Document and Entity Information	12 Months Ended
Oct. 26, 2012
Risk/Return:
Document Type	485BPOS
Document Period End Date	Jun. 30, 2012
Registrant Name	BLACKROCK MULTI STATE MUNICIPAL SERIES TRUST
Central Index Key	0000774013
Amendment Flag	false
Document Creation Date	Oct. 26, 2012
Document Effective Date	Oct. 26, 2012
Prospectus Date	Oct. 26, 2012

If the value is true, then the document is an amendment to previously-filed/accepted document.

No definition available.

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- 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

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- Definition

The date when a document, upon receipt and acceptance, becomes officially effective, in CCYY-MM-DD format. Usually it is a system-assigned date time value, but it may be declared by the submitter in some cases.

+ References

No definition available.

+ Details

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- Definition

The end date of the period reflected on the cover page if a periodic report. For all other reports and registration statements containing historical data, it is the date up through which that historical data is presented. If there is no historical data in the report, use the filing date. The format of the date is CCYY-MM-DD.

+ References

No definition available.

+ Details

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Namespace Prefix:	dei_
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- 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
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Data Type:	dei:submissionTypeItemType
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Period Type:	duration

- 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 Regulation 12B

-Number 240

-Section 12b

-Subsection 1

+ Details

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- 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

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- 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

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- Details

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