Commitments and Contingencies - Schedule of Long-term Commitments (Parenthetical) (Detail) $ in Millions	Dec. 31, 2020 USD ($)
Other Commitments [Line Items]
Total future minimum payments	$ 3,930
Gas Transportation [Member] \| PGS and SeaCoast [Member]
Other Commitments [Line Items]
Total future minimum payments	$ 117

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.

No definition available.

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Period Type:	duration