Label	Element	Value
Risk Return Abstract	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	THE ALGER FUNDS
Prospectus Date	rr_ProspectusDate	Mar. 01, 2022
Class I Shares | Alger International Focus 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 International Focus Fund</span>
Objective [Heading]	rr_ObjectiveHeading	<span style="color:#0065D2;font-family:Arial;font-size:10pt;font-weight:bold;">Investment Objective</span>
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	Alger International Focus Fund seeks long-term capital appreciation.
Expense [Heading]	rr_ExpenseHeading	<span style="color:#0065D2;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;margin-left:0%;">(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;margin-left:0%;">(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;">February </span><span style="color:#262626;font-family:Arial;font-size:8pt;">29, 2024</span>
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	<span style="color:#0065D2;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 75.27% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	75.27%
Expense Example [Heading]	rr_ExpenseExampleHeading	<span style="color:#0065D2;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, 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 you would pay the following expenses whether or not you redeemed your shares at the end of each period:
Strategy [Heading]	rr_StrategyHeading	<span style="color:#0065D2;font-family:Arial;font-size:10pt;font-weight:bold;">Principal Investment Strategy</span>
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	The Fund invests in companies that it believes are attractively valued, high quality growth companies. High quality growth companies are those companies that have definable strategic advantages/moat and competitive positioning that offer strong earnings visibility and sustainability. Moat refers to a business’ ability to maintain competitive advantages over its competitors in order to protect its long-term profits and market share from competing firms. The Fund focuses on analyzing growth trajectories and identifying catalysts for future growth for companies that are in a positive earnings revision cycle. The Fund is an all-cap, all-country, opportunistic focus fund which generally holds less than 50 holdings. 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.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 are companies generally defined by a third party, or in certain circumstances by a Portfolio Manager, (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’s benchmark is the MSCI All Country World Index (ACWI) ex USA, which is an unmanaged, market capitalization-weighted index designed to provide a broad measure of equity market performance throughout the world, including both developed and emerging markets, but excluding the United States.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 the information technology, consumer discretionary, healthcare and industrials sectors.The Fund’s investment objective is a fundamental policy and may not be changed without shareholder approval.
Risk [Heading]	rr_RiskHeading	<span style="color:#0065D2;font-family:Arial;font-size:10pt;font-weight:bold;">Principal Risks</span>
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	An investment in the Fund involves risks. The Fund’s share price may go down, which means you could lose money. 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. The following is a summary description of principal risks involved in investing in the Fund.Investment Risk – An investment in the Fund is subject to investment risk, including the possible loss of the entire principal amount that you invest.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.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.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.Small Number of Holdings Risk – Under normal circumstances, the Fund invests in a small number of issuers. 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.Sector Risk – The Fund may have a significant portion of its assets invested in securities of companies conducting business within a single sector. 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.•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.•Technology Companies 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.•Healthcare Companies 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.•Industrial Companies Risk – The Fund may have a significant portion of its assets invested in securities of companies in the industrial sector. Industrial companies are affected by supply and demand both for their specific product or service and for industrial sector products in general. Government regulation, world events, exchange rates and economic conditions, technological developments and liabilities for environmental damage and general civil liabilities will likewise affect the performance of these companies. Aerospace and defense companies, a component of the industrial sector, can be significantly affected by government spending policies because companies involved in this industry rely, to a significant extent, on U.S. and foreign government demand for their products and services.Growth Stocks 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.Emerging Markets Risk – The Fund may invest in issuers located in emerging markets, and therefore may be exposed to the economies, industries, securities and currency markets of such countries, which may be adversely affected by protectionist trade policies, a slow U.S. economy, political and social instability, regional and global conflicts, terrorism and war, including actions that are contrary to the interests of the United States. Emerging markets are riskier than more developed markets because they tend to develop unevenly and may never fully develop. Investments in emerging markets may be considered speculative. Emerging markets are more likely to experience hyperinflation and currency devaluations, which adversely affect returns to U.S. investors. In addition, many emerging securities markets have far lower trading volumes and less liquidity than developed markets. The Fund, individually or in combination with other shareholders, may have limited rights and remedies against emerging market issuers.Small Cap Securities Risk – There may be greater risk in investing in companies with small market capitalizations rather than larger, more established companies owing to such factors as more limited product lines or financial resources or lack of management depth. 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.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.
