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 Global Real Estate 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 Global Real Estate 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 Global Real Estate Fund seeks total return through a combination of capital appreciation and current income.
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)
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 66% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	66.00%
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="color:#000000;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="color:#000000;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 remain the same. Class C Shares automatically convert to Class A Shares 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 real estate-related companies. These securities may include common stocks, preferred stocks, and other equity securities, including, but not limited to, real estate investment trusts (“REITs”) and similar REIT-like entities, such as foreign entities that have REIT characteristics and real estate operating companies (“REOCs”). The Fund may invest in shares of companies through initial public offerings and secondary offerings.As a fundamental policy, the Fund will concentrate 25% or more of its net assets in securities of issuers in real estate or real estate-related industries. The Fund’s investment in companies engaged in businesses outside the real estate industry which possess significant real estate holdings will be deemed to be in the real estate industry for purposes of the Fund’s investment objective and its policy on industry concentration.Real estate-related industries are comprised of companies that, in the opinion of portfolio management, at the time of investment, generally (i) derive at least 50% of their revenue from ownership, construction, extraction, financing, management, operation, sales or development of real estate, or from businesses which have a clear relationship to these activities; (ii) have at least 50% of their assets in real estate; or (iii) have more than 50% of their net asset value accounted for by real estate.A REIT is an entity dedicated to owning, and usually operating, income-producing real estate, or to financing real estate. REITs pool investors’ funds for investment primarily in income-producing real estate or real estate-related loans or interests. Under the Internal Revenue Code of 1986, as amended (the “Internal Revenue Code”), a REIT is not taxed on income it distributes to its shareholders if it complies with several requirements relating to its organization, ownership, assets and income, and a requirement that it generally distributes to its shareholders at least 90% of its taxable income (other than net capital gains) for each taxable year. A REOC is a publicly traded corporation that is engaged in real estate businesses, but that has not taken (or is not eligible for) the REIT tax election and therefore does not have a requirement to distribute any of its taxable income.The Fund also invests in non-U.S. real estate and real estate-related companies. The Fund expects under normal market conditions to maintain investments in issuers that are economically tied to different countries throughout the world, including the United States. An issuer is deemed to be economically tied to a country or countries if one or more of the following tests are met: (i) the issuer is organized in, or its primary business office or principal trading market of its equity is located in, the country; (ii) a majority of the issuer’s revenues are derived from one or more countries; or (iii) a majority of the issuer’s assets are located in one or more countries.In choosing investments for the Fund, portfolio management applies a “bottom up” approach that utilizes portfolio management’s knowledge of issuers in the Americas and the Asia Pacific, European, and Latin American regions. Factors that portfolio management considers in their fundamental analysis includes a company’s balance sheet, valuation, strength of management, property markets and sectors, economics, and capital markets in seeking to determine the appropriate risk-adjusted return.To identify the universe of investible securities for the Fund, portfolio management also applies negative screens, which incorporate third-party inputs, to seek to avoid investing in (i) REITs that are involved in the operation of prison facilities and (ii) issuers that are United Nations Global Compact violators. At portfolio management’s discretion, the Fund will engage with companies regarding the adoption, or commitment to adopt, emission reduction targets. Under normal circumstances, the Fund will invest at least 10% of its assets in companies that have committed to such targets.Portfolio management will generally consider selling a security if it believes that its future prospects have been accurately reflected in the market price, the company no longer meets the social or environmental criteria noted above, or if their original investment thesis has changed.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.
