Label	Element	Value
Risk Return Abstract	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	JANUS INVESTMENT FUND
Class A C S I N T Shares | Janus Henderson European Focus Fund
Risk Return Abstract	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	<span style="color:#000000;font-family:Times New Roman;font-size:15.20pt;font-weight:bold;margin-left:3pt;">Janus Henderson European Focus Fund</span>
Objective [Heading]	rr_ObjectiveHeading	<span style="color:#FFFFFF;font-family:Times New Roman;font-size:10.45pt;font-weight:bold;margin-left:0.0pt;text-transform:uppercase;">Investment Objective</span>
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	Janus Henderson European Focus Fund seeks long-term capital appreciation primarily through investment in equities of European companies.
Expense [Heading]	rr_ExpenseHeading	<span style="color:#FFFFFF;font-family:Times New Roman;font-size:10.45pt;font-weight:bold;margin-left:0.0pt;text-transform:uppercase;">Fees and Expenses of the Fund</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. Each share class has different expenses, but represents an investment in the same Fund. For Class A Shares, you may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Fund or in other Janus Henderson funds. More information about these and other discounts, as well as eligibility requirements for each share class, is available from your financial professional and in the “Purchases” section on page 128 of the Fund’s Prospectus and in the “Purchases” section on page 77 of the Fund’s Statement of Additional Information. In addition, please see Appendix A – Intermediary Sales Charge Waivers and Discounts. You may also incur brokerage commissions charged by your broker or financial intermediary when buying Class I Shares or Class N Shares of the Fund that are not reflected in the table or in the example below.
Shareholder Fees Caption [Text]	rr_ShareholderFeesCaption	SHAREHOLDER FEES (fees paid directly from your investment)
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	<span style="font-family:Times New Roman;font-size:7.60pt;">The Adviser has contractually agreed to waive its investment advisory fee and/or reimburse operating expenses to the extent that the Fund’s total annual fund operating expenses (excluding the fees payable pursuant to a Rule 12b-1 plan, shareholder servicing fees, such as transfer agency fees (including out-of-pocket costs), administrative services fees and any networking/omnibus fees payable by any share class, brokerage commissions, interest, dividends, taxes, acquired fund fees and expenses, and extraordinary expenses) exceed 0.96% for at least a one-year period commencing on January </span><span style="font-family:Times New Roman;font-size:7.60pt;line-height:9.50pt;"> </span><span style="font-family:Times New Roman;font-size:7.60pt;">26, 2024. This contractual waiver may be terminated or modified only at the discretion of the Board of Trustees.</span>
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	<span style="font-family:Times New Roman;font-size:9.50pt;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 169% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	169.00%
Expense Breakpoint Discounts [Text]	rr_ExpenseBreakpointDiscounts	<span style="font-family:Times New Roman;font-size:9.50pt;">For Class A Shares, you may qualify for sales charge </span><span style="font-family:Times New Roman;font-size:9.50pt;">discounts if you and your family invest, or agree to invest in the future, at least </span><span style="font-family:Times New Roman;font-size:9.50pt;">$50,000</span><span style="font-family:Times New Roman;font-size:9.50pt;"> in the Fund or in other Janus Henderson funds. More information about these and other discounts, as well as eligibility requirements for each share class, is available from your financial professional and in the “Purchases” section on page 128 of the Fund’s Prospectus and in the “Purchases” section on page 77 of the Fund’s Statement of Additional Information. In addition, please see Appendix A – Intermediary Sales Charge Waivers and Discounts. You may also incur brokerage commissions charged by your broker or financial intermediary when buying Class I Shares or Class N Shares of the Fund that are not reflected in the table or in the example below.</span>
Expense Breakpoint, Minimum Investment Required [Amount]	rr_ExpenseBreakpointMinimumInvestmentRequiredAmount	$ 50,000
Expense Example [Heading]	rr_ExpenseExampleHeading	<span style="color:#000000;font-family:Times New Roman;font-size:9.50pt;font-weight:bold;">EXAMPLE:</span>
Expense Example by Year [Heading]	rr_ExpenseExampleByYearHeading	<span style="font-family:Times New Roman;font-size:9.50pt;">The Example assumes that you invest $10,000 in the Fund for the time periods indicated and reinvest all dividends </span><span style="font-family:Times New Roman;font-size:9.50pt;">and distributions. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses are equal to the Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement for the first year and the Total Annual Fund Operating Expenses thereafter. Class C Shares automatically convert to Class A Shares </span><span style="color:#000000;font-family:Times New Roman;font-size:9.50pt;">after eight years. The Example for Class C Shares for the ten-year period reflects the conversion to Class A Shares. Although your actual costs may be higher or lower, based on these assumptions your costs would be:</span>
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.
Expense Example by, Year, Caption [Text]	rr_ExpenseExampleByYearCaption	If Shares are redeemed
Expense Example, No Redemption, By Year, Caption [Text]	rr_ExpenseExampleNoRedemptionByYearCaption	If Shares are not redeemed
Strategy [Heading]	rr_StrategyHeading	<span style="color:#FFFFFF;font-family:Times New Roman;font-size:10.45pt;font-weight:bold;margin-left:0.0pt;text-transform:uppercase;">Principal investment strategies</span>
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	The Fund pursues its investment objective by investing, under normal circumstances, at least 80% of its net assets (plus any borrowings for investment purposes) in equity securities of European companies. The Fund generally invests in a portfolio of 35-60 equity securities. Equity securities include common stocks and related securities. European companies are broadly defined to include any company that meets one or more of the following tests: (i) its country of organization, its primary business office and/or the principal trading market of its stock are located in Europe, (ii) 50% or more of its assets are located in Europe, or (iii) 50% or more of its revenues are derived from Europe.Portfolio management seeks investments that will increase in value by emphasizing stock selection. Stock selection is based on an opportunistic approach which seeks to utilize stock specific criteria described below and global market and industry dynamics that are expected to drive stock prices of European companies. Portfolio management will invest in both “growth” stocks that portfolio management believes are reasonably priced and “value” stocks that are, in portfolio management’s opinion, undervalued. Companies are evaluated using a broad range of criteria, including: (i) a company’s financial strength; (ii) competitive position in its industry; and (iii) projected future earnings and cash flows.The Fund may generally invest in companies located in Western European countries such as the United Kingdom, Belgium, Germany, Norway, the Netherlands, Denmark, Switzerland, Finland, Sweden, Portugal, France, Austria, Ireland, Italy and Spain. The Fund may, under unusual circumstances, invest in a single country or a limited number of countries.In evaluating investment opportunities in various market conditions, portfolio management conducts fundamental research that considers factors such as a company’s historic and projected return on capital, the quality of a company’s management,and a company’s historical valuations, as well as valuation relative to the wider market.The Fund will generally consider selling a stock when, in portfolio management’s opinion, there is a deterioration in the company’s fundamentals, the company fails to meet performance expectations, its earnings are disappointing, or its revenue growth has slowed. The Fund will also consider selling a stock if portfolio management believes that negative country, sector, or regional factors may affect the company’s outlook, or, in portfolio management’s opinion, a superior investment opportunity arises or to meet cash requirements.The Fund may engage in active and frequent trading to achieve its investment objective. The Fund does not limit its investments to companies of any particular size and may invest a significant portion of its assets in smaller and less seasoned issuers. However, in an attempt to reduce portfolio risks, portfolio management generally will invest across countries, industry groups and/or security types.The Fund may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions on a short-term or long-term basis, in an amount equal to up to one-third of its total assets as determined at the time of the loan origination.
