Alger International Opportunities Fund Investment Strategy - Class I Shares [Member] - Alger International Opportunities Fund	Oct. 31, 2025
Prospectus [Line Items]
Strategy [Heading]	<span style="color:#0064FA;font-family:Arial;font-size:10pt;font-weight:bold;">Principal Investment Strategy</span>
Strategy Narrative [Text Block]	The Fund is sub-advised by Redwood Investments, LLC (“Redwood”), an affiliate of the Manager (Redwood and the Manager, collectively referred to as the “Manager,” where applicable). Subject to the general supervision by the Fund’s Board of Trustees, the Manager oversees Redwood and evaluates its performance results. The Manager reviews portfolio performance, compliance with investment guidelines and federal securities laws, and changes in key personnel of Redwood. Redwood is primarily responsible for the day-to-day management of the Fund’s portfolio, including purchases and sales of individual securities.The Fund invests in companies that it believes meet three primary criteria: (1) high quality companies, (2) which are attractively valued, and (3) where the Manager believes that future earnings and free cash flow growth will be meaningfully above what is expected by the market. High quality companies are those companies that offer strong earnings visibility and sustainability because of their durable competitive advantages, capable management teams, and prudent financial management. The Manager focuses on understanding industry and company dynamics to assess company quality, and on identifying and forecasting critical drivers to reach a differentiated view of future growth. The Fund is an all-cap, all-country, opportunistic focus fund which generally holds less than 50 holdings. Fund holdings may differ from this number for a variety of reasons, including, among others, because of extreme market volatility, such as when the Fund has entered a temporary defensive position. Additionally, the Fund may exceed the stated number of holdings when it acquires a new holding and determines that it is in the best interests of shareholders to sell an existing holding over a period of time, instead of immediately selling the entire holding. Under normal circumstances, the Fund invests at least 80% of its net assets in equity securities, including common stocks, American Depositary Receipts and Global Depositary Receipts, of foreign companies. Foreign companies, which are generally defined by a third party, but may be defined by the Portfolio Manager, are companies that (i) that are organized under the laws of a foreign country; (ii) whose securities are primarily listed in a foreign country; or (iii) that have a majority of their assets, or derive more than 50% of their revenue or profits from businesses, investments, or sales, outside the United States. The Fund normally focuses its foreign investments in developed countries, but may also invest in emerging market securities. The Fund may invest in companies of any market capitalization, from large, well-established companies to small, emerging growth companies. Emerging market countries include all countries categorized as Emerging Markets or Frontier Markets by Morgan Stanley Capital International (MSCI). The Fund generally invests in at least three foreign countries, and, at times, may invest a substantial portion of its assets in a single foreign country.The Fund may sell a stock when it reaches a target price, it fails to perform as expected, or other opportunities appear more attractive. As a result, the Fund may engage in active trading of portfolio securities.The Fund may invest a significant portion of its assets in securities of companies conducting business within a single sector, as defined by third party sources, including, but not limited to, the information technology, communication services, industrials and financials sectors. For the purpose of categorizing companies, sectors are a broader category than industries and industries comprise sectors.The Fund may invest in cash (and cash equivalents) when the Fund is unable to find enough attractive long-term investments to meet its investment objective, to meet redemptions and/or when the Manager believes it is advisable to do so during times of short-term market volatility. During these times, cash (and cash equivalents) will not exceed 15% of the Fund’s net assets.The Fund’s investment objective is a fundamental policy and may not be changed without shareholder approval.

Alger International Opportunities Fund Investment Strategy - Class I Shares [Member] - Alger International Opportunities Fund

Oct. 31, 2025

<span style="color:#0064FA;font-family:Arial;font-size:10pt;font-weight:bold;">Principal Investment Strategy</span>

Strategy Narrative [Text Block]

The Fund is sub-advised by Redwood Investments, LLC (“Redwood”), an affiliate of the Manager (Redwood and the Manager, collectively referred to as the “Manager,” where applicable). Subject to the general supervision by the Fund’s Board of Trustees, the Manager oversees Redwood and evaluates its performance results. The Manager reviews portfolio performance, compliance with investment guidelines and federal securities laws, and changes in key personnel of Redwood. Redwood is primarily responsible for the day-to-day management of the Fund’s portfolio, including purchases and sales of individual securities.The Fund invests in companies that it believes meet three primary criteria: (1) high quality companies, (2) which are attractively valued, and (3) where the Manager believes that future earnings and free cash flow growth will be meaningfully above what is expected by the market. High quality companies are those companies that offer strong earnings visibility and sustainability because of their durable competitive advantages, capable management teams, and prudent financial management. The Manager focuses on understanding industry and company dynamics to assess company quality, and on identifying and forecasting critical drivers to reach a differentiated view of future growth. The Fund is an all-cap, all-country, opportunistic focus fund which generally holds less than 50 holdings. Fund holdings may differ from this number for a variety of reasons, including, among others, because of extreme market volatility, such as when the Fund has entered a temporary defensive position. Additionally, the Fund may exceed the stated number of holdings when it acquires a new holding and determines that it is in the best interests of shareholders to sell an existing holding over a period of time, instead of immediately selling the entire holding. Under normal circumstances, the Fund invests at least 80% of its net assets in equity securities, including common stocks, American Depositary Receipts and Global Depositary Receipts, of foreign companies. Foreign companies, which are generally defined by a third party, but may be defined by the Portfolio Manager, are companies that (i) that are organized under the laws of a foreign country; (ii) whose securities are primarily listed in a foreign country; or (iii) that have a majority of their assets, or derive more than 50% of their revenue or profits from businesses, investments, or sales, outside the United States. The Fund normally focuses its foreign investments in developed countries, but may also invest in emerging market securities. The Fund may invest in companies of any market capitalization, from large, well-established companies to small, emerging growth companies. Emerging market countries include all countries categorized as Emerging Markets or Frontier Markets by Morgan Stanley Capital International (MSCI). The Fund generally invests in at least three foreign countries, and, at times, may invest a substantial portion of its assets in a single foreign country.The Fund may sell a stock when it reaches a target price, it fails to perform as expected, or other opportunities appear more attractive. As a result, the Fund may engage in active trading of portfolio securities.The Fund may invest a significant portion of its assets in securities of companies conducting business within a single sector, as defined by third party sources, including, but not limited to, the information technology, communication services, industrials and financials sectors. For the purpose of categorizing companies, sectors are a broader category than industries and industries comprise sectors.The Fund may invest in cash (and cash equivalents) when the Fund is unable to find enough attractive long-term investments to meet its investment objective, to meet redemptions and/or when the Manager believes it is advisable to do so during times of short-term market volatility. During these times, cash (and cash equivalents) will not exceed 15% of the Fund’s net assets.The Fund’s investment objective is a fundamental policy and may not be changed without shareholder approval.