Strategy Portfolio Concentration [Text]	rr_StrategyPortfolioConcentration	<span style="color:#000000;font-family:Times New Roman;font-size:9.50pt;">As a fundamental policy, the Fund will concentrate 25% or more of its net assets in securities of issuers in real estate or real estate-related industries.</span>
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. Class I Shares, Class A Shares, Class C Shares, and Class S Shares of the Fund commenced operations on July 6, 2009, after the reorganization of each corresponding class of shares of Janus Adviser Global Real Estate Fund (the “JAD predecessor fund”) into each respective share class of the Fund. Class T Shares of the Fund commenced operations on July 6, 2009. Class N Shares of the Fund commenced operations on January 26, 2018.•The performance shown for Class I Shares, Class A Shares, Class C Shares, and Class S Shares for periods prior to July 6, 2009, reflects the historical performance of the JAD predecessor fund’s Class I Shares, Class A Shares, Class C Shares, and Class S Shares prior to the reorganization, calculated using the fees and expenses of each respective share class of the JAD predecessor fund, net of any applicable fee and expense limitations or waivers.•The performance shown for Class T Shares for periods prior to July 6, 2009, reflects the historical performance of the JAD predecessor fund’s Class I Shares prior to the reorganization, calculated using the fees and expenses of Class T Shares, without the effect of any fee and expense limitations or waivers.•The performance shown for Class N Shares for periods prior to January 26, 2018, reflects the performance of the Fund’s Class I Shares from July 6, 2009, calculated using the fees and expenses of Class I Shares, net of any applicable fee and expense limitations or waivers. The performance shown for Class N Shares for periods prior to July 6, 2009, reflects the historical performance of the JAD predecessor fund’s Class I Shares, calculated using the fees and expenses of Class I Shares of the JAD predecessor fund, net of any applicable fee and expense limitations or waivers.If Class T Shares of the Fund had been available during periods prior to July 6, 2009 or Class N Shares of the Fund had been available during periods prior to January 26, 2018, the performance shown may have been different. The performance shown for periods following the Fund’s commencement of Class I Shares, Class A Shares, Class C Shares, Class S Shares, Class N Shares, and Class T Shares reflects the fees and expenses of each respective share class, net of any applicable fee and expense limitations or waivers.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 broad-based securities market indices. 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 past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available atjanushenderson.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 broad-based securities market indices. 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 broad-based securities market indices. 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 past performance (before and after taxes) does not necessarily indicate how it will perform in the future.</span>
Bar Chart [Heading]	rr_BarChartHeading	Annual Total Returns for Class I 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:1st Quarter 201915.90%Worst Quarter:1st Quarter 2020– 21.12%
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 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 </span><span style="color:#000000;font-family:Times New Roman;font-size:9.50pt;">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.</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 I Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class I 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 FTSE EPRA Nareit Global Index. The Fund also compares its performance to the FTSE EPRA Nareit Global Net Index (the “Net Index”). Both indices are composed of the same holdings. However, the FTSE EPRA Nareit Global Index reflects no deduction for foreign withholding taxes, whereas the Net Index reflects deduction for such taxes. The indices are described below.•The FTSE EPRA Nareit Global Index and the Net Index are global market capitalization-weighted indices composed of listed real estate companies and real estate investment trusts in both developed and emerging market countries.After-tax returns are calculated using distributions for the Fund’s Class I Shares for the periods following July 6, 2009; and for the JAD Predecessor Fund’s Class I Shares for the periods prior to July 6, 2009. 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 I Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class I 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 atjanushenderson.com/performance or by calling 1-877-335-2687.
Class A C S I N T Shares | Janus Henderson Global Real Estate 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 Global Real Estate 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 Global Real Estate Fund | Industry and Sector Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	Industry and Sector Risk. The Fund may have a significant portion of its assets invested in securities of companies conducting similar business or businesses within the same economic sector. Companies in the same industry or economic sector may be similarly affected by economic or market events, making the Fund more vulnerable to unfavorable developments than funds that invest more broadly. As the Fund’s portfolio becomes more concentrated, the Fund is less able to spread risk and potentially reduce the risk of loss and volatility. In addition, the Fund may be overweight or underweight in certain industries or sectors relative to its benchmark index, which may cause the Fund’s performance to be more or less sensitive to developments affecting those sectors.
