S000003882 [Member] Investment Risks - Putnam VT Government Money Market Fund	Dec. 31, 2025
Interest Rate Risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Interest rate risk: The values of money market investments usually rise and fall in response to changes in interest rates. Interest rate risk is generally lowest for investments with short maturities (a significant part of the fund’s investments).
Credit quality risk [Member]
Prospectus [Line Items]
Risk [Text Block]	Credit quality risk: Changes in the financial condition of an issuer or counterparty, changes in specific economic or political conditions that affect a particular type of issuer, and changes in general economic or political conditions can increase the risk of default by an issuer or counterparty, which can affect a security’s or instrument’s credit quality or value. Certain securities in which the fund may invest, including securities issued by certain U.S. government agencies and U.S. government sponsored enterprises, are not guaranteed by the U.S. government or supported by the full faith and credit of the United States.
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. The fund may not achieve its goal, and it is not intended to be a complete investment program. You could lose money by investing in the fund. Although the fund seeks to preserve the value of your investment at $1.00 per share, it cannot guarantee it will do so. An investment in the fund is not a bank account and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. The fund’s sponsor is not required to reimburse the fund for losses, and you should not expect that the sponsor will provide financial support to the fund at any time, including during periods of market stress.
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 Depository Institution [Member]
Prospectus [Line Items]
Risk [Text Block]	An investment in the fund is not a bank account and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Risk Money Market Fund May Not Preserve Dollar [Member]
Prospectus [Line Items]
Risk [Text Block]	Although the fund seeks to preserve the value of your investment at $1.00 per share, it cannot guarantee it will do so.
Risk Money Market Fund Sponsor May Not Provide Support [Member]
Prospectus [Line Items]
Risk [Text Block]	The fund’s sponsor is not required to reimburse the fund for losses, and you should not expect that the sponsor will provide financial support to the fund at any time, including during periods of market stress.

S000003882 [Member] Investment Risks - Putnam VT Government Money Market Fund

Dec. 31, 2025

Interest rate risk: The values of money market investments usually rise and fall in response to changes in interest rates. Interest rate risk is generally lowest for investments with short maturities (a significant part of the fund’s investments).

Prospectus [Line Items]

Risk [Text Block]

Credit quality risk: Changes in the financial condition of an issuer or counterparty, changes in specific economic or political conditions that affect a particular type of issuer, and changes in general economic or political conditions can increase the risk of default by an issuer or counterparty, which can affect a security’s or instrument’s credit quality or value. Certain securities in which the fund may invest, including securities issued by certain U.S. government agencies and U.S. government sponsored enterprises, are not guaranteed by the U.S. government or supported by the full faith and credit of the United States.

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.

The fund may not achieve its goal, and it is not intended to be a complete investment program. You could lose money by investing in the fund. Although the fund seeks to preserve the value of your investment at $1.00 per share, it cannot guarantee it will do so. An investment in the fund is not a bank account and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. The fund’s sponsor is not required to reimburse the fund for losses, and you should not expect that the sponsor will provide financial support to the fund at any time, including during periods of market stress.

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 Depository Institution [Member]

Prospectus [Line Items]

Risk [Text Block]

An investment in the fund is not a bank account and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.

Risk Money Market Fund May Not Preserve Dollar [Member]

Prospectus [Line Items]

Risk [Text Block]

Although the fund seeks to preserve the value of your investment at $1.00 per share, it cannot guarantee it will do so.

Risk Money Market Fund Sponsor May Not Provide Support [Member]

Prospectus [Line Items]

Risk [Text Block]

The fund’s sponsor is not required to reimburse the fund for losses, and you should not expect that the sponsor will provide financial support to the fund at any time, including during periods of market stress.