497

FIST2 P1 09/18

SUPPLEMENT DATED SEPTEMBER 4, 2018

TO THE PROSPECTUS DATED MARCH 1, 2018

OF

Franklin low duration total return Fund

Franklin total return Fund

(Franklin Investors Securities Trust)

The prospectus is amended as follows:

I. The following is added to the “Fund Summaries – Franklin Low Duration Total Return Fund – Principal Investment Strategies” and “Fund Summaries – Franklin Total Return Fund – Principal Investment Strategies” sections of the prospectus:

The Fund may invest a small portion of its assets in marketplace loans to consumers and small and mid-sized enterprises or companies (SMEs) originated through online lending platforms.

II. The following is added to the “Fund Summaries – Franklin Low Duration Total Return Fund – Principal Risks” and “Fund Summaries – Franklin Total Return Fund – Principal Risks” sections of the prospectus:

Marketplace Loans   Marketplace loans are subject to the risks associated with debt investments generally, including but not limited to, interest rate, credit, liquidity, high yield debt, market and income risks. Marketplace loans generally are not rated by rating agencies, are often unsecured, and are highly risky and speculative investments. Lenders and investors, such as the Fund, assume all of the credit risk on the loans they fund or purchase and there are no assurances that payments due on underlying loans will be made. In addition, investments in marketplace loans may be adversely affected if the platform operator or a third-party service provider becomes unable or unwilling to fulfill its obligations in servicing the loans. Moreover, the Fund may have limited information about the underlying marketplace loans and information provided to the platform regarding the loans and the borrowers’ credit information may be incomplete, inaccurate or outdated. It also may be difficult for the Fund to sell an investment in a marketplace loan before maturity at the price at which the Fund believes the loan should be valued because these loans typically are considered by the Fund to be illiquid securities.

III. The following is added to the “Fund Details – Franklin Low Duration Total Return Fund – Principal Investment Policies and Practices” and “Fund Details – Franklin Total Return Fund – Principal Investment Policies and Practices” sections of the prospectus:

The Fund may invest a small portion of its assets in marketplace loans to consumers and small and mid-sized enterprises or companies (SMEs). Marketplace loans are loans that are originated through online lending platforms that match consumers, SMEs, and other borrowers seeking loans with investors willing to provide the funding for such loans. These borrowers may seek such loans for a variety of different purposes (e.g., loans for education, loans to fund elective medical procedures or loans for franchise financing). The yield to the lender on a marketplace loan is the fixed interest rate assigned by the platform to the loan net of any fees charged by the platform, including servicing fees, which cover the costs of services such as screening borrowers for their eligibility, managing the supply and demand of the marketplace, and facilitating payments and debt collection, among other things.

IV. The following is added to the “Fund Details – Franklin Low Duration Total Return Fund – Principal Risks” and “Fund Details – Franklin Total Return Fund – Principal Risks” sections of the prospectus:

Marketplace Loans

Marketplace loans are subject to the risks associated with debt investments generally, including but not limited to, interest rate, credit, liquidity, high yield debt, market and income risks. Marketplace loans generally are not rated by rating agencies, are often unsecured, and are highly risky and speculative investments. Lenders and investors, such as the Fund, assume all of the credit risk on the loans they fund or purchase and there are no assurances that payments due on underlying loans will be made. The Fund may not have direct recourse against the borrower or may be otherwise limited in its ability to enforce its rights with respect to its investment in marketplace loans, particularly in the case of unsecured loans. In addition, lenders and investors are not entitled to recover any deficiency of principal or interest from the platform operator if the underlying borrower defaults on its payments due with respect to a loan. Investments in marketplace loans may be adversely affected if the platform operator or a third-party service provider becomes unable or unwilling to fulfill its obligations in servicing the loans. Moreover, the Fund may have limited information about the underlying marketplace loans and the information provided to the platform regarding the loans and borrowers’ credit information may be incomplete, inaccurate or outdated. Additionally, the terms of certain loans may not restrict the borrowers from incurring additional debt. If a borrower incurs additional debt after obtaining a loan through a platform, the additional debt may adversely affect the borrower’s creditworthiness generally, and could result in the financial distress, insolvency or bankruptcy of the borrower. To the extent borrowers incur other indebtedness that is secured, such as a mortgage, the ability of the secured creditors to exercise collection remedies against the assets of that borrower may impair the borrower’s ability to repay its marketplace loan or it may impair the platform’s ability to collect on the marketplace loan upon default. When a marketplace loan is unsecured, borrowers may choose to repay other loans before repaying a loan facilitated through a platform because the borrowers have no collateral at risk. The Fund will not be made aware of any additional debt incurred by a borrower or whether such debt is secured, which could allow other creditors to move more quickly to claim assets of the borrower. Furthermore, U.S. based marketplace lending platforms are subject to extensive regulation, which could impair the enforcement of marketplace loans, among other things.

1

Finally, marketplace loans are not listed on any securities exchange and an active secondary market for such loans does not currently exist and may not develop in the future. It may be difficult for the Fund to sell an investment in a loan before its maturity at the price at which the Fund believes the loan should be valued. The Fund typically considers its investments in marketplace loans to be illiquid for purposes of its limitation on illiquid investments.

Please keep this supplement with your prospectus for future reference.

2

FIST2 SA1 09/18

SUPPLEMENT DATED SEPTEMBER 4, 2018

TO THE STATEMENT OF ADDITIONAL INFORMATION

DATED MARCH 1, 2018

OF

Franklin low duration total return Fund

Franklin total return Fund

(Franklin Investors Securities Trust)

The Statement of Additional Information (SAI) is amended as follows:

I. The following is added to the bullet point list in the “Goals, Strategies and Risks – Additional Strategies – Low Duration Fund” and “Goals, Strategies and Risks – Additional Strategies – Total Return Fund” sections of the SAI:

·marketplace loans

II. The following is added to the “Goals, Strategies and Risks – Glossary of Investments, Techniques, Strategies and Their Risks” section of the SAI:

Marketplace loans     Marketplace loans are originated through online platforms that provide a marketplace for lending and match consumers, small and mid-sized enterprises or companies (“SMEs”), and other borrowers seeking loans with investors willing to provide the funding for such loans (“Marketplace Loans”). These borrowers may seek such loans for a variety of different purposes (e.g., loans for education, loans to fund elective medical procedures or loans for franchise financing). The procedures through which borrowers obtain loans can vary between platforms, and between the types of loans (e.g., consumer versus SME). Marketplace lending is often referred to as “peer to peer” lending because of the industry’s initial focus on individual investors and consumer loan borrowers. However, since its inception, the industry has grown to include substantial involvement by institutional investors.

In the case of consumer platforms, prospective borrowers must disclose or otherwise make available to the platform operator certain financial and other information including, for example, the borrower’s credit score (as determined by a credit reporting agency), income, debt-to-income ratio, credit utilization, employment status, homeownership status, number of existing credit lines, intended use of funds, and the number and/or amount of recent payment defaults and delinquencies, certain of which information is then made available to prospective lenders. The borrower must satisfy the minimum eligibility requirements set by the platform operator. The platform operator uses the information provided by the borrower (along with other relevant data such as the characteristics of the loan) to assign its own credit rating (in the case of most consumer platforms) and the interest rate for the requested loan.

Lenders may select which loans to fund based on such borrower-provided information and platform-assigned credit rating (to the extent one is assigned) and the yield to the lender. The yield to the lender is the fixed interest rate assigned by the platform to the loan net of any fees charged by the platform, including servicing fees. Such servicing fees cover services such as screening borrowers for their eligibility, managing the supply and demand of the marketplace, and facilitating payments and debt collection, among other things. A typical servicing fee charged to the lender is 1% of the outstanding loan balance. Platforms may also charge borrowers an origination fee, which is typically 1% to 5% of the loan balance. The platforms may set limits as to the maximum dollar amount that may be requested by a borrower (whether through one or multiple loans) and the minimum dollar amount that a lender must provide under each loan. The loans originated through the online consumer lending platforms typically have a fixed term ranging between six months and five years in principal amounts with a minimum (e.g., $1,000) and maximum (e.g., $100,000), and typically amortize through equal monthly payments to their maturity dates.

In the United States, platforms are subject to extensive regulation, oversight and examination at the federal, state and local level, and across multiple jurisdictions if they operate their business nationwide. Accordingly, platforms are generally subject to various securities, lending, licensing and consumer protection laws. Most states limit by statute the maximum rate of interest that lenders may charge on consumer loans. A limited number of states also may have interest rate caps for certain commercial loans. The maximum permitted interest rate can vary substantially between states. Some states impose a fixed maximum rate while others link the maximum rate to a floating rate index. Some platforms obtain state lending licenses and lend directly to borrowers. Other platform operators through a contractual relationship with a bank purchase bank originated loans. In this model, an operator of a platform may be able to (through existing law and legal interpretations) be the beneficiary of the federal preemption available to federally insured banks that preempt the state laws and usury rates applicable under the various state laws where borrowers reside.

Risks of marketplace loans generally.     Marketplace Loans are subject to the risks associated with debt investments generally, including but not limited to, interest rate, credit, liquidity, high yield debt, market and income risks. Marketplace Loans generally are not rated by rating agencies and constitute a highly risky and speculative investment. There can be no assurance that payments due on underlying Marketplace Loans will be made. A platform operator is not obligated to make any payments due on a Marketplace Loan except to the extent that the operator actually receives payments from the borrower on the related loan. Accordingly, lenders and investors assume all of the credit risk on the loans they fund or purchase from a platform operator and are not entitled to recover any deficiency of principal or interest from the platform operator if the underlying borrower defaults on its payments due with respect to a loan. A substantial portion of the Marketplace Loans in which the Fund may invest will not be secured by any collateral, will not be guaranteed or insured by a third party and will not be backed by any governmental authority. Accordingly, the platforms and any third-party collection agencies will be limited in their ability to collect on defaulted Marketplace Loans. In addition, a platform operator is generally not required to repurchase Marketplace Loans from a lender or purchaser except under very narrow circumstances, such as in cases of verifiable identity fraud by the borrower or as may otherwise be negotiated by a purchaser of whole loans.

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To the extent a Marketplace Loan is secured, there can be no assurance as to the amount of any funds that may be realized from recovering and liquidating any collateral or the timing of such recovery and liquidation and hence there is no assurance that sufficient funds (or, possibly, any funds) will be available to offset any payment defaults that occur under the Marketplace Loan. Marketplace Loans are obligations of the borrowers and the terms of certain loans may not restrict the borrowers from incurring additional debt. If a borrower incurs additional debt after obtaining a loan through a platform, the additional debt may adversely affect the borrower’s creditworthiness generally, and could result in the financial distress, insolvency or bankruptcy of the borrower. To the extent borrowers incur other indebtedness that is secured, such as a mortgage, the ability of the secured creditors to exercise collection remedies against the assets of that borrower may impair the borrower’s ability to repay its Marketplace Loan or it may impair the platform’s ability to collect on the Marketplace Loan upon default. To the extent that a Marketplace Loan is unsecured, borrowers may choose to repay obligations under other indebtedness (such as loans obtained from traditional lending sources) before repaying a loan facilitated through a platform because the borrowers have no collateral at risk. The Fund will not be made aware of any additional debt incurred by a borrower, or whether such debt is secured. The effect of this can be to allow other creditors to move more quickly to claim any assets of the borrower.

Borrower credit risk.     Certain of the Marketplace Loans in which the Fund may invest may represent obligations of consumers who would not otherwise qualify for, or would have difficulty qualifying for, credit from traditional sources of lending, or SMEs that are unable to effectively access public equity or debt markets, as a result of, among other things, limited assets, adverse income characteristics, limited credit or operating history or an impaired credit record, which may include, for example in the case of consumers, a history of irregular employment, previous bankruptcy filings, repossessions of property, charged off loans and/or garnishment of wages. The average interest rate charged to, or required of, such obligors generally is higher than that charged by commercial banks and other institutions providing traditional sources of credit or that set by the debt market. As a result of the credit profile of the borrowers and the interest rates on Marketplace Loans, the delinquency and default experience on the Marketplace Loans may be significantly higher than those experienced by financial products arising from traditional sources of lending. The Fund may need to rely on the collection efforts of the platforms and third party collection agencies, which also may be limited in their ability to collect on defaulted loans. The Fund may not have direct recourse against borrowers, may not be able to obtain the identity of the borrowers in order to contact a borrower about a loan and may not be able to pursue borrowers to collect payment under loans. Borrowers may seek protection under federal bankruptcy law or similar laws. In most cases involving the bankruptcy of a borrower with an unsecured Marketplace Loan, unsecured creditors will receive only a fraction of any amount outstanding on their loan, if anything at all.

Fraud risk.     The Fund is subject to the risk of fraudulent activity associated with the various parties involved in marketplace lending, including the platforms, banks, borrowers and third parties handling borrower and investor information. For example, a borrower may have supplied false or inaccurate information. A platform’s resources, technologies and fraud prevention tools may be insufficient to accurately detect and prevent fraud. A platform may have the exclusive right and ability to investigate claims of borrower identity theft, which creates a conflict of interest. If a platform determines that verifiable identity theft has occurred, it may be required to repurchase the loan or indemnify the Fund. Alternatively, if the platform denies a claim of identity theft, it would not be required to repurchase the loan or indemnify the Fund.

