Equity-Based Compensation (Tables) - Williams Companies Incentive Plan [Member]

12 Months Ended

Dec. 31, 2020

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Nonvested Restricted Stock Unit Rollforward and related information [Table Text Block]

The following summary reflects nonvested restricted stock unit activity and related information for the year ended December 31, 2020:

Restricted Stock Units Outstanding	Shares	Weighted- Average Fair Value (1)
	(Millions)
Nonvested at December 31, 2019	5.4	$	28.11
Granted	2.8	$	18.32
Forfeited	(0.5)	$	27.90
Vested	(1.5)	$	29.04
Nonvested at December 31, 2020	6.2	$	23.53

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(1)Performance-based restricted stock units are valued considering measures of total shareholder return utilizing a Monte Carlo valuation method, as well as return on capital employed and a ratio of debt to EBITDA. All other restricted stock units are valued at the grant-date market price. Restricted stock units generally vest after three years.

Other restricted stock unit information [Table Text Block]

Value of Restricted Stock Units	2020		2019		2018
Weighted-average grant date fair value of restricted stock units granted during the year, per share	$	18.32	$	25.87	$	30.48
Total fair value of restricted stock units vested during the year (in millions)	$	43	$	29	$	35

Stock Option Rollfoward and related information [Table Text Block]

The following summary reflects stock option activity and related information for the year ended December 31, 2020:

Stock Options	Options	Weighted- Average Exercise Price		Aggregate Intrinsic Value
	(Millions)			(Millions)
Outstanding at December 31, 2019	6.8	$	32.64
Granted	—	$	—
Exercised	(0.3)	$	17.28
Cancelled	(0.5)	$	34.04
Outstanding at December 31, 2020	6.0	$	33.18	$	—
Exercisable at December 31, 2020	5.7	$	33.41	$	—

Cash Proceeds Received and Tax Benefit from Share-based Payment Awards [Table Text Block]

The following table summarizes additional information related to stock option activity during each of the last three years:

	Year Ended December 31,
	2020		2019		2018
	(Millions)
Total intrinsic value of options exercised	$	1	$	6	$	3
Tax benefits realized on options exercised	$	—	$	1	$	—
Cash received from the exercise of options	$	3	$	4	$	9

Stock Options Schedule of Valuation Assumptions [Table Text Block]

The estimated fair value at date of grant of options for our common stock granted in each respective year, using the Black-Scholes option pricing model, is as follows:

	2018
Weighted-average grant date fair value of options for our common stock granted during the year, per share	$	5.49
Weighted-average assumptions:
Dividend yield	4.7		%
Volatility	30.1		%
Risk-free interest rate	2.7		%
Expected life (years)	6.0