Label	Element	Value
Risk Return Abstract	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	THE ALGER FUNDS
Prospectus Date	rr_ProspectusDate	Feb. 28, 2025
Class Z Shares | Alger 35 Fund - Z
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 35 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 35 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>
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 year, the Fund’s portfolio turnover rate was 254.89% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	254.89%
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 is based on net operating expenses, which reflect the contractual expense limitation agreed to by the Manager. 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	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.Under normal circumstances, the Fund invests in a 35-stock portfolio of equity securities of companies of any market capitalization that the Manager believes are undergoing Positive Dynamic Change. Equity securities include common or preferred stocks, or securities convertible into or exchangeable for equity securities, including warrants and rights. The Fund may invest in companies whose securities are traded on domestic or foreign exchanges. The Fund focuses its investments in companies fostering and benefiting from technological improvements, advancements or developments. In the opinion of the Manager, these companies use technology extensively to improve their business processes, applications and opportunities or seek to grow through technological developments and innovations. The Fund intends to invest a substantial portion of its assets in a smaller number of issuers. Generally the Fund will own approximately 35 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 occasionally 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 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, health care, consumer discretionary and communication services 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	The following bar chart and the table beneath it provide some indication of the risks of investing in the Fund by showing changes in the Fund’s performance from year to year and by showing how the Fund’s average annual returns for the indicated periods compare with those of an appropriate broad-based securities market index that represents the overall domestic equity market and a more narrowly based index that reflects the market sectors in which the Fund invests. Effective upon the close of business May 7, 2021, Class P shares of the Fund were reclassified as Class Z shares.  The reclassified Class Z shares have the same annual returns as the Class P shares because the shares are invested in the same portfolio of securities and the reclassified Class Z shares have the same expenses as the Fund’s Class P shares. The Fund’s past performance (before and after taxes) is not necessarily an indication of how it will perform in the future. Updated performance information is available on the Fund’s website www.alger.com. The Russell 3000 Growth Index has been added as an index for comparison with the Fund’s performance and more closely reflects the market segments in which the Fund invests than the Fund’s broad-based securities market index.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	<span style="color:#262626;font-family:Arial;font-size:9pt;">The following bar chart and the table beneath it provide some indication of the risks of investing in the Fund by showing changes in the Fund’s performance from year to year and by showing how the Fund’s average annual returns for the indicated periods compare with those of an appropriate broad-based securities market index that represents the overall domestic equity market</span><span style="color:#262626;font-family:Arial;font-size:9pt;line-height:11pt;"> </span><span style="color:#262626;font-family:Arial;font-size:9pt;">and a more narrowly based index that reflects the market sectors in which the Fund invests. </span>
Performance Additional Market Index [Text]	rr_PerformanceAdditionalMarketIndex	<span style="color:#262626;font-family:Arial;font-size:9pt;">The Russell 3000 Growth Index has been added as an index for comparison with the Fund’s performance and more closely reflects the market segments in which the Fund invests than the Fund’s broad-based securities market index.</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 </span><span style="color:#262626;font-family:Arial;font-size:9pt;">necessarily an indication of how it will perform in the future.</span>
Bar Chart [Heading]	rr_BarChartHeading	<span style="color:#262626;font-family:Arial;font-size:10pt;font-weight:bold;">Annual Total Return for Class Z Shares</span><span style="color:#262626;font-family:Arial;font-size:10pt;line-height:12pt;"> </span><span style="color:#262626;font-family:Arial;font-size:10pt;font-style:italic;">as of December 31 (%)</span>
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	Best Quarter:Q2 202032.75%Worst Quarter:Q2 2022-21.96%
Performance Table Heading	rr_PerformanceTableHeading	<span style="color:#0064FA;font-family:Arial;font-size:10pt;font-weight:bold;">Average Annual Total Return as of December 31, 2024</span>
Performance Table Uses Highest Federal Rate	rr_PerformanceTableUsesHighestFederalRate	<span style="color:#262626;font-family:Arial;font-size:9pt;">after-tax returns are calculated using the historical highest individual federal marginal income tax rates and </span><span style="color:#262626;font-family:Arial;font-size:9pt;">do not reflect the impact of state and local taxes.</span>
Performance Table Not Relevant to Tax Deferred	rr_PerformanceTableNotRelevantToTaxDeferred	<span style="color:#262626;font-family:Arial;font-size:9pt;">Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. The after-tax returns shown may not be relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.</span>
Performance Table Narrative	rr_PerformanceTableNarrativeTextBlock	In the foregoing table, after-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. The after-tax returns shown may not be relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.