Platform provided credit information risk.     The investment manager is reliant in part on the borrower credit information provided to it or assigned by the platforms when selecting Marketplace Loans for investment. To the extent a credit rating is assigned to each borrower by a platform, such rating may not accurately reflect the borrower’s actual creditworthiness. A platform may be unable, or may not seek, to verify all of the borrower information obtained by it. Borrower information on which platforms and lenders may rely may be outdated. In addition, certain information that the investment manager would otherwise seek may not be available, such as financial statements and other financial information. Furthermore, the investment manager may be unable to perform any independent follow-up verification with respect to a borrower to the extent the borrower’s name, address and other contact information is required to remain confidential. In addition, the platforms’ credit decisions and scoring models are based on algorithms that could potentially contain programming or other errors or prove to be ineffective or otherwise flawed.

Liquidity risk.     Investors that acquire Marketplace Loans directly from platforms must generally hold their loans through maturity in order to recoup their entire principal. No Marketplace Loans currently being offered have been registered with the U.S. Securities and Exchange Commission. In addition, Marketplace Loans are not listed on any securities exchange (although secondary market trading in pass-through notes issued by one platform does occur on one electronic “alternative trading system”). An active secondary market for Marketplace Loans does not currently exist and an active market for the Marketplace Loans may not develop in the future. Accordingly, it may be difficult for the Fund to sell an investment in Marketplace Loans at the price which the Fund believes the loan should be valued. The Fund typically considers its investments in Marketplace Loans to be illiquid for purposes of its limitation on illiquid investments.

4

Platform risk.     To the extent that the Fund invests in Marketplace Loans, it will be dependent on the continued success of the platforms that originate such loans. The Fund materially depends on such platforms for loan data and the origination, sourcing and servicing of Marketplace Loans and on the platform’s ability to collect, verify and provide information to the Fund about each Marketplace Loan and borrower.

Regulatory and judicial risks.     The platforms through which Marketplace Loans are originated are subject to various statutes, rules and regulations issued by federal, state and local government authorities. Federal and state consumer protection laws in particular impose requirements and place restrictions on creditors and service providers in connection with extensions of credit and collections on personal loans and protection of sensitive customer data obtained in the origination and servicing thereof. Platforms are also subject to laws relating to electronic commerce and transfer of funds in conducting business electronically. A failure to comply with the applicable rules and regulations may, among other things, subject the platform or its related entities to certain registration requirements with government authorities and the payment of any penalties and fines; result in the revocation of their licenses; cause the loan contracts originated by the platform to be voided or otherwise impair the enforcement of such loans; and subject them to potential civil and criminal liability, class action lawsuits and/or administrative or regulatory enforcement actions.

The federal and state consumer protection laws generally (i) require lenders to provide consumers with specified disclosures regarding the terms of the loans and/or impose substantive restrictions on the terms on which loans are made; (ii) prohibit lenders from discriminating against consumers on the basis of certain protected classes; and (iii) restrict the actions that a lender or debt collector can take to realize on delinquent or defaulted loans. Marketplace lending industry participants, including platforms, may be subject in certain cases to increased risk of litigation alleging violations of federal and state laws and regulations. In addition, courts have recently considered the regulatory environment applicable to marketplace lending platforms and purchasers of Marketplace Loans. In light of recent decisions, if upheld and widely applied, certain marketplace lending platforms could be required to restructure their operations and certain loans previously made by them through funding banks may not be enforceable, whether in whole or in part, by investors holding such loans or such loans could be subject to reduced returns and/or the platform subject to fines and penalties. As a result, Marketplace Loans purchased by the Fund could become unenforceable, thereby causing losses for shareholders.

Please keep this supplement with your SAI for future reference.

5

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Fund Summary

Franklin Investors Securities Trust - FIST2-24 | Franklin Low Duration Total Return Fund

Investment Goal

A high level of current income as is consistent with prudent investing, while seeking preservation of capital.

Fees and Expenses of the Fund

These tables describe the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts in Class A if you and your family invest, or agree to invest in the future, at least $100,000 in Franklin Templeton funds. More information about these and other discounts is available from your financial professional and under “Your Account” on page 139 in the Fund's Prospectus and under “Buying and Selling Shares” on page 85 of the Fund’s Statement of Additional Information. In addition, more information about sales charge discounts and waivers for purchases of shares through specific financial intermediaries is set forth in Appendix A – "Intermediary Sales Charge Discounts and Waivers" to the Fund’s prospectus.

Please note that the tables and examples below do not reflect any transaction fees that may be charged by financial intermediaries, or commissions that a shareholder may be required to pay directly to its financial intermediary when buying or selling Class R6 or Advisor Class shares.

Shareholder Fees (fees paid directly from your investment)

Shareholder Fees {- Franklin Low Duration Total Return Fund} - Franklin Investors Securities Trust - FIST2-24 - Franklin Low Duration Total Return Fund	Class A		Class C	Class R6	Advisor Class
Maximum Sales Charge (Load) Imposed on Purchases (as percentage of offering price)	2.25%		none	none	none
Maximum Deferred Sales Charge (Load) (as percentage of the lower of original purchase price or sale proceeds)	none	[1]	1.00%	none	none

Annual Fund Operating Expenses

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

Annual Operating Expenses {- Franklin Low Duration Total Return Fund} - Franklin Investors Securities Trust - FIST2-24 - Franklin Low Duration Total Return Fund		Class A	Class C	Class R6	Advisor Class
Management fees		0.50%	0.50%	0.50%	0.50%
Distribution and service (12b-1) fees		0.25%	0.65%	none	none
Other expenses	[1]	0.20%	0.20%	0.05%	0.20%
Acquired fund fees and expenses		0.02%	0.02%	0.02%	0.02%
Total annual Fund operating expenses	[1]	0.97%	1.37%	0.57%	0.72%
Fee waiver and/or expense reimbursement	[2]	(0.26%)	(0.26%)	(0.26%)	(0.26%)
Total annual Fund operating expenses after fee waiver and/or expense reimbursement	[1],[2]	0.71%	1.11%	0.31%	0.46%

Example

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of the period. The Example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same. The Example reflects adjustments made to the Fund's operating expenses due to the fee waivers and/or expense reimbursements by management for the 1 Year numbers only. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example {- Franklin Low Duration Total Return Fund} - Franklin Investors Securities Trust - FIST2-24 - Franklin Low Duration Total Return Fund - USD ($)	Class A	Class C	Class R6	Advisor Class
1 year	$ 296	$ 213	$ 32	$ 47
3 years	502	408	156	204
5 years	725	725	293	375
10 years	$ 1,366	$ 1,625	$ 689	$ 871

If you do not sell your shares:

Expense Example, No Redemption {- Franklin Low Duration Total Return Fund}	Franklin Investors Securities Trust - FIST2-24 Franklin Low Duration Total Return Fund Class C USD ($)
1 Year	$ 113
3 Years	408
5 Years	725
10 Years	$ 1,625

Portfolio Turnover

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 50.40% of the average value of its portfolio.

Principal Investment Strategies

Under normal market conditions, the Fund invests primarily in debt securities, which may be represented by derivative investments that provide exposure to debt securities such as futures, options and swap agreements. The debt securities in which the Fund may invest include government and corporate debt securities, mortgage- and asset-backed securities, floating interest rate corporate loans and debt securities and municipal securities.

The Fund targets an estimated average portfolio duration of three (3) years or less. Duration is a measure of the expected price volatility of a debt instrument as a result of changes in market rates of interest, based on the weighted average timing of the instrument’s expected principal and interest payments and other factors.

The Fund invests primarily in investment grade debt securities and in unrated securities that the investment manager deems are of comparable quality. Derivatives whose reference securities are investment grade are considered by the Fund to be investment grade. The Fund's focus on the credit quality of its portfolio is intended to reduce credit risk and help to preserve the Fund's capital.

The Fund also may invest up to 20% of its total assets in non-investment grade securities, including up to 5% in securities rated lower than B- by S&P or Moody's, which may include defaulted securities. (In calculating the above non-investment grade debt limitations, the Fund combines its non-investment grade debt securities with the net long and short exposure to non-investment grade debt securities from derivative instruments.) Excluding derivatives, the Fund will invest no more than 33% of its total assets in non-investment grade debt securities, including no more than 5% in securities rated lower than B- by S&P or Moody's, which may include defaulted securities. For purposes of the credit limitations above, non-investment grade debt securities include unrated securities that the investment manager deems are of comparable quality.

The Fund may invest up to 25% of its total assets in foreign securities, including up to 20% of its total assets in non-U.S. dollar denominated securities and up to 10% of its total assets in emerging market securities.

The Fund may invest a small portion of its assets in marketplace loans to consumers and small and mid-sized enterprises or companies (SMEs) originated through online lending platforms.

The Fund may invest in many different securities issued or guaranteed by the U.S. government or by non-U.S. governments or their respective agencies or instrumentalities, including mortgage-backed securities and inflation-indexed securities issued by the U.S. Treasury. Mortgage-backed securities represent an interest in a pool of mortgage loans made by banks and other financial institutions to finance purchases of homes, commercial buildings and other real estate. The individual mortgage loans are packaged or "pooled" together for sale to investors. As the underlying mortgage loans are paid off, investors receive principal and interest payments. These securities may be fixed-rate or adjustable-rate mortgage-backed securities (ARMS). The Fund may also invest a small portion of its assets directly in mortgage loans.

To pursue its investment goal, the Fund regularly enters into various derivative transactions, including currency forwards, currency, interest rate/bond futures contracts and options on interest rate futures contracts, and swap agreements, including interest rate, fixed income total return, currency and credit default swaps, and options on interest rate and credit default swap agreements. The use of these derivative transactions may allow the Fund to obtain net long or short exposures to select currencies, interest rates, countries, duration or credit risks. These derivatives may be used to enhance Fund returns, increase liquidity, gain exposure to certain instruments or markets in a more efficient or less expensive way and/or hedge risks associated with its other portfolio investments.

In choosing investments, the Fund’s investment manager selects securities in various market sectors based on the investment manager’s assessment of changing economic, market, industry and issuer conditions. The investment manager uses a “top-down” analysis of macroeconomic trends, combined with a “bottom-up” fundamental analysis of market sectors, industries and issuers, to try to take advantage of varying sector reactions to economic events.

Principal Risks

You could lose money by investing in the Fund. Mutual fund shares are not deposits or obligations of, or guaranteed or endorsed by, any bank, and are not insured by the Federal Deposit Insurance Corporation, the Federal Reserve Board, or any other agency of the U.S. government.

Interest Rate

When interest rates rise, debt security prices generally fall. The opposite is also generally true: debt security prices rise when interest rates fall. Interest rate changes are influenced by a number of factors, including government policy, monetary policy, inflation expectations, perceptions of risk, and supply and demand of bonds. In general, fixed rate securities with longer maturities or durations are more sensitive to interest rate changes.

Credit

An issuer of debt securities may fail to make interest payments or repay principal when due, in whole or in part. Changes in an issuer's financial strength or in a security's credit rating may affect a security's value.

High-Yield Debt Securities

Issuers of lower-rated or “high-yield” debt securities (also known as “junk bonds”) are not as strong financially as those issuing higher credit quality debt securities. High-yield debt securities are generally considered predominantly speculative by the applicable rating agencies as their issuers are more likely to encounter financial difficulties because they may be more highly leveraged, or because of other considerations. In addition, high yield debt securities generally are more vulnerable to changes in the relevant economy, such as a recession or a sustained period of rising interest rates, that could affect their ability to make interest and principal payments when due. The prices of high-yield debt securities generally fluctuate more than those of higher credit quality. High-yield debt securities are generally more illiquid (harder to sell) and harder to value.

Floating Rate Corporate Investments

Floating rate corporate loans and corporate debt securities generally have credit ratings below investment grade and may be subject to resale restrictions. They are often issued in connection with highly leveraged transactions, and may be subject to greater credit risks than other investments including the possibility of default or bankruptcy. In addition, a secondary market in corporate loans may be subject to irregular trading activity, wide bid/ask spreads and extended trade settlement periods, which may impair the ability to accurately value existing and prospective investments and to realize in a timely fashion the full value on sale of a corporate loan. A significant portion of floating rate investments may be “covenant lite” loans that may contain fewer or less restrictive constraints on the borrower or other borrower-friendly characteristics.

Derivative Instruments

The performance of derivative instruments depends largely on the performance of an underlying instrument, such as a currency, security, interest rate or index, and such instruments often have risks similar to the underlying instrument, in addition to other risks. Derivatives involve costs and can create economic leverage in the Fund’s portfolio which may result in significant volatility and cause the Fund to participate in losses (as well as gains) in an amount that exceeds the Fund’s initial investment. Other risks include illiquidity, mispricing or improper valuation of the derivative instrument, and imperfect correlation between the value of the derivative and the underlying instrument so that the Fund may not realize the intended benefits. When a derivative is used for hedging, the change in value of the derivative may also not correlate specifically with the currency, security, interest rate, index or other risk being hedged. Derivatives also may present the risk that the other party to the transaction will fail to perform.

Income

Because the Fund can only distribute what it earns, the Fund's distributions to shareholders may decline when prevailing interest rates fall, when the Fund experiences defaults on debt securities it holds, or when the Fund realizes a loss upon the sale of a debt security.

