Label	Element	Value
Risk Return Abstract	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	JANUS INVESTMENT FUND
Prospectus Date	rr_ProspectusDate	Jan. 28, 2022
Class D 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:0.0%;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:0.0%;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 and hold Shares of the Fund.
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 77% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	77.00%
Expense Example [Heading]	rr_ExpenseExampleHeading	<span style="color:#000000;font-family:Times New Roman;font-size:9.50pt;font-weight:bold;margin-left:3pt;">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, reinvest all dividends and distributions, and then redeem all of your Shares at the end of each period. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions 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.
Strategy [Heading]	rr_StrategyHeading	<span style="color:#FFFFFF;font-family:Times New Roman;font-size:10.45pt;font-weight:bold;margin-left:0.0%;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. Such companies may include those in the real estate industry or real estate-related industries. 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 the portfolio managers, 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 a company 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. The Fund may also invest in companies or issuers that are economically tied to emerging markets.In choosing investments for the Fund, the portfolio managers apply a “bottom up” approach that utilizes the portfolio managers’ knowledge of issuers in the Americas and the Asia Pacific, European, and Latin American regions. Factors that the portfolio managers consider in their fundamental analysis include 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.The portfolio managers may sell a stock if they believe that its future prospects have been accurately reflected in the market price or if their original investment thesis has changed.The Fund may lend portfolio securities 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:0.0%;text-transform:uppercase;">Principal investment risks</span>
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors interested in investments focused in the real estate industry or real estate-related industries, including common stocks. Common stocks tend to be more volatile than many other investment choices. The principal risks associated with investing in the Fund are set forth below.Real Estate Securities Risk. An investment in the Fund may be subject to many of the same risks as a direct investment in real estate. The value of real estate-related companies’ securities is sensitive to changes in real estate values and rental income, property taxes, interest rates, tax and regulatory requirements, supply and demand, and the management skill and creditworthiness of the company. Investments in REITs involve the same risks as other real estate investments. REITs and REIT-like entities may have relatively small market capitalizations, which can increase the relative volatility of the market price for their securities. 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.Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the portfolio managers’ belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. 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. 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, social unrest, natural disasters, epidemics and pandemics, including COVID-19) adversely interrupt the global economy and financial markets.Concentration Risk. Since the Fund concentrates its assets in the real estate or real estate-related industry, an investment in the Fund will be closely linked to performance of the real estate markets. As a result, the Fund may be subject to greater risks and its net asset value may fluctuate more than a fund that does not concentrate its investments.Foreign Exposure Risk. The Fund normally has significant exposure to foreign markets as a result of its investments in foreign securities, including investments in emerging markets, which can be more volatile than the U.S. markets. As a result, its 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. The Fund’s investments in emerging market countries, if any, may involve risks greater than, or in addition to, the risks of investing in more developed countries.Portfolio Management Risk. The Fund is an actively managed investment portfolio and is therefore subject to the risk that the investment strategies employed for the Fund may fail to produce the intended results. The Fund may underperform its benchmark index or other mutual funds with similar investment objectives.Initial Public Offering and Secondary Offering Risk. Initial public offering (“IPO”) 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. Although IPOs and secondary offerings may have had a positive impact on the Fund’s performance in the past, there can be no assurance that the Fund will identify favorable IPO and secondary offering investment opportunities in the future. In addition, as the Fund increases in size, the impact of IPOs and secondary offerings on the Fund’s performance will generally decrease.Emerging Markets Risk. The risks of foreign investing are heightened when investing in emerging markets. Emerging marketsecurities involve a number of additional risks, which may result from less government supervision and regulation of business and industry practices (including the potential lack of strict finance and accounting controls and standards), stock exchanges, brokers, and listed companies. Information about emerging market companies, including financial information, may be less available or reliable and the Adviser’s ability to conduct due diligence with respect to such companies may be limited. Accordingly, these investments may be potentially more volatile in price and less liquid than investments in developed securities markets, resulting in greater risk to investors. There is a risk in developing countries that a current or future economic or political crisis could lead to price controls, forced mergers of companies, expropriation or confiscatory taxation, imposition or enforcement of foreign ownership limits, seizure, nationalization, sanctions or imposition of restrictions by various governmental entities on investment and trading, or creation of government monopolies, any of which may have a detrimental effect on the Fund’s investments. In addition, the taxation systems at the federal, regional, and local levels in developing or emerging market countries may be less transparent, inconsistently enforced, and subject to change. Emerging markets may be subject to a higher degree of corruption and fraud than developed markets and financial institutions and transaction counterparties may have less financial sophistication, creditworthiness, and/or resources than participants in developed markets. In addition, the Fund’s investments may be denominated in foreign currencies and therefore, changes in the value of a country’s currency compared to the U.S. dollar may affect the value of the Fund’s investments. To the extent that the Fund invests a significant portion of its assets in the securities of emerging markets issuers in or companies of a single country or region, it is more likely to be impacted by events or conditions affecting that country or region, which could have a negative impact on the Fund’s performance. As of September 30, 2021, approximately 6.1% of the Fund’s investments were in emerging markets (i.e., countries included in the MSCI Emerging Markets Indexsm).Securities Lending Risk. The Fund may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions. 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.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.
