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Label Element Value
Prospectus [Line Items] rr_ProspectusLineItems  
Document Type dei_DocumentType 485BPOS
Document Period End Date dei_DocumentPeriodEndDate Dec. 31, 2024
Entity Registrant Name dei_EntityRegistrantName Putnam Convertible Securities Fund
Entity Central Index Key dei_EntityCentralIndexKey 0000081247
Entity Inv Company Type dei_EntityInvCompanyType N-1A
Amendment Flag dei_AmendmentFlag false
Prospectus 1 [Member] | Putnam Convertible Securities Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading Fund Summary
Objective [Heading] rr_ObjectiveHeading Goal
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The fund seeks, with equal emphasis, current income and capital appreciation. Its secondary objective is conservation of capital.
Expense [Heading] rr_ExpenseHeading Fees and expenses
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

The following tables describe the fees and expenses you may pay if you buy, hold and sell shares of the fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in Putnam funds. More information about these and other discounts is available from your financial professional and in How do I buy fund shares? beginning on page 18 of the fund’s prospectus, in the Appendix to the fund’s prospectus, and in How to buy shares beginning on page 17 of the fund’s statement of additional information (“SAI”).
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 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-related costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher turnover rate may indicate higher transaction costs and may result in higher taxes when the fund’s shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or the above example, affect fund performance. The fund’s turnover rate in the most recent fiscal year was 61%.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 61.00%
Expense Breakpoint Discounts [Text] rr_ExpenseBreakpointDiscounts You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in Putnam funds.
Expense Breakpoint, Minimum Investment Required [Amount] rr_ExpenseBreakpointMinimumInvestmentRequiredAmount $ 50,000
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

The following hypothetical example is intended to help you compare the cost of investing in the fund with the cost of investing in other funds. It assumes that you invest $10,000 in the fund for the time periods indicated and then, except as indicated, redeem all your shares at the end of those periods. It assumes a 5% return on your investment each year and that the fund’s operating expenses remain the same. Your actual costs may be higher or lower.

Strategy [Heading] rr_StrategyHeading Investments, risks, and performance
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

Investments

We invest mainly in convertible securities of U.S. companies. Under normal circumstances, we invest at least 80% of the fund’s net assets in convertible securities. This policy may be changed only after 60 days’ notice to shareholders. Convertible securities combine the investment characteristics of bonds and common stocks. Convertible securities include bonds, preferred stocks and other instruments that can be converted into or exchanged for common stock or equivalent value. A significant portion of the convertible securities we buy are below-investment-grade (sometimes referred to as “junk bonds”). The convertible bonds we buy usually have intermediate-to long-term stated maturities (i.e., three years or longer), but often contain “put” features, which allow bondholders to sell the bond back to the company under specified circumstances, that result in shorter effective maturities. When deciding whether to buy or sell investments, we may consider, among other factors: (i) a security’s structural features, such as its position in a company’s capital structure and “put” and “call” features (a company’s right to repurchase the security under specified circumstances is a “call” feature); (ii) credit and prepayment risks; and (iii) with respect to a company’s common stock underlying a convertible security, the stock’s valuation and the company’s financial strength, growth potential, competitive position in its industry, projected future earnings, cash flows and dividends.

Risk [Heading] rr_RiskHeading Risks
Risk [Text Block] rr_RiskTextBlock

It is important to understand that you can lose money by investing in the fund.

The value of investments in the fund’s portfolio may fall or fail to rise over extended periods of time for a variety of reasons, including general economic, political or financial market conditions, investor sentiment and market perceptions, government actions, geopolitical events or changes, outbreaks of infectious illnesses or other widespread public health issues, and factors related to a specific issuer, asset class, geography, industry or sector. These and other factors may lead to increased volatility and reduced liquidity in the fund’s portfolio holdings, may negatively impact the fund’s performance, and may exacerbate other risks to which the fund is subject.

