485BPOS

1933 Act File No.	33-36729
1940 Act File No.	811-6165

Form N-1A

SECURITIES AND EXCHANGE COMMISSION

Washington, DC 20549

REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933
	Pre-Effective Amendment No.
	Post-Effective Amendment No.	64
and/or
REGISTRATION STATEMENT UNDER THE INVESTMENT COMPANY ACT OF 1940
	Amendment No.	63

FEDERATED MUNICIPAL SECURITIES INCOME TRUST

(Exact Name of Registrant as Specified in Charter)

Federated Investors Funds

4000 Ericsson Drive

Warrendale, PA 15086-7561

(Address of Principal Executive Offices)

(412) 288-1900

(Registrant’s Telephone Number, including Area Code)

John W. McGonigle, Esquire

Federated Investors Tower

Pittsburgh, Pennsylvania 15222-3779

(Name and Address of Agent for Service)

It is proposed that this filing will become effective (check appropriate box):
X	immediately upon filing pursuant to paragraph (b)
	on	pursuant to paragraph (b)
	60 days after filing pursuant to paragraph (a)(1)
	on	pursuant to paragraph (a)(1)
	75 days after filing pursuant to paragraph (a)(2)
	on	pursuant to paragraph (a)(2) of Rule 485
If appropriate, check the following box:
	This post-effective amendment designates a new effective date for a previously filed post-effective amendment.

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, and the Investment Company Act of 1940, the Registrant, FEDERATED MUNICIPAL SECURITIES INCOME TRUST, certifies that it meets all of the requirements for effectiveness of this Amendment to its Registration Statement pursuant to Rule 485(b) under the Securities Act of 1933 and has duly caused this Amendment to its Registration Statement to be signed on its behalf by the undersigned, duly authorized, in the City of Pittsburgh and Commonwealth of Pennsylvania, on the 18th day of November, 2013.

FEDERATED MUNICIPAL SECURITIES INCOME TRUST

BY:  /s/ Timothy S. Johnson
Timothy S. Johnson, Assistant Secretary

Pursuant to the requirements of the Securities Act of 1933, this Amendment to its Registration Statement has been signed below by the following person in the capacity and on the date indicated:

NAME	TITLE	DATE
BY: /s/ Timothy S. Johnson Timothy S. Johnson Assistant Secretary	Attorney In Fact For the Persons Listed Below	November 18, 2013
John F. Donahue *	Trustee
J. Christopher Donahue *	President and Trustee (Principal Executive Officer)
Lori A. Hensler*	Treasurer (Principal Financial Officer)
John T. Collins*	Trustee
Maureen Lally-Green*	Trustee
Peter E. Madden*	Trustee
Charles F. Mansfield, Jr.*	Trustee
Thomas O’Neill*	Trustee
P. Jerome Richey*	Trustee
John S. Walsh*	Trustee
*By Power of Attorney

Federated Municipal High Yield Advantage Fund

Federated Michigan Intermediate Municipal Trust

Federated New York Municipal Income Fund

Federated Ohio Municipal Income Fund

Federated Pennsylvania Municipal Income Fund

Portfolios of FEDERATED MUNICIPAL SECURITIES INCOME TRUST

Post-Effective Amendment No. 64

This Post-Effective Amendment is filed for the sole purpose of submitting the XBRL Interactive Data File exhibits for the Risk/Return Summaries of the above-named Funds filed as part of Post-Effective Amendment No. 63 on October 28, 2013.  The exhibits filed herewith do not constitute the complete publicly filed disclosure for the Funds, and should be used in conjunction with the complete prospectuses for the Funds.

Exhibit List for Interactive Data File Submissions.

EX-101.INS	INSTANCE
EX-101.SCH	SCHEMA
EX-101.CAL	CALCULATION LINKBASE
EX-101.DEF	DEFINITION LINKBASE
EX-101.LAB	LABEL LINKBASE
EX-101.PRE	PRESENTATION LINKBASE

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Federated New York Municipal Income Fund

Federated New York Municipal Income Fund (the "Fund")

RISK/RETURN SUMMARY: INVESTMENT OBJECTIVE

The Fund's investment objective is to provide current income exempt from federal regular income tax (federal regular income tax does not include the federal alternative minimum tax (AMT)) and the personal income taxes imposed by the state of New York and New York municipalities.

RISK/RETURN SUMMARY: FEES AND EXPENSES

This table describes the fees and expenses that you may pay if you buy and hold Class A Shares (A) and Class B Shares (B) of the Fund. You may qualify for certain sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in certain classes (e.g., A class) of Federated funds. More information about these and other discounts is available from your financial professional and in the "What Do Shares Cost" section of the Prospectus on page 15.

Shareholder Fees (fees paid directly from your investment)

Shareholder Fees Federated New York Municipal Income Fund	A	B
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	4.50%	none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, as applicable)	none	5.50%
Maximum Sales Charge (Load) Imposed on Reinvested Dividends (and other Distributions) (as a percentage of offering price)	none	none
Redemption Fee (as a percentage of amount redeemed, if applicable)	none	none
Exchange Fee	none	none

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses Federated New York Municipal Income Fund		A		B
Management Fee		0.40%		0.40%
Distribution (12b-1) Fee		none	[1]	0.75%
Other Expenses		0.89%		0.89%
Total Annual Fund Operating Expenses		1.29%		2.04%
Fee Waivers and/or Expense Reimbursements	[2]	0.53%		0.52%
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements		0.76%		1.52%

Example

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 for the time periods indicated and then redeem all of your Shares at the end of those periods. Expenses assuming no redemption are also shown. The Example also assumes that your investment has a 5% return each year and that operating expenses are as shown in the table above and remain the same. Although your actual costs and returns may be higher or lower, based on these assumptions your costs would be:

Expense Example Federated New York Municipal Income Fund (USD $)	1 Year	3 Years	5 Years	10 Years
A	575	841	1,126	1,936
B	757	1,040	1,299	2,176

Expense Example, No Redemption Federated New York Municipal Income Fund (USD $)	1 Year	3 Years	5 Years	10 Years
A	575	841	1,126	1,936
B	207	640	1,099	2,176

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was 7% of the average value of its portfolio.

RISK/RETURN SUMMARY: INVESTMENTS, RISKS and PERFORMANCE

What are the Fund's Main Investment Strategies?

The Fund pursues its objective by investing its assets so that, normally (except as discussed herein), distributions of annual interest income are exempt from federal regular income tax and the personal income taxes imposed by the state of New York and New York municipalities. Interest from the Fund's investments may be subject to the federal AMT for individuals and corporations.

The Fund does not limit itself to securities of a particular maturity range. Currently, at least a majority of the Fund's assets will be invested in long-term securities (i.e., securities with stated maturities of 10 years or more).

The Fund also will invest at least a majority of its assets in securities rated investment-grade (or unrated securities of comparable quality), and may purchase securities rated below investment-grade (or unrated securities of comparable quality), which are also known as junk bonds, up to 49% of its assets. Investment-grade securities are securities that receive investment-grade ratings (i.e., generally ratings in the first, second, third or fourth highest rating category) by a nationally recognized statistical rating organization (NRSRO) or unrated securities of comparable quality. For example, securities rated AAA, AA, A or BBB by Standard & Poor's, an NRSRO, would be rated in the first, second, third or fourth ratings category, respectively. Securities rated below investment-grade (or noninvestment-grade securities) are securities that do not receive investment-grade ratings (i.e., generally ratings below one of the four highest rating categories) by an NRSRO or unrated securities of comparable quality. For example, securities rated B or BB by Standard & Poor's, an NRSRO, would be noninvestment-grade securities. The Fund does not have a specific minimum quality rating.

The securities in which the Fund may principally invest include tax-exempt securities, which may include, for example, general obligation bonds, special revenue bonds, private activity bonds, tax-increment financing bonds, municipal leases, zero-coupon securities, inverse floaters, municipal mortgage-backed securities and planned amortization classes. Certain of the tax-exempt securities in which the Fund invests may be subject to credit enhancement.

The Fund also may principally invest in derivative contracts (such as, for example, futures contracts, option contracts and swap contracts) and hybrid instruments to implement its investment strategies as more fully described in this Prospectus.

The Fund also may invest in certain securities or other investments as described in this Prospectus (such as market discount bonds, credit default swaps and other derivative transactions) that will likely cause the Fund to realize a limited amount of ordinary income or short-term capital gains (which are treated as ordinary income for federal income tax purposes).

Because the Fund refers to New York municipal investments in its name, it has an investment policy that it will normally invest its assets so that at least 80% of the income that it distributes will be exempt from federal regular income tax and the personal income taxes imposed by the state of New York and New York municipalities. This policy may not be changed without shareholder approval.

What are the Main Risks of Investing in the Fund?

All mutual funds take investment risks. Therefore, it is possible to lose money by investing in the Fund. The primary factors that may reduce the Fund's returns include:

• Interest Rate Risk. Prices of fixed-income securities (including tax-exempt securities) generally fall when interest rates rise. Interest rate changes have a greater effect on prices of fixed-income securities with longer durations.

• Issuer Credit Risk. It is possible that interest or principal on securities will not be paid when due. Noninvestment-grade securities generally have a higher default risk than investment-grade securities. Such non-payment or default may reduce the value of the Fund's portfolio holdings, its share price and its performance.

• Counterparty Credit Risk. A party to a transaction involving the Fund may fail to meet its obligations. This could cause the Fund to lose money or to lose the benefit of the transaction or prevent the Fund from selling or buying other securities to implement its investment strategies.

• Liquidity Risk. Certain securities in which the Fund invests may be less readily marketable and may be subject to greater fluctuation in price than other securities. These features may make it more difficult to sell or buy a security at a favorable price or time. Noninvestment-grade securities generally have less liquidity than investment-grade securities. Liquidity risk also refers to the possibility that the Fund may not be able to sell a security or close out a derivative contract when it wants to. Over-the-counter derivative contracts generally carry greater liquidity risk than exchange-traded contracts.

• Tax Risk. In order to be tax-exempt, tax-exempt securities must meet certain legal requirements. Failure to meet such requirements may cause the interest received and distributed by the Fund to shareholders to be taxable. The federal income tax treatment of payments in respect of certain derivative contracts is unclear. The Fund also may invest in market discount bonds, enter into credit default swap arrangements and other derivative transactions, and engage in other permissible activities that will likely cause the Fund to realize a limited amount of ordinary income or short-term capital gains (which are treated as ordinary income for federal income tax purposes). Consequently, for each of these reasons, the Fund may receive payments, and make distributions, that are treated as ordinary income for federal income tax purposes. Income from the Fund also may be subject to AMT.

• Leverage Risk. Leverage risk is created when an investment, which includes, for example, a derivative contract, exposes the Fund to a level of risk that exceeds the amount invested. Changes in the value of such an investment magnify the Fund's risk of loss and potential for gain. Investments can have these same results if their returns are based on a multiple of a specified index, security or other benchmark.

• Call Risk. The Fund's performance may be adversely affected by the possibility that an issuer of a security held by the Fund may redeem the security prior to maturity at a price below or above its current market value.

• Sector Risk. Since the Fund invests at least a majority of its assets in a portfolio of: (1) long-term New York tax-exempt securities; and (2) investment-grade New York tax-exempt securities, the Fund may be subject to additional risks compared to funds that invest in multiple states. New York's economy is relatively diversified across the manufacturing, agriculture and service sectors. New York City, however, is a major component of the state's economy and is heavily dependent on the historically volatile financial, real estate and insurance industries. A substantial part of the Fund's portfolio also may be comprised of securities issued or credit enhanced by companies in similar businesses or with other similar characteristics. As a result, the Fund will be more susceptible to any economic, business, political or other developments which generally affect these issuers or entities.

• Prepayment Risk. When homeowners prepay their mortgages in response to lower interest rates, the Fund will be required to reinvest the proceeds at the lower interest rates available. Also, when interest rates fall, the price of municipal mortgage-backed securities may not rise to as great an extent as that of other fixed-income securities.

• Credit Enhancement Risk. The securities in which the Fund invests may be subject to credit enhancement (for example, guarantees, letters of credit or bond insurance). If the credit quality of the credit enhancement provider (for example, a bank or bond insurer) is downgraded, the rating on a security credit enhanced by such credit enhancement provider also may be downgraded. Having multiple securities credit enhanced by the same enhancement provider will increase the adverse effects on the Fund that are likely to result from a downgrading of, or a default by, such an enhancement provider. Adverse developments in the banking or bond insurance industries also may negatively affect the Fund.

• Non-Diversification Risk. The Fund is non-diversified. Compared to diversified mutual funds, it may invest a higher percentage of its assets among fewer issuers of portfolio securities. This increases the Fund's risk by magnifying the impact (positively or negatively) that any one issuer has on the Fund's Share price and performance.

• Risk Associated with Noninvestment-Grade Securities. The Fund may invest a portion of its assets in securities that are below investment-grade quality (which are also known as junk bonds), which may be subject to greater economic, credit and liquidity risks than investment-grade securities.

• Risk Related to the Economy. Lower-grade bond returns are sensitive to changes in the economy. The value of the Fund's portfolio may decline in tandem with a drop in the overall value of the stock market based on negative developments in the U.S. and global economies.

• Risk of Investing in Derivative Contracts and Hybrid Instruments. Derivative contracts and hybrid instruments involve risks different from, or possibly greater than, risks associated with investing directly in securities and other traditional investments. Specific risk issues related to the use of such contracts and instruments include valuation and tax issues, increased potential for losses and/or costs to the Fund, and a potential reduction in gains to the Fund. Each of these issues is described in greater detail in this Prospectus. Derivative contracts and hybrid instruments may also involve other risks described in this Prospectus or the Fund's Statement of Additional Information (SAI), such as interest rate, credit, liquidity and leverage risks.

• Technology Risk. The Adviser uses various technology in managing the Fund, consistent with its investment objective and strategy described in this Prospectus. For example, proprietary and third-party data and systems are utilized to support decision making for the Fund.  Data imprecision, software or other technology malfunctions, programming inaccuracies and similar circumstances may impair the performance of these systems, which may negatively affect Fund performance.

The Shares offered by this Prospectus are not deposits or obligations of any bank, are not endorsed or guaranteed by any bank and are not insured or guaranteed by the U.S. government, the Federal Deposit Insurance Corporation, the Federal Reserve Board or any other government agency.

Performance: Bar Chart and Table

Risk/Return Bar Chart

The bar chart and performance table below reflect historical performance data for the Fund and are intended to help you analyze the Fund's investment risks in light of its historical returns. The bar chart shows the variability of the Fund's A class total returns on a calendar year-by-year basis. The Average Annual Total Return Table shows returns for each class averaged over the stated periods, and includes comparative performance information. The Fund's performance will fluctuate, and past performance (before and after taxes) is not necessarily an indication of future results. Updated performance information for the Fund is available under the "Products" section at FederatedInvestors.com or by calling 1-800-341-7400.

Federated New York Municipal Income Fund - A Class

The total returns shown in the bar chart do not reflect the payment of any sales charges or recurring shareholder account fees. If these charges or fees had been included, the returns shown would have been lower.

The Fund's A class total return for the nine-month period from January 1, 2013 to September 30, 2013, was (3.65)%.

Within the periods shown in the bar chart, the Fund's A class highest quarterly return was 8.10% (quarter ended September 30, 2009). Its lowest quarterly return was (5.77)% (quarter ended September 30, 2008).

Average Annual Total Return Table

In addition to Return Before Taxes, Return After Taxes is shown for the Fund's A class to illustrate the effect of federal taxes on Fund returns. After-tax returns are shown only for the A class and after-tax returns for the B class will differ from those shown below for the A class. Actual after-tax returns depend on each investor's personal tax situation, and are likely to differ from those shown. After-tax returns are calculated using a standard set of assumptions. The stated returns assume the highest historical federal income and capital gains tax rates. These after-tax returns do not reflect the effect of any applicable state and local taxes. After-tax returns are not relevant to investors holding Shares through tax-deferred programs, such as a 401(k) plan, an Individual Retirement Account (IRA) or other tax-advantaged investment plan.

(For the Period Ended December 31, 2012)

Average Annual Total Returns Federated New York Municipal Income Fund		1 Year	5 Years	10 Years
A		2.16%	3.69%	3.71%
A Return After Taxes on Distributions		2.16%	3.69%	3.71%
A Return After Taxes on Distributions and Sale of Fund Shares		2.57%	3.69%	3.74%
B		0.61%	3.51%	3.56%
S&P Municipal Bond New York Index (reflects no deduction for fees, expenses or taxes)	[1]	6.65%	5.67%	5.13%
S&P Municipal Bond NY, Investment Grade, 3-Year Plus Sub-Index (reflects no deduction for fees, expenses or taxes)	[2]	1.07%	1.35%	1.69%
Morningstar Municipal New York Funds Category Average	[3]	8.30%	5.33%	4.46%

[1] The Fund has adopted a Distribution (12b-1) Plan for its Class A Shares pursuant to which the A class of the Fund may incur or charge a Distribution (12b-1) fee of up to a maximum amount of 0.05%. No such fee is currently incurred or charged by the A class of the Fund. The A class of the Fund will not incur or charge such a Distribution (12b-1) fee until such time as approved by the Fund's Board of Trustees (the "Trustees").

[2] The Adviser and its affiliates have voluntarily agreed to waive their fees and/or reimburse expenses so that the total annual fund operating expenses (excluding Acquired Fund Fees and Expenses, extraordinary expenses, and proxy-related expenses paid by the Fund, if any) paid by the Fund's A class and B class (after the voluntary waivers and/or reimbursements) will not exceed 0.76% and 1.52% (the "Fee Limit"), respectively, up to but not including the later of (the "Termination Date"): (a) November 1, 2014; or (b) the date of the Fund's next effective Prospectus. While the Adviser and its affiliates currently do not anticipate terminating or increasing these arrangements prior to the Termination Date, these arrangements may only be terminated or the Fee Limit increased prior to the Termination Date with the agreement of the Fund's Board of Trustees.

[1] The S&P Municipal Bond New York Index (NY Index) consists of bonds in the S&P Municipal Bond Index (Main Index) that have been issued by the state of New York or local governments or state or local government entities within New York. The Main Index is a broad, comprehensive, market value-weighted index composed of approximately 55,000 bond issues that are exempt from U.S. federal income taxes or subject to the alternative minimum tax (AMT). Eligibility criteria for inclusion in the Main Index include, but are not limited to: the bond issuer must be a state (including the Commonwealth of Puerto Rico and U.S. territories) or a local government or a state or local government entity where interest on the bond is exempt from U.S. federal income taxes or subject to the AMT; the bond must be held by a mutual fund for which Standard & Poor's Securities Evaluations, Inc. provides prices; it must be denominated in U.S. dollars and have a minimum par amount of $2 million; and the bond must have a minimum term to maturity and/or call date greater than or equal to one calendar month. The Main Index is rebalanced monthly.

[2] The S&P Municipal Bond NY, Investment Grade, 3-Year Plus Sub-Index (NYIG Index) represents the portion of the NY Index composed solely of bonds that are rated BBB-/Baa3 or higher with remaining maturities of more than three years that are not subject to AMT.

[3] Morningstar figures represent the average of the total returns reported by all the mutual funds designated by Morningstar as falling into the respective category indicated. Funds designated within the Morningstar Municipal New York Funds Category Average include those that invest at least 80% of assets in New York Municipal debt and have durations of more than 7 years (or, if duration is unavailable, average maturities of more than 12 years).

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Federated Michigan Intermediate Municipal Trust

Federated Michigan Intermediate Municipal Trust (the "Fund")

RISK/RETURN SUMMARY: INVESTMENT OBJECTIVE

The Fund's investment objective is to provide current income exempt from federal regular income tax and personal income taxes imposed by the state of Michigan and Michigan municipalities.

RISK/RETURN SUMMARY: FEES AND EXPENSES

This table describes the fees and expenses that you may pay if you buy and hold Class A Shares (A) of the Fund. You may qualify for certain sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in certain classes (e.g., A class) of Federated funds. More information about these and other discounts is available from your financial professional and in the "What Do Shares Cost?" section of the Prospectus on page 14.

Shareholder Fees (fees paid directly from your investment)

Shareholder Fees	Federated Michigan Intermediate Municipal Trust A
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	3.00%
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, as applicable)	none
Maximum Sales Charge (Load) Imposed on Reinvested Dividends (and other Distributions) (as a percentage of offering price)	none
Redemption Fee (as a percentage of amount redeemed, if applicable)	none
Exchange Fee	none

Annual Fund Operating Expenses (expenses that you pay each year as a

percentage of the value of your investment)

Annual Fund Operating Expenses		Federated Michigan Intermediate Municipal Trust A
Management Fee		0.40%
Distribution (12b-1) Fee		none
Other Expenses		0.49%
Total Annual Fund Operating Expenses		0.89%
Fee Waivers and/or Expense Reimbursements	[1]	0.14%
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements		0.75%

Example

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 for the time periods indicated and then redeem all of your Shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that operating expenses are as shown in the table above and remain the same. Although your actual costs and returns may be higher or lower, based on these assumptions your costs would be:

Expense Example (USD $)	Federated Michigan Intermediate Municipal Trust A
1 Year	388
3 Years	575
5 Years	778
10 Years	1,363

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was 8% of the average value of its portfolio.