Risk Lose Money [Text]	rr_RiskLoseMoney	<span style="font-family:Times New Roman;font-size:9.50pt;">The biggest risk is that the Fund’s returns will vary, and you could lose money.</span>
Risk Not Insured Depository Institution [Text]	rr_RiskNotInsuredDepositoryInstitution	<span style="color:#000000;font-family:Times New Roman;font-size:9.50pt;font-style:italic;">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.</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:0.0%;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 D Shares of the Fund commenced operations on February 16, 2010. The performance shown for Class D Shares for periods prior to February 16, 2010, reflects the performance of the Fund’s Class I Shares calculated using the fees and expenses of Class D Shares, without the effect of any fee and expense limitations or waivers. If Class D Shares of the Fund had been available during periods prior to February 16, 2010, the performance shown may have been different. The performance shown for the periods following the Fund’s commencement of Class D Shares reflects the fees and expenses of Class D Shares, 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 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 at janushenderson.com/allfunds or by calling 1-800-525-3713.
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>
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 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;">1-800-525-3713</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/allfunds</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 D Shares (calendar year-end)
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	Best Quarter:1st Quarter 201216.13%Worst Quarter:1st Quarter 2020– 21.18%
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Returns (periods ended 12/31/21)
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 after-tax returns depend on your individual tax </span><span style="color:#000000;font-family:Times New Roman;font-size:9.50pt;">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 Narrative	rr_PerformanceTableNarrativeTextBlock	The Fund’s primary benchmark index is the FTSE EPRA Nareit Global Index. The primary index is used to calculate the Fund’s performance fee adjustment. 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 D Shares for the periods following February 16, 2010; and for the Fund’s Class I Shares for the periods prior to February 16, 2010. If Class D Shares of the Fund had been available during these earlier periods, distributions may have been different and thus, after-tax returns may have been different from those shown. 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.
Performance Table Closing [Text Block]	rr_PerformanceTableClosingTextBlock	Updated performance information is available at janushenderson.com/allfunds or by calling 1-800-525-3713.
Class D Shares | Janus Henderson Global Real Estate Fund | Class D
Risk Return Abstract	rr_RiskReturnAbstract
Management Fees	rr_ManagementFeesOverAssets	0.84%	[1]
Other Expenses	rr_OtherExpensesOverAssets	0.22%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.06%
1 Year	rr_ExpenseExampleYear01	$ 108
3 Years	rr_ExpenseExampleYear03	337
5 Years	rr_ExpenseExampleYear05	585
10 Years	rr_ExpenseExampleYear10	$ 1,294
2012	rr_AnnualReturn2012	32.10%
2013	rr_AnnualReturn2013	6.51%
2014	rr_AnnualReturn2014	14.10%
2015	rr_AnnualReturn2015	(2.04%)
2016	rr_AnnualReturn2016	3.41%
2017	rr_AnnualReturn2017	17.63%
2018	rr_AnnualReturn2018	(3.33%)
2019	rr_AnnualReturn2019	30.88%
2020	rr_AnnualReturn2020	1.31%
2021	rr_AnnualReturn2021	22.34%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	Best Quarter
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Mar. 31, 2012
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	16.13%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	Worst Quarter
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Mar. 31, 2020
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(21.18%)
Class D Shares | Janus Henderson Global Real Estate Fund | Return Before Taxes | Class D
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	22.34%
5 Years	rr_AverageAnnualReturnYear05	13.03%
10 Years	rr_AverageAnnualReturnYear10	11.61%
Since Inception	rr_AverageAnnualReturnSinceInception	6.55%
Inception Date	rr_AverageAnnualReturnInceptionDate	Nov. 28, 2007
Class D Shares | Janus Henderson Global Real Estate Fund | Return After Taxes on Distributions | Class D
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	20.15%
5 Years	rr_AverageAnnualReturnYear05	11.41%
10 Years	rr_AverageAnnualReturnYear10	10.00%
Since Inception	rr_AverageAnnualReturnSinceInception	5.27%
Inception Date	rr_AverageAnnualReturnInceptionDate	Nov. 28, 2007
Class D Shares | Janus Henderson Global Real Estate Fund | Return After Taxes on Distributions and Sale of Fund Shares | Class D
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	13.82%
5 Years	rr_AverageAnnualReturnYear05	9.71%
10 Years	rr_AverageAnnualReturnYear10	8.87%
Since Inception	rr_AverageAnnualReturnSinceInception	4.74%
Inception Date	rr_AverageAnnualReturnInceptionDate	Nov. 28, 2007
Class D Shares | Janus Henderson Global Real Estate Fund | FTSE EPRA Nareit Global Index (reflects no deduction for expenses, fees, or taxes)
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	23.04%
5 Years	rr_AverageAnnualReturnYear05	8.45%
10 Years	rr_AverageAnnualReturnYear10	9.06%
Since Inception	rr_AverageAnnualReturnSinceInception	4.48%
Class D 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)
Risk Return Abstract	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	22.01%
5 Years	rr_AverageAnnualReturnYear05	7.52%
10 Years	rr_AverageAnnualReturnYear10	8.19%
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.