Label	Element	Value
Dreyfus Natural Resources Fund
Risk/Return:	rr_RiskReturnAbstract
Supplement [Text Block]	ck0001111178_SupplementTextBlock	November 18, 2016 DREYFUS OPPORTUNITY FUNDS Dreyfus Natural Resources Fund Supplement to Summary and Statutory Prospectus dated February 1, 2016 The following changes will take effect on December 19, 2016:
Risk/Return [Heading]	rr_RiskReturnHeading	Dreyfus Natural Resources Fund
Strategy [Heading]	rr_StrategyHeading	The following sentence replaces the last sentence of the sections entitled "Principal Investment Strategy" in the summary prospectus and "Fund Summary – Principal Investment Strategy" in the statutory prospectus:
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	The fund may invest in foreign securities, including emerging markets securities, without limitation.

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Risk/Return Summary Investment Objectives/Goals Include the following information, in plain English under rule 421(d) under the Securities Act, in the order and subject matter indicated

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Form
-Number N-1A
-Chapter A
-Section 2

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Principal investment strategies of the Fund. Summarize how the Fund intends to achieve its investment objectives by identifying the Fund's principal investment strategies (including the type or types of securities in which the Fund invests or will invest principally) and any policy to concentrate in securities of issuers in a particular industry or group of industries.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Form
-Number N-1A
-Chapter A
-Section 4
-Subsection a

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Form
-Number N-1A
-Chapter A
-Section 4
-Subsection a

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