Risk [Heading]	rr_RiskHeading	<span style="color:#FFFFFF;font-family:Times New Roman;font-size:10.45pt;font-weight:bold;margin-left:0.0pt;text-transform:uppercase;">Principal investment risks</span>
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	<span style="color:#FFFFFF;font-family:Times New Roman;font-size:10.45pt;font-weight:bold;margin-left:0.0pt;text-transform:uppercase;">Performance information</span>
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. Returns shown for periods prior to June 5, 2017, are those of Henderson European Focus Fund (the “Predecessor Fund”). The Predecessor Fund was advised by Henderson Global Investors (North America) Inc. and subadvised by Henderson Investment Management Limited. Class A Shares, Class C Shares, Class I Shares, and Class R6 Shares of the Predecessor Fund were reorganized into Class A Shares, Class C Shares, Class I Shares, and Class N Shares, respectively, of the Fund on June 2, 2017. Class A Shares and Class C Shares of the Predecessor Fund commenced operations with the Predecessor Fund’s inception on August 31, 2001. Class I Shares and Class R6 Shares of the Predecessor Fund commenced operations on March 31, 2009 and November 30, 2015, respectively. Class S Shares and Class T Shares of the Fund commenced operations on June 5, 2017.•The performance shown for Class A Shares for periods prior to June 5, 2017, reflects the performance of Class A Shares of the Predecessor Fund and is calculated using the fees and expenses of Class A Shares of the Predecessor Fund, in effect during the periods shown, net of any applicable fee and expense limitations or waivers.•The performance shown for Class C Shares for periods prior to June 5, 2017, reflects the performance of Class C Shares of the Predecessor Fund and is calculated using the fees and expenses of Class C Shares of the Predecessor Fund, in effect during the periods shown, net of any applicable fee and expense limitations or waivers.•The performance shown for Class I Shares for periods prior to June 5, 2017, reflects the performance of Class I Shares of the Predecessor Fund and is calculated using the fees and expenses of Class I Shares of the Predecessor Fund, in effect during the periods shown, net of any applicable fee and expense limitations or waivers, except that for periods prior to March 31, 2009, performance shown for Class I Shares reflects the performance of Class A Shares of the Predecessor Fund, calculated using the fees and expenses of Class A Shares of the Predecessor Fund (without sales charges), net of any applicable fee and expense limitations or waivers.•The performance shown for Class N Shares for periods prior to June 5, 2017, reflects the performance of Class R6 Shares of the Predecessor Fund and is calculated using the fees and expenses of Class R6 Shares of the Predecessor Fund, in effect during the periods shown, net of any applicable fee and expense limitations or waivers, except that for periods prior to November 30, 2015, performance shown for Class N Shares reflects the performance of Class A Shares of the Predecessor Fund, calculated using the fees and expenses of Class A Shares of the Predecessor Fund (without sales charges), net of any applicable fee and expense limitations or waivers.•The performance shown for Class S Shares for periods prior to June 5, 2017, reflects the performance of Class A Shares of the Predecessor Fund, calculated using the fees and expenses of Class A Shares of the Predecessor Fund (without sales charges), net of any applicable fee and expense limitations or waivers.•The performance shown for Class T Shares for periods prior to June 5, 2017, reflects the performance of Class A Shares of the Predecessor Fund, calculated using the fees and expenses of Class A Shares of the Predecessor Fund (without sales charges), net of any applicable fee and expense limitations or waivers.Returns of the Fund will be different from the Predecessor Fund as they have different expenses.The bar chart depicts the change in performance from year to year during the periods indicated. The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower.The table compares the Fund’s average annual returns for the periods indicated to a broad-based securities market index. All figures assume reinvestment of dividends and distributions.For certain periods, the Fund’s performance reflects the effect of expense waivers. Without the effect of these expense waivers, the performance shown would have been lower.The Fund’s (and the Predecessor Fund’s) past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future.Updated performance information is available at janushenderson.com/performance or by calling 1-877-335-2687.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	<span style="color:#000000;font-family:Times New Roman;font-size:9.50pt;">The bar chart depicts the change in performance from year to year during the periods indicated. </span><span style="color:#000000;font-family:Times New Roman;font-size:9.50pt;">The bar chart figures do not </span><span style="color:#000000;font-family:Times New Roman;font-size:9.50pt;">include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower.</span><span style="color:#000000;font-family:Times New Roman;font-size:9.50pt;">The table compares the Fund’s average annual returns for </span><span style="color:#000000;font-family:Times New Roman;font-size:9.50pt;">the periods indicated to a broad-based securities market index. All figures assume reinvestment of dividends and distributions.</span>
Performance Additional Market Index [Text]	rr_PerformanceAdditionalMarketIndex	<span style="color:#000000;font-family:Times New Roman;font-size:9.50pt;">The table compares the Fund’s average annual returns for </span><span style="color:#000000;font-family:Times New Roman;font-size:9.50pt;">the periods indicated to a broad-based securities market index. All figures assume reinvestment of dividends and distributions.</span>
Performance Availability Phone [Text]	rr_PerformanceAvailabilityPhone	<span style="color:#000000;font-family:Times New Roman;font-size:9.50pt;font-style:italic;">1-877-335-2687</span>
Performance Availability Website Address [Text]	rr_PerformanceAvailabilityWebSiteAddress	<span style="color:#000000;font-family:Times New Roman;font-size:9.50pt;font-style:italic;">janushenderson.com/performance</span>
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	<span style="color:#000000;font-family:Times New Roman;font-size:9.50pt;font-style:italic;">The Fund’s (and the Predecessor Fund’s) past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future.</span>
Bar Chart [Heading]	rr_BarChartHeading	Annual Total Returns for Class A Shares (calendar year-end)
Bar Chart Does Not Reflect Sales Loads [Text]	rr_BarChartDoesNotReflectSalesLoads	<span style="color:#000000;font-family:Times New Roman;font-size:9.50pt;">The bar chart figures do not </span><span style="color:#000000;font-family:Times New Roman;font-size:9.50pt;">include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower.</span>
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	Best Quarter:2nd Quarter 202020.74%Worst Quarter:4th Quarter 2018– 21.09%
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns (periods ended 12/31/23)
Performance Table Does Reflect Sales Loads	rr_PerformanceTableDoesReflectSalesLoads	<span style="color:#000000;font-family:Times New Roman;font-size:7.60pt;">The one year return is calculated to include the contingent deferred sales charge.</span>
Performance Table Uses Highest Federal Rate	rr_PerformanceTableUsesHighestFederalRate	<span style="color:#000000;font-family:Times New Roman;font-size:9.50pt;">After-tax returns are calculated using the historically highest individual </span><span style="color:#000000;font-family:Times New Roman;font-size:9.50pt;">federal marginal income tax rates and do not reflect the impact of state and local taxes.</span>
Performance Table Not Relevant to Tax Deferred	rr_PerformanceTableNotRelevantToTaxDeferred	<span style="color:#000000;font-family:Times New Roman;font-size:9.50pt;">Actual after-tax returns depend on </span><span style="color:#000000;font-family:Times New Roman;font-size:9.50pt;">your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-advantaged account, such as a 401(k) plan or an IRA.</span>
Performance Table One Class of after Tax Shown [Text]	rr_PerformanceTableOneClassOfAfterTaxShown	<span style="color:#000000;font-family:Times New Roman;font-size:9.50pt;">After-tax returns are only shown for Class A Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class A Shares due to varying sales charges (as applicable), fees, and expenses among the classes.</span>
Performance Table Narrative	rr_PerformanceTableNarrativeTextBlock	The Fund’s primary benchmark index is the MSCI Europe Index. The index is described below.•The MSCI Europe Index is designed to measure developed market equity performance in Europe.After-tax returns are calculated using distributions for the Predecessor Fund’s Class A Shares for the period prior to June 5, 2017. If Class A Shares of the Fund had been available during periods prior to June 5, 2017, the distributions used to calculate the after-tax returns may have been different. After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-advantaged account, such as a 401(k) plan or an IRA.After-tax returns are only shown for Class A Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class A Shares due to varying sales charges (as applicable), fees, and expenses among the classes.
Performance Table Closing [Text Block]	rr_PerformanceTableClosingTextBlock	Updated performance information is available at janushenderson.com/performance or by calling 1-877-335-2687.
Class A C S I N T Shares | Janus Henderson European Focus Fund | Risk Lose Money [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	The biggest risk is that the Fund’s returns will vary, and you could lose money.
Class A C S I N T Shares | Janus Henderson European Focus Fund | Risk Not Insured Depository Institution [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Class A C S I N T Shares | Janus Henderson European Focus Fund | Market Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	Market Risk. The value of the Fund’s portfolio may decrease due to short-term market movements and over more prolonged market downturns. As a result, the Fund’s net asset value may fluctuate and it may be more difficult to value or sell the Fund’s holdings. Market risk may affect a single issuer, industry, economic sector, or the market as a whole. Market risk may be magnified if certain social, political, economic, and other conditions and events (such as terrorism, conflicts, including related sanctions, social unrest, natural disasters, epidemics and pandemics, including COVID-19) adversely interrupt the global economy and financial markets. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money.
Class A C S I N T Shares | Janus Henderson European Focus Fund | Foreign Exposure Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	Foreign Exposure Risk. Foreign markets can be more volatile than the U.S. market. As a result, the Fund’s returns and net asset value may be affected by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio.
Class A C S I N T Shares | Janus Henderson European Focus Fund | Portfolio Management Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	Portfolio Management Risk. The Fund is an actively managed investment portfolio and is therefore subject to the risk that the investment strategies and research process employed for the Fund may fail to produce the intended results. Accordingly,the Fund may underperform its benchmark index or other mutual funds with similar investment objectives.
