| Label                          | **Element**              | Value                                                                                                                                                                                                  |
|--------------------------------|--------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| **Risk/Return:**               | rr_RiskReturnAbstract    |                                                                                                                                                                                                   |
| Registrant Name                | dei_EntityRegistrantName | Fidelity Rutland Square Trust II                                                                                                                                                                       |
| Prospectus Date                | rr_ProspectusDate        | Jul. 30,  2015                                                                                                                                                                                         |
| Strategic Advisers Growth Fund |                          |                                                                                                                                                                                                   |
| **Risk/Return:**               | rr_RiskReturnAbstract    |                                                                                                                                                                                                   |
| Supplement [Text Block]        | frst_SupplementTextBlock | **Supplement to the Strategic Advisers® Growth Fund July 30, 2015 Prospectus***Effective October 1, 2015, the fund changed its classification from a non-diversified fund to a diversified fund.* |

| 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.
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| X                                                                                                                                                                                                                               |
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| X                                                                                                                                                                                                                                                                                                                                               |
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| - Definition
The date of the prospectus.
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| X                                                                                                                                                                                  |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - References
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| X                                                                                                                                 |
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