Earnings (Loss) Per Common Share from Continuing Operations (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Earnings (loss) per common share
Income (loss) from continuing operations available to common stockholders	$ 208	$ 862	$ (156)
Basic weighted-average shares	1,213,631	1,212,037	973,626
Effect of dilutive securities:
Diluted weighted-average shares	1,215,165	1,214,011	973,626	[1]
Earnings (loss) per common share:
Basic	$ 0.17	$ 0.71	$ (0.16)
Diluted	$ 0.17	$ 0.71	$ (0.16)
Nonvested restricted stock units [Member]
Effect of dilutive securities:
Incremental common shares attributable to share-based payment arrangements under effects of dilutive securities item	1,531	1,811	0
Earnings (loss) per common share from continuing operations (Textuals) [Abstract]
Number of weighted-average shares excluded from computation of diluted earnings per common share			2,000
Stock options [Member]
Effect of dilutive securities:
Incremental common shares attributable to share-based payment arrangements under effects of dilutive securities item	3	163	0
Earnings (loss) per common share from continuing operations (Textuals) [Abstract]
Number of weighted-average shares excluded from computation of diluted earnings per common share			500

[1] For the year ended December 31, 2018, 2.0 million weighted-average nonvested restricted stock units and 0.5 million weighted-average stock options have been excluded from the computation of diluted earnings (loss) per common share as their inclusion would be antidilutive due to our loss from continuing operations attributable to The Williams Companies, Inc.