company LLC [Member] \| West [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage					50.00%			50.00%
Jackalope Gas Gathering Services LLC [Member] \| West [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage					50.00%			50.00%
Rocky Mountain Midstream Holdings LLC [Member] \| West [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage					43.00%			43.00%		40.00%