These risks are generally greater for convertible securities issued by small and midsize companies (which may constitute a significant portion of the fund’s investments from time to time). The value of convertible securities may be adversely affected by changes in the prices of underlying common stocks. Convertible securities tend to provide higher yields than common stocks. However, a higher yield may not protect investors against the risk of loss or adequately mitigate any loss associated with a decline in the price of a convertible security. Convertible securities are subject to credit risk, which is the risk that an issuer of the fund’s investments may default on payment of interest or principal. Credit risk is generally greater for below-investment-grade convertible securities (a significant part of the fund’s investments), which can be more sensitive to changes in markets, credit conditions, and interest rates, and may be considered speculative. Generally, convertible securities may be less sensitive to interest rate changes than non-convertible bonds as a result of convertible securities’ convertibility and “put” features. Interest rate risk is generally greater for longer-term bonds and convertible securities whose underlying stock price has fallen significantly below the conversion price. Bond investments may be more susceptible to downgrades or defaults during economic downturns or other periods of economic stress.

The fund may be an investment option for mutual funds that are managed by the Investment Manager and its affiliates as “funds of funds.” Additionally, other investors from time to time may make substantial investments in the fund. Such shareholders may at times be considered to control the fund. Dispositions of a large number of shares by these shareholders may adversely affect the fund’s liquidity and net assets. These redemptions may also force the fund to sell securities, which may increase the fund’s brokerage costs.

There is no guarantee that the investment techniques, analyses, or judgments that we apply in making investment decisions for the fund will produce the intended outcome or that the investments we select for the fund will perform as well as other securities that were not selected for the fund. We, or the fund’s other service providers, may experience disruptions or operating errors that could negatively impact the fund.

The fund may not achieve its goal, and it is not intended to be a complete investment program. An investment in the fund is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.

Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The accompanying 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 the average annual total returns of each class of the fund that has been in operation for at least one full calendar year and also compares the fund’s performance with the average annual total returns of a broad measure of market performance and an additional index with characteristics relevant to the fund. Performance for classes other than those shown may vary from the performance shown to the extent the expenses for those classes differ. The fund makes updated performance information, including its current net asset value per share, available at www.franklintempleton.com.

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

Sales charges are not reflected in the accompanying 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 accompanying bar chart and table provide some indication of the risks of investing in the fund.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.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 Annual total returns for class A shares before sales charges
Bar Chart Does Not Reflect Sales Loads [Text] rr_BarChartDoesNotReflectSalesLoads Sales charges are not reflected in the accompanying bar chart, and if those charges were included, returns would be less than those shown.
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best calendar quarter
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2020
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 25.30%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst calendar quarter
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Jun. 30, 2022
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (15.22%)
Performance Table Heading rr_PerformanceTableHeading Average annual total returns after sales charges For periods ended 12/31/24
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns reflect the historical highest individual federal marginal income tax rates and do not reflect state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on an investor’s tax situation and may differ from those shown.
Performance Table One Class of after Tax Shown [Text] rr_PerformanceTableOneClassOfAfterTaxShown After-tax returns are shown for class A shares only and will vary for other classes.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock

After-tax returns reflect the historical highest individual federal marginal income tax rates and do not reflect 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 shown for class A shares only and will vary for other classes. These after-tax returns do not apply if you hold your fund shares through a 401(k) plan, an IRA, or another tax-advantaged arrangement.

Class C share performance reflects conversion to class A shares after eight years.

Important data provider notices and terms are available at www.franklintempletondatasources.com. All data is subject to change.
Prospectus 1 [Member] | Putnam Convertible Securities Fund | Bloomberg U.S. Aggregate Index (no deduction for fees, expenses or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.25%
5 Years rr_AverageAnnualReturnYear05 (0.33%)
10 Years rr_AverageAnnualReturnYear10 1.35%
Prospectus 1 [Member] | Putnam Convertible Securities Fund | ICE BofA U.S. Convertible Index (no deduction for fees, expenses or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 11.14%
5 Years rr_AverageAnnualReturnYear05 9.66%
10 Years rr_AverageAnnualReturnYear10 9.07%
Prospectus 1 [Member] | Putnam Convertible Securities Fund | Class A  
Prospectus [Line Items] rr_ProspectusLineItems  
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice 5.75%
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 1.00% [1]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.61%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.17%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.03%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 674
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 884
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 1,111
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,762
Annual Return 2015 rr_AnnualReturn2015 (7.03%)
Annual Return 2016 rr_AnnualReturn2016 9.51%
Annual Return 2017 rr_AnnualReturn2017 14.93%
Annual Return 2018 rr_AnnualReturn2018 (3.26%)
Annual Return 2019 rr_AnnualReturn2019 24.31%
Annual Return 2020 rr_AnnualReturn2020 44.97%
Annual Return 2021 rr_AnnualReturn2021 4.01%
Annual Return 2022 rr_AnnualReturn2022 (18.57%)
Annual Return 2023 rr_AnnualReturn2023 10.13%
Annual Return 2024 rr_AnnualReturn2024 12.60%
1 Year rr_AverageAnnualReturnYear01 6.12%
5 Years rr_AverageAnnualReturnYear05 7.49%
10 Years rr_AverageAnnualReturnYear10 7.28%
Prospectus 1 [Member] | Putnam Convertible Securities Fund | Class A | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 5.57%
5 Years rr_AverageAnnualReturnYear05 5.22%
10 Years rr_AverageAnnualReturnYear10 5.19%
Prospectus 1 [Member] | Putnam Convertible Securities Fund | Class A | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 3.72%
5 Years rr_AverageAnnualReturnYear05 5.43%
10 Years rr_AverageAnnualReturnYear10 5.22%
Prospectus 1 [Member] | Putnam Convertible Securities Fund | Class C  
Prospectus [Line Items] rr_ProspectusLineItems  
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther 1.00% [2]
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.61%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 1.00%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.17%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.78%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 281
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 560
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 964
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 1,897
Expense Example, No Redemption, 1 Year rr_ExpenseExampleNoRedemptionYear01 181
Expense Example, No Redemption, 3 Years rr_ExpenseExampleNoRedemptionYear03 560
Expense Example, No Redemption, 5 Years rr_ExpenseExampleNoRedemptionYear05 964
Expense Example, No Redemption, 10 Years rr_ExpenseExampleNoRedemptionYear10 $ 1,897
1 Year rr_AverageAnnualReturnYear01 10.79%
5 Years rr_AverageAnnualReturnYear05 7.96%
10 Years rr_AverageAnnualReturnYear10 7.27%
Prospectus 1 [Member] | Putnam Convertible Securities Fund | Class R  
Prospectus [Line Items] rr_ProspectusLineItems  
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.61%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.50%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.17%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.28%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 130
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 406
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 702
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,545
1 Year rr_AverageAnnualReturnYear01 12.32%
5 Years rr_AverageAnnualReturnYear05 8.50%
10 Years rr_AverageAnnualReturnYear10 7.65%
Prospectus 1 [Member] | Putnam Convertible Securities Fund | Class R6  
Prospectus [Line Items] rr_ProspectusLineItems  
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.61%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.11%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.72%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 74
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 230
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 401
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 894
1 Year rr_AverageAnnualReturnYear01 13.00% [3]
5 Years rr_AverageAnnualReturnYear05 9.11% [3]
10 Years rr_AverageAnnualReturnYear10 8.25% [3]
Prospectus 1 [Member] | Putnam Convertible Securities Fund | Class Y  
Prospectus [Line Items] rr_ProspectusLineItems  
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.61%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.17%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.78%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 80
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 249
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 433
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 966
1 Year rr_AverageAnnualReturnYear01 12.89%
5 Years rr_AverageAnnualReturnYear05 9.05%
10 Years rr_AverageAnnualReturnYear10 8.19%
Prospectus 1 [Member] | Putnam Convertible Securities Fund | Risk Lose Money [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock It is important to understand that you can lose money by investing in the fund.
Prospectus 1 [Member] | Putnam Convertible Securities Fund | Risk Not Insured Depository Institution [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock An investment in the fund is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Prospectus 2 [Member] | Putnam Convertible Securities Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk/Return [Heading] rr_RiskReturnHeading Fund Summary
Objective [Heading] rr_ObjectiveHeading Goal
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock

The fund seeks, with equal emphasis, current income and capital appreciation. Its secondary objective is conservation of capital.
Expense [Heading] rr_ExpenseHeading Fees and expenses
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock

The following tables describe the fees and expenses you may pay if you buy, hold and sell Class I shares of the fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below.

Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder fees (fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses 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-related costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher turnover rate may indicate higher transaction costs and may result in higher taxes when the fund’s shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or the above example, affect fund performance. The fund’s turnover rate in the most recent fiscal year was 61%.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 61.00%
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

The following hypothetical example is intended to help you compare the cost of investing in the fund with the cost of investing in other funds. It assumes that you invest $10,000 in the fund for the time periods indicated and then redeem all your shares at the end of those periods. It assumes a 5% return on your investment each year and that the fund’s operating expenses remain the same. Your actual costs may be higher or lower.

