XML 11 R1.htm IDEA: XBRL DOCUMENT v3.24.3

N-2	6 Months Ended
	Sep. 30, 2024 shares
Cover [Abstract]
Entity Central Index Key	0001454741
Amendment Flag	false
Document Type	N-CSRS
Entity Registrant Name	Eaton Vance National Municipal Opportunities Trust
General Description of Registrant [Abstract]
Investment Objectives and Practices [Text Block]	The Trust’s primary investment objective is to provide current income exempt from regular federal income tax. The Trust will, as a secondary investment objective, seek to achieve capital appreciation.
Latest Premium (Discount) to NAV [Percent]	(5.13%)	[1]
Common Shares [Member]
Capital Stock, Long-Term Debt, and Other Securities [Abstract]
Outstanding Security, Title [Text Block]	Common Shares
Outstanding Security, Held [Shares]	15,624,921
[1] The shares of the Fund often trade at a discount or premium to their net asset value. The discount or premium may vary over time and may be higher or lower than what is quoted in this report. For up-to-date premium/discount information, please refer to https://funds.eatonvance.com/closed-end-fund-prices.php.

X

- References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Form N-2
-Section Item 10

+ Details

Name:	cef_CapitalStockLongTermDebtAndOtherSecuritiesAbstract
Namespace Prefix:	cef_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Form N-2
-Section Item 8

+ Details

Name:	cef_GeneralDescriptionOfRegistrantAbstract
Namespace Prefix:	cef_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Form N-2
-Section Item 8
-Subsection 2
-Paragraph b, d

+ Details

Name:	cef_InvestmentObjectivesAndPracticesTextBlock
Namespace Prefix:	cef_
Data Type:	dtr-types:textBlockItemType
Balance Type:	na
Period Type:	duration

X

- References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Form N-2
-Section Item 8
-Subsection 5
-Paragraph c

+ Details

Name:	cef_LatestPremiumDiscountToNavPercent
Namespace Prefix:	cef_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

X

- References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Form N-2
-Section Item 10
-Subsection 5
-Paragraph 3

+ Details

Name:	cef_OutstandingSecurityHeldShares
Namespace Prefix:	cef_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

X

- References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Form N-2
-Section Item 10
-Subsection 5
-Paragraph 1

+ Details

Name:	cef_OutstandingSecurityTitleTextBlock
Namespace Prefix:	cef_
Data Type:	dtr-types:textBlockItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Boolean flag that is true when the XBRL content amends previously-filed or accepted submission.

+ References

No definition available.

+ Details

Name:	dei_AmendmentFlag
Namespace Prefix:	dei_
Data Type:	xbrli:booleanItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Cover page.

+ References

No definition available.

+ Details

Name:	dei_CoverAbstract
Namespace Prefix:	dei_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

The type of document being provided (such as 10-K, 10-Q, 485BPOS, etc). The document type is limited to the same value as the supporting SEC submission type, or the word 'Other'.

+ References

No definition available.

+ Details

Name:	dei_DocumentType
Namespace Prefix:	dei_
Data Type:	dei:submissionTypeItemType
Balance Type:	na
Period Type:	duration

X

- Definition

A unique 10-digit SEC-issued value to identify entities that have filed disclosures with the SEC. It is commonly abbreviated as CIK.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Exchange Act
-Number 240
-Section 12
-Subsection b-2

+ Details

Name:	dei_EntityCentralIndexKey
Namespace Prefix:	dei_
Data Type:	dei:centralIndexKeyItemType
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 Exchange Act
-Number 240
-Section 12
-Subsection b-2

+ Details

Name:	dei_EntityRegistrantName
Namespace Prefix:	dei_
Data Type:	xbrli:normalizedStringItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	us-gaap_StatementClassOfStockAxis=ck0001454741_CommonSharesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: