Cover Page - shares	9 Months Ended
	Sep. 30, 2019	Oct. 22, 2019
Cover page.
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2019
Document Transition Report	false
Entity File Number	001-08246
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Entity Registrant Name	SOUTHWESTERN ENERGY CO
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	71-0205415
Entity Address, Address Line One	10000 Energy Drive
Entity Address, City or Town	Spring,
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	77389
City Area Code	832
Local Phone Number	796-1000
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Central Index Key	0000007332
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Title of 12(b) Security	Common Stock, Par Value $0.01
Trading Symbol	SWN
Entity Common Stock, Shares Outstanding		541,296,926
Amendment Flag	false
Security Exchange Name	NYSE