Risk/Return Detail Data - FidelityOverseasFund-AMCIZPRO - USD ($)			12 Months Ended											60 Months Ended	120 Months Ended
		Nov. 17, 2025	Nov. 17, 2025	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Nov. 17, 2025	Nov. 17, 2025
FidelityOverseasFund-AMCIZPRO | Fidelity Overseas Fund | Fidelity Advisor Overseas Fund - Class A
Prospectus Line Items
Maximum Cumulative Sales Charge (as a percentage of Offering Price)		5.75%
Maximum Deferred Sales Charge (as a percentage)	[1]	0.00%
Management Fees (as a percentage of Assets)	[2],[3]	0.71%
Distribution and Service (12b-1) Fees		0.25%
Other Expenses (as a percentage of Assets):	[3]	0.01%
Expenses (as a percentage of Assets)		0.97%
Expense Example, with Redemption, 1 Year		$ 668
Expense Example, with Redemption, 3 Years		866
Expense Example, with Redemption, 5 Years		1,080
Expense Example, with Redemption, 10 Years		1,696
Expense Example, No Redemption, 1 Year		668
Expense Example, No Redemption, 3 Years		866
Expense Example, No Redemption, 5 Years		1,080
Expense Example, No Redemption, 10 Years		$ 1,696
Average Annual Return, Label [Optional Text]			Return Before Taxes
Average Annual Return, Percent			5.20%											5.61%	7.14%
Annual Return [Percent]				5.20%	20.55%	(24.79%)	19.36%	15.42%	28.42%	(14.69%)	29.65%	(1.32%)	8.25%
FidelityOverseasFund-AMCIZPRO | Fidelity Overseas Fund | Fidelity Advisor Overseas Fund - Class M
Prospectus Line Items
Maximum Cumulative Sales Charge (as a percentage of Offering Price)		3.50%
Maximum Deferred Sales Charge (as a percentage)	[1]	0.00%
Management Fees (as a percentage of Assets)	[2],[3]	0.71%
Distribution and Service (12b-1) Fees		0.50%
Other Expenses (as a percentage of Assets):	[3]	0.01%
Expenses (as a percentage of Assets)		1.22%
Expense Example, with Redemption, 1 Year		$ 470
Expense Example, with Redemption, 3 Years		724
Expense Example, with Redemption, 5 Years		997
Expense Example, with Redemption, 10 Years		1,776
Expense Example, No Redemption, 1 Year		470
Expense Example, No Redemption, 3 Years		724
Expense Example, No Redemption, 5 Years		997
Expense Example, No Redemption, 10 Years		$ 1,776
FidelityOverseasFund-AMCIZPRO | Fidelity Overseas Fund | Fidelity Advisor Overseas Fund - Class C
Prospectus Line Items
Maximum Cumulative Sales Charge (as a percentage of Offering Price)		0.00%
Maximum Deferred Sales Charge (as a percentage)	[4]	1.00%
Management Fees (as a percentage of Assets)	[2],[3]	0.71%
Distribution and Service (12b-1) Fees		1.00%
Other Expenses (as a percentage of Assets):	[3]	0.01%
Expenses (as a percentage of Assets)		1.72%
Expenses Deferred Charges [Text Block]		On Class C shares redeemed less than one year after purchase.
Expense Example, with Redemption, 1 Year		$ 275
Expense Example, with Redemption, 3 Years		542
Expense Example, with Redemption, 5 Years		933
Expense Example, with Redemption, 10 Years		1,831
Expense Example, No Redemption, 1 Year		175
Expense Example, No Redemption, 3 Years		542
Expense Example, No Redemption, 5 Years		933
Expense Example, No Redemption, 10 Years		$ 1,831
FidelityOverseasFund-AMCIZPRO | Fidelity Overseas Fund | Fidelity Advisor Overseas Fund - Class I
Prospectus Line Items
Maximum Cumulative Sales Charge (as a percentage of Offering Price)		0.00%
Maximum Deferred Sales Charge (as a percentage)		0.00%
Management Fees (as a percentage of Assets)	[2],[3]	0.71%
Distribution and Service (12b-1) Fees		0.00%
Other Expenses (as a percentage of Assets):	[3]	0.01%
Expenses (as a percentage of Assets)		0.72%
Expense Example, with Redemption, 1 Year		$ 74
Expense Example, with Redemption, 3 Years		230
Expense Example, with Redemption, 5 Years		401
Expense Example, with Redemption, 10 Years		894
Expense Example, No Redemption, 1 Year		74
Expense Example, No Redemption, 3 Years		230
Expense Example, No Redemption, 5 Years		401
Expense Example, No Redemption, 10 Years		$ 894
FidelityOverseasFund-AMCIZPRO | Fidelity Overseas Fund | Fidelity Advisor Overseas Fund - Class Z
Prospectus Line Items
Maximum Cumulative Sales Charge (as a percentage of Offering Price)		0.00%
Maximum Deferred Sales Charge (as a percentage)		0.00%
Management Fees (as a percentage of Assets)	[2],[3]	0.58%
Distribution and Service (12b-1) Fees		0.00%
Other Expenses (as a percentage of Assets):	[3]	0.01%
Expenses (as a percentage of Assets)		0.59%
Expense Example, with Redemption, 1 Year		$ 60
Expense Example, with Redemption, 3 Years		189
Expense Example, with Redemption, 5 Years		329
Expense Example, with Redemption, 10 Years		738
Expense Example, No Redemption, 1 Year		60
Expense Example, No Redemption, 3 Years		189
Expense Example, No Redemption, 5 Years		329
Expense Example, No Redemption, 10 Years		$ 738
FidelityOverseasFund-AMCIZPRO | Fidelity Overseas Fund
Prospectus Line Items
Risk/Return [Heading]		Fund Summary Fund/Class: Fidelity® Overseas Fund/Fidelity Advisor® Overseas Fund A, M, C, I, Z
Objective [Heading]		Investment Objective
Objective, Primary [Text Block]		Fidelity® Overseas Fund seeks long-term growth of capital.
Expense Heading [Optional Text]		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. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the fund or certain other Fidelity® funds. More information about these and other discounts is available from your investment professional and in the "Fund Distribution" section beginning on page 19 of the prospectus and in the sales charge waiver appendix to the prospectus.
Shareholder Fees Caption [Optional Text]		Shareholder fees
Operating Expenses Caption [Optional 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 35% of the average value of its portfolio.
Portfolio Turnover, Rate		35.00%
Expenses Deferred Charges [Text Block]		Class A and Class M purchases of $1 million or more will not be subject to a front-end sales charge. Such Class A and Class M purchases may be subject, upon redemption, to a contingent deferred sales charge (CDSC) of 1.00% and 0.25%, respectively.
Expense Breakpoint Discounts [Text]		You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the fund or certain other Fidelity® funds. More information about these and other discounts is available from your investment professional and in the "Fund Distribution" section beginning on page 19 of the prospectus
Expense Breakpoint, Minimum Investment Required [Amount]		$ 50,000
Other Expenses, New Fund, Based on Estimates [Text]		Based on estimated amounts for the current fiscal year.
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 and if you hold your shares:
Strategy [Heading]		Principal Investment Strategies
Strategy Narrative [Text Block]		Normally investing at least 80% of assets in non-U.S. securities. The Adviser considers non-U.S. securities to include investments that are tied economically to a particular country or region outside the U.S. 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. 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 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.
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 Fidelity® Overseas Fund, a class of shares of the fund, from year to year and compares the performance of this class 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 for Fidelity® Overseas Fund, a class of shares of the fund. Performance history will be available at institutional.fidelity.com for Class A, Class M, Class C, Class I, and Class Z after Class A, Class M, Class C, Class I, and Class Z have been in operation for one calendar year.
Performance Information Illustrates Variability of Returns [Text]		The information illustrates the changes in the performance of Fidelity® Overseas Fund, a class of shares of the fund, from year to year and compares the performance of this class to the performance of a securities market index over various periods of time.
Performance One Year or Less [Text]		Performance history will be available at institutional.fidelity.com for Class A, Class M, Class C, Class I, and Class Z after Class A, Class M, Class C, Class I, and Class Z have been in operation for one calendar year.
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
Bar Chart, Returns for Class Not Offered in Prospectus [Text]		* The returns shown above are for Fidelity® Overseas Fund, a class of shares of the fund that is not offered through this prospectus.   Class A, Class M, Class C, Class I, and Class Z would have substantially similar annual returns to Fidelity® Overseas Fund because the classes are invested in the same portfolio of securities. Class A's, Class M's, Class C's, Class I's, and Class Z's returns would differ from Fidelity® Overseas Fund's returns only to the extent that the classes do not have the same expenses.
Highest Quarterly Return, Label [Optional Text]		Highest Quarter Return
Highest Quarterly Return, Date		Jun. 30, 2020
Highest Quarterly Return		18.84%
Lowest Quarterly Return, Label [Optional Text]		Lowest Quarter Return
Lowest Quarterly Return, Date		Mar. 31, 2020
Lowest Quarterly Return		(19.83%)
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.
FidelityOverseasFund-AMCIZPRO | Fidelity Overseas Fund | After Taxes on Distributions | Fidelity Advisor Overseas Fund - Class A
Prospectus Line Items
Average Annual Return, Label [Optional Text]			Return After Taxes on Distributions
Average Annual Return, Percent			5.00%											5.33%	6.78%
FidelityOverseasFund-AMCIZPRO | Fidelity Overseas Fund | After Taxes on Distributions and Sales | Fidelity Advisor Overseas Fund - Class A
Prospectus Line Items
Average Annual Return, Label [Optional Text]			Return After Taxes on Distributions and Sale of Fund Shares
Average Annual Return, Percent			3.46%											4.51%	5.83%
FidelityOverseasFund-AMCIZPRO | Fidelity Overseas Fund | MS001
Prospectus Line Items
Average Annual Return, Label [Optional Text]			MSCI EAFE Index
Average Annual Return, Percent			4.07%											4.95%	5.41%
Document Type		497
Registrant Name		Fidelity Investment Trust

[1] AClass A and Class M purchases of $1 million or more will not be subject to a front-end sales charge. Such Class A and Class M purchases may be subject, upon redemption, to a contingent deferred sales charge (CDSC) of 1.00% and 0.25%, respectively.

[2] AThe management fee comprises a basic fee, which may vary by class, that is adjusted up or down (subject to a maximum rate) based on the performance of the fund or a designated class of the fund relative to that of the MSCI EAFE Index. Please see "Fund Services - Fund Management - Advisory Fee(s)" for additional information.

[3] BBased on estimated amounts for the current fiscal year.

[4] BOn Class C shares redeemed less than one year after purchase.