v3.26.3
Investment Risks
Sep. 25, 2026
ARBITRAGE FUND | ARBITRAGE FUND | Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] As with all mutual funds, investing in the Fund entails risks that could cause the Fund and you to lose money.
ARBITRAGE FUND | ARBITRAGE FUND | Merger Arbitrage Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Merger Arbitrage Risk: The principal risk associated with the Fund’s merger arbitrage investment strategy is that the proposed corporate reorganizations in which the Fund invests may not be completed or may be completed on less favorable terms than originally anticipated, in which case the Fund may realize losses.

ARBITRAGE FUND | ARBITRAGE FUND | Short Sale Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Short Sale Risk: The Fund may obtain short exposure by borrowing a security to sell or by trading a derivative instrument that has a similar economic effect, such as a future, forward or swap. The Fund will suffer a loss if it sells a security short and the value of the security rises rather than falls. There is no theoretical ceiling to the price of a shorted security. Therefore, in theory, securities sold short have unlimited risk. Short sales also 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. The Fund’s investment performance may also suffer if it is required to close out a short position earlier than it had intended. In addition, the Fund may be subject to expenses related to short sales that are not typically associated with investing in securities directly, such as costs of borrowing. These expenses may negatively impact the Fund’s performance. When the Fund sells a security short, it must maintain cash or high-grade securities equal to the margin requirement. As a result, the Fund may maintain high levels of cash or other liquid assets (such as U.S. Treasury bills, money market instruments, certificates of deposit, high quality commercial paper, and long equity positions). The need to maintain cash or other liquid assets could limit the Fund’s ability to pursue other opportunities as they arise. Short exposure generally introduces more risk to the Fund than long positions (purchases). It is also possible that the Fund’s long positions will decline in value at the same time that the value of its short positions increases, thereby increasing potential losses to the Fund.

ARBITRAGE FUND | ARBITRAGE FUND | Active Management Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Active Management Risk: The Fund is an actively managed investment portfolio and is therefore subject to management risk. The Adviser will apply its investment and risk analysis in making investment decisions for the Fund, but there is no guarantee that these decisions will produce the intended results.

ARBITRAGE FUND | ARBITRAGE FUND | Concentration Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Concentration Risk: If a large percentage of mergers or other corporate events taking place within the U.S. are within one industry over a given period of time, the Fund may invest a large portion of its assets in securities of issuers in a single industry for that period of time. During such a period of concentration, the Fund may be subject to greater volatility with respect to its portfolio securities than a fund that is more broadly diversified.

ARBITRAGE FUND | ARBITRAGE FUND | High Portfolio Turnover Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

High Portfolio Turnover Risk: The Fund normally expects to engage in active and frequent trading and expects to have a high portfolio turnover rate (over 100%). This may increase the Fund’s brokerage commission costs, which would reduce performance. Rapid portfolio turnover also exposes shareholders to a higher current realization of short-term gains, which could cause you to pay higher taxes.

ARBITRAGE FUND | ARBITRAGE FUND | Foreign Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Foreign Securities Risk: The securities of foreign issuers may be less liquid and more volatile than securities of comparable U.S. issuers. Transaction costs may be higher in foreign countries than in the U.S. The U.S. dollar value of foreign securities traded in foreign currencies held by the Fund or by funds in which the Fund invests (and any dividends and interest earned) may be affected favorably or unfavorably by changes in foreign currency exchange rates. An increase in the U.S. dollar relative to these other currencies may adversely affect the Fund. Additionally, investments in foreign securities, even those publicly traded in the U.S., may involve risks which are in addition to those inherent in U.S. investments. Foreign governments and economies often are less stable than the U.S. Government and the U.S. economy, and foreign companies may not be subject to the same regulatory requirements and accounting, auditing, and financial reporting standards of U.S. companies. As a consequence, there may be less publicly available information about such companies, which may negatively affect the value of foreign securities held by the Fund.

ARBITRAGE FUND | ARBITRAGE FUND | Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Market Risk: The value of the Fund’s investments, and the net asset value (“NAV”) of the Fund, will fluctuate over time, sometimes rapidly and unpredictably. Market risk may affect a single issuer, an entire industry, or the market as a whole. Securities markets may experience short-term or even extended periods of heightened volatility and turmoil. These events could have an adverse effect on the value of the Fund’s investments, and investors could lose money due to this price fluctuation. The value of a security may decline due to factors that are specifically related to a particular company, as well as general market conditions, such as real or perceived adverse economic or political conditions, inflation rates, changes in interest rates, or adverse investor sentiment. Geopolitical and other risks, including terrorism, war and sanctions, and environmental and public health risks (such as natural disasters, epidemics, and pandemics), may add to instability in world economies and markets generally. This uncertainty could lead to corporate events such as mergers, acquisitions, and restructurings breaking, forcing the Fund to allocate assets to other strategies. The extent and duration of such market disruptions cannot be predicted but could magnify the impact of other risks to the Fund, could have a significant adverse impact on the Fund and its investments, and could result in increased volatility of the Fund’s NAV.

ARBITRAGE FUND | ARBITRAGE FUND | Sector Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Sector Risk: The securities of companies in the same or related businesses (“sectors”), if comprising a significant portion of the Fund’s portfolio, may in some circumstances react negatively to market conditions, interest rates and economic, regulatory or financial developments, and may adversely affect the value of the Fund’s portfolio, to a greater extent than if such securities comprised a lesser portion of the Fund’s portfolio or if the Fund’s portfolio was diversified across a greater number of sectors. Some sectors have particular risks that may not affect other sectors.

ARBITRAGE FUND | ARBITRAGE FUND | Derivatives Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Derivatives Risk: In general, a derivative instrument typically involves leverage and provides exposure to potential gain or loss from a change in the market price of the underlying asset (or a basket of assets or an index) in a notional amount that exceeds the amount of cash or assets required to establish or maintain the derivative instrument. Adverse changes in the value or price of the underlying asset (or basket of assets or index), which the Fund may not directly own, can result in a loss to the Fund substantially greater than the amount invested in the derivative itself. The use of derivative instruments also exposes the Fund to additional risks and transaction costs. Derivative instruments come in many varieties and may include forward contracts, options (both written and purchased), and swap contracts.

ARBITRAGE FUND | ARBITRAGE FUND | Hedging Transaction Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Hedging Transaction Risk: Instruments used to hedge against an opposite position may offset losses, but they also may offset gains. The success of the Fund’s hedging strategies will be subject to the Adviser’s ability to assess correctly the degree of correlation between the performance of the instruments used in the hedging strategies and the performance of the investments in the Fund’s portfolio being hedged. Hedging transactions involve the risk of imperfect correlation. Imperfect correlation may prevent the Fund from achieving the intended hedge or expose the Fund to risk of loss. Hedging transactions also limit the opportunity for gain if the value of a hedged portfolio position should increase.

ARBITRAGE FUND | ARBITRAGE FUND | Counterparty Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Counterparty Risk: The Fund may enter into various types of derivative contracts with a counterparty that may be privately negotiated in the over-the-counter market. These contracts involve exposure to credit risk, because contract performance depends, in part, on the financial condition of the counterparty. If the creditworthiness of the counterparty declines, the Fund may not receive payments owed under the contract, or such payments may be delayed, and the value of agreements with the counterparty can be expected to decline, potentially resulting in losses to the Fund.

ARBITRAGE FUND | ARBITRAGE FUND | Temporary Investment/Cash Management Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Temporary Investment/Cash Management Risk: The Fund may hold a significant portion of its assets in cash, money market or similar cash management funds, or short-term investments for temporary defensive purposes in response to adverse market, economic, political or other conditions, to preserve the Fund’s ability to capitalize quickly on new market opportunities or for other reasons, such as because the Adviser has determined to obtain investment exposure through derivative instruments instead of direct cash investments. These investments may include money market funds, money market instruments such as Treasury bills, securities issued by the U.S. Government, its agencies or instrumentalities, bankers’ acceptances, commercial paper, and repurchase agreements for the above securities, and investment companies that invest primarily in such instruments. To the extent the Fund

maintains cash or holds short-term investments, the Fund may not achieve its investment objective and may also be subject to additional risks, including market, interest rate, and credit risk.

ARBITRAGE FUND | ARBITRAGE FUND | Swap Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Swap Risk: The Fund may enter into total return swaps to gain investment exposure to the underlying security or securities in a more efficient or economically attractive manner than direct ownership. In a standard “swap” transaction, two parties agree to exchange the returns (or differentials in rates of return) earned or realized on particular predetermined investments or instruments. Certain categories of swap agreements often have terms of greater than seven days and may be considered illiquid. Moreover, the Fund bears the risk of loss of the amount expected to be received under a swap agreement in the event of the default or bankruptcy of a swap agreement counterparty. It is possible that developments in the swaps market, including new and additional government regulation, could result in higher Fund costs and expenses and could adversely affect the Fund’s ability, among other things, to terminate existing swap agreements or to realize amounts to be received under such agreements.

ARBITRAGE FUND | ARBITRAGE FUND | Options Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Options Risk: Options transactions involve special risks that may make it difficult or impossible to close a position when the Fund desires. These risks include possible imperfect correlation between the price movements of the option and the underlying security; the potential lack of a liquid secondary market at any particular time; and possible price fluctuation limits. In addition, the option activities of the Fund may affect its portfolio turnover rate and the amount of brokerage commissions paid by the Fund.

ARBITRAGE FUND | ARBITRAGE FUND | Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Liquidity Risk: Liquidity risk exists when particular investments are difficult to purchase or sell. Liquidity risk may be the result of, among other things, market turmoil, the reduced number and capacity of traditional market participants to make a market in fixed-income securities, or the lack of an active trading market. Markets for securities or financial instruments could be disrupted by a number of events, including, but not limited to, an economic crisis, natural disasters, new legislation or regulatory changes inside or outside the U.S. Liquid investments may become less liquid after being purchased by the Fund, particularly during periods of market stress. To enhance investment value and/or protect shareholder rights, from time to time, the Fund may participate in various types of litigation, including but not limited to shareholder appraisal rights petitions and class action lawsuits. If the Fund exercises its appraisal rights, it may experience limited liquidity on its investment while the subject securities are being appraised. Illiquid and relatively less liquid investments may be harder to value, especially in turbulent markets, and if the Fund is forced to sell these investments to meet redemption requests or for other cash needs, the Fund may suffer a loss.