RISK/RETURN SUMMARY: INVESTMENTS, RISKS and PERFORMANCE

What are the Fund's Main Investment Strategies?

The Fund pursues its objective by investing at least a majority of its assets in a portfolio of tax-exempt securities so that, normally (except as discussed herein), distributions of annual interest income are exempt from federal regular income tax and the personal income taxes imposed by the state of Michigan and Michigan municipalities. Interest from the Fund's investments may be subject to the federal alternative minimum tax (AMT) for individuals and corporations.

The Fund's portfolio securities will be investment grade or of comparable quality. Investment-grade securities are securities that receive investment grade ratings (i.e., generally ratings in the first, second, third or fourth highest rating category) by a nationally recognized statistical ratings organization (NRSRO) or unrated securities of comparable quality. For example, securities rated AAA, AA, A or BBB by Standard & Poor's, an NRSRO, would be rated in the first, second, third or fourth highest rating category, respectively.

The Fund's dollar-weighted average portfolio maturity is between three and ten years, and its average-weighted duration is between three and seven years.

The securities in which the Fund may principally invest include tax-exempt securities, which may include, for example, general obligation bonds, special revenue bonds, private activity bonds, tax-increment financing bonds, municipal leases, zero-coupon securities, inverse floaters, municipal mortgage-backed securities and planned amortization classes. Certain of the tax-exempt securities in which the Fund invests may be subject to credit enhancement.

The Fund also may principally invest in derivative contracts (such as, for example, futures contracts, option contracts and swap contracts) and hybrid instruments to implement its investment strategies as more fully described in this Prospectus.

The Fund also may invest in certain securities or other investments as described in this Prospectus (such as market discount bonds, credit default swaps and other derivative transactions) that will likely cause the Fund to realize a limited amount of ordinary income or short-term capital gains (which are treated as ordinary income for federal income tax purposes).

Because the Fund refers to Michigan municipal investments in its name, it has an investment policy that it will normally invest its assets so that at least 80% of the income that it distributes will be exempt from federal regular income tax and the personal income taxes imposed by the state of Michigan and Michigan municipalities. This policy may not be changed without shareholder approval.

What are the Main Risks of Investing in the Fund?

All mutual funds take investment risks. Therefore, it is possible to lose money by investing in the Fund. The primary factors that may reduce the Fund's returns include:

• Interest Rate Risk. Prices of fixed-income securities (including tax-exempt securities) generally fall when interest rates rise. Interest rate changes have a greater effect on prices of fixed-income securities with longer durations.

• Issuer Credit Risk. It is possible that interest or principal on securities will not be paid when due. Such non-payment or default may reduce the value of the Fund's portfolio holdings, its share price and its performance.

• Counterparty Credit Risk. A party to a transaction involving the Fund may fail to meet its obligations. This could cause the Fund to lose money or to lose the benefit of the transaction or prevent the Fund from selling or buying other securities to implement its investment strategies.

• Liquidity Risk. Certain securities in which the Fund invests may be less readily marketable and may be subject to greater fluctuation in price than other securities. These features may make it more difficult to sell or buy a security at a favorable price or time. Liquidity risk also refers to the possibility that the Fund may not be able to sell a security or close out a derivative contract when it wants to. Over-the-counter derivative contracts generally carry greater liquidity risk than exchange-traded contracts.

• Tax Risk. In order to be tax-exempt, tax-exempt securities must meet certain legal requirements. Failure to meet such requirements may cause the interest received and distributed by the Fund to shareholders to be taxable. The federal income tax treatment of payments in respect of certain derivative contracts is unclear. The Fund also may invest in market discount bonds, enter into credit default swap arrangements and other derivative transactions, and engage in other permissible activities that will likely cause the Fund to realize a limited amount of ordinary income or short-term capital gains (which are treated as ordinary income for federal income tax purposes). Consequently, for each of these reasons, the Fund may receive payments, and make distributions, that are treated as ordinary income for federal income tax purposes. Income from the Fund also may be subject to AMT.

• Leverage Risk. Leverage risk is created when an investment, which includes, for example, a derivative contract, exposes the Fund to a level of risk that exceeds the amount invested. Changes in the value of such an investment magnify the Fund's risk of loss and potential for gain. Investments can have these same results if their returns are based on a multiple of a specified index, security or other benchmark.

• Call Risk. The Fund's performance may be adversely affected by the possibility that an issuer of a security held by the Fund may redeem the security prior to maturity at a price below or above its current market value.

• Sector Risk. Since the Fund invests at least a majority of its assets in a portfolio of Michigan tax-exempt securities, the Fund may be subject to additional risks compared to funds that invest in multiple states. Although it has diversified, Michigan's economy is still heavily dependent upon certain industries, especially automobile, manufacturing and related industries. Any downturns in these industries may adversely affect the economy of the state. A substantial part of the Fund's portfolio may be comprised of securities issued or credit enhanced by companies in similar businesses, or with other similar characteristics. As a result, the Fund will be more susceptible to any economic, business, political or other developments which generally affect these entities.

• Prepayment Risk. When homeowners prepay their mortgages in response to lower interest rates, the Fund will be required to reinvest the proceeds at the lower interest rates available. Also, when interest rates fall, the price of municipal mortgage-backed securities may not rise to as great an extent as that of other fixed-income securities.

• Credit Enhancement Risk. The securities in which the Fund invests may be subject to credit enhancement (for example, guarantees, letters of credit or bond insurance). If the credit quality of the credit enhancement provider (for example, a bank or bond insurer) is downgraded, the rating on a security credit enhanced by such credit enhancement provider also may be downgraded. Having multiple securities credit enhanced by the same enhancement provider will increase the adverse effects on the Fund that are likely to result from a downgrading of, or a default by, such an enhancement provider. Adverse developments in the banking or bond insurance industries also may negatively affect the Fund.

• Non-Diversification Risk. The Fund is non-diversified. Compared to diversified mutual funds, it may invest a higher percentage of its assets among fewer issuers of portfolio securities. This increases the Fund's risk by magnifying the impact (positively or negatively) that any one issuer has on the Fund's Share price and performance.

• Risk Related to the Economy. Lower-grade bond returns are sensitive to changes in the economy. The value of the Fund's portfolio may decline in tandem with a drop in the overall value of the stock market based on negative developments in the U.S. and global economies.

• Risk of Investing in Derivative Contracts and Hybrid Instruments. Derivative contracts and hybrid instruments involve risks different from, or possibly greater than, risks associated with investing directly in securities and other traditional investments. Specific risk issues related to the use of such contracts and instruments include valuation and tax issues, increased potential for losses and/or costs to the Fund, and a potential reduction in gains to the Fund. Each of these issues is described in greater detail in this Prospectus. Derivative contracts and hybrid instruments may also involve other risks described in this Prospectus or the Fund's Statement of Additional Information (SAI), such as interest rate, credit, liquidity and leverage risks.

• Technology Risk. The Adviser uses various technology in managing the Fund, consistent with its investment objective and strategy described in this Prospectus. For example, proprietary and third-party data and systems are utilized to support decision making for the Fund.  Data imprecision, software or other technology malfunctions, programming inaccuracies and similar circumstances may impair the performance of these systems, which may negatively affect Fund performance.

The Shares offered by this Prospectus are not deposits or obligations of any bank, are not endorsed or guaranteed by any bank and are not insured or guaranteed by the U.S. government, the Federal Deposit Insurance Corporation, the Federal Reserve Board or any other government agency.

Performance: Bar Chart and Table

Risk/Return Bar Chart

The bar chart and performance table below reflect historical performance data for the Fund and are intended to help you analyze the Fund's investment risks in light of its historical returns. The bar chart shows the variability of the Fund's A class total returns on a calendar year-by-year basis. The Average Annual Total Return Table shows returns averaged over the stated periods, and includes comparative performance information. The Fund's performance will fluctuate, and past performance (before and after taxes) is not necessarily an indication of future results. Updated performance information for the Fund is available under the "Products" section at FederatedInvestors.com or by calling 1-800-341-7400.

Federated Michigan Intermediate Municipal Trust - A Class

The total returns shown in the bar chart do not reflect payment of any sales charges or recurring shareholder account fees. If these charges or fees had been included, the returns shown would have been lower.

The Fund's A class total return for the nine-month period from January 1, 2013 to September 30, 2013, was (2.79)%.

Within the periods shown in the bar chart, the Fund's A class highest quarterly return was 5.33% (quarter ended September 30, 2009). Its lowest quarterly return was (3.14)% (quarter ended December 31, 2010).

Average Annual Total Return Table

In addition to Return Before Taxes, Return After Taxes is shown for the Fund's A class to illustrate the effect of federal taxes on Fund returns. Actual after-tax returns depend on each investor's personal tax situation, and are likely to differ from those shown. After-tax returns are calculated using a standard set of assumptions. The stated returns assume the highest historical federal income and capital gains tax rates. These after-tax returns do not reflect the effect of any applicable state and local taxes. After-tax returns are not relevant to investors holding shares through tax-deferred programs, such as a 401(k) plan, an Individual Retirement Account (IRA) or other tax-advantaged investment plan.

(For the Periods Ended December 31, 2012)

Average Annual Total Returns Federated Michigan Intermediate Municipal Trust		1 Year	5 Years	10 Years
A		2.29%	4.27%	3.81%
A Return After Taxes on Distributions		2.25%	4.26%	3.80%
A Return After Taxes on Distributions and Sale of Fund Shares		2.60%	4.17%	3.79%
S&P Municipal Bond Intermediate Index (reflects no deduction of fees, expenses or taxes)	[1]	5.34%	6.12%	5.14%
Morningstar Municipal Single State Intermediate Funds Category Average	[2]	4.72%	4.53%	3.74%

[1] Effective November 1, 2013, the Adviser and its affiliates have voluntarily agreed to waive their fees and/or reimburse expenses so that the total annual fund operating expenses (excluding Acquired Fund Fees and Expenses, extraordinary expenses and proxy-related expenses paid by the Fund, if any) paid by the Fund's A class (after the voluntary waivers and/or reimbursements) will not exceed 0.75% (the "Fee Limit") up to but not including the later of (the "Termination Date"): (a) November 1, 2014; or (b) the date of the Fund's next effective Prospectus. While the Adviser and its affiliates currently do not anticipate terminating or increasing these arrangements prior to the Termination Date, these arrangements may only be terminated or the Fee Limit increased prior to the Termination Date with the agreement of the Fund's Board of Trustees.

