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Commitments, Guarantees and Contingencies - Narrative (Details) T in Millions			9 Months Ended	12 Months Ended
	Jul. 21, 2021 USD ($)	Feb. 20, 2018 USD ($)	Sep. 30, 2021 USD ($) phase T	Dec. 31, 2019 USD ($)
Guarantor Obligations [Line Items]
Outstanding guarantees and other assurances aggregated			$ 1,100,000,000
Company posted collateral related to net liability positions			$ 55,000,000
Goal to reduce in GHG emissions			30.00%
Amount of code of conduct payment				$ 4,000,000
Regulation of Waste Disposal
Guarantor Obligations [Line Items]
Accrual for environmental loss contingencies			$ 101,000,000
Environmental liabilities former gas facilities			$ 67,000,000
National Ambient Air Quality Standards
Guarantor Obligations [Line Items]
Capping of SO2 Emissions Under CSAPR \| T			2.4
Capping of NOx emissions under CSAPR \| T			1.2
National Ambient Air Quality Standards \| CSAPR
Guarantor Obligations [Line Items]
Number of phases under the EPA’s CAIR for reductions of Sulfur Dioxide and Mono-Nitrogen Oxides \| phase			2
Global Holding \| Senior Secured Term Loan \| Senior Loans \| Signal Peak, Global Rail and Affiliates
Guarantor Obligations [Line Items]
Investment ownership percentage			69.99%
FEV \| Senior Secured Term Loan \| Senior Loans \| Signal Peak \| Global Holding
Guarantor Obligations [Line Items]
Investment ownership percentage			33.33%
WMB Marketing Ventures, LLC \| Senior Secured Term Loan \| Senior Loans \| Signal Peak \| Global Holding
Guarantor Obligations [Line Items]
Investment ownership percentage			33.33%
FE
Guarantor Obligations [Line Items]
Outstanding guarantees and other assurances aggregated			$ 586,000,000
Other Guarantee
Guarantor Obligations [Line Items]
Outstanding guarantees and other assurances aggregated			68,000,000
Other Assurances
Guarantor Obligations [Line Items]
Outstanding guarantees and other assurances aggregated			469,000,000
Term Loan Facility due November 2024 \| Line of Credit \| Global Holding
Guarantor Obligations [Line Items]
Face amount of debt			$ 120,000,000
EPA \| Clean Water Act
Guarantor Obligations [Line Items]
Amount awarded to other party		$ 610,000
Term of payments		2 years
U.S. Attorney's Office \| United States v. Householder, et al.
Guarantor Obligations [Line Items]
Term of payments	60 days
Term of DPA	3 years
Loss in period	$ 230,000,000
United States Treasury \| United States v. Householder, et al.
Guarantor Obligations [Line Items]
Amount awarded to other party	115,000,000
Ohio Development Service \| United States v. Householder, et al.
Guarantor Obligations [Line Items]
Amount awarded to other party	$ 115,000,000