Label

Element

Value

Risk/Return:

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Registrant Name

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JANUS INVESTMENT FUND

Prospectus Date

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Jan. 28, 2015

Janus International Equity Fund | Class D Shares

Risk/Return:

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Risk/Return [Heading]

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FUND SUMMARY

Janus International Equity Fund

Objective [Heading]

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INVESTMENT OBJECTIVE

Objective, Primary [Text Block]

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Janus International Equity Fund seeks long-term growth of capital.

Expense [Heading]

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FEES AND EXPENSES OF THE FUND

Expense Narrative [Text Block]

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This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund.

Operating Expenses Caption [Text]

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ANNUAL FUND OPERATING EXPENSES
(expenses that you pay each year as a percentage of the value of your investment)

Portfolio Turnover [Heading]

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Portfolio Turnover: 

Portfolio Turnover [Text Block]

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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 57% of the average value of its portfolio.

Portfolio Turnover, Rate

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57.00%

Expense Example [Heading]

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EXAMPLE:

Expense Example by Year [Heading]

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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:

Expense Example Narrative [Text Block]

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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]

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PRINCIPAL INVESTMENT STRATEGIES

Strategy Narrative [Text Block]

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The Fund pursues its investment objective by investing, under normal circumstances, at least 80% of its net assets in equity securities. The Fund normally invests in a core group of 60-100 equity securities of issuers that are economically tied to different countries throughout the world, excluding the United States. The Fund may, under unusual circumstances, invest all of its assets in a single country. The Fund may invest in emerging markets but will normally limit such investments to 20% of its net assets, measured at the time of purchase. The Fund may also invest in foreign debt securities.

The portfolio managers apply a “bottom up” approach in choosing investments. In other words, the portfolio managers look at companies one at a time to determine if a company is an attractive investment opportunity and if it is consistent with the Fund’s investment policies. The portfolio managers normally seek to limit any sector exposure and country exposure to plus or minus 10% of the respective weighting of the Fund’s primary benchmark index, currently the MSCI EAFE^® Index.

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.

Risk [Heading]

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PRINCIPAL INVESTMENT RISKS

Risk Narrative [Text Block]

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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 an equity portfolio, including common stocks. Common stocks tend to be more volatile than many other investment choices.

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 to a large degree 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. To the extent the Fund invests in foreign debt securities, such investments are sensitive to changes in interest rates. Additionally, investments in securities of foreign governments involve the risk that a foreign government may not be willing or able to pay interest or repay principal when due. The 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 mentioned above 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. There is a risk in developing countries that a 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 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 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. Additionally, foreign and emerging market risks, including but not limited to price controls, expropriation or confiscatory taxation, imposition or enforcement of foreign ownership limits, nationalization, and restrictions on repatriation of assets may be heightened to the extent the Fund invests in Chinese local market securities (also known as “A Shares”). As of September 30, 2014, approximately 13.9% of the Fund’s investments were in emerging markets.

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.

Growth Securities Risk. The Fund invests in companies after assessing their growth potential. Securities of companies perceived to be “growth” companies may be more volatile than other stocks and may involve special risks. If the portfolio managers’ perception of a company’s growth potential is not realized, the securities purchased may not perform as expected, reducing the Fund’s returns. In addition, because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “growth” stocks may perform differently from the market as a whole and other types of securities.

Real Estate Securities Risk. The Fund’s performance may be affected by the risks associated with investments in real estate-related companies. 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 real estate investment trusts (“REITs”) involve the same risks as other real estate investments. In addition, a REIT could fail to qualify for tax-free pass-through of its income under the Internal Revenue Code 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.

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.

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.

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]

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The biggest risk is that the Fund’s returns will vary, and you could lose money.

Risk Not Insured Depository Institution [Text]

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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.

Bar Chart and Performance Table [Heading]

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PERFORMANCE INFORMATION

Performance Narrative [Text Block]

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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 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. The indices are not actively managed and are not available for direct investment. 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 janus.com/allfunds or by calling 1-800-525-3713.

Performance Information Illustrates Variability of Returns [Text]

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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.

The bar chart depicts the change in performance from year to year during the periods indicated.

Performance Additional Market Index [Text]

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The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. The indices are not actively managed and are not available for direct investment. All figures assume reinvestment of dividends and distributions.

Performance Availability Phone [Text]

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1-800-525-3713

Performance Availability Website Address [Text]

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janus.com/allfunds

Performance Past Does Not Indicate Future [Text]

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The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future.

Bar Chart [Heading]

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Annual Total Returns for Class D Shares (calendar year-end)

Bar Chart Closing [Text Block]

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Best Quarter:  2nd Quarter 2009  31.92%          Worst Quarter:  3rd Quarter 2008  −24.25%

Performance Table Heading

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Average Annual Total Returns (periods ended 12/31/14)

Performance Table Uses Highest Federal Rate

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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

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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 Explanation after Tax Higher

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If the Fund incurs a loss, which generates a tax benefit, the Return After Taxes on Distributions and Sale of Fund Shares may exceed the Fund’s other return figures.

