Employee Retirement Plans and Post-Retirement Benefit Plan - Additional Information (Detail)	12 Months Ended
	Dec. 30, 2017 USD ($) h CompensationPlan	Dec. 31, 2016 USD ($)	Dec. 26, 2015 USD ($)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Unfunded projected pension benefits	$ 2,200,000	$ 1,900,000
Long-term rate of return assumption	6.50%
Pension Benefit Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefit obligation, discount rate	3.68%	4.25%
Debt Securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Securities target allocation	35.00%
Debt Securities | Minimum
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Assumed average annual returns on assets	3.00%
Debt Securities | Maximum
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Assumed average annual returns on assets	6.00%
Equity Securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Securities target allocation	65.00%
Equity Securities | Minimum
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Assumed average annual returns on assets	8.00%
Equity Securities | Maximum
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Assumed average annual returns on assets	12.00%
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	6.00%
Pension contributions	$ 3,200,000	$ 3,500,000	$ 3,000,000
Non-Union Plans | Boston Beer 401 (k) Plan | Company's match for the first $1,000 of the eligible participants contribute
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Employer match percentage	100.00%
Contribution amount by the company	$ 1,000
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 match percentage	50.00%
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.
Pension contributions	$ 238,000	$ 219,000	$ 188,000
Eligibility period	12 months
Time required for eligibility | h	750
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	3.68%	4.25%
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%