v3.26.1
S000003896 [Member] Average Annual Total Returns
 12 Months Ended 60 Months Ended 120 Months Ended
Dec. 31, 2025
Dec. 31, 2025
Dec. 31, 2025
Russell 3000 Index (no deduction for fees, expenses or taxes)      
Prospectus [Line Items]      
Average Annual Return, Percent 17.15% 13.15% 14.29%
Putnam VT Balanced Blended Benchmark (no deduction for fees, expenses or taxes, but, for the MSCI EAFE Index-NR, are net of dividend tax withholding)      
Prospectus [Line Items]      
Average Annual Return, Percent [1] 14.67% 7.63% 9.14%
Putnam Balanced Blended Benchmark (no deduction for fees, expenses or taxes, but, for the MSCI EAFE Index-NR, are net of dividend tax withholding)      
Prospectus [Line Items]      
Average Annual Return, Percent 14.67% 7.63% 9.14%
Class IA Shares      
Prospectus [Line Items]      
Average Annual Return, Percent 14.69% 8.67% 8.71%
Class IB Shares      
Prospectus [Line Items]      
Average Annual Return, Percent 14.38% 8.39% 8.43%
[1]
Effective February 1, 2026, the Putnam VT Balanced Blended Benchmark replaced the Putnam Balanced Blended Benchmark as the fund’s benchmark. The Investment Manager believes that the Putnam VT Balanced Blended Benchmark better reflects the fund’s current portfolio.