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

12 Months Ended

Dec. 31, 2017

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, 2017:

Stock Options	Options		Weighted- Average Exercise Price		Aggregate Intrinsic Value
	(Millions)				(Millions)
Outstanding at December 31, 2016	6.2		$	31.32
Granted	1.0		$	28.85
Exercised	(0.5	)	$	21.33
Cancelled	(0.1	)	$	36.75
Outstanding at December 31, 2017	6.6		$	31.53	$	23
Exercisable at December 31, 2017	5.1		$	31.85	$	19

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,
	2017		2016		2015
	(Millions)
Total intrinsic value of options exercised	$	4	$	2	$	37
Tax benefits realized on options exercised	$	1	$	1	$	13
Cash received from the exercise of options	$	7	$	4	$	20

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: 

	2017			2016			2015
Weighted-average grant date fair value of options for our common stock granted during the year, per share	$	6.61		$	7.90		$	7.61
Weighted-average assumptions:
Dividend yield	4.2		%	3.2		%	4.8		%
Volatility	35.1		%	44.7		%	27.8		%
Risk-free interest rate	2.1		%	1.2		%	1.8		%
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, 2017:

Restricted Stock Units Outstanding	Shares		Weighted- Average Fair Value (1)
	(Millions)
Nonvested at December 31, 2016	3.9		$	35.19
Granted	2.0		$	29.47
Forfeited	(0.8	)	$	39.21
Vested	(0.9	)	$	38.30
Nonvested at December 31, 2017	4.2		$	31.02

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(1) Performance-based restricted stock units are valued utilizing a Monte Carlo valuation method using measures of total shareholder return. 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	2017		2016		2015
Weighted-average grant date fair value of restricted stock units granted during the year, per share	$	29.47	$	26.51	$	40.15
Total fair value of restricted stock units vested during the year ($’s in millions)	$	33	$	32	$	42