Class A C S I N T Shares | Janus Henderson Global Real Estate Fund | Real Estate Sector Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	•Real Estate and Real Estate-Related Industries Risk. Investments in securities of real-estate related companies are subject to the risks associated with fluctuations in the value of the underlying properties; defaults by borrowers or tenants; market saturation; changes in general and local economic conditions; decreases in market rates for rents; changes in the availability, cost, and terms of mortgage funds; increased competition, property taxes, capital expenditures, or operating expenses; and other economic, political, or regulatory occurrences, including the impact of changes in environmental laws. In addition, a REIT could fail to qualify for tax-free pass-through of its income under the Internal Revenue Code of 1986, as amended, or fail to maintain its exemption from registration under the Investment Company Act of 1940, as amended, which could produce adverse economic consequences for the REIT and its investors, including the Fund. Dividends received by the Fund from a REIT generally will not constitute qualified dividend income. The real estate industry is particularly sensitive to economic downturns and changes in interest rates. The ability to trade companies operating in real estate development and operations in the secondary market can be more limited compared to other equity investments, and certain REITs and REIT-like entities have relatively small market capitalizations, which can increase the volatility of the market price for their securities.
Class A C S I N T Shares | Janus Henderson Global Real Estate 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 Global Real Estate 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 Global Real Estate 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 Global Real Estate Fund | ESG Investment Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	ESG Investment Risk. Because the Fund considers environmental, social, and governance (“ESG”) factors in selecting securities, the Fund may perform differently than funds that do not consider ESG factors. Due to the ESG considerations and exclusionary criteria employed by the Fund, the Fund may not be invested in certain issuers within the real estate industry or real estate-related industries, and therefore may have lower performance than portfolios that do not apply similar criteria.ESG-related information provided by issuers and third parties, which portfolio management may utilize, continues to develop, and may be incomplete, inaccurate, use different methodologies, or be applied differently across companies and industries. Further, the regulatory landscape for ESG investing in the United States is still developing and future rules and regulations may require the Fund to modify or alter its investment process. Similarly, government policies incentivizing companies to consider their environmental or social practices may fall out of favor, which could potentially limit the Fund’s investment universe. There is also a risk that the issuers identified through the investment process employed by the Fund may fail to adhere to positive environmental or social practices, which may result in selling a security when it might otherwise be disadvantageous to do so.
Class A C S I N T Shares | Janus Henderson Global Real Estate Fund | Initial Public Offering and Secondary Offering Risk [Member]
Risk Return Abstract	rr_RiskReturnAbstract
Risk [Text Block]	rr_RiskTextBlock	Initial Public Offering and Secondary Offering Risk. Initial public offerings (“IPOs”) and secondary offering shares frequently are volatile in price due to the absence of a prior public market, the small number of shares available for trading, and limited information about the issuer. Therefore, the Fund may hold IPO and secondary offering shares for a very short period of time. This may increase the portfolio turnover rate of the Fund and may lead to increased expenses for the Fund, such as commissions and transaction costs. There can be no assurance that the Fund will identify favorable IPO and secondary offering investment opportunities.
