As a non-diversified fund concentrating in the health care industries, the fund invests mainly in common stocks (growth or value stocks or both) of large and midsize companies worldwide that the Investment Manager, as defined below, believes have favorable investment potential. Under normal circumstances, the fund invests at least 80% of its net assets in securities of companies in the health care industries. This policy may be changed only after 60 days’ notice to shareholders. Potential investments include companies that manufacture health care supplies or provide health care-related services, and companies in the research, development, production and marketing of pharmaceuticals and biotechnology products. The fund may purchase stocks of companies with stock prices that reflect a value lower than that which that Investment Manager places on the company. The Investment Manager may consider, among other factors, a company’s valuation, financial strength, growth potential, competitive position in its industry, projected future earnings, cash flows and dividends when deciding whether to buy or sell investments. The Investment Manager may also consider other factors that it believes will cause the stock price to rise. The fund may also use derivatives, such as certain foreign currency transactions, futures, options, warrants and swap contracts, for both hedging and non-hedging purposes, and may engage in short sales of securities. For example, the fund typically uses foreign currency forward contracts in connection with the fund’s investments in foreign securities in order to hedge the fund’s currency exposure relative to the fund’s benchmark index.

The use of the term “global” in the fund’s name is meant to emphasize that the Investment Manager looks for investment opportunities on a worldwide basis and that the fund’s investment strategies are not constrained by the countries or regions in which companies are located. Under normal market conditions, the fund intends to invest in at least five different countries and at least 40% of its net assets in securities of foreign companies (or, if less, at least the percentage of net assets that is ten percentage points less than the percentage of the fund’s benchmark represented by foreign companies, as determined by the providers of the benchmark).

S000003874 [Member] Investment Strategy - Putnam VT Global Health Care Fund	Dec. 31, 2025
Prospectus [Line Items]
Strategy [Heading]	Investments, risks, and performance Investments
Strategy Narrative [Text Block]	As a non-diversified fund concentrating in the health care industries, the fund invests mainly in common stocks (growth or value stocks or both) of large and midsize companies worldwide that the Investment Manager, as defined below, believes have favorable investment potential. Under normal circumstances, the fund invests at least 80% of its net assets in securities of companies in the health care industries. This policy may be changed only after 60 days’ notice to shareholders. Potential investments include companies that manufacture health care supplies or provide health care-related services, and companies in the research, development, production and marketing of pharmaceuticals and biotechnology products. The fund may purchase stocks of companies with stock prices that reflect a value lower than that which that Investment Manager places on the company. The Investment Manager may consider, among other factors, a company’s valuation, financial strength, growth potential, competitive position in its industry, projected future earnings, cash flows and dividends when deciding whether to buy or sell investments. The Investment Manager may also consider other factors that it believes will cause the stock price to rise. The fund may also use derivatives, such as certain foreign currency transactions, futures, options, warrants and swap contracts, for both hedging and non-hedging purposes, and may engage in short sales of securities. For example, the fund typically uses foreign currency forward contracts in connection with the fund’s investments in foreign securities in order to hedge the fund’s currency exposure relative to the fund’s benchmark index. The use of the term “global” in the fund’s name is meant to emphasize that the Investment Manager looks for investment opportunities on a worldwide basis and that the fund’s investment strategies are not constrained by the countries or regions in which companies are located. Under normal market conditions, the fund intends to invest in at least five different countries and at least 40% of its net assets in securities of foreign companies (or, if less, at least the percentage of net assets that is ten percentage points less than the percentage of the fund’s benchmark represented by foreign companies, as determined by the providers of the benchmark).