Divestitures (Details) - USD ($) $ in Millions			3 Months Ended						12 Months Ended
		Jul. 06, 2017	Dec. 31, 2018	Jun. 30, 2018	Sep. 30, 2017	Jun. 30, 2017	Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Nov. 30, 2018	Oct. 01, 2018	Oct. 26, 2017
Income (Loss) from Individually Significant Component Disposed of, Attributable to Parent, before Income Tax [Abstract]
Gain on sale of certain assets									$ 692	$ 1,095	$ 0
Impairment Of Certain Assets [Member]
Income (Loss) from Individually Significant Component Disposed of, Attributable to Parent, before Income Tax [Abstract]
Tangible Asset Impairment Charges											873
Impairment Of Certain Assets [Member] | Fair Value, Measurements, Nonrecurring [Member]
Income (Loss) from Individually Significant Component Disposed of, Attributable to Parent, before Income Tax [Abstract]
Tangible Asset Impairment Charges	[1]								0	23	70
Impairment Of Certain Assets [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member]
Income (Loss) from Individually Significant Component Disposed of, Attributable to Parent, before Income Tax [Abstract]
Tangible Asset Impairment Charges											803
Impairment Of Certain Assets [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member] | West [Member]
Income (Loss) from Individually Significant Component Disposed of, Attributable to Parent, before Income Tax [Abstract]
Tangible Asset Impairment Charges	[2]							$ 48
Gulf Coast Pipeline Systems [Member]
Income Statement and Additional Disclosures by Disposal Groups [Line Items]
Disposal Group, Consideration												$ 177
Income (Loss) from Individually Significant Component Disposed of, Attributable to Parent, before Income Tax [Abstract]
Gain on sale of certain assets			$ 101
Gulf Coast Pipeline Systems [Member] | Atlantic Gulf [Member]
Income (Loss) from Individually Significant Component Disposed of, Attributable to Parent, before Income Tax [Abstract]
Gain on sale of certain assets			81
Gulf Coast Pipeline Systems [Member] | Other [Member]
Income (Loss) from Individually Significant Component Disposed of, Attributable to Parent, before Income Tax [Abstract]
Gain on sale of certain assets			20
Gulf Coast Pipeline Systems [Member] | Disposal Group, Not Discontinued Operations [Member] | Impairment Of Certain Assets [Member] | Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 2 [Member]
Income (Loss) from Individually Significant Component Disposed of, Attributable to Parent, before Income Tax [Abstract]
Tangible Asset Impairment Charges				$ 66
Gulf Coast Pipeline Systems [Member] | Disposal Group, Not Discontinued Operations [Member] | Impairment Of Certain Assets [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member]
Income (Loss) from Individually Significant Component Disposed of, Attributable to Parent, before Income Tax [Abstract]
Tangible Asset Impairment Charges					$ 68	$ 23
Four Corners [Member] | West [Member]
Income Statement and Additional Disclosures by Disposal Groups [Line Items]
Disposal Group, Consideration													$ 1,125
Income (Loss) from Individually Significant Component Disposed of, Attributable to Parent, before Income Tax [Abstract]
Income (Loss) before Income Taxes of Disposal Group									(52)	(47)	(37)
Income (Loss) before Income Taxes of Disposal Group Attributable to the Williams Companies, Inc.									(43)	(35)	(23)
Gain on sale of certain assets			$ 591
Williams Olefins, L.L.C. [Member]
Income Statement and Additional Disclosures by Disposal Groups [Line Items]
Disposal Group, Consideration		$ 2,084												$ 12
Income (Loss) from Individually Significant Component Disposed of, Attributable to Parent, before Income Tax [Abstract]
Gain (Loss) on Disposition of Business					$ 1,095
Williams Olefins, L.L.C. [Member] | Disposal Group, Not Discontinued Operations [Member]
Income (Loss) from Individually Significant Component Disposed of, Attributable to Parent, before Income Tax [Abstract]
Income (Loss) before Income Taxes of Disposal Group									0	(26)	(141)
Income (Loss) before Income Taxes of Disposal Group Attributable to the Williams Companies, Inc.									$ 0	$ (19)	(85)
Canadian Operations [Member] | Disposal Group, Not Discontinued Operations [Member]
Income Statement and Additional Disclosures by Disposal Groups [Line Items]
Disposal Group, Consideration							$ 1,020
Divested cash of disposal group							$ 31
Income (Loss) from Individually Significant Component Disposed of, Attributable to Parent, before Income Tax [Abstract]
Income (Loss) before Income Taxes of Disposal Group											98
Income (Loss) before Income Taxes of Disposal Group Attributable to the Williams Companies, Inc.											95
Canadian Operations [Member] | Disposal Group, Not Discontinued Operations [Member] | Other income (expense) - net [Member]
Income Statement and Additional Disclosures by Disposal Groups [Line Items]
Loss on sale of Canadian operations (Note 3)											66
Gain (Loss) on Foreign Currency Derivative Instruments Not Designated as Hedging Instruments											15
Canadian Operations [Member] | Disposal Group, Not Discontinued Operations [Member] | Impairment Of Certain Assets [Member] | Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member]
Income Statement and Additional Disclosures by Disposal Groups [Line Items]
Disposal Group, Not Discontinued Operation, Loss (Gain) on Write-down											$ 747
Variable Interest Term Loan due 2018 [Member] | Williams Olefins, L.L.C. [Member]
Income (Loss) from Individually Significant Component Disposed of, Attributable to Parent, before Income Tax [Abstract]
Extinguishment of Debt, Amount		$ 850

[1] Reflects multiple individually insignificant impairments and write-downs of other certain assets that may no longer be in use or are surplus in nature for which the fair value was determined to be lower than the carrying value.

[2] Relates to certain gathering assets within the Mid-Continent region. The estimated fair value was determined by a market approach based on our analysis of observable inputs in the principal market.