[1] The S&P Municipal Bond Intermediate Index consists of bonds in the S&P Municipal Bond Index (Main Index) with a minimum maturity of three years and a maximum maturity of up to, but not including, 15 years as measured from the rebalancing date of the Main Index. The Main Index is a broad, comprehensive, market value-weighted index composed of approximately 55,000 bond issues that are exempt from U.S. federal income taxes or subject to the alternative minimum tax (AMT). Eligibility criteria for inclusion in the Main Index include, but are not limited to: the bond issuer must be a state (including the Commonwealth of Puerto Rico and U.S. territories) or a local government or a state or local government entity where interest on the bond is exempt from U.S. federal income taxes or subject to the AMT; the bond must be held by a mutual fund for which Standard & Poor's Securities Evaluations, Inc. provides prices; it must be denominated in U.S. dollars and have a minimum par amount of $2 million; and the bond must have a minimum term to maturity and/or call date greater than or equal to one calendar month. The Main Index is rebalanced monthly.

[2] Morningstar figures represent the average of the total returns reported by all the mutual funds designed by Morningstar as falling into the respective category indicated.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	Federated Municipal Securities Income Trust
Prospectus Date	rr_ProspectusDate	Oct. 31, 2013
Federated New York Municipal Income Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Federated New York Municipal Income Fund (the "Fund")
Objective [Heading]	rr_ObjectiveHeading	RISK/RETURN SUMMARY: INVESTMENT OBJECTIVE
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund's investment objective is to provide current income exempt from federal regular income tax (federal regular income tax does not include the federal alternative minimum tax (AMT)) and the personal income taxes imposed by the state of New York and New York municipalities.
Expense [Heading]	rr_ExpenseHeading	RISK/RETURN SUMMARY: FEES AND EXPENSES
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay if you buy and hold Class A Shares (A) and Class B Shares (B) of the Fund. You may qualify for certain sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in certain classes (e.g., A class) of Federated funds. More information about these and other discounts is available from your financial professional and in the "What Do Shares Cost" section of the Prospectus on page 15.
Shareholder Fees Caption [Text]	rr_ShareholderFeesCaption	Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	November 1, 2014
Fee Waiver Or Reimbursement Over Assets Later Of Termination Or Next Effective Prosepectus	fmsit1_FeeWaiverOrReimbursementOverAssetsLaterOfTerminationOrNextEffectiveProsepectus	up to but not including the later of (the "Termination Date"): (a) November 1, 2014; or (b) the date of the Fund's next effective Prospectus.
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	Portfolio Turnover
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was 7% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	7.00%
Expense Breakpoint Discounts [Text]	rr_ExpenseBreakpointDiscounts	You may qualify for certain sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in certain classes (e.g., A class) of Federated funds.
Expense Breakpoint, Minimum Investment Required [Amount]	rr_ExpenseBreakpointMinimumInvestmentRequiredAmount	$ 100,000
Expense Example [Heading]	rr_ExpenseExampleHeading	Example
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 for the time periods indicated and then redeem all of your Shares at the end of those periods. Expenses assuming no redemption are also shown. The Example also assumes that your investment has a 5% return each year and that operating expenses are as shown in the table above and remain the same. Although your actual costs and returns may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading]	rr_StrategyHeading	RISK/RETURN SUMMARY: INVESTMENTS, RISKS and PERFORMANCE What are the Fund's Main Investment Strategies?
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	The Fund pursues its objective by investing its assets so that, normally (except as discussed herein), distributions of annual interest income are exempt from federal regular income tax and the personal income taxes imposed by the state of New York and New York municipalities. Interest from the Fund's investments may be subject to the federal AMT for individuals and corporations. The Fund does not limit itself to securities of a particular maturity range. Currently, at least a majority of the Fund's assets will be invested in long-term securities (i.e., securities with stated maturities of 10 years or more). The Fund also will invest at least a majority of its assets in securities rated investment-grade (or unrated securities of comparable quality), and may purchase securities rated below investment-grade (or unrated securities of comparable quality), which are also known as junk bonds, up to 49% of its assets. Investment-grade securities are securities that receive investment-grade ratings (i.e., generally ratings in the first, second, third or fourth highest rating category) by a nationally recognized statistical rating organization (NRSRO) or unrated securities of comparable quality. For example, securities rated AAA, AA, A or BBB by Standard & Poor's, an NRSRO, would be rated in the first, second, third or fourth ratings category, respectively. Securities rated below investment-grade (or noninvestment-grade securities) are securities that do not receive investment-grade ratings (i.e., generally ratings below one of the four highest rating categories) by an NRSRO or unrated securities of comparable quality. For example, securities rated B or BB by Standard & Poor's, an NRSRO, would be noninvestment-grade securities. The Fund does not have a specific minimum quality rating. The securities in which the Fund may principally invest include tax-exempt securities, which may include, for example, general obligation bonds, special revenue bonds, private activity bonds, tax-increment financing bonds, municipal leases, zero-coupon securities, inverse floaters, municipal mortgage-backed securities and planned amortization classes. Certain of the tax-exempt securities in which the Fund invests may be subject to credit enhancement. The Fund also may principally invest in derivative contracts (such as, for example, futures contracts, option contracts and swap contracts) and hybrid instruments to implement its investment strategies as more fully described in this Prospectus. The Fund also may invest in certain securities or other investments as described in this Prospectus (such as market discount bonds, credit default swaps and other derivative transactions) that will likely cause the Fund to realize a limited amount of ordinary income or short-term capital gains (which are treated as ordinary income for federal income tax purposes). Because the Fund refers to New York municipal investments in its name, it has an investment policy that it will normally invest its assets so that at least 80% of the income that it distributes will be exempt from federal regular income tax and the personal income taxes imposed by the state of New York and New York municipalities. This policy may not be changed without shareholder approval.
Risk [Heading]	rr_RiskHeading	What are the Main Risks of Investing in the Fund?
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	All mutual funds take investment risks. Therefore, it is possible to lose money by investing in the Fund. The primary factors that may reduce the Fund's returns include: Interest Rate Risk. Prices of fixed-income securities (including tax-exempt securities) generally fall when interest rates rise. Interest rate changes have a greater effect on prices of fixed-income securities with longer durations. Issuer Credit Risk. It is possible that interest or principal on securities will not be paid when due. Noninvestment-grade securities generally have a higher default risk than investment-grade securities. Such non-payment or default may reduce the value of the Fund's portfolio holdings, its share price and its performance. Counterparty Credit Risk. A party to a transaction involving the Fund may fail to meet its obligations. This could cause the Fund to lose money or to lose the benefit of the transaction or prevent the Fund from selling or buying other securities to implement its investment strategies. Liquidity Risk. Certain securities in which the Fund invests may be less readily marketable and may be subject to greater fluctuation in price than other securities. These features may make it more difficult to sell or buy a security at a favorable price or time. Noninvestment-grade securities generally have less liquidity than investment-grade securities. Liquidity risk also refers to the possibility that the Fund may not be able to sell a security or close out a derivative contract when it wants to. Over-the-counter derivative contracts generally carry greater liquidity risk than exchange-traded contracts. Tax Risk. In order to be tax-exempt, tax-exempt securities must meet certain legal requirements. Failure to meet such requirements may cause the interest received and distributed by the Fund to shareholders to be taxable. The federal income tax treatment of payments in respect of certain derivative contracts is unclear. The Fund also may invest in market discount bonds, enter into credit default swap arrangements and other derivative transactions, and engage in other permissible activities that will likely cause the Fund to realize a limited amount of ordinary income or short-term capital gains (which are treated as ordinary income for federal income tax purposes). Consequently, for each of these reasons, the Fund may receive payments, and make distributions, that are treated as ordinary income for federal income tax purposes. Income from the Fund also may be subject to AMT. Leverage Risk. Leverage risk is created when an investment, which includes, for example, a derivative contract, exposes the Fund to a level of risk that exceeds the amount invested. Changes in the value of such an investment magnify the Fund's risk of loss and potential for gain. Investments can have these same results if their returns are based on a multiple of a specified index, security or other benchmark. Call Risk. The Fund's performance may be adversely affected by the possibility that an issuer of a security held by the Fund may redeem the security prior to maturity at a price below or above its current market value. Sector Risk. Since the Fund invests at least a majority of its assets in a portfolio of: (1) long-term New York tax-exempt securities; and (2) investment-grade New York tax-exempt securities, the Fund may be subject to additional risks compared to funds that invest in multiple states. New York's economy is relatively diversified across the manufacturing, agriculture and service sectors. New York City, however, is a major component of the state's economy and is heavily dependent on the historically volatile financial, real estate and insurance industries. A substantial part of the Fund's portfolio also may be comprised of securities issued or credit enhanced by companies in similar businesses or with other similar characteristics. As a result, the Fund will be more susceptible to any economic, business, political or other developments which generally affect these issuers or entities. Prepayment Risk. When homeowners prepay their mortgages in response to lower interest rates, the Fund will be required to reinvest the proceeds at the lower interest rates available. Also, when interest rates fall, the price of municipal mortgage-backed securities may not rise to as great an extent as that of other fixed-income securities. Credit Enhancement Risk. The securities in which the Fund invests may be subject to credit enhancement (for example, guarantees, letters of credit or bond insurance). If the credit quality of the credit enhancement provider (for example, a bank or bond insurer) is downgraded, the rating on a security credit enhanced by such credit enhancement provider also may be downgraded. Having multiple securities credit enhanced by the same enhancement provider will increase the adverse effects on the Fund that are likely to result from a downgrading of, or a default by, such an enhancement provider. Adverse developments in the banking or bond insurance industries also may negatively affect the Fund. Non-Diversification Risk. The Fund is non-diversified. Compared to diversified mutual funds, it may invest a higher percentage of its assets among fewer issuers of portfolio securities. This increases the Fund's risk by magnifying the impact (positively or negatively) that any one issuer has on the Fund's Share price and performance. Risk Associated with Noninvestment-Grade Securities. The Fund may invest a portion of its assets in securities that are below investment-grade quality (which are also known as junk bonds), which may be subject to greater economic, credit and liquidity risks than investment-grade securities. Risk Related to the Economy. Lower-grade bond returns are sensitive to changes in the economy. The value of the Fund's portfolio may decline in tandem with a drop in the overall value of the stock market based on negative developments in the U.S. and global economies. Risk of Investing in Derivative Contracts and Hybrid Instruments. Derivative contracts and hybrid instruments involve risks different from, or possibly greater than, risks associated with investing directly in securities and other traditional investments. Specific risk issues related to the use of such contracts and instruments include valuation and tax issues, increased potential for losses and/or costs to the Fund, and a potential reduction in gains to the Fund. Each of these issues is described in greater detail in this Prospectus. Derivative contracts and hybrid instruments may also involve other risks described in this Prospectus or the Fund's Statement of Additional Information (SAI), such as interest rate, credit, liquidity and leverage risks. Technology Risk. The Adviser uses various technology in managing the Fund, consistent with its investment objective and strategy described in this Prospectus. For example, proprietary and third-party data and systems are utilized to support decision making for the Fund.  