Commitments and Contingencies (Narrative) (Details)	Dec. 31, 2020 USD ($) lease	Mar. 31, 2019 USD ($)
Commitments And Contingencies [Line Items]
Obligation under transportation agreements	$ 8,544,000,000
Guarantee obligations relative to the firms transportation agreements and gathering project and services	923,000,000
Maturities of operating leases (ASC 842):
2021	50,000,000
2022	37,000,000
2023	26,000,000
2024	18,000,000
2025	14,000,000
Thereafter	42,000,000
Indemnification liability	0
Pending regulatory approval and/or construction
Commitments And Contingencies [Line Items]
Obligation under transportation agreements	531,000,000
Appalachian Basin
Commitments And Contingencies [Line Items]
Obligation under transportation agreements		$ 357,000,000
Maturities of operating leases (ASC 842):
Obligation under transportation agreements, reimbursed by seller		$ 133,000,000
Pressure Pumping Equipment \| Exploration and Production
Commitments And Contingencies [Line Items]
Aggregate annual lease payment	6,000,000
Drilling Rigs \| Exploration and Production
Commitments And Contingencies [Line Items]
Aggregate annual lease payment	$ 11,000,000
Number of leases \| lease	7
Office Space, Vehicles And Equipment
Maturities of operating leases (ASC 842):
2021	$ 30,000,000
2022	21,000,000
2023	18,000,000
2024	14,000,000
2025	12,000,000
Thereafter	36,000,000
Compression Rentals
Maturities of operating leases (ASC 842):
2021	20,000,000
2022	14,000,000
2023	3,000,000
2024	$ 1,000,000

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Commitments And Contingencies [Line Items]

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Liability Associated With Indemnification Obligation

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Other Commitment, Reimbursed By Seller

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The current carrying amount of the liability for the freestanding or embedded guarantor's obligations under the guarantee or each group of similar guarantees.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (c)
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Amount of lessee's undiscounted obligation for lease payment for operating lease due after fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=121609121&loc=SL77918701-209980

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Amount of lessee's undiscounted obligation for lease payment for operating lease to be paid in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of lessee's undiscounted obligation for lease payment for operating lease to be paid in third fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of lessee's undiscounted obligation for lease payment for operating lease to be paid in second fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Number of separate real estate development properties located on land subject to ground leases.

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Minimum amount of other commitment not otherwise specified in the taxonomy. Excludes commitments explicitly modeled in the taxonomy, including but not limited to, long-term and short-term purchase commitments, recorded and unrecorded purchase obligations, supply commitments, registration payment arrangements, leases, debt, product warranties, guarantees, environmental remediation obligations, and pensions.

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