Mortgage Securities and Asset-Backed Securities

Mortgage securities differ from conventional debt securities because principal is paid back periodically over the life of the security rather than at maturity. The Fund may receive unscheduled payments of principal due to voluntary prepayments, refinancings or foreclosures on the underlying mortgage loans. Because of prepayments, mortgage securities may be less effective than some other types of debt securities as a means of "locking in" long-term interest rates and may have less potential for capital appreciation during periods of falling interest rates. A reduction in the anticipated rate of principal prepayments, especially during periods of rising interest rates, may increase or extend the effective maturity of mortgage securities, making them more sensitive to interest rate changes, subject to greater price volatility, and more susceptible than some other debt securities to a decline in market value when interest rates rise.

Issuers of asset-backed securities may have limited ability to enforce the security interest in the underlying assets, and credit enhancements provided to support the securities, if any, may be inadequate to protect investors in the event of default. Like mortgage securities, asset-backed securities are subject to prepayment and extension risks.

Foreign Securities (non U.S.)

Investing in foreign securities typically involves more risks than investing in U.S. securities, including risks related to currency exchange rates and policies, country or government specific issues, less favorable trading practices or regulation and greater price volatility. Certain of these risks also may apply to securities of U.S. companies with significant foreign operations.

Currency Management Strategies

Currency management strategies may substantially change the Fund’s exposure to currency exchange rates and could result in losses to the Fund if currencies do not perform as the investment manager expects. In addition, currency management strategies, to the extent that they reduce the Fund’s exposure to currency risks, may also reduce the Fund’s ability to benefit from favorable changes in currency exchange rates. Using currency management strategies for purposes other than hedging further increases the Fund’s exposure to foreign investment losses. Currency markets generally are not as regulated as securities markets. In addition, currency rates may fluctuate significantly over short periods of time, and can reduce returns.

Sovereign Debt Securities

Sovereign debt securities are subject to various risks in addition to those relating to debt securities and foreign securities generally, including, but not limited to, the risk that a governmental entity may be unwilling or unable to pay interest and repay principal on its sovereign debt, or otherwise meet its obligations when due because of cash flow problems, insufficient foreign reserves, the relative size of the debt service burden to the economy as a whole, the government’s policy towards principal international lenders such as the International Monetary Fund, or the political considerations to which the government may be subject. If a sovereign debtor defaults (or threatens to default) on its sovereign debt obligations, the indebtedness may be restructured. Some sovereign debtors have in the past been able to restructure their debt payments without the approval of some or all debt holders or to declare moratoria on payments. In the event of a default on sovereign debt, the Fund may also have limited legal recourse against the defaulting government entity.

Emerging Market Countries

The Fund’s investments in emerging market countries are subject to all of the risks of foreign investing generally, and have additional heightened risks due to a lack of established legal, political, business and social frameworks to support securities and currency markets, including: delays in settling portfolio transactions; currency and capital controls; greater sensitivity to interest rate changes; pervasiveness of corruption and crime; currency exchange rate volatility; and inflation, deflation or currency devaluation.

Extension

Some debt securities, particularly mortgage-backed securities, are subject to the risk that the debt security’s effective maturity is extended because calls or prepayments are less or slower than anticipated, particularly when interest rates rise. The market value of such security may then decline and become more interest rate sensitive.

Prepayment

Prepayment risk occurs when a debt security can be repaid in whole or in part prior to the security's maturity and the Fund must reinvest the proceeds it receives, during periods of declining interest rates, in securities that pay a lower rate of interest. Also, if a security has been purchased at a premium, the value of the premium would be lost in the event of prepayment. Prepayments generally increase when interest rates fall.

Marketplace Loans

Marketplace loans are subject to the risks associated with debt investments generally, including but not limited to, interest rate, credit, liquidity, high yield debt, market and income risks. Marketplace loans generally are not rated by rating agencies, are often unsecured, and are highly risky and speculative investments. Lenders and investors, such as the Fund, assume all of the credit risk on the loans they fund or purchase and there are no assurances that payments due on underlying loans will be made. In addition, investments in marketplace loans may be adversely affected if the platform operator or a third-party service provider becomes unable or unwilling to fulfill its obligations in servicing the loans. Moreover, the Fund may have limited information about the underlying marketplace loans and information provided to the platform regarding the loans and the borrowers’ credit information may be incomplete, inaccurate or outdated. It also may be difficult for the Fund to sell an investment in a marketplace loan before maturity at the price at which the Fund believes the loan should be valued because these loans typically are considered by the Fund to be illiquid securities.

Liquidity

From time to time, the trading market for a particular security or type of security or other investments in which the Fund invests may become less liquid or even illiquid. Reduced liquidity will have an adverse impact on the Fund’s ability to sell such securities or other investments when necessary to meet the Fund’s liquidity needs, in response to a specific economic event or to buy particular securities to invest available cash or when considered advantageous by the investment manager. Reduced liquidity will also generally lower the value of such securities or other investments. Market prices for such securities or other investments may be volatile.

Variable Rate Securities

Because changes in interest rates on variable rate securities (including floating rate securities) may lag behind changes in market rates, the value of such securities may decline during periods of rising interest rates until their interest rates reset to market rates. During periods of declining interest rates, because the interest rates on variable rate securities generally reset downward, their market value is unlikely to rise to the same extent as the value of comparable fixed rate securities.

Market

The market values of securities or other investments owned by the Fund will go up or down, sometimes rapidly or unpredictably. The market value of a security or other investment may be reduced by market activity or other results of supply and demand unrelated to the issuer. This is a basic risk associated with all investments. When there are more sellers than buyers, prices tend to fall. Likewise, when there are more buyers than sellers, prices tend to rise.

Management

The Fund is subject to management risk because it is an actively managed investment portfolio. The Fund's investment manager applies investment techniques and risk analyses in making investment decisions for the Fund, but there can be no guarantee that these decisions will produce the desired results.

Performance

The following bar chart and table provide some indication of the risks of investing in the Fund. The bar chart shows changes in the Fund's performance from year to year for Class A shares. The table shows how the Fund's average annual returns for 1 year, 5 years, 10 years or since inception, as applicable, compared with those of a broad measure of market performance. The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You can obtain updated performance information at franklintempleton.com or by calling (800) DIAL BEN/342-5236.

Sales charges are not reflected in the bar chart, and if those charges were included, returns would be less than those shown.

Class A Annual Total Returns

Best Quarter:	Q3'09	2.87%
Worst Quarter:	Q3'11	-1.94%

Average Annual Total Returns
(figures reflect sales charges)

For the periods ended December 31, 2017

Average Annual Total Returns{- Franklin Low Duration Total Return Fund} - Franklin Investors Securities Trust - FIST2-24 - Franklin Low Duration Total Return Fund	Past 1 year	Past 5 years	Past 10 years	Since Inception	[1]
Class A | Return Before Taxes	(1.09%)	0.63%	2.29%
Class A | After Taxes on Distributions	(1.87%)	(0.25%)	1.26%
Class A | After Taxes on Distributions and Sales	(0.62%)	0.08%	1.35%
Class C | Return Before Taxes	(0.19%)	0.68%	2.10%
Class R6 | Return Before Taxes	1.55%			1.38%
Advisor Class | Return Before Taxes	1.52%	1.34%	2.78%
Bloomberg Barclays U.S. Government & Credit (1-3 Year) Index (index reflects no deduction for fees, expenses or taxes)	0.84%	0.84%	1.85%

Historical performance for Class C shares prior to their inception is based on the performance of Class A shares. Class C performance has been adjusted to reflect differences in sales charges and 12b-1 expenses between classes.

The after-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns are shown only for Class A and after-tax returns for other classes will vary.

[1] There is a 0.75% contingent deferred sales charge that applies to investments of $1 million or more (see“Investments of $1 Million or More” under “Choosing a Share Class”) and purchases by certain retirement plans without an initial sales charge on shares sold within 18 months of purchase.

[1] Other expenses of the Fund have been restated to exclude non-recurring prior period expenses and for Class R6 shares, to reflect current fiscal year expenses. If the non-recurring prior period expenses were included in the table above, the amounts stated would have been greater. Consequently, the total annual Fund operating expenses differ from the ratio of expenses to average net assets shown in the Financial Highlights.

[2] The investment manager has contractually agreed to waive or assume certain expenses so that common expenses (excluding the Rule 12b-1 fees, acquired fund fees and expenses and certain non-routine expenses) for each class of the Fund do not exceed 0.44% until February 28, 2019. The investment manager also has contractually agreed in advance to reduce its fees as a result of the Fund's investments in Franklin Templeton affiliated funds (acquired funds) for the next 12-month period. Contractual fee waiver and/or expense reimbursement agreements may not be changed or terminated during the time period set forth above.

[1] Since inception May 1, 2013.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

FRANKLIN INVESTORS SECURITIES TRUST

Prospectus Date

rr_ProspectusDate

Sep. 04, 2018

Risk/Return [Heading]

rr_RiskReturnHeading

Fund Summary

Franklin Investors Securities Trust - FIST2-24 | Franklin Low Duration Total Return Fund

Risk/Return:

rr_RiskReturnAbstract

Objective [Heading]

rr_ObjectiveHeading

Investment Goal

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

A high level of current income as is consistent with prudent investing, while seeking preservation of capital.

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses of the Fund

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

These tables describe the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts in Class A if you and your family invest, or agree to invest in the future, at least $100,000 in Franklin Templeton funds. More information about these and other discounts is available from your financial professional and under “Your Account” on page 139 in the Fund's Prospectus and under “Buying and Selling Shares” on page 85 of the Fund’s Statement of Additional Information. In addition, more information about sales charge discounts and waivers for purchases of shares through specific financial intermediaries is set forth in Appendix A – "Intermediary Sales Charge Discounts and Waivers" to the Fund’s prospectus.

Please note that the tables and examples below do not reflect any transaction fees that may be charged by financial intermediaries, or commissions that a shareholder may be required to pay directly to its financial intermediary when buying or selling Class R6 or Advisor Class shares.

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder Fees (fees paid directly from your investment)

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses

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

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

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 50.40% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

50.40%

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may qualify for sales charge discounts in Class A if you and your family invest, or agree to invest in the future, at least $100,000 in Franklin Templeton funds.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

$ 100,000

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of the period. The Example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same. The Example reflects adjustments made to the Fund's operating expenses due to the fee waivers and/or expense reimbursements by management for the 1 Year numbers only. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example, No Redemption, By Year, Caption [Text]

rr_ExpenseExampleNoRedemptionByYearCaption

If you do not sell your shares:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Under normal market conditions, the Fund invests primarily in debt securities, which may be represented by derivative investments that provide exposure to debt securities such as futures, options and swap agreements. The debt securities in which the Fund may invest include government and corporate debt securities, mortgage- and asset-backed securities, floating interest rate corporate loans and debt securities and municipal securities.

The Fund targets an estimated average portfolio duration of three (3) years or less. Duration is a measure of the expected price volatility of a debt instrument as a result of changes in market rates of interest, based on the weighted average timing of the instrument’s expected principal and interest payments and other factors.

The Fund invests primarily in investment grade debt securities and in unrated securities that the investment manager deems are of comparable quality. Derivatives whose reference securities are investment grade are considered by the Fund to be investment grade. The Fund's focus on the credit quality of its portfolio is intended to reduce credit risk and help to preserve the Fund's capital.

The Fund also may invest up to 20% of its total assets in non-investment grade securities, including up to 5% in securities rated lower than B- by S&P or Moody's, which may include defaulted securities. (In calculating the above non-investment grade debt limitations, the Fund combines its non-investment grade debt securities with the net long and short exposure to non-investment grade debt securities from derivative instruments.) Excluding derivatives, the Fund will invest no more than 33% of its total assets in non-investment grade debt securities, including no more than 5% in securities rated lower than B- by S&P or Moody's, which may include defaulted securities. For purposes of the credit limitations above, non-investment grade debt securities include unrated securities that the investment manager deems are of comparable quality.

The Fund may invest up to 25% of its total assets in foreign securities, including up to 20% of its total assets in non-U.S. dollar denominated securities and up to 10% of its total assets in emerging market securities.

The Fund may invest a small portion of its assets in marketplace loans to consumers and small and mid-sized enterprises or companies (SMEs) originated through online lending platforms.

The Fund may invest in many different securities issued or guaranteed by the U.S. government or by non-U.S. governments or their respective agencies or instrumentalities, including mortgage-backed securities and inflation-indexed securities issued by the U.S. Treasury. Mortgage-backed securities represent an interest in a pool of mortgage loans made by banks and other financial institutions to finance purchases of homes, commercial buildings and other real estate. The individual mortgage loans are packaged or "pooled" together for sale to investors. As the underlying mortgage loans are paid off, investors receive principal and interest payments. These securities may be fixed-rate or adjustable-rate mortgage-backed securities (ARMS). The Fund may also invest a small portion of its assets directly in mortgage loans.

To pursue its investment goal, the Fund regularly enters into various derivative transactions, including currency forwards, currency, interest rate/bond futures contracts and options on interest rate futures contracts, and swap agreements, including interest rate, fixed income total return, currency and credit default swaps, and options on interest rate and credit default swap agreements. The use of these derivative transactions may allow the Fund to obtain net long or short exposures to select currencies, interest rates, countries, duration or credit risks. These derivatives may be used to enhance Fund returns, increase liquidity, gain exposure to certain instruments or markets in a more efficient or less expensive way and/or hedge risks associated with its other portfolio investments.

