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Shareholder Report
 6 Months Ended
Dec. 31, 2025
USD ($)
Holding
Shareholder Report [Line Items]  
Document Type N-CSRS
Amendment Flag false
Registrant Name Federated Hermes Short-Intermediate Duration Municipal Trust
Entity Central Index Key 0000353101
Entity Investment Company Type N-1A
Document Period End Date Dec. 31, 2025
C000024678 [Member]  
Shareholder Report [Line Items]  
Fund Name Federated Hermes Short-Intermediate Municipal Fund
Class Name Service Shares
Trading Symbol FSHSX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about the Federated Hermes Short-Intermediate Municipal Fund (the “Fund”) for the period of July 1, 2025 to December 31, 2025.
Shareholder Report Annual or Semi-Annual semi-annual shareholder report
Additional Information [Text Block] You can find additional information about the Fund at FederatedHermes.com/us/FundInformation. You can also request this information by contacting us at 1‑800‑341‑7400, Option 4, or your financial advisor.
Additional Information Phone Number 1‑800‑341‑7400
Additional Information Website FederatedHermes.com/us/FundInformation
Expenses [Text Block]
What were the Fund costs for the last six months?
(Based on a hypothetical $10,000 investment)
Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment
Service Shares $33 0.64%
Expenses Paid, Amount $ 33
Expense Ratio, Percent 0.64%
Net Assets $ 389,083,108
Holdings Count | Holding 197
Investment Company Portfolio Turnover 14.00%
Additional Fund Statistics [Text Block]
Key Fund Statistics
Net Assets $389,083,108
Number of Investments 197
Portfolio Turnover Rate 14%
Holdings [Text Block]
Fund Holdings
Top Sectors
(% of Net Assets)
Graphical Representation - Allocation 1 Chart
C000024677 [Member]  
Shareholder Report [Line Items]  
Fund Name Federated Hermes Short-Intermediate Municipal Fund
Class Name Institutional Shares
Trading Symbol FSHIX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about the Federated Hermes Short-Intermediate Municipal Fund (the “Fund”) for the period of July 1, 2025 to December 31, 2025.
Shareholder Report Annual or Semi-Annual semi-annual shareholder report
Additional Information [Text Block] You can find additional information about the Fund at FederatedHermes.com/us/FundInformation. You can also request this information by contacting us at 1‑800‑341‑7400, Option 4, or your financial advisor.
Additional Information Phone Number 1‑800‑341‑7400
Additional Information Website FederatedHermes.com/us/FundInformation
Expenses [Text Block]
What were the Fund costs for the last six months?
(Based on a hypothetical $10,000 investment)
Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment
Institutional Shares $20 0.40%
Expenses Paid, Amount $ 20
Expense Ratio, Percent 0.40%
Net Assets $ 389,083,108
Holdings Count | Holding 197
Investment Company Portfolio Turnover 14.00%
Additional Fund Statistics [Text Block]
Key Fund Statistics
Net Assets $389,083,108
Number of Investments 197
Portfolio Turnover Rate 14%
Holdings [Text Block]
Fund Holdings
Top Sectors
(% of Net Assets)
Graphical Representation - Allocation 1 Chart
C000037571 [Member]  
Shareholder Report [Line Items]  
Fund Name Federated Hermes Short-Intermediate Municipal Fund
Class Name Class A Shares
Trading Symbol FMTAX
Annual or Semi-Annual Statement [Text Block] This semi-annual shareholder report contains important information about the Federated Hermes Short-Intermediate Municipal Fund (the “Fund”) for the period of July 1, 2025 to December 31, 2025.
Shareholder Report Annual or Semi-Annual semi-annual shareholder report
Additional Information [Text Block] You can find additional information about the Fund at FederatedHermes.com/us/FundInformation. You can also request this information by contacting us at 1‑800‑341‑7400, Option 4, or your financial advisor.
Additional Information Phone Number 1‑800‑341‑7400
Additional Information Website FederatedHermes.com/us/FundInformation
Expenses [Text Block]
What were the Fund costs for the last six months?
(Based on a hypothetical $10,000 investment)
Class Name Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment
Class A Shares $33 0.65%
Expenses Paid, Amount $ 33
Expense Ratio, Percent 0.65%
Net Assets $ 389,083,108
Holdings Count | Holding 197
Investment Company Portfolio Turnover 14.00%
Additional Fund Statistics [Text Block]
Key Fund Statistics
Net Assets $389,083,108
Number of Investments 197
Portfolio Turnover Rate 14%
Holdings [Text Block]
Fund Holdings
Top Sectors
(% of Net Assets)
Graphical Representation - Allocation 1 Chart