Class A C S I N T Shares | Janus Henderson Global Real Estate 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 Global Real Estate 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	0.77%	[1]
Distribution/Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses	rr_OtherExpensesOverAssets	0.18%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.20%
1 Year	rr_ExpenseExampleYear01	$ 690
3 Years	rr_ExpenseExampleYear03	934
5 Years	rr_ExpenseExampleYear05	1,197
10 Years	rr_ExpenseExampleYear10	1,946
1 Year	rr_ExpenseExampleNoRedemptionYear01	690
3 Years	rr_ExpenseExampleNoRedemptionYear03	934
5 Years	rr_ExpenseExampleNoRedemptionYear05	1,197
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 1,946
Class A C S I N T Shares | Janus Henderson Global Real Estate 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	0.77%	[1]
Distribution/Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	1.00%
Other Expenses	rr_OtherExpensesOverAssets	0.26%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.03%
1 Year	rr_ExpenseExampleYear01	$ 306
3 Years	rr_ExpenseExampleYear03	637
5 Years	rr_ExpenseExampleYear05	1,093
10 Years	rr_ExpenseExampleYear10	2,145
1 Year	rr_ExpenseExampleNoRedemptionYear01	206
3 Years	rr_ExpenseExampleNoRedemptionYear03	637
5 Years	rr_ExpenseExampleNoRedemptionYear05	1,093
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 2,145
Class A C S I N T Shares | Janus Henderson Global Real Estate 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	0.77%	[1]
Distribution/Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	0.25%
Other Expenses	rr_OtherExpensesOverAssets	0.36%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.38%
1 Year	rr_ExpenseExampleYear01	$ 140
3 Years	rr_ExpenseExampleYear03	437
5 Years	rr_ExpenseExampleYear05	755
10 Years	rr_ExpenseExampleYear10	1,657
1 Year	rr_ExpenseExampleNoRedemptionYear01	140
3 Years	rr_ExpenseExampleNoRedemptionYear03	437
5 Years	rr_ExpenseExampleNoRedemptionYear05	755
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 1,657
Class A C S I N T Shares | Janus Henderson Global Real Estate 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	0.77%	[1]
Distribution/Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.20%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.97%
1 Year	rr_ExpenseExampleYear01	$ 99
3 Years	rr_ExpenseExampleYear03	309
5 Years	rr_ExpenseExampleYear05	536
10 Years	rr_ExpenseExampleYear10	1,190
1 Year	rr_ExpenseExampleNoRedemptionYear01	99
3 Years	rr_ExpenseExampleNoRedemptionYear03	309
5 Years	rr_ExpenseExampleNoRedemptionYear05	536
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 1,190
2014	rr_AnnualReturn2014	14.23%
2015	rr_AnnualReturn2015	(1.94%)
2016	rr_AnnualReturn2016	3.50%
2017	rr_AnnualReturn2017	17.72%
2018	rr_AnnualReturn2018	(3.13%)
2019	rr_AnnualReturn2019	30.88%
2020	rr_AnnualReturn2020	1.39%
2021	rr_AnnualReturn2021	22.40%
2022	rr_AnnualReturn2022	(25.23%)
2023	rr_AnnualReturn2023	7.59%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	Best Quarter
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Mar. 31, 2019
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	15.90%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	Worst Quarter
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Mar. 31, 2020
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(21.12%)
Class A C S I N T Shares | Janus Henderson Global Real Estate 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	0.77%	[1]
Distribution/Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.07%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.84%
1 Year	rr_ExpenseExampleYear01	$ 86
3 Years	rr_ExpenseExampleYear03	268
5 Years	rr_ExpenseExampleYear05	466
10 Years	rr_ExpenseExampleYear10	1,037
1 Year	rr_ExpenseExampleNoRedemptionYear01	86
3 Years	rr_ExpenseExampleNoRedemptionYear03	268
5 Years	rr_ExpenseExampleNoRedemptionYear05	466
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 1,037
Class A C S I N T Shares | Janus Henderson Global Real Estate 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	0.77%	[1]
Distribution/Service (12b-1) Fees	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.33%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.10%
