Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

PUTNAM CONVERTIBLE SECURITIES FUND

Prospectus Date

rr_ProspectusDate

Feb. 28, 2015

Class I | PUTNAM CONVERTIBLE SECURITIES FUND

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

Fund summary

Objective [Heading]

rr_ObjectiveHeading

Goal

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

Putnam Convertible Securities Fund seeks, with equal emphasis, current income and capital appreciation.

Objective, Secondary [Text Block]

rr_ObjectiveSecondaryTextBlock

Its secondary objective is conservation of capital.

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The following table describes the fees and expenses you may pay if you buy and hold Class I shares of the fund.

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 63%.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

63.00%

Other Expenses, New Fund, Based on Estimates [Text]

rr_OtherExpensesNewFundBasedOnEstimates

Other expenses are based on estimated amounts for the current fiscal year.

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

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

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 (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.

Strategy Portfolio Concentration [Text]

rr_StrategyPortfolioConcentration

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.

Risk [Heading]

rr_RiskHeading

Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

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

The value of convertible securities in the fund's portfolio may fall or fail to rise over extended periods of time for a variety of reasons, including general financial market conditions, factors related to a specific company or industry, changing market perceptions of the risk of default and changes in government intervention in the financial markets. These factors may also lead to increased volatility and reduced liquidity in the markets for convertible securities. 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). 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.

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.

Risk Lose Money [Text]

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

Risk Not Insured Depository Institution [Text]

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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]

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Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The performance information below gives some indication of the risks associated with an investment in the fund by showing the fund’s performance year to year and over time. The performance shown is that of class Y shares of the fund, which are not offered in this prospectus, and this performance has not been adjusted to reflect the lower fees associated with class I shares of the fund. Please remember that past performance is not necessarily an indication of future results.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The performance information below gives some indication of the risks associated with an investment in the fund by showing the fund’s performance year to year and over time.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Please remember that past performance is not necessarily an indication of future results.

Bar Chart [Heading]

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Annual total returns for class I shares

Bar Chart Closing [Text Block]

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Best calendar quarter Q2 2009	19.23%
Worst calendar quarter Q4 2008	-25.93%

Bar Chart, Returns for Class Not Offered in Prospectus [Text]

rr_BarChartReturnsForClassNotOfferedInProspectus

The performance shown is that of class Y shares of the fund, which are not offered in this prospectus, and this performance has not been adjusted to reflect the lower fees associated with class I shares of the fund.

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Best calendar quarter

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

19.23%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Worst calendar quarter

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(25.93%)

Performance Table Heading

rr_PerformanceTableHeading

Average annual total returns after sales charges (for periods ending 12/31/14)

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

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Actual after-tax returns depend on an investor’s tax situation and may differ from those shown.

Performance Table Narrative

rr_PerformanceTableNarrativeTextBlock

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.

Class I | PUTNAM CONVERTIBLE SECURITIES FUND | Class I

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases (as a percentage of offering price)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, whichever is lower)

rr_MaximumDeferredSalesChargeOverOther

none

Management fees

rr_ManagementFeesOverAssets

0.62%

Distribution and service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.06%

^[1]

Total annual fund operating expenses

rr_ExpensesOverAssets

0.68%

1 year

rr_ExpenseExampleYear01

69

3 years

rr_ExpenseExampleYear03

218

2005

rr_AnnualReturn2005

2.27%

2006

rr_AnnualReturn2006

14.85%

2007

rr_AnnualReturn2007

6.21%

2008

rr_AnnualReturn2008

(39.30%)

2009

rr_AnnualReturn2009

54.13%

2010

rr_AnnualReturn2010

19.79%

2011

rr_AnnualReturn2011

(6.22%)

2012

rr_AnnualReturn2012

15.38%

2013

rr_AnnualReturn2013

22.27%

2014

rr_AnnualReturn2014

7.73%

1 year

rr_AverageAnnualReturnYear01

7.73%

5 years

rr_AverageAnnualReturnYear05

11.29%

10 years

rr_AverageAnnualReturnYear10

7.14%

Class I | PUTNAM CONVERTIBLE SECURITIES FUND | after taxes on distributions | Class I

Risk/Return:

rr_RiskReturnAbstract

1 year

rr_AverageAnnualReturnYear01

5.67%

5 years

rr_AverageAnnualReturnYear05

10.07%

10 years

rr_AverageAnnualReturnYear10

6.09%

Class I | PUTNAM CONVERTIBLE SECURITIES FUND | after taxes on distributions and sale of fund shares | Class I

Risk/Return:

rr_RiskReturnAbstract

1 year

rr_AverageAnnualReturnYear01

5.31%

5 years

rr_AverageAnnualReturnYear05

8.62%

10 years

rr_AverageAnnualReturnYear10

5.41%

Class I | PUTNAM CONVERTIBLE SECURITIES FUND | BofA Merrill Lynch All U.S. Convertibles Index (no deduction for fees, expenses or taxes)

Risk/Return:

rr_RiskReturnAbstract

1 year

rr_AverageAnnualReturnYear01

9.44%

5 years

rr_AverageAnnualReturnYear05

11.72%

10 years

rr_AverageAnnualReturnYear10

7.11%

[1] Other expenses are based on estimated amounts for the current fiscal year.