Risk/Return Detail Data - FidelitySeriesInternationalFunds-ComboPRO	Dec. 30, 2024 USD ($)
Risk/Return:
Registrant Name	Fidelity Investment Trust
FidelitySeriesInternationalFunds-ComboPRO | Fidelity Series International Growth Fund
Risk/Return:
Risk/Return [Heading]	Fund Summary Fund: Fidelity® Series International Growth Fund
Objective [Heading]	Investment Objective
Objective, Primary [Text Block]	Fidelity® Series International Growth 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
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 26 % of the average value of its portfolio.
Portfolio Turnover, Rate	26.00%
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 primarily in common stocks. Normally investing in companies that Fidelity Management & Research Company LLC (FMR) believes have above-average growth potential (stocks of these companies are often called "growth" stocks). Allocating investments across 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. Effective December 11, 2025, the Adviser normally invests at least 80% of assets in securities of growth companies. Growth companies are companies the Adviser believes have above average growth potential. The Adviser considers a number of factors in determining a company's growth potential, such as whether the company is included in a third-party growth benchmark or classified as a growth company by a third-party vendor, if the company's projected earnings per share growth, sales growth per share or free cash flow growth or its trailing earnings per share growth is above the equity market median, if the company's research and development expenses exceed sales, general and administrative expenses, or if the company is raising capital to grow, fund or expand its business. A company's growth potential can be determined under any of these factors. 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.
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 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 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 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
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	12.43%
Highest Quarterly Return, Label	Highest Quarter Return
Highest Quarterly Return, Date	Jun. 30, 2020
Highest Quarterly Return	18.37%
Lowest Quarterly Return, Label	Lowest Quarter Return
Lowest Quarterly Return, Date	Mar. 31, 2020
Lowest Quarterly Return	(17.35%)
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.
FidelitySeriesInternationalFunds-ComboPRO | Fidelity Series International Growth Fund | Fidelity Series International Growth Fund
Risk/Return:
Management fee	none
Distribution and/or Service (12b-1) fees	none
Other expenses	0.01%
Total annual operating expenses	0.01%
1 year	$ 1
3 years	3
5 years	6
10 years	$ 13
2014	(3.37%)
2015	4.34%
2016	(3.54%)
2017	30.21%
2018	(10.87%)
2019	35.56%
2020	18.61%
2021	16.61%
2022	(22.88%)
2023	21.73%
FidelitySeriesInternationalFunds-ComboPRO | Fidelity Series International Growth Fund | Return Before Taxes | Fidelity Series International Growth Fund
Risk/Return:
Label	Return Before Taxes
Past 1 year	21.73%
Past 5 years	11.97%
Past 10 years	7.11%
FidelitySeriesInternationalFunds-ComboPRO | Fidelity Series International Growth Fund | After Taxes on Distributions | Fidelity Series International Growth Fund
Risk/Return:
Label	Return After Taxes on Distributions
Past 1 year	21.39%
Past 5 years	10.28%
Past 10 years	5.83%
FidelitySeriesInternationalFunds-ComboPRO | Fidelity Series International Growth Fund | After Taxes on Distributions and Sales | Fidelity Series International Growth Fund
Risk/Return:
Label	Return After Taxes on Distributions and Sale of Fund Shares
Past 1 year	13.16%
Past 5 years	9.37%
Past 10 years	5.50%
FidelitySeriesInternationalFunds-ComboPRO | Fidelity Series International Growth Fund | MS001
Risk/Return:
Label	MSCI EAFE Index
Past 1 year	18.49%
Past 5 years	8.39%
Past 10 years	4.48%
FidelitySeriesInternationalFunds-ComboPRO | Fidelity Series International Growth Fund | MS270
Risk/Return:
Label	MSCI EAFE Growth Index
Past 1 year	17.75%
Past 5 years	8.97%
Past 10 years	5.31%