Long-term debt - Summary of Long Term Debt (Parenthetical) (Detail) - USD ($)	12 Months Ended
Mar. 28, 2020	Mar. 30, 2019
Debt Instrument [Line Items]
Net of deferred financing costs	$ 400,000	$ 600,000
Term Loan from Investissement Quebec Prime Plus Seven Percent [Member]
Debt Instrument [Line Items]
Annual rate of prime plus	7.00%	7.00%
Balance of term loan	$ 5,000,000	$ 5,000,000
Line of Credit Facility Repayment Date	Jun. 05, 2019
Term Loan from Investissement Quebec Prime Plus Ten Percent [Member]
Debt Instrument [Line Items]
Annual rate of prime plus	10.00%	10.00%
Balance of term loan	$ 2,000,000	$ 2,000,000
Line of Credit Facility Repayment Date	Jun. 05, 2019
Finance Lease Obligations [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument Interest Rate Stated Percentage Rate	2.20%	2.20%
Finance Lease Obligations [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument Interest Rate Stated Percentage Rate	3.30%	3.30%
Cash Contribution one [Member] \| Montel [Member]
Debt Instrument [Line Items]
Interest on Cash advances	11.00%	11.00%
Cash received from related party	$ 1,500,000	$ 1,500,000
Cash Contribution Two [Member] \| Montel [Member]
Debt Instrument [Line Items]
Interest on Cash advances	11.00%	11.00%
Cash received from related party	$ 2,500,000	$ 2,500,000
Term Loan Facility Repayable At October Two Thousand Twenty Two [Member] \| Term Loan From Crystal Financial LLC CDOR Plus Eight Point Two Five Percent [Member]
Debt Instrument [Line Items]
Debt Instrument Interest Rate Stated Percentage Rate	8.25%	8.25%
Net of deferred financing costs	$ 272,000	$ 378,000

Interest Rate on Cash Advances

No definition available.

Name:	bgi_InterestRateOnCashAdvances
Namespace Prefix:	bgi_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Line Of Credit Facility Repayment Date

+ References

No definition available.

+ Details

Name:	bgi_LineOfCreditFacilityRepaymentDate
Namespace Prefix:	bgi_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

The percentage points added to the reference rate to compute the variable rate on the lessor's capital lease (sales-type and direct financing leases).

+ References

No definition available.

+ Details

Name:	us-gaap_CapitalLeasesOfLessorContingentRentalsBasisSpreadOnVariableRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ 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 210.5-02.17)
-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 835
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28555-108399

+ Details

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

- Definition

The cash inflow from a long-term borrowing made from related parties where one party can exercise control or significant influence over another party; including affiliates, owners or officers and their immediate families, pension trusts, and so forth. Alternate caption: Proceeds from Advances from Affiliates.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3255-108585

+ Details

Name:	us-gaap_ProceedsFromRelatedPartyDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Carrying value as of the balance sheet date, including the current and noncurrent portions, of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer). Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

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(22))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

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

- Details

Name:	us-gaap_LongtermDebtTypeAxis=bgi_TermLoanFromInvestissementOfQuebecPrimePlusSevenPercentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=bgi_TermLoanFromInvestissementOfQuebecPrimePlusTenPercentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=bgi_FinanceLeaseObligationsMember
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:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=bgi_CashContributionOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_CreditFacilityAxis=bgi_CashContributionTwoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=bgi_TermLoanFacilityRepayableAtOctoberTwoThousandTwentyTwoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=bgi_TermLoanFromCrystalFinancialLlcCdorPlusEightPointTwoFivePercentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: