Commitments and Contingencies (Narrative) (Details)	Mar. 31, 2021 USD ($)
Commitments And Contingencies [Line Items]
Obligation under transportation agreements	$ 8,351,000,000
Guarantee obligations relative to the firms transportation agreements and gathering project and services	908,000,000
Material liabilities recognized	0
Pending regulatory approval and/or construction
Commitments And Contingencies [Line Items]
Obligation under transportation agreements	$ 436,000,000