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	Nov. 13, 2020 USD ($) $ / shares shares	Sep. 30, 2021 shares	Aug. 31, 2020 USD ($) $ / shares shares	Dec. 31, 2022 USD ($) subsidiary segment $ / shares shares	Dec. 31, 2021 USD ($) subsidiary $ / shares shares	Dec. 31, 2020 USD ($)	Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Number of segments | segment						2
Cash and cash equivalents	$ 28,000,000					$ 50,000,000	$ 28,000,000
Outstanding checks included in accounts payable	21,000,000					$ 100,000,000	21,000,000
Natural gas, oil and NGL reserves discount						10.00%
Net book value adjusted for market differentials								$ 2,825,000,000
Impairments						$ 0	6,000,000	2,830,000,000
Net unevaluated costs excluded from amortization, cumulative	2,231,000,000					2,217,000,000	2,231,000,000
Capitalized interest						278,000,000
Other long-term assets	$ 84,000,000					$ 110,000,000	$ 84,000,000
Treasury stock (in shares) | shares						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	2,035					1,743	2,035
Marketing-Related Intangible Assets
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Intangible assets, current	$ 48,000,000					$ 43,000,000	$ 48,000,000
Other long-term assets	$ 43,000,000					38,000,000	43,000,000
Amortization of intangible asset						5,000,000	8,000,000	9,000,000
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						$ 5,000,000
Other non-core assets
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Impairments							$ 6,000,000	5,000,000
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						$ 1,100,000,000
Undeveloped Properties Northeast Appalachia
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Net unevaluated costs excluded from amortization, cumulative						778,000,000
Wells In Progress
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Net unevaluated costs excluded from amortization, cumulative						46,000,000
Capitalized interest						$ 278,000,000
One Customer | Revenue Benchmark | Customer concentration risk
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Number of subsidiaries of major customer with which business is conducted | subsidiary						1	1
Concentration percentage						17.00%	12.00%
WPX Property Acquisition
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Percentage of voting interest									86.00%
Montage Merger
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Impairments						$ 0	$ 0	0
Unamortized cost of properties acquired								1,087,000,000
Net unevaluated costs excluded from amortization, cumulative						$ 111,000,000
Shares of Southwestern common stock issued in respect of outstanding common stock and stock-based awards (in shares) | shares			69,740,848
Business acquisition, equity interest issued or issuable, value assigned			$ 213,000,000
Offering price (in dollars per share) | $ / shares			$ 3.05		$ 2.50
Montage Merger | Public Stock Offering
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Underwritten public offering of common stock (in shares) | shares					63,250,000
Net proceeds from public offering					$ 152,000,000
Montage 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			69,740,848
Business acquisition, equity interest issued or issuable, value assigned			$ 213,000,000
Offering price (in dollars per share) | $ / shares			$ 3.05
Number of Southwestern Energy common stock for each share of common stock converted (in shares) | shares			1.8656
Montage Merger | Pro Forma
Organization, Consolidation and Presentation of Financial Statements [Line Items]
Impairments								$ 539,000,000
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
Offering price (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
Offering price (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
Offering price (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
Offering price (in dollars per share) | $ / shares		$ 4.70