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Dreyfus Opportunistic Small Cap Fund  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading Fund Summary
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The fund seeks capital appreciation.
Expense [Heading] rr_ExpenseHeading Fees and Expenses
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the fund.
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Portfolio Turnover [Heading] rr_PortfolioTurnoverHeading Portfolio Turnover
Portfolio Turnover [Text Block] rr_PortfolioTurnoverTextBlock

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 74.06% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 74.06%
Other Expenses, New Fund, Based on Estimates [Text] rr_OtherExpensesNewFundBasedOnEstimates Other expenses for Class I and Class Y shares are estimated amounts for the current fiscal year based on the Other expenses for Investor shares
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

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:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategy
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

To pursue its goal, the fund normally invests at least 80% of its net assets, plus any borrowings for investment purposes, in the stocks of small cap companies. The fund currently considers small cap companies to be those companies with market capitalizations that fall within the range of companies in the Russell 2000® Index, the fund's benchmark index. As of May 27, 2016, the market capitalization of the largest company in the index was approximately $3.86 billion, and the weighted average and median market capitalizations of the index were approximately $1.68 billion and $695 million, respectively. Stocks are selected for the fund's portfolio based primarily on bottom-up fundamental analysis. The fund's portfolio managers use a disciplined investment process that relies, in general, on proprietary fundamental research and valuation. Generally, elements of the process include analysis of a company's business prospects, estimation of the company's value and the identification of events that could cause the estimated value of the company to change. In general, the fund seeks exposure to securities and sectors that the fund's portfolio managers perceive to be attractive from a valuation and fundamental standpoint.
Risk [Heading] rr_RiskHeading Principal Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock

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 market conditions or because of factors that affect the particular company or the company's 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.


· Growth and value stock risk. By investing in a mix of growth and value companies, the fund assumes the risks of both. Investors often expect growth companies to increase their earnings at a certain rate. If these expectations are not met, investors can punish the stocks inordinately, even if earnings do increase. In addition, growth stocks may lack the dividend yield that may cushion stock prices in market downturns. 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 in a timely manner at or near their perceived value. In such a market, the value of such securities and the fund's share price may fall dramatically. Investments that are illiquid or that trade in lower volumes may be more difficult to value. Investments in foreign securities tend to have greater exposure to liquidity risk than domestic securities.
Risk Lose Money [Text] rr_RiskLoseMoney The fund's share price fluctuates, sometimes dramatically, which means you could lose money.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution 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.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

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 Investor 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. More recent performance information may be available at www.dreyfus.com.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The following bar chart and table provide some indication of the risks of investing in the fund.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.dreyfus.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture The fund's past performance (before and after taxes) is not necessarily an indication of how the fund will perform in the future.
Bar Chart [Heading] rr_BarChartHeading Year-by-Year Total Returns as of 12/31 each year (%)
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Best Quarter
Q2, 2009: 28.46%


Worst Quarter
Q3, 2011: -30.21%


The year-to-date total return of the fund's Investor shares as of June 30, 2016 was 3.38%.
Year to Date Return, Label rr_YearToDateReturnLabel year-to-date total return
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Jun. 30, 2016
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn 3.38%
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2009
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 28.46%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Sep. 30, 2011
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (30.21%)
Index No Deduction for Fees, Expenses, Taxes [Text] rr_IndexNoDeductionForFeesExpensesTaxes reflects no deduction for fees, expenses or taxes
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate 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.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred 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 U.S. tax-deferred arrangements such as 401(k) plans or individual retirement accounts.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax performance is shown only for Investor shares. After-tax performance of the fund's other share classes will vary.
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock

After-tax performance is shown only for Investor 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 U.S. tax-deferred arrangements such as 401(k) plans or individual retirement accounts.


For the fund's Class I and Class Y shares, periods prior to the class' inception date reflect the performance of the fund's Investor shares. Such performance figures have not been adjusted to reflect applicable class fees and expenses. 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.
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (as of 12/31/15)
Dreyfus Opportunistic Small Cap Fund | Russell 2000 Index reflects no deduction for fees, expenses or taxes  
Risk/Return: rr_RiskReturnAbstract  
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (4.41%)
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 9.19%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 6.80%
Dreyfus Opportunistic Small Cap Fund | Investor  
Risk/Return: rr_RiskReturnAbstract  
Management fees rr_ManagementFeesOverAssets 0.75%
Other expenses (including shareholder services fees) rr_OtherExpensesOverAssets 0.34%
Total annual fund operating expenses rr_ExpensesOverAssets 1.09%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 111
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 347
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 601
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,329
Annual Return 2006 rr_AnnualReturn2006 5.04%
Annual Return 2007 rr_AnnualReturn2007 4.91%
Annual Return 2008 rr_AnnualReturn2008 (31.91%)
Annual Return 2009 rr_AnnualReturn2009 64.33%
Annual Return 2010 rr_AnnualReturn2010 32.35%
Annual Return 2011 rr_AnnualReturn2011 (14.35%)
Annual Return 2012 rr_AnnualReturn2012 20.73%
Annual Return 2013 rr_AnnualReturn2013 47.79%
Annual Return 2014 rr_AnnualReturn2014 1.02%
Annual Return 2015 rr_AnnualReturn2015 (2.71%)
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (2.71%)
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 8.47%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 9.38%
Dreyfus Opportunistic Small Cap Fund | Investor | After Taxes on Distributions  
Risk/Return: rr_RiskReturnAbstract  
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (3.61%)
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 6.13%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 7.41%
Dreyfus Opportunistic Small Cap Fund | Investor | After Taxes on Distributions and Sale of Fund Shares  
Risk/Return: rr_RiskReturnAbstract  
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (0.78%)
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 6.26%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 7.24%
Dreyfus Opportunistic Small Cap Fund | Class I  
Risk/Return: rr_RiskReturnAbstract  
Management fees rr_ManagementFeesOverAssets 0.75%
Other expenses (including shareholder services fees) rr_OtherExpensesOverAssets 0.09% [1]
Total annual fund operating expenses rr_ExpensesOverAssets 0.84%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 86
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 268
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 466
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,037
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (2.71%)
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 8.47%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 9.38%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Sep. 30, 2016
Dreyfus Opportunistic Small Cap Fund | Class Y  
Risk/Return: rr_RiskReturnAbstract  
Management fees rr_ManagementFeesOverAssets 0.75%
Other expenses (including shareholder services fees) rr_OtherExpensesOverAssets 0.05% [1]
Total annual fund operating expenses rr_ExpensesOverAssets 0.80%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 82
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 255
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 444
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 990
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 (2.71%)
Average Annual Returns, 5 Years rr_AverageAnnualReturnYear05 8.47%
Average Annual Returns, 10 Years rr_AverageAnnualReturnYear10 9.38%
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Sep. 30, 2016
[1] Other expenses for Class I and Class Y shares are estimated amounts for the current fiscal year based on the Other expenses for Investor shares