ARBITRAGE FUND | ARBITRAGE FUND | Investment Company and ETF Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Investment Company and ETF Risk: Investing in securities issued by other investment companies, including ETFs, involves risks similar to those of investing directly in the securities and other assets held by the investment company or ETF. The Fund will indirectly bear its pro rata share of the fees and expenses incurred by a fund it invests in, including advisory fees. These expenses are in addition to the advisory and other expenses that the Fund bears directly in connection with its own operations. Unlike shares of typical mutual funds, shares of ETFs are traded on an exchange through a trading day and bought and sold based on market values and not at NAV. For this reason, shares could trade either at a premium or a discount to NAV. The trading price of an ETF is expected to closely track the actual NAV of an ETF, and the Fund will generally gain or lose value consistent with the performance of the ETF’s portfolio securities. The Fund will pay brokerage commissions in connection with the purchase and sale of shares of ETFs. An index-based ETF may not replicate exactly the performance of the benchmark index it seeks to track for a number of reasons, including transaction costs incurred by the ETF, the temporary unavailability of certain index securities in the secondary market or discrepancies between the ETF and the index with respect to the weighting of securities or the number of securities held.

ARBITRAGE FUND | ARBITRAGE FUND | Leverage Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Leverage Risk: If the Fund uses leverage through activities such as borrowing, entering into short sales, purchasing securities on margin or on a “when-issued” basis or purchasing derivative instruments in an effort to increase its returns, the Fund has the risk of magnified capital losses that occur when losses affect an asset base, enlarged by borrowings or the creation of liabilities, that exceeds the net assets of the Fund. Should the Fund employ leverage, the Fund’s NAV may be more volatile and sensitive to market movements. Leverage may involve the creation of a liability that requires the Fund to pay interest.

ARBITRAGE FUND | ARBITRAGE FUND | Market Capitalization Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Market Capitalization Risk: The securities of small-capitalization and mid-capitalization companies may be less liquid and more vulnerable to adverse business, economic, or market events than securities of relatively larger, more established companies. Larger, more established companies may be unable to attain the high growth rates of successful, smaller- and medium-sized companies during periods of economic expansion.

ARBITRAGE FUND | ARBITRAGE FUND | Currency Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Currency Risk: Fluctuations in exchange rates between the U.S. dollar and foreign currencies may negatively affect an investment in the Fund. Adverse changes in exchange rates may erode or reverse any gains produced by foreign currency denominated investments and may widen any losses. The Fund may, but is not required to, seek to reduce currency risk by hedging part or all of its exposure to various foreign currencies. The return of currency forward and futures contracts utilized for currency hedging may not perfectly offset the actual fluctuations of the foreign currencies relative to the U.S. dollar and may prevent the Fund from realizing gains from an increase in the value of the currency. In addition to currency risk, currency forward/futures contracts, like other derivatives, may be susceptible to credit risk and other risks. Further, in order to minimize transaction costs, or for other reasons, the Fund’s exposure to non-U.S. currencies may not be hedged.

WATER ISLAND EVENT-DRIVEN FUND | WATER ISLAND EVENT-DRIVEN FUND | Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] As with all mutual funds, investing in the Fund entails risks that could cause the Fund and you to lose money.
WATER ISLAND EVENT-DRIVEN FUND | WATER ISLAND EVENT-DRIVEN FUND | Merger Arbitrage Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Merger Arbitrage Risk: The principal risk associated with the Fund’s merger arbitrage investment strategy is that the proposed corporate reorganizations in which the Fund invests may not be completed or may be completed on less favorable terms than originally anticipated, in which case the Fund may realize losses.

WATER ISLAND EVENT-DRIVEN FUND | WATER ISLAND EVENT-DRIVEN FUND | Short Sale Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Short Sale Risk: The Fund may obtain short exposure by borrowing a security to sell or by trading a derivative instrument that has a similar economic effect, such as a future, forward or swap. The Fund will suffer a loss if it sells a security short and the value of the security rises rather than falls. There is no theoretical ceiling to the price of a shorted security. Therefore, in theory, securities sold short have unlimited risk. Short sales also 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. The Fund’s investment performance may also suffer if it is required to close out a short position earlier than it had intended. In addition, the Fund may be subject to expenses related to short sales that are not typically associated with investing in securities directly, such as costs of borrowing. These expenses may negatively impact the Fund’s performance. When the Fund sells a security short, it must maintain cash or high-grade securities equal to the margin requirement. As a result, the Fund may maintain high levels of cash or other liquid assets (such as U.S. Treasury bills, money market instruments, certificates of deposit, high quality commercial paper, and long equity positions). The need to maintain cash or other liquid assets could limit the Fund’s ability to pursue other opportunities as they arise. Short exposure generally introduces more risk to the Fund than long positions (purchases). It is also possible that the Fund’s long positions will decline in value at the same time that the value of its short positions increases, thereby increasing potential losses to the Fund.

WATER ISLAND EVENT-DRIVEN FUND | WATER ISLAND EVENT-DRIVEN FUND | Event-Driven Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Event-Driven Risk: Event-driven investments involve the risk that certain of the events driving the investment may not happen or the market may react differently than expected to the anticipated transaction. In addition, although an event may occur or is announced, it may be renegotiated, terminated, or involve a longer time frame than originally contemplated. Event-driven investment transactions are also subject to the risk of overall market movements. Any one of these risks could cause the Fund to experience investment losses, impacting its shares negatively.

WATER ISLAND EVENT-DRIVEN FUND | WATER ISLAND EVENT-DRIVEN FUND | Special Situations Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Special Situations Risk: The Fund may seek to benefit from “special situations,” such as mergers, acquisitions, consolidations, bankruptcies, liquidations, reorganizations, restructurings, tender or exchange offers, or other unusual events expected to affect a particular issuer. Investing in special situations carries the risk that certain of such situations may not happen as anticipated or the market may react differently than expected to such situations. The securities of companies involved in special situations may be more volatile than other securities, may at times be illiquid, or may be difficult to value. Certain special situations carry the additional risks inherent in difficult corporate transitions and the securities of such companies may be more likely to lose value than the securities of more stable companies.

WATER ISLAND EVENT-DRIVEN FUND | WATER ISLAND EVENT-DRIVEN FUND | Active Management Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Active Management Risk: The Fund is an actively managed investment portfolio and is therefore subject to management risk. The Adviser will apply its investment and risk analysis in making investment decisions for the Fund, but there is no guarantee that these decisions will produce the intended results.

WATER ISLAND EVENT-DRIVEN FUND | WATER ISLAND EVENT-DRIVEN FUND | Concentration Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Concentration Risk: If a large percentage of mergers or other corporate events taking place within the U.S. are within one industry over a given period of time, the Fund may invest a large portion of its assets in securities of issuers in a single industry for that period of time. During such a period of concentration, the Fund may be subject to greater volatility with respect to its portfolio securities than a fund that is more broadly diversified.

WATER ISLAND EVENT-DRIVEN FUND | WATER ISLAND EVENT-DRIVEN FUND | High Portfolio Turnover Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

High Portfolio Turnover Risk: The Fund normally expects to engage in active and frequent trading and expects to have a high portfolio turnover rate (over 100%). This may increase the Fund’s brokerage commission costs, which would reduce performance. Rapid portfolio turnover also exposes shareholders to a higher current realization of short-term gains, which could cause you to pay higher taxes.

WATER ISLAND EVENT-DRIVEN FUND | WATER ISLAND EVENT-DRIVEN FUND | Interest Rate Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Interest Rate Risk: Prices of debt securities and preferred stocks tend to move inversely with changes in interest rates. When interest rates fall, the market value of the respective debt securities and preferred securities usually increases. Conversely, when interest rates rise, the market value of the respective debt securities and preferred securities usually declines. As such, a change in interest rates may affect prices of the Fund’s debt securities and preferred securities and, accordingly, the Fund’s share price.

WATER ISLAND EVENT-DRIVEN FUND | WATER ISLAND EVENT-DRIVEN FUND | Foreign Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Foreign Securities Risk: The securities of foreign issuers may be less liquid and more volatile than securities of comparable U.S. issuers. Transaction costs may be higher in foreign countries than in the U.S. The U.S. dollar value of foreign securities traded in foreign currencies held by the Fund or by funds in which the Fund invests (and any dividends and interest earned) may be affected favorably or unfavorably by changes in foreign currency exchange rates. An increase in the U.S. dollar relative to these other currencies may adversely affect the Fund. Additionally, investments in foreign securities, even those publicly traded in the U.S., may involve risks which are in addition to those inherent in U.S. investments. Foreign governments and economies often are less stable than the U.S. Government and the U.S. economy, and foreign companies may not be subject to the same regulatory requirements and accounting, auditing, and financial reporting standards of U.S. companies. As a consequence, there may be less publicly available information about such companies, which may negatively affect the value of foreign securities held by the Fund.

WATER ISLAND EVENT-DRIVEN FUND | WATER ISLAND EVENT-DRIVEN FUND | Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Market Risk: The value of the Fund’s investments, and the net asset value (“NAV”) of the Fund, will fluctuate over time, sometimes rapidly and unpredictably. Market risk may affect a single issuer, an entire industry, or the market as a whole. Securities markets may experience short-term or even extended periods of heightened volatility and turmoil. These events could have an adverse effect on the value of the Fund’s investments, and investors could lose money due to this price fluctuation. The value of a security may decline due to factors that are specifically related to a particular company, as well as general market conditions, such as real or perceived adverse economic or political conditions, inflation rates, changes in interest rates, or adverse investor sentiment. Geopolitical and other risks, including terrorism, war and sanctions, and environmental and public health risks (such as natural disasters, epidemics, and pandemics), may add to instability in world economies and markets generally. This uncertainty could lead to corporate events such as mergers, acquisitions, and restructurings breaking, forcing the Fund to allocate assets to other strategies. The extent and duration of such market disruptions cannot be predicted but could magnify the impact of other risks to the Fund, could have a significant adverse impact on the Fund and its investments, and could result in increased volatility of the Fund’s NAV.

