Acquisitions (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions			1 Months Ended	3 Months Ended
	Dec. 31, 2021	Sep. 01, 2021	Sep. 30, 2021	Mar. 31, 2022	Mar. 31, 2021	Nov. 30, 2021
Business Acquisition [Line Items]
Total operating revenues				$ 2,943	$ 1,072
Operating income				1,299	$ 301
Long-term debt	$ 5,407			4,900
Obligation under transportation agreements				$ 10,158
Contractual commitments payments, term (in years)				2 years
Maximum
Business Acquisition [Line Items]
Contractual commitments payments, term (in years)				2 years
5.375% Senior Notes due February 2029 | Senior Notes
Business Acquisition [Line Items]
Stated interest rate		5.375%		5.375%		5.375%
Long-term debt		$ 700				$ 700
Indigo Agreement
Business Acquisition [Line Items]
Obligation under transportation agreements				$ 34
Liability for the estimated future payments				17
Purchase or volume commitments with gathering fresh water and sand
Business Acquisition [Line Items]
Obligation under transportation agreements				35
Haynesville
Business Acquisition [Line Items]
Total operating revenues				753
Operating income				$ 482
GEPH Merger
Business Acquisition [Line Items]
Cash consideration	$ 1,269
Shares of Southwestern common stock issued (in shares)	99,337,748
Value of Southwestern's stock issued as consideration	$ 463
NYSE closing price per share of Southwestern common shares (in dollars per share)	$ 4.66
Revolving credit facility	$ 81
Evaluated oil and gas properties	1,783
Unevaluated oil and gas properties (1)	58
Other property, plant and equipment	$ 2
Indigo Natural Resources, LLC
Business Acquisition [Line Items]
Cash consideration		$ 373
Shares of Southwestern common stock issued (in shares)		337,827,171	337,827,171
Value of Southwestern's stock issued as consideration		$ 1,588
NYSE closing price per share of Southwestern common shares (in dollars per share)		$ 4.70
Revolving credit facility		$ 95
Evaluated oil and gas properties		2,724
Unevaluated oil and gas properties (1)		693
Other property, plant and equipment		4
Senior unsecured notes		726
Indigo Natural Resources, LLC | 5.375% Senior Notes due February 2029 | Senior Notes
Business Acquisition [Line Items]
Senior note assumed in merger agreement		$ 700
Stated interest rate		5.375%