Employee Retirement Plans and Post-Retirement Medical Benefits - Additional Information (Detail)	1 Months Ended	12 Months Ended
	Jan. 31, 2020	Dec. 26, 2020 USD ($) CompensationPlan	Dec. 28, 2019 USD ($)	Dec. 29, 2018 USD ($)
Pension Benefit Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Unfunded projected pension benefits		$ 0	$ 2,734,000
Retiree Medical Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Unfunded projected pension benefits		$ 1,077,000	888,000
Non-Union Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Number of retirement plans | CompensationPlan		1
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		$ 6,400,000	4,000,000.0	$ 3,500,000
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	5.00%
Employer match percentage	50.00%
Non-Union Plans | Dogfish Head 401 (K) Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Voluntary contributions of annual compensation		60.00%
Employer matching contribution percentage		5.00%
Contributions Plan			300,000
Non-Union Plans | Dogfish Head 401 (K) Plan | Company's match thereafter
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Employer match percentage		50.00%
Non-Union Plans | Dogfish Head 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 match percentage		100.00%
Contribution percentage by the company		3.00%
Union Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Number of retirement plans | CompensationPlan		2
Union Plans | Company Sponsored Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Eligibility timing		open to all union employees who are covered by the Company’s collective bargaining agreement with Teamsters Local Union. No. 1199 (“Local Union 1199”), or persons on leave from the Company who are employed by Local Union 1199, and in either case who have completed 12 consecutive months of employment with at least 750 hours worked.
Eligibility period		12 months
Time required for eligibility		750 hours
Expenses on termination of defined benefit plan		$ 2,000,000.0
Pension contributions		$ 2,900,000	$ 300,000	$ 300,000
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		2.50%	3.32%
Benefit obligation, rate of compensation increase		2.50%	2.50%	2.50%
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 union employees upon commencement of employment or, if later, attaining age 21.
Voluntary contributions of annual compensation		60.00%