WATER ISLAND EVENT-DRIVEN FUND | WATER ISLAND EVENT-DRIVEN FUND | Sector Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Sector Risk: The securities of companies in the same or related businesses (“sectors”), if comprising a significant portion of the Fund’s portfolio, may in some circumstances react negatively to market conditions, interest rates and economic, regulatory or financial developments, and may adversely affect the value of the Fund’s portfolio, to a greater extent than if such securities comprised a lesser portion of the Fund’s portfolio or if the Fund’s portfolio was diversified across a greater number of sectors. Some sectors have particular risks that may not affect other sectors.

WATER ISLAND EVENT-DRIVEN FUND | WATER ISLAND EVENT-DRIVEN FUND | Derivatives Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Derivatives Risk: In general, a derivative instrument typically involves leverage and provides exposure to potential gain or loss from a change in the market price of the underlying asset (or a basket of assets or an index) in a notional amount that exceeds the amount of cash or assets required to establish or maintain the derivative instrument. Adverse changes in the value or price of the underlying asset (or basket of assets or index), which the Fund may not directly own, can result in a loss to the Fund substantially greater than the amount invested in the derivative itself. The use of derivative instruments also exposes the Fund to additional risks and transaction costs. Derivative instruments come in many varieties and may include forward contracts, options (both written and purchased), and swap contracts.

WATER ISLAND EVENT-DRIVEN FUND | WATER ISLAND EVENT-DRIVEN FUND | Credit Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Credit Risk: Credit risk refers to the possibility that the issuer of the security will not be able to make interest or principal payments when due. The Fund may invest in convertible and non-convertible debt securities, including high yield debt securities, also known as “junk bonds.” Investments in junk bonds are subject to greater credit risks than securities with credit ratings above investment grade and have a greater risk of default than investment grade debt securities. Junk bonds are less sensitive to interest rate changes than higher credit quality instruments and generally are more sensitive to adverse economic changes or individual corporate developments.

WATER ISLAND EVENT-DRIVEN FUND | WATER ISLAND EVENT-DRIVEN FUND | Convertible Security Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Convertible Security Risk: Convertible securities generally offer lower interest or dividend yields than non-convertible securities of similar quality. Because convertible securities are higher in the firm’s capital structure than equity, convertible securities are generally not as risky as the equity securities of the same issuer. However, convertible securities may gain or lose value due to changes in interest rates and other general economic conditions, industry fundamentals, market sentiment, and changes in the issuer’s operating results and credit ratings.

WATER ISLAND EVENT-DRIVEN FUND | WATER ISLAND EVENT-DRIVEN FUND | Hedging Transaction Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Hedging Transaction Risk: Instruments used to hedge against an opposite position may offset losses, but they also may offset gains. The success of the Fund’s hedging strategies will be subject to the Adviser’s ability to assess correctly the degree of correlation between the performance of the instruments used in the hedging strategies and the performance of the investments in the Fund’s portfolio being hedged. Hedging transactions involve the risk of imperfect correlation. Imperfect correlation may prevent the Fund from achieving the intended hedge or expose the Fund to risk of loss. Hedging transactions also limit the opportunity for gain if the value of a hedged portfolio position should increase.

WATER ISLAND EVENT-DRIVEN FUND | WATER ISLAND EVENT-DRIVEN FUND | Counterparty Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Counterparty Risk: The Fund may enter into various types of derivative contracts with a counterparty that may be privately negotiated in the over-the-counter market. These contracts involve exposure to credit risk, because contract performance depends, in part, on the financial condition of the counterparty. If the creditworthiness of the counterparty declines, the Fund may not receive payments owed under the contract, or such payments may be delayed, and the value of agreements with the counterparty can be expected to decline, potentially resulting in losses to the Fund.

WATER ISLAND EVENT-DRIVEN FUND | WATER ISLAND EVENT-DRIVEN FUND | Temporary Investment/Cash Management Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Temporary Investment/Cash Management Risk: The Fund may hold a significant portion of its assets in cash, money market or similar cash management funds, or short-term investments for temporary defensive purposes in response to adverse market, economic, political or other conditions, to preserve the Fund’s ability to capitalize quickly on new market opportunities or for other reasons, such as because the Adviser has determined to obtain investment exposure through derivative instruments instead of direct cash investments. These investments may include money market funds, money market instruments such as Treasury bills, securities issued by the U.S. Government, its agencies or instrumentalities, bankers’ acceptances, commercial paper, and repurchase agreements for the above securities, and investment companies that invest primarily in such instruments. To the extent the Fund maintains cash or holds short-term investments, the Fund may not achieve its investment objective and may also be subject to additional risks, including market, interest rate, and credit risk.

WATER ISLAND EVENT-DRIVEN FUND | WATER ISLAND EVENT-DRIVEN FUND | Swap Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Swap Risk: The Fund may enter into total return swaps to gain investment exposure to the underlying security or securities in a more efficient or economically attractive manner than direct ownership. In a standard “swap” transaction, two parties agree to exchange the returns (or differentials in rates of return) earned or realized on particular predetermined investments or instruments. The Fund may also enter into credit default or credit default index swaps with qualified broker-dealer counterparties. In a credit default swap, one party typically makes an upfront payment and a stream of payments to another party in exchange for the right to receive a specified return in the event of a default by a referenced entity on its obligation or other credit-related event. The Fund may use swaps for any investment purpose, including as part of a merger arbitrage or event-driven strategy involving pending corporate reorganizations. Certain categories of swap agreements often have terms of greater than seven days and may be considered illiquid. Moreover, the Fund bears the risk of loss of the amount expected to be received under a swap agreement in the event of the default or bankruptcy of a swap agreement counterparty. It is possible that developments in the swaps market, including new and additional government regulation, could result in higher Fund costs and expenses and could adversely affect the Fund’s ability, among other things, to terminate existing swap agreements or to realize amounts to be received under such agreements.

WATER ISLAND EVENT-DRIVEN FUND | WATER ISLAND EVENT-DRIVEN FUND | Options Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Options Risk: Options transactions involve special risks that may make it difficult or impossible to close a position when the Fund desires. These risks include possible imperfect correlation between the price movements of the option and the underlying security; the potential lack of a liquid secondary market at any particular time; and possible price fluctuation limits. In addition, the option activities of the Fund may affect its portfolio turnover rate and the amount of brokerage commissions paid by the Fund.

WATER ISLAND EVENT-DRIVEN FUND | WATER ISLAND EVENT-DRIVEN FUND | Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Liquidity Risk: Liquidity risk exists when particular investments are difficult to purchase or sell. Liquidity risk may be the result of, among other things, market turmoil, the reduced number and capacity of traditional market participants to make a market in fixed-income securities, or the lack of an active trading market. Markets for securities or financial instruments could be disrupted by a number of events, including, but not limited to, an economic crisis, natural disasters, new legislation or regulatory changes inside or outside the U.S. Liquid investments may become less liquid after being purchased by the Fund, particularly during periods of market stress. To enhance investment value and/or protect shareholder rights, from time to time, the Fund may participate in various types of litigation, including but not limited to shareholder appraisal rights petitions and class action lawsuits. If the Fund exercises its appraisal rights, it may experience limited liquidity on its investment while the subject securities are being appraised. Illiquid and relatively less liquid investments may be harder to value, especially in turbulent markets, and if the Fund is forced to sell these investments to meet redemption requests or for other cash needs, the Fund may suffer a loss.

WATER ISLAND EVENT-DRIVEN FUND | WATER ISLAND EVENT-DRIVEN FUND | Investment Company and ETF Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Investment Company and ETF Risk: Investing in securities issued by other investment companies, including ETFs, involves risks similar to those of investing directly in the securities and other assets held by the investment company or ETF. The Fund will indirectly bear its pro rata share of the fees and expenses incurred by a fund it invests in, including advisory fees. These expenses are in addition to the advisory and other expenses that the Fund bears directly in connection with its own operations. Unlike shares of typical mutual funds, shares of ETFs are traded on an exchange through a trading day and bought and sold based on market values and not at NAV. For this reason, shares could trade either at a premium or a discount to NAV. The trading price of an ETF is expected to closely track the actual NAV of an ETF, and the Fund will generally gain or lose value consistent with the performance of the ETF’s portfolio securities. The Fund will pay brokerage commissions in connection with the purchase and sale of shares of ETFs. An index-based ETF may not replicate exactly the performance of the benchmark index it seeks to track for a number of reasons, including transaction costs incurred by the ETF, the temporary unavailability of certain index securities in the secondary market or discrepancies between the ETF and the index with respect to the weighting of securities or the number of securities held.

WATER ISLAND EVENT-DRIVEN FUND | WATER ISLAND EVENT-DRIVEN FUND | Large Shareholder Transaction Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Large Shareholder Transaction Risk: A significant percentage of the Fund’s shares may be owned or controlled by certain large shareholders, including another Fund advised by the Adviser. The Fund may experience adverse effects when certain large shareholders purchase or redeem large amounts of shares of the Fund. Such large shareholder redemptions may cause the Fund to sell its securities at times when it would not otherwise do so, which may negatively impact the Fund’s NAV and liquidity. In addition, a large redemption could result in the Fund’s current expenses being allocated over a smaller asset base, leading to an increase in the Fund’s expense ratio. Similarly, large share purchases may adversely affect the Fund’s performance to the extent that the Fund is delayed in investing new cash and is required to maintain a larger cash position than it ordinarily would.

WATER ISLAND EVENT-DRIVEN FUND | WATER ISLAND EVENT-DRIVEN FUND | Leverage Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Leverage Risk: If the Fund uses leverage through activities such as borrowing, entering into short sales, purchasing securities on margin or on a “when-issued” basis or purchasing derivative instruments in an effort to increase its returns, the Fund has the risk of magnified capital losses that occur when losses affect an asset base, enlarged by borrowings or the creation of liabilities, that exceeds the net assets of the Fund. Should the Fund employ leverage, the Fund’s NAV may be more volatile and sensitive to market movements. Leverage may involve the creation of a liability that requires the Fund to pay interest.

WATER ISLAND EVENT-DRIVEN FUND | WATER ISLAND EVENT-DRIVEN FUND | Market Capitalization Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Market Capitalization Risk: The securities of small-capitalization and mid-capitalization companies may be less liquid and more vulnerable to adverse business, economic, or market events than securities of relatively larger, more established companies. Larger, more established companies may be unable to attain the high growth rates of successful, smaller- and medium-sized companies during periods of economic expansion.

