2.4.0.8165 - Disclosure - Stock Options - Additional Information (Detail)truefalsefalse1false USDfalsefalse$eol_PE677256--1310-K0007_STD_365_20130430_0http://www.sec.gov/CIK0001330421duration2012-05-01T00:00:002013-04-30T00:00:00pureStandardhttp://www.xbrl.org/2003/instancepure0iso4217_USD_per_sharesDividehttp://www.xbrl.org/2003/iso4217USDiso4217http://www.xbrl.org/2003/instanceshares0iso4217_USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170sharesStandardhttp://www.xbrl.org/2003/instanceshares0USDUSD$2false USDfalsefalse$eol_PE677256--1310-K0007_STD_366_20120430_0http://www.sec.gov/CIK0001330421duration2011-05-01T00:00:002012-04-30T00:00:00iso4217_USD_per_sharesDividehttp://www.xbrl.org/2003/iso4217USDiso4217http://www.xbrl.org/2003/instanceshares0iso4217_USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170sharesStandardhttp://www.xbrl.org/2003/instanceshares0USDUSD$3false USDfalsefalse$eol_PE677256--1310-K0007_STD_365_20110430_0http://www.sec.gov/CIK0001330421duration2010-05-01T00:00:002011-04-30T00:00:00iso4217_USD_per_sharesDividehttp://www.xbrl.org/2003/iso4217USDiso4217http://www.xbrl.org/2003/instanceshares0iso4217_USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170sharesStandardhttp://www.xbrl.org/2003/instanceshares0USDUSD$1true 3us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItemsus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Share-based Compensation Arrangement by Share-based Payment Award [Line Items]2false 4us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumberus-gaap_truenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse1082900010829000falsefalsefalse2truefalsefalse1208300012083000falsefalsefalse3truefalsefalse1169100011691000falsefalsefalsexbrli:sharesItemTypesharesThe number of shares reserved for issuance under stock option agreements awarded under the plan that validly exist and are outstanding as of the balance sheet date, including vested options.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 123R -Paragraph A240 -Subparagraph b(1)(a) -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 123R -Paragraph A240 -Subparagraph b(1)(b) -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. false1Options to purchase shares of common stock outstanding3false 4us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRateus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truetruefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalsenum:percentItemTypepureThe estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2)(iii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 123R -Paragraph A240 -Subparagraph e(2)(c) -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. false0Expected dividend yield assumed4false 4us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValueus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse5.755.75USD$falsetruefalse2truefalsefalse5.145.14USD$falsetruefalse3truefalsefalse2.812.81USD$falsetruefalsenum:perShareItemTypedecimalThe weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 123R -Paragraph A240 -Subparagraph c(1) -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 false3Weighted-average grant date fair value of options granted5false 4us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValueus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse4280000042800000USD$falsetruefalse2truefalsefalse1080000010800000USD$falsetruefalse3truefalsefalse46000004600000USD$falsetruefalsexbrli:monetaryItemTypemonetaryThe total accumulated difference between fair values of underlying shares on dates of exercise and exercise price on options which were exercised (or share units converted) into shares during the reporting period under the plan.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d)(2) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 123R -Paragraph A240 -Subparagraph c(2) -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. false2Aggregate intrinsic value of options exercised6false 4us-gaap_AllocatedShareBasedCompensationExpenseus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalsepositiveLabel1truefalsefalse2250000022500000USD$falsefalsefalse2truefalsefalse77000007700000USD$falsefalsefalse3truefalsefalse47000004700000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryRepresents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 123R -Paragraph 64 -Subparagraph b -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 14.F) -URI http://asc.fasb.org/extlink&oid=6793087&loc=d3e301413-122809 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1)(i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 123R -Paragraph A240 -Subparagraph g(1) -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 14 -Section F false2Stock-based expense7false 4us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptionsus-gaap_truedebitinstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse2250000022500000USD$falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryAggregate unrecognized cost of option awards made to employees under a stock option plan or plans, that have yet to vest.No definition available.false2Total unrecognized stock-based expense related to unvested stock options8false 4us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1us-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse002 years 10 months 17 daysfalsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalsexbrli:durationItemTypenaWeighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 false0Future period share-based expense period