Shareholder Report, Holdings (Details)	Jul. 31, 2026
Fidelity Massachusetts Municipal Money Market Fund \| EMD0Member
Holdings [Line Items]
Percent of Net Asset Value	74.70%
Fidelity Massachusetts Municipal Money Market Fund \| EMD1Member
Holdings [Line Items]
Percent of Net Asset Value	0.70%
Fidelity Massachusetts Municipal Money Market Fund \| EMD2Member
Holdings [Line Items]
Percent of Net Asset Value	5.20%
Fidelity Massachusetts Municipal Money Market Fund \| EMD3Member
Holdings [Line Items]
Percent of Net Asset Value	5.20%
Fidelity Massachusetts Municipal Money Market Fund \| EMD4Member
Holdings [Line Items]
Percent of Net Asset Value	4.00%
Fidelity Massachusetts Municipal Money Market Fund \| EMD5Member
Holdings [Line Items]
Percent of Net Asset Value	6.50%
Fidelity Massachusetts Municipal Money Market Fund \| AAVariableRateDemandNotesVRDNsMember
Holdings [Line Items]
Percent of Net Asset Value	39.00%
Fidelity Massachusetts Municipal Money Market Fund \| AAMunicipalSecuritiesMember
Holdings [Line Items]
Percent of Net Asset Value	22.60%
Fidelity Massachusetts Municipal Money Market Fund \| AATenderOptionBondMember
Holdings [Line Items]
Percent of Net Asset Value	21.50%
Fidelity Massachusetts Municipal Money Market Fund \| AANetOtherAssetsLiabilitiesMember
Holdings [Line Items]
Percent of Net Asset Value	16.90%
Fidelity Massachusetts Municipal Money Market Fund - Premium Class \| EMD0Member
Holdings [Line Items]
Percent of Net Asset Value	74.70%
Fidelity Massachusetts Municipal Money Market Fund - Premium Class \| EMD1Member
Holdings [Line Items]
Percent of Net Asset Value	0.70%
Fidelity Massachusetts Municipal Money Market Fund - Premium Class \| EMD2Member
Holdings [Line Items]
Percent of Net Asset Value	5.20%
Fidelity Massachusetts Municipal Money Market Fund - Premium Class \| EMD3Member
Holdings [Line Items]
Percent of Net Asset Value	5.20%
Fidelity Massachusetts Municipal Money Market Fund - Premium Class \| EMD4Member
Holdings [Line Items]
Percent of Net Asset Value	4.00%
Fidelity Massachusetts Municipal Money Market Fund - Premium Class \| EMD5Member
Holdings [Line Items]
Percent of Net Asset Value	6.50%
Fidelity Massachusetts Municipal Money Market Fund - Premium Class \| AAVariableRateDemandNotesVRDNsMember
Holdings [Line Items]
Percent of Net Asset Value	39.00%
Fidelity Massachusetts Municipal Money Market Fund - Premium Class \| AAMunicipalSecuritiesMember
Holdings [Line Items]
Percent of Net Asset Value	22.60%
Fidelity Massachusetts Municipal Money Market Fund - Premium Class \| AATenderOptionBondMember
Holdings [Line Items]
Percent of Net Asset Value	21.50%
Fidelity Massachusetts Municipal Money Market Fund - Premium Class \| AANetOtherAssetsLiabilitiesMember
Holdings [Line Items]
Percent of Net Asset Value	16.90%
Fidelity Massachusetts Municipal Money Market Fund - Institutional Class \| EMD0Member
Holdings [Line Items]
Percent of Net Asset Value	74.70%
Fidelity Massachusetts Municipal Money Market Fund - Institutional Class \| EMD1Member
Holdings [Line Items]
Percent of Net Asset Value	0.70%
Fidelity Massachusetts Municipal Money Market Fund - Institutional Class \| EMD2Member
Holdings [Line Items]
Percent of Net Asset Value	5.20%
Fidelity Massachusetts Municipal Money Market Fund - Institutional Class \| EMD3Member
Holdings [Line Items]
Percent of Net Asset Value	5.20%
Fidelity Massachusetts Municipal Money Market Fund - Institutional Class \| EMD4Member
Holdings [Line Items]
Percent of Net Asset Value	4.00%
Fidelity Massachusetts Municipal Money Market Fund - Institutional Class \| EMD5Member
Holdings [Line Items]
Percent of Net Asset Value	6.50%
Fidelity Massachusetts Municipal Money Market Fund - Institutional Class \| AAVariableRateDemandNotesVRDNsMember
Holdings [Line Items]
Percent of Net Asset Value	39.00%
Fidelity Massachusetts Municipal Money Market Fund - Institutional Class \| AAMunicipalSecuritiesMember
Holdings [Line Items]
Percent of Net Asset Value	22.60%
Fidelity Massachusetts Municipal Money Market Fund - Institutional Class \| AATenderOptionBondMember
Holdings [Line Items]
Percent of Net Asset Value	21.50%
Fidelity Massachusetts Municipal Money Market Fund - Institutional Class \| AANetOtherAssetsLiabilitiesMember
Holdings [Line Items]
Percent of Net Asset Value	16.90%
Fidelity Massachusetts Municipal Income Fund \| RS0Member
Holdings [Line Items]
Percent of Net Asset Value	32.00%
Fidelity Massachusetts Municipal Income Fund \| RS1Member
Holdings [Line Items]
Percent of Net Asset Value	17.70%
Fidelity Massachusetts Municipal Income Fund \| RS2Member
Holdings [Line Items]
Percent of Net Asset Value	12.70%
Fidelity Massachusetts Municipal Income Fund \| RS3Member
Holdings [Line Items]
Percent of Net Asset Value	11.00%
Fidelity Massachusetts Municipal Income Fund \| RS4Member
Holdings [Line Items]
Percent of Net Asset Value	10.40%
Fidelity Massachusetts Municipal Income Fund \| RS5Member
Holdings [Line Items]
Percent of Net Asset Value	5.80%
Fidelity Massachusetts Municipal Income Fund \| RS6Member
Holdings [Line Items]
Percent of Net Asset Value	7.20%
Fidelity Massachusetts Municipal Income Fund \| QDAAAMember
Holdings [Line Items]
Percent of Net Asset Value	9.50%
Fidelity Massachusetts Municipal Income Fund \| QDAAMember
Holdings [Line Items]
Percent of Net Asset Value	62.60%
Fidelity Massachusetts Municipal Income Fund \| QDAMember
Holdings [Line Items]
Percent of Net Asset Value	8.30%
Fidelity Massachusetts Municipal Income Fund \| QDBBBMember
Holdings [Line Items]
Percent of Net Asset Value	12.60%
Fidelity Massachusetts Municipal Income Fund \| QDBBMember
Holdings [Line Items]
Percent of Net Asset Value	1.80%
Fidelity Massachusetts Municipal Income Fund \| QDNotRatedMember
Holdings [Line Items]
Percent of Net Asset Value	2.00%
Fidelity Massachusetts Municipal Income Fund \| QDShortTermInvestmentsandNetOtherAssetsLiabilitiesMember
Holdings [Line Items]
Percent of Net Asset Value	3.20%

Shareholder Report, Holdings (Details)

Jul. 31, 2026