In choosing investments, the Fund’s investment manager selects securities in various market sectors based on the investment manager’s assessment of changing economic, market, industry and issuer conditions. The investment manager uses a “top-down” analysis of macroeconomic trends, combined with a “bottom-up” fundamental analysis of market sectors, industries and issuers, to try to take advantage of varying sector reactions to economic events.

Strategy Portfolio Concentration [Text]

rr_StrategyPortfolioConcentration

Under normal market conditions, the Fund invests primarily in debt securities, which may be represented by derivative investments that provide exposure to debt securities such as futures, options and swap agreements. The debt securities in which the Fund may invest include government and corporate debt securities, mortgage- and asset-backed securities, floating interest rate corporate loans and debt securities and municipal securities.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

You could lose money by investing in the Fund. Mutual fund shares are not deposits or obligations of, or guaranteed or endorsed by, any bank, and are not insured by the Federal Deposit Insurance Corporation, the Federal Reserve Board, or any other agency of the U.S. government.

Interest Rate

When interest rates rise, debt security prices generally fall. The opposite is also generally true: debt security prices rise when interest rates fall. Interest rate changes are influenced by a number of factors, including government policy, monetary policy, inflation expectations, perceptions of risk, and supply and demand of bonds. In general, fixed rate securities with longer maturities or durations are more sensitive to interest rate changes.

Credit

An issuer of debt securities may fail to make interest payments or repay principal when due, in whole or in part. Changes in an issuer's financial strength or in a security's credit rating may affect a security's value.

High-Yield Debt Securities

Issuers of lower-rated or “high-yield” debt securities (also known as “junk bonds”) are not as strong financially as those issuing higher credit quality debt securities. High-yield debt securities are generally considered predominantly speculative by the applicable rating agencies as their issuers are more likely to encounter financial difficulties because they may be more highly leveraged, or because of other considerations. In addition, high yield debt securities generally are more vulnerable to changes in the relevant economy, such as a recession or a sustained period of rising interest rates, that could affect their ability to make interest and principal payments when due. The prices of high-yield debt securities generally fluctuate more than those of higher credit quality. High-yield debt securities are generally more illiquid (harder to sell) and harder to value.

Floating Rate Corporate Investments

Floating rate corporate loans and corporate debt securities generally have credit ratings below investment grade and may be subject to resale restrictions. They are often issued in connection with highly leveraged transactions, and may be subject to greater credit risks than other investments including the possibility of default or bankruptcy. In addition, a secondary market in corporate loans may be subject to irregular trading activity, wide bid/ask spreads and extended trade settlement periods, which may impair the ability to accurately value existing and prospective investments and to realize in a timely fashion the full value on sale of a corporate loan. A significant portion of floating rate investments may be “covenant lite” loans that may contain fewer or less restrictive constraints on the borrower or other borrower-friendly characteristics.

Derivative Instruments

The performance of derivative instruments depends largely on the performance of an underlying instrument, such as a currency, security, interest rate or index, and such instruments often have risks similar to the underlying instrument, in addition to other risks. Derivatives involve costs and can create economic leverage in the Fund’s portfolio which may result in significant volatility and cause the Fund to participate in losses (as well as gains) in an amount that exceeds the Fund’s initial investment. Other risks include illiquidity, mispricing or improper valuation of the derivative instrument, and imperfect correlation between the value of the derivative and the underlying instrument so that the Fund may not realize the intended benefits. When a derivative is used for hedging, the change in value of the derivative may also not correlate specifically with the currency, security, interest rate, index or other risk being hedged. Derivatives also may present the risk that the other party to the transaction will fail to perform.

Income

Because the Fund can only distribute what it earns, the Fund's distributions to shareholders may decline when prevailing interest rates fall, when the Fund experiences defaults on debt securities it holds, or when the Fund realizes a loss upon the sale of a debt security.

Mortgage Securities and Asset-Backed Securities

Mortgage securities differ from conventional debt securities because principal is paid back periodically over the life of the security rather than at maturity. The Fund may receive unscheduled payments of principal due to voluntary prepayments, refinancings or foreclosures on the underlying mortgage loans. Because of prepayments, mortgage securities may be less effective than some other types of debt securities as a means of "locking in" long-term interest rates and may have less potential for capital appreciation during periods of falling interest rates. A reduction in the anticipated rate of principal prepayments, especially during periods of rising interest rates, may increase or extend the effective maturity of mortgage securities, making them more sensitive to interest rate changes, subject to greater price volatility, and more susceptible than some other debt securities to a decline in market value when interest rates rise.

Issuers of asset-backed securities may have limited ability to enforce the security interest in the underlying assets, and credit enhancements provided to support the securities, if any, may be inadequate to protect investors in the event of default. Like mortgage securities, asset-backed securities are subject to prepayment and extension risks.

Foreign Securities (non U.S.)

Investing in foreign securities typically involves more risks than investing in U.S. securities, including risks related to currency exchange rates and policies, country or government specific issues, less favorable trading practices or regulation and greater price volatility. Certain of these risks also may apply to securities of U.S. companies with significant foreign operations.

Currency Management Strategies

Currency management strategies may substantially change the Fund’s exposure to currency exchange rates and could result in losses to the Fund if currencies do not perform as the investment manager expects. In addition, currency management strategies, to the extent that they reduce the Fund’s exposure to currency risks, may also reduce the Fund’s ability to benefit from favorable changes in currency exchange rates. Using currency management strategies for purposes other than hedging further increases the Fund’s exposure to foreign investment losses. Currency markets generally are not as regulated as securities markets. In addition, currency rates may fluctuate significantly over short periods of time, and can reduce returns.

Sovereign Debt Securities

Sovereign debt securities are subject to various risks in addition to those relating to debt securities and foreign securities generally, including, but not limited to, the risk that a governmental entity may be unwilling or unable to pay interest and repay principal on its sovereign debt, or otherwise meet its obligations when due because of cash flow problems, insufficient foreign reserves, the relative size of the debt service burden to the economy as a whole, the government’s policy towards principal international lenders such as the International Monetary Fund, or the political considerations to which the government may be subject. If a sovereign debtor defaults (or threatens to default) on its sovereign debt obligations, the indebtedness may be restructured. Some sovereign debtors have in the past been able to restructure their debt payments without the approval of some or all debt holders or to declare moratoria on payments. In the event of a default on sovereign debt, the Fund may also have limited legal recourse against the defaulting government entity.

Emerging Market Countries

The Fund’s investments in emerging market countries are subject to all of the risks of foreign investing generally, and have additional heightened risks due to a lack of established legal, political, business and social frameworks to support securities and currency markets, including: delays in settling portfolio transactions; currency and capital controls; greater sensitivity to interest rate changes; pervasiveness of corruption and crime; currency exchange rate volatility; and inflation, deflation or currency devaluation.

Extension

Some debt securities, particularly mortgage-backed securities, are subject to the risk that the debt security’s effective maturity is extended because calls or prepayments are less or slower than anticipated, particularly when interest rates rise. The market value of such security may then decline and become more interest rate sensitive.

Prepayment

Prepayment risk occurs when a debt security can be repaid in whole or in part prior to the security's maturity and the Fund must reinvest the proceeds it receives, during periods of declining interest rates, in securities that pay a lower rate of interest. Also, if a security has been purchased at a premium, the value of the premium would be lost in the event of prepayment. Prepayments generally increase when interest rates fall.

Marketplace Loans

Marketplace loans are subject to the risks associated with debt investments generally, including but not limited to, interest rate, credit, liquidity, high yield debt, market and income risks. Marketplace loans generally are not rated by rating agencies, are often unsecured, and are highly risky and speculative investments. Lenders and investors, such as the Fund, assume all of the credit risk on the loans they fund or purchase and there are no assurances that payments due on underlying loans will be made. In addition, investments in marketplace loans may be adversely affected if the platform operator or a third-party service provider becomes unable or unwilling to fulfill its obligations in servicing the loans. Moreover, the Fund may have limited information about the underlying marketplace loans and information provided to the platform regarding the loans and the borrowers’ credit information may be incomplete, inaccurate or outdated. It also may be difficult for the Fund to sell an investment in a marketplace loan before maturity at the price at which the Fund believes the loan should be valued because these loans typically are considered by the Fund to be illiquid securities.

Liquidity

From time to time, the trading market for a particular security or type of security or other investments in which the Fund invests may become less liquid or even illiquid. Reduced liquidity will have an adverse impact on the Fund’s ability to sell such securities or other investments when necessary to meet the Fund’s liquidity needs, in response to a specific economic event or to buy particular securities to invest available cash or when considered advantageous by the investment manager. Reduced liquidity will also generally lower the value of such securities or other investments. Market prices for such securities or other investments may be volatile.

Variable Rate Securities

Because changes in interest rates on variable rate securities (including floating rate securities) may lag behind changes in market rates, the value of such securities may decline during periods of rising interest rates until their interest rates reset to market rates. During periods of declining interest rates, because the interest rates on variable rate securities generally reset downward, their market value is unlikely to rise to the same extent as the value of comparable fixed rate securities.

Market

The market values of securities or other investments owned by the Fund will go up or down, sometimes rapidly or unpredictably. The market value of a security or other investment may be reduced by market activity or other results of supply and demand unrelated to the issuer. This is a basic risk associated with all investments. When there are more sellers than buyers, prices tend to fall. Likewise, when there are more buyers than sellers, prices tend to rise.

Management

The Fund is subject to management risk because it is an actively managed investment portfolio. The Fund's investment manager applies investment techniques and risk analyses in making investment decisions for the Fund, but there can be no guarantee that these decisions will produce the desired results.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The following bar chart and table provide some indication of the risks of investing in the Fund. The bar chart shows changes in the Fund's performance from year to year for Class A shares. The table shows how the Fund's average annual returns for 1 year, 5 years, 10 years or since inception, as applicable, compared with those of a broad measure of market performance. The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You can obtain updated performance information at franklintempleton.com or by calling (800) DIAL BEN/342-5236.

Sales charges are not reflected in the bar chart, and if those charges were included, returns would be less than those shown.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The following bar chart and table provide some indication of the risks of investing in the Fund. The bar chart shows changes in the Fund's performance from year to year for Class A shares. The table shows how the Fund's average annual returns for 1 year, 5 years, 10 years or since inception, as applicable, compared with those of a broad measure of market performance.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

(800) DIAL BEN/342-5236

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

franklintempleton.com

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.

Bar Chart [Heading]

rr_BarChartHeading

Class A Annual Total Returns

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

Sales charges are not reflected in the bar chart, and if those charges were included, returns would be less than those shown.

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Best Quarter:	Q3'09	2.87%
Worst Quarter:	Q3'11	-1.94%

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns
(figures reflect sales charges)

For the periods ended December 31, 2017

Performance Table Closing [Text Block]

rr_PerformanceTableClosingTextBlock

Historical performance for Class C shares prior to their inception is based on the performance of Class A shares. Class C performance has been adjusted to reflect differences in sales charges and 12b-1 expenses between classes.

The after-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns are shown only for Class A and after-tax returns for other classes will vary.

Franklin Investors Securities Trust - FIST2-24 | Franklin Low Duration Total Return Fund | Class A

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as percentage of offering price)

rr_MaximumCumulativeSalesChargeOverOfferingPrice

2.25%

Maximum Deferred Sales Charge (Load) (as percentage of the lower of original purchase price or sale proceeds)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

^[1]

Management fees

rr_ManagementFeesOverAssets

0.50%

Distribution and service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.20%

^[2]

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.02%

Total annual Fund operating expenses

rr_ExpensesOverAssets

0.97%

^[2]

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.26%)

^[3]

Total annual Fund operating expenses after fee waiver and/or expense reimbursement

rr_NetExpensesOverAssets

0.71%

^[2],[3]

1 year

rr_ExpenseExampleYear01

$ 296

3 years

rr_ExpenseExampleYear03

502

5 years

rr_ExpenseExampleYear05

725

10 years

rr_ExpenseExampleYear10

$ 1,366

2008

rr_AnnualReturn2008

2.32%

2009

rr_AnnualReturn2009

8.24%

2010

rr_AnnualReturn2010

4.79%

2011

rr_AnnualReturn2011

0.60%

2012

rr_AnnualReturn2012

4.08%

2013

rr_AnnualReturn2013

1.22%

2014

rr_AnnualReturn2014

1.01%

2015

rr_AnnualReturn2015

(0.59%)

2016

rr_AnnualReturn2016

2.67%

2017

rr_AnnualReturn2017

1.22%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Best Quarter:

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

2.87%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Worst Quarter:

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2011

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(1.94%)

Franklin Investors Securities Trust - FIST2-24 | Franklin Low Duration Total Return Fund | Class C

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as percentage of offering price)

rr_MaximumCumulativeSalesChargeOverOfferingPrice

none

Maximum Deferred Sales Charge (Load) (as percentage of the lower of original purchase price or sale proceeds)

rr_MaximumDeferredSalesChargeOverOfferingPrice

1.00%

Management fees

rr_ManagementFeesOverAssets

0.50%

Distribution and service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

0.65%

Other expenses

rr_OtherExpensesOverAssets

0.20%

^[2]

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.02%

Total annual Fund operating expenses

rr_ExpensesOverAssets

1.37%

^[2]

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.26%)

^[3]

Total annual Fund operating expenses after fee waiver and/or expense reimbursement

rr_NetExpensesOverAssets

1.11%

^[2],[3]

1 year

rr_ExpenseExampleYear01

$ 213

3 years

rr_ExpenseExampleYear03

408

5 years

rr_ExpenseExampleYear05

725

10 years

rr_ExpenseExampleYear10

1,625

1 Year

rr_ExpenseExampleNoRedemptionYear01

113

3 Years

rr_ExpenseExampleNoRedemptionYear03

408

5 Years

rr_ExpenseExampleNoRedemptionYear05

725

10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 1,625

Franklin Investors Securities Trust - FIST2-24 | Franklin Low Duration Total Return Fund | Class R6

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as percentage of offering price)

rr_MaximumCumulativeSalesChargeOverOfferingPrice

none

Maximum Deferred Sales Charge (Load) (as percentage of the lower of original purchase price or sale proceeds)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

Management fees

rr_ManagementFeesOverAssets

0.50%

Distribution and service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.05%

^[2]

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.02%

Total annual Fund operating expenses

rr_ExpensesOverAssets

0.57%

^[2]

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.26%)

^[3]

Total annual Fund operating expenses after fee waiver and/or expense reimbursement

rr_NetExpensesOverAssets

0.31%

^[2],[3]

1 year

rr_ExpenseExampleYear01

$ 32

3 years

rr_ExpenseExampleYear03

156

5 years

rr_ExpenseExampleYear05

293

10 years

rr_ExpenseExampleYear10

$ 689

Franklin Investors Securities Trust - FIST2-24 | Franklin Low Duration Total Return Fund | Advisor Class

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as percentage of offering price)

rr_MaximumCumulativeSalesChargeOverOfferingPrice

none

Maximum Deferred Sales Charge (Load) (as percentage of the lower of original purchase price or sale proceeds)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

Management fees

rr_ManagementFeesOverAssets

0.50%

Distribution and service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.20%

^[2]

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.02%

Total annual Fund operating expenses

rr_ExpensesOverAssets

0.72%

^[2]

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.26%)

^[3]

Total annual Fund operating expenses after fee waiver and/or expense reimbursement

rr_NetExpensesOverAssets

0.46%

^[2],[3]

1 year

rr_ExpenseExampleYear01

$ 47

3 years

rr_ExpenseExampleYear03

204

5 years

rr_ExpenseExampleYear05

375

10 years

rr_ExpenseExampleYear10

$ 871

Franklin Investors Securities Trust - FIST2-24 | Franklin Low Duration Total Return Fund | Return Before Taxes | Class A

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Franklin Low Duration Total Return Fund

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

Past 1 year

rr_AverageAnnualReturnYear01

(1.09%)

Past 5 years

rr_AverageAnnualReturnYear05

0.63%

Past 10 years

rr_AverageAnnualReturnYear10

2.29%

Franklin Investors Securities Trust - FIST2-24 | Franklin Low Duration Total Return Fund | Return Before Taxes | Class C

Risk/Return:

rr_RiskReturnAbstract

Past 1 year

rr_AverageAnnualReturnYear01

(0.19%)

Past 5 years

rr_AverageAnnualReturnYear05

0.68%

Past 10 years

rr_AverageAnnualReturnYear10

2.10%

Franklin Investors Securities Trust - FIST2-24 | Franklin Low Duration Total Return Fund | Return Before Taxes | Class R6

Risk/Return:

rr_RiskReturnAbstract

Past 1 year

rr_AverageAnnualReturnYear01

1.55%

Past 10 years

rr_AverageAnnualReturnYear10

Since Inception

rr_AverageAnnualReturnSinceInception

1.38%

^[4]

Franklin Investors Securities Trust - FIST2-24 | Franklin Low Duration Total Return Fund | Return Before Taxes | Advisor Class

Risk/Return:

rr_RiskReturnAbstract

Past 1 year

rr_AverageAnnualReturnYear01

1.52%

Past 5 years

rr_AverageAnnualReturnYear05

1.34%

Past 10 years

rr_AverageAnnualReturnYear10

2.78%

Franklin Investors Securities Trust - FIST2-24 | Franklin Low Duration Total Return Fund | After Taxes on Distributions | Class A

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Franklin Low Duration Total Return Fund

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

Past 1 year

rr_AverageAnnualReturnYear01

(1.87%)

Past 5 years

rr_AverageAnnualReturnYear05

(0.25%)

Past 10 years

rr_AverageAnnualReturnYear10

1.26%

Franklin Investors Securities Trust - FIST2-24 | Franklin Low Duration Total Return Fund | After Taxes on Distributions and Sales | Class A

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Franklin Low Duration Total Return Fund

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

Past 1 year

rr_AverageAnnualReturnYear01

(0.62%)

Past 5 years

rr_AverageAnnualReturnYear05

0.08%

Past 10 years

rr_AverageAnnualReturnYear10

1.35%

Franklin Investors Securities Trust - FIST2-24 | Franklin Low Duration Total Return Fund | Bloomberg Barclays U.S. Government & Credit (1-3 Year) Index (index reflects no deduction for fees, expenses or taxes)

Risk/Return:

rr_RiskReturnAbstract

Past 1 year

rr_AverageAnnualReturnYear01

0.84%

Past 5 years

rr_AverageAnnualReturnYear05

0.84%

Past 10 years

rr_AverageAnnualReturnYear10

1.85%

[1] There is a 0.75% contingent deferred sales charge that applies to investments of $1 million or more (see“Investments of $1 Million or More” under “Choosing a Share Class”) and purchases by certain retirement plans without an initial sales charge on shares sold within 18 months of purchase.

[2] Other expenses of the Fund have been restated to exclude non-recurring prior period expenses and for Class R6 shares, to reflect current fiscal year expenses. If the non-recurring prior period expenses were included in the table above, the amounts stated would have been greater. Consequently, the total annual Fund operating expenses differ from the ratio of expenses to average net assets shown in the Financial Highlights.

[3] The investment manager has contractually agreed to waive or assume certain expenses so that common expenses (excluding the Rule 12b-1 fees, acquired fund fees and expenses and certain non-routine expenses) for each class of the Fund do not exceed 0.44% until February 28, 2019. The investment manager also has contractually agreed in advance to reduce its fees as a result of the Fund's investments in Franklin Templeton affiliated funds (acquired funds) for the next 12-month period. Contractual fee waiver and/or expense reimbursement agreements may not be changed or terminated during the time period set forth above.

[4] Since inception May 1, 2013.

XML

Fund Summary

Franklin Investors Securities Trust - FIST2-24 | Franklin Total Return Fund

Investment Goal

High current income, consistent with preservation of capital. As a secondary goal, capital appreciation over the long term.

Fees and Expenses of the Fund

These tables describe the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts in Class A if you and your family invest, or agree to invest in the future, at least $100,000 in Franklin Templeton funds. More information about these and other discounts is available from your financial professional and under “Your Account” on page 139 in the Fund's Prospectus and under “Buying and Selling Shares” on page 85 of the Fund’s Statement of Additional Information. In addition, more information about sales charge discounts and waivers for purchases of shares through specific financial intermediaries is set forth in Appendix A – "Intermediary Sales Charge Discounts and Waivers" to the Fund’s prospectus.

Please note that the tables and examples below do not reflect any transaction fees that may be charged by financial intermediaries, or commissions that a shareholder may be required to pay directly to its financial intermediary when buying or selling Class R6 or Advisor Class shares.

Shareholder Fees (fees paid directly from your investment)

Shareholder Fees {- Franklin Total Return Fund} - Franklin Investors Securities Trust - FIST2-24 - Franklin Total Return Fund	Class A		Class C	Class R	Class R6	Advisor Class
Maximum Sales Charge (Load) Imposed on Purchases (as percentage of offering price)	4.25%		none	none	none	none
Maximum Deferred Sales Charge (Load) (as percentage of the lower of original purchase price or sale proceeds)	none	[1]	1.00%	none	none	none

Annual Fund Operating Expenses

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

Annual Operating Expenses {- Franklin Total Return Fund} - Franklin Investors Securities Trust - FIST2-24 - Franklin Total Return Fund		Class A	Class C	Class R	Class R6	Advisor Class
Management fees		0.47%	0.47%	0.47%	0.47%	0.47%
Distribution and service (12b-1) fees		0.25%	0.65%	0.50%	none	none
Other expenses	[1]	0.19%	0.19%	0.19%	0.05%	0.19%
Acquired fund fees and expenses	[2]	0.02%	0.02%	0.02%	0.02%	0.02%
Total annual Fund operating expenses	[2]	0.93%	1.33%	1.18%	0.54%	0.68%
Fee waiver and/or expense reimbursement	[3]	(0.03%)	(0.03%)	(0.03%)	(0.03%)	(0.03%)
Total annual Fund operating expenses after fee waiver and/or expense reimbursement	[2],[3]	0.90%	1.30%	1.15%	0.51%	0.65%

Example

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of the period. The Example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same. The Example reflects adjustments made to the Fund's operating expenses due to the fee waivers and/or expense reimbursements by management for the 1 Year numbers only. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example {- Franklin Total Return Fund} - Franklin Investors Securities Trust - FIST2-24 - Franklin Total Return Fund - USD ($)	Class A	Class C	Class R	Class R6	Advisor Class
1 year	$ 513	$ 232	$ 117	$ 52	$ 66
3 years	706	418	372	170	215
5 years	915	726	646	299	376
10 years	$ 1,517	$ 1,600	$ 1,430	$ 675	$ 844

If you do not sell your shares:

Expense Example, No Redemption {- Franklin Total Return Fund}	Franklin Investors Securities Trust - FIST2-24 Franklin Total Return Fund Class C USD ($)
1 Year	$ 132
3 Years	418
5 Years	726
10 Years	$ 1,600

Portfolio Turnover

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 78.46% of the average value of its portfolio.

Principal Investment Strategies

Under normal market conditions, the Fund invests primarily in debt securities, which may be represented by derivative investments that provide exposure to debt securities such as futures, options and swap agreements. The debt securities in which the Fund may invest include government and corporate debt securities, mortgage- and asset-backed securities, floating interest rate corporate loans and debt securities and municipal securities. The Fund currently focuses on government and corporate debt securities and mortgage- and asset-backed securities.

Effective May 1, 2018, under normal market conditions, the Fund invests primarily in investment grade debt securities and in unrated securities that the investment manager deems are of comparable quality. Prior to this date, under normal market conditions, the Fund invests at least 80% of its assets in investment grade debt securities and investments. Derivatives whose reference securities are investment grade are considered by the Fund to be investment grade. The Fund's focus on the credit quality of its portfolio is intended to reduce credit risk and help to preserve the Fund's capital.

The Fund also may invest up to 20% of its total assets in non-investment grade securities, including up to 5% in securities rated lower than B- by S&P or Moody's, which may include defaulted securities. (In calculating the above non-investment grade debt limitations, the Fund combines its non-investment grade debt securities with the net long and short exposure to non-investment grade debt securities from derivative instruments.) Excluding derivatives, the Fund will invest no more than 33% of its total assets in non-investment grade debt securities, including no more than 5% in securities rated lower than B- by S&P or Moody's, which may include defaulted securities. For purposes of the credit limitations above, non-investment grade debt securities include unrated securities that the investment manager deems are of comparable quality.

The Fund may invest up to 25% of its total assets in foreign securities, including up to 20% of its total assets in non-U.S. dollar denominated securities and up to 10% of its total assets in emerging market securities.

The Fund may invest a small portion of its assets in marketplace loans to consumers and small and mid-sized enterprises or companies (SMEs) originated through online lending platforms.

The Fund may invest in many different securities issued or guaranteed by the U.S. government or by non-U.S. governments, or their respective agencies or instrumentalities, including mortgage-backed securities and inflation-indexed securities issued by the U.S. Treasury. Mortgage-backed securities represent an interest in a pool of mortgage loans made by banks and other financial institutions to finance purchases of homes, commercial buildings and other real estate. The individual mortgage loans are packaged or "pooled" together for sale to investors. As the underlying mortgage loans are paid off, investors receive principal and interest payments. These securities may be fixed-rate or adjustable-rate mortgage-backed securities (ARMS). The Fund may purchase or sell mortgage-backed securities on a delayed delivery or forward commitment basis through the "to-be-announced" (TBA) market. With TBA transactions, the particular securities to be delivered must meet specified terms and standards. The Fund may also invest a small portion of its assets directly in mortgage loans.

To pursue its investment goals, the Fund regularly enters into various derivative transactions, including currency forwards, currency, interest rate/bond futures contracts and options on interest rate futures contracts, and swap agreements, including interest rate, fixed income total return, currency and credit default swaps, and options on interest rate and credit default swap agreements. The use of these derivative transactions may allow the Fund to obtain net long or short exposures to select currencies, interest rates, countries, duration or credit risks. These derivatives may be used to enhance Fund returns, increase liquidity, gain exposure to certain instruments or markets in a more efficient or less expensive way and/or hedge risks associated with its other portfolio investments.

The Fund may invest in mortgage dollar rolls. In a mortgage dollar roll, the Fund sells mortgage-backed securities for delivery in the current month and simultaneously contracts to repurchase substantially similar (same type, coupon, and maturity) securities on a specified future date. During the period between the sale and repurchase, the Fund forgoes principal and interest paid on the mortgage-backed securities. The Fund earns money on a mortgage dollar roll from any difference between the sale price and the future purchase price, as well as the interest earned on the cash proceeds of the initial sale.

In choosing investments, the Fund’s investment manager selects securities in various market sectors based on the investment manager’s assessment of changing economic, market, industry and issuer conditions. The investment manager uses a “top-down” analysis of macroeconomic trends, combined with a “bottom-up” fundamental analysis of market sectors, industries and issuers, to try to take advantage of varying sector reactions to economic events.

Principal Risks

You could lose money by investing in the Fund. Mutual fund shares are not deposits or obligations of, or guaranteed or endorsed by, any bank, and are not insured by the Federal Deposit Insurance Corporation, the Federal Reserve Board, or any other agency of the U.S. government.

Interest Rate

When interest rates rise, debt security prices generally fall. The opposite is also generally true: debt security prices rise when interest rates fall. Interest rate changes are influenced by a number of factors, including government policy, monetary policy, inflation expectations, perceptions of risk, and supply and demand of bonds. In general, fixed rate securities with longer maturities or durations are more sensitive to interest rate changes.

Credit

An issuer of debt securities may fail to make interest payments or repay principal when due, in whole or in part. Changes in an issuer's financial strength or in a security's credit rating may affect a security's value.

High-Yield Debt Securities

Issuers of lower-rated or “high-yield” debt securities (also known as “junk bonds”) are not as strong financially as those issuing higher credit quality debt securities. High-yield debt securities are generally considered predominantly speculative by the applicable rating agencies as their issuers are more likely to encounter financial difficulties because they may be more highly leveraged, or because of other considerations. In addition, high yield debt securities generally are more vulnerable to changes in the relevant economy, such as a recession or a sustained period of rising interest rates, that could affect their ability to make interest and principal payments when due. The prices of high-yield debt securities generally fluctuate more than those of higher credit quality. High-yield debt securities are generally more illiquid (harder to sell) and harder to value.

Floating Rate Corporate Investments

Floating rate corporate loans and corporate debt securities generally have credit ratings below investment grade and may be subject to resale restrictions. They are often issued in connection with highly leveraged transactions, and may be subject to greater credit risks than other investments including the possibility of default or bankruptcy. In addition, a secondary market in corporate loans may be subject to irregular trading activity, wide bid/ask spreads and extended trade settlement periods, which may impair the ability to accurately value existing and prospective investments and to realize in a timely fashion the full value on sale of a corporate loan. A significant portion of floating rate investments may be “covenant lite” loans that may contain fewer or less restrictive constraints on the borrower or other borrower-friendly characteristics.

Derivative Instruments

The performance of derivative instruments depends largely on the performance of an underlying instrument, such as a currency, security, interest rate or index, and such instruments often have risks similar to the underlying instrument, in addition to other risks. Derivatives involve costs and can create economic leverage in the Fund’s portfolio which may result in significant volatility and cause the Fund to participate in losses (as well as gains) in an amount that exceeds the Fund’s initial investment. Other risks include illiquidity, mispricing or improper valuation of the derivative instrument, and imperfect correlation between the value of the derivative and the underlying instrument so that the Fund may not realize the intended benefits. When a derivative is used for hedging, the change in value of the derivative may also not correlate specifically with the currency, security, interest rate, index or other risk being hedged. Derivatives also may present the risk that the other party to the transaction will fail to perform.

Income

Because the Fund can only distribute what it earns, the Fund's distributions to shareholders may decline when prevailing interest rates fall, when the Fund experiences defaults on debt securities it holds, or when the Fund realizes a loss upon the sale of a debt security.

Mortgage Securities and Asset-Backed Securities

Mortgage securities differ from conventional debt securities because principal is paid back periodically over the life of the security rather than at maturity. The Fund may receive unscheduled payments of principal due to voluntary prepayments, refinancings or foreclosures on the underlying mortgage loans. Because of prepayments, mortgage securities may be less effective than some other types of debt securities as a means of "locking in" long-term interest rates and may have less potential for capital appreciation during periods of falling interest rates. A reduction in the anticipated rate of principal prepayments, especially during periods of rising interest rates, may increase or extend the effective maturity of mortgage securities, making them more sensitive to interest rate changes, subject to greater price volatility, and more susceptible than some other debt securities to a decline in market value when interest rates rise.

Issuers of asset-backed securities may have limited ability to enforce the security interest in the underlying assets, and credit enhancements provided to support the securities, if any, may be inadequate to protect investors in the event of default. Like mortgage securities, asset-backed securities are subject to prepayment and extension risks.

Foreign Securities (non U.S.)

Investing in foreign securities typically involves more risks than investing in U.S. securities, including risks related to currency exchange rates and policies, country or government specific issues, less favorable trading practices or regulation and greater price volatility. Certain of these risks also may apply to securities of U.S. companies with significant foreign operations.

Currency Management Strategies

Currency management strategies may substantially change the Fund’s exposure to currency exchange rates and could result in losses to the Fund if currencies do not perform as the investment manager expects. In addition, currency management strategies, to the extent that they reduce the Fund’s exposure to currency risks, may also reduce the Fund’s ability to benefit from favorable changes in currency exchange rates. Using currency management strategies for purposes other than hedging further increases the Fund’s exposure to foreign investment losses. Currency markets generally are not as regulated as securities markets. In addition, currency rates may fluctuate significantly over short periods of time, and can reduce returns.

Sovereign Debt Securities

Sovereign debt securities are subject to various risks in addition to those relating to debt securities and foreign investments generally, including, but not limited to, the risk that a governmental entity may be unwilling or unable to pay interest and repay principal on its sovereign debt, or otherwise meet its obligations when due because of cash flow problems, insufficient foreign reserves, the relative size of the debt service burden to the economy as a whole, the government’s policy towards principal international lenders such as the International Monetary Fund, or the political considerations to which the government may be subject. If a sovereign debtor defaults (or threatens to default) on its sovereign debt obligations, the indebtedness may be restructured. Some sovereign debtors have in the past been able to restructure their debt payments without the approval of some or all debt holders or to declare moratoria on payments. In the event of a default on sovereign debt, the Fund may also have limited legal recourse against the defaulting government entity.

Emerging Market Countries

The Fund’s investments in emerging market countries are subject to all of the risks of foreign investing generally, and have additional heightened risks due to a lack of established legal, political, business and social frameworks to support securities and currency markets, including: delays in settling portfolio transactions; currency and capital controls; greater sensitivity to interest rate changes; pervasiveness of corruption and crime; currency exchange rate volatility; and inflation, deflation or currency devaluation.

Extension

Some debt securities, particularly mortgage-backed securities, are subject to the risk that the debt security’s effective maturity is extended because calls or prepayments are less or slower than anticipated, particularly when interest rates rise. The market value of such security may then decline and become more interest rate sensitive.

Prepayment

Prepayment risk occurs when a debt security can be repaid in whole or in part prior to the security's maturity and the Fund must reinvest the proceeds it receives, during periods of declining interest rates, in securities that pay a lower rate of interest. Also, if a security has been purchased at a premium, the value of the premium would be lost in the event of prepayment. Prepayments generally increase when interest rates fall.

Mortgage Dollar Rolls

In a mortgage dollar roll, the Fund takes the risk that: the market price of the mortgage-backed securities will drop below their future repurchase price; the securities that it repurchases at a later date will have less favorable market characteristics; the other party to the agreement will not be able to perform; the roll adds leverage to the Fund's portfolio; and, it increases the Fund's sensitivity to interest rate changes. In addition, investment in mortgage dollar rolls may increase the portfolio turnover rate for the Fund.

Marketplace Loans

Marketplace loans are subject to the risks associated with debt investments generally, including but not limited to, interest rate, credit, liquidity, high yield debt, market and income risks. Marketplace loans generally are not rated by rating agencies, are often unsecured, and are highly risky and speculative investments. Lenders and investors, such as the Fund, assume all of the credit risk on the loans they fund or purchase and there are no assurances that payments due on underlying loans will be made. In addition, investments in marketplace loans may be adversely affected if the platform operator or a third-party service provider becomes unable or unwilling to fulfill its obligations in servicing the loans. Moreover, the Fund may have limited information about the underlying marketplace loans and information provided to the platform regarding the loans and the borrowers’ credit information may be incomplete, inaccurate or outdated. It also may be difficult for the Fund to sell an investment in a marketplace loan before maturity at the price at which the Fund believes the loan should be valued because these loans typically are considered by the Fund to be illiquid securities.

Liquidity

From time to time, the trading market for a particular security or type of security or other investments in which the Fund invests may become less liquid or even illiquid. Reduced liquidity will have an adverse impact on the Fund’s ability to sell such securities or other investments when necessary to meet the Fund’s liquidity needs, in response to a specific economic event or to buy particular securities to invest available cash or when considered advantageous by the investment manager. Reduced liquidity will also generally lower the value of such securities or other investments. Market prices for such securities or other investments may be volatile.

Variable Rate Securities

Because changes in interest rates on variable rate securities (including floating rate securities) may lag behind changes in market rates, the value of such securities may decline during periods of rising interest rates until their interest rates reset to market rates. During periods of declining interest rates, because the interest rates on variable rate securities generally reset downward, their market value is unlikely to rise to the same extent as the value of comparable fixed rate securities.

Market

The market values of securities or other investments owned by the Fund will go up or down, sometimes rapidly or unpredictably. The market value of a security or other investment may be reduced by market activity or other results of supply and demand unrelated to the issuer. This is a basic risk associated with all investments. When there are more sellers than buyers, prices tend to fall. Likewise, when there are more buyers than sellers, prices tend to rise.

Management

The Fund is subject to management risk because it is an actively managed investment portfolio. The Fund's investment manager applies investment techniques and risk analyses in making investment decisions for the Fund, but there can be no guarantee that these decisions will produce the desired results.

Portfolio turnover

The investment manager will sell a security when it believes it is appropriate to do so, regardless of how long the Fund has held the security. The Fund's turnover rate may exceed 100% per year because of the anticipated use of certain investment strategies. The rate of portfolio turnover will not be a limiting factor for the investment manager in making decisions on when to buy or sell securities, including entering into mortgage dollar rolls. High turnover will increase the Fund's transaction costs and may increase your tax liability if the transactions result in capital gains.

Performance

The following bar chart and table provide some indication of the risks of investing in the Fund. The bar chart shows changes in the Fund's performance from year to year for Class A shares. The table shows how the Fund's average annual returns for 1 year, 5 years, 10 years or since inception, as applicable, compared with those of a broad measure of market performance. The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You can obtain updated performance information at franklintempleton.com or by calling (800) DIAL BEN/342-5236.

Sales charges are not reflected in the bar chart, and if those charges were included, returns would be less than those shown.

Class A Annual Total Returns

Best Quarter:	Q3'09	6.20%
Worst Quarter:	Q3'08	-4.05%

Average Annual Total Returns
(figures reflect sales charges)

For the periods ended December 31, 2017

Average Annual Total Returns{- Franklin Total Return Fund} - Franklin Investors Securities Trust - FIST2-24 - Franklin Total Return Fund	Past 1 year	Past 5 years	Past 10 years	Since Inception	[1]
Class A | Return Before Taxes	(0.88%)	1.02%	3.75%
Class A | After Taxes on Distributions	(1.79%)	(0.26%)	2.13%
Class A | After Taxes on Distributions and Sales	(0.50%)	0.18%	2.24%
Class C | Return Before Taxes	2.15%	1.50%	3.78%
Class R | Return Before Taxes	3.25%	1.66%	3.94%
Class R6 | Return Before Taxes	3.91%			2.04%
Advisor Class | Return Before Taxes	3.70%	2.16%	4.46%
Bloomberg Barclays U.S. Aggregate Index (index reflects no deduction for fees, expenses or taxes)	3.54%	2.10%	4.00%

The after-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns are shown only for Class A and after-tax returns for other classes will vary.

[1] There is a 0.75% contingent deferred sales charge that applies to investments of $1 million or more (see“Investments of $1 Million or More” under “Choosing a Share Class”) and purchases by certain retirement plans without an initial sales charge on shares sold within 18 months of purchase.

[1] Other expenses for Class R6 shares have been restated to reflect current fiscal year expenses.

[2] Total annual Fund operating expenses differ from the ratio of expenses to average net assets shown in the Financial Highlights, which reflect the operating expenses of the Fund and do not include acquired fund fees and expenses.

[3] The investment manager has contractually agreed to waive or assume certain expenses so that total annual Fund operating expenses (excluding the Rule 12b-1 fees, acquired fund fees and expenses and certain non-routine expenses) for each class of the Fund do not exceed 0.63% through February 28, 2019. The investment manager also has contractually agreed in advance to reduce its fees as a result of the Fund's investments in Franklin Templeton affiliated funds (acquired funds) for the next 12-month period. Contractual fee waiver and/or expense reimbursement agreements may not be changed or terminated during the time period set forth above.

[1] Since inception May 1, 2013.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

FRANKLIN INVESTORS SECURITIES TRUST

Prospectus Date

rr_ProspectusDate

Sep. 04, 2018

Risk/Return [Heading]

rr_RiskReturnHeading

Fund Summary

Franklin Investors Securities Trust - FIST2-24 | Franklin Total Return Fund

Risk/Return:

rr_RiskReturnAbstract

Objective [Heading]

rr_ObjectiveHeading

Investment Goal

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

High current income, consistent with preservation of capital. As a secondary goal, capital appreciation over the long term.

