2.4.0.8020024 - Document - Risk/Return Summary {Unlabeled} - Dreyfus Opportunistic Midcap Value Fundfalsefalsetrue1false falsefalseS000000461Memberhttp://www.sec.gov/CIK0000914775duration2012-08-31T00:00:002012-08-31T00:00:001false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00Dreyfus Opportunistic Midcap Value Fundfalsefalsefalse1false truefalseS000000461Memberhttp://www.sec.gov/CIK0000914775duration2012-08-31T00:00:002012-08-31T00:00:00falsefalseck0000914775_S000000461Memberdei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000914775_S000000461Memberdei_LegalEntityAxisexplicitMembernanafalse0Dreyfus Opportunistic Midcap Value Fund2false 4rr_RiskReturnHeadingrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00Fund Summaryfalsefalsefalsexbrli:stringItemTypestringRisk/Return Summary Investment Objectives/Goals Include the following information, in plain English under rule 421(d) under the Securities Act, in the order and subject matter indicatedReference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 2 false0Risk/Return [Heading]3false 4rr_ObjectiveHeadingrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00Investment Objectivefalsefalsefalsexbrli:stringItemTypestringInvestment Objectives/Goals. Disclose the Fund's investment objectives or goals. A Fund also may identify its type or category (e.g., that it is a Money Market Fund or a balanced fund).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 2 -Subsection a false0Objective [Heading]4false 4rr_ObjectivePrimaryTextBlockrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00 The fund seeks to surpass the performance of the Russell Midcap® Value Index. falsefalsefalsenonnum:textBlockItemTypenaInvestment Objectives/Goals. Disclose the Fund's investment objectives or goals. A Fund also may identify its type or category (e.g., that it is a Money Market Fund or a balanced fund).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 2 -Subsection a false0Objective, Primary [Text Block]5false 4rr_ExpenseHeadingrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00Fees and Expensesfalsefalsefalsexbrli:stringItemTypestringRisk/Return Summary Fee Table Includes the following information, in plain English under rule 421(d) under the Securities Act, after Item 2 Fees and expenses of the Fund This table describes the fees and expenses that you may pay if you buy and hold shared of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $[_____] in [name of fund family] funds. Shareholder Fees (fees paid directly from your investment) Example This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then you redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return per year and that the Fund's operating expenses remained the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be You would pay the following expenses if you did not redeem your shares The Example does not reflect sales charges (loads) on reinvested dividends [and other distributions]. If these sales charges (loads) were included, your costs would be higher. Portfolio Turnover The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover may indicate higher transaction costs. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was __% of the average value of its whole portfolio. Instructions. A.3.instructions.6 New Funds. For purposes of this Item, a "New Fund" is a Fund that does not include in Form N-1A financial statements reporting operating results or that includes financial statements for the Fund's initial fiscal year reporting operating results for a period of 6 months or less. The following Instructions apply to New Funds.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Subsection instructions -Paragraph 1 -Subparagraph d false0Expense [Heading]6false 4rr_ExpenseNarrativeTextBlockrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00 This table describes the fees and expenses that you may pay if you buy and hold shares of the fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in certain funds in the Dreyfus Family of Funds. More information about these and other discounts is available from your financial professional and in the Shareholder Guide section beginning on page 9 of this prospectus and in the How to Buy Shares section and the Additional Information About How to Buy Shares section beginning on page II-1 and page III-1, respectively, of the fund's Statement of Additional Information. falsefalsefalsenonnum:textBlockItemTypenaThis table describes the fees and expenses that you may pay if you buy and hold shared of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $[_____] in [name of fund family] funds. Include the narrative explanations in the order indicated. A Fund may modify the narrative explanations if the explanation contains comparable information to that shown. The narrative explanation regarding sales charge discounts is only required by a Fund that offers such discounts and should specify the minimum level of investment required to qualify for a discount. Modify the narrative explanation to state that Fund shares are sold on a national securities exchange at the end of the time periods indicated, and that brokerage commissions for buying and selling Fund shares through a broker are not reflected.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Subsection instructions -Paragraph 1 -Subparagraph b false0Expense Narrative [Text Block]7false 4rr_ShareholderFeesCaptionrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00Shareholder Fees (fees paid directly from your investment)falsefalsefalsexbrli:stringItemTypestringShareholder Fees (fees paid directly from your investment).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Subsection table -Paragraph 1 false0Shareholder Fees Caption [Text]8false 4rr_ShareholderFeesTableTextBlockrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00~ http://dreyfus.com/20130625/role/ScheduleShareholderFees20025 column dei_LegalEntityAxis compact ck0000914775_S000000461Member row primary compact * ~falsefalse~ http://dreyfus.com/20130625/role/ScheduleShareholderFees20025 column dei_LegalEntityAxis compact ck0000914775_S000000461Member row primary compact * ~falsehttp://dreyfus.com/20130625/role/ScheduleShareholderFees20025020025 - Schedule - Shareholder Feestruefalsefalse1falseColumnperiodPeriod*Columndei_LegalEntityAxisAxisck0000914775_S000000461MemberColumnrr_ProspectusShareClassAxisAxis*ColumnunitUnit*duration2012-08-31T00:00:002012-08-31T00:00:00falsefalseDreyfus Opportunistic Midcap Value Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000914775_S000000461Memberdei_LegalEntityAxisexplicitMemberfalsefalseClass Arr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000914775_C000001288Memberrr_ProspectusShareClassAxisexplicitMemberDreyfus Opportunistic Midcap Value FundClass ApureStandardhttp://www.xbrl.org/2003/instancepurexbrli0Standard0 USDfalsefalseduration2012-08-31T00:00:002012-08-31T00:00:00$2falseColumnperiodPeriod*Columndei_LegalEntityAxisAxisck0000914775_S000000461MemberColumnrr_ProspectusShareClassAxisAxis*ColumnunitUnit*duration2012-08-31T00:00:002012-08-31T00:00:00falsefalseDreyfus Opportunistic Midcap Value Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000914775_S000000461Memberdei_LegalEntityAxisexplicitMemberfalsefalseClass Crr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000914775_C000064720Memberrr_ProspectusShareClassAxisexplicitMemberDreyfus Opportunistic Midcap Value FundClass CpureStandardhttp://www.xbrl.org/2003/instancepurexbrli0Standard0 USDfalsefalseduration2012-08-31T00:00:002012-08-31T00:00:00$3falseColumnperiodPeriod*Columndei_LegalEntityAxisAxisck0000914775_S000000461MemberColumnrr_ProspectusShareClassAxisAxis*ColumnunitUnit*duration2012-08-31T00:00:002012-08-31T00:00:00falsefalseDreyfus Opportunistic Midcap Value Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000914775_S000000461Memberdei_LegalEntityAxisexplicitMemberfalsefalseClass Irr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000914775_C000064721Memberrr_ProspectusShareClassAxisexplicitMemberDreyfus Opportunistic Midcap Value FundClass IpureStandardhttp://www.xbrl.org/2003/instancepurexbrli0Standard0 USDfalsefalseduration2012-08-31T00:00:002012-08-31T00:00:00$4falseColumnperiodPeriod*Columndei_LegalEntityAxisAxisck0000914775_S000000461MemberColumnrr_ProspectusShareClassAxisAxis*ColumnunitUnit*duration2012-08-31T00:00:002012-08-31T00:00:00falsefalseDreyfus Opportunistic Midcap Value Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000914775_S000000461Memberdei_LegalEntityAxisexplicitMemberfalsefalseClass Yrr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000914775_C000130426Memberrr_ProspectusShareClassAxisexplicitMemberDreyfus Opportunistic Midcap Value FundClass YpureStandardhttp://www.xbrl.org/2003/instancepurexbrli0Standard0 USDfalsefalseduration2012-08-31T00:00:002012-08-31T00:00:00$1falseRowprimaryElement*3false 4rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPricerr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalselabelrr:NonNegativePure4TypepureMaximum Deferred Sales Charge (Load) (as a percentage of ____) A.3.instructions.2.a.i "Maximum Deferred Sales Charge (Load)" includes the maximum total deferred sales charge (load) payable upon redemption, in installments, or both, expressed as a percentage of the amount or amounts stated in response to Item 7(a), except that, for a sales charge (load) based on net asset value at the time of purchase, show the sales charge (load) as a percentage of the offering price at the time of purchase. A Fund may include in a footnote to the table, if applicable, a tabular presentation showing the amount of deferred sales charges (loads) over time or a narrative explanation of the sales charges (loads) (e.g., __% in the first year after purchase, declining to __% in the __ year and eliminated thereafter). A.3.instructions.2.a.ii If more than one type of sales charge (load) is imposed (e.g., a deferred sales charge (load) and a front-end sales charge (load)), the first caption in the table should read "Maximum Sales Charge (Load)" and show the maximum cumulative percentage. Show the percentage amounts and the terms of each sales charge (load) comprising that figure on separate lines below.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Subsection table -Paragraph 1 -Subparagraph 1 false0Maximum sales charge (load) imposed on purchases (as a percentage of offering price) 0rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPricerr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalselabel1truetruetrue0.05750.0575falsefalsefalse2truetruetrue0.00000.0000falsefalsefalse3truetruetrue0.00000.0000falsefalsefalse4truetruetrue0.00000.0000falsefalsefalserr:NonNegativePure4TypepureMaximum Deferred Sales Charge (Load) (as a percentage of ____) A.3.instructions.2.a.i "Maximum Deferred Sales Charge (Load)" includes the maximum total deferred sales charge (load) payable upon redemption, in installments, or both, expressed as a percentage of the amount or amounts stated in response to Item 7(a), except that, for a sales charge (load) based on net asset value at the time of purchase, show the sales charge (load) as a percentage of the offering price at the time of purchase. A Fund may include in a footnote to the table, if applicable, a tabular presentation showing the amount of deferred sales charges (loads) over time or a narrative explanation of the sales charges (loads) (e.g., __% in the first year after purchase, declining to __% in the __ year and eliminated thereafter). A.3.instructions.2.a.ii If more than one type of sales charge (load) is imposed (e.g., a deferred sales charge (load) and a front-end sales charge (load)), the first caption in the table should read "Maximum Sales Charge (Load)" and show the maximum cumulative percentage. Show the percentage amounts and the terms of each sales charge (load) comprising that figure on separate lines below.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Subsection table -Paragraph 1 -Subparagraph 1 false0Maximum sales charge (load) imposed on purchases (as a percentage of offering price)2falseRowprimaryElement*4false 4rr_MaximumDeferredSalesChargeOverOtherrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalselabelrr:NonNegativePure4TypepureMaximum Deferred Sales Charge (Load) (as a percentage of ____) "Maximum Deferred Sales Charge (Load)" includes the maximum total deferred sales charge (load) payable upon redemption, in installments, or both, expressed as a percentage of the amount or amounts stated in response to Item 7(a), except that, for a sales charge (load) based on net asset value at the time of purchase, show the sales charge (load) as a percentage of the offering price at the time of purchase. A Fund may include in a footnote to the table, if applicable, a tabular presentation showing the amount of deferred sales charges (loads) over time or a narrative explanation of the sales charges (loads) (e.g., __% in the first year after purchase, declining to __% in the __ year and eliminated thereafter). If more than one type of sales charge (load) is imposed (e.g., a deferred sales charge (load) and a front-end sales charge (load)), the first caption in the table should read "Maximum Sales Charge (Load)" and show the maximum cumulative percentage. Show the percentage amounts and the terms of each sales charge (load) comprising that figure on separate lines below.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Subsection instructions -Paragraph 2 -Subparagraph a -Clause i false0Maximum deferred sales charge (load) (as a percentage of lower of purchase or sale price) 0rr_MaximumDeferredSalesChargeOverOtherrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalselabel1truetruetrue0.00000.0000[1]falsefalsefalse2truetruetrue0.01000.0100falsefalsefalse3truetruetrue0.00000.0000falsefalsefalse4truetruetrue0.00000.0000falsefalsefalserr:NonNegativePure4TypepureMaximum Deferred Sales Charge (Load) (as a percentage of ____) "Maximum Deferred Sales Charge (Load)" includes the maximum total deferred sales charge (load) payable upon redemption, in installments, or both, expressed as a percentage of the amount or amounts stated in response to Item 7(a), except that, for a sales charge (load) based on net asset value at the time of purchase, show the sales charge (load) as a percentage of the offering price at the time of purchase. A Fund may include in a footnote to the table, if applicable, a tabular presentation showing the amount of deferred sales charges (loads) over time or a narrative explanation of the sales charges (loads) (e.g., __% in the first year after purchase, declining to __% in the __ year and eliminated thereafter). If more than one type of sales charge (load) is imposed (e.g., a deferred sales charge (load) and a front-end sales charge (load)), the first caption in the table should read "Maximum Sales Charge (Load)" and show the maximum cumulative percentage. Show the percentage amounts and the terms of each sales charge (load) comprising that figure on separate lines below.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Subsection instructions -Paragraph 2 -Subparagraph a -Clause i false0Maximum deferred sales charge (load) (as a percentage of lower of purchase or sale price)1Class A shares bought without an initial sales charge as part of an investment of $1 million or more may be charged a deferred sales charge of 1.00% if redeemed within one year.falseShareholder Fees Dreyfus Opportunistic Midcap Value FundUnKnownUnKnownUnKnownUnKnownfalsefalsefalseSheet426442018ColumnperiodPeriod*Columndei_LegalEntityAxisAxisck0000914775_S000000461MemberColumnrr_ProspectusShareClassAxisAxis*ColumnunitUnit*RowprimaryElement*falsenonnum:textBlockItemTypenaContains a command for the SEC Viewer for the role corresponding to ShareholderFeesData.No definition available.false0Shareholder Fees [Table]9false 4rr_OperatingExpensesCaptionrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)falsefalsefalsexbrli:stringItemTypestringAnnual Fund Operating Expenses (ongoing expenses that you pay each year as a percentage of the value of your investment)Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Subsection table -Paragraph 1 -Subparagraph 7 false0Operating Expenses Caption [Text]10false 4rr_AnnualFundOperatingExpensesTableTextBlockrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00~ http://dreyfus.com/20130625/role/ScheduleAnnualFundOperatingExpenses20026 column dei_LegalEntityAxis compact ck0000914775_S000000461Member row primary compact * ~falsefalse~ http://dreyfus.com/20130625/role/ScheduleAnnualFundOperatingExpenses20026 column dei_LegalEntityAxis compact ck0000914775_S000000461Member row primary compact * ~falsehttp://dreyfus.com/20130625/role/ScheduleAnnualFundOperatingExpenses20026020026 - Schedule - Annual Fund Operating Expensestruefalsefalse1falseColumnperiodPeriod*Columndei_LegalEntityAxisAxisck0000914775_S000000461MemberColumnrr_ProspectusShareClassAxisAxis*ColumnunitUnit*duration2012-08-31T00:00:002012-08-31T00:00:00falsefalseDreyfus Opportunistic Midcap Value Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000914775_S000000461Memberdei_LegalEntityAxisexplicitMemberfalsefalseClass Arr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000914775_C000001288Memberrr_ProspectusShareClassAxisexplicitMemberDreyfus Opportunistic Midcap Value FundClass ApureStandardhttp://www.xbrl.org/2003/instancepurexbrli0Standard0 USDfalsefalseduration2012-08-31T00:00:002012-08-31T00:00:00$2falseColumnperiodPeriod*Columndei_LegalEntityAxisAxisck0000914775_S000000461MemberColumnrr_ProspectusShareClassAxisAxis*ColumnunitUnit*duration2012-08-31T00:00:002012-08-31T00:00:00falsefalseDreyfus Opportunistic Midcap Value Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000914775_S000000461Memberdei_LegalEntityAxisexplicitMemberfalsefalseClass Crr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000914775_C000064720Memberrr_ProspectusShareClassAxisexplicitMemberDreyfus Opportunistic Midcap Value FundClass CpureStandardhttp://www.xbrl.org/2003/instancepurexbrli0Standard0 USDfalsefalseduration2012-08-31T00:00:002012-08-31T00:00:00$3falseColumnperiodPeriod*Columndei_LegalEntityAxisAxisck0000914775_S000000461MemberColumnrr_ProspectusShareClassAxisAxis*ColumnunitUnit*duration2012-08-31T00:00:002012-08-31T00:00:00falsefalseDreyfus Opportunistic Midcap Value Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000914775_S000000461Memberdei_LegalEntityAxisexplicitMemberfalsefalseClass Irr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000914775_C000064721Memberrr_ProspectusShareClassAxisexplicitMemberDreyfus Opportunistic Midcap Value FundClass IpureStandardhttp://www.xbrl.org/2003/instancepurexbrli0Standard0 USDfalsefalseduration2012-08-31T00:00:002012-08-31T00:00:00$4falseColumnperiodPeriod*Columndei_LegalEntityAxisAxisck0000914775_S000000461MemberColumnrr_ProspectusShareClassAxisAxis*ColumnunitUnit*duration2012-08-31T00:00:002012-08-31T00:00:00falsefalseDreyfus Opportunistic Midcap Value Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000914775_S000000461Memberdei_LegalEntityAxisexplicitMemberfalsefalseClass Yrr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000914775_C000130426Memberrr_ProspectusShareClassAxisexplicitMemberDreyfus Opportunistic Midcap Value FundClass YpureStandardhttp://www.xbrl.org/2003/instancepurexbrli0Standard0 USDfalsefalseduration2012-08-31T00:00:002012-08-31T00:00:00$1falseRowprimaryElement*3false 4rr_ManagementFeesOverAssetsrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalselabelrr:NonNegativePure4TypepureManagement Fees include investment advisory fees (including any fees based on the Fund's performance), any other management fees payable to the investment adviser or its affiliates, and administrative fees payable to the investment adviser or its affiliates that are not included as "Other Expenses."Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Subsection instructions -Paragraph 3 -Subparagraph a false0Management fees 0rr_ManagementFeesOverAssetsrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalselabel1truetruetrue0.00750.0075falsefalsefalse2truetruetrue0.00750.0075falsefalsefalse3truetruetrue0.00750.0075falsefalsefalse4truetruetrue0.00750.0075falsefalsefalserr:NonNegativePure4TypepureManagement Fees include investment advisory fees (including any fees based on the Fund's performance), any other management fees payable to the investment adviser or its affiliates, and administrative fees payable to the investment adviser or its affiliates that are not included as "Other Expenses."Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Subsection instructions -Paragraph 3 -Subparagraph a false0Management fees2falseRowprimaryElement*4false 4rr_DistributionAndService12b1FeesOverAssetsrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalselabelrr:NonNegativePure4TypepureDistribution [and/or Service] (12b-1) Fees" include all distribution or other expenses incurred during the most recent fiscal year under a plan adopted pursuant to rule 12b-1 [17 CFR 270.12b-1]. Under an appropriate caption or a subcaption of "Other Expenses," disclose the amount of any distribution or similar expenses deducted from the Fund's assets other than pursuant to a rule 12b-1 plan.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Subsection table -Paragraph 1 -Subparagraph 9 false0Distribution (12b-1) fees 0rr_DistributionAndService12b1FeesOverAssetsrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalselabel1truetruetrue0.00000.0000falsefalsefalse2truetruetrue0.00750.0075falsefalsefalse3truetruetrue0.00000.0000falsefalsefalse4truetruetrue0.00000.0000falsefalsefalserr:NonNegativePure4TypepureDistribution [and/or Service] (12b-1) Fees" include all distribution or other expenses incurred during the most recent fiscal year under a plan adopted pursuant to rule 12b-1 [17 CFR 270.12b-1]. Under an appropriate caption or a subcaption of "Other Expenses," disclose the amount of any distribution or similar expenses deducted from the Fund's assets other than pursuant to a rule 12b-1 plan.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Subsection table -Paragraph 1 -Subparagraph 9 false0Distribution (12b-1) fees3falseRowprimaryElement*5false 4rr_OtherExpensesOverAssetsrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalselabelrr:NonNegativePure4Typepure"Other Expenses" include all expenses not otherwise disclosed in the table that are deducted from the Fund's assets or charged to all shareholder accounts. The amount of expenses deducted from the Fund's assets are the amounts shown as expenses in the Fund's statement of operations (including increases resulting from complying with paragraph 2(g) of rule 6-07 of Regulation S-X [17 CFR 210.6-07]). "Other Expenses" do not include extraordinary expenses as determined under generally accepted accounting principles (see Accounting Principles Board Opinion No. 30). If extraordinary expenses were incurred that materially affected the Fund's "Other Expenses," disclose in a footnote to the table what "Other Expenses" would have been had the extraordinary expenses been included.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Subsection instructions -Paragraph 3 -Subparagraph c -Clause i false0Other expenses (including shareholder services fees) 0rr_OtherExpensesOverAssetsrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalselabel[1]1truetruetrue0.00470.0047falsefalsefalse2truetruetrue0.00530.0053falsefalsefalse3truetruetrue0.00250.0025falsefalsefalse4truetruetrue0.00060.0006falsefalsefalserr:NonNegativePure4Typepure"Other Expenses" include all expenses not otherwise disclosed in the table that are deducted from the Fund's assets or charged to all shareholder accounts. The amount of expenses deducted from the Fund's assets are the amounts shown as expenses in the Fund's statement of operations (including increases resulting from complying with paragraph 2(g) of rule 6-07 of Regulation S-X [17 CFR 210.6-07]). "Other Expenses" do not include extraordinary expenses as determined under generally accepted accounting principles (see Accounting Principles Board Opinion No. 30). If extraordinary expenses were incurred that materially affected the Fund's "Other Expenses," disclose in a footnote to the table what "Other Expenses" would have been had the extraordinary expenses been included.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Subsection instructions -Paragraph 3 -Subparagraph c -Clause i false0Other expenses (including shareholder services fees)4falseRowprimaryElement*6false 4rr_ExpensesOverAssetsrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalselabelrr:NonNegativePure4TypepureTotal Annual Fund Operating Expenses. If the Fund is a Feeder Fund, reflect the aggregate expenses of the Feeder Fund and the Master Fund in a single fee table using the captions provided. In a footnote to the fee table, state that the table and Example reflect the expenses of both the Feeder and Master Funds. If the prospectus offers more than one Class of a Multiple Class Fund or more than one Feeder Fund that invests in the same Master Fund, provide a separate response for each Class or Feeder Fund. Base the percentages of "Annual Fund Operating Expenses" on amounts incurred during the Fund's most recent fiscal year, but include in expenses amounts that would have been incurred absent expense reimbursement or fee waiver arrangements. If the Fund has changed its fiscal year and, as a result, the most recent fiscal year is less than three months, use the fiscal year prior to the most recent fiscal year as the basis for determining "Annual Fund Operating Expenses."Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Subsection instructions -Paragraph 3 -Subparagraph d false0Total annual fund operating expenses 0rr_ExpensesOverAssetsrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalselabel1truetruetrue0.01220.0122falsefalsefalse2truetruetrue0.02030.0203falsefalsefalse3truetruetrue0.01000.0100falsefalsefalse4truetruetrue0.00810.0081falsefalsefalserr:NonNegativePure4TypepureTotal Annual Fund Operating Expenses. If the Fund is a Feeder Fund, reflect the aggregate expenses of the Feeder Fund and the Master Fund in a single fee table using the captions provided. In a footnote to the fee table, state that the table and Example reflect the expenses of both the Feeder and Master Funds. If the prospectus offers more than one Class of a Multiple Class Fund or more than one Feeder Fund that invests in the same Master Fund, provide a separate response for each Class or Feeder Fund. Base the percentages of "Annual Fund Operating Expenses" on amounts incurred during the Fund's most recent fiscal year, but include in expenses amounts that would have been incurred absent expense reimbursement or fee waiver arrangements. If the Fund has changed its fiscal year and, as a result, the most recent fiscal year is less than three months, use the fiscal year prior to the most recent fiscal year as the basis for determining "Annual Fund Operating Expenses."Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Subsection instructions -Paragraph 3 -Subparagraph d false0Total annual fund operating expenses1Other expenses for Class Y are based on estimated amounts for the current fiscal year.falseAnnual Fund Operating Expenses Dreyfus Opportunistic Midcap Value FundUnKnownUnKnownUnKnownUnKnownfalsefalsefalseSheet44121244026ColumnperiodPeriod*Columndei_LegalEntityAxisAxisck0000914775_S000000461MemberColumnrr_ProspectusShareClassAxisAxis*ColumnunitUnit*RowprimaryElement*falsenonnum:textBlockItemTypenaContains a command for the SEC Viewer for the role corresponding to OperatingExpensesData.No definition available.false0Annual Fund Operating Expenses [Table]11false 4rr_ExpenseExampleHeadingrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00Examplefalsefalsefalsexbrli:stringItemTypestringHeading for Expense Example.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Subsection instructions -Paragraph 4 false0Expense Example [Heading]12false 4rr_ExpenseExampleNarrativeTextBlockrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00 The Example is intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the fund's operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be: falsefalsefalsenonnum:textBlockItemTypenaThe Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Subsection example -Paragraph 1 -Subparagraph 1 false0Expense Example Narrative [Text Block]13false 4rr_ExpenseExampleWithRedemptionTableTextBlockrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00~ http://dreyfus.com/20130625/role/ScheduleExpenseExampleTransposed20027 column dei_LegalEntityAxis compact ck0000914775_S000000461Member row primary compact * ~falsefalse~ http://dreyfus.com/20130625/role/ScheduleExpenseExampleTransposed20027 column dei_LegalEntityAxis compact ck0000914775_S000000461Member row primary compact * ~truehttp://dreyfus.com/20130625/role/ScheduleExpenseExampleTransposed20027020027 - Schedule - Expense Example {Transposed}truefalsefalse1falseColumnprimaryElement*3false 4rr_ExpenseExampleYear01rr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabelrr:NonNegativeMonetaryTypemonetaryThe Example assumes that you invest $10,000 in the Fund for the time periods indicated and then you redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return per year and that the Fund's operating expenses remained the same. Although your actual costs may be higher or lower.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Subsection instructions -Paragraph 4 false21 Year USDfalsefalse$2falseColumnprimaryElement*4false 4rr_ExpenseExampleYear03rr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabelrr:NonNegativeMonetaryTypemonetaryThe Example assumes that you invest $10,000 in the Fund for the time periods indicated and then you redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return per year and that the Fund's operating expenses remained the same. Although your actual costs may be higher or lower.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Subsection example -Paragraph 1 -Subparagraph 2 false23 Years USDfalsefalse$3falseColumnprimaryElement*5false 4rr_ExpenseExampleYear05rr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabelrr:NonNegativeMonetaryTypemonetaryThe Example assumes that you invest $10,000 in the Fund for the time periods indicated and then you redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return per year and that the Fund's operating expenses remained the same. Although your actual costs may be higher or lower.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Subsection example -Paragraph 1 -Subparagraph 2 false25 Years USDfalsefalse$4falseColumnprimaryElement*6false 4rr_ExpenseExampleYear10rr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabelrr:NonNegativeMonetaryTypemonetaryThe Example assumes that you invest $10,000 in the Fund for the time periods indicated and then you redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return per year and that the Fund's operating expenses remained the same. Although your actual costs may be higher or lower.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Subsection example -Paragraph 1 -Subparagraph 2 false210 Years USDfalsefalse$1falseRowperiodPeriod*Rowdei_LegalEntityAxisAxisck0000914775_S000000461MemberRowrr_ProspectusShareClassAxisAxis*RowunitUnit*duration2012-08-31T00:00:002012-08-31T00:00:00falsefalseDreyfus Opportunistic Midcap Value Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000914775_S000000461Memberdei_LegalEntityAxisexplicitMemberfalsefalseClass Arr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000914775_C000001288Memberrr_ProspectusShareClassAxisexplicitMemberDreyfus Opportunistic Midcap Value FundClass AusdStandardhttp://www.xbrl.org/2003/iso4217USDiso42170 0truefalsefalsefalsefalsefalsefalsefalsefalse1truefalsetrue692692falsefalsefalse2truefalsetrue940940falsefalsefalse3truefalsetrue12071207falsefalsefalse4truefalsetrue19671967falsefalsefalsenanafalse0Class A2falseRowperiodPeriod*Rowdei_LegalEntityAxisAxisck0000914775_S000000461MemberRowrr_ProspectusShareClassAxisAxis*RowunitUnit*duration2012-08-31T00:00:002012-08-31T00:00:00falsefalseDreyfus Opportunistic Midcap Value Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000914775_S000000461Memberdei_LegalEntityAxisexplicitMemberfalsefalseClass Crr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000914775_C000064720Memberrr_ProspectusShareClassAxisexplicitMemberDreyfus Opportunistic Midcap Value FundClass CusdStandardhttp://www.xbrl.org/2003/iso4217USDiso42170 0truefalsefalsefalsefalsefalsefalsefalsefalse1truefalsetrue306306falsefalsefalse2truefalsetrue637637falsefalsefalse3truefalsetrue10931093falsefalsefalse4truefalsetrue23582358falsefalsefalsenanafalse0Class C3falseRowperiodPeriod*Rowdei_LegalEntityAxisAxisck0000914775_S000000461MemberRowrr_ProspectusShareClassAxisAxis*RowunitUnit*duration2012-08-31T00:00:002012-08-31T00:00:00falsefalseDreyfus Opportunistic Midcap Value Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000914775_S000000461Memberdei_LegalEntityAxisexplicitMemberfalsefalseClass Irr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000914775_C000064721Memberrr_ProspectusShareClassAxisexplicitMemberDreyfus Opportunistic Midcap Value FundClass IusdStandardhttp://www.xbrl.org/2003/iso4217USDiso42170 0truefalsefalsefalsefalsefalsefalsefalsefalse1truefalsetrue102102falsefalsefalse2truefalsetrue318318falsefalsefalse3truefalsetrue552552falsefalsefalse4truefalsetrue12251225falsefalsefalsenanafalse0Class I4falseRowperiodPeriod*Rowdei_LegalEntityAxisAxisck0000914775_S000000461MemberRowrr_ProspectusShareClassAxisAxis*RowunitUnit*duration2012-08-31T00:00:002012-08-31T00:00:00falsefalseDreyfus Opportunistic Midcap Value Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000914775_S000000461Memberdei_LegalEntityAxisexplicitMemberfalsefalseClass Yrr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000914775_C000130426Memberrr_ProspectusShareClassAxisexplicitMemberDreyfus Opportunistic Midcap Value FundClass YusdStandardhttp://www.xbrl.org/2003/iso4217USDiso42170 0truefalsefalsefalsefalsefalsefalsefalsefalse1truefalsetrue8383falsefalsefalse2truefalsetrue259259falsefalsefalse3truefalsetrue450450falsefalsefalse4truefalsetrue10021002falsefalsefalsenanafalse0Class YfalseExpense Example Dreyfus Opportunistic Midcap Value Fund (USD $)UnKnownUnKnownUnKnownUnKnownfalsefalsefalseSheet44121244044ColumnprimaryElement*RowperiodPeriod*Rowdei_LegalEntityAxisAxisck0000914775_S000000461MemberRowrr_ProspectusShareClassAxisAxis*RowunitUnit*falsenonnum:textBlockItemTypenaContains a command for the SEC Viewer for the role corresponding to ExpenseExample.No definition available.false0Expense Example, With Redemption [Table]14false 4rr_ExpenseExampleNoRedemptionByYearCaptionrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00 You would pay the following expenses if you did not redeem your shares: falsefalsefalsexbrli:stringItemTypestringYou would pay the following expenses if you did not redeem your shares. Include the second 1-, 3-, 5-, and 10-year periods and related narrative explanation only if a sales charge (load) or other fee is charged upon redemption.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Subsection example -Paragraph 2 -Subparagraph 1 false0Expense Example, No Redemption, By Year, Caption [Text]15false 4rr_ExpenseExampleNoRedemptionTableTextBlockrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00~ http://dreyfus.com/20130625/role/ScheduleExpenseExampleNoRedemptionTransposed20028 column dei_LegalEntityAxis compact ck0000914775_S000000461Member row primary compact * ~falsefalse~ http://dreyfus.com/20130625/role/ScheduleExpenseExampleNoRedemptionTransposed20028 column dei_LegalEntityAxis compact ck0000914775_S000000461Member row primary compact * ~truehttp://dreyfus.com/20130625/role/ScheduleExpenseExampleNoRedemptionTransposed20028020028 - Schedule - Expense Example No Redemption {Transposed}truefalsefalse1falseColumnprimaryElement*3false 4rr_ExpenseExampleNoRedemptionYear01rr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabelrr:NonNegativeMonetaryTypemonetaryYou would pay the following expenses if you did not redeem your shares. Include the second 1-, 3-, 5-, and 10-year periods and related narrative explanation only if a sales charge (load) or other fee is charged upon redemption.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Subsection example -Paragraph 2 -Subparagraph 1 false21 Year USDfalsefalse$2falseColumnprimaryElement*4false 4rr_ExpenseExampleNoRedemptionYear03rr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabelrr:NonNegativeMonetaryTypemonetaryYou would pay the following expenses if you did not redeem your shares. Include the second 1-, 3-, 5-, and 10-year periods and related narrative explanation only if a sales charge (load) or other fee is charged upon redemption.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Subsection example -Paragraph 2 -Subparagraph 1 false23 Years USDfalsefalse$3falseColumnprimaryElement*5false 4rr_ExpenseExampleNoRedemptionYear05rr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabelrr:NonNegativeMonetaryTypemonetaryYou would pay the following expenses if you did not redeem your shares. 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Disclose the period for which the information is provided if less than a full fiscal year. A Fund that is a Money Market Fund may omit the portfolio turnover information required by this Item.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Subsection instructions -Paragraph 5 false0Portfolio Turnover [Heading]17false 4rr_PortfolioTurnoverTextBlockrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00 The fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover may indicate higher transaction costs and may result in higher taxes when fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the fund's performance. During the most recent fiscal year, the fund's portfolio turnover rate was 71.25% of the average value of its portfolio. falsefalsefalsenonnum:textBlockItemTypenaDisclose the portfolio turnover rate provided in response to Item 14(a) for the most recent fiscal year (or for such shorter period as the Fund has been in operation). Disclose the period for which the information is provided if less than a full fiscal year. A Fund that is a Money Market Fund may omit the portfolio turnover information required by this Item.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 3 -Subsection example -Paragraph 3 false0Portfolio Turnover [Text Block]18false 4rr_StrategyHeadingrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00Principal Investment Strategyfalsefalsefalsexbrli:stringItemTypestringPrincipal investment strategies of the Fund. Summarize how the Fund intends to achieve its investment objectives by identifying the Fund's principal investment strategies (including the type or types of securities in which the Fund invests or will invest principally) and any policy to concentrate in securities of issuers in a particular industry or group of industries.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection a false0Strategy [Heading]19false 4rr_StrategyNarrativeTextBlockrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00 To pursue its goal, the fund normally invests at least 80% of its net assets, plus any borrowings for investment purposes, in mid-cap stocks with market capitalizations between $1 billion and $25 billion at the time of purchase. Because the fund may continue to hold a security whose market capitalization grows, a substantial portion of the fund's holdings can have market capitalizations in excess of $25 billion at any given time. The fund's portfolio managers identify potential investments through extensive quantitative and fundamental research. The fund focuses on individual stock selection (a "bottom-up" approach), emphasizing three key factors: relative value, business health, and business momentum. In constructing the fund's portfolio, the fund's portfolio managers use an opportunistic value approach to identify stocks whose current market prices trade at a large discount to their intrinsic value, as calculated by the portfolio managers. Intrinsic value is based on the combination of the valuation assessment of the company's operating divisions with its economic balance sheet. The opportunistic value style attempts to benefit from valuation inefficiencies and underappreciated fundamental prospects present in the marketplace. To do this, the portfolio managers use mid-cycle estimates, growth prospects, the identification of a revaluation catalyst and competitive advantages as some of the factors in the valuation assessment. Additionally, a company's stated and hidden liabilities and assets are included in the portfolio managers' economic balance sheet calculation for the company. falsefalsefalsenonnum:textBlockItemTypenaPrincipal investment strategies of the Fund. Summarize how the Fund intends to achieve its investment objectives by identifying the Fund's principal investment strategies (including the type or types of securities in which the Fund invests or will invest principally) and any policy to concentrate in securities of issuers in a particular industry or group of industries.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection a false0Strategy Narrative [Text Block]20false 4rr_RiskHeadingrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00Principal Risksfalsefalsefalsexbrli:stringItemTypestringNarrative Risk Disclosure.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection b -Paragraph 1 false0Risk [Heading]21false 4rr_RiskNarrativeTextBlockrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00 An investment in the fund is not a bank deposit. It is not insured or guaranteed by the Federal Deposit Insurance Corporation (FDIC) or any other government agency. It is not a complete investment program. The fund's share price fluctuates, sometimes dramatically, which means you could lose money. · Risks of stock investing. Stocks generally fluctuate more in value than bonds and may decline significantly over short time periods. There is the chance that stock prices overall will decline because stock markets tend to move in cycles, with periods of rising prices and falling prices. The market value of a stock may decline due to general weakness in the stock market or because of factors that affect the company or its particular industry. · Small and midsize company risk. Small and midsize companies carry additional risks because the operating histories of these companies tend to be more limited, their earnings and revenues less predictable (and some companies may be experiencing significant losses), and their share prices more volatile than those of larger, more established companies. The shares of smaller companies tend to trade less frequently than those of larger, more established companies, which can adversely affect the pricing of these securities and the fund's ability to sell these securities. · Value stock risk. Value stocks involve the risk that they may never reach their expected full market value, either because the market fails to recognize the stock's intrinsic worth or the expected value was misgauged. They also may decline in price even though in theory they are already undervalued. · Market sector risk. The fund may significantly overweight or underweight certain companies, industries or market sectors, which may cause the fund's performance to be more or less sensitive to developments affecting those companies, industries or sectors. · Liquidity risk. When there is little or no active trading market for specific types of securities, it can become more difficult to sell the securities at or near their perceived value. In such a market, the value of such securities and the fund's share price may fall dramatically. falsefalsefalsenonnum:textBlockItemTypenaNarrative Risk Disclosure. A Fund may, in responding to this Item, describe the types of investors for whom the Fund is intended or the types of investment goals that may be consistent with an investment in the Fund.