Commitments and Contingencies - Additional Information (Detail) $ in Thousands	12 Months Ended
Dec. 26, 2020 USD ($) vendor	Dec. 28, 2019 USD ($)
Commitments and Contingencies Disclosure [Line Items]
Company's current brewing and packaging percentage	33.00%	23.00%
Prepaid brewing service fees current	$ 30,230	$ 12,077
Prepaid expense, current	56,800
Commitments [Member]
Commitments and Contingencies Disclosure [Line Items]
Estimated volume commitments contractual shortfall fees	70,700
City Brewing
Commitments and Contingencies Disclosure [Line Items]
Payments for capital improvements	71,600
Prepaid Third-party Brewing Fees
Commitments and Contingencies Disclosure [Line Items]
Prepaid brewing service fees current	14,800
Prepaid brewing service fees	$ 71,600
Minimum
Commitments and Contingencies Disclosure [Line Items]
Company's current brewing and packaging percentage	65.00%
Barley, Wheat and Malt
Commitments and Contingencies Disclosure [Line Items]
Number of suppliers \| vendor	4
Purchase commitments outstanding	$ 22,500
Hops
Commitments and Contingencies Disclosure [Line Items]
Purchase commitments	$ 29,500

Commitments and Contingencies Disclosure [Line Items]

No definition available.

Name:	sam_CommitmentsAndContingenciesDisclosureLineItems
Namespace Prefix:	sam_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Estimated volume commitments contractual shortfall fees.

+ References

No definition available.

+ Details

Name:	sam_EstimatedVolumeCommitmentsContractualShortfallFees
Namespace Prefix:	sam_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Number of Suppliers

+ References

No definition available.

+ Details

Name:	sam_NumberOfSuppliers
Namespace Prefix:	sam_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage Of Production Volumes

+ References

No definition available.

+ Details

Name:	sam_PercentageOfProductionVolumes
Namespace Prefix:	sam_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The cash outflow for acquisition of or capital improvements to properties held for investment (operating, managed, leased) or for use.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3213-108585

+ Details

Name:	us-gaap_PaymentsForCapitalImprovements
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of asset related to consideration paid in advance for costs that provide economic benefits in future periods, and amount of other assets.

+ References

No definition available.

+ Details

Name:	us-gaap_PrepaidExpenseAndOtherAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of asset related to consideration paid in advance for costs that provide economic benefits in future periods, and amount of other assets that are expected to be realized or consumed within one year or the normal operating cycle, if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(7))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=121566466&loc=d3e6676-107765

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(8))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_PrepaidExpenseAndOtherAssetsCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of asset related to consideration paid in advance for costs that provide economic benefits within a future period of one year or the normal operating cycle, if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=121566466&loc=d3e6787-107765

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=121566466&loc=d3e6676-107765

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 340
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6387103&loc=d3e6435-108320

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 340
-SubTopic 10
-Section 05
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=68074540&loc=d3e5879-108316

+ Details

Name:	us-gaap_PrepaidExpenseCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Minimum amount of purchase arrangement in which the entity has agreed to expend funds to procure goods or services from a supplier.

+ References

No definition available.

+ Details

Name:	us-gaap_PurchaseObligation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of the recorded obligation to transfer funds in the future for fixed or minimum amounts or quantities of goods or services at fixed or minimum prices (for example, as in take-or-pay contracts or throughput contracts).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 440
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=121559207&loc=d3e25383-109308

+ Details

Name:	us-gaap_RecordedUnconditionalPurchaseObligation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_FairValueByLiabilityClassAxis=us-gaap_CommitmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=sam_CityBrewingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	sam_NatureOfPrepaidExpensesAxis=sam_PrepaidBrewingFeesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis=sam_BarleyWheatAndMaltMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PurchaseCommitmentExcludingLongtermCommitmentAxis=sam_HopsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: