Summary of Significant Accounting Policies and Other Matters - Investments (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2021	Feb. 28, 2021
Stagecoach Gas Services LLC
Schedule of Equity Method Investments [Line Items]
Goodwill, impairment loss	$ 343
Stagecoach Gas Services LLC
Schedule of Equity Method Investments [Line Items]
Goodwill, impairment loss	172
Equity method investments	667	$ 839
Goodwill, impairment loss, after-tax	$ 120
Stagecoach Gas Services LLC
Schedule of Equity Method Investments [Line Items]
Ownership percentage	50.00%

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount after tax of loss recognized that results from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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