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses of the Fund

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

These tables describe the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts in Class A if you and your family invest, or agree to invest in the future, at least $100,000 in Franklin Templeton funds. More information about these and other discounts is available from your financial professional and under “Your Account” on page 139 in the Fund's Prospectus and under “Buying and Selling Shares” on page 85 of the Fund’s Statement of Additional Information. In addition, more information about sales charge discounts and waivers for purchases of shares through specific financial intermediaries is set forth in Appendix A – "Intermediary Sales Charge Discounts and Waivers" to the Fund’s prospectus.

Please note that the tables and examples below do not reflect any transaction fees that may be charged by financial intermediaries, or commissions that a shareholder may be required to pay directly to its financial intermediary when buying or selling Class R6 or Advisor Class shares.

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder Fees (fees paid directly from your investment)

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses

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

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

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 78.46% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

78.46%

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may qualify for sales charge discounts in Class A if you and your family invest, or agree to invest in the future, at least $100,000 in Franklin Templeton funds.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

$ 100,000

Expense Example [Heading]

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Example

Expense Example Narrative [Text Block]

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This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of the period. The Example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same. The Example reflects adjustments made to the Fund's operating expenses due to the fee waivers and/or expense reimbursements by management for the 1 Year numbers only. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example, No Redemption, By Year, Caption [Text]

rr_ExpenseExampleNoRedemptionByYearCaption

If you do not sell your shares:

Strategy [Heading]

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Principal Investment Strategies

Strategy Narrative [Text Block]

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Under normal market conditions, the Fund invests primarily in debt securities, which may be represented by derivative investments that provide exposure to debt securities such as futures, options and swap agreements. The debt securities in which the Fund may invest include government and corporate debt securities, mortgage- and asset-backed securities, floating interest rate corporate loans and debt securities and municipal securities. The Fund currently focuses on government and corporate debt securities and mortgage- and asset-backed securities.

Effective May 1, 2018, under normal market conditions, the Fund invests primarily in investment grade debt securities and in unrated securities that the investment manager deems are of comparable quality. Prior to this date, under normal market conditions, the Fund invests at least 80% of its assets in investment grade debt securities and investments. Derivatives whose reference securities are investment grade are considered by the Fund to be investment grade. The Fund's focus on the credit quality of its portfolio is intended to reduce credit risk and help to preserve the Fund's capital.

The Fund also may invest up to 20% of its total assets in non-investment grade securities, including up to 5% in securities rated lower than B- by S&P or Moody's, which may include defaulted securities. (In calculating the above non-investment grade debt limitations, the Fund combines its non-investment grade debt securities with the net long and short exposure to non-investment grade debt securities from derivative instruments.) Excluding derivatives, the Fund will invest no more than 33% of its total assets in non-investment grade debt securities, including no more than 5% in securities rated lower than B- by S&P or Moody's, which may include defaulted securities. For purposes of the credit limitations above, non-investment grade debt securities include unrated securities that the investment manager deems are of comparable quality.

The Fund may invest up to 25% of its total assets in foreign securities, including up to 20% of its total assets in non-U.S. dollar denominated securities and up to 10% of its total assets in emerging market securities.

The Fund may invest a small portion of its assets in marketplace loans to consumers and small and mid-sized enterprises or companies (SMEs) originated through online lending platforms.

The Fund may invest in many different securities issued or guaranteed by the U.S. government or by non-U.S. governments, or their respective agencies or instrumentalities, including mortgage-backed securities and inflation-indexed securities issued by the U.S. Treasury. Mortgage-backed securities represent an interest in a pool of mortgage loans made by banks and other financial institutions to finance purchases of homes, commercial buildings and other real estate. The individual mortgage loans are packaged or "pooled" together for sale to investors. As the underlying mortgage loans are paid off, investors receive principal and interest payments. These securities may be fixed-rate or adjustable-rate mortgage-backed securities (ARMS). The Fund may purchase or sell mortgage-backed securities on a delayed delivery or forward commitment basis through the "to-be-announced" (TBA) market. With TBA transactions, the particular securities to be delivered must meet specified terms and standards. The Fund may also invest a small portion of its assets directly in mortgage loans.

To pursue its investment goals, the Fund regularly enters into various derivative transactions, including currency forwards, currency, interest rate/bond futures contracts and options on interest rate futures contracts, and swap agreements, including interest rate, fixed income total return, currency and credit default swaps, and options on interest rate and credit default swap agreements. The use of these derivative transactions may allow the Fund to obtain net long or short exposures to select currencies, interest rates, countries, duration or credit risks. These derivatives may be used to enhance Fund returns, increase liquidity, gain exposure to certain instruments or markets in a more efficient or less expensive way and/or hedge risks associated with its other portfolio investments.

The Fund may invest in mortgage dollar rolls. In a mortgage dollar roll, the Fund sells mortgage-backed securities for delivery in the current month and simultaneously contracts to repurchase substantially similar (same type, coupon, and maturity) securities on a specified future date. During the period between the sale and repurchase, the Fund forgoes principal and interest paid on the mortgage-backed securities. The Fund earns money on a mortgage dollar roll from any difference between the sale price and the future purchase price, as well as the interest earned on the cash proceeds of the initial sale.

In choosing investments, the Fund’s investment manager selects securities in various market sectors based on the investment manager’s assessment of changing economic, market, industry and issuer conditions. The investment manager uses a “top-down” analysis of macroeconomic trends, combined with a “bottom-up” fundamental analysis of market sectors, industries and issuers, to try to take advantage of varying sector reactions to economic events.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

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You could lose money by investing in the Fund. Mutual fund shares are not deposits or obligations of, or guaranteed or endorsed by, any bank, and are not insured by the Federal Deposit Insurance Corporation, the Federal Reserve Board, or any other agency of the U.S. government.

Interest Rate

When interest rates rise, debt security prices generally fall. The opposite is also generally true: debt security prices rise when interest rates fall. Interest rate changes are influenced by a number of factors, including government policy, monetary policy, inflation expectations, perceptions of risk, and supply and demand of bonds. In general, fixed rate securities with longer maturities or durations are more sensitive to interest rate changes.

Credit

An issuer of debt securities may fail to make interest payments or repay principal when due, in whole or in part. Changes in an issuer's financial strength or in a security's credit rating may affect a security's value.

High-Yield Debt Securities

Issuers of lower-rated or “high-yield” debt securities (also known as “junk bonds”) are not as strong financially as those issuing higher credit quality debt securities. High-yield debt securities are generally considered predominantly speculative by the applicable rating agencies as their issuers are more likely to encounter financial difficulties because they may be more highly leveraged, or because of other considerations. In addition, high yield debt securities generally are more vulnerable to changes in the relevant economy, such as a recession or a sustained period of rising interest rates, that could affect their ability to make interest and principal payments when due. The prices of high-yield debt securities generally fluctuate more than those of higher credit quality. High-yield debt securities are generally more illiquid (harder to sell) and harder to value.

Floating Rate Corporate Investments

Floating rate corporate loans and corporate debt securities generally have credit ratings below investment grade and may be subject to resale restrictions. They are often issued in connection with highly leveraged transactions, and may be subject to greater credit risks than other investments including the possibility of default or bankruptcy. In addition, a secondary market in corporate loans may be subject to irregular trading activity, wide bid/ask spreads and extended trade settlement periods, which may impair the ability to accurately value existing and prospective investments and to realize in a timely fashion the full value on sale of a corporate loan. A significant portion of floating rate investments may be “covenant lite” loans that may contain fewer or less restrictive constraints on the borrower or other borrower-friendly characteristics.

Derivative Instruments

The performance of derivative instruments depends largely on the performance of an underlying instrument, such as a currency, security, interest rate or index, and such instruments often have risks similar to the underlying instrument, in addition to other risks. Derivatives involve costs and can create economic leverage in the Fund’s portfolio which may result in significant volatility and cause the Fund to participate in losses (as well as gains) in an amount that exceeds the Fund’s initial investment. Other risks include illiquidity, mispricing or improper valuation of the derivative instrument, and imperfect correlation between the value of the derivative and the underlying instrument so that the Fund may not realize the intended benefits. When a derivative is used for hedging, the change in value of the derivative may also not correlate specifically with the currency, security, interest rate, index or other risk being hedged. Derivatives also may present the risk that the other party to the transaction will fail to perform.

Income

Because the Fund can only distribute what it earns, the Fund's distributions to shareholders may decline when prevailing interest rates fall, when the Fund experiences defaults on debt securities it holds, or when the Fund realizes a loss upon the sale of a debt security.

Mortgage Securities and Asset-Backed Securities

Mortgage securities differ from conventional debt securities because principal is paid back periodically over the life of the security rather than at maturity. The Fund may receive unscheduled payments of principal due to voluntary prepayments, refinancings or foreclosures on the underlying mortgage loans. Because of prepayments, mortgage securities may be less effective than some other types of debt securities as a means of "locking in" long-term interest rates and may have less potential for capital appreciation during periods of falling interest rates. A reduction in the anticipated rate of principal prepayments, especially during periods of rising interest rates, may increase or extend the effective maturity of mortgage securities, making them more sensitive to interest rate changes, subject to greater price volatility, and more susceptible than some other debt securities to a decline in market value when interest rates rise.

Issuers of asset-backed securities may have limited ability to enforce the security interest in the underlying assets, and credit enhancements provided to support the securities, if any, may be inadequate to protect investors in the event of default. Like mortgage securities, asset-backed securities are subject to prepayment and extension risks.

Foreign Securities (non U.S.)

Investing in foreign securities typically involves more risks than investing in U.S. securities, including risks related to currency exchange rates and policies, country or government specific issues, less favorable trading practices or regulation and greater price volatility. Certain of these risks also may apply to securities of U.S. companies with significant foreign operations.

Currency Management Strategies

Currency management strategies may substantially change the Fund’s exposure to currency exchange rates and could result in losses to the Fund if currencies do not perform as the investment manager expects. In addition, currency management strategies, to the extent that they reduce the Fund’s exposure to currency risks, may also reduce the Fund’s ability to benefit from favorable changes in currency exchange rates. Using currency management strategies for purposes other than hedging further increases the Fund’s exposure to foreign investment losses. Currency markets generally are not as regulated as securities markets. In addition, currency rates may fluctuate significantly over short periods of time, and can reduce returns.

Sovereign Debt Securities

Sovereign debt securities are subject to various risks in addition to those relating to debt securities and foreign investments generally, including, but not limited to, the risk that a governmental entity may be unwilling or unable to pay interest and repay principal on its sovereign debt, or otherwise meet its obligations when due because of cash flow problems, insufficient foreign reserves, the relative size of the debt service burden to the economy as a whole, the government’s policy towards principal international lenders such as the International Monetary Fund, or the political considerations to which the government may be subject. If a sovereign debtor defaults (or threatens to default) on its sovereign debt obligations, the indebtedness may be restructured. Some sovereign debtors have in the past been able to restructure their debt payments without the approval of some or all debt holders or to declare moratoria on payments. In the event of a default on sovereign debt, the Fund may also have limited legal recourse against the defaulting government entity.

Emerging Market Countries

The Fund’s investments in emerging market countries are subject to all of the risks of foreign investing generally, and have additional heightened risks due to a lack of established legal, political, business and social frameworks to support securities and currency markets, including: delays in settling portfolio transactions; currency and capital controls; greater sensitivity to interest rate changes; pervasiveness of corruption and crime; currency exchange rate volatility; and inflation, deflation or currency devaluation.

Extension

Some debt securities, particularly mortgage-backed securities, are subject to the risk that the debt security’s effective maturity is extended because calls or prepayments are less or slower than anticipated, particularly when interest rates rise. The market value of such security may then decline and become more interest rate sensitive.

Prepayment

Prepayment risk occurs when a debt security can be repaid in whole or in part prior to the security's maturity and the Fund must reinvest the proceeds it receives, during periods of declining interest rates, in securities that pay a lower rate of interest. Also, if a security has been purchased at a premium, the value of the premium would be lost in the event of prepayment. Prepayments generally increase when interest rates fall.

Mortgage Dollar Rolls

In a mortgage dollar roll, the Fund takes the risk that: the market price of the mortgage-backed securities will drop below their future repurchase price; the securities that it repurchases at a later date will have less favorable market characteristics; the other party to the agreement will not be able to perform; the roll adds leverage to the Fund's portfolio; and, it increases the Fund's sensitivity to interest rate changes. In addition, investment in mortgage dollar rolls may increase the portfolio turnover rate for the Fund.

Marketplace Loans

Marketplace loans are subject to the risks associated with debt investments generally, including but not limited to, interest rate, credit, liquidity, high yield debt, market and income risks. Marketplace loans generally are not rated by rating agencies, are often unsecured, and are highly risky and speculative investments. Lenders and investors, such as the Fund, assume all of the credit risk on the loans they fund or purchase and there are no assurances that payments due on underlying loans will be made. In addition, investments in marketplace loans may be adversely affected if the platform operator or a third-party service provider becomes unable or unwilling to fulfill its obligations in servicing the loans. Moreover, the Fund may have limited information about the underlying marketplace loans and information provided to the platform regarding the loans and the borrowers’ credit information may be incomplete, inaccurate or outdated. It also may be difficult for the Fund to sell an investment in a marketplace loan before maturity at the price at which the Fund believes the loan should be valued because these loans typically are considered by the Fund to be illiquid securities.

