Risk/Return Detail Data - FidelitySeriesSelectInternationalSmallCapFund-PRO	Dec. 30, 2024 USD ($)
Risk/Return:
Registrant Name	Fidelity Investment Trust
FidelitySeriesSelectInternationalSmallCapFund-PRO | Fidelity Series Select International Small Cap Fund
Risk/Return:
Risk/Return [Heading]	Fund Summary Fund: Fidelity® Series Select International Small Cap Fund
Objective [Heading]	Investment Objective
Objective, Primary [Text Block]	Fidelity® Series Select International Small Cap Fund seeks capital appreciation.
Expense [Heading]	Fee Table
Expense Narrative [Text Block]	The following table describes the fees and expenses that may be incurred when you buy, hold, and sell shares 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 28, 2028
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 18 % of the average value of its portfolio.
Portfolio Turnover, Rate	18.00%
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 primarily in non-U.S. securities, including securities of issuers located in emerging markets. The Adviser considers non-U.S. securities to include investments that are tied economically to a particular country or region outside the U.S. Emerging markets include 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 that the Adviser identifies as having similar emerging markets characteristics. The Adviser considers a number of factors to determine whether an issuer is located in or tied economically to a particular country or region including: whether a third-party vendor has assigned a particular country or region classification to the issuer or included the issuer in an index representative of a particular country or region; the issuer's domicile, incorporation, and location of assets; whether the issuer derives at least 50% of its revenues from, or has at least 50% of its assets in, a particular country or region; the source of government guarantees (if any); and the primary trading market or listing exchange. Whether an issuer is located in or tied economically to a particular country can be determined under any of these factors. Normally investing at least 80% of assets in securities of companies with small market capitalizations (which, for purposes of this fund, are those companies with market capitalizations similar to companies in the MSCI EAFE Small Cap Index or the MSCI ACWI ex USA Small Cap Index). Effective December 11, 2025, derivative instruments that provide investment exposure to the investments above or exposure to one or more market risk factors associated with such investments are included in the fund's 80% policy, consistent with the fund's investment policies and limitations with respect to investments in derivatives. Normally investing primarily in equity securities. Allocating investments across different countries and regions. 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]	Principal Investment Risks
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 performance of the fund's shares over the past 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 additional index has 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. The performance shown does not reflect the impact of any fees paid at the fee-based account or plan level, if applicable. Visit www.fidelity.com for more recent performance information.
Performance Information Illustrates Variability of Returns [Text]	The information illustrates the performance of the fund's shares over the past 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
Year to Date Return, Label	Year-to-Date Return
Bar Chart, Year to Date Return, Date	Sep. 30, 2024
Bar Chart, Year to Date Return	8.81%
Highest Quarterly Return, Label	Highest Quarter Return
Highest Quarterly Return, Date	Dec. 31, 2023
Highest Quarterly Return	11.58%
Lowest Quarterly Return, Label	Lowest Quarter Return
Lowest Quarterly Return, Date	Sep. 30, 2023
Lowest Quarterly Return	(4.55%)
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.
FidelitySeriesSelectInternationalSmallCapFund-PRO | Fidelity Series Select International Small Cap Fund | Fidelity Series Select International Small Cap Fund
Risk/Return:
Management fee	none
Distribution and/or Service (12b-1) fees	none
Other expenses	0.22%
Total annual operating expenses	0.22%
Fee waiver and/or expense reimbursement	0.21%	[1]
Total annual operating expenses after fee waiver and/or expense reimbursement	0.01%
1 year	$ 1
3 years	3
5 years	48
10 years	$ 206
Annual Return, Inception Date	Nov. 04, 2022
2023	15.13%
FidelitySeriesSelectInternationalSmallCapFund-PRO | Fidelity Series Select International Small Cap Fund | Return Before Taxes | Fidelity Series Select International Small Cap Fund
Risk/Return:
Label	Return Before Taxes
Past 1 year	15.13%
Since Inception	22.81%	[2]
FidelitySeriesSelectInternationalSmallCapFund-PRO | Fidelity Series Select International Small Cap Fund | After Taxes on Distributions | Fidelity Series Select International Small Cap Fund
Risk/Return:
Label	Return After Taxes on Distributions
Past 1 year	13.07%
Since Inception	20.81%	[2]
FidelitySeriesSelectInternationalSmallCapFund-PRO | Fidelity Series Select International Small Cap Fund | After Taxes on Distributions and Sales | Fidelity Series Select International Small Cap Fund
Risk/Return:
Label	Return After Taxes on Distributions and Sale of Fund Shares
Past 1 year	9.47%
Since Inception	16.85%	[2]
FidelitySeriesSelectInternationalSmallCapFund-PRO | Fidelity Series Select International Small Cap Fund | MS001
Risk/Return:
Label	MSCI EAFE Index
Past 1 year	18.49%
Since Inception	25.84%
FidelitySeriesSelectInternationalSmallCapFund-PRO | Fidelity Series Select International Small Cap Fund | MS141
Risk/Return:
Label	MSCI EAFE Small Cap Index
Past 1 year	13.37%
Since Inception	21.37%

[1] A Fidelity Management & Research Company LLC (FMR) has contractually agreed to reimburse the fund to the extent that total operating expenses (excluding interest, fees and expenses of the Independent Trustees, 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 0.013% (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 28, 2028 . 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 4, 2022 .