v3.5.0.1

Quarterly Financial Information - Additional Information (Details) $ in Millions | 3 Months Ended
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Apr. 30, 2016 USD ($)
Quarterly Financial Information [Abstract] |
Quantifying Misstatement in Current Year Financial Statements, Amount | $ (0.9)

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- Definition Quarterly Financial Information [Abstract] + References No definition available. + Details
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Namespace Prefix: | bv_
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Period Type: | duration

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- Definition Amount of each individual error being corrected in the correcting adjustment. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 250 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SAB Topic 1.N) -URI http://asc.fasb.org/extlink&oid=26874127&loc=d3e30840-122693 + Details
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Balance Type: | debit
Period Type: | duration