Risk/Return Detail Data - BroadlyDiversifiedInternationalEquityFunds-RetailComboPRO	Dec. 30, 2022 USD ($)
Risk/Return:
Registrant Name	Fidelity Investment Trust
BroadlyDiversifiedInternationalEquityFunds-RetailComboPRO | Fidelity Diversified International Fund
Risk/Return:
Risk/Return [Heading]	Fund Summary Fund /Class: Fidelity® Diversified International Fund /Fidelity® Diversified International Fund
Objective [Heading]	Investment Objective
Objective, Primary [Text Block]	Fidelity® Diversified International Fund seeks capital growth.
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 certain share classes 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 20 % of the average value of its portfolio.
Portfolio Turnover, Rate	20.00%
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. Normally investing primarily in common stocks. 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
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 Exposure. 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. 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]	You could lose money by investing in the 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 over various periods of time. The index description appears 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 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, 2022
Bar Chart, Year to Date Return	(33.67%)
Highest Quarterly Return, Label	Highest Quarter Return
Highest Quarterly Return, Date	Jun. 30, 2020
Highest Quarterly Return	21.46%
Lowest Quarterly Return, Label	Lowest Quarter Return
Lowest Quarterly Return, Date	Mar. 31, 2020
Lowest Quarterly Return	(19.33%)
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.
BroadlyDiversifiedInternationalEquityFunds-RetailComboPRO | Fidelity Diversified International Fund | Fidelity Diversified International Fund
Risk/Return:
Management fee	0.81%	[1]
Distribution and/or Service (12b-1) fees	none
Other expenses	0.18%
Total annual operating expenses	0.99%
1 year	$ 101
3 years	315
5 years	547
10 years	$ 1,213
2012	19.41%
2013	25.19%
2014	(3.20%)
2015	3.12%
2016	(3.73%)
2017	26.65%
2018	(15.24%)
2019	29.70%
2020	18.91%
2021	12.84%
BroadlyDiversifiedInternationalEquityFunds-RetailComboPRO | Fidelity Diversified International Fund | Return Before Taxes | Fidelity Diversified International Fund
Risk/Return:
Label	Return Before Taxes
Past 1 year	12.84%
Past 5 years	13.31%
Past 10 years	10.38%
BroadlyDiversifiedInternationalEquityFunds-RetailComboPRO | Fidelity Diversified International Fund | After Taxes on Distributions | Fidelity Diversified International Fund
Risk/Return:
Label	Return After Taxes on Distributions
Past 1 year	10.34%
Past 5 years	12.14%
Past 10 years	9.61%
BroadlyDiversifiedInternationalEquityFunds-RetailComboPRO | Fidelity Diversified International Fund | After Taxes on Distributions and Sales | Fidelity Diversified International Fund
Risk/Return:
Label	Return After Taxes on Distributions and Sale of Fund Shares
Past 1 year	9.53%
Past 5 years	10.57%
Past 10 years	8.50%
BroadlyDiversifiedInternationalEquityFunds-RetailComboPRO | Fidelity Diversified International Fund | MS001
Risk/Return:
Label	MSCI EAFE Index
Past 1 year	11.48%
Past 5 years	9.78%
Past 10 years	8.22%

[1] A The management fee is comprised of a basic fee of 0.65% adjusted up or down by a maximum of 0.20% based on the fund's performance relative to that of the MSCI EAFE Index. Please see "Fund Services - Fund Management - Advisory Fee(s)" for additional information.