Strategy [Heading] rr_StrategyHeading Investments, risks, and performance
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

Investments

We invest mainly in convertible securities of U.S. companies. Under normal circumstances, we invest at least 80% of the fund’s net assets in convertible securities. This policy may be changed only after 60 days’ notice to shareholders. Convertible securities combine the investment characteristics of bonds and common stocks. Convertible securities include bonds, preferred stocks and other instruments that can be converted into or exchanged for common stock or equivalent value. A significant portion of the convertible securities we buy are below-investment-grade (sometimes referred to as “junk bonds”). The convertible bonds we buy usually have intermediate-to long-term stated maturities (i.e., three years or longer), but often contain “put” features, which allow bondholders to sell the bond back to the company under specified circumstances, that result in shorter effective maturities. When deciding whether to buy or sell investments, we may consider, among other factors: (i) a security’s structural features, such as its position in a company’s capital structure and “put” and “call” features (a company’s right to repurchase the security under specified circumstances is a “call” feature); (ii) credit and prepayment risks; and (iii) with respect to a company’s common stock underlying a convertible security, the stock’s valuation and the company’s financial strength, growth potential, competitive position in its industry, projected future earnings, cash flows and dividends.
Risk [Heading] rr_RiskHeading Risks
Risk [Text Block] rr_RiskTextBlock

It is important to understand that you can lose money by investing in the fund.

The value of investments in the fund’s portfolio may fall or fail to rise over extended periods of time for a variety of reasons, including general economic, political or financial market conditions, investor sentiment and market perceptions, government actions, geopolitical events or changes, outbreaks of infectious illnesses or other widespread public health issues, and factors related to a specific issuer, asset class, geography, industry or sector. These and other factors may lead to increased volatility and reduced liquidity in the fund’s portfolio holdings, may negatively impact the fund’s performance, and may exacerbate other risks to which the fund is subject.

These risks are generally greater for convertible securities issued by small and midsize companies (which may constitute a significant portion of the fund’s investments from time to time). The value of convertible securities may be adversely affected by changes in the prices of underlying common stocks. Convertible securities tend to provide higher yields than common stocks. However, a higher yield may not protect investors against the risk of loss or adequately mitigate any loss associated with a decline in the price of a convertible security. Convertible securities are subject to credit risk, which is the risk that an issuer of the fund’s investments may default on payment of interest or principal. Credit risk is generally greater for below-investment-grade convertible securities (a significant part of the fund’s investments), which can be more sensitive to changes in markets, credit conditions, and interest rates, and may be considered speculative. Generally, convertible securities may be less sensitive to interest rate changes than non-convertible bonds as a result of convertible securities’ convertibility and “put” features. Interest rate risk is generally greater for longer-term bonds and convertible securities whose underlying stock price has fallen significantly below the conversion price. Bond investments may be more susceptible to downgrades or defaults during economic downturns or other periods of economic stress.

The fund may be an investment option for mutual funds that are managed by the Investment Manager and its affiliates as “funds of funds.” Additionally, other investors from time to time may make substantial investments in the fund. Such shareholders may at times be considered to control the fund. Dispositions of a large number of shares by these shareholders may adversely affect the fund’s liquidity and net assets. These redemptions may also force the fund to sell securities, which may increase the fund’s brokerage costs.

There is no guarantee that the investment techniques, analyses, or judgments that we apply in making investment decisions for the fund will produce the intended outcome or that the investments we select for the fund will perform as well as other securities that were not selected for the fund. We, or the fund’s other service providers, may experience disruptions or operating errors that could negatively impact the fund.

The fund may not achieve its goal, and it is not intended to be a complete investment program. An investment in the fund is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.

Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock

The accompanying 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 I shares. The table shows the average annual total returns of Class I shares and also compares the fund’s performance with the average annual total returns of a broad measure of market performance and an additional index with characteristics relevant to the fund. Performance for classes other than those shown may vary from the performance shown to the extent the expenses for those classes differ. The fund makes updated performance information, including its current net asset value, available at www.franklintempleton.com.

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

Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The accompanying bar chart and table provide some indication of the risks of investing in the fund.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.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 Annual total returns for class I shares before sales charges
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Best calendar quarter
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Jun. 30, 2020
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 25.39%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Worst calendar quarter
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Jun. 30, 2022
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (15.16%)
Performance Table Heading rr_PerformanceTableHeading Average annual total returns after sales charges For periods ended 12/31/24
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns reflect the historical highest individual federal marginal income tax rates and do not reflect state and local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred Actual after-tax returns depend on an investor’s tax situation and may differ from those shown.
Performance Table Closing [Text Block] rr_PerformanceTableClosingTextBlock

After-tax returns reflect the historical highest individual federal marginal income tax rates and do not reflect state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown.

Important data provider notices and terms are available at www.franklintempletondatasources.com. All data is subject to change.
Prospectus 2 [Member] | Putnam Convertible Securities Fund | Bloomberg U.S. Aggregate Index (no deduction for fees, expenses or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 1.25%
5 Years rr_AverageAnnualReturnYear05 (0.33%)
10 Years rr_AverageAnnualReturnYear10 1.35%
Prospectus 2 [Member] | Putnam Convertible Securities Fund | ICE BofA U.S. Convertible Index (no deduction for fees, expenses or taxes)  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 11.14%
5 Years rr_AverageAnnualReturnYear05 9.66%
10 Years rr_AverageAnnualReturnYear10 9.07%
Prospectus 2 [Member] | Putnam Convertible Securities Fund | Class I  
Prospectus [Line Items] rr_ProspectusLineItems  
Maximum Sales Charge Imposed on Purchases (as a percentage of Offering Price) rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice none
Maximum Deferred Sales Charge (as a percentage) rr_MaximumDeferredSalesChargeOverOther none
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.61%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.07%
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.68%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 69
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 218
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 379
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 847
Annual Return 2015 rr_AnnualReturn2015 (6.69%)
Annual Return 2016 rr_AnnualReturn2016 9.95%
Annual Return 2017 rr_AnnualReturn2017 15.42%
Annual Return 2018 rr_AnnualReturn2018 (2.90%)
Annual Return 2019 rr_AnnualReturn2019 24.74%
Annual Return 2020 rr_AnnualReturn2020 45.55%
Annual Return 2021 rr_AnnualReturn2021 4.40%
Annual Return 2022 rr_AnnualReturn2022 (18.28%)
Annual Return 2023 rr_AnnualReturn2023 10.52%
Annual Return 2024 rr_AnnualReturn2024 13.01%
1 Year rr_AverageAnnualReturnYear01 13.01% [4]
5 Years rr_AverageAnnualReturnYear05 9.17% [4]
10 Years rr_AverageAnnualReturnYear10 8.32% [4]
Prospectus 2 [Member] | Putnam Convertible Securities Fund | Class I | After Taxes on Distributions  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 12.30%
5 Years rr_AverageAnnualReturnYear05 6.67%
10 Years rr_AverageAnnualReturnYear10 5.99%
Prospectus 2 [Member] | Putnam Convertible Securities Fund | Class I | After Taxes on Distributions and Sales  
Prospectus [Line Items] rr_ProspectusLineItems  
1 Year rr_AverageAnnualReturnYear01 7.82%
5 Years rr_AverageAnnualReturnYear05 6.65%
10 Years rr_AverageAnnualReturnYear10 5.93%
Prospectus 2 [Member] | Putnam Convertible Securities Fund | Risk Lose Money [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock It is important to understand that you can lose money by investing in the fund.
Prospectus 2 [Member] | Putnam Convertible Securities Fund | Risk Not Insured Depository Institution [Member]  
Prospectus [Line Items] rr_ProspectusLineItems  
Risk [Text Block] rr_RiskTextBlock An investment in the fund is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
[1] Applies only to certain redemptions of shares bought with no initial sales charge.
[2] This charge is eliminated after one year.
[3] Performance for class R6 shares prior to their inception (5/22/18) is derived from the historical performance of class Y and has not been adjusted for the lower investor servicing fees applicable to class R6 shares; had it been adjusted, returns would have been higher.
[4] Performance for class I shares prior to their inception (3/3/15) is derived from the historical performance of class Y and has not been adjusted for the lower investor servicing fees applicable to class I shares; had it been adjusted, returns would have been higher.