Fair Value Measurements and Guarantees Nonrecurring Measurements (Details) - USD ($) $ in Millions			1 Months Ended	3 Months Ended			6 Months Ended
		Mar. 31, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Share Price Change			26.00%			40.00%
Goodwill, Impairment Loss				$ 0	$ 0		$ 0	$ 187
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Equity Method Investment, Other than Temporary Impairment				$ 0	$ 0		0	938
Impairment Of Equity-Method Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Equity Method Investment, Other than Temporary Impairment							$ 0	$ 938
Fair Value, Nonrecurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Goodwill, Impairment Loss						$ 187
Williams Companies Inc [Member] | Appalachia Midstream Services, LLC [Member] | Fair Value, Nonrecurring [Member] | Level 3 [Member] | Northeast G And P [Member] | Impairment Of Equity-Method Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Equity Method Investment, Other than Temporary Impairment	[1]	$ 127
Williams Companies Inc [Member] | Appalachia Midstream Services, LLC [Member] | Fair Value, Nonrecurring [Member] | Level 3 [Member] | Northeast G And P [Member] | Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Investments, Fair Value Disclosure	[1]	2,700	$ 2,700			2,700
Rocky Mountain Midstream Holdings LLC [Member] | Fair Value, Nonrecurring [Member] | Level 3 [Member] | West [Member] | Impairment Of Equity-Method Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Equity Method Investment, Other than Temporary Impairment	[2]	243
Rocky Mountain Midstream Holdings LLC [Member] | Fair Value, Nonrecurring [Member] | Level 3 [Member] | West [Member] | Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Investments, Fair Value Disclosure	[2]	$ 557	$ 557			$ 557
Rocky Mountain Midstream Holdings LLC [Member] | Measurement Input, Discount Rate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Investments Fair Value Inputs		17.00%	17.00%			17.00%
Brazos Permian II LLC [Member] | Fair Value, Nonrecurring [Member] | Level 3 [Member] | West [Member] | Impairment Of Equity-Method Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Equity Method Investment, Other than Temporary Impairment	[2]	$ 193
Brazos Permian II LLC [Member] | Fair Value, Nonrecurring [Member] | Level 3 [Member] | West [Member] | Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Investments, Fair Value Disclosure	[2]	$ 0	$ 0			$ 0
Brazos Permian II LLC [Member] | Measurement Input, Discount Rate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Investments Fair Value Inputs		17.00%	17.00%			17.00%
Caiman Energy II [Member] | Fair Value, Nonrecurring [Member] | Level 3 [Member] | Northeast G And P [Member] | Impairment Of Equity-Method Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Equity Method Investment, Other than Temporary Impairment	[1]	$ 229
Caiman Energy II [Member] | Fair Value, Nonrecurring [Member] | Level 3 [Member] | Northeast G And P [Member] | Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Investments, Fair Value Disclosure	[1]	191	$ 191			$ 191
Aux Sable Liquid Products LP [Member] | Fair Value, Nonrecurring [Member] | Level 3 [Member] | Northeast G And P [Member] | Impairment Of Equity-Method Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Equity Method Investment, Other than Temporary Impairment	[1]	39
Aux Sable Liquid Products LP [Member] | Fair Value, Nonrecurring [Member] | Level 3 [Member] | Northeast G And P [Member] | Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Investments, Fair Value Disclosure	[1]	7	7			7
Laurel Mountain Midstream, LLC [Member] | Fair Value, Nonrecurring [Member] | Level 3 [Member] | Northeast G And P [Member] | Impairment Of Equity-Method Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Equity Method Investment, Other than Temporary Impairment	[1]	10
Laurel Mountain Midstream, LLC [Member] | Fair Value, Nonrecurring [Member] | Level 3 [Member] | Northeast G And P [Member] | Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Investments, Fair Value Disclosure	[1]	236	236			236
Discovery Producer Services LLC [Member] | Fair Value, Nonrecurring [Member] | Level 3 [Member] | Transmission And Gulf Of Mexico [Member] | Impairment Of Equity-Method Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Equity Method Investment, Other than Temporary Impairment	[1]	97
Discovery Producer Services LLC [Member] | Fair Value, Nonrecurring [Member] | Level 3 [Member] | Transmission And Gulf Of Mexico [Member] | Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Investments, Fair Value Disclosure	[1]	$ 367	$ 367			$ 367
Minimum [Member] | Caiman Energy II And Aux Sable Liquid Products LP [Member] | Measurement Input, EBITDA Multiple [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Investments Fair Value Inputs		500.00%	500.00%			500.00%
Minimum [Member] | Appalachia Midstream Services LLC And Laurel Mountain Midstream LLC And Discovery Producer Services LLC [Member] | Measurement Input, Discount Rate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Investments Fair Value Inputs		9.70%	9.70%			9.70%
Maximum [Member] | Caiman Energy II And Aux Sable Liquid Products LP [Member] | Measurement Input, EBITDA Multiple [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Investments Fair Value Inputs		620.00%	620.00%			620.00%
Maximum [Member] | Appalachia Midstream Services LLC And Laurel Mountain Midstream LLC And Discovery Producer Services LLC [Member] | Measurement Input, Discount Rate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Investments Fair Value Inputs		13.50%	13.50%			13.50%
Weighted Average [Member] | Caiman Energy II And Aux Sable Liquid Products LP [Member] | Measurement Input, EBITDA Multiple [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Investments Fair Value Inputs		600.00%	600.00%			600.00%
Weighted Average [Member] | Appalachia Midstream Services LLC And Laurel Mountain Midstream LLC And Discovery Producer Services LLC [Member] | Measurement Input, Discount Rate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]
Investments Fair Value Inputs		12.60%	12.60%			12.60%
Noncontrolling Interests
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Goodwill, Impairment Loss						$ 65

[1] Following the previously described declining market conditions during the first quarter of 2020, we evaluated these investments for other-than-temporary impairment. The impairments within our Northeast G&P segment are primarily associated with operations in wet-gas areas where producer drilling activities are influenced by NGL prices which historically trend with crude oil prices. The fair values of our investments in Caiman II and Aux Sable Liquid Products LP (Aux Sable) were estimated using a market approach, reflecting valuation multiples ranging from 5.0x to 6.2x EBITDA (weighted-average 6.0x). The fair values of the other investments, including gathering systems that are part of Appalachia Midstream Investments, were estimated using an income approach, with discount rates ranging from 9.7 percent to 13.5 percent (weighted-average 12.6 percent). We also considered any debt held at the investee level, and its impact to fair value. The assumed valuation multiples and industry weighted-average discount rates utilized were both significantly influenced by the market declines previously discussed.

[2] Following the previously described declining market conditions during the first quarter of 2020, we evaluated these investments for other-than-temporary impairment. The fair value was measured using an income approach. Both investees operate in primarily oil-driven basins where significant expected reductions in producer activities led to reduced estimates of expected future cash flows. Our fair value estimates also reflected discount rates of approximately 17 percent for these investments. We also considered any debt held at the investee level, and its impact to fair value. The industry weighted-average discount rates utilized were significantly influenced by the market declines previously discussed.