Data imprecision, software or other technology malfunctions, programming inaccuracies and similar circumstances may impair the performance of these systems, which may negatively affect Fund performance. The Shares offered by this Prospectus are not deposits or obligations of any bank, are not endorsed or guaranteed by any bank and are not insured or guaranteed by the U.S. government, the Federal Deposit Insurance Corporation, the Federal Reserve Board or any other government agency.
Risk Lose Money [Text]	rr_RiskLoseMoney	All mutual funds take investment risks. Therefore, it is possible to lose money by investing in the Fund.
Risk Nondiversified Status [Text]	rr_RiskNondiversifiedStatus	Non-Diversification Risk. The Fund is non-diversified. Compared to diversified mutual funds, it may invest a higher percentage of its assets among fewer issuers of portfolio securities. This increases the Fund's risk by magnifying the impact (positively or negatively) that any one issuer has on the Fund's Share price and performance.
Risk Not Insured Depository Institution [Text]	rr_RiskNotInsuredDepositoryInstitution	The Shares offered by this Prospectus are not deposits or obligations of any bank, are not endorsed or guaranteed by any bank and are not insured or guaranteed by the U.S. government, the Federal Deposit Insurance Corporation, the Federal Reserve Board or any other government agency.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance: Bar Chart and Table Risk/Return Bar Chart
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The bar chart and performance table below reflect historical performance data for the Fund and are intended to help you analyze the Fund's investment risks in light of its historical returns. The bar chart shows the variability of the Fund's A class total returns on a calendar year-by-year basis. The Average Annual Total Return Table shows returns for each class averaged over the stated periods, and includes comparative performance information. The Fund's performance will fluctuate, and past performance (before and after taxes) is not necessarily an indication of future results. Updated performance information for the Fund is available under the "Products" section at FederatedInvestors.com or by calling 1-800-341-7400.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The bar chart shows the variability of the Fund's A class total returns on a calendar year-by-year basis.
Performance Availability Phone [Text]	rr_PerformanceAvailabilityPhone	1-800-341-7400
Performance Availability Website Address [Text]	rr_PerformanceAvailabilityWebSiteAddress	FederatedInvestors.com
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	The Fund's performance will fluctuate, and past performance (before and after taxes) is not necessarily an indication of future results.
Bar Chart [Heading]	rr_BarChartHeading	Federated New York Municipal Income Fund - A Class
Bar Chart Does Not Reflect Sales Loads [Text]	rr_BarChartDoesNotReflectSalesLoads	The total returns shown in the bar chart do not reflect the payment of any sales charges or recurring shareholder account fees. If these charges or fees had been included, the returns shown would have been lower.
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	The total returns shown in the bar chart do not reflect the payment of any sales charges or recurring shareholder account fees. If these charges or fees had been included, the returns shown would have been lower. The Fund's A class total return for the nine-month period from January 1, 2013 to September 30, 2013, was (3.65)%. Within the periods shown in the bar chart, the Fund's A class highest quarterly return was 8.10% (quarter ended September 30, 2009). Its lowest quarterly return was (5.77)% (quarter ended September 30, 2008).
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Return Table
Performance Table Uses Highest Federal Rate	rr_PerformanceTableUsesHighestFederalRate	After-tax returns are calculated using a standard set of assumptions. The stated returns assume the highest historical federal income and capital gains tax rates. These after-tax returns do not reflect the effect of any applicable state and local taxes.
Performance Table Not Relevant to Tax Deferred	rr_PerformanceTableNotRelevantToTaxDeferred	After-tax returns are not relevant to investors holding Shares through tax-deferred programs, such as a 401(k) plan, an Individual Retirement Account (IRA) or other tax-advantaged investment plan.
Performance Table One Class of after Tax Shown [Text]	rr_PerformanceTableOneClassOfAfterTaxShown	After-tax returns are shown only for the A class and after-tax returns for the B class will differ from those shown below for the A class.
Performance Table Narrative	rr_PerformanceTableNarrativeTextBlock	In addition to Return Before Taxes, Return After Taxes is shown for the Fund's A class to illustrate the effect of federal taxes on Fund returns. After-tax returns are shown only for the A class and after-tax returns for the B class will differ from those shown below for the A class. Actual after-tax returns depend on each investor's personal tax situation, and are likely to differ from those shown. After-tax returns are calculated using a standard set of assumptions. The stated returns assume the highest historical federal income and capital gains tax rates. These after-tax returns do not reflect the effect of any applicable state and local taxes. After-tax returns are not relevant to investors holding Shares through tax-deferred programs, such as a 401(k) plan, an Individual Retirement Account (IRA) or other tax-advantaged investment plan. (For the Period Ended December 31, 2012)
Federated New York Municipal Income Fund | A
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	4.50%
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, as applicable)	rr_MaximumDeferredSalesChargeOverOther	none
Maximum Sales Charge (Load) Imposed on Reinvested Dividends (and other Distributions) (as a percentage of offering price)	rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther	none
Redemption Fee (as a percentage of amount redeemed, if applicable)	rr_RedemptionFeeOverRedemption	none
Exchange Fee	rr_ExchangeFeeOverRedemption	none
Management Fee	rr_ManagementFeesOverAssets	0.40%
Distribution (12b-1) Fee	rr_DistributionAndService12b1FeesOverAssets	none	[1]
Other Expenses	rr_OtherExpensesOverAssets	0.89%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.29%
Fee Waivers and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	0.53%	[2]
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements	rr_NetExpensesOverAssets	0.76%
1 Year	rr_ExpenseExampleYear01	575
3 Years	rr_ExpenseExampleYear03	841
5 Years	rr_ExpenseExampleYear05	1,126
10 Years	rr_ExpenseExampleYear10	1,936
1 Year	rr_ExpenseExampleNoRedemptionYear01	575
3 Years	rr_ExpenseExampleNoRedemptionYear03	841
5 Years	rr_ExpenseExampleNoRedemptionYear05	1,126
10 Years	rr_ExpenseExampleNoRedemptionYear10	1,936
2003	rr_AnnualReturn2003	5.74%
2004	rr_AnnualReturn2004	4.18%
2005	rr_AnnualReturn2005	4.30%
2006	rr_AnnualReturn2006	5.16%
2007	rr_AnnualReturn2007	(0.60%)
2008	rr_AnnualReturn2008	(10.75%)
2009	rr_AnnualReturn2009	17.03%
2010	rr_AnnualReturn2010	1.82%
2011	rr_AnnualReturn2011	10.35%
2012	rr_AnnualReturn2012	7.01%
Year to Date Return, Label	rr_YearToDateReturnLabel	The Fund's A class total return for the nine-month period
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Sep. 30, 2013
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	(3.65%)
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest quarterly return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Sep. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	8.10%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest quarterly return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Sep. 30, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(5.77%)
1 Year	rr_AverageAnnualReturnYear01	2.16%
5 Years	rr_AverageAnnualReturnYear05	3.69%
10 Years	rr_AverageAnnualReturnYear10	3.71%
Federated New York Municipal Income Fund | B
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, as applicable)	rr_MaximumDeferredSalesChargeOverOther	5.50%
Maximum Sales Charge (Load) Imposed on Reinvested Dividends (and other Distributions) (as a percentage of offering price)	rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther	none
Redemption Fee (as a percentage of amount redeemed, if applicable)	rr_RedemptionFeeOverRedemption	none
Exchange Fee	rr_ExchangeFeeOverRedemption	none
Management Fee	rr_ManagementFeesOverAssets	0.40%
Distribution (12b-1) Fee	rr_DistributionAndService12b1FeesOverAssets	0.75%
Other Expenses	rr_OtherExpensesOverAssets	0.89%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	2.04%
Fee Waivers and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	0.52%	[2]
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.52%
1 Year	rr_ExpenseExampleYear01	757
3 Years	rr_ExpenseExampleYear03	1,040
5 Years	rr_ExpenseExampleYear05	1,299
10 Years	rr_ExpenseExampleYear10	2,176
1 Year	rr_ExpenseExampleNoRedemptionYear01	207
3 Years	rr_ExpenseExampleNoRedemptionYear03	640
5 Years	rr_ExpenseExampleNoRedemptionYear05	1,099
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 2,176
1 Year	rr_AverageAnnualReturnYear01	0.61%
5 Years	rr_AverageAnnualReturnYear05	3.51%
10 Years	rr_AverageAnnualReturnYear10	3.56%
Federated New York Municipal Income Fund | Return After Taxes on Distributions | A
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	2.16%
5 Years	rr_AverageAnnualReturnYear05	3.69%
10 Years	rr_AverageAnnualReturnYear10	3.71%
Federated New York Municipal Income Fund | Return After Taxes on Distributions and Sale of Fund Shares | A
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	2.57%
5 Years	rr_AverageAnnualReturnYear05	3.69%
10 Years	rr_AverageAnnualReturnYear10	3.74%
Federated New York Municipal Income Fund | S&P Municipal Bond New York Index (reflects no deduction for fees, expenses or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	6.65%	[3]
5 Years	rr_AverageAnnualReturnYear05	5.67%	[3]
10 Years	rr_AverageAnnualReturnYear10	5.13%	[3]
Federated New York Municipal Income Fund | S&P Municipal Bond NY, Investment Grade, 3-Year Plus Sub-Index (reflects no deduction for fees, expenses or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	1.07%	[4]
5 Years	rr_AverageAnnualReturnYear05	1.35%	[4]
10 Years	rr_AverageAnnualReturnYear10	1.69%	[4]
Federated New York Municipal Income Fund | Morningstar Municipal New York Funds Category Average
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	8.30%	[5]
5 Years	rr_AverageAnnualReturnYear05	5.33%	[5]
10 Years	rr_AverageAnnualReturnYear10	4.46%	[5]

[1] The Fund has adopted a Distribution (12b-1) Plan for its Class A Shares pursuant to which the A class of the Fund may incur or charge a Distribution (12b-1) fee of up to a maximum amount of 0.05%. No such fee is currently incurred or charged by the A class of the Fund. The A class of the Fund will not incur or charge such a Distribution (12b-1) fee until such time as approved by the Fund's Board of Trustees (the "Trustees").

[2] The Adviser and its affiliates have voluntarily agreed to waive their fees and/or reimburse expenses so that the total annual fund operating expenses (excluding Acquired Fund Fees and Expenses, extraordinary expenses, and proxy-related expenses paid by the Fund, if any) paid by the Fund's A class and B class (after the voluntary waivers and/or reimbursements) will not exceed 0.76% and 1.52% (the "Fee Limit"), respectively, up to but not including the later of (the "Termination Date"): (a) November 1, 2014; or (b) the date of the Fund's next effective Prospectus. While the Adviser and its affiliates currently do not anticipate terminating or increasing these arrangements prior to the Termination Date, these arrangements may only be terminated or the Fee Limit increased prior to the Termination Date with the agreement of the Fund's Board of Trustees.

[3] The S&P Municipal Bond New York Index (NY Index) consists of bonds in the S&P Municipal Bond Index (Main Index) that have been issued by the state of New York or local governments or state or local government entities within New York. The Main Index is a broad, comprehensive, market value-weighted index composed of approximately 55,000 bond issues that are exempt from U.S. federal income taxes or subject to the alternative minimum tax (AMT). Eligibility criteria for inclusion in the Main Index include, but are not limited to: the bond issuer must be a state (including the Commonwealth of Puerto Rico and U.S. territories) or a local government or a state or local government entity where interest on the bond is exempt from U.S. federal income taxes or subject to the AMT; the bond must be held by a mutual fund for which Standard & Poor's Securities Evaluations, Inc. provides prices; it must be denominated in U.S. dollars and have a minimum par amount of $2 million; and the bond must have a minimum term to maturity and/or call date greater than or equal to one calendar month. The Main Index is rebalanced monthly.

[4] The S&P Municipal Bond NY, Investment Grade, 3-Year Plus Sub-Index (NYIG Index) represents the portion of the NY Index composed solely of bonds that are rated BBB-/Baa3 or higher with remaining maturities of more than three years that are not subject to AMT.

[5] Morningstar figures represent the average of the total returns reported by all the mutual funds designated by Morningstar as falling into the respective category indicated. Funds designated within the Morningstar Municipal New York Funds Category Average include those that invest at least 80% of assets in New York Municipal debt and have durations of more than 7 years (or, if duration is unavailable, average maturities of more than 12 years).