Class A C S I N T Shares | Janus Henderson European Focus Fund | Currency Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	Currency Risk. Currency risk is the risk that changes in the exchange rate between currencies will adversely affect the value (in U.S. dollar terms) of an investment. As long as the Fund holds a foreign security, its value will be affected by the value of the local currency relative to the U.S. dollar. When the Fund sells a foreign currency denominated security, its value may be worth less in U.S. dollars even if the security increases in value in its home country. U.S. dollar-denominated securities of foreign issuers may also be affected by currency risk, as the value of these securities may also be affected by changes in the issuer’s local currency.
Class A C S I N T Shares | Janus Henderson European Focus Fund | Geographic Concentration Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	Geographic Concentration Risk. To the extent the Fund invests a substantial amount of its assets in issuers located in a single country or region, the economic, political, social, regulatory, or other developments or conditions within such country or region will generally have a greater effect on the Fund than they would on a more geographically diversified fund, which may result in greater losses and volatility. Adverse developments in certain regions could also adversely affect securities of other countries whose economies appear to be unrelated and could have a negative impact on the Fund’s performance.
Class A C S I N T Shares | Janus Henderson European Focus Fund | Europe Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	•Europe Risk. The Fund is subject to certain risks related to Europe. Investments in British companies may subject the Fund to social, regulatory, political, currency, security, and economic risk specific to the United Kingdom. The United Kingdom has one of the largest economies in Europe, and the United States and other European countries are substantial trading partners of the United Kingdom. As a result, the British economy may be impacted by changes to the economic health of the United States and other European countries. Western Europe has, in certain instances, been susceptible to serious financial hardship, high debt levels, and high levels of unemployment. The European Union itself has experienced difficulties in connection with the debt loads of some of its member states.
Class A C S I N T Shares | Janus Henderson European Focus Fund | Issuer Concentration Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	Issuer Concentration Risk. The Fund’s portfolio may be comprised of a relatively small number of issuers in comparison to other funds. As a result, the Fund may be subject to greater risks than a fund that invests in a greater number of issuers. A change in the value of any single investment held by the Fund may affect the overall value of the Fund more than it would affect a fund that holds more investments. In particular, the Fund may be more susceptible to adverse developments affecting any single issuer held by the Fund and may be susceptible to greater losses because of these developments.
Class A C S I N T Shares | Janus Henderson European Focus Fund | Value Investing Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	Value Investing Risk. Because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “value” stocks may perform differently than other types of stocks and from the market as a whole, and can continue to be undervalued by the market for long periods of time. It is also possible that a value stock will never appreciate to the extent expected by portfolio management.
Class A C S I N T Shares | Janus Henderson European Focus Fund | Growth Securities Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	Growth Securities Risk. Securities of companies perceived to be “growth” companies may be more volatile than other stocks and may involve special risks. If portfolio management’s perception of a company’s growth potential is not realized, the securities purchased may not perform as expected, reducing the Fund’s returns. In addition, because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “growth” stocks may perform differently from other types of securities and the market as a whole.
Class A C S I N T Shares | Janus Henderson European Focus Fund | Portfolio Turnover Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	Portfolio Turnover Risk. Increased portfolio turnover may result in higher costs, which may have a negative effect on the Fund’s performance. In addition, higher portfolio turnover may result in the acceleration of capital gains and the recognition of greater levels of short-term capital gains, which are taxed at ordinary federal income tax rates when distributed to shareholders in a taxable account.
Class A C S I N T Shares | Janus Henderson European Focus Fund | Small- and Mid-Sized Companies Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	Small- and Mid-Sized Companies Risk. Investments in securities issued by small- and mid-sized companies, which can include smaller, start-up companies offering emerging products or services, may involve greater risks than are customarily associated with larger, more established companies. For example, small- and mid-sized companies may suffer more significant losses as a result of their narrow product lines, limited operating history, greater exposure to competitive threats, limited financial resources, limited trading markets, and the potential lack of management depth. Securities issued by small- and mid-sized companies tend to be more volatile and somewhat more speculative than securities issued by larger or more established companies and may underperform as compared to the securities of larger or more established companies. These holdings are also subject to wider price fluctuations and tend to be less liquid than stocks of larger or more established companies, which could have a significant adverse effect on the Fund’s returns, especially as market conditions change.
Class A C S I N T Shares | Janus Henderson European Focus Fund | Securities Lending Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	Securities Lending Risk. There is the risk that when portfolio securities are lent, the securities may not be returned on a timely basis, and the Fund may experience delays and costs in recovering the security or gaining access to the collateral provided to the Fund to collateralize the loan. If the Fund is unable to recover a security on loan, the Fund may use the collateral to purchase replacement securities in the market. There is a risk that the value of the collateral could decrease below the cost of the replacement security by the time the replacement investment is made, resulting in a loss to the Fund.