WATER ISLAND EVENT-DRIVEN FUND | WATER ISLAND EVENT-DRIVEN FUND | Currency Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Currency Risk: Fluctuations in exchange rates between the U.S. dollar and foreign currencies may negatively affect an investment in the Fund. Adverse changes in exchange rates may erode or reverse any gains produced by foreign currency denominated investments and may widen any losses. The Fund may, but is not required to, seek to reduce currency risk by hedging part or all of its exposure to various foreign currencies. The return of currency forward and futures contracts utilized for currency hedging may not perfectly offset the actual fluctuations of the foreign currencies relative to the U.S. dollar and may prevent the Fund from realizing gains from an increase in the value of the currency. In addition to currency risk, currency forward/futures contracts, like other derivatives, may be susceptible to credit risk and other risks. Further, in order to minimize transaction costs, or for other reasons, the Fund’s exposure to non-U.S. currencies may not be hedged.

WATER ISLAND CREDIT OPPORTUNITIES FUND | WATER ISLAND CREDIT OPPORTUNITIES FUND | Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] As with all mutual funds, investing in the Fund entails risks that could cause the Fund and you to lose money.
WATER ISLAND CREDIT OPPORTUNITIES FUND | WATER ISLAND CREDIT OPPORTUNITIES FUND | Merger Arbitrage Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Merger Arbitrage Risk: The principal risk associated with the Fund’s merger arbitrage investment strategy is that the proposed corporate reorganizations in which the Fund invests may not be completed or may be completed on less favorable terms than originally anticipated, in which case the Fund may realize losses.

WATER ISLAND CREDIT OPPORTUNITIES FUND | WATER ISLAND CREDIT OPPORTUNITIES FUND | Short Sale Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Short Sale Risk: The Fund may obtain short exposure by borrowing a security to sell or by trading a derivative instrument that has a similar economic effect, such as a future, forward or swap. The Fund will suffer a loss if it sells a security short and the value of the security rises rather than falls. There is no theoretical ceiling to the price of a shorted security. Therefore, in theory, securities sold short have unlimited risk. Short sales also 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. The Fund’s investment performance may also suffer if it is required to close out a short position earlier

than it had intended. In addition, the Fund may be subject to expenses related to short sales that are not typically associated with investing in securities directly, such as costs of borrowing. These expenses may negatively impact the Fund’s performance. When the Fund sells a security short, it must maintain cash or high-grade securities equal to the margin requirement. As a result, the Fund may maintain high levels of cash or other liquid assets (such as U.S. Treasury bills, money market instruments, certificates of deposit, high quality commercial paper, and long equity positions). The need to maintain cash or other liquid assets could limit the Fund’s ability to pursue other opportunities as they arise. Short exposure generally introduces more risk to the Fund than long positions (purchases). It is also possible that the Fund’s long positions will decline in value at the same time that the value of its short positions increases, thereby increasing potential losses to the Fund.

WATER ISLAND CREDIT OPPORTUNITIES FUND | WATER ISLAND CREDIT OPPORTUNITIES FUND | Event-Driven Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Event-Driven Risk: Event-driven investments involve the risk that certain of the events driving the investment may not happen or the market may react differently than expected to the anticipated transaction. In addition, although an event may occur or is announced, it may be renegotiated, terminated, or involve a longer time frame than originally contemplated. Event-driven investment transactions are also subject to the risk of overall market movements. Any one of these risks could cause the Fund to experience investment losses, impacting its shares negatively.

WATER ISLAND CREDIT OPPORTUNITIES FUND | WATER ISLAND CREDIT OPPORTUNITIES FUND | Active Management Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Active Management Risk: The Fund is an actively managed investment portfolio and is therefore subject to management risk. The Adviser will apply its investment and risk analysis in making investment decisions for the Fund, but there is no guarantee that these decisions will produce the intended results.

WATER ISLAND CREDIT OPPORTUNITIES FUND | WATER ISLAND CREDIT OPPORTUNITIES FUND | High Portfolio Turnover Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

High Portfolio Turnover Risk: The Fund normally expects to engage in active and frequent trading and expects to have a high portfolio turnover rate (over 100%). This may increase the Fund’s brokerage commission costs, which would reduce performance. Rapid portfolio turnover also exposes shareholders to a higher current realization of short-term gains, which could cause you to pay higher taxes.

WATER ISLAND CREDIT OPPORTUNITIES FUND | WATER ISLAND CREDIT OPPORTUNITIES FUND | Interest Rate Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Interest Rate Risk: Prices of debt securities and preferred stocks tend to move inversely with changes in interest rates. When interest rates fall, the market value of the respective debt securities and preferred securities usually increases. Conversely, when interest rates rise, the market value of the respective debt securities and preferred securities usually declines. As such, a change in interest rates may affect prices of the Fund’s debt securities and preferred securities and, accordingly, the Fund’s share price.

WATER ISLAND CREDIT OPPORTUNITIES FUND | WATER ISLAND CREDIT OPPORTUNITIES FUND | Foreign Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Foreign Securities Risk: The securities of foreign issuers may be less liquid and more volatile than securities of comparable U.S. issuers. Transaction costs may be higher in foreign countries than in the U.S. The U.S. dollar value of foreign securities traded in foreign currencies held by the Fund or by funds in which the Fund invests (and any dividends and interest earned) may be affected favorably or unfavorably by changes in foreign currency exchange rates. An increase in the U.S. dollar relative to these other currencies may adversely affect the Fund. Additionally, investments in foreign securities, even those publicly traded in the U.S., may involve risks which are in addition to those inherent in U.S. investments. Foreign governments and economies often are less stable than the U.S. Government and the U.S. economy, and foreign companies may not be subject to the same regulatory requirements and accounting, auditing, and financial reporting standards of U.S. companies. As a consequence, there may be less publicly available information about such companies, which may negatively affect the value of foreign securities held by the Fund.

WATER ISLAND CREDIT OPPORTUNITIES FUND | WATER ISLAND CREDIT OPPORTUNITIES FUND | Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Market Risk: The value of the Fund’s investments, and the net asset value (“NAV”) of the Fund, will fluctuate over time, sometimes rapidly and unpredictably. Market risk may affect a single issuer, an entire industry, or the market as a whole. Securities markets may experience short-term or even extended periods of heightened volatility and turmoil. These events could have an adverse effect on the value of the Fund’s investments, and investors could lose money due to this price fluctuation. The value of a security may decline due to factors that are specifically related to a particular company, as well as general market conditions, such as real or perceived adverse economic or political conditions, inflation rates, changes in interest rates, or adverse investor sentiment. Geopolitical and other risks, including terrorism, war and sanctions, and environmental and public health risks (such as natural disasters, epidemics, and pandemics), may add to instability in world economies and markets generally. This uncertainty could lead to corporate events such as mergers, acquisitions, and restructurings breaking, forcing the Fund to allocate assets to other strategies. The extent and duration of such market disruptions cannot be predicted but could magnify the impact of other risks to the Fund, could have a significant adverse impact on the Fund and its investments, and could result in increased volatility of the Fund’s NAV.

WATER ISLAND CREDIT OPPORTUNITIES FUND | WATER ISLAND CREDIT OPPORTUNITIES FUND | Sector Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Sector Risk: The securities of companies in the same or related businesses (“sectors”), if comprising a significant portion of the Fund’s portfolio, may in some circumstances react negatively to market conditions, interest rates and economic, regulatory or financial developments, and may adversely affect the value of the Fund’s portfolio, to a greater extent than if such securities comprised a lesser portion of the Fund’s portfolio or if the Fund’s portfolio was diversified across a greater number of sectors. Some sectors have particular risks that may not affect other sectors.

WATER ISLAND CREDIT OPPORTUNITIES FUND | WATER ISLAND CREDIT OPPORTUNITIES FUND | Derivatives Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Derivatives Risk: In general, a derivative instrument typically involves leverage and provides exposure to potential gain or loss from a change in the market price of the underlying asset (or a basket of assets or an index) in a notional amount that exceeds the amount of cash or assets required to establish or maintain the derivative instrument. Adverse changes in the value or price of the underlying asset (or basket of assets or index), which the Fund may not directly own, can result in a loss to the Fund substantially greater than the amount invested in the derivative itself. The use of derivative instruments also exposes the Fund to additional risks and transaction costs. Derivative instruments come in many varieties and may include forward contracts, options (both written and purchased), and swap contracts.

WATER ISLAND CREDIT OPPORTUNITIES FUND | WATER ISLAND CREDIT OPPORTUNITIES FUND | Credit Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Credit Risk: Credit risk refers to the possibility that the issuer of the security will not be able to make interest or principal payments when due. The Fund may invest in convertible and non-convertible debt securities, including high yield debt securities, also known as “junk bonds.” Investments in junk bonds are subject to greater credit risks than securities with credit ratings above investment grade and have a greater risk of default than investment grade debt securities. Junk bonds are less sensitive to interest rate changes than higher credit quality instruments and generally are more sensitive to adverse economic changes or individual corporate developments.

WATER ISLAND CREDIT OPPORTUNITIES FUND | WATER ISLAND CREDIT OPPORTUNITIES FUND | Convertible Security Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Convertible Security Risk: Convertible securities generally offer lower interest or dividend yields than non-convertible securities of similar quality. Because convertible securities are higher in the firm’s capital structure than equity, convertible securities are generally not as risky as the equity securities of the same issuer. However, convertible securities may gain or lose value due to changes in interest rates and other general economic conditions, industry fundamentals, market sentiment and changes in the issuer’s operating results and credit ratings.

WATER ISLAND CREDIT OPPORTUNITIES FUND | WATER ISLAND CREDIT OPPORTUNITIES FUND | Hedging Transaction Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Hedging Transaction Risk: Instruments used to hedge against an opposite position may offset losses, but they also may offset gains. The success of the Fund’s hedging strategies will be subject to the Adviser’s ability to assess correctly the degree of correlation between the performance of the instruments used in the hedging strategies and the performance of the investments in the Fund’s portfolio being hedged. Hedging transactions involve the risk of imperfect correlation. Imperfect correlation may prevent the Fund from achieving the intended hedge or expose the Fund to risk of loss. Hedging transactions also limit the opportunity for gain if the value of a hedged portfolio position should increase.

