v3.5.0.2

Commitments and Contingencies - Additional Information (Details) $ in Millions	Oct. 31, 2016 USD ($)
Sales Tax Accrual [Member]
Loss Contingencies [Line Items]
Accrued contingency	$ 0.7
401K Accrual [Member]
Loss Contingencies [Line Items]
Accrued contingency	$ 0.5

X

- Definition

Amount of loss contingency liability expected to be resolved within one year or the normal operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14326-108349

+ Details

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

X

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

X

- Details

Name:	us-gaap_LossContingenciesByNatureOfContingencyAxis=bv_SalesTaxAccrualMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_LossContingenciesByNatureOfContingencyAxis=bv_A401KAccrualMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: