v3.3.1.900

Summary of Significant Accounting Policies - Additional Information (Detail) | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Jan. 31, 2016 Customer revenue_source | Jan. 31, 2015 Customer | Jan. 31, 2016 Customer revenue_source | Apr. 30, 2015 Customer
Accounting Policies [Abstract] |  |  |  |
Number of clients that accounted for more than 10% of account receivables | 0 |  | 0 | 0
Number of clients that accounted for more than 10% of revenue | 0 | 0 |  |
Software as a Service (“SaaS”) |  |  |  |
Revenue Recognition, Multiple-deliverable Arrangements [Line Items] |  |  |  |
Revenue sources | revenue_source | 2 |  | 2 |
Service agreement period |  |  | 1 year |

X
- Definition Number of Customers With Greater Than Ten Percent Accounts Receivable Balance + References No definition available. + Details
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Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of Customers With Greater Than Ten Percent Revenue + References No definition available. + Details
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Namespace Prefix: | bv_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Revenue Recognition, Number of Revenue Sources + References No definition available. + Details
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Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Revenue Recognition, Service Agreement, Period + References No definition available. + Details
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Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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- References No definition available. + Details
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- 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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- Details
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Namespace Prefix: |
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Balance Type: |
Period Type: |