Class A C S I N T Shares | Janus Henderson European Focus Fund | Class A
Risk Return Abstract	rr_RiskReturnAbstract
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	5.75%
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds)	rr_MaximumDeferredSalesChargeOverOther	none
Management Fees	rr_ManagementFeesOverAssets	1.00%
Distribution/Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses	rr_OtherExpensesOverAssets	0.26%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.51%
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	0.21%	[1]
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement	rr_NetExpensesOverAssets	1.30%	[1]
1 Year	rr_ExpenseExampleYear01	$ 700
3 Years	rr_ExpenseExampleYear03	1,005
5 Years	rr_ExpenseExampleYear05	1,333
10 Years	rr_ExpenseExampleYear10	2,256
1 Year	rr_ExpenseExampleNoRedemptionYear01	700
3 Years	rr_ExpenseExampleNoRedemptionYear03	1,005
5 Years	rr_ExpenseExampleNoRedemptionYear05	1,333
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 2,256
2014	rr_AnnualReturn2014	(4.99%)
2015	rr_AnnualReturn2015	2.73%
2016	rr_AnnualReturn2016	(7.25%)
2017	rr_AnnualReturn2017	16.11%
2018	rr_AnnualReturn2018	(27.82%)
2019	rr_AnnualReturn2019	31.43%
2020	rr_AnnualReturn2020	26.49%
2021	rr_AnnualReturn2021	11.99%
2022	rr_AnnualReturn2022	(16.12%)
2023	rr_AnnualReturn2023	18.25%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	Best Quarter
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2020
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	20.74%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	Worst Quarter
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2018
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(21.09%)
Class A C S I N T Shares | Janus Henderson European Focus Fund | Class C
Risk Return Abstract	rr_RiskReturnAbstract
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds)	rr_MaximumDeferredSalesChargeOverOther	1.00%
Management Fees	rr_ManagementFeesOverAssets	1.00%
Distribution/Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.32%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.32%
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	0.24%	[1]
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement	rr_NetExpensesOverAssets	2.08%	[1]
1 Year	rr_ExpenseExampleYear01	$ 311
3 Years	rr_ExpenseExampleYear03	701
5 Years	rr_ExpenseExampleYear05	1,219
10 Years	rr_ExpenseExampleYear10	2,434
1 Year	rr_ExpenseExampleNoRedemptionYear01	211
3 Years	rr_ExpenseExampleNoRedemptionYear03	701
5 Years	rr_ExpenseExampleNoRedemptionYear05	1,219
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 2,434
Class A C S I N T Shares | Janus Henderson European Focus Fund | Class S
Risk Return Abstract	rr_RiskReturnAbstract
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds)	rr_MaximumDeferredSalesChargeOverOther	none
Management Fees	rr_ManagementFeesOverAssets	1.00%
Distribution/Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses	rr_OtherExpensesOverAssets	1.70%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.95%
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	1.49%	[1]
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement	rr_NetExpensesOverAssets	1.46%	[1]
1 Year	rr_ExpenseExampleYear01	$ 149
3 Years	rr_ExpenseExampleYear03	772
5 Years	rr_ExpenseExampleYear05	1,421
10 Years	rr_ExpenseExampleYear10	3,165
1 Year	rr_ExpenseExampleNoRedemptionYear01	149
3 Years	rr_ExpenseExampleNoRedemptionYear03	772
5 Years	rr_ExpenseExampleNoRedemptionYear05	1,421
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 3,165
Class A C S I N T Shares | Janus Henderson European Focus Fund | Class I
Risk Return Abstract	rr_RiskReturnAbstract
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds)	rr_MaximumDeferredSalesChargeOverOther	none
Management Fees	rr_ManagementFeesOverAssets	1.00%
Distribution/Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.26%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.26%
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	0.21%	[1]
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement	rr_NetExpensesOverAssets	1.05%	[1]
1 Year	rr_ExpenseExampleYear01	$ 107
3 Years	rr_ExpenseExampleYear03	379
