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Label Element Value
Prospectus [Line Items] rr_ProspectusLineItems  
Document Type dei_DocumentType 497
Document Period End Date dei_DocumentPeriodEndDate Apr. 30, 2022
Entity Registrant Name dei_EntityRegistrantName Putnam Variable Trust
Entity Central Index Key dei_EntityCentralIndexKey 0000822671
Entity Inv Company Type dei_EntityInvCompanyType N-1A
Amendment Flag dei_AmendmentFlag false
Putnam VT Small Cap Value Fund  
Prospectus [Line Items] rr_ProspectusLineItems  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual fund operating expenses (expenses you pay each year as a percentage of the value of your investment)
Expense Example [Heading] rr_ExpenseExampleHeading Example
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock

The following hypothetical example is intended to help you compare the cost of investing in the fund with the cost of investing in other funds. The example does not reflect insurance-related charges or expenses. If it did, expenses would be higher. It assumes that you invest $10,000 in the fund for the time periods indicated and then redeem or hold all your shares at the end of those periods. It assumes a 5% return on your investment each year and that the fund’s operating expenses remain the same. Your actual costs may be higher or lower.

 
Putnam VT Small Cap Value Fund | Class IA  
Prospectus [Line Items] rr_ProspectusLineItems  
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.61%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.14%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets none [1]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 0.75%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 77
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 240
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 417
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 930
Putnam VT Small Cap Value Fund | Class IB  
Prospectus [Line Items] rr_ProspectusLineItems  
Management Fees (as a percentage of Assets) rr_ManagementFeesOverAssets 0.61%
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses (as a percentage of Assets): rr_OtherExpensesOverAssets 0.14%
Acquired Fund Fees and Expenses rr_AcquiredFundFeesAndExpensesOverAssets none [1]
Expenses (as a percentage of Assets) rr_ExpensesOverAssets 1.00%
Expense Example, with Redemption, 1 Year rr_ExpenseExampleYear01 $ 102
Expense Example, with Redemption, 3 Years rr_ExpenseExampleYear03 318
Expense Example, with Redemption, 5 Years rr_ExpenseExampleYear05 552
Expense Example, with Redemption, 10 Years rr_ExpenseExampleYear10 $ 1,225
[1] Restated to reflect current fees.