Risk Lose Money [Text]	rr_RiskLoseMoney	<span style="color:#262626;font-family:Arial;font-size:9pt;">The Fund’s share price may go down, which means you could lose money.</span>
Risk Not Insured Depository Institution [Text]	rr_RiskNotInsuredDepositoryInstitution	<span style="color:#262626;font-family:Arial;font-size:9pt;"> 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.</span>
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	<span style="color:#0065D2;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 benchmark of market performance. Before March 28, 2018, the Fund followed different investment strategies and was managed by different portfolio managers. Prior to August 15, 2018 the Fund was named “Alger International Growth Fund.” Performance prior to March 28, 2018 reflects these prior management styles and does not reflect the Fund’s current investment strategies and investment personnel. 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.
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 benchmark of market performance.</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 I 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 202029.67%Worst Quarter:Q1 2020-19.70%
Performance Table Heading	rr_PerformanceTableHeading	<span style="color:#0065D2;font-family:Arial;font-size:10pt;font-weight:bold;">Average Annual Total Return as of December 31, 2021</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 I Shares | Alger International Focus Fund - I | Class I
Risk Return Abstract	rr_RiskReturnAbstract
Shareholder Fees (fees paid directly from your investment)	rr_ShareholderFeeOther	none
Advisory Fees	rr_ManagementFeesOverAssets	0.71%	[1]
Distribution and/or Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses	rr_OtherExpensesOverAssets	0.28%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.24%	[2]
1 Year	rr_ExpenseExampleYear01	$ 126
3 Years	rr_ExpenseExampleYear03	393
5 Years	rr_ExpenseExampleYear05	681
10 Years	rr_ExpenseExampleYear10	$ 1,500
2014	rr_AnnualReturn2014	(3.24%)
2015	rr_AnnualReturn2015	1.13%
2016	rr_AnnualReturn2016	(5.28%)
2017	rr_AnnualReturn2017	26.88%
2018	rr_AnnualReturn2018	(20.77%)
2019	rr_AnnualReturn2019	28.14%
2020	rr_AnnualReturn2020	43.40%
2021	rr_AnnualReturn2021	8.79%
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	29.67%
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	Mar. 31, 2020
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(19.70%)
Inception Date	rr_AverageAnnualReturnInceptionDate	May 31, 2013
Class I Shares | Alger International Focus Fund - I | Return Before Taxes | Class I
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	8.79%
5 Years	rr_AverageAnnualReturnYear05	14.98%
Since Inception	rr_AverageAnnualReturnSinceInception	9.12%
Class I Shares | Alger International Focus Fund - I | Return After Taxes on Distributions | Class I
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	6.73%
5 Years	rr_AverageAnnualReturnYear05	13.33%
Since Inception	rr_AverageAnnualReturnSinceInception	8.00%
Class I Shares | Alger International Focus Fund - I | Return After Taxes on Distributions and Sale of Shares | Class I
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	6.65%
5 Years	rr_AverageAnnualReturnYear05	11.33%
Since Inception	rr_AverageAnnualReturnSinceInception	6.86%
Class I Shares | Alger International Focus Fund - I | MSCI AC WORLD INDEX ex USA (reflects no deductions for fees, expenses or taxes)
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	8.29%
5 Years	rr_AverageAnnualReturnYear05	10.12%
Since Inception	rr_AverageAnnualReturnSinceInception	6.52%

[1] 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 .71%, and for assets in excess of $1 billion is .60%. The actual rate paid as a percentage of average daily net assets for the year ended October 31, 2021 was .71%.

[2] The Manager has contractually agreed to waive fees or to reimburse Fund expenses (excluding acquired fund fees and expenses, dividend expense on short sales, borrowing costs, interest, taxes, brokerage and extraordinary expenses, to the extent applicable) through February 29, 2024 to the extent necessary to limit the total annual fund operating expenses of the Class I Shares of the Fund to 1.25% 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, during the term of the contract, 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.