| Form N-CSR Cover | 6 Months Ended |
| Jun. 30, 2024 | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSRS |
| Amendment Flag | false |
| Registrant Name | EATON VANCE VARIABLE TRUST |
| Entity Central Index Key | 0001121746 |
| Entity Investment Company Type | N-1A |
| Document Period End Date | Jun. 30, 2024 |
| Shareholder Report | 6 Months Ended |
| Jun. 30, 2024 USD ($) Holding | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSRS |
| Amendment Flag | false |
| Registrant Name | EATON VANCE VARIABLE TRUST |
| Entity Central Index Key | 0001121746 |
| Entity Investment Company Type | N-1A |
| Document Period End Date | Jun. 30, 2024 |
| C000139703 | |
| Shareholder Report [Line Items] | |
| Fund Name | Eaton Vance VT Floating-Rate Income Fund |
| Class Name | ADV Class |
| Trading Symbol | VTFLA |
| Annual or Semi-Annual Statement [Text Block] | This semi-annual shareholder report contains important information about the Eaton Vance VT Floating-Rate Income Fund for the period of January 1, 2024 to June 30, 2024. |
| Shareholder Report Annual or Semi-Annual | Semi-Annual Shareholder Report |
| Additional Information [Text Block] | You can find additional information about the Fund at www.eatonvance.com/open-end-mutual-fund-documents.php |
| Additional Information Phone Number | 1-800-262-1122 |
| Additional Information Website | www.eatonvance.com/open-end-mutual-fund-documents.php</span>" id="sjs-B19"><span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 10.6667px; font-weight: 400; grid-area: auto; line-height: 16px; margin: 0px; overflow: visible; text-align: left;">www.eatonvance.com/open-end-mutual-fund-documents.php</span> |
| Expenses [Text Block] | What were the Fund costs for the last six months? Footnote Reference (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment ADV Class $48 0.95% Footnote Description Footnote 1 Does not reflect expenses and charges that are, or may be, imposed under the variable annuity contract or variable life insurance separate account or qualified pension or retirement plan through which your investment in the Fund is made. |
| Expenses Paid, Amount | $ 48 |
| Expense Ratio, Percent | 0.95% |
| AssetsNet | $ 573,673,246 |
| Holdings Count | Holding | 507 |
| InvestmentCompanyPortfolioTurnover | 16% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics Total Net Assets $573,673,246 # of Portfolio Holdings 507 Portfolio Turnover Rate 16% |
| Holdings [Text Block] | Asset Allocation (% of total investments) Value Value Other Footnote Reference 1.3% Short-Term Investments 1.9% Asset-Backed Securities 3.1% Corporate Bonds 7.0% Senior Floating-Rate Loans 86.7% Footnote Description Footnote † Investment types less than 1% each |
| Material Fund Change [Text Block] | |
| Updated Prospectus Phone Number | 1-800-262-1122 |
| C000014195 | |
| Shareholder Report [Line Items] | |
| Fund Name | Eaton Vance VT Floating-Rate Income Fund |
| Class Name | Initial Class |
| Trading Symbol | VTFLR |
| Annual or Semi-Annual Statement [Text Block] | This semi-annual shareholder report contains important information about the Eaton Vance VT Floating-Rate Income Fund for the period of January 1, 2024 to June 30, 2024. |
| Shareholder Report Annual or Semi-Annual | Semi-Annual Shareholder Report |
| Additional Information [Text Block] | You can find additional information about the Fund at www.eatonvance.com/open-end-mutual-fund-documents.php |
| Additional Information Phone Number | 1-800-262-1122 |
| Additional Information Website | www.eatonvance.com/open-end-mutual-fund-documents.php</span>" id="sjs-B39"><span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 10.6667px; font-weight: 400; grid-area: auto; line-height: 16px; margin: 0px; overflow: visible; text-align: left;">www.eatonvance.com/open-end-mutual-fund-documents.php</span> |
| Expenses [Text Block] | What were the Fund costs for the last six months? Footnote Reference (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Initial Class $61 1.20% Footnote Description Footnote 1 Does not reflect expenses and charges that are, or may be, imposed under the variable annuity contract or variable life insurance separate account or qualified pension or retirement plan through which your investment in the Fund is made. |
| Expenses Paid, Amount | $ 61 |
| Expense Ratio, Percent | 1.20% |
| AssetsNet | $ 573,673,246 |
| Holdings Count | Holding | 507 |
| InvestmentCompanyPortfolioTurnover | 16% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics Total Net Assets $573,673,246 # of Portfolio Holdings 507 Portfolio Turnover Rate 16% |
| Holdings [Text Block] | Asset Allocation (% of total investments) Value Value Other Footnote Reference 1.3% Short-Term Investments 1.9% Asset-Backed Securities 3.1% Corporate Bonds 7.0% Senior Floating-Rate Loans 86.7% Footnote Description Footnote † Investment types less than 1% each |
| Material Fund Change [Text Block] | |
| Updated Prospectus Phone Number | 1-800-262-1122 |
| C000162648 | |
| Shareholder Report [Line Items] | |
| Fund Name | Eaton Vance VT Floating-Rate Income Fund |
