Equity-Based Compensation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions		12 Months Ended
		Dec. 31, 2020		Dec. 31, 2019	Dec. 31, 2018	Apr. 28, 2020
Williams Companies Incentive Plan [Member]
Equity-Based Compensation (Textuals) [Abstract]
Shares authorized for issuance		50,000				10,000
Shares reserved for future issuance		31,000
Shares available for future grants		19,000
Equity-based compensation expense		$ 52		$ 57	$ 54
Tax benefit from equity-based compensation expense		13		$ 14	$ 14
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized [Abstract]
Unrecognized equity-based compensation expense		$ 57
Unrecognized equity-based compensation expense, Weighted-average period of recognition in years		1 year 8 months 12 days
Williams Companies Incentive Plan [Member] | Nonvested Restricted Stock Units [Member]
Equity-Based Compensation (Textuals) [Abstract]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period		3 years
Rollforward of nonvested restricted stock unit activity and related information
Restricted Stock Units, Nonvested shares, Beginning Balance		5,400
Restricted Stock Units, Granted		2,800
Restricted Stock Units, Forfeited		(500)
Restricted Stock Units, Vested		(1,500)
Restricted Stock Units, Nonvested shares, Ending Balance		6,200		5,400
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Restricted Stock Units, Nonvested, Weighted-Average Fair Value, Beginning Balance	[1]	$ 28.11
Weighted-average grant date fair value of restricted stock units granted during the year, per share		18.32	[1]	$ 25.87	$ 30.48
Restricted Stock Units, Forfeited, Weighted-Average Fair Value	[1]	27.90
Restricted Stock Units, Vested, Weighted-Average Fair Value	[1]	29.04
Restricted Stock Units, Nonvested, Weighted-Average Fair Value, Ending Balance	[1]	$ 23.53		$ 28.11
Restricted Stock Units, Vested in Period, Fair Value		$ 43		$ 29	$ 35
Williams Companies Incentive Plan [Member] | Performance Shares [Member]
Rollforward of nonvested restricted stock unit activity and related information
Performance based nonvested restricted stock units as a percent of total nonvested restricted stock units outstanding		41.00%
Williams Companies Incentive Plan [Member] | Performance Shares [Member] | Minimum [Member]
Rollforward of nonvested restricted stock unit activity and related information
Range of vested shares based on extent to which certain financial targets are achieved		0.00%
Williams Companies Incentive Plan [Member] | Performance Shares [Member] | Maximum [Member]
Rollforward of nonvested restricted stock unit activity and related information
Range of vested shares based on extent to which certain financial targets are achieved		200.00%
Williams Companies Incentive Plan [Member] | Stock options [Member]
Rollforward of stock option activity and related information
Options Outstanding, Beginning Balance		6,800
Options, Granted		0
Options, Exercised		(300)
Options, Cancelled		(500)
Options Outstanding, Ending Balance		6,000		6,800
Options Exercisable at Period End		5,700
Options, Aggregate Intrinsic Value, Ending Balance		$ 0
Options, Aggregate Intrinsic Value, Exercisable at Period End		0
Total intrinsic value of options exercised		1		$ 6	3
Tax benefits realized on options exercised		0		1	0
Cash received from the exercise of options		$ 3		$ 4	$ 9
Stock Options Outstanding, Weighted Average Remaining Contractual Life		3 years 6 months
Stock Options Exercisable, Weighted Average Remaining Contractual Life		3 years 3 months 18 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Options, Weighted Average Exercise Price, Beginning Balance		$ 32.64
Options, Weighted Average Exercise Price, Granted		0
Options, Weighted Average Exercise Price, Exercised		17.28
Options, Weighted Average Exercise Price, Cancelled		34.04
Options, Weighted Average Exercise Price, Ending Balance		33.18		$ 32.64
Options, Weighted Average Exercise Price, Exercisable at Period End		$ 33.41
Estimated fair value at date of grant of options for common stock granted
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					4.70%
Volatility					30.10%
Risk-free interest rate					2.70%
Expected life (years)					6 years
Duration Of Base Term For Peer Group Historical Volatility Measurement		10 years
Employee Stock Purchase Plan [Member]
Equity-Based Compensation (Textuals) [Abstract]
Shares authorized for issuance		5,200				1,600
Shares available for future grants		1,700
No. of shares purchases by employees		347
Average price of shares purchased		$ 16.07

[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.