5 Years	rr_ExpenseExampleYear05	671
10 Years	rr_ExpenseExampleYear10	1,504
1 Year	rr_ExpenseExampleNoRedemptionYear01	107
3 Years	rr_ExpenseExampleNoRedemptionYear03	379
5 Years	rr_ExpenseExampleNoRedemptionYear05	671
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 1,504
Class A C S I N T Shares | Janus Henderson European Focus Fund | Class N
Risk Return Abstract	rr_RiskReturnAbstract
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds)	rr_MaximumDeferredSalesChargeOverOther	none
Management Fees	rr_ManagementFeesOverAssets	1.00%
Distribution/Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.21%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.21%
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	0.25%	[1]
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement	rr_NetExpensesOverAssets	0.96%	[1]
1 Year	rr_ExpenseExampleYear01	$ 98
3 Years	rr_ExpenseExampleYear03	359
5 Years	rr_ExpenseExampleYear05	641
10 Years	rr_ExpenseExampleYear10	1,444
1 Year	rr_ExpenseExampleNoRedemptionYear01	98
3 Years	rr_ExpenseExampleNoRedemptionYear03	359
5 Years	rr_ExpenseExampleNoRedemptionYear05	641
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 1,444
Class A C S I N T Shares | Janus Henderson European Focus Fund | Class T
Risk Return Abstract	rr_RiskReturnAbstract
Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds)	rr_MaximumDeferredSalesChargeOverOther	none
Management Fees	rr_ManagementFeesOverAssets	1.00%
Distribution/Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.46%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.46%
Fee Waiver and/or Expense Reimbursement	rr_FeeWaiverOrReimbursementOverAssets	0.24%	[1]
Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement	rr_NetExpensesOverAssets	1.22%	[1]
1 Year	rr_ExpenseExampleYear01	$ 124
3 Years	rr_ExpenseExampleYear03	438
5 Years	rr_ExpenseExampleYear05	775
10 Years	rr_ExpenseExampleYear10	1,726
1 Year	rr_ExpenseExampleNoRedemptionYear01	124
3 Years	rr_ExpenseExampleNoRedemptionYear03	438
5 Years	rr_ExpenseExampleNoRedemptionYear05	775
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 1,726
Class A C S I N T Shares | Janus Henderson European Focus Fund | Return Before Taxes | Class A
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	11.44%	[2]
5 Years	rr_AverageAnnualReturnYear05	13.05%	[2]
10 Years	rr_AverageAnnualReturnYear10	3.43%	[2]
Since Inception	rr_AverageAnnualReturnSinceInception	11.01%	[2]
Inception Date	rr_AverageAnnualReturnInceptionDate	Aug. 31, 2001	[2]
Class A C S I N T Shares | Janus Henderson European Focus Fund | Return Before Taxes | Class C
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	16.40%	[3]
5 Years	rr_AverageAnnualReturnYear05	13.55%	[3]
10 Years	rr_AverageAnnualReturnYear10	3.26%	[3]
Since Inception	rr_AverageAnnualReturnSinceInception	10.47%	[3]
Inception Date	rr_AverageAnnualReturnInceptionDate	Aug. 31, 2001	[3]
Class A C S I N T Shares | Janus Henderson European Focus Fund | Return Before Taxes | Class S
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	18.19%
5 Years	rr_AverageAnnualReturnYear05	14.54%
10 Years	rr_AverageAnnualReturnYear10	4.05%
Since Inception	rr_AverageAnnualReturnSinceInception	11.31%
Inception Date	rr_AverageAnnualReturnInceptionDate	Aug. 31, 2001
Class A C S I N T Shares | Janus Henderson European Focus Fund | Return Before Taxes | Class I
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	18.52%
5 Years	rr_AverageAnnualReturnYear05	14.70%
10 Years	rr_AverageAnnualReturnYear10	4.32%
Since Inception	rr_AverageAnnualReturnSinceInception	11.50%
Inception Date	rr_AverageAnnualReturnInceptionDate	Aug. 31, 2001
Class A C S I N T Shares | Janus Henderson European Focus Fund | Return Before Taxes | Class N
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	18.64%
5 Years	rr_AverageAnnualReturnYear05	14.80%
10 Years	rr_AverageAnnualReturnYear10	4.31%
Since Inception	rr_AverageAnnualReturnSinceInception	11.43%
Inception Date	rr_AverageAnnualReturnInceptionDate	Aug. 31, 2001
Class A C S I N T Shares | Janus Henderson European Focus Fund | Return Before Taxes | Class T
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	18.36%
5 Years	rr_AverageAnnualReturnYear05	14.53%
