v3.5.0.1

Acquired Intangible Assets, net - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2016	Apr. 30, 2015	Apr. 30, 2014
Finite-Lived Intangible Assets [Line Items]
Amortization Of Intangible Assets Including Portion In Cost Of Revenue	$ 1,900	$ 1,900
Impairment of Intangible Assets, Finite-lived	$ 0	$ 0	$ 2,500
Discontinued Operations [Member]
Finite-Lived Intangible Assets [Line Items]
Impairment of Intangible Assets, Finite-lived			2,500
Discontinued Operations [Member] | Customer relationships
Finite-Lived Intangible Assets [Line Items]
Impairment of Intangible Assets, Finite-lived			2,400
Discontinued Operations [Member] | Developed technology
Finite-Lived Intangible Assets [Line Items]
Impairment of Intangible Assets, Finite-lived			$ 100

X

- Definition

Amortization of intangible assets including amount related to developed technology which is included in cost of revenue on the statement of operations.

+ References

No definition available.

+ Details

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

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Data Type:	xbrli:stringItemType
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X

- Definition

The amount of impairment loss recognized in the period resulting from the write-down of the carrying amount of a finite-lived intangible asset to fair value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16373-109275

+ Details

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X

- Details

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- Details

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X

- Details

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Namespace Prefix:
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