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	Federated Municipal Securities Income Trust
Prospectus Date	rr_ProspectusDate	Oct. 31, 2013
Federated Pennsylvania Municipal Income Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Federated Pennsylvania Municipal Income Fund (the "Fund")
Objective [Heading]	rr_ObjectiveHeading	RISK/RETURN SUMMARY: INVESTMENT OBJECTIVE
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund's investment objective is to provide current income exempt from federal regular income tax (federal regular income tax does not include the federal alternative minimum tax (AMT)) and the personal income taxes imposed by the state of Pennsylvania and Pennsylvania municipalities.
Expense [Heading]	rr_ExpenseHeading	RISK/RETURN SUMMARY: FEES AND EXPENSES
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay if you buy and hold Class A Shares (A) and Class B Shares (B) of the Fund. You may qualify for certain sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in certain classes (e.g., A class) of Federated funds. More information about these and other discounts is available from your financial professional and in the "What Do Shares Cost?" section of the Prospectus on page 15.
Shareholder Fees Caption [Text]	rr_ShareholderFeesCaption	Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	November 1, 2014
Fee Waiver Or Reimbursement Over Assets Later Of Termination Or Next Effective Prosepectus	fmsit1_FeeWaiverOrReimbursementOverAssetsLaterOfTerminationOrNextEffectiveProsepectus	up to but not including the later of (the "Termination Date"): (a) November 1, 2014; or (b) the date of the Fund's next effective Prospectus.
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	Portfolio Turnover
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was 7% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	7.00%
Expense Breakpoint Discounts [Text]	rr_ExpenseBreakpointDiscounts	You may qualify for certain sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in certain classes (e.g., A class) of Federated funds.
Expense Breakpoint, Minimum Investment Required [Amount]	rr_ExpenseBreakpointMinimumInvestmentRequiredAmount	$ 100,000
Expense Example [Heading]	rr_ExpenseExampleHeading	Example
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 for the time periods indicated and then redeem all of your Shares at the end of those periods. Expenses assuming no redemption are also shown. The Example also assumes that your investment has a 5% return each year and that operating expenses are as shown in the table above and remain the same. Although your actual costs and returns may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading]	rr_StrategyHeading	RISK/RETURN SUMMARY: INVESTMENTS, RISKS and PERFORMANCE What are the Fund's Main Investment Strategies?
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	The Fund pursues its objective by investing its assets so that, normally (except as discussed herein), distributions of annual interest income are exempt from federal regular income tax and the Commonwealth of Pennsylvania personal income tax. Interest from the Fund's investments may be subject to the federal AMT for individuals and corporations. The Fund does not limit itself to securities of a particular maturity range. Currently, at least a majority of the Fund's assets will be invested in long-term securities (i.e., securities with stated maturities of 10 years or more). The Fund also will invest at least a majority of its assets in securities rated investment-grade (or unrated securities of comparable quality), and may purchase securities rated below investment-grade (or unrated securities of comparable quality), which are also known as junk bonds, up to 49% of its assets. Investment-grade securities are securities that receive investment-grade ratings (i.e., generally ratings in the first, second, third or fourth highest rating category) by a nationally recognized statistical rating organization (NRSRO) or unrated securities of comparable quality. For example, securities rated AAA, AA, A or BBB by Standard & Poor's, an NRSRO, would be rated in the first, second, third or fourth ratings category, respectively. Securities rated below investment-grade (or noninvestment-grade securities) are securities that do not receive investment-grade ratings (i.e., generally ratings below one of the four highest rating categories) by an NRSRO or unrated securities of comparable quality. For example, securities rated B or BB by Standard & Poor's, an NRSRO, would be noninvestment-grade securities. The Fund does not have a specific minimum quality rating. The securities in which the Fund may principally invest include tax-exempt securities, which may include, for example, general obligation bonds, special revenue bonds, private activity bonds, tax-increment financing bonds, municipal leases, zero-coupon securities, inverse floaters, municipal mortgage-backed securities and planned amortization classes. Certain of the tax-exempt securities in which the Fund invests may be subject to credit enhancement. The Fund also may principally invest in derivative contracts (such as, for example, futures contracts, option contracts and swap contracts) and hybrid instruments to implement its investment strategies as more fully described in this Prospectus. The Fund also may invest in certain securities or other investments as described in this Prospectus (such as market discount bonds, credit default swaps and other derivative transactions) that will likely cause the Fund to realize a limited amount of ordinary income or short-term capital gains (which are treated as ordinary income for federal income tax purposes). Because the Fund refers to Pennsylvania municipal investments in its name, it has an investment policy that it will normally invest its assets so that at least 80% of the income that it distributes will be exempt from federal regular income tax and the Commonwealth of Pennsylvania personal income tax. This policy may not be changed without shareholder approval.
Risk [Heading]	rr_RiskHeading	What are the Main Risks of Investing in the Fund?
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	All mutual funds take investment risks. Therefore, it is possible to lose money by investing in the Fund. The primary factors that may reduce the Fund's returns include: Interest Rate Risk. Prices of fixed-income securities (including tax-exempt securities) generally fall when interest rates rise. Interest rate changes have a greater effect on prices of fixed-income securities with longer durations. Issuer Credit Risk. It is possible that interest or principal on securities will not be paid when due. Noninvestment-grade securities generally have a higher default risk than investment-grade securities. Such non-payment or default may reduce the value of the Fund's portfolio holdings, its share price and its performance. Counterparty Credit Risk. A party to a transaction involving the Fund may fail to meet its obligations. This could cause the Fund to lose money or to lose the benefit of the transaction or prevent the Fund from selling or buying other securities to implement its investment strategies. Liquidity Risk. Certain securities in which the Fund invests may be less readily marketable and may be subject to greater fluctuation in price than other securities. These features may make it more difficult to sell or buy a security at a favorable price or time. Noninvestment-grade securities generally have less liquidity than investment-grade securities. Liquidity risk also refers to the possibility that the Fund may not be able to sell a security or close out a derivative contract when it wants to. Over-the-counter derivative contracts generally carry greater liquidity risk than exchange-traded contracts. Tax Risk. In order to be tax-exempt, tax-exempt securities must meet certain legal requirements. Failure to meet such requirements may cause the interest received and distributed by the Fund to shareholders to be taxable. The federal income tax treatment of payments in respect of certain derivative contracts is unclear. The Fund also may invest in market discount bonds, enter into credit default swap arrangements and other derivative transactions, and engage in other permissible activities that will likely cause the Fund to realize a limited amount of ordinary income or short-term capital gains (which are treated as ordinary income for federal income tax purposes). Consequently, for each of these reasons, the Fund may receive payments, and make distributions, that are treated as ordinary income for federal income tax purposes. Income from the Fund also may be subject to AMT. Leverage Risk. Leverage risk is created when an investment, which includes, for example, a derivative contract, exposes the Fund to a level of risk that exceeds the amount invested. Changes in the value of such an investment magnify the Fund's risk of loss and potential for gain. Investments can have these same results if their returns are based on a multiple of a specified index, security or other benchmark. Call Risk. The Fund's performance may be adversely affected by the possibility that an issuer of a security held by the Fund may redeem the security prior to maturity at a price below or above its current market value. Sector Risk. Since the Fund invests at least a majority of its assets in a portfolio of: (1) long-term Pennsylvania tax-exempt securities; and (2) investment-grade Pennsylvania tax-exempt securities, the Fund may be subject to additional risks compared to funds that invest in multiple states. Pennsylvania's economy has diversified away from the concentration in heavy industry and manufacturing, which existed prior to the downsizing of the steel industry, and improved its mixture of technology-based businesses, health care services and education services. Despite the improvements in its employment base, Pennsylvania is still subject to the cyclical impact which an economic downturn has on the manufacturing sector. A substantial part of the Fund's portfolio also may be comprised of securities issued or credit enhanced by companies in similar businesses or with other similar characteristics. As a result, the Fund will be more susceptible to any economic, business, political or other developments which generally affect these issuers or entities. Prepayment Risk. When homeowners prepay their mortgages in response to lower interest rates, the Fund will be required to reinvest the proceeds at the lower interest rates available. Also, when interest rates fall, the price of municipal mortgage-backed securities may not rise to as great an extent as that of other fixed-income securities. Credit Enhancement Risk. The securities in which the Fund invests may be subject to credit enhancement (for example, guarantees, letters of credit or bond insurance). If the credit quality of the credit enhancement provider (for example, a bank or bond insurer) is downgraded, the rating on a security credit enhanced by such credit enhancement provider also may be downgraded. Having multiple securities credit enhanced by the same enhancement provider will increase the adverse effects on the Fund that are likely to result from a downgrading of, or a default by, such an enhancement provider. Adverse developments in the banking or bond insurance industries also may negatively affect the Fund. Non-Diversification Risk. The Fund is non-diversified. Compared to diversified mutual funds, it may invest a higher percentage of its assets among fewer issuers of portfolio securities. This increases the Fund's risk by magnifying the impact (positively or negatively) that any one issuer has on the Fund's Share price and performance. Risk Associated with Noninvestment-Grade Securities. The Fund may invest a portion of its assets in securities that are below investment-grade quality (which are also known as junk bonds), which may be subject to greater economic, credit and liquidity risks than investment-grade securities. Risk Related to the Economy. Lower-grade bond returns are sensitive to changes in the economy. The value of the Fund's portfolio may decline in tandem with a drop in the overall value of the stock market based on negative developments in the U.S. and global economies. Risk of Investing in Derivative Contracts and Hybrid Instruments. Derivative contracts and hybrid instruments involve risks different from, or possibly greater than, risks associated with investing directly in securities and other traditional investments. Specific risk issues related to the use of such contracts and instruments include valuation and tax issues, increased potential for losses and/or costs to the Fund, and a potential reduction in gains to the Fund. Each of these issues is described in greater detail in this Prospectus. Derivative contracts and hybrid instruments may also involve other risks described in this Prospectus or the Fund's Statement of Additional Information (SAI), such as interest rate, credit, liquidity and leverage risks. Technology Risk. The Adviser uses various technology in managing the Fund, consistent with its investment objective and strategy described in this Prospectus. For example, proprietary and third-party data and systems are utilized to support decision making for the Fund.  Data imprecision, software or other technology malfunctions, programming inaccuracies and similar circumstances may impair the performance of these systems, which may negatively affect Fund performance. The Shares offered by this Prospectus are not deposits or obligations of any bank, are not endorsed or guaranteed by any bank and are not insured or guaranteed by the U.S. government, the Federal Deposit Insurance Corporation, the Federal Reserve Board or any other government agency.
Risk Lose Money [Text]	rr_RiskLoseMoney	All mutual funds take investment risks. Therefore, it is possible to lose money by investing in the Fund.
Risk Nondiversified Status [Text]	rr_RiskNondiversifiedStatus	Non-Diversification Risk. The Fund is non-diversified. Compared to diversified mutual funds, it may invest a higher percentage of its assets among fewer issuers of portfolio securities. This increases the Fund's risk by magnifying the impact (positively or negatively) that any one issuer has on the Fund's Share price and performance.
Risk Not Insured Depository Institution [Text]	rr_RiskNotInsuredDepositoryInstitution	The Shares offered by this Prospectus are not deposits or obligations of any bank, are not endorsed or guaranteed by any bank and are not insured or guaranteed by the U.S. government, the Federal Deposit Insurance Corporation, the Federal Reserve Board or any other government agency.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance: Bar Chart and Table Risk/Return Bar Chart
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The bar chart and performance table below reflect historical performance data for the Fund and are intended to help you analyze the Fund's investment risks in light of its historical returns. The bar chart shows the variability of the Fund's A class total returns on a calendar year-by-year basis. The Average Annual Total Return Table shows returns averaged over the stated periods and includes comparative performance information. The Fund's performance will fluctuate, and past performance (before and after taxes) is not necessarily an indication of future results. Updated performance information for the Fund is available under the "Products" section at FederatedInvestors.com or by calling 1-800-341-7400.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The bar chart shows the variability of the Fund's A class total returns on a calendar year-by-year basis.
Performance Availability Phone [Text]	rr_PerformanceAvailabilityPhone	1-800-341-7400
Performance Availability Website Address [Text]	rr_PerformanceAvailabilityWebSiteAddress	FederatedInvestors.com
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	The Fund's performance will fluctuate, and past performance (before and after taxes) is not necessarily an indication of future results.
Bar Chart [Heading]	rr_BarChartHeading	Federated Pennsylvania Municipal Income Fund - A Class
Bar Chart Does Not Reflect Sales Loads [Text]	rr_BarChartDoesNotReflectSalesLoads	The total returns shown in the bar chart do not reflect the payment of any sales charges or recurring shareholder account fees. If these charges or fees had been included, the returns shown would have been lower.
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	The total returns shown in the bar chart do not reflect the payment of any sales charges or recurring shareholder account fees. If these charges or fees had been included, the returns shown would have been lower. The Fund's A class total return for the nine-month period from January 1, 2013 to September 30, 2013, was (3.69)%. Within the periods shown in the bar chart, the Fund's A class highest quarterly return was 7.17% (quarter ended September 30, 2009). Its lowest quarterly return was (4.85)% (quarter ended December 31, 2008).
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Return Table
Performance Table Uses Highest Federal Rate	rr_PerformanceTableUsesHighestFederalRate	After-tax returns are calculated using a standard set of assumptions. The stated returns assume the highest historical federal income and capital gains tax rates. These after-tax returns do not reflect the effect of any applicable state and local taxes.
Performance Table Not Relevant to Tax Deferred	rr_PerformanceTableNotRelevantToTaxDeferred	After-tax returns are not relevant to investors holding Shares through tax-deferred programs, such as a 401(k) plan, an Individual Retirement Account (IRA) or other tax-advantaged investment plan.
Performance Table One Class of after Tax Shown [Text]	rr_PerformanceTableOneClassOfAfterTaxShown	After-tax returns are shown only for the A class and after tax returns for the B class will differ from those shown below for the A class.
Performance Table Narrative	rr_PerformanceTableNarrativeTextBlock	In addition to Return Before Taxes, Return After Taxes is shown for the Fund's A class to illustrate the effect of federal taxes on Fund returns. After-tax returns are shown only for the A class and after tax returns for the B class will differ from those shown below for the A class. Actual after-tax returns depend on each investor's personal tax situation, and are likely to differ from those shown. After-tax returns are calculated using a standard set of assumptions. The stated returns assume the highest historical federal income and capital gains tax rates. These after-tax returns do not reflect the effect of any applicable state and local taxes. After-tax returns are not relevant to investors holding Shares through tax-deferred programs, such as a 401(k) plan, an Individual Retirement Account (IRA) or other tax-advantaged investment plan. (For the Period Ended December 31, 2012)
Federated Pennsylvania Municipal Income Fund | A
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	4.50%
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, as applicable)	rr_MaximumDeferredSalesChargeOverOther	none
Maximum Sales Charge (Load) Imposed on Reinvested Dividends (and other Distributions) (as a percentage of offering price)	rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther	none
Redemption Fee (as a percentage of amount redeemed, if applicable)	rr_RedemptionFeeOverRedemption	none
Exchange Fee	rr_ExchangeFeeOverRedemption	none
Management Fee	rr_ManagementFeesOverAssets	0.40%
Distribution (12b-1) Fee	rr_DistributionAndService12b1FeesOverAssets	none	[1]
Other Expenses	rr_OtherExpensesOverAssets	0.45%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.85%
Fee Waivers and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	0.10%	[2]
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements	rr_NetExpensesOverAssets	0.75%
1 Year	rr_ExpenseExampleYear01	533
3 Years	rr_ExpenseExampleYear03	709
5 Years	rr_ExpenseExampleYear05	900
10 Years	rr_ExpenseExampleYear10	1,452
1 Year	rr_ExpenseExampleNoRedemptionYear01	533
3 Years	rr_ExpenseExampleNoRedemptionYear03	709
5 Years	rr_ExpenseExampleNoRedemptionYear05	900
10 Years	rr_ExpenseExampleNoRedemptionYear10	1,452
2003	rr_AnnualReturn2003	5.09%
2004	rr_AnnualReturn2004	4.23%
2005	rr_AnnualReturn2005	3.78%
2006	rr_AnnualReturn2006	4.51%
2007	rr_AnnualReturn2007	0.12%
2008	rr_AnnualReturn2008	(10.94%)
2009	rr_AnnualReturn2009	15.59%
2010	rr_AnnualReturn2010	1.62%
2011	rr_AnnualReturn2011	9.70%
2012	rr_AnnualReturn2012	7.21%
Year to Date Return, Label	rr_YearToDateReturnLabel	The Fund's A class total return for the nine-month period
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Sep. 30, 2013
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	(3.69%)
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest quarterly return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Sep. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	7.17%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest quarterly return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(4.85%)
1 Year	rr_AverageAnnualReturnYear01	2.39%
5 Years	rr_AverageAnnualReturnYear05	3.27%
10 Years	rr_AverageAnnualReturnYear10	3.41%
Federated Pennsylvania Municipal Income Fund | B
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, as applicable)	rr_MaximumDeferredSalesChargeOverOther	5.50%
Maximum Sales Charge (Load) Imposed on Reinvested Dividends (and other Distributions) (as a percentage of offering price)	rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther	none
Redemption Fee (as a percentage of amount redeemed, if applicable)	rr_RedemptionFeeOverRedemption	none
Exchange Fee	rr_ExchangeFeeOverRedemption	none
Management Fee	rr_ManagementFeesOverAssets	0.40%
Distribution (12b-1) Fee	rr_DistributionAndService12b1FeesOverAssets	0.75%
Other Expenses	rr_OtherExpensesOverAssets	0.45%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.60%
Fee Waivers and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	0.08%	[2]
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.52%
1 Year	rr_ExpenseExampleYear01	713
3 Years	rr_ExpenseExampleYear03	905
5 Years	rr_ExpenseExampleYear05	1,071
10 Years	rr_ExpenseExampleYear10	1,699
1 Year	rr_ExpenseExampleNoRedemptionYear01	163
3 Years	rr_ExpenseExampleNoRedemptionYear03	505
5 Years	rr_ExpenseExampleNoRedemptionYear05	871
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 1,699
1 Year	rr_AverageAnnualReturnYear01	0.78%
5 Years	rr_AverageAnnualReturnYear05	3.07%
10 Years	rr_AverageAnnualReturnYear10	3.24%
Federated Pennsylvania Municipal Income Fund | Return After Taxes on Distributions | A
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	2.39%
5 Years	rr_AverageAnnualReturnYear05	3.27%
10 Years	rr_AverageAnnualReturnYear10	3.41%
Federated Pennsylvania Municipal Income Fund | Return After Taxes on Distributions and Sale of Fund Shares | A
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	2.78%
5 Years	rr_AverageAnnualReturnYear05	3.35%
10 Years	rr_AverageAnnualReturnYear10	3.50%
Federated Pennsylvania Municipal Income Fund | S&P Municipal Bond Pennsylvania Index (reflects no deduction for fees, expenses or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	6.88%	[3]
5 Years	rr_AverageAnnualReturnYear05	5.74%	[3]
10 Years	rr_AverageAnnualReturnYear10	5.18%	[3]
Federated Pennsylvania Municipal Income Fund | S&P Municipal Bond PA, Investment Grade, 3-Year Plus Sub-Index (reflects no deduction for fees, expenses or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	8.00%	[4]
5 Years	rr_AverageAnnualReturnYear05	6.51%	[4]
10 Years	rr_AverageAnnualReturnYear10	5.56%	[4]
Federated Pennsylvania Municipal Income Fund | Morningstar Municipal Pennsylvania Funds Category Average
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	7.36%	[5]
5 Years	rr_AverageAnnualReturnYear05	5.08%	[5]
10 Years	rr_AverageAnnualReturnYear10	4.25%	[5]