WATER ISLAND CREDIT OPPORTUNITIES FUND | WATER ISLAND CREDIT OPPORTUNITIES FUND | Counterparty Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Counterparty Risk: The Fund may enter into various types of derivative contracts with a counterparty that may be privately negotiated in the over-the-counter market. These contracts involve exposure to credit risk, because contract performance depends, in part, on the financial condition of the counterparty. If the creditworthiness of the counterparty declines, the Fund may not receive payments owed under the contract, or such payments may be delayed, and the value of agreements with the counterparty can be expected to decline, potentially resulting in losses to the Fund.

WATER ISLAND CREDIT OPPORTUNITIES FUND | WATER ISLAND CREDIT OPPORTUNITIES FUND | Temporary Investment/Cash Management Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Temporary Investment/Cash Management Risk: The Fund may hold a significant portion of its assets in cash, money market or similar cash management funds, or short-term investments for temporary defensive purposes in response to adverse market, economic, political or other conditions, to preserve the Fund’s ability to capitalize quickly on new market opportunities or for other reasons, such as because the Adviser has determined to obtain investment exposure through derivative instruments instead of direct cash investments. These investments may include money market funds, money market instruments such as Treasury bills, securities issued by the U.S. Government, its agencies or instrumentalities, bankers’ acceptances, commercial paper, and repurchase agreements for the above securities, and investment companies that invest primarily in such instruments. To the extent the Fund maintains cash or holds short-term investments, the Fund may not achieve its investment objective and may also be subject to additional risks, including market, interest rate, and credit risk.

WATER ISLAND CREDIT OPPORTUNITIES FUND | WATER ISLAND CREDIT OPPORTUNITIES FUND | Swap Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Swap Risk: The Fund may enter into total return swaps to gain investment exposure to the underlying security or securities in a more efficient or economically attractive manner than direct ownership. In a standard “swap” transaction, two parties agree to exchange the returns (or differentials in rates of return) earned or realized on particular predetermined investments or instruments. The Fund may also enter into credit default or credit default index swaps with qualified broker-dealer counterparties. In a credit default swap, one party typically makes an upfront payment and a stream of payments to another party in exchange for the right to receive a specified return in the event of a default by a referenced entity on its obligation or other credit-related event. The Fund may use swaps for any investment purpose, including as part of a merger arbitrage or event-driven strategy involving pending corporate reorganizations. Certain categories of swap agreements often have terms of greater than seven days and may be considered illiquid. Moreover, the Fund bears the risk of loss of the amount expected to be received under a swap agreement in the event of the default or bankruptcy of a swap agreement counterparty. It is possible that developments in the swaps market, including new and additional government regulation, could result in higher Fund costs and expenses and could adversely affect the Fund’s ability, among other things, to terminate existing swap agreements or to realize amounts to be received under such agreements.

WATER ISLAND CREDIT OPPORTUNITIES FUND | WATER ISLAND CREDIT OPPORTUNITIES FUND | Options Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Options Risk: Options transactions involve special risks that may make it difficult or impossible to close a position when the Fund desires. These risks include possible imperfect correlation between the price movements of the option and the underlying security; the potential lack of a liquid secondary

market at any particular time; and possible price fluctuation limits. In addition, the option activities of the Fund may affect its portfolio turnover rate and the amount of brokerage commissions paid by the Fund.

WATER ISLAND CREDIT OPPORTUNITIES FUND | WATER ISLAND CREDIT OPPORTUNITIES FUND | Preferred Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Preferred Securities Risk: Investments in preferred stocks may be subject to the risks of deferred distribution payments, subordination to debt instruments, a lack of liquidity compared to equities, limited voting rights, and sensitivity to interest-rate changes.

WATER ISLAND CREDIT OPPORTUNITIES FUND | WATER ISLAND CREDIT OPPORTUNITIES FUND | Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Liquidity Risk: Liquidity risk exists when particular investments are difficult to purchase or sell. Liquidity risk may be the result of, among other things, market turmoil, the reduced number and capacity of traditional market participants to make a market in fixed-income securities, or the lack of an active trading market. Markets for securities or financial instruments could be disrupted by a number of events, including, but not limited to, an economic crisis, natural disasters, new legislation or regulatory changes inside or outside the U.S. Liquid investments may become less liquid after being purchased by the Fund, particularly during periods of market stress. Illiquid and relatively less liquid investments may be harder to value, especially in turbulent markets, and if the Fund is forced to sell these investments to meet redemption requests or for other cash needs, the Fund may suffer a loss.

WATER ISLAND CREDIT OPPORTUNITIES FUND | WATER ISLAND CREDIT OPPORTUNITIES FUND | Investment Company and ETF Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Investment Company and ETF Risk: Investing in securities issued by other investment companies, including ETFs, involves risks similar to those of investing directly in the securities and other assets held by the investment company or ETF. The Fund will indirectly bear its pro rata share of the fees and expenses incurred by a fund it invests in, including advisory fees. These expenses are in addition to the advisory and other expenses that the Fund bears directly in connection with its own operations. Unlike shares of typical mutual funds, shares of ETFs are traded on an exchange through a trading day and bought and sold based on market values and not at NAV. For this reason, shares could trade either at a premium or a discount to NAV. The trading price of an ETF is expected to closely track the actual NAV of an ETF, and the Fund will generally gain or lose value consistent with the performance of the ETF’s portfolio securities. The Fund will pay brokerage commissions in connection with the purchase and sale of shares of ETFs. An index-based ETF may not replicate exactly the performance of the benchmark index it seeks to track for a number of reasons, including transaction costs incurred by the ETF, the temporary unavailability of certain index securities in the secondary market or discrepancies between the ETF and the index with respect to the weighting of securities or the number of securities held.

WATER ISLAND CREDIT OPPORTUNITIES FUND | WATER ISLAND CREDIT OPPORTUNITIES FUND | Large Shareholder Transaction Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Large Shareholder Transaction Risk: A significant percentage of the Fund’s shares may be owned or controlled by certain large shareholders. The Fund may experience adverse effects when certain large shareholders purchase or redeem large amounts of shares of the Fund. Such large shareholder redemptions may cause the Fund to sell its securities at times when it would not otherwise do so, which may negatively impact the Fund’s NAV and liquidity. In addition, a large redemption could result in the Fund’s current expenses being allocated over a smaller asset base, leading to an increase in the Fund’s expense ratio. Similarly, large share purchases may adversely affect the Fund’s performance to the extent that the Fund is delayed in investing new cash and is required to maintain a larger cash position than it ordinarily would.

WATER ISLAND CREDIT OPPORTUNITIES FUND | WATER ISLAND CREDIT OPPORTUNITIES FUND | Leverage Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Leverage Risk: If the Fund uses leverage through activities such as borrowing, entering into short sales, purchasing securities on margin or on a “when-issued” basis or purchasing derivative instruments in an effort to increase its returns, the Fund has the risk of magnified capital losses that occur when losses affect an asset base, enlarged by borrowings or the creation of liabilities, that exceeds the net assets of the Fund. Should the Fund employ leverage, the Fund’s NAV may be more volatile and sensitive to market movements. Leverage may involve the creation of a liability that requires the Fund to pay interest.

WATER ISLAND CREDIT OPPORTUNITIES FUND | WATER ISLAND CREDIT OPPORTUNITIES FUND | Currency Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Currency Risk: Fluctuations in exchange rates between the U.S. dollar and foreign currencies may negatively affect an investment in the Fund. Adverse changes in exchange rates may erode or reverse any gains produced by foreign currency denominated investments and may widen any losses. The Fund may, but is not required to, seek to reduce currency risk by hedging part or all of its exposure to various foreign currencies. The return of currency forward and futures contracts utilized for currency hedging may not perfectly offset the actual fluctuations of the foreign currencies relative to the U.S. dollar and may prevent the Fund from realizing gains from an increase in the value of the currency. In addition to currency risk, currency forward/futures contracts, like other derivatives, may be susceptible to credit risk and other risks. Further, in order to minimize transaction costs, or for other reasons, the Fund’s exposure to non-U.S. currencies may not be hedged.

ALTSHARES MERGER ARBITRAGE ETF | AltShares Merger Arbitrage ETF | Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] As with all funds, investing in the Fund entails risks that could cause the Fund and the Fund’s investors to lose money.
ALTSHARES MERGER ARBITRAGE ETF | AltShares Merger Arbitrage ETF | Risk Nondiversified Status [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Non-Diversification Risk: The Fund is non-diversified, which means that it may invest a relatively high percentage of its assets in a limited number of issuers. As a result, the Fund’s performance may be more vulnerable to changes in market value of a single issuer or group of issuers and more susceptible to risks associated with the occurrence of adverse events affecting a particular issuer than a diversified fund.

ALTSHARES MERGER ARBITRAGE ETF | AltShares Merger Arbitrage ETF | Merger Arbitrage Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Merger Arbitrage Risk: The principal risk associated with the Fund’s merger arbitrage investment strategy is that the proposed corporate reorganizations in which the Fund invests may not be completed or may be completed on less favorable terms than originally anticipated, in which case the Fund may realize losses.

ALTSHARES MERGER ARBITRAGE ETF | AltShares Merger Arbitrage ETF | Passive Investment Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Passive Investment Risk: The Fund is not actively managed, does not seek to “beat” the Underlying Index, and does not take temporary defensive positions when markets decline. Therefore, the Fund may not sell a security due to current or projected underperformance of a security, industry, or sector.

ALTSHARES MERGER ARBITRAGE ETF | AltShares Merger Arbitrage ETF | Short Sale Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Short Sale Risk: The Fund may obtain short exposure by borrowing a security to sell or by trading a derivative instrument, such as a future, forward or swap. The Fund will suffer a loss if it sells a security short and the value of the security rises rather than falls. There is no theoretical ceiling to the price of a shorted security. Therefore, in theory, securities sold short have unlimited risk. Short sales also 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. The Fund’s investment performance may also suffer if it is required to close out a short position earlier than it had intended. In addition, the Fund may be subject to expenses related to short sales that are not typically associated with investing in securities directly, such as costs of borrowing. These expenses may negatively impact the Fund’s performance. When the Fund sells a security short, it must maintain cash or high-grade securities equal to the margin requirement. As a result, the Fund may maintain high levels of cash or other liquid assets (such as U.S. Treasury bills, money market instruments, certificates of deposit, high quality commercial paper, and long equity positions). The need to maintain cash or other liquid assets could limit the Fund’s ability to pursue other opportunities as they arise. Short exposure generally introduces more risk to the Fund than long positions (purchases). It is also possible that the Fund’s long positions will decline in value at the same time that the value of its short positions increases, thereby increasing potential losses to the Fund.

