Deferred compensation arrangement percentage of participants compensation deferred.

No definition available.

Name:	bv_DeferredCompensationArrangementPercentageOfParticipantsCompensationDeferred
Namespace Prefix:	bv_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Net Deferred Gain Losses Net Of Taxes Expected To Be Recognized In Interest Expense

+ References

No definition available.

+ Details

Name:	bv_NetDeferredGainLossesNetOfTaxesExpectedToBeRecognizedInInterestExpense
Namespace Prefix:	bv_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Terminated notional amount.

+ References

No definition available.

+ Details

Name:	bv_TerminatedNotionalAmount
Namespace Prefix:	bv_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480237/815-40-50-5

+ Details

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

- Definition

Nominal volume used to calculate payments on a derivative instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeNonmonetaryNotionalAmountVolume
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:volumeItemType
Balance Type:	na
Period Type:	duration

- Definition

Nominal or face amount used to calculate payment on derivative.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480434/815-10-50-1B

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1A
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480434/815-10-50-1A

+ Details

Name:	us-gaap_DerivativeNotionalAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateContractMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateSwapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=bv_InterestRateCollarAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=bv_FuelSwapContractsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

Fair Value Measurements and Derivative Instruments - Additional Information (Details) gal in Millions, $ in Millions	6 Months Ended
	Mar. 31, 2024 USD ($) gal	Sep. 30, 2023 USD ($)	Aug. 28, 2023 USD ($)	Jan. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Interest Rate Contracts
Derivative [Line Items]
Notional amount	$ 600.0	$ 600.0
Interest Rate Swaps
Derivative [Line Items]
Notional amount				$ 500.0	$ 500.0
Net deferred gain on interest rate swap net of taxes expected to be recognized over the next 12 months	$ 6.1
Interest Rate Collar Agreement
Derivative [Line Items]
Notional amount				$ 500.0
Terminated notional amount			$ 400.0
Fuel Swap Contracts
Derivative [Line Items]
Notional volume \| gal	4.0
Maximum
Derivative [Line Items]
Percentage of participants compensation deferred	70.00%