Label

Element

Value

Prospectus [Line Items]

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Document Type

dei_DocumentType

497

Document Period End Date

dei_DocumentPeriodEndDate

Dec. 31, 2023

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

Putnam Convertible Securities Fund

Prospectus [Line Items]

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Risk/Return [Heading]

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Prospectuses dated February 29, 2024

Strategy [Heading]

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Effective immediately, the sub-section Investments, risks, and performance – Investments in the section Fund summary is deleted in its entirety and replaced with the following:

Strategy Narrative [Text Block]

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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 fund invests significantly in convertible bonds that 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.