| Label                  | **Element**              | Value                     |
|------------------------|--------------------------|---------------------------|
| **Risk/Return:**       | rr_RiskReturnAbstract    |                      |
| Registrant Name        | dei_EntityRegistrantName | FIDELITY INVESTMENT TRUST |
| Prospectus Date        | rr_ProspectusDate        | Dec. 30,  2014            |
| Document Creation Date | dei_DocumentCreationDate | Oct. 16,  2015            |

| X                                                                                                                                                                                                                                                                                                                                                                                                           |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The date the document was made available and submitted, in CCYY-MM-DD format. The date of submission, date of acceptance by the recipient, and the document effective date are all potentially different.
+ References
No definition available.
+ Details**Name:**dei_DocumentCreationDate**Namespace Prefix:**dei_**Data Type:**xbrli:dateItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The exact name of the entity filing the report as specified in its charter, which is required by forms filed with the SEC.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation 12B -Number 240 -Section 12b -Subsection 1
+ Details**Name:**dei_EntityRegistrantName**Namespace Prefix:**dei_**Data Type:**xbrli:normalizedStringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                               |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The date of the prospectus.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Form -Number N-1A -Chapter A -Section 1 -Subsection a -Paragraph 3
+ Details**Name:**rr_ProspectusDate**Namespace Prefix:**rr_**Data Type:**xbrli:dateItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                  |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - References
No definition available.
+ Details**Name:**rr_RiskReturnAbstract**Namespace Prefix:**rr_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |