Risk/Return Detail Data - FidelityInfrastructureFund-PRO	Dec. 30, 2022 USD ($)
Risk/Return:
Registrant Name	Fidelity Investment Trust
FidelityInfrastructureFund-PRO | Fidelity Infrastructure Fund
Risk/Return:
Risk/Return [Heading]	Fund Summary Fund: Fidelity® Infrastructure Fund
Objective [Heading]	Investment Objective
Objective, Primary [Text Block]	Fidelity® Infrastructure Fund seeks long-term growth of capital.
Expense [Heading]	Fee Table
Expense Narrative [Text Block]	The following table describes the fees and expenses that may be incurred when you buy and hold shares of the fund. In addition to the fees and expenses described below, your broker may also require you to pay brokerage commissions on purchases and sales of the fund.
Shareholder Fees Caption [Text]	Shareholder fees
(fees paid directly from your investment)	none
Operating Expenses Caption [Text]	Annual Operating Expenses
Fee Waiver or Reimbursement over Assets, Date of Termination	February 29, 2024
Portfolio Turnover [Heading]	Portfolio Turnover
Portfolio Turnover [Text Block]	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. During the most recent fiscal year, the fund's portfolio turnover rate was 91 % of the average value of its portfolio.
Portfolio Turnover, Rate	91.00%
Expense Example Narrative [Text Block]	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 the 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]	Principal Investment Strategies
Strategy Narrative [Text Block]	Normally investing at least 80% of assets in securities of companies that own, operate, or are involved in the distribution, development, and service of infrastructure-related assets. Such companies may include those involved in transportation and supply chain infrastructure, such as airports, highways, railroads, marine ports, and warehouse and logistics facilities; utilities infrastructure, such as electric, water, gas, renewable electricity, and multi-utilities; energy infrastructure, such as oil, gas, and electricity storage and transportation; and communications and digital infrastructure, such as cell towers, data centers and internet infrastructure, and satellites; as well as other infrastructure companies. Normally investing primarily in equity securities. 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. Investing in either "growth" stocks or "value" stocks or both. Investing in securities of domestic and foreign issuers.
Risk [Heading]	Principal Investment Risks
Risk Narrative [Text Block]	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 Markets 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. The extent of economic development; political stability; market depth, infrastructure, and capitalization; and regulatory oversight can be less than in more developed markets. Emerging markets typically have less established legal, accounting and financial reporting systems than those in more developed markets, which may reduce the scope or quality of financial information available to investors. 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. Infrastructure Industries Concentration. The infrastructure industries can be significantly affected by general economic trends; fluctuations in energy and commodity prices; supply and demand of services or fuel; interest rate changes; financing difficulties; natural resource conservation; labor relations; legislation; taxes; government regulation and spending; geopolitical developments; import controls; worldwide competition; and liability for environmental damage, depletion of resources, and mandated expenditures for safety and pollution control. 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. "Growth" Investing. "Growth" stocks can perform differently from the market as a whole and other types of stocks and can be more volatile than other types of stocks.       "Value" Investing. "Value" stocks can perform differently from the market as a whole and other types of stocks and can continue to be undervalued by the market for long periods of time. In addition, the fund is classified as non-diversified under the Investment Company Act of 1940 (1940 Act), which means that it has the ability to invest a greater portion of assets in securities of a smaller number of individual issuers than a diversified fund. As a result, changes in the market value of a single investment could cause greater fluctuations in share price than would occur in a more diversified fund. 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]	You could lose money by investing in the fund.
Risk Nondiversified Status [Text]	In addition, the fund is classified as non-diversified under the Investment Company Act of 1940 (1940 Act), which means that it has the ability to invest a greater portion of assets in securities of a smaller number of individual issuers than a diversified fund. As a result, changes in the market value of a single investment could cause greater fluctuations in share price than would occur in a more diversified fund.
Risk Not Insured Depository Institution [Text]	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]	Performance
Performance Narrative [Text Block]	The following information is intended to help you understand the risks of investing in the fund. The information illustrates the changes in the performance of the fund's shares from year to year and compares the performance of the fund's shares to the performance of a securities market index and an additional index over various periods of time. The indexes have characteristics relevant to the fund's investment strategies. Index descriptions appear in the "Additional Index Information" section of the prospectus. Past performance (before and after taxes) is not an indication of future performance. Visit www.fidelity.com for more recent performance information.
Performance Information Illustrates Variability of Returns [Text]	The information illustrates the changes in the performance of the fund's shares from year to year and compares the performance of the fund's shares to the performance of a securities market index and an additional index over various periods of time.
