Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

FEDERATED SHORT-INTERMEDIATE DURATION MUNICIPAL TRUST

Prospectus Date

rr_ProspectusDate

Aug. 31, 2019

Supplement to Prospectus [Text Block]

rr_SupplementToProspectusTextBlock

Federated Short-Intermediate Duration Municipal Trust

CLASS A SHARES (TICKER FMTAX)
INSTITUTIONAL SHARES (TICKER FSHIX)
SERVICE SHARES (TICKER FSHSX)

SUPPLEMENT TO PROSPECTUS DATED AUGUST 31, 2019, AS AMENDED

1. Under the section entitled "Fund Summary Information," please replace the final sentence of the "Risk/Return Summary: Fees and Expenses" introductory paragraph with the following:

"If you purchase the Fund's IS or SS Shares through a broker acting as an agent on behalf of its customers, you may be required to pay a commission to such broker; such commissions, if any, are not reflected in the Example below."

FEDERATED SHORT-INTERMEDIATE DURATION MUNICIPAL TRUST

Risk/Return:

rr_RiskReturnAbstract

Supplement to Prospectus [Text Block]

rr_SupplementToProspectusTextBlock

Federated Short-Intermediate Duration Municipal Trust

CLASS A SHARES (TICKER FMTAX)
INSTITUTIONAL SHARES (TICKER FSHIX)
SERVICE SHARES (TICKER FSHSX)

SUPPLEMENT TO PROSPECTUS DATED AUGUST 31, 2019, AS AMENDED

1. Under the section entitled "Fund Summary Information," please replace the final sentence of the "Risk/Return Summary: Fees and Expenses" introductory paragraph with the following:

"If you purchase the Fund's IS or SS Shares through a broker acting as an agent on behalf of its customers, you may be required to pay a commission to such broker; such commissions, if any, are not reflected in the Example below."