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection b -Paragraph 1 -Subparagraph i -Clause instruction false0Risk Narrative [Text Block]22false 4rr_BarChartAndPerformanceTableHeadingrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00Performancefalsefalsefalsexbrli:stringItemTypestringRisk/Return Bar Chart and Table.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection b -Paragraph 2 false0Bar Chart and Performance Table [Heading]23false 4rr_PerformanceNarrativeTextBlockrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00 The following bar chart and table provide some indication of the risks of investing in the fund. The bar chart shows changes in the performance of the fund's Class A shares from year to year. The table compares the average annual total returns of the fund's shares to those of a broad measure of market performance. The fund's past performance (before and after taxes) is not necessarily an indication of how the fund will perform in the future. Sales charges, if any, are not reflected in the bar chart, and if those charges were included, returns would have been less than those shown. More recent performance information may be available at www.dreyfus.com. Since the fund's Class Y shares are new, past performance information is not available for Class Y shares as of the date of this prospectus. Class Y shares would have had substantially similar annual returns as Class A, C and I shares because each share class is invested in the same portfolio of securities and the annual returns would have differed only to the extent that the classes do not have the same expenses. falsefalsefalsenonnum:textBlockItemTypenaRisk/Return Bar Chart and Table.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection b -Paragraph 2 false0Performance Narrative [Text Block]24false 4rr_BarChartHeadingrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00Year-by-Year Total Returns as of 12/31 each year (%) Class Afalsefalsefalsexbrli:stringItemTypestringRisk/Return Bar Chart and Table.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection b -Paragraph 2 false0Bar Chart [Heading]25false 4rr_BarChartTableTextBlockrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00~ http://dreyfus.com/20130625/role/ScheduleAnnualTotalReturnsBarChart20029 column dei_LegalEntityAxis compact ck0000914775_S000000461Member column rr_ProspectusShareClassAxis compact ck0000914775_C000001288Member row primary compact * ~falsefalseBarChart4.jpg~ http://dreyfus.com/20130625/role/ScheduleAnnualTotalReturnsBarChart20029 column dei_LegalEntityAxis compact ck0000914775_S000000461Member column rr_ProspectusShareClassAxis compact ck0000914775_C000001288Member row primary compact * ~falsehttp://dreyfus.com/20130625/role/ScheduleAnnualTotalReturnsBarChart20029020029 - Schedule - Annual Total Returns [Bar Chart]truefalsefalse1falseColumnperiodPeriod*Columndei_LegalEntityAxisAxisck0000914775_S000000461MemberColumnrr_ProspectusShareClassAxisAxisck0000914775_C000001288MemberColumnunitUnit*duration2012-08-31T00:00:002012-08-31T00:00:00falsefalseDreyfus Opportunistic Midcap Value Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000914775_S000000461Memberdei_LegalEntityAxisexplicitMemberfalsefalseClass Arr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000914775_C000001288Memberrr_ProspectusShareClassAxisexplicitMemberDreyfus Opportunistic Midcap Value FundClass ApureStandardhttp://www.xbrl.org/2003/instancepurexbrli0Standard0 USDfalsefalseduration2012-08-31T00:00:002012-08-31T00:00:00$1falseRowprimaryElement*3false3false 4rr_AnnualReturn2003rr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse0.57500.5750falsefalsefalsexbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection b -Paragraph 2 -Subparagraph instructions -Clause 3 -Exhibit a false0Annual Return 2003 4rr_AnnualReturn2003rr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalsexbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection b -Paragraph 2 -Subparagraph instructions -Clause 3 -Exhibit a false0Annual Return 2003 0rr_AnnualReturn2003rr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse0.57500.5750falsefalsefalsexbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection b -Paragraph 2 -Subparagraph instructions -Clause 3 -Exhibit a false0Annual Return 20032falseRowprimaryElement*4false4false 4rr_AnnualReturn2004rr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse0.17530.1753falsefalsefalsexbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection b -Paragraph 2 -Subparagraph instructions -Clause 3 -Exhibit a false0Annual Return 2004 4rr_AnnualReturn2004rr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalsexbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection b -Paragraph 2 -Subparagraph instructions -Clause 3 -Exhibit a false0Annual Return 2004 0rr_AnnualReturn2004rr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse0.17530.1753falsefalsefalsexbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection b -Paragraph 2 -Subparagraph instructions -Clause 3 -Exhibit a false0Annual Return 20043falseRowprimaryElement*5false5false 4rr_AnnualReturn2005rr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse0.08070.0807falsefalsefalsexbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection b -Paragraph 2 -Subparagraph ii false0Annual Return 2005 4rr_AnnualReturn2005rr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalsexbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection b -Paragraph 2 -Subparagraph ii false0Annual Return 2005 0rr_AnnualReturn2005rr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse0.08070.0807falsefalsefalsexbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection b -Paragraph 2 -Subparagraph ii false0Annual Return 20054falseRowprimaryElement*6false6false 4rr_AnnualReturn2006rr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse0.10440.1044falsefalsefalsexbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection b -Paragraph 2 -Subparagraph ii false0Annual Return 2006 4rr_AnnualReturn2006rr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalsexbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection b -Paragraph 2 -Subparagraph ii false0Annual Return 2006 0rr_AnnualReturn2006rr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse0.10440.1044falsefalsefalsexbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection b -Paragraph 2 -Subparagraph ii false0Annual Return 20065falseRowprimaryElement*7false7false 4rr_AnnualReturn2007rr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse0.05470.0547falsefalsefalsexbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection b -Paragraph 2 -Subparagraph instructions -Clause 3 -Exhibit a false0Annual Return 2007 4rr_AnnualReturn2007rr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalsexbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection b -Paragraph 2 -Subparagraph instructions -Clause 3 -Exhibit a false0Annual Return 2007 0rr_AnnualReturn2007rr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse0.05470.0547falsefalsefalsexbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection b -Paragraph 2 -Subparagraph instructions -Clause 3 -Exhibit a false0Annual Return 20076falseRowprimaryElement*8false8false 4rr_AnnualReturn2008rr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse-0.3984-0.3984falsefalsefalsexbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection b -Paragraph 2 -Subparagraph ii false0Annual Return 