| Label                                             | **Element**              | Value                                                                                                                                                                                                                                                                                             |
|---------------------------------------------------|--------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| **Risk/Return:**                                  | rr_RiskReturnAbstract    |                                                                                                                                                                                                                                                                                              |
| Registrant Name                                   | dei_EntityRegistrantName | FIDELITY INVESTMENT TRUST                                                                                                                                                                                                                                                                         |
| Prospectus Date                                   | rr_ProspectusDate        | Dec. 30,  2014                                                                                                                                                                                                                                                                                    |
| Retail | Fidelity Emerging Markets Discovery Fund |                          |                                                                                                                                                                                                                                                                                              |
| **Risk/Return:**                                  | rr_RiskReturnAbstract    |                                                                                                                                                                                                                                                                                              |
| Supplement [Text Block]                           | fit_SupplementTextBlock  | **Supplement to the Fidelity® Emerging Markets Discovery Fund and Fidelity Total Emerging Markets Fund December 30, 2014 Prospectus**Effective October 1, 2015, Fidelity® Emerging Markets Discovery Fund changed its classification from a non-diversified fund to a diversified fund. |

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