Document and Entity Information	9 Months Ended
	May 31, 2011	Jun. 27, 2011
Document and Entity Information [Abstract]
Entity Registrant Name	ACUITY BRANDS INC
Entity Central Index Key	0001144215
Document Type	10-Q
Document Period End Date	May 31, 2011
Amendment Flag	false
Document Fiscal Year Focus	2011
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--08-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		43,338,989