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Label Element Value
Risk/Return: rr_RiskReturnAbstract  
Document Type dei_DocumentType Other
Document Period End Date dei_DocumentPeriodEndDate Dec. 31, 2010
Registrant Name dei_EntityRegistrantName JOHN HANCOCK VARIABLE INSURANCE TRUST
Central Index Key dei_EntityCentralIndexKey 0000756913
Amendment Flag dei_AmendmentFlag false
Document Creation Date dei_DocumentCreationDate Dec. 19, 2011
Document Effective Date dei_DocumentEffectiveDate Dec. 20, 2011
Prospectus Date rr_ProspectusDate May 02, 2011
Supplement [Text Block] jht756913_SupplementTextBlock
John Hancock Variable Insurance Trust
Supplement dated December 19, 2011
to the Prospectus dated May 2, 2011
Core Balanced Strategy Trust
Core Allocation Trust
Core Disciplined Diversification Trust
Core Balanced Trust
Balanced Trust
Large Cap Trust
   Fund Reorganizations
On December 16, 2011, the Board of Trustees of John Hancock Variable Insurance Trust (the “Trust”) approved an Agreement and Plan of Reorganization providing for the following reorganizations:
     
Acquired Fund  Acquiring Fund
Core Balanced Strategy Trust
   Core Strategy Trust
Core Allocation Trust
   Lifestyle Growth Trust
Core Disciplined Diversification Trust
  Lifestyle Growth Trust
Core Balanced Trust
 Lifestyle Growth Trust
Balanced Trust
 Lifestyle Growth Trust
Large Cap Trust
   U.S. Equity Trust
A meeting of the shareholders of each Acquired Fund has been scheduled for Tuesday, April 17, 2012 to seek approval of the respective reorganization. Subject to regulatory and shareholder approval, each reorganization is scheduled to occur immediately after the close of business on Friday, April 27, 2012.
Large Cap Trust | Prospectus Series I, Series II and Series NAV Shares
  
Risk/Return: rr_RiskReturnAbstract  
Supplement [Text Block] jht756913_SupplementTextBlock In addition, on January 19, 2012, Grantham, Mayo, Van Otterloo & Co., LLC (“GMO”), the subadviser to the U.S. Equity Trust, will replace UBS Global Asset Management (Americas) Inc. as the subadviser to the Large Cap Trust.
Examples rr_ExpenseExampleAbstract  
Supplement Strategy [Text Block] jht756913_SupplementStrategyTextBlock In connection with this change, effective January 19, 2012, the investment policies of the Large Cap Trust are amended and restated as follows:
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock

Under normal market conditions, the fund invests at least 80% of its net assets (plus any borrowings for investment purposes) in equity securities of large capitalization companies tied economically to the U.S. The fund defines large capitalization companies as those with a market capitalization range, at the time of investment, equal to that of the Russell 1000 Index. As of October 31, 2011, the market capitalization range of the Russell 1000 Index was $877 million to $385 billion.

In general, the fund emphasizes large capitalization stocks, but it may also invest up to 20% of its net assets (plus any borrowings for investment purposes) in equity securities of small and medium capitalization companies and/or the securities of foreign companies in developed countries. Investments in equity securities may include dividend-paying securities, common stock and preferred stock, IPOs, ETFs, equity index futures, shares of investment companies, convertible securities, warrants and rights. For purposes of the fund, ETFs and index futures are considered securities with a market capitalization equal to the weighted average market capitalization of the basket of securities comprising the ETF or underlying index.

In managing the fund, the subadviser uses active investment management methods, which means that equities are bought and sold according to the subadviser’s evaluation of companies’ published financial information, securities’ prices, equity and bond markets, and the overall economy.

In selecting equities for the fund, the subadviser may use a combination of quantitative and qualitative investment methods to identify equities that the subadviser believes present positive return potential relative to other equities. Some of these methods evaluate individual equities or a group of equities (e.g., equities of companies in a particular industry) based on the ratio of their price to historical financial information, including book value, cash flow and earnings, and forecasted financial information provided by industry analysts. The subadviser may compare these ratios to industry or market averages in assessing the relative attractiveness of an equity or a group of equities. Other methods used by the subadviser focus on evaluating patterns of price movement or volatility of an equity or group of equities relative to the fund’s investment universe. The subadviser also may adjust the fund’s portfolio for factors such as position size, industry and sector exposure, and market capitalization.
Financial Services Trust | Prospectus Series I, Series II and Series NAV Shares
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading JOHN HANCOCK FINANCIAL SERVICES TRUST
Annual Fund Operating Expenses rr_OperatingExpensesAbstract  
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Expenses Restated to Reflect Current [Text] rr_ExpensesRestatedToReflectCurrent The management fee has been restated to reflect contractual changes to the Advisory Agreement.
Examples rr_ExpenseExampleAbstract  
Expense Example [Heading] rr_ExpenseExampleHeading Examples.
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock The examples are intended to help you compare the cost of investing in the fund with the cost of investing in other mutual funds. The examples assume that $10,000 is invested in the fund for the periods indicated and then all shares are redeemed at the end of those periods. The examples also assume that the investment has a 5% return each year and that the fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on the these assumptions your costs would be:
Financial Services Trust | Prospectus Series I, Series II and Series NAV Shares | Series I
  
Annual Fund Operating Expenses rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Series I
Management Fee rr_ManagementFeesOverAssets 0.78% [1]
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.05%
Other Expenses rr_OtherExpensesOverAssets 0.06%
Total Fund Operating Expenses rr_ExpensesOverAssets 0.89%
Examples rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Series I
Year 1 rr_ExpenseExampleYear01 91
Year 3 rr_ExpenseExampleYear03 284
Year 5 rr_ExpenseExampleYear05 493
Year 10 rr_ExpenseExampleYear10 1,096
Financial Services Trust | Prospectus Series I, Series II and Series NAV Shares | Series II
  
Annual Fund Operating Expenses rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Series II
Management Fee rr_ManagementFeesOverAssets 0.78% [1]
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets 0.25%
Other Expenses rr_OtherExpensesOverAssets 0.06%
Total Fund Operating Expenses rr_ExpensesOverAssets 1.09%
Examples rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Series II
Year 1 rr_ExpenseExampleYear01 111
Year 3 rr_ExpenseExampleYear03 347
Year 5 rr_ExpenseExampleYear05 601
Year 10 rr_ExpenseExampleYear10 1,329
Financial Services Trust | Prospectus Series I, Series II and Series NAV Shares | Series NAV
  
Annual Fund Operating Expenses rr_OperatingExpensesAbstract  
Operating Expenses Column [Text] rr_OperatingExpensesColumnName Series NAV
Management Fee rr_ManagementFeesOverAssets 0.78% [1]
Distribution and Service (12b-1) Fees rr_DistributionAndService12b1FeesOverAssets none
Other Expenses rr_OtherExpensesOverAssets 0.06%
Total Fund Operating Expenses rr_ExpensesOverAssets 0.84%
Examples rr_ExpenseExampleAbstract  
Expense Example, By Year, Column [Text] rr_ExpenseExampleByYearColumnName Series NAV
Year 1 rr_ExpenseExampleYear01 86
Year 3 rr_ExpenseExampleYear03 268
Year 5 rr_ExpenseExampleYear05 466
Year 10 rr_ExpenseExampleYear10 1,037
[1] The management fee has been restated to reflect contractual changes to the Advisory Agreement.