Alger Mid Cap Focus Fund Investment Risks - Class Y Shares [Member] - Alger Mid Cap Focus Fund	Oct. 31, 2025
Investment Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Investment Risk – An investment in the Fund is subject to investment risk, including the possible loss of the entire principal amount that you invest.
Market Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Market Risk – Your investment in Fund shares represents an indirect investment in the securities owned by the Fund. The value of these securities, like other investments, may move up or down, sometimes rapidly and unpredictably. Your Fund shares at any point in time may be worth less than what you invested, even after taking into account the reinvestment of Fund dividends and distributions. Local, regional or global events such as environmental or natural disasters, war, terrorism, pandemics, outbreaks of infectious diseases, and similar public health threats, trade disputes and changes in trade regulations, civil unrest, recessions, or other events could have a significant impact on the Fund and its investments.
Mid Cap Securities Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Mid Cap Securities Risk – There may be greater risk in investing in medium-capitalization companies rather than larger, more established companies due to such factors as inexperienced management and limited product lines or financial resources. It may also be difficult or impossible to liquidate a security position at a time and price acceptable to the Fund because of the potentially less frequent trading of stocks of smaller market capitalization. Often, medium capitalization companies and the industries in which they focus are still evolving and, as a result, they may be more sensitive to changing market conditions.
Equity Securities Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Equity Securities Risk – As with any fund that invests in stocks, your investment will fluctuate in value, and the loss of your investment is a risk of investing. The Fund’s price per share will fluctuate due to changes in the market prices of its investments. Also, the Fund’s investments may not grow as fast as the rate of inflation and stocks tend to be more volatile than some other investments you could make, such as bonds.
Concentration Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Concentration Risk – By focusing on an industry or a group of industries, the Fund carries much greater risks of adverse developments and price movements in such industries than a fund that invests in a wider variety of industries. Because the Fund concentrates in a specific industry or group of industries, there is also the risk that the Fund will perform poorly during a slump in demand for securities of companies in such industries.
Sector Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Sector Risk – The Fund may have a significant portion of its assets invested in securities of companies conducting business within a single sector, as defined by third party sources. Companies in the same sector may be similarly affected by economic, regulatory, political or market events or conditions, which may make the Fund more vulnerable to unfavorable developments in that sector than a fund that has a more diversified portfolio. Generally, the more broadly the Fund invests, the more it spreads risk and potentially reduces the risks of loss and volatility.
Information Technology Sector Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	●Information Technology Sector Risk – The Fund may have a significant portion of its assets invested in securities of technology-related companies. Therefore, the Fund may be more susceptible to particular risks that may affect companies in the information technology sector and technology-related sectors than if it were invested in a wider variety of companies in unrelated sectors. At times, the performance of such companies will lag the performance of other industries or the broader market as a whole. Certain technology related companies may face special risks that their products or services may not prove to be commercially successful. Technology related companies are also strongly affected by worldwide scientific or technological developments. As a result, their products may rapidly become obsolete. Such companies are also often subject to governmental regulation and may, therefore, be adversely affected by governmental policies. These factors may lead to limited earnings and/or failing profit margins. As a result, the value of technology related companies’ securities may fall or fail to rise. Many technology related companies’ securities have historically been more volatile than other securities, especially over the short term.
Health Care Sector Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	●Health Care Sector Risk – The Fund may have a significant portion of its assets invested in securities of healthcare companies. At times, the performance of healthcare companies will lag the performance of other industries or the broader market as a whole, and the performance of such companies may be more volatile. Healthcare companies may also be significantly affected by intense competition, aggressive pricing, government regulation, technological innovations, product obsolescence, patent considerations, product compatibility and consumer preferences.
