| Cover | May 07, 2020 | Mar. 30, 2020 |
| Cover [Abstract] | ||
| Document Type | 8-K | |
| Entity Registrant Name | BellRing Brands, Inc. | |
| City Area Code | 314 | |
| Local Phone Number | 644-7600 | |
| Written Communications | false | |
| Soliciting Material | false | |
| Pre-commencement Tender Offer | false | |
| Pre-commencement Issuer Tender Offer | false | |
| Entity Emerging Growth Company | true | |
| Entity Ex Transition Period | true | |
| Document Period End Date | May 7, 2020 | |
| Entity Incorporation, State or Country Code | DE | |
| Entity File Number | 001-39093 | |
| Entity Tax Identification Number | 83-4096323 | |
| Entity Address, Address Line One | 2503 S. Hanley Road | |
| Entity Address, City or Town | St. Louis | |
| Entity Address, State or Province | MO | |
| Entity Address, Postal Zip Code | 63144 | |
| Title of 12(b) Security | Class A Common Stock, $0.01 par value per share | |
| Trading Symbol | BRBR | |
| Security Exchange Name | NYSE | |
| Entity Central Index Key | 0001772016 | |
| Amendment Flag | false |