ALTSHARES MERGER ARBITRAGE ETF | AltShares Merger Arbitrage ETF | Concentration Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Concentration Risk: If a large percentage of mergers or other corporate events taking place within the U.S. are within one industry over a given period of time, the Underlying Index may be concentrated in an industry or group of industries or sectors. Because the Fund’s assets are expected to be concentrated in an industry or group of industries or sectors to the same extent as the Underlying Index, the Fund is subject to loss due to adverse occurrences affecting that industry or group of industries or sectors. During such a period of concentration, the Fund may be subject to greater volatility than a fund that is more broadly diversified.

ALTSHARES MERGER ARBITRAGE ETF | AltShares Merger Arbitrage ETF | High Portfolio Turnover Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

High Portfolio Turnover Risk: The Fund’s strategy is expected to involve buying and selling portfolio securities frequently to rebalance the Fund’s investment exposures, which may increase brokerage commission costs and reduce performance. High portfolio turnover also exposes shareholders to a higher current realization of short-term gains, which could cause you to pay higher taxes.

ALTSHARES MERGER ARBITRAGE ETF | AltShares Merger Arbitrage ETF | Foreign Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Foreign Securities Risk: The securities of foreign issuers may be less liquid and more volatile than securities of comparable U.S. issuers. Transaction costs may be higher in foreign countries than in the U.S. The U.S. dollar value of foreign securities traded in foreign currencies (and any dividends and interest earned) held by the Fund may be affected favorably or unfavorably by changes in foreign currency exchange rates. An increase in the U.S. dollar relative to these other currencies may adversely affect the Fund. Additionally, investments in foreign securities, even those publicly traded in the U.S., may involve risks which are in addition to those inherent in U.S. investments. Foreign governments and economies often are less stable than the U.S. Government and the U.S. economy, and foreign companies may not be subject to the same regulatory requirements and accounting, auditing, and financial reporting standards of U.S. companies. As a consequence, there may be less publicly available information about such companies, which may negatively affect the value of foreign securities held by the Fund.

ALTSHARES MERGER ARBITRAGE ETF | AltShares Merger Arbitrage ETF | Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Market Risk: The value of the Fund’s investments, and the net asset value (“NAV”) of the Fund, will fluctuate over time, sometimes rapidly and unpredictably. Market risk may affect a single issuer, an entire industry, or the market as a whole. Securities markets may experience short-term or even extended periods of heightened volatility and turmoil. These events could have an adverse effect on the value of the Fund’s investments, and investors could lose money due to this price fluctuation. The value of a security may decline due to factors that are specifically related to a particular company, as well as general market conditions, such as real or perceived adverse economic or political conditions, inflation rates, changes in interest rates, or adverse investor sentiment. Geopolitical and other risks, including terrorism, war and sanctions, and environmental and public health risks (such as natural disasters, epidemics, and pandemics), may add to instability in world economies and markets generally. This uncertainty could lead to corporate events such as mergers, acquisitions, and restructurings breaking. The extent and duration of such market disruptions cannot be predicted but could magnify the impact of other risks to the Fund, could have a significant adverse impact on the Fund and its investments, and could result in increased volatility of the Fund’s NAV.

ALTSHARES MERGER ARBITRAGE ETF | AltShares Merger Arbitrage ETF | Sector Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Sector Risk: The securities of companies in the same or related businesses (“sectors”), if comprising a significant portion of the Fund’s portfolio, may in some circumstances react negatively to market conditions, interest rates and economic, regulatory or financial developments, and may adversely affect the value of the Fund’s portfolio, to a greater extent than if such securities comprised a lesser portion of the Fund’s portfolio or if the Fund’s portfolio was diversified across a greater number of sectors. Some sectors have particular risks that may not affect other sectors.

ALTSHARES MERGER ARBITRAGE ETF | AltShares Merger Arbitrage ETF | Equity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Equity Risk: Common stocks are susceptible to general stock market fluctuations and to volatile increases and decreases in value as market confidence in and perceptions of their issuers change. Preferred stocks are subject to the risk that the dividend on the stock may be changed or omitted by the issuer, and that participation in the growth of an issuer may be limited.

ALTSHARES MERGER ARBITRAGE ETF | AltShares Merger Arbitrage ETF | Derivatives Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Derivatives Risk: A derivative instrument (such as a forward contract, option (both written and purchased), or swap contract) typically involves leverage and provides exposure to potential gain or loss from a change in the market price of the underlying asset (or a basket of assets or an index) in a notional amount that exceeds the amount of cash or assets required to establish or maintain the derivative instrument. Adverse changes in the value or price of the underlying asset (or basket of assets or index), which the Fund may not directly own, can result in a loss to the Fund substantially greater than the amount invested in the derivative itself. The use of derivative instruments also exposes the Fund to additional risks and transaction costs.

ALTSHARES MERGER ARBITRAGE ETF | AltShares Merger Arbitrage ETF | Hedging Transaction Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Hedging Transaction Risk: Instruments used to hedge against an opposite position may offset losses, but they also may offset gains. Hedging transactions involve the risk of imperfect correlation. Imperfect correlation may prevent the Fund from achieving the intended hedge or expose the Fund to risk of loss. Hedging transactions also limit the opportunity for gain if the value of a hedged portfolio position should increase.

ALTSHARES MERGER ARBITRAGE ETF | AltShares Merger Arbitrage ETF | Counterparty Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Counterparty Risk: The Fund may enter into various types of derivative contracts with a counterparty that may be privately negotiated in the over-the-counter market. These contracts involve exposure to credit risk, because contract performance depends, in part, on the financial condition of the counterparty. If the creditworthiness of the counterparty declines, the Fund may not receive payments owed under the contract, or such payments may be delayed, and the value of agreements with the counterparty can be expected to decline, potentially resulting in losses to the Fund.

ALTSHARES MERGER ARBITRAGE ETF | AltShares Merger Arbitrage ETF | ETF Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

ETF Risk: As an ETF, the Fund is subject to the following risks:

Premium-Discount Risk: Shares may trade above or below their NAV. Accordingly, investors may pay more than NAV when purchasing Shares or receive less than NAV when selling Shares.

Secondary Market Trading Risk: Investors buying or selling Shares in the secondary market may pay bid-ask spreads, brokerage commissions or other charges, which may be a significant proportional cost for investors seeking to buy or sell Shares. There can be no assurance that an active or liquid trading market for Shares will develop or be maintained or that the Shares will continue to be listed. In addition, trading in Shares on the Exchange may be halted.

Cash Transactions Risk: The Fund may effect redemptions partly or wholly for cash, rather than through in-kind distributions of securities. Accordingly, the Fund may be required to sell portfolio securities in order to obtain the cash needed to distribute redemption proceeds and it may recognize gains on sales of portfolio holdings. As a result, an investment in the Fund may be less tax-efficient than an investment in an ETF that primarily or wholly effects redemptions in-kind. Moreover, cash transactions may have to be carried out over several days if the securities markets are relatively illiquid at the time the Fund must sell securities and may involve considerable brokerage fees and taxes. These brokerage fees and taxes, which will be higher than if the Fund redeemed its shares principally in-kind, may be passed on to Authorized Participants (“APs”) in the form of transaction fees. As a result, the spreads between the bid and the offered prices of the Fund’s shares may be wider than those of shares of ETFs that primarily or wholly transact in-kind.

International Closed Market Trading Risk: Because certain of the Fund’s investments trade in markets that are closed when the Fund and Exchange are open, there are likely to be deviations between the current prices of such investments and the prices at which such investments are marked for purposes of the Fund’s NAV. As a result, Shares may appear to trade at a significant discount or premium to NAV. In addition, shareholders may not be able to purchase or redeem their shares of the Fund, or purchase or sell shares of the Fund on the Exchange, on days when the NAV of the Fund could be significantly affected by events in the relevant non-U.S. markets.

Flash Crash Risk: Sharp price declines in securities owned by the Fund may trigger trading halts, which may result in the Fund’s shares trading in the market at an increasingly large discount to NAV during part (or all) of a trading day or cause the Fund itself to halt trading.

Authorized Participants Concentration Risk: The Fund may have a limited number of financial institutions that may act as APs. To the extent that those APs exit the business or are unable to process creation and/or redemption orders, Shares may trade at a discount to NAV like closed-end fund shares and may face delisting from the Exchange.

ALTSHARES MERGER ARBITRAGE ETF | AltShares Merger Arbitrage ETF | Swap Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Swap Risk: The Fund may enter into total return swaps to gain investment exposure to the underlying security or securities in a more efficient or economically attractive manner than direct ownership. In a standard “swap” transaction, two parties agree to exchange the returns (or differentials in rates of return) earned or realized on particular predetermined investments or instruments. Certain categories of swap agreements often have terms of greater than seven days and may be considered illiquid. Moreover, the Fund bears the risk of loss of the amount expected to be received under a swap agreement in the event of the default or bankruptcy of a swap agreement counterparty. It is possible that developments in the swaps market, including new and additional government regulation, could result in higher Fund costs and expenses and could adversely affect the Fund’s ability, among other things, to terminate existing swap agreements or to realize amounts to be received under such agreements.

ALTSHARES MERGER ARBITRAGE ETF | AltShares Merger Arbitrage ETF | Investment Company and ETF Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Investment Company and ETF Risk: Investing in securities issued by other investment companies, including ETFs, involves risks similar to those of investing directly in the securities and other assets held by the investment company or ETF. The Fund will indirectly bear its pro rata share of the fees and expenses incurred by a fund it invests in, including advisory fees. These expenses are in addition to the advisory and other expenses that the Fund bears directly in connection with its own operations.

ALTSHARES MERGER ARBITRAGE ETF | AltShares Merger Arbitrage ETF | Tracking Error Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Tracking Error Risk: Tracking error is the divergence of the Fund’s performance from that of the Underlying Index, which may be due to the Fund’s use of representative sampling or other differences between the Fund’s and Underlying Index’s holdings, transaction and operating costs, and security valuation procedures. This risk is heightened during times of market volatility.