2008 4rr_AnnualReturn2008rr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalsexbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection b -Paragraph 2 -Subparagraph ii false0Annual Return 2008 0rr_AnnualReturn2008rr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse-0.3984-0.3984falsefalsefalsexbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection b -Paragraph 2 -Subparagraph ii false0Annual Return 20087falseRowprimaryElement*9false9false 4rr_AnnualReturn2009rr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse0.61760.6176falsefalsefalsexbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection b -Paragraph 2 -Subparagraph instructions -Clause 3 -Exhibit a false0Annual Return 2009 4rr_AnnualReturn2009rr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalsexbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection b -Paragraph 2 -Subparagraph instructions -Clause 3 -Exhibit a false0Annual Return 2009 0rr_AnnualReturn2009rr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse0.61760.6176falsefalsefalsexbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection b -Paragraph 2 -Subparagraph instructions -Clause 3 -Exhibit a false0Annual Return 20098falseRowprimaryElement*10false10false 4rr_AnnualReturn2010rr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse0.25070.2507falsefalsefalsexbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection b -Paragraph 2 -Subparagraph ii false0Annual Return 2010 4rr_AnnualReturn2010rr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalsexbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection b -Paragraph 2 -Subparagraph ii false0Annual Return 2010 0rr_AnnualReturn2010rr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse0.25070.2507falsefalsefalsexbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection b -Paragraph 2 -Subparagraph ii false0Annual Return 20109falseRowprimaryElement*11false11false 4rr_AnnualReturn2011rr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse-0.0581-0.0581falsefalsefalsexbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection b -Paragraph 2 -Subparagraph instructions -Clause 3 -Exhibit a false0Annual Return 2011 4rr_AnnualReturn2011rr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalsexbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection b -Paragraph 2 -Subparagraph instructions -Clause 3 -Exhibit a false0Annual Return 2011 0rr_AnnualReturn2011rr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse-0.0581-0.0581falsefalsefalsexbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection b -Paragraph 2 -Subparagraph instructions -Clause 3 -Exhibit a false0Annual Return 201110falseRowprimaryElement*12false12false 4rr_AnnualReturn2012rr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse0.19410.1941falsefalsefalsexbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection b -Paragraph 2 -Subparagraph ii false0Annual Return 2012 4rr_AnnualReturn2012rr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalsexbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection b -Paragraph 2 -Subparagraph ii false0Annual Return 2012 0rr_AnnualReturn2012rr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1truetruefalse0.19410.1941falsefalsefalsexbrli:pureItemTypepureIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart. When a Multiple Class Fund offers more than one Class in the prospectus, provide annual total returns in the bar chart for only one of those Classes. The Fund can select which Class to include (e.g., the oldest Class, the Class with the greatest net assets).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection b -Paragraph 2 -Subparagraph ii false0Annual Return 2012falseAnnual Total Returns [Bar Chart] UnKnownUnKnownUnKnownUnKnownfalsefalsefalseSheet11009110014ColumnperiodPeriod*Columndei_LegalEntityAxisAxisck0000914775_S000000461MemberColumnrr_ProspectusShareClassAxisAxisck0000914775_C000001288MemberColumnunitUnit*RowprimaryElement*falsenonnum:textBlockItemTypenaContains a command for the SEC Viewer for the role corresponding to BarChartData.No definition available.false0Bar Chart [Table]26false 4rr_BarChartClosingTextBlockrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00 Best Quarter Q2, 2003: 26.41% Worst Quarter Q3, 2011: -24.80% The year-to-date total return of the fund's Class A shares as of March 31, 2013 was 13.67%. falsefalsefalsenonnum:textBlockItemTypenaIf the Fund has annual returns for at least one calendar year, provide a bar chart showing the Fund's annual total returns for each of the last 10 calendar years (or for the life of the Fund if less than 10 years), but only for periods subsequent to the effective date of the Fund's registration statement. Present the corresponding numerical return adjacent to each bar. If the Fund's fiscal year is other than a calendar year, include the year-to-date return information as of the end of the most recent quarter in a footnote to the bar chart. Following the bar chart, disclose the Fund's highest and lowest return for a quarter during the 10 years or other period of the bar chart.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection b -Paragraph 2 -Subparagraph ii false0Bar Chart Closing [Text Block]27false 4rr_AverageAnnualReturnCaptionrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsetruefalse00Average Annual Total Returns (as of 12/31/12)falsefalsefalsexbrli:stringItemTypestringThis item represents Average Anuual Total Returns. If a Multiple Class Fund offers a Class in the prospectus that converts into another Class after a stated period, compute average annual total returns in the table by using the returns of the other Class for the period after conversion.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection b -Paragraph 2 -Subparagraph instructions -Clause 5 false0Caption28false 4rr_PerformanceTableNarrativeTextBlockrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00 After-tax performance is shown only for Class A shares. After-tax performance of the fund's other share classes will vary. After-tax returns are calculated using the historical highest individual federal marginal income tax rates, and do not reflect the impact of state and local taxes. Actual after-tax returns depend on the investor's tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts. For the fund's Class C and I shares, periods prior to May 30, 2008 reflect the performance of the fund's Class A shares adjusted to reflect each share class' applicable sales charge. Such performance figures have not been adjusted, however, to reflect applicable class fees and expenses; if such fees and expenses had been reflected, the performance shown for Class C shares for such periods may have been lower. falsefalsefalsenonnum:textBlockItemTypenaIf the Fund has annual returns for at least one calendar year, provide a table showing the Fund's (A) average annual total return; (B) average annual total return (after taxes on distributions); and (C) average annual total return (after taxes on distributions and redemption). A Money Market Fund should show only the returns described in clause (A) of the preceding sentence. All returns should be shown for 1-, 5-, and 10- calendar year periods ending on the date of the most recently completed calendar year (or for the life of the Fund, if shorter), but only for periods subsequent to the effective date of the Fund's registration statement. The table also should show the returns of an appropriate broad-based securities market index as defined in Instruction 5 to Item 22(b)(7) for the same periods. A Fund that has been in existence for more than 10 years also may include returns for the life of the Fund. A Money Market Fund may provide the Fund's 7-day yield ending on the date of the most recent calendar year or disclose a toll-free (or collect) telephone number that investors can use to obtain the Fund's current 7-day yield. For a Fund (other than a Money Market Fund or a Fund described in General Instruction C.3.(d)(iii)), provide the information in the following table with the specified captions AVERAGE ANNUAL TOTAL RETURNS (For the periods ended December 31, _____). For a Fund that provides annual total returns for only one calendar year or for a Fund that does not include the bar chart because it does not have annual returns for a full calendar year, modify, as appropriate, the narrative explanation required by paragraph (c)(2)(i) (e.g., by stating that the information gives some indication of the risks of an investment in the Fund by comparing the Fund's performance with a broad measure of market performance).Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection b -Paragraph 2 -Subparagraph iv false0Performance Table Narrative29false 4rr_PerformanceTableTextBlockrr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00~ http://dreyfus.com/20130625/role/ScheduleAverageAnnualReturnsTransposed20030 column dei_LegalEntityAxis compact ck0000914775_S000000461Member column rr_PerformanceMeasureAxis compact * row primary compact * ~falsefalse~ http://dreyfus.com/20130625/role/ScheduleAverageAnnualReturnsTransposed20030 column dei_LegalEntityAxis compact ck0000914775_S000000461Member column rr_PerformanceMeasureAxis compact * row primary compact * ~truehttp://dreyfus.com/20130625/role/ScheduleAverageAnnualReturnsTransposed20030020030 - Schedule - Average Annual Returns {Transposed}truefalsefalse1falseColumnprimaryElement*3false 4rr_AverageAnnualReturnYear01rr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabelxbrli:pureItemTypepureReturn Before Taxes.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection b -Paragraph 2 -Subparagraph iii -Clause 1 -Exhibit 2 false0Average Annual Returns, 1 Year USDfalsefalse$2falseColumnprimaryElement*4false 4rr_AverageAnnualReturnYear05rr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabelxbrli:pureItemTypepureReturn Before Taxes.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection b -Paragraph 2 -Subparagraph iii -Clause 1 -Exhibit 2 false0Average Annual Returns, 5 Years USDfalsefalse$3falseColumnprimaryElement*5false 4rr_AverageAnnualReturnYear10rr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabelxbrli:pureItemTypepureReturn Before Taxes.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection b -Paragraph 2 -Subparagraph iii -Clause 1 -Exhibit 2 false0Average Annual Returns, 10 Years USDfalsefalse$4falseColumnprimaryElement*6false 4rr_AverageAnnualReturnInceptionDaterr_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseterseLabelxbrli:dateItemTypedateReturn Before Taxes.Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 4 -Subsection b -Paragraph 2 -Subparagraph instructions -Clause 4 false0Average Annual Returns, Inception Date USDfalsefalse$1falseRowperiodPeriod*Rowdei_LegalEntityAxisAxisck0000914775_S000000461MemberRowrr_PerformanceMeasureAxisAxis*Rowrr_ProspectusShareClassAxisAxis*RowunitUnit*duration2012-08-31T00:00:002012-08-31T00:00:00falsefalseDreyfus Opportunistic Midcap Value Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000914775_S000000461Memberdei_LegalEntityAxisexplicitMembertruefalse[PerformanceMeasureDomain]rr_PerformanceMeasureAxisrr_PerformanceMeasureDomainrr_PerformanceMeasureAxisexplicitMemberfalsefalseClass Arr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000914775_C000001288Memberrr_ProspectusShareClassAxisexplicitMemberDreyfus Opportunistic Midcap Value Fund[PerformanceMeasureDomain]Class ApureStandardhttp://www.xbrl.org/2003/instancepurexbrli0Standard0 0truefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.12530.1253falsefalsefalse2truetruetrue0.05230.0523falsefalsefalse3truetruetrue0.11640.1164falsefalsefalse4falsetruefalse001995-09-29falsefalsetruenanafalse0Class A2falseRowperiodPeriod*Rowdei_LegalEntityAxisAxisck0000914775_S000000461MemberRowrr_PerformanceMeasureAxisAxis*Rowrr_ProspectusShareClassAxisAxis*RowunitUnit*duration2012-08-31T00:00:002012-08-31T00:00:00falsefalseDreyfus Opportunistic Midcap Value Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000914775_S000000461Memberdei_LegalEntityAxisexplicitMembertruefalse[PerformanceMeasureDomain]rr_PerformanceMeasureAxisrr_PerformanceMeasureDomainrr_PerformanceMeasureAxisexplicitMemberfalsefalseClass Crr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000914775_C000064720Memberrr_ProspectusShareClassAxisexplicitMemberDreyfus Opportunistic Midcap Value Fund[PerformanceMeasureDomain]Class CpureStandardhttp://www.xbrl.org/2003/instancepurexbrli0Standard0 0truefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.17450.1745falsefalsefalse2truetruetrue0.05680.0568falsefalsefalse3truetruetrue0.11880.1188falsefalsefalse4falsetruefalse002008-05-30falsefalsetruenanafalse0Class C3falseRowperiodPeriod*Rowdei_LegalEntityAxisAxisck0000914775_S000000461MemberRowrr_PerformanceMeasureAxisAxis*Rowrr_ProspectusShareClassAxisAxis*RowunitUnit*duration2012-08-31T00:00:002012-08-31T00:00:00falsefalseDreyfus Opportunistic Midcap Value Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000914775_S000000461Memberdei_LegalEntityAxisexplicitMembertruefalse[PerformanceMeasureDomain]rr_PerformanceMeasureAxisrr_PerformanceMeasureDomainrr_PerformanceMeasureAxisexplicitMemberfalsefalseClass Irr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000914775_C000064721Memberrr_ProspectusShareClassAxisexplicitMemberDreyfus Opportunistic Midcap Value Fund[PerformanceMeasureDomain]Class IpureStandardhttp://www.xbrl.org/2003/instancepurexbrli0Standard0 0truefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.19590.1959falsefalsefalse2truetruetrue0.06700.0670falsefalsefalse3truetruetrue0.12410.1241falsefalsefalse4falsetruefalse002008-05-30falsefalsetruenanafalse0Class I4falseRowperiodPeriod*Rowdei_LegalEntityAxisAxisck0000914775_S000000461MemberRowrr_PerformanceMeasureAxisAxis*Rowrr_ProspectusShareClassAxisAxis*RowunitUnit*duration2012-08-31T00:00:002012-08-31T00:00:00falsefalseDreyfus Opportunistic Midcap Value Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000914775_S000000461Memberdei_LegalEntityAxisexplicitMemberfalsefalseAfter Taxes on Distributionsrr_PerformanceMeasureAxisxbrldihttp://xbrl.org/2006/xbrldirr_AfterTaxesOnDistributionsMemberrr_PerformanceMeasureAxisexplicitMemberfalsefalseClass Arr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000914775_C000001288Memberrr_ProspectusShareClassAxisexplicitMemberDreyfus Opportunistic Midcap Value FundAfter Taxes on DistributionsClass ApureStandardhttp://www.xbrl.org/2003/instancepurexbrli0Standard0 0truefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.12480.1248falsefalsefalse2truetruetrue0.04650.0465falsefalsefalse3truetruetrue0.10500.1050falsefalsefalse4falsefalsefalse00falsefalsefalsenanafalse0After Taxes on Distributions Class A5falseRowperiodPeriod*Rowdei_LegalEntityAxisAxisck0000914775_S000000461MemberRowrr_PerformanceMeasureAxisAxis*Rowrr_ProspectusShareClassAxisAxis*RowunitUnit*duration2012-08-31T00:00:002012-08-31T00:00:00falsefalseDreyfus Opportunistic Midcap Value Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000914775_S000000461Memberdei_LegalEntityAxisexplicitMemberfalsefalseAfter Taxes on Distributions and Sale of Fund Sharesrr_PerformanceMeasureAxisxbrldihttp://xbrl.org/2006/xbrldirr_AfterTaxesOnDistributionsAndSalesMemberrr_PerformanceMeasureAxisexplicitMemberfalsefalseClass Arr_ProspectusShareClassAxisxbrldihttp://xbrl.org/2006/xbrldick0000914775_C000001288Memberrr_ProspectusShareClassAxisexplicitMemberDreyfus Opportunistic Midcap Value FundAfter Taxes on Distributions and Sale of Fund SharesClass ApureStandardhttp://www.xbrl.org/2003/instancepurexbrli0Standard0 0truefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.08190.0819falsefalsefalse2truetruetrue0.04390.0439falsefalsefalse3truetruetrue0.09990.0999falsefalsefalse4falsefalsefalse00falsefalsefalsenanafalse0After Taxes on Distributions and Sale of Fund Shares Class A6falseRowperiodPeriod*Rowdei_LegalEntityAxisAxisck0000914775_S000000461MemberRowrr_PerformanceMeasureAxisAxis*Rowrr_ProspectusShareClassAxisAxis*RowunitUnit*duration2012-08-31T00:00:002012-08-31T00:00:00falsefalseDreyfus Opportunistic Midcap Value Funddei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldick0000914775_S000000461Memberdei_LegalEntityAxisexplicitMemberfalsefalseRussell Midcap Value Index reflects no deduction for fees, expenses or taxesrr_PerformanceMeasureAxisxbrldihttp://xbrl.org/2006/xbrldick0000914775_index_Russell_Midcap_Value_Index_reflects_no_deduction_for_fees_expenses_or_taxesMemberrr_PerformanceMeasureAxisexplicitMembertruefalse[ShareClassDomain]rr_ProspectusShareClassAxisrr_ShareClassDomainrr_ProspectusShareClassAxisexplicitMemberDreyfus Opportunistic Midcap Value FundRussell Midcap Value Index reflects no deduction for fees, expenses or taxes[ShareClassDomain]pureStandardhttp://www.xbrl.org/2003/instancepurexbrli0Standard0 0truefalsefalsefalsefalsefalsefalsefalsefalse1truetruetrue0.18510.1851falsefalsefalse2truetruetrue0.03790.0379falsefalsefalse3truetruetrue0.10630.1063falsefalsefalse4falsefalsefalse00falsefalsefalsenanafalse0Russell Midcap Value Index reflects no deduction for fees, expenses or taxesfalseAverage Annual Returns Dreyfus Opportunistic Midcap Value 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