v3.5.0.1

Accrued Expenses and Other Current Liabilities - Additional Information (Details) - USD ($) $ in Millions	Apr. 30, 2016	Apr. 30, 2015
Other Long Term Liabilities [Member]
Accrued Expenses and Other Current Liabilities [Line Items]
Lease Incentive, Payable	$ 6.3	$ 0.3
Accrued Liabilities [Member]
Accrued Expenses and Other Current Liabilities [Line Items]
Lease Incentive, Payable	$ 0.7	$ 0.8

X

- Definition

[Line Items] for Accrued Expenses and Other Current Liabilities [Table]

+ References

No definition available.

+ Details

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Namespace Prefix:	bv_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

This item represents an incentive or inducement contractually stipulated between parties to a lease whereby the lessor has committed to provide the entity (lessee) with a cash payment as inducement to enter the lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.15(a))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.15(5))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

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

X

- Details

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Namespace Prefix:
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Balance Type:
Period Type:

X

- Details

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Namespace Prefix:
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Balance Type:
Period Type: