Consolidated Statement of Comprehensive Income (Loss) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Comprehensive income (loss):
Net income (loss)	$ 198	$ 714	$ 193
Cash flow hedging activities:
Net unrealized gain (loss) from derivative instruments, net of taxes of $—, $—, and $1 in 2020, 2019, and 2018, respectively	(2)	0	(7)
Reclassifications into earnings of net derivative instruments (gain) loss, net of taxes of $—, $—, and ($1) in 2020, 2019, and 2018, respectively	1	0	8
Pension and other postretirement benefits:
Net actuarial gain (loss) arising during the year, net of taxes of ($27), ($20), and $3 in 2020, 2019, and 2018, respectively	81	59	(6)
Amortization of actuarial (gain) loss and net actuarial loss from settlements included in net periodic benefit cost (credit), net of taxes of ($7), ($4), and ($11) in 2020, 2019, and 2018, respectively	23	12	35
Other comprehensive income (loss)	103	71	30
Comprehensive income (loss)	301	785	223
Less: Comprehensive income (loss) attributable to noncontrolling interests	(13)	(136)	346
Comprehensive Income (loss) attributable to The Williams Companies, Inc.	$ 314	$ 921	$ (123)