Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	JANUS INVESTMENT FUND
Prospectus Date	rr_ProspectusDate	Oct. 29, 2018
Janus Henderson All Asset Fund | Class D Shares
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	<b>FUND SUMMARY</b><br/><br/><b>Janus Henderson All Asset Fund</b>
Objective [Heading]	rr_ObjectiveHeading	<b>INVESTMENT OBJECTIVE </b>
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	Janus Henderson All Asset Fund seeks to provide total return by investing in a broad range of asset classes.
Expense [Heading]	rr_ExpenseHeading	<b>FEES AND EXPENSES OF THE FUND </b>
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	<b>ANNUAL FUND OPERATING EXPENSES</b><br/>(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	November 1, 2019
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	<b>Portfolio Turnover:</b>
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 16% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	16.00%
Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]	rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees	To the extent that the Fund invests in Acquired Funds, the Fund’s “Total Annual Fund Operating Expenses” may not correlate to the “Ratio of gross expenses to average net assets” presented in the Financial Highlights table because that ratio includes only the direct operating expenses incurred by the Fund, not the indirect costs of investing in Acquired Funds.
Expense Example [Heading]	rr_ExpenseExampleHeading	<b>EXAMPLE:</b>
Expense Example by Year [Heading]	rr_ExpenseExampleByYearHeading	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 without waivers remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	The following Example is based on expenses without waivers. 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	<b>PRINCIPAL INVESTMENT STRATEGIES </b>
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	The Fund seeks to achieve its investment objective by investing in a broad range of both traditional asset classes (such as equity and fixed-income investments) and alternative asset classes (such as real estate, commodities, currencies, private equity, and absolute return strategies). As part of this strategy, the Fund may hold cash and/or invest in money market instruments or cash equivalents. A flexible asset allocation approach will be utilized to invest across asset classes within a risk controlled framework. Asset allocation decisions will be driven by a process consisting of three key elements: asset selection, diversified portfolio construction and efficient implementation. Risk management is an integral part of decision making and is considered at all stages of the investment process. The Fund will vary its exposure to different asset classes and strategies over time in response to changing market and economic conditions. The level of exposure to various asset classes will be based on the adviser’s assessment of the asset’s potential return, associated volatility and correlation with other assets. The Fund may seek exposure to the asset classes described above by investing in other investment companies (“underlying funds”) or investment pools, by investing directly in securities and other investments or through the use of derivatives. Such investment companies and investment pools might include, for example, other open-end or closed-end investment companies (including investment companies that concentrate their investments in one or more industries or economic or market sectors), exchange-traded funds (“ETFs”, which are open-end investment companies whose shares may be bought or sold by investors in transactions on major stock exchanges), unit investment trusts, and domestic or foreign private investment pools (including investment companies not registered under the Investment Company Act of 1940, as amended (the “1940 Act”), such as “hedge funds”) or indexes of investment pools. Janus Capital may itself manage the Fund’s assets allocated to a particular asset class, either directly or through a mutual fund or other pooled vehicle managed by it, or it may invest the Fund’s assets in other investment companies or private investment pools providing access to specialist management outside of the Janus Henderson Group organizations. The amount and type of the Fund’s investment in a particular asset class, and the amount invested in certain investment companies or investment pools, is limited by law and by tax considerations. Because it invests in other investment companies, the Fund is considered a “fund of funds.” The Fund’s investment exposure, either through direct investment or through the underlying funds, primarily includes the following types of securities and other financial instruments: Equity securities of U.S. and non-U.S. companies, including in emerging markets. Equity securities include common stocks, preferred stocks, convertible securities, depositary receipts, and equity interests in trusts, warrants to purchase equity securities, partnerships, and limited liability companies. The Fund may invest in equity securities in all capitalization ranges. Fixed-income securities of various types including U.S. government debt securities, U.S. investment grade corporate debt, high-yield bonds and other securities rated below investment grade (commonly referred to as “junk bonds”), mortgage-related and other asset-backed securities, foreign investment grade debt (including developed market government bonds), emerging market debt, international high-yield debt, convertible securities, senior loans and cash equivalents. The Fund may invest in fixed-income securities of varying