S000003879 [Member] Investment Risks - Putnam VT Emerging Markets Equity Fund	Dec. 31, 2025
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. Growth stocks may be more susceptible to earnings disappointments, and value stocks may fail to rebound. These risks are generally greater for small and midsize companies.
Geographic focus risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Geographic focus risk: Investments focused in a single region may be affected by common economic forces and other factors. In addition, events in any one country within the region may impact the other countries or the region as a whole. From time to time, the fund may invest a significant portion of its assets in companies in one or more related industries or sectors, such as Asian or Pacific Basin countries, which would make the fund more vulnerable to adverse developments affecting those regions, industries or sectors.
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.
Derivatives risks [Member]
Prospectus [Line Items]
Risk [Text Block]	Derivatives risk: The fund’s use of derivatives may increase the risks of investing in the fund by increasing investment exposure (which may be considered leverage) or, in the case of many over-the-counter instruments, because of the potential inability to terminate or sell derivative positions and the potential failure of the other party to the instrument to meet its obligations. The risk of a party failing to meet its obligations may increase if the fund has significant exposure to that counterparty. The value of derivatives may move in unexpected ways due to unanticipated market movements, the use of leverage, imperfect correlation between the derivative instrument and the reference asset, or other factors, especially in unusual market conditions, and volatility in the value of derivatives could adversely impact the fund’s returns, obligations and exposures. Derivatives are also subject to other risks, including liquidity risk (e.g., liquidity demands arising from the requirement to make payments to a derivative counterparty), operational risk (e.g., settlement issues or system failures) and legal risk (e.g., insufficient legal documentation or contract enforceability issues).
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.
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.
Risk Nondiversified Status [Member]
Prospectus [Line Items]
Risk [Text Block]	Non-diversified fund risk: The fund’s “non-diversified” status, which means the fund may invest a greater percentage of its assets in fewer issuers than a “diversified” fund, can increase the fund’s vulnerability to adverse developments affecting a single industry, country or issuer, which may result in greater losses and volatility for the fund.

S000003879 [Member] Investment Risks - Putnam VT Emerging Markets Equity Fund

Dec. 31, 2025

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. Growth stocks may be more susceptible to earnings disappointments, and value stocks may fail to rebound. These risks are generally greater for small and midsize companies.

Prospectus [Line Items]

Risk [Text Block]

Geographic focus risk: Investments focused in a single region may be affected by common economic forces and other factors. In addition, events in any one country within the region may impact the other countries or the region as a whole. From time to time, the fund may invest a significant portion of its assets in companies in one or more related industries or sectors, such as Asian or Pacific Basin countries, which would make the fund more vulnerable to adverse developments affecting those regions, industries or sectors.

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.

Derivatives risks [Member]

Prospectus [Line Items]

Risk [Text Block]

Derivatives risk: The fund’s use of derivatives may increase the risks of investing in the fund by increasing investment exposure (which may be considered leverage) or, in the case of many over-the-counter instruments, because of the potential inability to terminate or sell derivative positions and the potential failure of the other party to the instrument to meet its obligations.

The risk of a party failing to meet its obligations may increase if the fund has significant exposure to that counterparty. The value of derivatives may move in unexpected ways due to unanticipated market movements, the use of leverage, imperfect correlation between the derivative instrument and the reference asset, or other factors, especially in unusual market conditions, and volatility in the value of derivatives could adversely impact the fund’s returns, obligations and exposures. Derivatives are also subject to other risks, including liquidity risk (e.g., liquidity demands arising from the requirement to make payments to a derivative counterparty), operational risk (e.g., settlement issues or system failures) and legal risk (e.g., insufficient legal documentation or contract enforceability issues).

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.

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.

Risk Nondiversified Status [Member]

Prospectus [Line Items]

Risk [Text Block]

Non-diversified fund risk: The fund’s “non-diversified” status, which means the fund may invest a greater percentage of its assets in fewer issuers than a “diversified” fund, can increase the fund’s vulnerability to adverse developments affecting a single industry, country or issuer, which may result in greater losses and volatility for the fund.