Performance Availability Website Address [Text]	www.fidelity.com
Performance Past Does Not Indicate Future [Text]	Past performance (before and after taxes) is not an indication of future performance.
Bar Chart [Heading]	Year-by-Year Returns
Annual Return, Inception Date	Nov. 05, 2019
Year to Date Return, Label	Year-to-Date Return
Bar Chart, Year to Date Return, Date	Sep. 30, 2022
Bar Chart, Year to Date Return	(15.44%)
Highest Quarterly Return, Label	Highest Quarter Return
Highest Quarterly Return, Date	Jun. 30, 2020
Highest Quarterly Return	14.74%
Lowest Quarterly Return, Label	Lowest Quarter Return
Lowest Quarterly Return, Date	Mar. 31, 2020
Lowest Quarterly Return	(15.41%)
Performance Table Heading	Average Annual Returns
Performance Table Uses Highest Federal Rate	After-tax returns are calculated using the historical highest individual federal marginal income tax rates, but do not reflect the impact of state or local taxes.
Performance Table Not Relevant to Tax Deferred	The after-tax returns shown are not relevant if you hold your shares in a retirement account or in another tax-deferred arrangement, such as an employee benefit plan (profit sharing, 401(k), or 403(b) plan).
Performance Table Explanation after Tax Higher	Return After Taxes on Distributions and Sale of Fund Shares may be higher than other returns for the same period due to a tax benefit of realizing a capital loss upon the sale of fund shares.
Performance Table Narrative	After-tax returns are calculated using the historical highest individual federal marginal income tax rates, but do not reflect the impact of state or local taxes. Actual after-tax returns may differ depending on your individual circumstances. The after-tax returns shown are not relevant if you hold your shares in a retirement account or in another tax-deferred arrangement, such as an employee benefit plan (profit sharing, 401(k), or 403(b) plan). Return After Taxes on Distributions and Sale of Fund Shares may be higher than other returns for the same period due to a tax benefit of realizing a capital loss upon the sale of fund shares.
FidelityInfrastructureFund-PRO | Fidelity Infrastructure Fund | Fidelity Infrastructure Fund
Risk/Return:
Management fee	0.68%
Distribution and/or Service (12b-1) fees	none
Other expenses	0.45%
Total annual operating expenses	1.13%
Fee waiver and/or expense reimbursement	0.18%	[1]
Total annual operating expenses after fee waiver and/or expense reimbursement	0.95%
1 year	$ 97
3 years	335
5 years	599
10 years	$ 1,353
2020	12.80%
2021	7.58%
FidelityInfrastructureFund-PRO | Fidelity Infrastructure Fund | Return Before Taxes | Fidelity Infrastructure Fund
Risk/Return:
Label	Return Before Taxes
Past 1 year	7.58%
Since Inception	12.14%
FidelityInfrastructureFund-PRO | Fidelity Infrastructure Fund | After Taxes on Distributions | Fidelity Infrastructure Fund
Risk/Return:
Label	Return After Taxes on Distributions
Past 1 year	7.50%
Since Inception	11.99%
FidelityInfrastructureFund-PRO | Fidelity Infrastructure Fund | After Taxes on Distributions and Sales | Fidelity Infrastructure Fund
Risk/Return:
Label	Return After Taxes on Distributions and Sale of Fund Shares
Past 1 year	4.68%
Since Inception	9.45%
FidelityInfrastructureFund-PRO | Fidelity Infrastructure Fund | MS159
Risk/Return:
Label	MSCI ACWI (All Country World Index) Index
Past 1 year	18.90%
Since Inception	18.91%	[2]
FidelityInfrastructureFund-PRO | Fidelity Infrastructure Fund | SP212
Risk/Return:
Label	S&P® Global Infrastructure Index
Past 1 year	11.87%
Since Inception	4.22%	[2]

[1] A Fidelity Management & Research Company LLC (FMR) has contractually agreed to reimburse the fund to the extent that total operating expenses (excluding interest, certain taxes, fees and expenses of the Independent Trustees, proxy and shareholder meeting expenses, extraordinary expenses, and acquired fund fees and expenses (including fees and expenses associated with a wholly owned subsidiary), if any, as well as non-operating expenses such as brokerage commissions and fees and expenses associated with the fund's securities lending program, if applicable), as a percentage of its average net assets, exceed 0.95% (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 through the end of the fiscal year any expenses that were reimbursed during the current fiscal year up to, but not in excess of, the Expense Cap. This arrangement will remain in effect through February 29, 2024 . FMR may not terminate this arrangement before the expiration date without the approval of the Board of Trustees and may extend it in its discretion after that date.

[2] A From November 5, 2019