maturities. Derivatives. The Fund and the underlying funds may engage in exchange-traded or over-the-counter derivative transactions to enhance total return, to gain or limit exposure to equity or credit markets, interest rates or currency exchange rates, and/or as a substitute for the purchase or sale of securities, currencies or certain asset classes directly. The Fund expects to use derivatives principally when seeking to gain or limit exposure to equity markets by using futures contracts on securities indices or by purchasing exchange-traded call or put options on equity indices futures contracts, to gain or limit currency exposure using forward foreign currency contracts, to obtain net long or net negative (short) exposures to selected interest rate, duration or credit risks using a combination of bond or interest rate futures contracts, options on bond or interest rate futures contracts, and interest rate, inflation rate and credit default swap agreements. However, the Fund may also purchase or sell other types of derivatives contracts. There is no stated limit on the Fund’s or its investment in the underlying funds’ use of derivatives. At times the Fund may hold a significant amount of cash, money market instruments (which may include investments in one or more money market funds or similar vehicles) or other high-quality, short-term instruments to cover obligations with respect to, or that may result from, the Fund’s investments in futures contracts or securities indices, forward foreign currency contracts, bond or interest rate future contracts or other derivatives. The Fund or an underlying fund may invest in commodity-related investments. The Fund may invest, without limitation, in securities denominated in foreign currencies and in U.S. dollar-denominated securities of foreign issuers. In addition, the Fund or an underlying fund may invest in securities issued by smaller companies and in less seasoned issuers, including through initial public offerings and private placements. The Fund or an underlying fund may also enter into repurchase agreements. The Trust has obtained an exemptive order that allows the Fund to invest in affiliated and unaffiliated investment companies (including registered open-end and closed-end management companies, business development companies, and registered unit investment trusts) in excess of the limits under the 1940 Act, subject to the conditions of the order. The Fund may invest without limitation in any affiliated Fund of the Trust (“Underlying Janus Henderson Funds” and together with unaffiliated underlying funds, “underlying funds”). In addition to investing in the Underlying Janus Henderson Funds, at the discretion of the adviser and without shareholder approval, the Fund may invest in additional series of the Trust created in the future.
Risk [Heading]	rr_RiskHeading	<b>PRINCIPAL INVESTMENT RISKS </b>
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 seeking a portfolio that includes a broad range of both traditional and alternative asset classes. Investments in a portfolio with common stock and alternative investment exposure tend to be more volatile than many other investment choices. Allocation Risk.  The Fund’s ability to achieve its investment objective depends largely upon the portfolio manager’s allocation of assets among the underlying funds and other securities. You could lose money on your investment in the Fund as a result of these allocations. The Fund will typically invest in a number of different underlying funds; however, to the extent that the Fund invests a significant portion of its assets in a single underlying fund, it will be more sensitive to the risks associated with that fund and any investments in which that fund focuses. Management Risk.  The underlying funds are actively managed investment portfolios and are therefore subject to the risk that the investment strategies employed for the underlying funds may fail to produce the intended results. As a result, the Fund may underperform its benchmark index or other mutual funds with similar investment objectives. Foreign Exposure Risk.  The Fund and certain underlying funds may have significant exposure to foreign markets, including emerging markets, as a result of their investments in foreign securities, which can be more volatile than the U.S. markets. As a result, the Fund’s or an underlying fund’s returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. A market swing in one or more countries or regions where an underlying fund has invested a significant amount of its assets may have a greater effect on an underlying fund’s performance than it would in a more geographically diversified portfolio. The Fund’s or an underlying fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries. Emerging Markets Risk.  The risks of foreign investing are heightened when investing in emerging markets. Emerging markets securities 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, making these investments potentially more volatile in price and less liquid than investments in developed securities markets, resulting in greater risk to investors. In addition, an underlying 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 an underlying fund’s investments. To the extent that an underlying 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. Some of the risks of investing directly in foreign and emerging market securities may be reduced when an underlying fund invests indirectly in foreign securities through various other investment vehicles including derivatives, which also involve other risks. Small-Sized Companies Risk.  