Class Z Shares | Alger 35 Fund - Z | 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 Z Shares | Alger 35 Fund - Z | 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 Z Shares | Alger 35 Fund - Z | 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 Z Shares | Alger 35 Fund - Z | 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 Z Shares | Alger 35 Fund - Z | 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. 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 Z Shares | Alger 35 Fund - Z | 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 Z Shares | Alger 35 Fund - Z | 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 Z Shares | Alger 35 Fund - Z | 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 Z Shares | Alger 35 Fund - Z | 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 Z Shares | Alger 35 Fund - Z | Health Care Sector Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	●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.
Class Z Shares | Alger 35 Fund - Z | 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 Z Shares | Alger 35 Fund - Z | Small Number of Holdings Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	Small Number of Holdings Risk – Under normal circumstances, the Fund invests in a 35-stock portfolio. 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.
Class Z Shares | Alger 35 Fund - Z | 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 Z Shares | Alger 35 Fund - Z | Small Cap and Mid Cap Securities Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	Small Cap and Mid Cap Securities Risk – There may be greater risk in investing in smaller, less seasoned 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.
Class Z Shares | Alger 35 Fund - Z | Foreign Securities Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	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.
Class Z Shares | Alger 35 Fund - Z | 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 Z Shares | Alger 35 Fund - Z | 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 Z Shares | Alger 35 Fund - Z | 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 Z Shares | Alger 35 Fund - Z | Class Z
Risk Return Abstract	rr_RiskReturnAbstract
Shareholder Fees (fees paid directly from your investment)	rr_ShareholderFeeOther	none
Advisory Fees	rr_ManagementFeesOverAssets	0.45%
Other Expenses	rr_OtherExpensesOverAssets	0.44%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.89%
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	(0.33%)	[1]
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement	rr_NetExpensesOverAssets	0.56%
1 Year	rr_ExpenseExampleYear01	$ 57
3 Years	rr_ExpenseExampleYear03	179
5 Years	rr_ExpenseExampleYear05	313
10 Years	rr_ExpenseExampleYear10	$ 701
2019	rr_AnnualReturn2019	30.56%
2020	rr_AnnualReturn2020	67.89%
2021	rr_AnnualReturn2021	9.94%
2022	rr_AnnualReturn2022	(36.36%)
2023	rr_AnnualReturn2023	31.41%
2024	rr_AnnualReturn2024	51.30%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	<span style="color:#262626;font-family:Arial;font-size:8pt;font-weight:bold;">Best Quarter:</span>
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2020
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	32.75%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	<span style="color:#262626;font-family:Arial;font-size:8pt;font-weight:bold;">Worst Quarter:</span>
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Jun. 30, 2022
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(21.96%)
1 Year	rr_AverageAnnualReturnYear01	51.30%
5 Years	rr_AverageAnnualReturnYear05	18.49%
Since Inception	rr_AverageAnnualReturnSinceInception	17.12%
Inception Date	rr_AverageAnnualReturnInceptionDate	Mar. 29, 2018
Class Z Shares | Alger 35 Fund - Z | Return After Taxes on Distributions | Class Z
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	51.16%
5 Years	rr_AverageAnnualReturnYear05	15.55%
Since Inception	rr_AverageAnnualReturnSinceInception	14.87%
Class Z Shares | Alger 35 Fund - Z | Return After Taxes on Distributions and Sale of Shares | Class Z
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	30.42%
5 Years	rr_AverageAnnualReturnYear05	14.05%
Since Inception	rr_AverageAnnualReturnSinceInception	13.37%
Class Z Shares | Alger 35 Fund - Z | S&P 500 Index (reflects no deductions for fees, expenses or taxes)
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	25.02%
5 Years	rr_AverageAnnualReturnYear05	14.53%
Since Inception	rr_AverageAnnualReturnSinceInception	14.49%
Class Z Shares | Alger 35 Fund - Z | Russell 3000 Growth Index (reflects no deductions for fees, expenses or taxes)
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	32.46%
5 Years	rr_AverageAnnualReturnYear05	18.25%
Since Inception	rr_AverageAnnualReturnSinceInception	17.82%

[1] Fred Alger Management, LLC (the “Manager”) has contractually agreed to limit the Other Expenses of the Fund so that such expenses never exceed 0.10% of average daily net assets of the Fund’s Class Z Shares. This commitment is currently expected to remain in place for the life of the Fund, can only be amended or terminated by agreement of the Fund’s Board of Trustees and the Manager, and will terminate automatically in the event of termination of the Investment Advisory Agreement. This expense reimbursement arrangement does not include dividend expense on short sales, borrowing costs, interest, taxes, brokerage and extraordinary expenses.