Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	FIDELITY INVESTMENT TRUST
Prospectus Date	rr_ProspectusDate	Aug. 16, 2018
Fidelity Series Emerging Markets Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Fund Summary Fund: Fidelity® Series Emerging Markets Fund
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The fund seeks capital appreciation.
Expense [Heading]	rr_ExpenseHeading	Fee Table
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	The following table describes the fees and expenses that may be incurred when you buy and hold shares of the fund.
Shareholder Fees Caption [Text]	rr_ShareholderFeesCaption	Shareholder fees (fees paid directly from your investment)
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	Annual Operating Expenses (expenses that you pay each year as a % of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	February 28, 2022
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	Portfolio Turnover
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when fund shares are held in a taxable account. These costs, which are not reflected in annual operating expenses or in the example, affect the fund’s performance.
Other Expenses, New Fund, Based on Estimates [Text]	rr_OtherExpensesNewFundBasedOnEstimates	Based on estimated amounts for the current fiscal year.
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	This example helps compare the cost of investing in the fund with the cost of investing in other funds. Let’s say, hypothetically, that the annual return for shares of the fund is 5% and that your shareholder fees and the annual operating expenses for shares of the fund are exactly as described in the fee table. This example illustrates the effect of fees and expenses, but is not meant to suggest actual or expected fees and expenses or returns, all of which may vary. For every $10,000 you invested, here’s how much you would pay in total expenses if you sell all of your shares at the end of each time period indicated:
Strategy [Heading]	rr_StrategyHeading	Principal Investment Strategies
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	Normally investing at least 80% of assets in securities of issuers in emerging markets (countries that have an emerging stock market as defined by MSCI, countries or markets with low- to middle-income economies as classified by the World Bank, and other countries or markets with similar emerging characteristics) and other investments that are tied economically to emerging markets. Normally investing primarily in common stocks. Allocating investments across different emerging market countries. Using fundamental analysis of factors such as each issuer’s financial condition and industry position, as well as market and economic conditions, to select investments.
Risk [Heading]	rr_RiskHeading	Principal Investment Risks
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	Stock Market Volatility. Stock markets are volatile and can decline significantly in response to adverse issuer, political, regulatory, market, or economic developments. Different parts of the market, including different market sectors, and different types of securities can react differently to these developments. Foreign and Emerging Market Risk. Foreign markets, particularly emerging markets, can be more volatile than the U.S. market due to increased risks of adverse issuer, political, regulatory, market, or economic developments and can perform differently from the U.S. market. Emerging markets can be subject to greater social, economic, regulatory, and political uncertainties and can be extremely volatile. Foreign exchange rates also can be extremely volatile. Issuer-Specific Changes. The value of an individual security or particular type of security can be more volatile than, and can perform differently from, the market as a whole. An investment in the fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. You could lose money by investing in the fund.
Risk Lose Money [Text]	rr_RiskLoseMoney	You could lose money by investing in the fund.
Risk Not Insured Depository Institution [Text]	rr_RiskNotInsuredDepositoryInstitution	An investment in the fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance
Performance One Year or Less [Text]	rr_PerformanceOneYearOrLess	Performance history will be available for the fund after the fund has been in operation for one calendar year.
Fidelity Series Emerging Markets Fund | Class: Fidelity Series Emerging Markets Fund
Risk/Return:	rr_RiskReturnAbstract
Shareholder fees (fees paid directly from your investment)	rr_ShareholderFeeOther	none
Management fee	rr_ManagementFeesOverAssets	none
Distribution and/or Service (12b-1) fees	rr_DistributionAndService12b1FeesOverAssets	none
Other expenses	rr_OtherExpensesOverAssets	0.06%	[1]
Total annual operating expenses	rr_ExpensesOverAssets	0.06%
Fee waiver and/or expense reimbursement	rr_FeeWaiverOrReimbursementOverAssets	0.05%	[2]
Total annual operating expenses after fee waiver and/or expense reimbursement	rr_NetExpensesOverAssets	0.01%
1 year	rr_ExpenseExampleYear01	$ 1
3 years	rr_ExpenseExampleYear03	$ 3

[1] Based on estimated amounts for the current fiscal year.

[2] The Adviser has contractually agreed to reimburse the fund to the extent that total operating expenses (excluding interest, certain taxes, certain securities lending costs, brokerage commissions, fees and expenses of the Independent Trustees, proxy and shareholder meeting expenses, extraordinary expenses, and acquired fund fees and expenses, if any), as a percentage of its average net assets, exceed 0.014% (the Expense Cap). If at any time during the current fiscal year expenses for the fund fall below the Expense Cap, FMR reserves the right to recoup prior reimbursed expenses up to, but not in excess of, the Expense Cap. This arrangement will remain in effect through February 28, 2022. FMR may not terminate this arrangement before the expiration date without the approval of the Board of Trustees.