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v3.25.3

Summary of Significant Accounting Policies - COGS (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2023
Selling, general and administrative expenses |  |  |
Cost of Goods Sold |  |  |
Storage and other warehousing costs | $ 37.3 | $ 25.3 | $ 20.1

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- Definition Storage and other warehousing costs + References No definition available. + Details
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Namespace Prefix: | brbr_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |