| Document And Entity Information | Mar. 01, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K/A |
| Amendment Flag | true |
| Document Period End Date | Mar. 1, 2021 |
| Entity Registrant Name | BEACON ROOFING SUPPLY, INC. |
| Entity Central Index Key | 0001124941 |
| Entity Emerging Growth Company | false |
| Entity File Number | 000-50924 |
| Entity Incorporation, State or Country Code | DE |
| Entity Tax Identification Number | 36-4173371 |
| Entity Address, Address Line One | 505 Huntmar Park Drive |
| Entity Address, Address Line Two | Suite 300 |
| Entity Address, City or Town | Herndon |
| Entity Address, State or Province | VA |
| Entity Address, Postal Zip Code | 20170 |
| City Area Code | 571 |
| Local Phone Number | 323-3939 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Amendment Description | Beacon Roofing Supply, Inc. filed a Current Report on Form 8-K with the Securities and Exchange Commission on March 3, 2021 (the “Prior 8-K”) announcing that the Board of Directors had appointed Earl Newsome, Jr. to serve as a director. The purpose of this Current Report on Form 8-K/A is to announce that on August 11, 2021, the Board appointed Mr. Newsome to serve on the Board's Nominating and Governance Committee. The remainder of the information contained in the Prior 8-K is not hereby amended. |
| Security 12b Title | Common Stock, $0.01 par value |
| Trading Symbol | BECN |
| Security Exchange Name | NASDAQ |
