Label	Element	Value
Risk Return Abstract	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	THE ALGER FUNDS
Prospectus Date	rr_ProspectusDate	Feb. 28, 2025
Class I Shares | Alger Concentrated Equity Fund - I
Risk Return Abstract	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	<span style="color:#262626;font-family:Arial;font-size:10pt;font-weight:bold;text-transform:uppercase;">Alger Concentrated Equity Fund</span>
Objective [Heading]	rr_ObjectiveHeading	<span style="color:#0064FA;font-family:Arial;font-size:10pt;font-weight:bold;">Investment Objective</span>
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	Alger Concentrated Equity Fund seeks long-term capital appreciation.
Expense [Heading]	rr_ExpenseHeading	<span style="color:#0064FA;font-family:Arial;font-size:10pt;font-weight:bold;">Fund Fees and Expenses</span>
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	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.
Shareholder Fees Caption [Text]	rr_ShareholderFeesCaption	<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 [Text]	rr_OperatingExpensesCaption	<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>
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	<span style="color:#262626;font-family:Arial;font-size:8pt;">October 31, 2026</span>
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	<span style="color:#0064FA;font-family:Arial;font-size:10pt;font-weight:bold;">Portfolio Turnover</span>
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	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 example, affect the Fund’s performance. During the most recent fiscal period (since the Fund’s commencement of operations on April 4, 2024 through October 31, 2024) , the Fund’s portfolio turnover rate was 33.05% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	33.05%
Expense Example [Heading]	rr_ExpenseExampleHeading	<span style="color:#0064FA;font-family:Arial;font-size:9pt;font-weight:bold;">Example</span>
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	The following example is intended to help you compare the cost of investing in the Fund with the cost of investing in other funds. The example assumes 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. The example also assumes that the contractual fee waiver and/or expense reimbursement is only in effect through October 31, 2026. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading]	rr_StrategyHeading	<span style="color:#0064FA;font-family:Arial;font-size:10pt;font-weight:bold;">Principal Investment Strategy</span>
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	Under normal circumstances, the Fund invests at least 80% of its net assets, plus any borrowings for investment purposes, in equity securities of large-cap companies that the Manager believes demonstrate promising growth potential. For these purposes, “large-cap companies” are those companies that, at the time of purchase of the securities, have total market capitalization within the range of companies included in the Russell 1000 Growth Index. At December 31, 2024, the companies in this index ranged from $1.67 billion to $2.79 trillion. Equity securities include common or preferred stocks that are listed on U.S. exchanges. The Fund will invest at least 25% of its total assets in companies focused in the following group of related industries: software, technology hardware storage and peripherals, semiconductors and semiconductor equipment, information technology services, electronic equipment instruments and components, communications equipment, broadline retail and interactive media and services, as classified by third party sources. From time to time, the Fund may have 25% or more of its total assets invested in any one of these industries. The Fund intends to invest a substantial portion of its assets in a smaller number of issuers. Generally, the Fund will own no more than 30 holdings. As a result, the Fund is a non-diversified investment company, which means the performance results of any one position may have a greater impact on the Fund’s performance. Fund holdings may differ from this number for any reason. Such reasons may be, among others, because of extreme market volatility, such as when the Fund has entered a temporary defensive position. Additionally, the Fund may temporarily 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.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, consumer discretionary and communication services 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.
Risk [Heading]	rr_RiskHeading	<span style="color:#0064FA;font-family:Arial;font-size:10pt;font-weight:bold;">Principal Risks</span>
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	<span style="color:#0064FA;font-family:Arial;font-size:10pt;font-weight:bold;">Performance</span>
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	No performance information will be presented until the Fund has been in operation for a full calendar year. Annual performance information gives some indication of the risks of an investment in the Fund by comparing the Fund’s performance with a broad measure of market performance. The Fund’s past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. Updated performance information is available on the Fund’s website at www.alger.com.
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	<span style="color:#262626;font-family:Arial;font-size:9pt;">No performance information will be presented until the Fund has been in operation for a full calendar year.</span>
Performance Availability Website Address [Text]	rr_PerformanceAvailabilityWebSiteAddress	<span style="color:#262626;font-family:Arial;font-size:9pt;">www.alger.com</span>
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	<span style="color:#262626;font-family:Arial;font-size:9pt;">The Fund’s past performance (before and after taxes) is not necessarily an indication of how the </span><span style="color:#262626;font-family:Arial;font-size:9pt;">Fund will perform in the future.</span>
Class I Shares | Alger Concentrated Equity Fund - I | Risk Nondiversified Status [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	Non-Diversification Risk – The Fund is a non-diversified investment company. 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 diversified portfolio.
Class I Shares | Alger Concentrated Equity Fund - I | Risk Lose Money [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	The Fund’s share price may go down, which means you could lose money.
Class I Shares | Alger Concentrated Equity Fund - I | Risk Not Insured Depository Institution [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	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.
Class I Shares | Alger Concentrated Equity Fund - I | Investment Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	Investment Risk – An investment in the Fund is subject to investment risk, including the possible loss of the entire principal amount that you invest.
Class I Shares | Alger Concentrated Equity Fund - I | Market Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	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, recessions, or other events could have a significant impact on the Fund and its investments.
Class I Shares | Alger Concentrated Equity Fund - I | Equity Securities Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	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.
Class I Shares | Alger Concentrated Equity Fund - I | Growth Securities Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	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.
Class I Shares | Alger Concentrated Equity Fund - I | Concentration Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	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.
Class I Shares | Alger Concentrated Equity Fund - I | Sector Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	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.
Class I Shares | Alger Concentrated Equity Fund - I | Information Technology Sector Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	●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.
Class I Shares | Alger Concentrated Equity Fund - I | Consumer Discretionary Sector Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	●Consumer Discretionary Sector Risk – The consumer discretionary sector may be affected by changes in domestic and international economies, exchange and interest rates, competition, consumers’ disposable income, consumer preferences, social trends and marketing campaigns.
Class I Shares | Alger Concentrated Equity Fund - I | Communication Services Sector Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	●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.
Class I Shares | Alger Concentrated Equity Fund - I | Affiliate Ownership Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	Affiliate Ownership Risk – Certain shareholders, including other funds advised by the Manager or an affiliate of the Manager, may from time to time own a substantial amount of the shares of the Fund. In addition, a third party investor, the Manager or an affiliate of the Manager, or another entity may invest in the Fund and hold its investment for a limited period of time solely to facilitate commencement of the Fund or to facilitate the Fund’s achieving a specified size or scale. There can be no assurance that any large shareholder would not redeem its investment or that the size of the Fund would be maintained at such levels.  Accordingly, the Fund can be subject to the potential for large scale inflows and outflows as a result of purchases and redemptions made by large shareholders. Redemptions by large shareholders could have a significant negative impact on the Fund. Inflows and outflows could be significant, could cause the Fund to sell securities at inopportune times in order to meet redemption requests, and could cause the Fund’s portfolio turnover rate and transaction costs to rise, which may negatively affect the Fund’s performance and have adverse tax consequences for Fund shareholders.
Class I Shares | Alger Concentrated Equity Fund - I | Portfolio Turnover Active Trading Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	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.
Class I Shares | Alger Concentrated Equity Fund - I | Cash Position Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	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.
Class I Shares | Alger Concentrated Equity Fund - I | Class I
Risk Return Abstract	rr_RiskReturnAbstract
Shareholder Fees (fees paid directly from your investment)	rr_ShareholderFeeOther	none
Advisory Fees	rr_ManagementFeesOverAssets	0.45%
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses	rr_OtherExpensesOverAssets	6.22%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	6.92%
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(6.01%)	[1]
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement	rr_NetExpensesOverAssets	0.91%
1 Year	rr_ExpenseExampleYear01	$ 93
3 Years	rr_ExpenseExampleYear03	1,176
5 Years	rr_ExpenseExampleYear05	2,584
10 Years	rr_ExpenseExampleYear10	$ 5,874

[1] Fred Alger Management, LLC (the "Manager") has contractually agreed to waive and/or reimburse Fund expenses (excluding acquired fund fees and expenses, dividend expense on short sales, net borrowing costs, interest, taxes, brokerage expenses, fees in connection with the ReFlow Fund, LLC liquidity program, extraordinary expenses, and certain proxy expenses, to the extent applicable) through October 31, 2026 to the extent necessary to limit other expenses and any other applicable share class-specific expenses of the Class I Shares of the Fund to .35% of the class’s average daily net assets. This expense reimbursement may only be amended or terminated prior to its expiration date by agreement between the Manager and the Fund’s Board of Trustees, and will terminate automatically in the event of termination of the Investment Advisory Agreement. The Manager may recoup any fees waived or expenses reimbursed pursuant to the contract; however, the Fund will only make repayments to the Manager if such repayment does not cause the Fund’s expense ratio after the repayment is taken into account, to exceed both (i) the expense cap in place at the time such amounts were waived or reimbursed, and (ii) the Fund’s current expense cap. Such recoupment is limited to two years from the date the amount is initially waived or reimbursed.