ALTSHARES MERGER ARBITRAGE ETF | AltShares Merger Arbitrage ETF | Large Shareholder Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Large Shareholder Risk: Certain shareholders, including the Adviser or an affiliate of the Adviser, may own a substantial amount of the Fund’s Shares. Redemptions by large shareholders could have a significant negative impact on the Fund and transactions by large shareholders may account for a large percentage of the trading volume on the Exchange and may, therefore, have a material upward or downward effect on the market price of the Shares.

ALTSHARES MERGER ARBITRAGE ETF | AltShares Merger Arbitrage ETF | Market Capitalization Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Market Capitalization Risk: The securities of small-capitalization and mid-capitalization companies may be less liquid and more vulnerable to adverse business, economic, or market events than securities of relatively larger, more established companies.  Larger, more established companies may be unable to attain the high growth rates of successful, smaller- and medium-sized companies during periods of economic expansion.

ALTSHARES MERGER ARBITRAGE ETF | AltShares Merger Arbitrage ETF | Currency Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Currency Risk: Fluctuations in exchange rates between the U.S. dollar and foreign currencies may negatively affect an investment in the Fund. Adverse changes in exchange rates may erode or reverse any gains produced by foreign currency-denominated investments and may widen any losses. The return of the forward currency contracts and currency futures contracts utilized for currency hedging may not perfectly offset the actual fluctuations of the foreign currencies relative to the U.S. dollar and may prevent the Fund from realizing gains from an increase in the value of the currency. In addition to currency risk, currency forward/futures contracts, like other derivatives, may be susceptible to credit risk and other risks. Further, in order to minimize transaction costs, or for other reasons, the Fund’s exposure to non-U.S. currencies may not be hedged.

ALTSHARES EVENT-DRIVEN ETF | AltShares Event-Driven ETF | Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block] As with all funds, investing in the Fund entails risks that could cause the Fund and the Fund’s investors to lose money.
ALTSHARES EVENT-DRIVEN ETF | AltShares Event-Driven ETF | Merger Arbitrage Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Merger Arbitrage Risk: The principal risk associated with the Fund’s merger arbitrage investment strategy is that the proposed corporate reorganizations in which the Fund invests may not be completed or may be completed on less favorable terms than originally anticipated, in which case the Fund may realize losses.

ALTSHARES EVENT-DRIVEN ETF | AltShares Event-Driven ETF | Short Sale Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Short Sale Risk: The Fund may obtain short exposure by borrowing a security to sell or by trading a derivative instrument that has a similar economic effect, such as a future, forward or swap. The Fund will suffer a loss if it sells a security short and the value of the security rises rather than falls. There is no theoretical ceiling to the price of a shorted security. Therefore, in theory, securities sold short have unlimited risk. Short sales also 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. The Fund’s investment performance may also suffer if it is required to close out a short position earlier than it had intended. In addition, the Fund may be subject to expenses related to short sales that are not typically associated with investing in securities directly, such as costs of borrowing. These expenses may negatively impact the Fund’s performance. When the Fund sells a security short, it must maintain cash or high-grade securities equal to the margin requirement. As a result, the Fund may maintain high levels of cash or other liquid assets (such as U.S. Treasury bills, money market instruments, certificates of deposit, high quality commercial paper, and long equity positions). The need to maintain cash or other liquid assets could limit the Fund’s ability to pursue other opportunities as they arise. Short exposure generally introduces more risk to the Fund than long positions. It is also possible that the Fund’s long positions will decline in value at the same time that the value of its short positions increases, thereby increasing potential losses to the Fund.

ALTSHARES EVENT-DRIVEN ETF | AltShares Event-Driven ETF | Event-Driven Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Event-Driven Risk: Event-driven investments involve the risk that certain of the events driving the investment may not happen or the market may react differently than expected to the anticipated transaction. In addition, although an event may occur or is announced, it may be renegotiated, terminated, or involve a longer time frame than originally contemplated. Event-driven investment transactions are also subject to the risk of overall market movements. Any one of these risks could cause the Fund to experience investment losses, impacting its shares negatively.

ALTSHARES EVENT-DRIVEN ETF | AltShares Event-Driven ETF | Special Situations Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Special Situations Risk: The Fund may seek to benefit from “special situations,” such as mergers, acquisitions, consolidations, bankruptcies, liquidations, reorganizations, restructurings, tender or exchange offers, or other unusual events expected to affect a particular issuer. Investing in special situations carries the risk that certain of such situations may not happen as anticipated or the market may react differently than expected to such situations. The securities of companies involved in special situations may be more volatile than other securities, may at times be illiquid, or may be difficult to value. Certain special situations carry the additional risks inherent in difficult corporate transitions and the securities of such companies may be more likely to lose value than the securities of more stable companies.

ALTSHARES EVENT-DRIVEN ETF | AltShares Event-Driven ETF | Active Management Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Active Management Risk: The Fund is an actively managed investment portfolio and is therefore subject to management risk. The Adviser will apply its investment and risk analysis in making investment decisions for the Fund, but there is no guarantee that these decisions will produce the intended results.

ALTSHARES EVENT-DRIVEN ETF | AltShares Event-Driven ETF | Concentration Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Concentration Risk: If a large percentage of mergers or other corporate events taking place within the U.S. are within one industry over a given period of time, the Fund may invest a large portion of its assets in securities of issuers in a single industry for that period of time. During such a period of concentration, the Fund may be subject to greater volatility with respect to its portfolio securities than a fund that is more broadly diversified.

ALTSHARES EVENT-DRIVEN ETF | AltShares Event-Driven ETF | High Portfolio Turnover Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

High Portfolio Turnover Risk: The Fund normally expects to engage in active and frequent trading and expects to have a high portfolio turnover rate (over 100%). This may increase the Fund’s brokerage commission costs, which would reduce performance. Rapid portfolio turnover also exposes shareholders to a higher current realization of short-term gains, which could cause you to pay higher taxes.

ALTSHARES EVENT-DRIVEN ETF | AltShares Event-Driven ETF | Interest Rate Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Interest Rate Risk: Prices of debt securities and preferred stocks tend to move inversely with changes in interest rates. When interest rates fall, the market value of the respective debt securities and preferred securities usually increases. Conversely, when interest rates rise, the market value of the respective debt securities and preferred securities usually declines. As such, a change in interest rates may affect prices of the Fund’s debt securities and preferred securities and, accordingly, the Fund’s share price.

ALTSHARES EVENT-DRIVEN ETF | AltShares Event-Driven ETF | Foreign Securities Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Foreign Securities Risk: The securities of foreign issuers may be less liquid and more volatile than securities of comparable U.S. issuers. Transaction costs may be higher in foreign countries than in the U.S. The U.S. dollar value of foreign securities traded in foreign currencies held by the Fund (and any dividends and interest earned) may be affected favorably or unfavorably by changes in foreign currency exchange rates. An increase in the U.S. dollar relative to these other currencies may adversely affect the Fund. Additionally, investments in foreign securities, even those publicly traded in the U.S., may involve risks which are in addition to those inherent in U.S. investments. Foreign governments and economies often are less stable than the U.S. Government and the U.S. economy, and foreign companies may not be subject to the same regulatory requirements and accounting, auditing, and financial reporting standards of U.S. companies. As a consequence, there may be less publicly available information about such companies, which may negatively affect the value of foreign securities held by the Fund.

ALTSHARES EVENT-DRIVEN ETF | AltShares Event-Driven ETF | Market Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Market Risk: The value of the Fund’s investments, and the net asset value (“NAV”) of the Fund, will fluctuate over time, sometimes rapidly and unpredictably. Market risk may affect a single issuer, an entire industry, or the market as a whole. Securities markets may experience short-term or even extended periods of heightened volatility and turmoil. These events could have an adverse effect on the value of the Fund’s investments, and investors could lose money due to this price fluctuation. The value of a security may decline due to factors that are specifically related to a particular company, as well as general market conditions, such as real or perceived adverse economic or political conditions, inflation rates, changes in interest rates, or adverse investor sentiment. Geopolitical and other risks, including terrorism, war and sanctions, and environmental and public health risks (such as natural disasters, epidemics, and pandemics), may add to instability in world economies and markets generally. This uncertainty could lead to corporate events such as mergers, acquisitions, and restructurings breaking, forcing the Fund to allocate assets to other strategies. The extent and duration of such market disruptions cannot be predicted but could magnify the impact of other risks to the Fund, could have a significant adverse impact on the Fund and its investments, and could result in increased volatility of the Fund’s NAV.

ALTSHARES EVENT-DRIVEN ETF | AltShares Event-Driven ETF | Sector Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Sector Risk: The securities of companies in the same or related businesses (“sectors”), if comprising a significant portion of the Fund’s portfolio, may in some circumstances react negatively to market conditions, interest rates and economic, regulatory or financial developments, and may adversely affect the value of the Fund’s portfolio, to a greater extent than if such securities comprised a lesser portion of the Fund’s portfolio or if the Fund’s portfolio was diversified across a greater number of sectors. Some sectors have particular risks that may not affect other sectors.

ALTSHARES EVENT-DRIVEN ETF | AltShares Event-Driven ETF | Equity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Equity Risk: Common stocks are susceptible to general stock market fluctuations and to volatile increases and decreases in value as market confidence in and perceptions of their issuers change. Preferred stocks are subject to the risk that the dividend on the stock may be changed or omitted by the issuer, and that participation in the growth of an issuer may be limited.

ALTSHARES EVENT-DRIVEN ETF | AltShares Event-Driven ETF | Derivatives Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Derivatives Risk: In general, a derivative instrument typically involves leverage and provides exposure to potential gain or loss from a change in the market price of the underlying asset (or a basket of assets or an index) in a notional amount that exceeds the amount of cash or assets required to establish or maintain the derivative instrument. Adverse changes in the value or price of the underlying asset (or basket of assets or index), which the Fund may not directly own, can result in a loss to the Fund substantially greater than the amount invested in the derivative itself. The use of derivative instruments also exposes the Fund to additional risks and transaction costs. Derivative instruments come in many varieties and may include forward contracts, options (both written and purchased), and swap contracts.

