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Class T Prospectus | Dreyfus MLP 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 total return (consisting of capital appreciation and income).
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. You may qualify for sales charge discounts if you invest at least $250,000 in the fund. More information about sales charges, including such discounts, is available from your financial professional and in the Shareholder Guide section beginning on page 20 of the 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.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder Fees (fees paid directly from your investment)
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)
Fee Waiver or Reimbursement over Assets, Date of Termination rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination Mar. 31, 2018
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 111.44% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 111.44%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for sales charge discounts if you invest at least $250,000 in the fund.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 250,000
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 hold or 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. The one-year example and the first year of the three-, five- and ten-years examples are based on net operating expenses, which reflect the expense limitation by The Dreyfus Corporation. 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 master limited partnership (MLP) investments. MLPs in which the fund normally invests own and operate assets that are used in the energy sector, including assets used in exploring, developing, producing, generating, transporting (including marine), transmitting, terminalling, storing, gathering, processing, refining, distributing, mining or marketing of natural gas, natural gas liquids, crude oil, refined products, coal, electricity or alternative fuels (such as ethanol, hydrogen and biodiesel), or that provide energy-related equipment or services. The fund's MLP investments may include, but are not limited to: MLPs structured as limited partnerships (LPs) or limited liability companies (LLCs); MLPs that are taxed as "C" corporations; institutional units issued by MLP affiliates that represent indirect interests in MLPs; "C" corporations that hold significant interests in MLPs; private investments in public equities (PIPEs) issued by MLPs; and other U.S. and non-U.S. equity (principally common stocks) and debt securities (principally bonds and notes) and derivative instruments, including pooled investment vehicles, such as exchange traded funds (ETFs), and exchange-traded notes (ETNs), that provide exposure to MLPs. The fund's MLP investments may be of any market capitalization size and any credit quality (including "high yield" or "junk" bonds), maturity or duration.


The fund intends to concentrate its investments, under normal circumstances, in the energy sector, primarily investing in "midstream" energy infrastructure MLPs. The industries deemed to be included in the energy sector are energy equipment and services, oil, gas and consumable fuels, electric utilities, gas utilities, multi-utilities, and independent power and renewable electricity producers. Midstream MLPs generally are engaged in the treatment, gathering, compression, processing, transportation, transmission, fractionation, storage and terminalling of natural gas, natural gas liquids, crude oil, refined products or coal. Midstream MLPs also may operate ancillary businesses including marketing of energy products and logistical services. The fund also may invest in "upstream" and "downstream" MLPs. Upstream MLPs are engaged primarily in the exploration, recovery, development and production of crude oil, natural gas and natural gas liquids. Downstream MLPs are engaged primarily in the processing, treatment, and refining of natural gas liquids and crude oil.


The fund's portfolio managers employ a bottom-up fundamental and event driven process to select MLP investments for the fund's portfolio. The fund's portfolio managers evaluate both fundamental drivers and financial structure drivers that can impact cash flow growth and valuation. The fund's performance benchmark index is the Alerian MLP Index.


The fund may maintain significant short positions. The fund, however, intends to maintain an overall long position in its portfolio investments, with short positions ranging typically between 10% and 30% of the fund's net assets. A short sale involves the sale of a security that the fund does not own in the expectation of purchasing the same security (or a security exchangeable therefor) at a later date and at a lower price. The fund will incur a loss as a result of a short sale if the price of the security increases between the date of the short sale and the date on which the fund replaces the security sold short. The fund will realize a gain if the security declines in price between those two dates. The fund's potential loss is limited only by the maximum attainable price of the security less the price at which the security was sold.


The fund may utilize leverage through borrowings, engaging in short sales, or entering into derivative transactions in seeking its objective.


The fund may use derivative or other strategic instruments, principally options, futures and options on futures (including those relating to securities, foreign currencies, indices, and interest rates), contracts for difference, forward contracts, swap agreements (including total return, interest rate and credit default swaps), and options on swaps, as a substitute for investing directly in an underlying asset, as an alternative to selling a security short, to increase returns, to manage foreign currency, credit or interest rate risk, to manage effective maturity or duration, as part of a hedging strategy, or for other purposes related to the management of the fund. There is no limit to the amount of the fund's assets that may be invested in derivative instruments. To the extent such instruments have similar economic characteristics to MLP investments as described in the fund's policy with respect to the investment of at least 80% of its net assets, these investments will be considered investments included within such policy. When the fund enters derivatives transactions, it may be required to segregate liquid assets or enter into offsetting positions, in accordance with applicable regulations.


The fund is treated as a regular corporation, or "C" corporation, for U.S. federal income tax purposes so that, unlike traditional open-end mutual funds, the fund does not have flow-through tax treatment but instead is subject to U.S. federal income tax on its taxable income at the graduated rates applicable to corporations (currently with a maximum rate of 35%), as well as state and local income taxes. Accordingly, the fund's earnings and gains are subject to income tax prior to distribution to shareholders, and shareholders in turn may be subject to income tax on distributions received from the fund. In calculating the fund's daily net asset value, the fund will, among other things, account for its deferred tax liability and/or asset balances.
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.


· MLP risk. An investment in MLP units involves some risks that differ from an investment in the common stock of a corporation. The risks of investing in an MLP are generally those involved in investing in a partnership as opposed to a corporation. For example, state law governing partnerships is often less restrictive than state law governing corporations. Accordingly, there may be fewer protections afforded investors in an MLP than investors in a corporation, and holders of MLP units have limited control on matters affecting the partnership. Investing in MLPs involves certain risks related to investing in the underlying assets of the MLPs and risks associated with pooled investment vehicles. The benefit derived from the fund's investment in MLPs is largely dependent on the MLPs being treated as partnerships for U.S. federal income tax purposes. A change in current tax law, or a change in the business of a given MLP, could result in an MLP being treated as a corporation for U.S. federal income tax purposes and subject to corporate level tax on its income, and could reduce the amount of cash available for distribution by the MLP to its unit holders, such as the fund.


· Energy sector risk. Under normal circumstances, the fund concentrates its investments in the energy sector, primarily investing in energy infrastructure MLPs, and may, therefore, be more susceptible to the risks affecting such sector and MLPs. MLPs and other companies operating in the energy sector are subject to specific risks, including, among others, fluctuations in commodity prices; reduced consumer demand for commodities such as oil, natural gas or petroleum products; reduced availability of natural gas or other commodities for transporting, processing, storing or delivering; slowdowns in new construction; extreme weather or other natural disasters; and threats of attack by terrorists on energy assets. Additionally, energy sector companies are subject to substantial government regulation and changes in the regulatory environment for energy companies may adversely impact their profitability. MLPs may incur environmental costs and liabilities due to the nature of their businesses and the substances they handle. Changes in existing laws, regulations or enforcement policies governing the energy sector could significantly increase the compliance costs of MLPs. Certain MLPs could be required to implement remediation measures, the cost of which may not be recoverable from insurance. Over time, depletion of natural gas reserves and other energy reserves may also affect the profitability of energy companies. The pool of issuers of MLP investments in which the fund may invest may be limited; thus, demand for investment opportunities in MLPs that operate energy-related businesses may exceed the supply, which could make it difficult for the fund to fully implement its investment strategy.


· Fund structure risk. The fund's strategy of investing primarily in MLPs and electing to be structured as a corporation, or a "C" corporation, rather than as a regulated investment company for U.S. federal income tax purposes, means the fund generally will be subject to U.S. federal income tax on its taxable income at the rates applicable to corporations, and will be subject to state and local income taxes. This is a relatively new strategy for mutual funds and involves complicated accounting, tax and valuation issues that may cause the fund to differ significantly from most other open-end registered investment companies. The fund may have to use estimates of its income and expenses at various times during a given year that may result in volatility in the fund's net asset value and potentially significant consequences for the fund and its shareholders.


· MLP investment tax risk. Tax risks associated with the fund's MLP investments include but are not limited to the following:


MLP tax risk. Although the fund’s MLP investments may take various forms, it is expected that the fund will invest primarily in MLP's that are classified as partnerships for U.S. federal income tax purposes (pass-through MLPs). The benefit expected from the fund's pass-through MLP investments generally will depend on those MLPs being treated as partnerships for U.S. federal income tax purposes. Partnerships do not pay U.S. federal income tax at the partnership level. Rather, each partner is allocated a share of the partnership's income, gains, losses, deductions and expenses. A change in current tax law (or the interpretation thereof), or a change in the business of a given pass-through MLP, could result in that MLP being treated as a corporation for U.S. federal income tax purposes, which would result in that MLP being required to pay U.S. federal income tax (as well as state and local income taxes) on its taxable income. The classification of an MLP as a corporation for U.S. federal income tax purposes would have the effect of reducing the amount of cash available for distribution by that MLP. If any MLP in which the fund invests were treated as a corporation for U.S. federal income tax purposes, it could result in a reduction of the value of the fund's investment in that MLP and lower income to the fund.


To the extent a distribution received by the fund from a pass-through MLP investment is treated as a return of capital, the fund's adjusted tax basis in that MLP interest may be reduced, which will result in an increase in an amount of gain (or decrease in the amount of loss) recognized by the fund for tax purposes upon the sale of any such interest or upon subsequent distributions in respect of such interest. The final portions of the distributions received by the fund from its pass-through MLP investments considered return of capital will not be known until the fund receives Schedule K-1s from such MLP investments. Accordingly, any return of capital distribution received from a pass-through MLP investment may require the fund to restate the character of its distributions and amend any shareholder tax reporting previously issued.


Tax estimation/NAV risk. In calculating the fund's net asset value (NAV), the fund will, among other things, account for its current taxes and deferred tax liability and/or asset balances. The fund may accrue a deferred income tax liability balance at the rates applicable to corporations, plus an estimated state and local income tax rate, for its future tax liability associated with the capital appreciation of its investments and any return of capital distributions received by the fund on equity securities of MLPs that result in a reduction in the fund’s adjusted tax basis in those interests and for any net operating gains. Any deferred tax liability balance will reduce the fund's NAV. The fund also may accrue a deferred tax asset balance, which reflects an estimate of the fund's future tax benefit associated with net operating losses and unrealized losses. Any deferred tax asset balance will increase the fund's NAV. To the extent the fund has a deferred tax asset balance, the fund will assess whether or not a valuation allowance, which would offset the value of some or all of the deferred tax asset balance, is required. To the extent a valuation allowance differs from the estimates of the fund used in calculating the fund's daily NAV, the application of such valuation allowance could have a material impact on the fund's NAV.


The fund's deferred tax liability and/or asset balances are estimated using estimates of effective tax rates expected to apply to taxable income in the years such balances are realized. From time to time, the fund may modify its estimates or assumptions regarding its current taxes and deferred tax liability and/or asset balances as new information becomes available, which modifications in estimates or assumptions may have a material impact on the fund's NAV.


· Fund distribution policy risk. The fund's dividend distribution policy is intended to provide investors with a dividend distribution rate similar to owning MLPs directly. Under the policy, the fund intends to pay out a consistent dividend that over time approximates the distributions received from the fund's portfolio investments based on, among other considerations, distributions the fund actually received from portfolio investments and estimated future cash flows. Such dividends are not tied to the fund's investment income and may not represent yield or investment return on the fund's portfolio. To the extent that the dividends paid by the fund exceed the distributions the fund receives from its underlying investments, the fund's assets will decline. A decline in the fund's assets may result in an increase in the fund's expense ratio and over time the dividends paid by the fund in excess of distributions received by the fund could erode the fund's net asset value.


Due to the tax characterization of distributions made by MLPs, the fund anticipates that a significant portion of its distributions to shareholders will constitute a return of capital for U.S. federal income tax purposes. In general, a distribution will constitute a return of capital, rather than a qualified dividend, to the extent it exceeds the fund's current and accumulated earnings and profits. Return of capital reduces a shareholder's adjusted cost basis in the fund's shares.


· Issuer risk. A security's market value may decline for a number of reasons which directly relate to the issuer, such as management performance, financial leverage and reduced demand for the issuer's products or services, or factors that affect the issuer's industry, such as labor shortages or increased production costs and competitive conditions within an industry.


· 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.


· Market capitalization risk (small-, mid- and large-cap stock risk). To the extent the fund emphasizes small-, mid- or large-cap stocks, it will assume the associated risks. At any given time, any of these market capitalizations may be out of favor with investors. Compared to small- and mid-cap companies, large-cap companies may be less responsive to changes and opportunities affecting their business. To the extent the fund invests in small- and mid-cap companies, it will be subject to 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. Smaller companies may have limited product lines, markets or financial resources, or may depend on a limited management group.


· Fixed-income market risk. The market value of a fixed-income security may decline due to general market conditions that are not specifically related to a particular company, such as real or perceived adverse economic conditions, changes in the outlook for corporate earnings, changes in interest or currency rates or adverse investor sentiment generally. The fixed-income securities market can be susceptible to increases in volatility and decreases in liquidity. Liquidity can decline unpredictably in response to overall economic conditions or credit tightening. Increases in volatility and decreases in liquidity may be caused by a rise in interest rates (or the expectation of a rise in interest rates), which currently are at or near historic lows in the United States and in other countries. An unexpected increase in fund redemption requests, including requests from shareholders who may own a significant percentage of the fund's shares, which may be triggered by market turmoil or an increase in interest rates, could cause the fund to sell its holdings at a loss or at undesirable prices and adversely affect the fund's share price and increase the fund's liquidity risk, fund expenses and/or taxable distributions.


· Interest rate risk. Prices of bonds and other fixed rate fixed-income securities tend to move inversely with changes in interest rates. Typically, a rise in rates will adversely affect fixed-income securities and, accordingly, will cause the value of the fund's investments in these securities to decline. During periods of very low interest rates, which occur from time to time due to market forces or actions of governments and/or their central banks, including the Board of Governors of the Federal Reserve System in the U.S., the fund may be subject to a greater risk of principal decline from rising interest rates. When interest rates fall, the fund's investments in new securities may be at lower yields and may reduce the fund's income. The magnitude of these fluctuations in the market price of fixed-income securities is generally greater for securities with longer effective maturities and durations because such instruments do not mature, reset interest rates or become callable for longer periods of time. The change in the value of a fixed-income security or portfolio can be approximated by multiplying its duration by a change in interest rates. For example, the market price of a fixed-income security with a duration of three years would be expected to decline 3% if interest rates rose 1%. Conversely, the market price of the same security would be expected to increase 3% if interest rates fell 1%. Risks associated with rising interest rates are heightened given that interest rates in the United States and other countries currently are at or near historic lows. In the event that the fund has a negative average effective duration, the value of the fund may decline in a declining interest rate environment. Unlike investment grade bonds, however, the prices of high yield ("junk") bonds may fluctuate unpredictably and not necessarily inversely with changes in interest rates.


· Credit risk. Failure of an issuer of a security to make timely interest or principal payments when due, or a decline or perception of a decline in the credit quality of the security, can cause the security's price to fall. The lower a security's credit rating, the greater the chance that the issuer of the security will default or fail to meet its payment obligations.


· High yield securities risk. High yield ("junk") securities involve greater credit risk, including the risk of default, than investment grade securities, and are considered predominantly speculative with respect to the issuer's ability to make principal and interest payments. The prices of high yield securities can fall in response to bad news about the issuer or its industry, or the economy in general, to a greater extent than those of higher rated securities.


· Foreign investment risk. To the extent the fund invests in foreign securities, the fund's performance will be influenced by political, social and economic factors affecting investments in foreign issuers. Special risks associated with investments in foreign issuers include exposure to currency fluctuations, less liquidity, less developed or less efficient trading markets, lack of comprehensive company information, political and economic instability and differing auditing and legal standards. Investments denominated in foreign currencies are subject to the risk that such currencies will decline in value relative to the U.S. dollar and affect the value of these investments held by the fund.


· 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, even during periods of declining interest rates. Investments that are illiquid or that trade in lower volumes may be more difficult to value. The market for below investment grade securities may be less liquid and therefore these securities may be harder to value or sell at an acceptable price, especially during times of market volatility or decline. Investments in foreign securities tend to have greater exposure to liquidity risk than domestic securities. Liquidity risk also may refer to the risk that the fund will not be able to pay redemption proceeds within the allowable time period stated in this prospectus because of unusual market conditions, an unusually high volume of redemption requests, or other reasons. To meet redemption requests, the fund may be forced to sell securities at an unfavorable time and/or under unfavorable conditions, which may adversely affect the fund's share price.


· Short sale risk. The fund may make short sales, which involves selling a security it does not own in anticipation that the security's price will decline. Short sales expose the fund to the risk that it will be required to buy the security sold short (also known as "covering" the short position) at a time when the security has appreciated in value, thus resulting in a loss to the fund. Short positions in stocks involve more risk than long positions in stocks because the maximum sustainable loss on a stock purchased is limited to the amount paid for the stock plus the transaction costs, whereas there is no maximum attainable price on the shorted stock. As such, theoretically, stocks sold short have unlimited risk. The fund may not always be able to close out a short position at a particular time or at an acceptable price. The fund may not always be able to borrow a security the fund seeks to sell short at a particular time or at an acceptable price. Thus, there is a risk that the fund may be unable to engage in short selling due to a lack of available stocks or for some other reason.