1 Year	rr_ExpenseExampleYear01	$ 112
3 Years	rr_ExpenseExampleYear03	350
5 Years	rr_ExpenseExampleYear05	606
10 Years	rr_ExpenseExampleYear10	1,340
1 Year	rr_ExpenseExampleNoRedemptionYear01	112
3 Years	rr_ExpenseExampleNoRedemptionYear03	350
5 Years	rr_ExpenseExampleNoRedemptionYear05	606
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 1,340
Class A C S I N T Shares | Janus Henderson Global Real Estate Fund | Return Before Taxes | Class A
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	1.20%	[2]
5 Years	rr_AverageAnnualReturnYear05	4.02%	[2]
10 Years	rr_AverageAnnualReturnYear10	4.73%	[2]
Since Inception	rr_AverageAnnualReturnSinceInception	4.32%	[2]
Inception Date	rr_AverageAnnualReturnInceptionDate	Nov. 28, 2007	[2]
Class A C S I N T Shares | Janus Henderson Global Real Estate Fund | Return Before Taxes | Class C
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	5.51%	[3]
5 Years	rr_AverageAnnualReturnYear05	4.43%	[3]
10 Years	rr_AverageAnnualReturnYear10	4.54%	[3]
Since Inception	rr_AverageAnnualReturnSinceInception	3.95%	[3]
Inception Date	rr_AverageAnnualReturnInceptionDate	Nov. 28, 2007	[3]
Class A C S I N T Shares | Janus Henderson Global Real Estate Fund | Return Before Taxes | Class S
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	7.13%
5 Years	rr_AverageAnnualReturnYear05	5.04%
10 Years	rr_AverageAnnualReturnYear10	5.17%
Since Inception	rr_AverageAnnualReturnSinceInception	4.54%
Inception Date	rr_AverageAnnualReturnInceptionDate	Nov. 28, 2007
Class A C S I N T Shares | Janus Henderson Global Real Estate Fund | Return Before Taxes | Class I
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	7.59%
5 Years	rr_AverageAnnualReturnYear05	5.49%
10 Years	rr_AverageAnnualReturnYear10	5.62%
Since Inception	rr_AverageAnnualReturnSinceInception	4.97%
Inception Date	rr_AverageAnnualReturnInceptionDate	Nov. 28, 2007
Class A C S I N T Shares | Janus Henderson Global Real Estate Fund | Return Before Taxes | Class N
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	7.72%
5 Years	rr_AverageAnnualReturnYear05	5.60%
10 Years	rr_AverageAnnualReturnYear10	5.68%
Since Inception	rr_AverageAnnualReturnSinceInception	5.01%
Inception Date	rr_AverageAnnualReturnInceptionDate	Nov. 28, 2007
Class A C S I N T Shares | Janus Henderson Global Real Estate Fund | Return Before Taxes | Class T
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	7.45%
5 Years	rr_AverageAnnualReturnYear05	5.37%
10 Years	rr_AverageAnnualReturnYear10	5.47%
Since Inception	rr_AverageAnnualReturnSinceInception	4.48%
Inception Date	rr_AverageAnnualReturnInceptionDate	Nov. 28, 2007
Class A C S I N T Shares | Janus Henderson Global Real Estate Fund | Return After Taxes on Distributions | Class I
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	6.55%
5 Years	rr_AverageAnnualReturnYear05	4.37%
10 Years	rr_AverageAnnualReturnYear10	4.19%
Since Inception	rr_AverageAnnualReturnSinceInception	3.75%
Inception Date	rr_AverageAnnualReturnInceptionDate	Nov. 28, 2007
Class A C S I N T Shares | Janus Henderson Global Real Estate Fund | Return After Taxes on Distributions and Sale of Fund Shares | Class I
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	4.64%
5 Years	rr_AverageAnnualReturnYear05	3.99%
10 Years	rr_AverageAnnualReturnYear10	3.94%
Since Inception	rr_AverageAnnualReturnSinceInception	3.55%
Inception Date	rr_AverageAnnualReturnInceptionDate	Nov. 28, 2007
Class A C S I N T Shares | Janus Henderson Global Real Estate Fund | FTSE EPRA Nareit Global Index (reflects no deduction for expenses, fees, or taxes) | Class A
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	9.78%
5 Years	rr_AverageAnnualReturnYear05	2.99%
10 Years	rr_AverageAnnualReturnYear10	4.17%
Since Inception	rr_AverageAnnualReturnSinceInception	2.79%
Class A C S I N T Shares | Janus Henderson Global Real Estate Fund | FTSE EPRA Nareit Global Index (reflects no deduction for expenses, fees, or taxes) | Class C
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	9.78%
5 Years	rr_AverageAnnualReturnYear05	2.99%
10 Years	rr_AverageAnnualReturnYear10	4.17%
Since Inception	rr_AverageAnnualReturnSinceInception	2.79%