| Class Name | Institutional Class |
| Trading Symbol | VTFLI |
| Annual or Semi-Annual Statement [Text Block] | This semi-annual shareholder report contains important information about the Eaton Vance VT Floating-Rate Income Fund for the period of January 1, 2024 to June 30, 2024. |
| Shareholder Report Annual or Semi-Annual | Semi-Annual Shareholder Report |
| Additional Information [Text Block] | You can find additional information about the Fund at www.eatonvance.com/open-end-mutual-fund-documents.php |
| Additional Information Phone Number | 1-800-262-1122 |
| Additional Information Website | www.eatonvance.com/open-end-mutual-fund-documents.php</span>" id="sjs-B59"><span style="box-sizing: border-box; color: rgb(0, 0, 0); display: inline; flex-wrap: nowrap; font-size: 10.6667px; font-weight: 400; grid-area: auto; line-height: 16px; margin: 0px; overflow: visible; text-align: left;">www.eatonvance.com/open-end-mutual-fund-documents.php</span> |
| Expenses [Text Block] | What were the Fund costs for the last six months? Footnote Reference (based on a hypothetical $10,000 investment) Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Institutional Class $35 0.70% Footnote Description Footnote 1 Does not reflect expenses and charges that are, or may be, imposed under the variable annuity contract or variable life insurance separate account or qualified pension or retirement plan through which your investment in the Fund is made. |
| Expenses Paid, Amount | $ 35 |
| Expense Ratio, Percent | 0.70% |
| AssetsNet | $ 573,673,246 |
| Holdings Count | Holding | 507 |
| InvestmentCompanyPortfolioTurnover | 16% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics Total Net Assets $573,673,246 # of Portfolio Holdings 507 Portfolio Turnover Rate 16% |
| Holdings [Text Block] | Asset Allocation (% of total investments) Value Value Other Footnote Reference 1.3% Short-Term Investments 1.9% Asset-Backed Securities 3.1% Corporate Bonds 7.0% Senior Floating-Rate Loans 86.7% Footnote Description Footnote † Investment types less than 1% each |
| Material Fund Change [Text Block] | |
| Updated Prospectus Phone Number | 1-800-262-1122 |
| Shareholder Report, Holdings (Details) | Jun. 30, 2024 |
| C000139703 | Not Rated | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.20% |
| C000139703 | CCC or Lower | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.30% |
| C000139703 | B | |
| Holdings [Line Items] | |
| Percent of Total Investments | 60.50% |
| C000139703 | BB | |
| Holdings [Line Items] | |
| Percent of Total Investments | 23.90% |
| C000139703 | BBB | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.10% |
| C000139703 | Asset Other Line | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.30% |
| C000139703 | AssetShort-Term Investments | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.90% |
| C000139703 | AssetAsset-Backed Securities | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.10% |
| C000139703 | AssetCorporate Bonds | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7% |
| C000139703 | AssetSenior Floating-Rate Loans | |
| Holdings [Line Items] | |
| Percent of Total Investments | 86.70% |
| C000014195 | Not Rated | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.20% |
| C000014195 | CCC or Lower | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.30% |
| C000014195 | B | |
| Holdings [Line Items] | |
| Percent of Total Investments | 60.50% |
| C000014195 | BB | |
| Holdings [Line Items] | |
| Percent of Total Investments | 23.90% |
| C000014195 | BBB | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.10% |
| C000014195 | Asset Other Line | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.30% |
| C000014195 | AssetShort-Term Investments | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.90% |
| C000014195 | AssetAsset-Backed Securities | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.10% |
| C000014195 | AssetCorporate Bonds | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7% |
| C000014195 | AssetSenior Floating-Rate Loans | |
| Holdings [Line Items] | |
| Percent of Total Investments | 86.70% |
| C000162648 | Not Rated | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.20% |
| C000162648 | CCC or Lower | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.30% |
| C000162648 | B | |
| Holdings [Line Items] | |
| Percent of Total Investments | 60.50% |
| C000162648 | BB | |
| Holdings [Line Items] | |
| Percent of Total Investments | 23.90% |
| C000162648 | BBB | |
| Holdings [Line Items] | |
| Percent of Total Investments | 6.10% |
| C000162648 | Asset Other Line | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.30% |
| C000162648 | AssetShort-Term Investments | |
| Holdings [Line Items] | |
| Percent of Total Investments | 1.90% |
| C000162648 | AssetAsset-Backed Securities | |
| Holdings [Line Items] | |
| Percent of Total Investments | 3.10% |
| C000162648 | AssetCorporate Bonds | |
| Holdings [Line Items] | |
| Percent of Total Investments | 7% |
| C000162648 | AssetSenior Floating-Rate Loans | |
| Holdings [Line Items] | |
| Percent of Total Investments | 86.70% |
