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Employee Retirement Plans and Post-Retirement Medical Benefits - Additional Information (Detail) $ in Millions |  | 1 Months Ended | 12 Months Ended
--- | --- | --- | ---
Apr. 01, 2023 | Jan. 31, 2020 | Dec. 27, 2025 USD ($) CompensationPlan | Dec. 28, 2024 USD ($) | Dec. 30, 2023 USD ($)
Non-Union Plans | Boston Beer 401 (k) Plan |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |  |
Eligibility timing |  |  | eligible to participate in the Plan immediately upon employment |  |
Voluntary contributions of annual compensation |  |  | 60.00% |  |
Employer matching contribution percentage |  |  | 5.00% |  |
Contributions Plan | $ |  |  | $ 9.8 | $ 9.7 | $ 8.8
Non-Union Plans | Boston Beer 401 (k) Plan | Company's match thereafter |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |  |
Employer matching contribution percentage |  | 3.00% |  |  |
Employer match percentage |  | 100.00% |  |  |
Non-Union Plans | Boston Beer 401 (k) Plan | Company's match for the first 3% of the eligible participants contribute |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |  |
Employer matching contribution percentage |  | 2.00% |  |  |
Employer match percentage |  | 50.00% |  |  |
Non-Union Plans | Boston Beer 401 (k) Plan | Company's match for the first 5% of the eligible contribution |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |  |
Employer matching contribution percentage | 5.00% |  |  |  |
Employer match percentage | 100.00% |  |  |  |
Union Plans |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |  |
Number of retirement plans | CompensationPlan |  |  | 3 |  |
Union Plans | Retiree Medical Plan |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |  |
Eligibility period |  |  | 20 years |  |
Time required for eligibility |  |  | 5 years |  |
Benefit obligation, discount rate |  |  | 5.50% | 5.69% |
Benefit obligation, rate of compensation increase |  |  | 3.00% | 3.00% |
Percentage paid for coverage |  |  | 100.00% |  |
Union Plans | Retiree Medical Plan | Minimum |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |  |
Voluntarily retirement age |  |  | 57 years |  |
Union Plans | Retiree Medical Plan | Local #20 member |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |  |
Time required for eligibility |  |  | 7 years |  |
Retiree Medical Plan, last years of employment |  |  | 10 years |  |
Voluntarily retirement age |  |  | 65 years |  |
Union Plans | Retiree Medical Plan | Local #20 member | Minimum |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |  |
Eligibility period |  |  | 20 years |  |
Union Plans | Samuel Adams Cincinnati Brewery 401 (k) Plan |  |  |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |  |  |
Eligibility timing |  |  | all members of Local 20 upon commencement of employment or, if later, attaining age 21. |  |
Voluntary contributions of annual compensation |  |  | 60.00% |  |

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