Liquidity

From time to time, the trading market for a particular security or type of security or other investments in which the Fund invests may become less liquid or even illiquid. Reduced liquidity will have an adverse impact on the Fund’s ability to sell such securities or other investments when necessary to meet the Fund’s liquidity needs, in response to a specific economic event or to buy particular securities to invest available cash or when considered advantageous by the investment manager. Reduced liquidity will also generally lower the value of such securities or other investments. Market prices for such securities or other investments may be volatile.

Variable Rate Securities

Because changes in interest rates on variable rate securities (including floating rate securities) may lag behind changes in market rates, the value of such securities may decline during periods of rising interest rates until their interest rates reset to market rates. During periods of declining interest rates, because the interest rates on variable rate securities generally reset downward, their market value is unlikely to rise to the same extent as the value of comparable fixed rate securities.

Market

The market values of securities or other investments owned by the Fund will go up or down, sometimes rapidly or unpredictably. The market value of a security or other investment may be reduced by market activity or other results of supply and demand unrelated to the issuer. This is a basic risk associated with all investments. When there are more sellers than buyers, prices tend to fall. Likewise, when there are more buyers than sellers, prices tend to rise.

Management

The Fund is subject to management risk because it is an actively managed investment portfolio. The Fund's investment manager applies investment techniques and risk analyses in making investment decisions for the Fund, but there can be no guarantee that these decisions will produce the desired results.

Portfolio turnover

The investment manager will sell a security when it believes it is appropriate to do so, regardless of how long the Fund has held the security. The Fund's turnover rate may exceed 100% per year because of the anticipated use of certain investment strategies. The rate of portfolio turnover will not be a limiting factor for the investment manager in making decisions on when to buy or sell securities, including entering into mortgage dollar rolls. High turnover will increase the Fund's transaction costs and may increase your tax liability if the transactions result in capital gains.

Bar Chart and Performance Table [Heading]

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Performance

Performance Narrative [Text Block]

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The following bar chart and table provide some indication of the risks of investing in the Fund. The bar chart shows changes in the Fund's performance from year to year for Class A shares. The table shows how the Fund's average annual returns for 1 year, 5 years, 10 years or since inception, as applicable, compared with those of a broad measure of market performance. The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. You can obtain updated performance information at franklintempleton.com or by calling (800) DIAL BEN/342-5236.

Sales charges are not reflected in the bar chart, and if those charges were included, returns would be less than those shown.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The following bar chart and table provide some indication of the risks of investing in the Fund. The bar chart shows changes in the Fund's performance from year to year for Class A shares. The table shows how the Fund's average annual returns for 1 year, 5 years, 10 years or since inception, as applicable, compared with those of a broad measure of market performance.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

(800) DIAL BEN/342-5236

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

franklintempleton.com

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

The Fund's past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future.

Bar Chart [Heading]

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Class A Annual Total Returns

Bar Chart Does Not Reflect Sales Loads [Text]

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Sales charges are not reflected in the bar chart, and if those charges were included, returns would be less than those shown.

Bar Chart Closing [Text Block]

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Best Quarter:	Q3'09	6.20%
Worst Quarter:	Q3'08	-4.05%

Performance Table Heading

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Average Annual Total Returns
(figures reflect sales charges)

For the periods ended December 31, 2017

Performance Table Closing [Text Block]

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The after-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns are shown only for Class A and after-tax returns for other classes will vary.

Franklin Investors Securities Trust - FIST2-24 | Franklin Total Return Fund | Class A

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as percentage of offering price)

rr_MaximumCumulativeSalesChargeOverOfferingPrice

4.25%

Maximum Deferred Sales Charge (Load) (as percentage of the lower of original purchase price or sale proceeds)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

^[1]

Management fees

rr_ManagementFeesOverAssets

0.47%

Distribution and service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.19%

^[2]

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.02%

^[3]

Total annual Fund operating expenses

rr_ExpensesOverAssets

0.93%

^[3]

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.03%)

^[4]

Total annual Fund operating expenses after fee waiver and/or expense reimbursement

rr_NetExpensesOverAssets

0.90%

^[3],[4]

1 year

rr_ExpenseExampleYear01

$ 513

3 years

rr_ExpenseExampleYear03

706

5 years

rr_ExpenseExampleYear05

915

10 years

rr_ExpenseExampleYear10

$ 1,517

2008

rr_AnnualReturn2008

(5.48%)

2009

rr_AnnualReturn2009

15.39%

2010

rr_AnnualReturn2010

10.13%

2011

rr_AnnualReturn2011

5.53%

2012

rr_AnnualReturn2012

8.33%

2013

rr_AnnualReturn2013

(0.98%)

2014

rr_AnnualReturn2014

5.98%

2015

rr_AnnualReturn2015

(1.59%)

2016

rr_AnnualReturn2016

2.80%

2017

rr_AnnualReturn2017

3.53%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Best Quarter:

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

6.20%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Worst Quarter:

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2008

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(4.05%)

Franklin Investors Securities Trust - FIST2-24 | Franklin Total Return Fund | Class C

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as percentage of offering price)

rr_MaximumCumulativeSalesChargeOverOfferingPrice

none

Maximum Deferred Sales Charge (Load) (as percentage of the lower of original purchase price or sale proceeds)

rr_MaximumDeferredSalesChargeOverOfferingPrice

1.00%

Management fees

rr_ManagementFeesOverAssets

0.47%

Distribution and service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

0.65%

Other expenses

rr_OtherExpensesOverAssets

0.19%

^[2]

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.02%

^[3]

Total annual Fund operating expenses

rr_ExpensesOverAssets

1.33%

^[3]

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.03%)

^[4]

Total annual Fund operating expenses after fee waiver and/or expense reimbursement

rr_NetExpensesOverAssets

1.30%

^[3],[4]

1 year

rr_ExpenseExampleYear01

$ 232

3 years

rr_ExpenseExampleYear03

418

5 years

rr_ExpenseExampleYear05

726

10 years

rr_ExpenseExampleYear10

1,600

1 Year

rr_ExpenseExampleNoRedemptionYear01

132

3 Years

rr_ExpenseExampleNoRedemptionYear03

418

5 Years

rr_ExpenseExampleNoRedemptionYear05

726

10 Years

rr_ExpenseExampleNoRedemptionYear10

$ 1,600

Franklin Investors Securities Trust - FIST2-24 | Franklin Total Return Fund | Class R

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as percentage of offering price)

rr_MaximumCumulativeSalesChargeOverOfferingPrice

none

Maximum Deferred Sales Charge (Load) (as percentage of the lower of original purchase price or sale proceeds)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

Management fees

rr_ManagementFeesOverAssets

0.47%

Distribution and service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

0.50%

Other expenses

rr_OtherExpensesOverAssets

0.19%

^[2]

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.02%

^[3]

Total annual Fund operating expenses

rr_ExpensesOverAssets

1.18%

^[3]

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.03%)

^[4]

Total annual Fund operating expenses after fee waiver and/or expense reimbursement

rr_NetExpensesOverAssets

1.15%

^[3],[4]

1 year

rr_ExpenseExampleYear01

$ 117

3 years

rr_ExpenseExampleYear03

372

5 years

rr_ExpenseExampleYear05

646

10 years

rr_ExpenseExampleYear10

$ 1,430

Franklin Investors Securities Trust - FIST2-24 | Franklin Total Return Fund | Class R6

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as percentage of offering price)

rr_MaximumCumulativeSalesChargeOverOfferingPrice

none

Maximum Deferred Sales Charge (Load) (as percentage of the lower of original purchase price or sale proceeds)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

Management fees

rr_ManagementFeesOverAssets

0.47%

Distribution and service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.05%

^[2]

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.02%

^[3]

Total annual Fund operating expenses

rr_ExpensesOverAssets

0.54%

^[3]

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.03%)

^[4]

Total annual Fund operating expenses after fee waiver and/or expense reimbursement

rr_NetExpensesOverAssets

0.51%

^[3],[4]

1 year

rr_ExpenseExampleYear01

$ 52

3 years

rr_ExpenseExampleYear03

170

5 years

rr_ExpenseExampleYear05

299

10 years

rr_ExpenseExampleYear10

$ 675

Franklin Investors Securities Trust - FIST2-24 | Franklin Total Return Fund | Advisor Class

Risk/Return:

rr_RiskReturnAbstract

Maximum Sales Charge (Load) Imposed on Purchases (as percentage of offering price)

rr_MaximumCumulativeSalesChargeOverOfferingPrice

none

Maximum Deferred Sales Charge (Load) (as percentage of the lower of original purchase price or sale proceeds)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

Management fees

rr_ManagementFeesOverAssets

0.47%

Distribution and service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.19%

^[2]

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.02%

^[3]

Total annual Fund operating expenses

rr_ExpensesOverAssets

0.68%

^[3]

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.03%)

^[4]

Total annual Fund operating expenses after fee waiver and/or expense reimbursement

rr_NetExpensesOverAssets

0.65%

^[3],[4]

1 year

rr_ExpenseExampleYear01

$ 66

3 years

rr_ExpenseExampleYear03

215

5 years

rr_ExpenseExampleYear05

376

10 years

rr_ExpenseExampleYear10

$ 844

Franklin Investors Securities Trust - FIST2-24 | Franklin Total Return Fund | Return Before Taxes | Class A

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Franklin Total Return Fund

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

Past 1 year

rr_AverageAnnualReturnYear01

(0.88%)

Past 5 years

rr_AverageAnnualReturnYear05

1.02%

Past 10 years

rr_AverageAnnualReturnYear10

3.75%

Franklin Investors Securities Trust - FIST2-24 | Franklin Total Return Fund | Return Before Taxes | Class C

Risk/Return:

rr_RiskReturnAbstract

Past 1 year

rr_AverageAnnualReturnYear01

2.15%

Past 5 years

rr_AverageAnnualReturnYear05

1.50%

Past 10 years

rr_AverageAnnualReturnYear10

3.78%

Franklin Investors Securities Trust - FIST2-24 | Franklin Total Return Fund | Return Before Taxes | Class R

Risk/Return:

rr_RiskReturnAbstract

Past 1 year

rr_AverageAnnualReturnYear01

3.25%

Past 5 years

rr_AverageAnnualReturnYear05

1.66%

Past 10 years

rr_AverageAnnualReturnYear10

3.94%

Franklin Investors Securities Trust - FIST2-24 | Franklin Total Return Fund | Return Before Taxes | Class R6

Risk/Return:

rr_RiskReturnAbstract

Past 1 year

rr_AverageAnnualReturnYear01

3.91%

Past 10 years

rr_AverageAnnualReturnYear10

Since Inception

rr_AverageAnnualReturnSinceInception

2.04%

^[5]

Franklin Investors Securities Trust - FIST2-24 | Franklin Total Return Fund | Return Before Taxes | Advisor Class

Risk/Return:

rr_RiskReturnAbstract

Past 1 year

rr_AverageAnnualReturnYear01

3.70%

Past 5 years

rr_AverageAnnualReturnYear05

2.16%

Past 10 years

rr_AverageAnnualReturnYear10

4.46%

Franklin Investors Securities Trust - FIST2-24 | Franklin Total Return Fund | After Taxes on Distributions | Class A

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Franklin Total Return Fund

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

Past 1 year

rr_AverageAnnualReturnYear01

(1.79%)

Past 5 years

rr_AverageAnnualReturnYear05

(0.26%)

Past 10 years

rr_AverageAnnualReturnYear10

2.13%

Franklin Investors Securities Trust - FIST2-24 | Franklin Total Return Fund | After Taxes on Distributions and Sales | Class A

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Franklin Total Return Fund

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

Past 1 year

rr_AverageAnnualReturnYear01

(0.50%)

Past 5 years

rr_AverageAnnualReturnYear05

0.18%

Past 10 years

rr_AverageAnnualReturnYear10

2.24%

Franklin Investors Securities Trust - FIST2-24 | Franklin Total Return Fund | Bloomberg Barclays U.S. Aggregate Index (index reflects no deduction for fees, expenses or taxes)

Risk/Return:

rr_RiskReturnAbstract

Past 1 year

rr_AverageAnnualReturnYear01

3.54%

Past 5 years

rr_AverageAnnualReturnYear05

2.10%

Past 10 years

rr_AverageAnnualReturnYear10

4.00%

[1] There is a 0.75% contingent deferred sales charge that applies to investments of $1 million or more (see“Investments of $1 Million or More” under “Choosing a Share Class”) and purchases by certain retirement plans without an initial sales charge on shares sold within 18 months of purchase.

[2] Other expenses for Class R6 shares have been restated to reflect current fiscal year expenses.

[3] Total annual Fund operating expenses differ from the ratio of expenses to average net assets shown in the Financial Highlights, which reflect the operating expenses of the Fund and do not include acquired fund fees and expenses.

[4] The investment manager has contractually agreed to waive or assume certain expenses so that total annual Fund operating expenses (excluding the Rule 12b-1 fees, acquired fund fees and expenses and certain non-routine expenses) for each class of the Fund do not exceed 0.63% through February 28, 2019. The investment manager also has contractually agreed in advance to reduce its fees as a result of the Fund's investments in Franklin Templeton affiliated funds (acquired funds) for the next 12-month period. Contractual fee waiver and/or expense reimbursement agreements may not be changed or terminated during the time period set forth above.

[5] Since inception May 1, 2013.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	FRANKLIN INVESTORS SECURITIES TRUST
Prospectus Date	rr_ProspectusDate	Sep. 04, 2018
Document Creation Date	dei_DocumentCreationDate	Jun. 22, 2017