of recognition9false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse4false USDtruefalse$eol_PE677256--1310-K0007_STD_365_20130430_0_512014x510320http://www.sec.gov/CIK0001330421duration2012-05-01T00:00:002013-04-30T00:00:00falsefalseGeneral and Administrative Expenseus-gaap_IncomeStatementLocationAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_GeneralAndAdministrativeExpenseMemberus-gaap_IncomeStatementLocationAxisexplicitMemberiso4217_USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$nanafalse0General and Administrative Expense10true 3us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItemsus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Share-based Compensation Arrangement by Share-based Payment Award [Line Items]11false 4us-gaap_AllocatedShareBasedCompensationExpenseus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalsepositiveLabel1truefalsefalse1337300013373000USD$falsefalsefalse2truefalsefalse32950003295000USD$falsefalsefalse3truefalsefalse18500001850000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryRepresents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 123R -Paragraph 64 -Subparagraph b -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 14.F) -URI http://asc.fasb.org/extlink&oid=6793087&loc=d3e301413-122809 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1)(i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 123R -Paragraph A240 -Subparagraph g(1) -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 14 -Section F false2Stock-based expense12false 4bv_EstimatedLiabilitybv_falsecreditinstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse22000002200000USD$falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryEstimated LiabilityNo definition available.false2Estimated liability for taxes, interest and related items13false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse7false USDtruefalseeol_PE677256--1310-K0007_STD_365_20130430_0_508454x512177http://www.sec.gov/CIK0001330421duration2012-05-01T00:00:002013-04-30T00:00:00falsefalseRestricted Stockus-gaap_AwardTypeAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_RestrictedStockMemberus-gaap_AwardTypeAxisexplicitMemberiso4217_USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170$nanafalse0Restricted Stock14true 3us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItemsus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Share-based Compensation Arrangement by Share-based Payment Award [Line Items]15false 4us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1us-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse003 years 2 months 23 daysfalsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalsexbrli:durationItemTypenaWeighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 false0Future period share-based expense period of recognition16false 4us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedus-gaap_truedebitinstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse90000009000000USD$falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryAs of the balance sheet date, the aggregate unrecognized cost of equity-based awards made to employees under equity-based compensation awards that have yet to vest.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 123R -Paragraph A240 -Subparagraph h -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. false2Future period share-based expense17false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse8false USDtruefalse$eol_PE677256--1310-K0007_STD_365_20130430_0_508454x514283http://www.sec.gov/CIK0001330421duration2012-05-01T00:00:002013-04-30T00:00:00falsefalseStock Optionsus-gaap_AwardTypeAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_StockOptionsMemberus-gaap_AwardTypeAxisexplicitMemberpureStandardhttp://www.xbrl.org/2003/instancepure0iso4217_USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$nanafalse0Stock Options18true 3us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItemsus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Share-based Compensation Arrangement by Share-based Payment Award [Line Items]19false 4us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRateus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truetruefalse0.000.00falsefalsefalse2truetruefalse0.000.00falsefalsefalse3truetruefalse0.000.00falsefalsefalsenum:percentItemTypepureThe estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (f)(2)(iii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 123R -Paragraph A240 -Subparagraph e(2)(c) -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. false0Expected dividend yield assumed20false 4us-gaap_AllocatedShareBasedCompensationExpenseus-gaap_truedebitdurationfalsefalsefalsefalsefalsefalsefalsefalsepositiveLabel1truefalsefalse98000009800000USD$falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryRepresents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 123R -Paragraph 64 -Subparagraph b -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 14.F) -URI http://asc.fasb.org/extlink&oid=6793087&loc=d3e301413-122809 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (h)(1)(i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 123R -Paragraph A240 -Subparagraph g(1) -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 14 -Section F false2Stock-based expense21false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse11false truefalseeol_PE677256--1310-K0007_STD_365_20130430_0_498429x531054http://www.sec.gov/CIK0001330421duration2012-05-01T00:00:002013-04-30T00:00:00falsefalseEmployee