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

12 Months Ended

Dec. 31, 2018

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

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, 2018:

Stock Options	Options		Weighted- Average Exercise Price		Aggregate Intrinsic Value
	(Millions)				(Millions)
Outstanding at December 31, 2017	6.6		$	31.53
Granted	1.3		$	29.09
Exercised	(0.4	)	$	23.06
Cancelled	(0.2	)	$	31.45
Outstanding at December 31, 2018	7.3		$	31.55	$	6
Exercisable at December 31, 2018	5.3		$	32.63	$	6

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:

	Years Ended December 31,
	2018		2017		2016
	(Millions)
Total intrinsic value of options exercised	$	3	$	4	$	2
Tax benefits realized on options exercised	$	—	$	1	$	1
Cash received from the exercise of options	$	9	$	7	$	4

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			2017			2016
Weighted-average grant date fair value of options for our common stock granted during the year, per share	$	5.49		$	6.61		$	7.90
Weighted-average assumptions:
Dividend yield	4.7		%	4.2		%	3.2		%
Volatility	30.1		%	35.1		%	44.7		%
Risk-free interest rate	2.7		%	2.1		%	1.2		%
Expected life (years)	6.0			6.0			6.0

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, 2018:

Restricted Stock Units Outstanding	Shares		Weighted- Average Fair Value (1)
	(Millions)
Nonvested at December 31, 2017	4.2		$	31.02
Granted	1.7		$	30.48
Forfeited	(0.5	)	$	32.97
Vested	(0.9	)	$	39.30
Nonvested at December 31, 2018	4.5		$	28.96

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(1) Performance-based restricted stock units are valued considering measures of total shareholder return, utilizing a Monte Carlo valuation method, and return on capital employed. 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	2018		2017		2016
Weighted-average grant date fair value of restricted stock units granted during the year, per share	$	30.48	$	29.47	$	26.51
Total fair value of restricted stock units vested during the year ($s in millions)	$	35	$	33	$	32