Earnings Per Share (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions			1 Months Ended		6 Months Ended
	Dec. 31, 2021	Sep. 01, 2021	Jun. 30, 2022	Sep. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Stock repurchase program, number of shares authorized to be repurchased			2,800,000		2,800,000
Stock repurchase program, shares repurchase, average price per share			$ 7.10
Purchase of treasury stock					$ (20)	$ 0
GEPH Merger
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
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
Indigo Natural Resources, LLC
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
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