ALTSHARES EVENT-DRIVEN ETF | AltShares Event-Driven ETF | Credit Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Credit Risk: Credit risk refers to the possibility that the issuer of the security will not be able to make interest or principal payments when due. The Fund may invest in convertible and non-convertible debt securities, including high yield debt securities, also known as “junk bonds.” Investments in junk bonds are subject to greater credit risks than securities with credit ratings above investment grade and have a greater risk of default than investment grade debt securities. Junk bonds are less sensitive to interest rate changes than higher credit quality instruments and generally are more sensitive to adverse economic changes or individual corporate developments.

ALTSHARES EVENT-DRIVEN ETF | AltShares Event-Driven ETF | Hedging Transaction Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Hedging Transaction Risk: Instruments used to hedge against an opposite position may offset losses, but they also may offset gains.  The success of the Fund’s hedging strategies will be subject to the Adviser’s ability to assess correctly the degree of correlation between the performance of the instruments used in the hedging strategies and the performance of the investments in the Fund’s portfolio being hedged. Hedging transactions involve the risk of imperfect correlation. Imperfect correlation may prevent the Fund from achieving the intended hedge or expose the Fund to risk of loss. Hedging transactions also limit the opportunity for gain if the value of a hedged portfolio position should increase.

ALTSHARES EVENT-DRIVEN ETF | AltShares Event-Driven ETF | Counterparty Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Counterparty Risk: The Fund may enter into various types of derivative contracts with a counterparty that may be privately negotiated in the over-the-counter market. These contracts involve exposure to credit risk, because contract performance depends, in part, on the financial condition of the counterparty. If the creditworthiness of the counterparty declines, the Fund may not receive payments owed under the contract, or such payments may be delayed, and the value of agreements with the counterparty can be expected to decline, potentially resulting in losses to the Fund.

ALTSHARES EVENT-DRIVEN ETF | AltShares Event-Driven ETF | ETF Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

ETF Risk: As an ETF, the Fund is subject to the following risks:

Premium-Discount Risk: Shares may trade above or below their NAV. Accordingly, investors may pay more than NAV when purchasing Shares or receive less than NAV when selling Shares.

Secondary Market Trading Risk: Investors buying or selling Shares in the secondary market may pay bid-ask spreads, brokerage commissions or other charges, which may be a significant proportional cost for investors seeking to buy or sell Shares. There can be no assurance that an active or liquid trading market for Shares will develop or be maintained or that the Shares will continue to be listed. In addition, trading in Shares on the Exchange may be halted.

Cash Transactions Risk: The Fund may effect redemptions partly or wholly for cash, rather than through in-kind distributions of securities. Accordingly, the Fund may be required to sell portfolio securities in order to obtain the cash needed to distribute redemption proceeds and it may recognize gains on sales of portfolio holdings. As a result, an investment in the Fund may be less tax-efficient than an investment in an ETF that primarily or wholly effects redemptions in-kind. Moreover, cash transactions may have to be carried out over several days if the securities markets are relatively illiquid at the time the Fund must sell securities and may involve considerable brokerage fees and taxes. These brokerage fees and taxes, which will be higher than if the Fund redeemed its shares principally in-kind, may be passed on to Authorized Participants (“APs”) in the form of transaction fees. As a result, the spreads between the bid and the offered prices of the Fund’s shares may be wider than those of shares of ETFs that primarily or wholly transact in-kind.

International Closed Market Trading Risk: Because certain of the Fund’s investments trade in markets that are closed when the Fund and Exchange are open, there are likely to be deviations between the current prices of such investments and the prices at which such investments are marked for purposes of the Fund’s NAV. As a result, Shares may appear to trade at a significant discount or premium to NAV. In addition, shareholders may not be able to purchase or redeem their shares of the Fund, or purchase or sell shares of the Fund on the Exchange, on days when the NAV of the Fund could be significantly affected by events in the relevant non-U.S. markets.

Flash Crash Risk: Sharp price declines in securities owned by the Fund may trigger trading halts, which may result in the Fund’s shares trading in the market at an increasingly large discount to NAV during part (or all) of a trading day or cause the Fund itself to halt trading.

Authorized Participants Concentration Risk: The Fund may have a limited number of financial institutions that may act as APs. To the extent that those APs exit the business or are unable to process creation and/or redemption orders, Shares may trade at a discount to NAV like closed-end fund shares and may face delisting from the Exchange.

ALTSHARES EVENT-DRIVEN ETF | AltShares Event-Driven ETF | Temporary Investment/Cash Management Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Temporary Investment/Cash Management Risk: The Fund may hold a significant portion of its assets in cash, money market or similar cash management funds, or short-term investments for temporary defensive purposes in response to adverse market, economic, political or other conditions, to preserve the Fund’s ability to capitalize quickly on new market opportunities or for other reasons, such as because the Adviser has determined to obtain investment exposure through derivative instruments instead of direct cash investments. These investments may include money market funds, money market instruments such as Treasury bills, securities issued by the U.S. Government, its agencies or instrumentalities, bankers’ acceptances, commercial paper, and repurchase agreements for the above securities, and investment companies that invest primarily in such instruments. To the extent the Fund maintains cash or holds short-term investments, the Fund may not achieve its investment objective and may also be subject to additional risks, including market, interest rate, and credit risk.

ALTSHARES EVENT-DRIVEN ETF | AltShares Event-Driven ETF | Swap Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Swap Risk: The Fund may enter into total return swaps to gain investment exposure to the underlying security or securities in a more efficient or economically attractive manner than direct ownership. In a standard “swap” transaction, two parties agree to exchange the returns (or differentials in rates of return) earned or realized on particular predetermined investments or instruments. The Fund may also enter into credit default or credit default index swaps with qualified broker-dealer counterparties. In a credit default swap, one party typically makes an upfront payment and a stream of payments to another party in exchange for the right to receive a specified return in the event of a default by a referenced entity on its obligation or other credit-related event. The Fund may use swaps for any investment purpose, including as part of a merger arbitrage or event-driven strategy involving pending corporate reorganizations. Certain categories of swap agreements often have terms of greater than seven days and may be considered illiquid. Moreover, the Fund bears the risk of loss of the amount expected to be received under a swap agreement in the event of the default or bankruptcy of a swap agreement counterparty. It is possible that developments in the swaps market, including new and additional government regulation, could result

in higher Fund costs and expenses and could adversely affect the Fund’s ability, among other things, to terminate existing swap agreements or to realize amounts to be received under such agreements.

ALTSHARES EVENT-DRIVEN ETF | AltShares Event-Driven ETF | Liquidity Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Liquidity Risk: Liquidity risk exists when particular investments are difficult to purchase or sell. Liquidity risk may be the result of, among other things, market turmoil, the reduced number and capacity of traditional market participants to make a market in fixed-income securities, or the lack of an active trading market. Markets for securities or financial instruments could be disrupted by a number of events, including, but not limited to, an economic crisis, natural disasters, new legislation or regulatory changes inside or outside the U.S. Liquid investments may become less liquid after being purchased by the Fund, particularly during periods of market stress. To enhance investment value and/or protect shareholder rights, from time to time, the Fund may participate in various types of litigation, including but not limited to shareholder appraisal rights petitions and class action lawsuits. If the Fund exercises its appraisal rights, it may experience limited liquidity on its investment while the subject securities are being appraised. Illiquid and relatively less liquid investments may be harder to value, especially in turbulent markets, and if the Fund is forced to sell these investments to meet redemption requests or for other cash needs, the Fund may suffer a loss.

ALTSHARES EVENT-DRIVEN ETF | AltShares Event-Driven ETF | Investment Company and ETF Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Investment Company and ETF Risk: Investing in securities issued by other investment companies, including ETFs, involves risks similar to those of investing directly in the securities and other assets held by the investment company or ETF. The Fund will indirectly bear its pro rata share of the fees and expenses incurred by a fund it invests in, including advisory fees. These expenses are in addition to the advisory and other expenses that the Fund bears directly in connection with its own operations.

ALTSHARES EVENT-DRIVEN ETF | AltShares Event-Driven ETF | Large Shareholder Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Large Shareholder Risk: Certain shareholders, including the Adviser or an affiliate of the Adviser, may own a substantial amount of the Fund’s Shares. Redemptions by large shareholders could have a significant negative impact on the Fund and transactions by large shareholders may account for a large percentage of the trading volume on the Exchange and may, therefore, have a material upward or downward effect on the market price of the Shares.

ALTSHARES EVENT-DRIVEN ETF | AltShares Event-Driven ETF | Leverage Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Leverage Risk: If the Fund uses leverage through activities such as borrowing, entering into short sales, purchasing securities on margin or on a “when-issued” basis or purchasing derivative instruments in an effort to increase its returns, the Fund has the risk of magnified capital losses that occur when losses affect an asset base, enlarged by borrowings or the creation of liabilities, that exceeds the net assets of the Fund. Should the Fund employ leverage, the Fund’s NAV may be more volatile and sensitive to market movements. Leverage may involve the creation of a liability that requires the Fund to pay interest.

ALTSHARES EVENT-DRIVEN ETF | AltShares Event-Driven ETF | Market Capitalization Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Market Capitalization Risk:  The securities of small-capitalization and mid-capitalization companies may be less liquid and more vulnerable to adverse business, economic, or market events than securities of relatively larger, more established companies. Larger, more established companies may be unable to attain the high growth rates of successful, smaller- and medium-sized companies during periods of economic expansion.

ALTSHARES EVENT-DRIVEN ETF | AltShares Event-Driven ETF | Currency Risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]

Currency Risk: Fluctuations in exchange rates between the U.S. dollar and foreign currencies may negatively affect an investment in the Fund. Adverse changes in exchange rates may erode or reverse any gains produced by foreign currency denominated investments and may widen any losses. The Fund may, but is not required to, seek to reduce currency risk by hedging part or all of its exposure to various foreign currencies. The return of currency forward and futures contracts utilized for currency hedging may not perfectly offset the actual fluctuations of the foreign currencies relative to the U.S. dollar and may prevent the Fund from realizing gains from an increase in the value of the currency. In addition to currency risk, currency forward/futures contracts, like other derivatives, may be susceptible to credit risk and other risks. Further, in order to minimize transaction costs, or for other reasons, the Fund’s exposure to non-U.S. currencies may not be hedged.