Performance Table Narrative

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The MSCI EAFE^® (Europe, Australasia, Far East) Index is a free float-adjusted market capitalization index designed to measure developed market equity performance. The MSCI EAFE^® Index is composed of companies representative of the market structure of developed market countries. The index includes reinvestment of dividends, net of foreign withholding taxes. This index is used to calculate the performance fee adjustment.

The MSCI All Country World ex-U.S. Index^SM is an unmanaged, free float-adjusted, market capitalization weighted index composed of stocks of companies located in countries throughout the world, excluding the United States. It is designed to measure equity market performance in global developed and emerging markets outside the United States. The index includes reinvestment of dividends, net of foreign withholding taxes.

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-deferred account, such as a 401(k) plan or an IRA.

Performance Table Closing [Text Block]

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Updated performance information is available at janus.com/allfunds or by calling 1-800-525-3713.

Janus International Equity Fund | Class D Shares | Class D

Risk/Return:

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Operating Expenses Column [Text]

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Class D

Management Fees (may adjust up or down)

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0.63%

Other Expenses

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0.28%

Total Annual Fund Operating Expenses

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0.91%

Expense Example, By Year, Column [Text]

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Class D Shares

1 Year

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93

3 Years

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290

5 Years

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504

10 Years

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1,120

2007

rr_AnnualReturn2007

22.23%

2008

rr_AnnualReturn2008

(45.99%)

2009

rr_AnnualReturn2009

51.91%

2010

rr_AnnualReturn2010

14.30%

2011

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(13.77%)

2012

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18.61%

2013

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21.98%

2014

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(5.23%)

Highest Quarterly Return, Label

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Best Quarter:

Highest Quarterly Return, Date

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Jun. 30, 2009

Highest Quarterly Return

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31.92%

Lowest Quarterly Return, Label

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Worst Quarter:

Lowest Quarterly Return, Date

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Sep. 30, 2008

Lowest Quarterly Return

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(24.25%)

Janus International Equity Fund | Class D Shares | Return Before Taxes | Class D

Risk/Return:

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Column

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Class D Shares

Label

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Return Before Taxes

1 Year

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(5.23%)

5 Years

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6.23%

Since Inception of Predecessor Fund

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4.51%

Inception Date

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Nov. 28, 2006

Janus International Equity Fund | Class D Shares | Return After Taxes on Distributions | Class D

Risk/Return:

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Column

rr_AverageAnnualReturnColumnName

Class D Shares

Label

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Return After Taxes on Distributions

1 Year

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(6.57%)

5 Years

rr_AverageAnnualReturnYear05

5.88%

Since Inception of Predecessor Fund

rr_AverageAnnualReturnSinceInception

4.21%

Inception Date

rr_AverageAnnualReturnInceptionDate

Nov. 28, 2006

Janus International Equity Fund | Class D Shares | Return After Taxes on Distributions and Sale of Fund Shares | Class D

Risk/Return:

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Column

rr_AverageAnnualReturnColumnName

Class D Shares

Label

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Return After Taxes on Distributions and Sale of Fund Shares

^[1]

1 Year

rr_AverageAnnualReturnYear01

(1.69%)

5 Years

rr_AverageAnnualReturnYear05

5.04%

Since Inception of Predecessor Fund

rr_AverageAnnualReturnSinceInception

3.67%

Inception Date

rr_AverageAnnualReturnInceptionDate

Nov. 28, 2006

Janus International Equity Fund | Class D Shares | MSCI EAFE® Index (reflects no deduction for expenses, fees, or taxes, except foreign withholding taxes)

Risk/Return:

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Label

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MSCI EAFE^® Index

1 Year

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(4.90%)

5 Years

rr_AverageAnnualReturnYear05

5.33%

Since Inception of Predecessor Fund

rr_AverageAnnualReturnSinceInception

1.54%

Inception Date

rr_AverageAnnualReturnInceptionDate

Nov. 28, 2006

Janus International Equity Fund | Class D Shares | MSCI All Country World ex-U.S. Index℠ (reflects no deduction for expenses, fees, or taxes, except foreign withholding taxes)

Risk/Return:

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Label

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MSCI All Country World ex-U.S. Index^SM

1 Year

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(3.87%)

5 Years

rr_AverageAnnualReturnYear05

4.43%

Since Inception of Predecessor Fund

rr_AverageAnnualReturnSinceInception

2.01%

Inception Date

rr_AverageAnnualReturnInceptionDate

Nov. 28, 2006

[1] If the Fund incurs a loss, which generates a tax benefit, the Return After Taxes on Distributions and Sale of Fund Shares may exceed the Fund’s other return figures.