Document and Entity Information (USD $)	12 Months Ended
Sep. 30, 2011	Nov. 14, 2011	Mar. 31, 2011
Document Type	10-K
Document Period End Date	Sep. 30, 2011
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	2011
Document Fiscal Period Focus	FY
Entity Common Stock Shares Outstanding		90,364,061
Entity Public Float			$ 3,008,806,271

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The type of document being provided (such as 10-K, 10-Q, N-1A, etc). The document type should be limited to the same value as the supporting SEC submission type. The acceptable values are as follows: S-1, S-3, S-4, S-11, F-1, F-3, F-4, F-9, F-10, 6-K, 8-K, 10, 10-K, 10-Q, 20-F, 40-F, N-1A, 485BPOS, NCSR, N-Q, and Other.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

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