Document and Entity Information (USD $)	6 Months Ended
	Mar. 31, 2013	Apr. 26, 2013
Document And Entity Information [Abstract]
Document Type	10-Q
Document Period End Date	Mar. 31, 2013
Amendment Flag	false
Entity Registrant Name	Atmos Energy Corporation
Entity Central Index Key	0000731802
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Current Fiscal Year End Date	--09-30
Entity Filer Category	Large Accelerated Filer
Entity Well Known Seasoned Issuer	Yes
Document Fiscal Year Focus	2013
Document Fiscal Period Focus	Q2
Entity Common Stock Shares Outstanding		90,549,038
Entity Public Float	$ 3,816,801,052