Communication Services Sector Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	●Communication Services Sector Risk – Communication services companies are particularly vulnerable to the potential obsolescence of products and services due to technological advancement and the innovation of competitors. Companies in the communication services sector may also be affected by other competitive pressures, such as pricing competition, as well as research and development costs, substantial capital requirements and government regulation. Additionally, fluctuating domestic and international demand, shifting demographics and often unpredictable changes in consumer tastes can drastically affect a communication services company’s profitability. While all companies may be susceptible to network security breaches, certain companies in the communication services sector may be particular targets of hacking and potential theft of proprietary or consumer information or disruptions in service, which could have a material adverse effect on their businesses.
Industrials Sector Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	●Industrials Sector Risk – The Fund may have a significant portion of its assets invested in securities of companies in the industrials sector. Industrial companies are affected by supply and demand both for their specific product or service and for industrials sector products in general. Government regulation, world events, exchange rates and economic conditions, technological developments and liabilities for environmental damage and general civil liabilities will likewise affect the performance of these companies. Aerospace and defense companies, a component of the industrials sector, can be significantly affected by government spending policies because companies involved in this industry rely, to a significant extent, on U.S. and foreign government demand for their products and services.
Small Number of Holdings Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Small Number of Holdings Risk – Under normal circumstances, the Fund invests in a small number of issuers. Therefore, the Fund’s performance may be more vulnerable to changes in the market value of a single issuer and more susceptible to risks associated with a single economic, political, or regulatory occurrence than a fund that has a higher number of holdings.
Growth Securities Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Growth Securities Risk – Prices of growth stocks tend to be higher in relation to their companies’ earnings and may be more sensitive to market, political and economic developments than other stocks, making their prices more volatile. An investment in the Fund may be better suited to investors who seek long-term capital growth and can tolerate fluctuations in their investment’s value.
Privately Placed Securities Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Privately Placed Securities Risk – A private placement is an offering of a company’s securities that is not registered with the Securities and Exchange Commission (the “SEC”) and is not offered to the public. The issuers of privately placed securities are not typically subject to the same oversight and regulatory requirements, including disclosure and other investor protection requirements, to which public issuers are subject, and there may be very little public information available about the issuers and their performance. The sale or transfer of privately placed securities may be limited or prohibited by contract or law and such investments are generally considered to be illiquid. Privately placed securities are generally fair valued as they are not traded frequently. The Fund may be required to hold such positions for several years, if not longer, regardless of valuation, which may cause the Fund to be less liquid. As a result, investments in private placements can result in substantial or complete losses.
Foreign Securities Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Foreign Securities Risk – The Fund’s performance will be influenced by political, social and economic factors affecting investments in foreign companies. Special risks associated with investments in foreign companies include exposure to currency fluctuations, lack of liquidity, potential for market manipulation, less developed or less efficient trading markets, limited access to reliable capital, lack of comprehensive company information, political instability, differing audit, regulatory, and legal standards and lack of financial reporting standards. Additionally, events and evolving conditions in certain markets or regions may alter the risk profile of investments tied to those markets or regions. This may cause investments tied to such markets or regions to become riskier or more volatile, even when investments in such markets or regions were perceived as comparatively stable historically. In addition, foreign companies with securities listed on U.S. exchanges may be delisted if they do not meet U.S. accounting standards and auditor oversight requirements, which may decrease the liquidity and value of the securities.
Portfolio Turnover Active Trading Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Portfolio Turnover (Active Trading) Risk – Because the Fund may engage in active trading of portfolio securities, it may incur increased transaction costs and brokerage commissions, both of which can lower the actual return on an investment. Active trading may also increase short-term gains and losses, which may affect the taxes a shareholder has to pay.
Cash Position Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Cash Position Risk – At times, the Fund may hold up to 15% of its net assets in cash (and cash equivalents), which may underperform relative to equity securities.
Risk Lose Money [Member]
Prospectus [Line Items]
Risk [Text Block]	The Fund’s share price may go down, which means you could lose money.
Risk Not Insured Depository Institution [Member]
Prospectus [Line Items]
Risk [Text Block]	An investment in the Fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.