The Fund’s or underlying funds’ investments in securities issued by small-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. Securities issued by small-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. Convertible Securities Risk.  The Fund or underlying funds may invest in securities that are convertible into preferred and common stocks, and thus, are subject to the risks of investments in both debt and equity securities. The market value of convertible securities tends to decline as interest rates increase and, conversely, tends to increase as interest rates decline. In addition, because of the conversion feature, the market value of convertible securities tends to vary with fluctuations in the market value of the underlying preferred and common stocks and, therefore, also will react to variations in the general market for equity securities. Warrants Risk.  The price, performance and liquidity of warrants to purchase equity securities are typically linked to the underlying stock. These instruments have many characteristics of convertible securities and, similarly, will react to variations in the general market for equity securities purchased by the Fund or underlying funds. Fixed-Income Securities Risk.  The Fund’s assets may be allocated to fixed-income securities through investments in underlying funds. Typically, the values of fixed-income securities change inversely with prevailing interest rates. Therefore, a fundamental risk of fixed-income securities is interest rate risk, which is the risk that the value of such securities will generally decline as prevailing interest rates rise, which may cause an underlying fund’s net asset value to likewise decrease. For example, while securities with longer maturities and durations tend to produce higher yields, they also tend to be more sensitive to changes in prevailing interest rates and are therefore more volatile than shorter-term securities and are subject to greater market fluctuations as a result of changes in interest rates. Further, during periods of very low or negative interest rates, an underlying fund may not be able to maintain positive returns. An underlying fund may be subject to heightened interest rate risk because the Federal Reserve has ended its monetary stimulus program known as quantitative easing and interest rates are near historically low levels. The Federal Reserve raised the federal funds rate several times in recent periods and has signaled additional increases in the near future. To the extent the Federal Reserve continues to raise rates, there is a risk that the fixed-income markets will experience increased volatility and that the liquidity of certain underlying fund investments may be reduced. These developments could cause the underlying fund’s net asset value to fluctuate or make it more difficult for the underlying fund to accurately value its securities. These developments or others also could cause an underlying fund to face increased shareholder redemptions, which may lead to increased portfolio turnover and transaction costs, or could force the underlying fund to liquidate investments at disadvantageous times or prices, therefore adversely affecting the underlying fund and the Fund as well as the value of your investment. The amount of assets deemed illiquid remaining within the underlying fund may also increase, making it more difficult to meet shareholder redemptions and further adversely affecting the value of the underlying fund and the Fund. How specific fixed-income securities may react to changes in interest rates will depend on the specific characteristics of each security. Fixed-income securities are also subject to credit risk, prepayment risk, valuation risk, extension risk, and liquidity risk. Credit risk is the risk that the credit strength of an issuer of a fixed-income security will weaken and/or that the issuer will be unable to make timely principal and interest payments and that the security may go into default. Prepayment risk is the risk that during periods of falling interest rates, certain fixed-income securities with higher interest rates, such as mortgage- and asset-backed securities, may be prepaid by their issuers thereby reducing the amount of interest payments. Valuation risk is the risk that one or more of the fixed-income securities in which an underlying fund invests are priced differently than the value realized upon such security’s sale. In times of market instability, valuation may be more difficult. Extension risk is the risk that borrowers may pay off their debt obligations more slowly in times of rising interest rates, which will lengthen the duration of the portfolio. Liquidity risk is the risk that fixed-income securities may be difficult or impossible to sell at the time that an underlying fund’s portfolio manager would like or at the price the portfolio manager believes the security is currently worth. High-Yield/High-Risk Bond Risk.  High-yield/high-risk bonds are considered speculative and may be more sensitive than other types of bonds to economic changes, political changes, or adverse developments specific to the company that issued the bond, which may adversely affect their value. Exchange-Traded and Mutual Funds Risk.  