Organization and Summary of Significant Accounting Policies (Narrative) (Details)			1 Months Ended	12 Months Ended
	Dec. 31, 2021 USD ($) $ / shares shares	Sep. 01, 2021 USD ($) $ / shares shares	Sep. 30, 2021 shares	Dec. 31, 2023 USD ($) segment shares	Dec. 31, 2022 USD ($) $ / shares shares	Dec. 31, 2021 USD ($) $ / shares shares	Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Number of segments | segment				2
Cash and cash equivalents				$ 21,000,000	$ 50,000,000
Outstanding checks included in accounts payable				$ 73,000,000	100,000,000
Natural gas, oil and NGL reserves discount				10.00%
Net book value adjusted for market differentials				$ 1,710,000,000
Impairments				1,710,000,000	0	$ 6,000,000
Net unevaluated costs excluded from amortization, cumulative				2,075,000,000	2,217,000,000
Capitalized interest				303,000,000
Other long-term assets				$ 96,000,000	$ 110,000,000
Treasury stock (in shares) | shares				0	17,261,469
Treasury stock acquired, average cost per share (in dollars per share) | $ / shares					$ 7.24
Treasury stock acquired					$ 125,000,000
Shares held in trust (in shares) | shares				1,455	1,743
Marketing-Related Intangible Assets
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Intangible assets, current				$ 38,000,000	$ 43,000,000
Other long-term assets				33,000,000	38,000,000
Amortization of intangible asset				5,000,000	5,000,000	8,000,000
Expected amortization in year one				5,000,000
Expected amortization in year two				5,000,000
Expected amortization in year three				5,000,000
Expected amortization in year four				5,000,000
Expected amortization in year five				4,000,000
Other non-core assets
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Impairments				$ 0	$ 0	6,000,000
Minimum | Non-full cost pool assets
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Long lived assets, useful life				3 years
Maximum | Non-full cost pool assets
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Long lived assets, useful life				30 years
Undeveloped Properties Southwest Appalachia
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Net unevaluated costs excluded from amortization, cumulative				$ 1,048,000,000
Undeveloped Properties Northeast Appalachia
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Net unevaluated costs excluded from amortization, cumulative				587,000,000
Wells In Progress
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Net unevaluated costs excluded from amortization, cumulative				59,000,000
Capitalized interest				$ 303,000,000
One Customer | Revenue Benchmark | Customer concentration risk
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Concentration percentage				14.00%	17.00%
WPX Property Acquisition
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Percentage of voting interest							86.00%
Other
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Impairments				$ 0	$ 0	0
Net unevaluated costs excluded from amortization, cumulative				$ 137,000,000
GEPH Merger
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Shares of Southwestern common stock issued in respect of outstanding common stock and stock-based awards (in shares) | shares	99,337,748
Business acquisition, equity interest issued or issuable, value assigned	$ 463,000,000					$ 463,000,000
NYSE closing price per share of Southwestern common shares (in dollars per share) | $ / shares	$ 4.66					$ 4.66
GEPH Merger | Common Stock
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Shares of Southwestern common stock issued in respect of outstanding common stock and stock-based awards (in shares) | shares						99,337,748
Business acquisition, equity interest issued or issuable, value assigned	$ 463,000,000					$ 463,000,000
NYSE closing price per share of Southwestern common shares (in dollars per share) | $ / shares	$ 4.66					$ 4.66
Indigo Merger
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Shares of Southwestern common stock issued in respect of outstanding common stock and stock-based awards (in shares) | shares		337,827,171
Business acquisition, equity interest issued or issuable, value assigned		$ 1,588,000,000
NYSE closing price per share of Southwestern common shares (in dollars per share) | $ / shares		$ 4.70
Indigo Merger | Common Stock
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Shares of Southwestern common stock issued in respect of outstanding common stock and stock-based awards (in shares) | shares			337,827,171
Business acquisition, equity interest issued or issuable, value assigned		$ 1,588,000,000
NYSE closing price per share of Southwestern common shares (in dollars per share) | $ / shares		$ 4.70