| Label | Element | Value |
|---|---|---|
| Prospectus: | rr_ProspectusTable | |
| Document Type | dei_DocumentType | 485BPOS |
| Document Period End Date | dei_DocumentPeriodEndDate | Dec. 31, 2015 |
| Registrant Name | dei_EntityRegistrantName | OPPENHEIMER ROCHESTER FUND MUNICIPALS |
| Central Index Key | dei_EntityCentralIndexKey | 0000093621 |
| Amendment Flag | dei_AmendmentFlag | false |
| Document Creation Date | dei_DocumentCreationDate | Mar. 24, 2016 |
| Document Effective Date | dei_DocumentEffectiveDate | Mar. 28, 2016 |
| Prospectus Date | rr_ProspectusDate | Mar. 28, 2016 |