The Fund and certain underlying funds may invest in exchange-traded funds (“ETFs”) and mutual funds to gain exposure to a particular portion of the market. ETFs are typically open-end investment companies, which may seek to track the performance of a specific index or be actively managed. ETFs are traded on a national securities exchange at market prices that may vary from the net asset value of their underlying investments. Accordingly, there may be times when an ETF trades at a premium or discount. When the Fund or an underlying fund invests in an ETF or mutual fund, in addition to directly bearing the expenses associated with its own operations, it will bear a pro rata portion of the ETF’s or mutual fund’s expenses. The Fund and certain underlying funds are also subject to the risks associated with the securities in which the ETF or mutual fund invests. Affiliated Fund Risk.  Janus Capital has the authority to select and substitute underlying affiliated mutual funds. The fees paid to Janus Capital by some underlying affiliated mutual funds are generally higher than the fees paid by the Fund or other underlying affiliated mutual funds, which may create a conflict of interest when selecting underlying affiliated mutual funds and share classes for investment. Janus Capital, however, is a fiduciary to the Fund and is legally obligated to act in their best interest when selecting underlying affiliated mutual funds, without taking fees into consideration. Derivatives Risk.  Both the Fund and certain underlying funds may invest in derivatives. Derivatives can be highly volatile and involve risks in addition to the risks of the underlying referenced securities or asset. Gains or losses from a derivative investment can be substantially greater than the derivative’s original cost, and can therefore involve leverage. Leverage may cause the Fund or an underlying fund to be more volatile than if it had not used leverage. Derivatives can be complex instruments and may involve analysis that differs from that required for other investment types used by the Fund or an underlying fund. If the value of a derivative does not correlate well with the particular market or other asset class to which the derivative is intended to provide exposure, the derivative may not produce the anticipated result. Derivatives can also reduce the opportunity for gain or result in losses by offsetting positive returns in other investments. Derivatives can be less liquid than other types of investments and entail the risk that the counterparty will default on its payment obligations. If the counterparty to a derivative transaction defaults, the Fund or an underlying fund would risk the loss of the net amount of the payments that it contractually is entitled to receive. To the extent the Fund or an underlying fund enters into short derivative positions, the Fund or such underlying fund may be exposed to risks similar to those associated with short sales, including the risk that the Fund’s or such underlying fund’s losses are theoretically unlimited. Over-the-Counter Risk.  Securities traded in over-the-counter markets may trade in smaller volumes, and their prices may be more volatile, than securities principally traded on securities exchanges. Such securities may be less liquid than more widely traded securities. In addition, the prices of such securities may include an undisclosed dealer markup, which the Fund or an underlying fund pays as part of the purchase price. Leverage Risk.  Engaging in transactions using leverage or those having a leveraging effect subjects the Fund or an underlying fund to certain risks. Leverage can magnify the effect of any gains or losses, causing the Fund or an underlying fund to be more volatile than if it had not been leveraged. Certain commodity-linked derivatives may subject the Fund or an underlying fund to leveraged market exposure to commodities. In addition, the Fund’s or an underlying fund’s assets that are used as collateral to secure short sale transactions may decrease in value while the short positions are outstanding, which may force the Fund or the underlying fund to use its other assets to increase collateral. There is no assurance that a leveraging strategy will be successful. Real Estate Securities Risk.  To the extent an underlying fund holds equity and/or debt securities of real estate-related companies, the Fund may be affected by the risks associated with real estate investments. The value of securities of companies in real estate and real estate-related industries, including securities of real estate investment trusts (“REITs”), is sensitive to decreases in real estate values and rental income, property taxes, interest rates, tax and regulatory requirements, overbuilding/supply and demand, increased competition, local and general economic conditions, increases in operating costs, environmental liabilities, management skill in running a REIT, and the creditworthiness of the REIT. Mortgage- and Asset-Backed Securities Risk.  Mortgage- and asset-backed securities represent interests in “pools” of commercial or residential mortgages or other assets, including consumer loans or receivables. Mortgage- and asset-backed securities tend to be more sensitive to changes in interest rates than other types of debt securities. Investments in mortgage- and asset-backed securities are subject to both extension risk, where borrowers pay off their debt obligations more slowly in times of rising interest rates, and prepayment risk, where borrowers pay off their debt obligations sooner than expected in times of declining interest rates. These risks may reduce the returns of the Fund or an underlying fund. In addition, investments in mortgage- and asset-backed securities, including those comprised of subprime mortgages, may be subject to a higher degree of credit risk, valuation risk, and liquidity risk than various other types of fixed-income securities. Commodity-Linked Investments Risk.  