Stock Purchase Planus-gaap_PlanNameAxisxbrldihttp://xbrl.org/2006/xbrldibv_EmployeeStockPurchasePlanMemberus-gaap_PlanNameAxisexplicitMemberpureStandardhttp://www.xbrl.org/2003/instancepure0sharesStandardhttp://www.xbrl.org/2003/instanceshares0nanafalse0Employee Stock Purchase Plan22true 3us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItemsus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Share-based Compensation Arrangement by Share-based Payment Award [Line Items]23false 4us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantus-gaap_truenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse11371231137123falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalsexbrli:sharesItemTypesharesThe difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 false1Common stock share reserved to permit exercise of options outstanding24false 4bv_ExercisePriceOfStockOptionsGrantedPercentagebv_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truetruefalse0.850.85falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalsenum:percentItemTypepureExercise Price Of Stock Options Granted PercentageNo definition available.false0Stock option granted price, percentage25false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse12false USDtruefalse$eol_PE677256--1310-K0007_STD_0_20130430_0_497966x530824_498429x531054http://www.sec.gov/CIK0001330421instant2013-04-30T00:00:000001-01-01T00:00:00falsefalseEmployee Stock Purchase Planus-gaap_PlanNameAxisxbrldihttp://xbrl.org/2006/xbrldibv_EmployeeStockPurchasePlanMemberus-gaap_PlanNameAxisexplicitMemberfalsefalseAccrued Expenses and Other Current Liabilitiesus-gaap_BalanceSheetLocationAxisxbrldihttp://xbrl.org/2006/xbrldibv_AccruedExpensesAndOtherCurrentLiabilitiesMemberus-gaap_BalanceSheetLocationAxisexplicitMemberiso4217_USDStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$nanafalse0Employee Stock Purchase Plan | Accrued Expenses and Other Current Liabilities26true 3us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItemsus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Share-based Compensation Arrangement by Share-based Payment Award [Line Items]27false 4us-gaap_DueToEmployeesCurrentus-gaap_truecreditinstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse300000300000USD$falsetruefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalsexbrli:monetaryItemTypemonetaryAmounts due to employees, not to include stockholders or officers. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(k)(1)) -URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 850 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 08 -Paragraph k -Subparagraph 1 -Article 4 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 57 -Paragraph 2 -Subparagraph d -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(a)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 19 -Subparagraph a -Article 5 false2Amount held on behalf of employees for future stock purchases28false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse13false truefalseeol_PE677256--1310-K0007_STD_0_20130430_0_498429x676180http://www.sec.gov/CIK0001330421instant2013-04-30T00:00:000001-01-01T00:00:00falsefalse2005 Stock Option Planus-gaap_PlanNameAxisxbrldihttp://xbrl.org/2006/xbrldibv_TwoThousandFiveStockOptionPlanMemberus-gaap_PlanNameAxisexplicitMembersharesStandardhttp://www.xbrl.org/2003/instanceshares0nanafalse02005 Stock Option Plan29true 3us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItemsus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Share-based Compensation Arrangement by Share-based Payment Award [Line Items]30false 4us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumberus-gaap_truenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse68435066843506falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalsexbrli:sharesItemTypesharesThe number of shares reserved for issuance under stock option agreements awarded under the plan that validly exist and are outstanding as of the balance sheet date, including vested options.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 123R -Paragraph A240 -Subparagraph b(1)(a) -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 123R -Paragraph A240 -Subparagraph b(1)(b) -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. false1Options to purchase shares of common stock outstanding31false 4us-gaap_CommonStockCapitalSharesReservedForFutureIssuanceus-gaap_truenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse68435066843506falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalsexbrli:sharesItemTypesharesAggregate number of common shares reserved for future issuance.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 129 -Paragraph 4 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.29) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 false1Common shares reserved for Employee Stock Purchase Plan32false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse14false truefalseeol_PE677256--1310-K0007_STD_365_20130430_0_498429x618118http://www.sec.gov/CIK0001330421duration2012-05-01T00:00:002013-04-30T00:00:00falsefalse2012 Equity Incentive Planus-gaap_PlanNameAxisxbrldihttp://xbrl.org/2006/xbrldibv_TwoThousandTwelveEquityIncentivePlanMemberus-gaap_PlanNameAxisexplicitMemberpureStandardhttp://www.xbrl.org/2003/instancepure0sharesStandardhttp://www.xbrl.org/2003/instanceshares0nanafalse02012 Equity Incentive Plan33true 3us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItemsus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Share-based Compensation Arrangement by Share-based Payment Award [Line Items]34false 4us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorizedus-gaap_truenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse32470383247038falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalsexbrli:sharesItemTypesharesThe maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 123R -Paragraph A240 -Subparagraph a -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 false1Shares of common stock authorized for issuance35false 4us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantus-gaap_truenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse32470383247038falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalsexbrli:sharesItemTypesharesThe difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 false1Common stock share reserved to permit exercise of options outstanding36false 4bv_PercentageOfStockOptionsVestingInPeriodOfOneYearbv_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truetruefalse0.250.25falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalsenum:percentItemTypepurePercentage Of Stock Options Vesting In Period Of One YearNo definition available.false0Option granted , vesting percentage37false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse15false truefalseeol_PE677256--1310-K0007_STD_365_20130430_0_498429x618118_504957x513639http://www.sec.gov/CIK0001330421duration2012-05-01T00:00:002013-04-30T00:00:00falsefalse2012 Equity Incentive Planus-gaap_PlanNameAxisxbrldihttp://xbrl.org/2006/xbrldibv_TwoThousandTwelveEquityIncentivePlanMemberus-gaap_PlanNameAxisexplicitMemberfalsefalseMinimumus-gaap_RangeAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_MinimumMemberus-gaap_RangeAxisexplicitMemberpureStandardhttp://www.xbrl.org/2003/instancepure0nanafalse02012 Equity Incentive Plan | Minimum38true 3us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItemsus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Share-based Compensation Arrangement by Share-based Payment Award [Line Items]39false 4us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercentus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truetruefalse1.001.00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalsenum:percentItemTypepurePurchase price of common stock expressed as a percentage of its fair market value.No definition available.false0Exercise price as a percentage of the fair market value of common stock40false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse16false truefalseeol_PE677256--1310-K0007_STD_365_20130430_0_498429x618118_504957x514053http://www.sec.gov/CIK0001330421duration2012-05-01T00:00:002013-04-30T00:00:00falsefalse2012 Equity Incentive Planus-gaap_PlanNameAxisxbrldihttp://xbrl.org/2006/xbrldibv_TwoThousandTwelveEquityIncentivePlanMemberus-gaap_PlanNameAxisexplicitMemberfalsefalseMaximumus-gaap_RangeAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_MaximumMemberus-gaap_RangeAxisexplicitMembernanafalse02012 Equity Incentive Plan | Maximum41true 3us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItemsus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Share-based Compensation Arrangement by Share-based Payment Award [Line Items]42false 4bv_ShareBasedCompensationArrangementByShareBasedPaymentAwardExpirationTermbv_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse0010 yearsfalsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalsexbrli:durationItemTypenaShare Based Compensation Arrangement by Share Based Payment Award, Expiration TermNo definition available.false0Options, maximum term43false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse17false truefalseeol_PE677256--1310-K0007_STD_365_20130430_0_498429x618118_504957x513639_508454x569800http://www.sec.gov/CIK0001330421duration2012-05-01T00:00:002013-04-30T00:00:00falsefalse2012 Equity Incentive Planus-gaap_PlanNameAxisxbrldihttp://xbrl.org/2006/xbrldibv_TwoThousandTwelveEquityIncentivePlanMemberus-gaap_PlanNameAxisexplicitMemberfalsefalseShare Based Awards To More Than Ten Percent Ownersus-gaap_AwardTypeAxisxbrldihttp://xbrl.org/2006/xbrldibv_ShareBasedAwardsToMoreThanTenPercentOwnersMemberus-gaap_AwardTypeAxisexplicitMemberfalsefalseMinimumus-gaap_RangeAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_MinimumMemberus-gaap_RangeAxisexplicitMemberpureStandardhttp://www.xbrl.org/2003/instancepure0nanafalse02012 Equity Incentive Plan | Share Based Awards To More Than Ten Percent Owners | Minimum44true 3us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItemsus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Share-based Compensation Arrangement by Share-based Payment Award [Line Items]45false 4us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercentus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truetruefalse1.101.10falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalsenum:percentItemTypepurePurchase price of common stock expressed as a percentage of its fair market value.No definition available.false0Exercise price as a percentage of the fair market value of common stock46false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse18false truefalseeol_PE677256--1310-K0007_STD_365_20130430_0_498429x618118_504957x514053_508454x569800http://www.sec.gov/CIK0001330421duration2012-05-01T00:00:002013-04-30T00:00:00falsefalse2012 Equity Incentive Planus-gaap_PlanNameAxisxbrldihttp://xbrl.org/2006/xbrldibv_TwoThousandTwelveEquityIncentivePlanMemberus-gaap_PlanNameAxisexplicitMemberfalsefalseShare Based Awards To More Than Ten Percent Ownersus-gaap_AwardTypeAxisxbrldihttp://xbrl.org/2006/xbrldibv_ShareBasedAwardsToMoreThanTenPercentOwnersMemberus-gaap_AwardTypeAxisexplicitMemberfalsefalseMaximumus-gaap_RangeAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_MaximumMemberus-gaap_RangeAxisexplicitMembernanafalse02012 Equity Incentive Plan | Share Based Awards To More Than Ten Percent Owners | Maximum47true 3us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItemsus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Share-based Compensation Arrangement by Share-based Payment Award [Line Items]48false 4bv_ShareBasedCompensationArrangementByShareBasedPaymentAwardExpirationTermbv_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse005 yearsfalsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalsexbrli:durationItemTypenaShare Based Compensation Arrangement by Share Based Payment Award, Expiration TermNo definition available.false0Options, maximum term49false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse19false truefalseeol_PE677256--1310-K0007_STD_365_20130430_0_498429x618118_508454x514283http://www.sec.gov/CIK0001330421duration2012-05-01T00:00:002013-04-30T00:00:00falsefalse2012 Equity Incentive Planus-gaap_PlanNameAxisxbrldihttp://xbrl.org/2006/xbrldibv_TwoThousandTwelveEquityIncentivePlanMemberus-gaap_PlanNameAxisexplicitMemberfalsefalseStock Optionsus-gaap_AwardTypeAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_StockOptionsMemberus-gaap_AwardTypeAxisexplicitMembernanafalse02012 Equity Incentive Plan | Stock Options50true 3us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItemsus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Share-based Compensation Arrangement by Share-based Payment Award [Line Items]51false 4us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1us-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse004 yearsfalsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalsexbrli:durationItemTypenaPeriod which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 false0Share based award, vesting period52false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse20false truefalseeol_PE677256--1310-K0007_STD_365_20130430_0_498429x618118_508454x510905http://www.sec.gov/CIK0001330421duration2012-05-01T00:00:002013-04-30T00:00:00falsefalse2012 Equity Incentive Planus-gaap_PlanNameAxisxbrldihttp://xbrl.org/2006/xbrldibv_TwoThousandTwelveEquityIncentivePlanMemberus-gaap_PlanNameAxisexplicitMemberfalsefalseRestricted Stock Units (RSUs)us-gaap_AwardTypeAxisxbrldihttp://xbrl.org/2006/xbrldius-gaap_RestrictedStockUnitsRSUMemberus-gaap_AwardTypeAxisexplicitMembernanafalse02012 Equity Incentive Plan | Restricted Stock Units (RSUs)53true 3us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItemsus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Share-based Compensation Arrangement by Share-based Payment Award [Line Items]54false 4us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1us-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse004 yearsfalsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalsexbrli:durationItemTypenaPeriod which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 false0Share based award, vesting period55false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalse21false truefalseeol_PE677256--1310-K0007_STD_0_20130430_0_498429x597114_499577x661599http://www.sec.gov/CIK0001330421instant2013-04-30T00:00:000001-01-01T00:00:00falsefalse2005 Equity Incentive Planus-gaap_PlanNameAxisxbrldihttp://xbrl.org/2006/xbrldibv_TwoThousandAndFiveEquityIncentivePlanMemberus-gaap_PlanNameAxisexplicitMemberfalsefalsePower Reviewsus-gaap_BusinessAcquisitionAxisxbrldihttp://xbrl.org/2006/xbrldibv_PowerReviewsMemberus-gaap_BusinessAcquisitionAxisexplicitMembersharesStandardhttp://www.xbrl.org/2003/instanceshares0nanafalse02005 Equity Incentive Plan | Power Reviews56true 3us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItemsus-gaap_truenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1falsefalsefalse00falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Share-based Compensation Arrangement by Share-based Payment Award [Line Items]57false 4us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumberus-gaap_truenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse738645738645falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalsexbrli:sharesItemTypesharesThe number of shares reserved for issuance under stock option agreements awarded under the plan that validly exist and are outstanding as of the balance sheet date, including vested options.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 123R -Paragraph A240 -Subparagraph b(1)(a) -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 123R -Paragraph A240 -Subparagraph b(1)(b) -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. false1Options to purchase shares of common stock outstanding58false 4us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantus-gaap_truenainstantfalsefalsefalsefalsefalsefalsefalsefalseterseLabel1truefalsefalse738645738645falsefalsefalse2falsefalsefalse00falsefalsefalse3falsefalsefalse00falsefalsefalsexbrli:sharesItemTypesharesThe difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 false1Common stock share reserved to permit exercise of options outstandingfalseStock Options - Additional Information (Detail) (USD $)NoRoundingNoRoundingNoRoundingUnKnowntruefalsefalseSheethttp://www.bazaarvoice.com/taxonomy/role/DisclosureStockOptionsAdditionalInformation358