Debt Instrument, Covenant, Consolidated Total Debt to Consolidated EBITDA Ratio, Maximum

No definition available.

Name:	blbd_DebtInstrumentCovenantConsolidatedTotalDebtToConsolidatedEBITDARatioMaximum
Namespace Prefix:	blbd_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Debt Instrument, Covenant, Liquidity for Minimum Units Manufactured Trigger, Minimum

+ References

No definition available.

+ Details

Name:	blbd_DebtInstrumentCovenantLiquidityForMinimumUnitsManufacturedTriggerMinimum
Namespace Prefix:	blbd_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Debt Instrument, Covenant, Maximum Borrowing Capacity After Equity Issuance

+ References

No definition available.

+ Details

Name:	blbd_DebtInstrumentCovenantMaximumBorrowingCapacityAfterEquityIssuance
Namespace Prefix:	blbd_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Debt Instrument, Covenant, Maximum Equity Offering

+ References

No definition available.

+ Details

Name:	blbd_DebtInstrumentCovenantMaximumEquityOffering
Namespace Prefix:	blbd_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Debt Instrument, Covenant, Maximum Long-Term Debt Before Equity Issuance

+ References

No definition available.

+ Details

Name:	blbd_DebtInstrumentCovenantMaximumLongTermDebtBeforeEquityIssuance
Namespace Prefix:	blbd_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Debt Instrument, Covenant, Repayment of Debt After Equity Issuance, Percentage

+ References

No definition available.

+ Details

Name:	blbd_DebtInstrumentCovenantRepaymentOfDebtAfterEquityIssuancePercentage
Namespace Prefix:	blbd_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Debt Instrument, Covenant, Units Manufactured, Carryforward, Percentage

+ References

No definition available.

+ Details

Name:	blbd_DebtInstrumentCovenantUnitsManufacturedCarryforwardPercentage
Namespace Prefix:	blbd_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

Reference 2: 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(a)(1))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	dtr-types: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://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1D
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495340-112611

Reference 3: 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=124435984&loc=d3e28555-108399

+ Details

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

- Definition

Amount of the cost of borrowed funds accounted for as interest expense for debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 6
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123466204&loc=SL6036836-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.8)
-URI http://asc.fasb.org/extlink&oid=123367319&loc=SL114868664-224227

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 55
-Paragraph 69F
-URI http://asc.fasb.org/extlink&oid=123466577&loc=SL123495745-112612

Reference 4: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 55
-Paragraph 69E
-URI http://asc.fasb.org/extlink&oid=123466577&loc=SL123495743-112612

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1F
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495355-112611

+ Details

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

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

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

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ 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(22))
-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 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 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

+ Details

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

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

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

- Definition

Weighted average interest rate of long-term debt outstanding calculated at point in time.

+ References

No definition available.

+ Details

Name:	us-gaap_LongtermDebtWeightedAverageInterestRate
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Cash received on stock transaction after deduction of issuance costs.

+ References

No definition available.

+ Details

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

- Details

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

- Details

Name:	us-gaap_DebtInstrumentAxis=blbd_FourthAmendmentToCreditAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_DebtInstrumentAxis=blbd_SeniorCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_DebtInstrumentAxis=blbd_ThirdAmendmenttotheCreditAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementLocationAxis=blbd_GainLossOExtinguishmentOfDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BalanceSheetLocationAxis=us-gaap_OtherNoncurrentAssetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BalanceSheetLocationAxis=blbd_SeniorNotesNoncurrentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=blbd_SecondAmendmentToCreditAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=blbd_SeniorRevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

Debt - Narrative (Details)		3 Months Ended
Debt - Narrative (Details)	Dec. 15, 2021 USD ($)	Jan. 01, 2022 USD ($)	Jan. 02, 2021 USD ($)	Nov. 24, 2021 USD ($)	Oct. 02, 2021 USD ($)
Debt Instrument [Line Items]
Net proceeds from sale of stock	$ 75,000,000
Interest expense		$ 3,100,000	$ 1,900,000
Line of Credit \| Fourth Amendment to Credit Agreement
Debt Instrument [Line Items]
Maximum TNLR ratio				3.50
Minimum liquidity to avoid trigger of manufacturing covenant				$ 50,000,000
Carryforward of minimum units manufactured				50.00%
Maximum equity offering				$ 100,000,000
Equity proceeds used to repay debt				100.00%
Maximum borrowings before equity issuance				$ 110,000,000
Maximum borrowing capacity after equity issuance				$ 100,000,000
Stated interest rate (as a percent)				0.50%
Senior Term Loan \| Senior Credit Facility
Debt Instrument [Line Items]
Long-term line of credit		$ 162,700,000			$ 166,500,000
Stated interest rate (as a percent)		6.00%			4.00%
Weighted average effective interest rate (as a percent)		7.20%			6.00%
Revolving Credit Facility \| Line of Credit \| Third Amendment to the Credit Agreement
Debt Instrument [Line Items]
Lender fees and other issuance costs				$ 2,500,000
Revolving Credit Facility \| Line of Credit \| Third Amendment to the Credit Agreement \| Gain (Loss) o Extinguishment of Debt [Member]
Debt Instrument [Line Items]
Lender fees and other issuance costs				500,000
Revolving Credit Facility \| Line of Credit \| Third Amendment to the Credit Agreement \| Other Noncurrent Assets
Debt Instrument [Line Items]
Lender fees and other issuance costs				1,100,000
Revolving Credit Facility \| Line of Credit \| Third Amendment to the Credit Agreement \| Senior Notes, Noncurrent
Debt Instrument [Line Items]
Lender fees and other issuance costs				800,000
Revolving Credit Facility \| Line of Credit \| Second Amendment to Credit Agreement \| Gain (Loss) o Extinguishment of Debt [Member]
Debt Instrument [Line Items]
Lender fees and other issuance costs				$ 100,000
Revolving Credit Facility \| Line of Credit \| Senior Revolving Credit Facility
Debt Instrument [Line Items]
Long-term line of credit		$ 5,000,000.0
Letters of Credit \| Line of Credit \| Senior Revolving Credit Facility
Debt Instrument [Line Items]
Remaining borrowing capacity		88,700,000
Letters of credit, amount outstanding		$ 6,300,000