The Fund or an underlying fund may invest, directly or indirectly, in various commodity-linked investments that provide exposure to the commodities markets. Such exposure may subject the Fund or an underlying fund to greater volatility than investments in traditional securities. The value of a given commodity-linked derivative investment typically is based upon the price movements of a physical commodity (such as heating oil, livestock, or agricultural products), a commodity futures contract or commodity index, or some other readily measurable economic variable. The value of commodity-linked derivative instruments may therefore be affected by changes in overall market movements, volatility of the underlying benchmark, changes in interest rates, or other factors affecting a particular industry or commodity such as drought, floods, weather, livestock disease, embargoes, tariffs, and international economic, political, and regulatory developments. Private Placements and Restricted Securities Risk.  Restricted securities are securities that cannot be offered for public resale unless registered under the applicable securities laws or that have a contractual restriction that prohibits or limits their resale. They may include private placement securities that have not been registered under the Securities Act of 1933, as amended, and are generally eligible for sale only to certain eligible investors. Restricted securities may not be listed on an exchange and may have no active trading market and therefore may be considered to be illiquid. Because there may be relatively few potential purchasers for such investments, especially under adverse market or economic conditions or in the event of adverse changes in the financial condition of the issuer, the Fund or an underlying fund could find it difficult to sell such securities when the Fund’s adviser or subadviser believes it advisable to do so or may be able to sell such securities only at prices lower than if such securities were more widely held. At times, it may also be difficult to determine the fair value of such securities for purposes of computing the net asset value of the Fund or an underlying fund. The sale of such investments may also be restricted under securities laws. Repurchase Agreements Risk.  Repurchase agreements may be viewed as loans made by the Fund or an underlying fund which are collateralized by the securities subject to repurchase. Investment return on such assets will depend on the counterparties’ willingness and ability to perform their obligations under the repurchase agreements. If the seller of a repurchase agreement defaults, the Fund or any underlying fund could realize a loss on the sale of the underlying security to the extent that the proceeds of sale including accrued interest are less than the resale price provided in the agreement including interest. Market Risk.  The Fund may allocate its assets to equity investments through investments in underlying funds. The value of an underlying 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 manager’s belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of an underlying 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. Geographic Concentration Risk.  Although the Fund does not focus its investments in a particular geographic region, the application of flexible asset allocation approach may result at times in the Fund’s investments being concentrated in a particular geographic region. To the extent the Fund or underlying funds invest a substantial amount of its or their assets in issuers located in a single country or region, the economic, political, regulatory or other developments or conditions within such country or region will generally have a greater effect on the Fund or underlying funds than they would on a more geographically diversified fund, which may result in greater losses and volatility. Liquidity Risk.  The Fund or an underlying fund may invest in securities or instruments that do not trade actively or in large volumes, and may make investments that are less liquid than other investments. Also, the Fund or an underlying fund may make investments that may become less liquid in response to market developments or adverse investor perceptions. Investments that are illiquid or that trade in lower volumes may be more difficult to value. When there is no willing buyer and investments cannot be readily sold at the desired time or price, the Fund or an underlying fund may have to accept a lower price or may not be able to sell the security or instrument at all. Investments in foreign securities, particularly those of issuers located in emerging market countries, tend to have greater exposure to liquidity risk than domestic securities. In unusual market conditions, even normally liquid securities may be affected by a degree of liquidity risk (i.e., if the number and capacity of traditional market participants is reduced). An inability to sell one or more portfolio positions can adversely affect the Fund’s or an underlying fund’s value or prevent the Fund or an underlying fund from being able to take advantage of other investment opportunities. For investments in fixed-income securities, such securities may be difficult or impossible to sell at the time that the portfolio manager would like or at the price the portfolio manager believes the security is currently worth. To the extent the Fund or an underlying fund invests in fixed-income securities in a particular industry or economic sector, its share values may fluctuate in response to events affecting that industry or sector. 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	The biggest risk is that the Fund’s returns will vary, and you could lose money.