· ETF and other investment company risk. To the extent the fund invests in pooled investment vehicles, such as investment companies and ETFs, the fund will be affected by the investment policies, practices and performance of such entities in direct proportion to the amount of assets the fund has invested therein. The risks of investing in other investment companies, including ETFs, typically reflect the risks associated with the types of instruments in which the investment companies and ETFs invest. When the fund invests in another investment company or an ETF, shareholders of the fund will bear indirectly their proportionate share of the expenses of the other investment company or the ETF (including management fees) in addition to the expenses of the fund.


· ETN risk. ETNs are debt securities that combine certain aspects of ETFs and bonds. ETNs are not investment companies and thus are not regulated under the Investment Company Act of 1940, as amended. ETNs, like ETFs, are traded on stock exchanges and generally track specified market indices, and their value depends on the performance of the underlying index and the credit rating of the issuer.


· Derivatives risk. A small investment in derivatives could have a potentially large impact on the fund's performance. The use of derivatives involves risks different from, or possibly greater than, the risks associated with investing directly in the underlying assets, and the fund's use of derivatives may result in losses to the fund. Derivatives in which the fund may invest can be highly volatile, illiquid and difficult to value, and there is the risk that changes in the value of a derivative held by the fund will not correlate with the underlying assets or the fund's other investments in the manner intended. Certain derivatives have the potential for unlimited loss, regardless of the size of the initial investment. Certain types of derivatives, including over-the-counter transactions, involve greater risks than the underlying assets because, in addition to general market risks, they are subject to liquidity risk, credit and counterparty risk (failure of the counterparty to the derivatives transaction to honor its obligation) and pricing risk (risk that the derivative cannot or will not be accurately valued). Future rules and regulations of the Securities and Exchange Commission (SEC) may require the fund to alter, perhaps materially, its use of derivatives.


· Leverage risk. The use of leverage, such as borrowing for investment purposes, entering into contracts for difference, swap agreements, futures contracts or forward currency contracts, and engaging in forward commitment transactions, may magnify the fund's gains or losses. Short sales involve borrowing securities and then selling them; thus, the fund's short sales positions effectively leverage the fund's assets.


· High portfolio turnover risk. The fund may engage in active and frequent trading, which could produce higher transactions costs and taxable distributions, and lower the fund's after-tax performance.


· Non-diversification risk. The fund is non-diversified, which means that the fund may invest a relatively high percentage of its assets in a limited number of issuers. Therefore, the fund's performance may be more vulnerable to changes in the market value of a single issuer or group of issuers and more susceptible to risks associated with a single economic, political or regulatory occurrence than a diversified fund.

Risk Lose Money [Text] rr_RiskLoseMoney The fund's share price fluctuates, sometimes dramatically, which means you could lose money.
Risk Nondiversified Status [Text] rr_RiskNondiversifiedStatus The fund is non-diversified, which means that the fund may invest a relatively high percentage of its assets in a limited number of issuers. Therefore, the fund's performance may be more vulnerable to changes in the market value of a single issuer or group of issuers and more susceptible to risks associated with a single economic, political or regulatory occurrence than a diversified fund.
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. It is not a complete investment program.
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 the performance of the fund's Class T shares for its first full calendar year of operations. Sales charges are not reflected in the bar chart, and, if those charges were included, returns would have been less than those shown. The table compares the average annual total returns of the fund's Class T 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.


The historical performance of the fund's Class A shares, which are not offered in this prospectus, is used to calculate the performance of the fund's Class T shares shown in the bar chart and table. Since the fund's Class T shares are new, past performance information is not available for Class T shares as of the date of this prospectus. 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 charges and expenses. The performance figures in the table have been adjusted to reflect the sales load applicable to the fund's Class T shares. The performance figures have not been adjusted to reflect applicable class fees and expenses.
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 One Year or Less [Text] rr_PerformanceOneYearOrLess Since the fund's Class T shares are new, past performance information is not available for Class T shares as of the date of this prospectus.
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 (%) Class T*
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads Sales charges are not reflected in the bar chart, and, if those charges were included, returns would have been less than those shown.
Bar Chart Footnotes [Text Block] rr_BarChartFootnotesTextBlock

* Reflects the performance of the fund's Class A shares, which are offered in a separate prospectus. Such performance figures have not been adjusted to reflect applicable class fees and expenses.
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock

Best Quarter
Q2, 2016: 18.63%


Worst Quarter
Q1, 2016: -2.78%
Bar Chart, Returns for Class Not Offered in Prospectus [Text] rr_BarChartReturnsForClassNotOfferedInProspectus The historical performance of the fund's Class A shares, which are not offered in this prospectus, is used to calculate the performance of the fund's Class T shares shown in the bar chart and table.
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best Quarter
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2016
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 18.63%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst Quarter
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2016
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (2.78%)
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 Explanation after Tax Higher rr_PerformanceTableExplanationAfterTaxHigher Returns after taxes on distributions and sale of fund shares may be higher than returns before taxes or returns after taxes on distributions due to an assumed tax benefit from losses on a sale of the fund’s shares at the end of the period.
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock

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. Returns after taxes on distributions and sale of fund shares may be higher than returns before taxes or returns after taxes on distributions due to an assumed tax benefit from losses on a sale of the fund’s shares at the end of the period.
Caption rr_AverageAnnualReturnCaption Average Annual Total Returns (as of 12/31/16)
Class T Prospectus | Dreyfus MLP Fund | Alerian MLP Index reflects no deduction for fees, expenses or taxes  
Risk/Return: rr_RiskReturnAbstract  
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 18.31%
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception (13.02%)
Class T Prospectus | Dreyfus MLP Fund | Class T  
Risk/Return: rr_RiskReturnAbstract  
Maximum sales charge (load) imposed on purchases (as a percentage of offering price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 2.50%
Maximum deferred sales charge (load) (as a percentage of lower of purchase or sale price) rr_MaximumDeferredSalesChargeOverOther none
Management fees rr_ManagementFeesOverAssets 1.00%
Distribution/service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other expenses - Dividend and interest expense on securities sold short rr_Component2OtherExpensesOverAssets 0.62%
Other expenses - Other expenses rr_Component3OtherExpensesOverAssets 1.37%
Income tax expense rr_OtherExpensesOverAssets none [1]
Total annual fund operating expenses rr_ExpensesOverAssets 3.24%
Fee waiver and/or expense reimbursement rr_FeeWaiverOrReimbursementOverAssets (1.12%) [2]
Total annual fund operating expenses (after fee waiver and/or expense reimbursement) rr_NetExpensesOverAssets 2.12%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 460
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 1,121
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,806
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 3,627
Class T Prospectus | Dreyfus MLP Fund | Class A  
Risk/Return: rr_RiskReturnAbstract  
Annual Return 2016 rr_AnnualReturn2016 26.09%
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 22.94% [3],[4]
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception (13.45%) [3],[4]
Average Annual Returns, Inception Date rr_AverageAnnualReturnInceptionDate Apr. 30, 2015 [3],[4]
Class T Prospectus | Dreyfus MLP Fund | Class A | After Taxes on Distributions  
Risk/Return: rr_RiskReturnAbstract  
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 19.78% [4]
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception (15.31%) [4]
Class T Prospectus | Dreyfus MLP Fund | Class A | After Taxes on Distributions and Sale of Fund Shares  
Risk/Return: rr_RiskReturnAbstract  
Average Annual Returns, 1 Year rr_AverageAnnualReturnYear01 12.84% [4]
Average Annual Returns, Since Inception rr_AverageAnnualReturnSinceInception (11.01%) [4]
[1] The fund accrues for its deferred tax liability associated with the capital appreciation of its investments, distributions it receives on interests of master limited partnerships considered to be a return of capital, and for any net operating gains. The fund's accrued deferred tax liability, if any, will be reflected each day in the fund's net asset value per share. The fund's deferred tax liability will depend upon income, gains, losses, and deductions the fund is allocated from its master limited partnership investments and on the fund's realized and unrealized gains and losses, and may vary greatly from year to year. Any estimate of deferred tax liability cannot be reliably predicted from year to year.
[2] The fund's investment adviser, The Dreyfus Corporation, has contractually agreed, until March 31, 2018, to waive receipt of its fees and/or assume the direct expenses of Class T shares of the fund so that the expenses of such Class T shares do not exceed 1.25% (excluding Rule 12b-1 fees, dividend and interest expenses on securities sold short, taxes (such as deferred income tax expenses), interest, brokerage commissions, commitment fees on borrowings and extraordinary expenses). On or after March 31, 2018, The Dreyfus Corporation may terminate this expense limitation at any time.
[3] Inception date of Class A shares.
[4] Reflects the performance of the fund's Class A shares, which are offered in a separate prospectus, adjusted to reflect applicable sales charges. Such performance figures have not been adjusted to reflect applicable class fees and expenses.