| Cover Page | Oct. 06, 2020 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Oct. 6, 2020 |
| Entity File Number | 001-16583 |
| Entity Registrant Name | ACUITY BRANDS, INC. |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 58-2632672 |
| Entity Address, Address Line One | 1170 Peachtree Street, N.E. |
| Entity Address, Address Line Two | Suite 2300 |
| Entity Address, City or Town | Atlanta |
| Entity Address, State or Province | GA |
| Entity Address, Postal Zip Code | 30309 |
| City Area Code | 404 |
| Local Phone Number | 853-1400 |
| Title of 12(b) Security | Common stock, $0.01 par value per share |
| Trading Symbol | AYI |
| Security Exchange Name | NYSE |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001144215 |
| Amendment Flag | false |