Risk Not Insured Depository Institution [Text]	rr_RiskNotInsuredDepositoryInstitution	<i>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.</i>
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	<b>PERFORMANCE INFORMATION </b>
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 June 5, 2017. The performance shown for Class D Shares for periods prior to June 5, 2017, reflects the performance of Class I Shares of Henderson All Asset Fund (the “Predecessor Fund”), calculated using the estimated fees and expenses of Class D Shares, net of any applicable fee and expense limitations or waivers. 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. In connection with this reorganization, certain shareholders of the Predecessor Fund who held shares directly with the Predecessor Fund and not through an intermediary had the Class A Shares, Class C Shares, Class I Shares, and Class N Shares of the Fund received in the merger automatically exchanged for Class D Shares of the Fund following the merger. If Class D Shares of the Fund had been available during periods prior to June 5, 2017, the performance shown may have been different because the Fund and the Predecessor Fund have different expenses. 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 (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/allfunds or by calling 1-800-525-3713.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	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.<br/><br/>The bar chart depicts the change in performance from year to year during the periods indicated.
Performance Additional Market Index [Text]	rr_PerformanceAdditionalMarketIndex	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.
Performance Availability Phone [Text]	rr_PerformanceAvailabilityPhone	<i>1-800-525-3713</i>
Performance Availability Website Address [Text]	rr_PerformanceAvailabilityWebSiteAddress	<i>janushenderson.com/allfunds</i>
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	<i>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.</i>
Bar Chart [Heading]	rr_BarChartHeading	<b>Annual Total Returns for Class D Shares </b>(calendar year-end)
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	Best Quarter:  4th Quarter 2013  3.37%          Worst Quarter:  3rd Quarter 2015  – 4.64%
Year to Date Return, Label	rr_YearToDateReturnLabel	The Fund’s year-to-date return as of the calendar quarter ended September 30, 2018 was – 1.25%.
Performance Table Heading	rr_PerformanceTableHeading	<b>Average Annual Total Returns</b> (periods ended 12/31/17)
Performance Table Uses Highest Federal Rate	rr_PerformanceTableUsesHighestFederalRate	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.
Performance Table Not Relevant to Tax Deferred	rr_PerformanceTableNotRelevantToTaxDeferred	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-deferred account, such as a 401(k) plan or an IRA.
Performance Table Narrative	rr_PerformanceTableNarrativeTextBlock	The Fund’s primary benchmark index is the 3-month USD LIBOR. The Fund also compares its performance to the MSCI World IndexSM. The indices are described below. The 3-month USD LIBOR is a daily reference rate based on the interest rates at which banks offer to lend unsecured funds to other banks in the London wholesale money market (or interbank market). The MSCI World IndexSM is a free float-adjusted market capitalization weighted index that is designed to measure the equity market performance of developed market countries in North America, Europe, and the Asia/Pacific Region. After-tax returns are calculated using distributions for the Predecessor Fund’s Class I Shares for the period prior to June 5, 2017. If Class D 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-deferred 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.
