S000003871 [Member] Average Annual Total Returns |
12 Months Ended | 60 Months Ended | 120 Months Ended |
|---|---|---|---|
Dec. 31, 2025 |
Dec. 31, 2025 |
Dec. 31, 2025 |
|
| Bloomberg U.S. Aggregate Index (no deduction for fees, expenses or taxes) | |||
| Prospectus [Line Items] | |||
| Average Annual Return, Percent | 7.30% | (0.36%) | 2.01% |
| Bloomberg U.S. MBS Index (no deduction for fees, expenses or taxes) | |||
| Prospectus [Line Items] | |||
| Average Annual Return, Percent | 8.58% | 0.15% | 1.59% |
| Putnam VT Mortgage Securities Linked Benchmark (no deduction for fees, expenses or taxes) | |||
| Prospectus [Line Items] | |||
| Average Annual Return, Percent | 8.58% | 0.15% | 1.48% |
| Class IA Shares | |||
| Prospectus [Line Items] | |||
| Average Annual Return, Percent | 9.39% | 1.07% | 1.87% |
| Class IB shares | |||
| Prospectus [Line Items] | |||
| Average Annual Return, Percent | 9.09% | 0.83% | 1.62% |