v3.26.1
S000003881 [Member] Investment Risks - Putnam VT Sustainable Future Fund
Dec. 31, 2025
Foreign investments risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
Foreign investments risk: The value of international investments traded in foreign currencies may be adversely impacted by fluctuations in exchange rates. International investments, particularly investments in emerging markets, may carry risks associated with potentially less stable economies or governments (such as the risk of seizure by a foreign government, the imposition of economic sanctions or currency or other restrictions, or high levels of inflation), and may be or become illiquid.
Common stock risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
Common stock risk: Common stock represents an ownership interest in a company. The value of a company’s stock may fall or fail to rise as a result of factors directly relating to that company, such as decisions made by its management or lower demand for the company’s products or services. A stock’s value may also fall because of factors affecting not just the company, but also other companies in the same industry or in a number of different industries, such as increases in production costs.
The value of a company’s stock may also be affected by changes in financial markets that are relatively unrelated to the company or its industry, such as changes in interest rates, currency exchange rates, or inflation rates.
Growth stocks may be more susceptible to earnings disappointments and the market may not favor growth-style investing. These risks are generally greater for small and midsized companies. From time to time, the fund may invest a significant portion of its assets in companies in one or more related industries or sectors, which would make the fund more vulnerable to adverse developments affecting those industries or sectors.
Sustainable investing risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
Sustainable investing risk: Investing with a focus on Solutions Companies, whose products and services may provide solutions that directly impact sustainable environmental, social and economic development, may result in the fund investing in certain types of companies, industries or sectors that the market may not favor. In evaluating an investment opportunity, the Investment Manager may make investment decisions without the availability of optimal ESG-related data or based on information and data that is incomplete or inaccurate. Sustainability and ESG factors are not uniformly defined and applying such factors involves subjective assessments. Sustainability and ESG scorings and assessments of issuers can vary across third-party data providers and may change over time. The Investment Manager does not rely exclusively on third party data providers in evaluating ESG criteria. ESG information from third party providers may be incomplete, inaccurate or unavailable. In addition, a solutions company’s business practices, products or services may change over time. As a result of these possibilities, among others, the fund may temporarily hold securities that are inconsistent with the Investment Manager’s sustainable investment criteria. Regulatory changes or interpretations regarding the definitions and/or use of ESG or other sustainability criteria could have a material adverse effect on the fund’s ability to invest in accordance with its investment policies and/or achieve its investment objective, as well as the ability of certain classes of investors to invest in funds, such as the fund, whose strategies include ESG or other sustainability criteria.
Large shareholder transaction risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
Large shareholder transaction risk: The fund is subject to the risk that shareholders will purchase or redeem large quantities of shares of the fund. 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. In addition, a large number of shareholders may collectively purchase or redeem fund shares in large amounts rapidly or unexpectedly. Large shareholder transactions may adversely affect the fund’s liquidity and net assets. These redemptions may also adversely affect the fund’s performance if the fund is forced to sell securities, which may also increase the fund’s brokerage costs.
Liquidity and illiquid investments risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
Liquidity and illiquid investments risk: The fund may invest up to 15% of its net assets in illiquid investments, which may be considered speculative and which may be difficult to sell. The fund may not be able to sell its illiquid investments when the Investment Manager considers it desirable to do so, or the fund may be able to sell them only at less than their value.
Management and operational risk [Member]  
Prospectus [Line Items]  
Risk [Text Block]
Management and operational risk: There is no guarantee that the investment techniques, analyses, or judgments that the Investment Manager applies in making investment decisions for the fund will produce the intended outcome or that the investments selected for the fund will perform as well as other securities that were not selected for the fund. The Investment Manager, or the fund’s other service providers, may experience disruptions or operating errors that could negatively impact the fund.
Market risks [Member]  
Prospectus [Line Items]  
Risk [Text Block]
Market risk: 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.
Risk Lose Money [Member]  
Prospectus [Line Items]  
Risk [Text Block]
It is important to understand that you can lose money by investing in the fund.
Risk Not Insured [Member]  
Prospectus [Line Items]  
Risk [Text Block] An investment in the fund is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.