Alger Mid Cap Growth Fund Fees and Expenses - Class A B C Shares [Member] - Alger Mid Cap Growth Fund	Oct. 31, 2025 USD ($)
Prospectus [Line Items]
Expense Heading [Optional Text]	<span style="color:#0064FA;font-family:Arial;font-size:10pt;font-weight:bold;">Fund Fees and Expenses</span>
Expense Narrative [Text Block]	This table describes the fees and expenses that you may pay if you buy, hold and sell shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the table and examples below.You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $25,000 in Class A Shares of the Alger Family of Funds, including the Fund. More information about these and other discounts is available from your financial professional and in “Purchasing and Redeeming Fund Shares” on page 79 and in Appendix A – Waivers and Discounts Available from Intermediaries on page A-1 in the Fund’s Prospectus, and in the sections “Right of Accumulation (Class A Shares)” and “Letter of Intent (Class A)” beginning on page 38 of the Fund’s Statement of Additional Information.
Expense Breakpoint Discounts [Text]	<span style="color:#262626;font-family:Arial;font-size:9pt;">You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least </span><span style="color:#262626;font-family:Arial;font-size:9pt;">$25,000</span><span style="color:#262626;font-family:Arial;font-size:9pt;"> in Class A Shares of the Alger Family of Funds, including the Fund.</span><span style="color:#262626;font-family:Arial;font-size:8pt;">The Fund and Fred Alger Management, LLC (the “Manager”) have adopted fee breakpoints for the Fund. The advisory fee for assets up to $1 billion is .76%, and for assets in excess of $1 billion is .70%. The actual rate paid as a percentage of average daily net assets for the year ended October 31, 2025 was .76%.</span>
Expense Breakpoint, Minimum Investment Required [Amount]	$ 25,000
Shareholder Fees Caption [Optional Text]	<span style="color:#262626;font-family:Arial;font-size:9pt;font-weight:bold;">Shareholder Fees</span> <br/><span style="color:#262626;font-family:Arial;font-size:9pt;">(fees paid directly from your investment)</span>
Operating Expenses Caption [Optional Text]	<span style="color:#262626;font-family:Arial;font-size:9pt;font-weight:bold;">Annual Fund Operating Expenses</span> <br/><span style="color:#262626;font-family:Arial;font-size:9pt;">(expenses that you pay each year as a percentage of the value of your investment)</span>
Expenses Deferred Charges [Text Block]	Purchases of $1 million or more of Class A Shares at net asset value may be subject to a contingent deferred sales charge of 1.00% on redemptions made within 12 months of purchase.
Expense Example [Heading]	<span style="color:#0064FA;font-family:Arial;font-size:9pt;font-weight:bold;">Example</span>
Expense Example Narrative [Text Block]	The following examples are intended to help you compare the cost of investing in the Fund with the cost of investing in other funds. The examples assume that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods, that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example, No Redemption, By Year, Caption [Text]	<span style="color:#262626;font-family:Arial;font-size:8pt;font-weight:bold;">You would pay the following expenses if you did not redeem your shares:</span>
Portfolio Turnover [Heading]	<span style="color:#0064FA;font-family:Arial;font-size:10pt;font-weight:bold;">Portfolio Turnover</span>
Portfolio Turnover [Text Block]	The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the examples, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 88.64% of the average value of its portfolio.
Portfolio Turnover, Rate	88.64%