S000003871 [Member] Expense Example, No Redemption - Putnam VT Mortgage Securities Fund |
Dec. 31, 2025
USD ($)
|
|---|---|
| Class IA Shares | |
| Prospectus [Line Items] | |
| Expense Example, No Redemption, 1 Year | $ 51 |
| Expense Example, No Redemption, 3 Years | 269 |
| Expense Example, No Redemption, 5 Years | 504 |
| Expense Example, No Redemption, 10 Years | 1,180 |
| Class IB shares | |
| Prospectus [Line Items] | |
| Expense Example, No Redemption, 1 Year | 77 |
| Expense Example, No Redemption, 3 Years | 346 |
| Expense Example, No Redemption, 5 Years | 635 |
| Expense Example, No Redemption, 10 Years | $ 1,458 |