Alger Small Cap Growth Fund Investment Strategy - Class A B C Shares [Member] - Alger Small Cap Growth 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 Manager believes companies undergoing Positive Dynamic Change offer the best opportunities. Positive Dynamic Change refers to companies realizing High Unit Volume Growth or companies undergoing Positive Lifecycle Change. High Unit Volume Growth companies are traditional growth companies experiencing, for example, rapidly growing demand or market dominance. Positive Lifecycle Change companies are, for example, companies benefitting from new regulations, a new product innovation or new management.The Fund focuses on small, fast-growing companies that the Manager believes offer innovative products, services or technologies to a rapidly-expanding marketplace. The Fund normally invests at least 80% of its net assets, plus any borrowings for investment purposes, in equity securities of companies that, at the time of purchase of the securities, have a total market capitalization range of the Russell 2000 Growth Index. The Russell 2000 Growth Index is an index of small capitalization stocks. At December 31, 2025, the market capitalization of the companies in the Russell 2000 Growth Index ranged from $12.47 million to $25.69 billion. Because of the Fund’s long-term approach to investing, it could have a significant portion of its assets invested in securities of issuers that have appreciated beyond the market capitalization threshold noted. Equity securities include common or preferred stocks that are listed on U.S. exchanges.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, health care, industrials and consumer discretionary sectors. For the purpose of categorizing companies, sectors are a broader category than industries and industries comprise sectors.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 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.