Class A C S I N T Shares | Janus Henderson Global Real Estate Fund | FTSE EPRA Nareit Global Index (reflects no deduction for expenses, fees, or taxes) | Class S
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	9.78%
5 Years	rr_AverageAnnualReturnYear05	2.99%
10 Years	rr_AverageAnnualReturnYear10	4.17%
Since Inception	rr_AverageAnnualReturnSinceInception	2.79%
Class A C S I N T Shares | Janus Henderson Global Real Estate Fund | FTSE EPRA Nareit Global Index (reflects no deduction for expenses, fees, or taxes) | Class I
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	9.78%
5 Years	rr_AverageAnnualReturnYear05	2.99%
10 Years	rr_AverageAnnualReturnYear10	4.17%
Since Inception	rr_AverageAnnualReturnSinceInception	2.79%
Class A C S I N T Shares | Janus Henderson Global Real Estate Fund | FTSE EPRA Nareit Global Index (reflects no deduction for expenses, fees, or taxes) | Class N
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	9.78%
5 Years	rr_AverageAnnualReturnYear05	2.99%
10 Years	rr_AverageAnnualReturnYear10	4.17%
Since Inception	rr_AverageAnnualReturnSinceInception	2.79%
Class A C S I N T Shares | Janus Henderson Global Real Estate Fund | FTSE EPRA Nareit Global Index (reflects no deduction for expenses, fees, or taxes) | Class T
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	9.78%
5 Years	rr_AverageAnnualReturnYear05	2.99%
10 Years	rr_AverageAnnualReturnYear10	4.17%
Since Inception	rr_AverageAnnualReturnSinceInception	2.79%
Class A C S I N T Shares | Janus Henderson Global Real Estate Fund | FTSE EPRA Nareit Global Net Index (reflects no deduction for expenses, fees, or taxes, except foreign withholding taxes) | Class A
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	8.67%
5 Years	rr_AverageAnnualReturnYear05	2.07%
10 Years	rr_AverageAnnualReturnYear10	3.28%
Since Inception	rr_AverageAnnualReturnSinceInception
Class A C S I N T Shares | Janus Henderson Global Real Estate Fund | FTSE EPRA Nareit Global Net Index (reflects no deduction for expenses, fees, or taxes, except foreign withholding taxes) | Class C
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	8.67%
5 Years	rr_AverageAnnualReturnYear05	2.07%
10 Years	rr_AverageAnnualReturnYear10	3.28%
Since Inception	rr_AverageAnnualReturnSinceInception
Class A C S I N T Shares | Janus Henderson Global Real Estate Fund | FTSE EPRA Nareit Global Net Index (reflects no deduction for expenses, fees, or taxes, except foreign withholding taxes) | Class S
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	8.67%
5 Years	rr_AverageAnnualReturnYear05	2.07%
10 Years	rr_AverageAnnualReturnYear10	3.28%
Since Inception	rr_AverageAnnualReturnSinceInception
Class A C S I N T Shares | Janus Henderson Global Real Estate Fund | FTSE EPRA Nareit Global Net Index (reflects no deduction for expenses, fees, or taxes, except foreign withholding taxes) | Class I
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	8.67%
5 Years	rr_AverageAnnualReturnYear05	2.07%
10 Years	rr_AverageAnnualReturnYear10	3.28%
Since Inception	rr_AverageAnnualReturnSinceInception
Class A C S I N T Shares | Janus Henderson Global Real Estate Fund | FTSE EPRA Nareit Global Net Index (reflects no deduction for expenses, fees, or taxes, except foreign withholding taxes) | Class N
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	8.67%
5 Years	rr_AverageAnnualReturnYear05	2.07%
10 Years	rr_AverageAnnualReturnYear10	3.28%
Since Inception	rr_AverageAnnualReturnSinceInception
Class A C S I N T Shares | Janus Henderson Global Real Estate Fund | FTSE EPRA Nareit Global Net Index (reflects no deduction for expenses, fees, or taxes, except foreign withholding taxes) | Class T
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	8.67%
5 Years	rr_AverageAnnualReturnYear05	2.07%
10 Years	rr_AverageAnnualReturnYear10	3.28%
Since Inception	rr_AverageAnnualReturnSinceInception

[1] This fee may adjust up or down monthly based on the Fund’s performance relative to its benchmark index over the performance measurement period. For more information regarding performance-based advisory fees, refer to “Management Expenses” in the Fund’s Prospectus.

[2] Calculated assuming maximum permitted sales loads.

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