10 Years	rr_AverageAnnualReturnYear10	4.11%
Since Inception	rr_AverageAnnualReturnSinceInception	11.34%
Inception Date	rr_AverageAnnualReturnInceptionDate	Aug. 31, 2001
Class A C S I N T Shares | Janus Henderson European Focus Fund | Return After Taxes on Distributions | Class A
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	10.81%	[2]
5 Years	rr_AverageAnnualReturnYear05	12.89%	[2]
10 Years	rr_AverageAnnualReturnYear10	3.19%	[2]
Since Inception	rr_AverageAnnualReturnSinceInception	10.23%	[2]
Inception Date	rr_AverageAnnualReturnInceptionDate	Aug. 31, 2001	[2]
Class A C S I N T Shares | Janus Henderson European Focus Fund | Return After Taxes on Distributions and Sale of Fund Shares | Class A
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	7.12%	[2]
5 Years	rr_AverageAnnualReturnYear05	10.60%	[2]
10 Years	rr_AverageAnnualReturnYear10	2.76%	[2]
Since Inception	rr_AverageAnnualReturnSinceInception	9.47%	[2]
Inception Date	rr_AverageAnnualReturnInceptionDate	Aug. 31, 2001	[2]
Class A C S I N T Shares | Janus Henderson European Focus Fund | MSCI Europe Index (reflects no deduction for expenses, fees, or taxes, except foreign withholding taxes) | Class A
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	19.89%
5 Years	rr_AverageAnnualReturnYear05	9.09%
10 Years	rr_AverageAnnualReturnYear10	4.13%
Since Inception	rr_AverageAnnualReturnSinceInception	5.62%
Class A C S I N T Shares | Janus Henderson European Focus Fund | MSCI Europe Index (reflects no deduction for expenses, fees, or taxes, except foreign withholding taxes) | Class C
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	19.89%
5 Years	rr_AverageAnnualReturnYear05	9.09%
10 Years	rr_AverageAnnualReturnYear10	4.13%
Since Inception	rr_AverageAnnualReturnSinceInception	5.62%
Class A C S I N T Shares | Janus Henderson European Focus Fund | MSCI Europe Index (reflects no deduction for expenses, fees, or taxes, except foreign withholding taxes) | Class S
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	19.89%
5 Years	rr_AverageAnnualReturnYear05	9.09%
10 Years	rr_AverageAnnualReturnYear10	4.13%
Since Inception	rr_AverageAnnualReturnSinceInception	5.62%
Class A C S I N T Shares | Janus Henderson European Focus Fund | MSCI Europe Index (reflects no deduction for expenses, fees, or taxes, except foreign withholding taxes) | Class I
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	19.89%
5 Years	rr_AverageAnnualReturnYear05	9.09%
10 Years	rr_AverageAnnualReturnYear10	4.13%
Since Inception	rr_AverageAnnualReturnSinceInception	5.62%
Class A C S I N T Shares | Janus Henderson European Focus Fund | MSCI Europe Index (reflects no deduction for expenses, fees, or taxes, except foreign withholding taxes) | Class N
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	19.89%
5 Years	rr_AverageAnnualReturnYear05	9.09%
10 Years	rr_AverageAnnualReturnYear10	4.13%
Since Inception	rr_AverageAnnualReturnSinceInception	5.62%
Class A C S I N T Shares | Janus Henderson European Focus Fund | MSCI Europe Index (reflects no deduction for expenses, fees, or taxes, except foreign withholding taxes) | Class T
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	19.89%
5 Years	rr_AverageAnnualReturnYear05	9.09%
10 Years	rr_AverageAnnualReturnYear10	4.13%
Since Inception	rr_AverageAnnualReturnSinceInception	5.62%

[1] The Adviser has contractually agreed to waive its investment advisory fee and/or reimburse operating expenses to the extent that the Fund’s total annual fund operating expenses (excluding the fees payable pursuant to a Rule 12b-1 plan, shareholder servicing fees, such as transfer agency fees (including out-of-pocket costs), administrative services fees and any networking/omnibus fees payable by any share class, brokerage commissions, interest, dividends, taxes, acquired fund fees and expenses, and extraordinary expenses) exceed 0.96% for at least a one-year period commencing on January 26, 2024. This contractual waiver may be terminated or modified only at the discretion of the Board of Trustees.

[2] Fund returns calculated assuming maximum permitted sales loads.

[3] The one year return is calculated to include the contingent deferred sales charge.