Janus Henderson All Asset Fund | Class D Shares | Class D
Risk/Return:	rr_RiskReturnAbstract
Operating Expenses Column [Text]	rr_OperatingExpensesColumnName	Class D
Management Fees	rr_ManagementFeesOverAssets	0.40%
Other Expenses	rr_OtherExpensesOverAssets	0.58%
Acquired Fund Fees and Expenses	rr_AcquiredFundFeesAndExpensesOverAssets	0.53%	[1]
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.51%	[2]
Fee Waiver	rr_FeeWaiverOrReimbursementOverAssets	0.33%	[2]
Total Annual Fund Operating Expenses After Fee Waiver	rr_NetExpensesOverAssets	1.18%	[2]
Expense Example, By Year, Column [Text]	rr_ExpenseExampleByYearColumnName	Class D Shares
1 Year	rr_ExpenseExampleYear01	$ 154
3 Years	rr_ExpenseExampleYear03	477
5 Years	rr_ExpenseExampleYear05	824
10 Years	rr_ExpenseExampleYear10	$ 1,802
2013	rr_AnnualReturn2013	8.21%
2014	rr_AnnualReturn2014	1.34%
2015	rr_AnnualReturn2015	(1.89%)
2016	rr_AnnualReturn2016	4.31%
2017	rr_AnnualReturn2017	11.07%
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Sep. 30, 2018
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	(1.25%)
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	<b>Best Quarter:</b>
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Dec. 31, 2013
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	3.37%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	<b>Worst Quarter:</b>
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Sep. 30, 2015
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(4.64%)
Janus Henderson All Asset Fund | Class D Shares | Return Before Taxes | Class D
Risk/Return:	rr_RiskReturnAbstract
Average Annual Return, Column Name	rr_AverageAnnualReturnColumnName	Class D Shares
Label	rr_AverageAnnualReturnLabel	Return Before Taxes
1 Year	rr_AverageAnnualReturnYear01	11.07%
5 Years	rr_AverageAnnualReturnYear05	4.51%
Since Inception	rr_AverageAnnualReturnSinceInception	4.36%
Inception Date	rr_AverageAnnualReturnInceptionDate	Mar. 30, 2012
Janus Henderson All Asset Fund | Class D Shares | Return After Taxes on Distributions | Class D
Risk/Return:	rr_RiskReturnAbstract
Average Annual Return, Column Name	rr_AverageAnnualReturnColumnName	Class D Shares
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions
1 Year	rr_AverageAnnualReturnYear01	8.28%
5 Years	rr_AverageAnnualReturnYear05	3.05%
Since Inception	rr_AverageAnnualReturnSinceInception	3.02%
Inception Date	rr_AverageAnnualReturnInceptionDate	Mar. 30, 2012
Janus Henderson All Asset Fund | Class D Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class D
Risk/Return:	rr_RiskReturnAbstract
Average Annual Return, Column Name	rr_AverageAnnualReturnColumnName	Class D Shares
Label	rr_AverageAnnualReturnLabel	Return After Taxes on Distributions and Sale of Fund Shares
1 Year	rr_AverageAnnualReturnYear01	6.97%
5 Years	rr_AverageAnnualReturnYear05	2.98%
Since Inception	rr_AverageAnnualReturnSinceInception	2.92%
Inception Date	rr_AverageAnnualReturnInceptionDate	Mar. 30, 2012
Janus Henderson All Asset Fund | Class D Shares | 3-month USD LIBOR (reflects no deduction for expenses, fees, or taxes)
Risk/Return:	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	3-month USD LIBOR
1 Year	rr_AverageAnnualReturnYear01	1.11%
5 Years	rr_AverageAnnualReturnYear05	0.50%
Since Inception	rr_AverageAnnualReturnSinceInception	0.50%
Inception Date	rr_AverageAnnualReturnInceptionDate	Mar. 30, 2012
Janus Henderson All Asset Fund | Class D Shares | MSCI World Index℠ (reflects no deduction for expenses, fees, or taxes, except foreign withholding taxes)
Risk/Return:	rr_RiskReturnAbstract
Label	rr_AverageAnnualReturnLabel	MSCI World Index<SUP>SM</SUP>
1 Year	rr_AverageAnnualReturnYear01	22.40%
5 Years	rr_AverageAnnualReturnYear05	11.64%
Since Inception	rr_AverageAnnualReturnSinceInception	10.75%
Inception Date	rr_AverageAnnualReturnInceptionDate	Mar. 30, 2012

[1] “Acquired Fund” refers to any underlying fund (including, but not limited to, exchange-traded funds) in which a fund invests or has invested during the period. Acquired fund fees and expenses are indirect expenses a fund may incur as a result of investing in shares of an underlying fund. To the extent that the Fund invests in Acquired Funds, the Fund’s “Total Annual Fund Operating Expenses” may not correlate to the “Ratio of gross expenses to average net assets” presented in the Financial Highlights table because that ratio includes only the direct operating expenses incurred by the Fund, not the indirect costs of investing in Acquired Funds.

[2] Janus Capital 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 administrative services fees (including out-of-pocket costs), brokerage commissions, interest, dividends, taxes, acquired fund fees and expenses, and extraordinary expenses) exceed 0.51% until at least November 1, 2019. The contractual waiver may be terminated or modified prior to this date only at the discretion of the Board of Trustees.