[1] The Fund has adopted a Distribution (12b-1) Plan for its Class A shares pursuant to which the A class of the Fund may incur or charge a Distribution (12b-1) fee of up to a maximum amount of 0.05%. No such fee is currently incurred or charged by the A class of the Fund. The A class of the Fund will not incur or charge such a Distribution (12b-1) fee until such time as approved by the Fund's Board of Trustees (the “Trustees”).

[2] The Adviser and its affiliates have voluntarily agreed to waive their fees and/or reimburse expenses so that the total annual fund operating expenses (excluding Acquired Fund Fees and Expenses, extraordinary expenses, and proxy-related expenses, paid by the Fund, if any) paid by the Fund's A class and B class (after the voluntary waivers and/or reimbursements) will not exceed 0.75% and 1.52% (the "Fee Limit"), respectively, up to but not including the later of (the "Termination Date"): (a) November 1, 2014; or (b) the date of the Fund's next effective Prospectus. While the Adviser and its affiliates currently do not anticipate terminating or increasing these arrangements prior to the Termination Date, these arrangements may only be terminated or the Fee Limit increased prior to the Termination Date with the agreement of the Fund's Board of Trustees.

[3] The S&P Municipal Bond Pennsylvania Index (PA Index) consists of bonds in the S&P Municipal Bond Index (Main Index) that have been issued by the Commonwealth of Pennsylvania or local governments or state or local government entities within Pennsylvania. The Main Index is a broad, comprehensive, market value-weighted index composed of approximately 55,000 bond issues that are exempt from U.S. federal income taxes or subject to the alternative minimum tax (AMT). Eligibility criteria for inclusion in the Main Index include, but are not limited to: the bond issuer must be a state (including the Commonwealth of Puerto Rico and U.S. territories) or a local government or a state or local entity where interest on the bond is exempt from U.S. federal income taxes or subject to the AMT; the bond must be held by a mutual fund for which Standard & Poor's Securities Evaluations, Inc. provides prices; it must be denominated in U.S. dollars and have a minimum par amount of $2 million; and the bond must have a minimum term to maturity and/or call date greater than or equal to one calendar month. The Main Index is rebalanced monthly.

[4] The S&P Municipal Bond PA, Investment Grade, 3-Year Plus Sub-Index represents the return of the portion of the PA Index composed solely of bonds that are rated at least BBB with remaining maturities of more than three years that are not subject to AMT.

[5] Morningstar figures represent the average of the total returns reported by all the mutual funds designated by Morningstar as falling into the respective category indicated. Funds designated within the Morningstar Municipal Pennsylvania Funds Category Average include those that invest at least 80% of assets in Pennsylvania municipal debt and can include long-, intermediate- and short-duration portfolios.

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Federated Ohio Municipal Income Fund

Federated Ohio Municipal Income Fund (the "Fund")

RISK/RETURN SUMMARY: INVESTMENT OBJECTIVE

The Fund's investment objective is to provide current income exempt from federal regular income tax (federal regular income tax does not include the federal alternative minimum tax (AMT)) and the personal income taxes imposed by the state of Ohio and Ohio municipalities.

RISK/RETURN SUMMARY: FEES AND EXPENSES

This table describes the fees and expenses that you may pay if you buy and hold Class A Shares (A) and Class F Shares (F) of the Fund. You may qualify for certain sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 and $1,000,000 in certain classes (e.g., A class and F class, respectively) of Federated funds. More information about these and other discounts is available from your financial professional and in the "What Do Shares Cost?" section of the Prospectus on page 14.

Shareholder Fees (fees paid directly from your investment)

Shareholder Fees Federated Ohio Municipal Income Fund	A	F
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	4.50%	1.00%
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, as applicable)	none	1.00%
Maximum Sales Charge (Load) Imposed on Reinvested Dividends (and other Distributions) (as a percentage of offering price)	none	none
Redemption Fee (as a percentage of amount redeemed, if applicable)	none	none
Exchange Fee	none	none

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses Federated Ohio Municipal Income Fund		A		F
Management Fee		0.40%		0.40%
Distribution (12b-1) Fee		none	[1]	0.40%
Other Expenses		0.49%		0.49%
Total Annual Fund Operating Expenses		0.89%		1.29%
Fee Waivers and/or Expense Reimbursements	[2]	0.14%		0.39%
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements		0.75%		0.90%

Example

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 for the time periods indicated and then redeem all of your Shares at the end of those periods. Expenses assuming no redemption are also shown. The Example also assumes that your investment has a 5% return each year and that operating expenses are as shown in the table above and remain the same. Although your actual costs and returns may be higher or lower, based on these assumptions your costs would be:

Expense Example Federated Ohio Municipal Income Fund (USD $)	1 Year	3 Years	5 Years	10 Years
A	537	721	921	1,497
F	230	505	800	1,641

Expense Example, No Redemption Federated Ohio Municipal Income Fund (USD $)	1 Year	3 Years	5 Years	10 Years
A	537	721	921	1,497
F	130	405	700	1,541

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was 15% of the average value of its portfolio.

RISK/RETURN SUMMARY: INVESTMENTS, RISKS and PERFORMANCE

What are the Fund's Main Investment Strategies?

The Fund pursues its objective by investing its assets so that, normally (except as discussed herein), distributions of annual interest income are exempt from federal regular income tax and the personal income taxes imposed by the state of Ohio and Ohio municipalities. Interest from the Fund’s investments may be subject to the federal AMT for individuals and corporations.

The Fund does not limit itself to securities of a particular maturity range. Currently, at least a majority of the Fund’s assets will be invested in long-term securities (i.e., securities with stated maturities of 10 years or more).

The Fund also will invest at least a majority of its assets in securities rated investment-grade (or unrated securities of comparable quality) and may purchase securities rated below investment-grade (or unrated securities of comparable quality), which are also known as junk bonds, up to 49% of its assets. Investment-grade securities are securities that receive investment-grade ratings (i.e., generally ratings in the first, second, third or fourth highest rating category) by a nationally recognized statistical rating organization (NRSRO) or unrated securities of comparable quality. For example, securities rated AAA, AA, A or BBB by Standard & Poor’s, an NRSRO,would be rated in the first, second, third or fourth ratings category, respectively. Securities rated below investment-grade (or noninvestment-grade securities) are securities that do not receive investment-grade ratings (i.e., generally ratings below one of the four highest rating categories) by an NRSRO or unrated securities of comparable quality. For example, securities rated B or BB by Standard & Poor’s, an NRSRO, would be noninvestment-grade securities. The Fund does not have a specific minimum quality rating.

The securities in which the Fund may principally invest include tax-exempt securities, which may include, for example, general obligation bonds, special revenue bonds, private activity bonds, tax-increment financing bonds, municipal leases, zero-coupon securities, inverse floaters, municipal mortgage-backed securities and planned amortization classes. Certain of the tax-exempt securities in which the Fund invests may be subject to credit enhancement.

The Fund also may principally invest in derivative contracts (such as, for example, futures contracts, option contracts and swap contracts) and hybrid instruments to implement its investment strategies as more fully described in this Prospectus.

The Fund also may invest in certain securities or other investments as described in this Prospectus (such as market discount bonds, credit default swaps and other derivative transactions) that will likely cause the Fund to realize a limited amount of ordinary income or short-term capital gains (which are treated as ordinary income for federal income tax purposes).

Because the Fund refers to Ohio municipal investments in its name, it has an investment policy that it will normally invest its assets so that at least 80% of the income that it distributes will be exempt from federal regular income tax and the personal income taxes imposed by the state of Ohio and Ohio municipalities. This policy may not be changed without shareholder approval.

What are the Main Risks of Investing in the Fund?

All mutual funds take investment risks. Therefore, it is possible to lose money by investing in the Fund. The primary factors that may reduce the Fund’s returns include:

• Interest Rate Risk. Prices of fixed-income securities (including tax-exempt securities) generally fall when interest rates rise. Interest rate changes have a greater effect on prices of fixed-income securities with longer durations.

• Issuer Credit Risk. It is possible that interest or principal on securities will not be paid when due. Noninvestment-grade securities generally have a higher default risk than investment-grade securities. Such non-payment or default may reduce the value of the Fund’s portfolio holdings, its share price and its performance.

• Counterparty Credit Risk. A party to a transaction involving the Fund may fail to meet its obligations. This could cause the Fund to lose money or to lose the benefit of the transaction or prevent the Fund from selling or buying other securities to implement its investment strategies.

• Liquidity Risk. Certain securities in which the Fund invests may be less readily marketable and may be subject to greater fluctuation in price than other securities. These features may make it more difficult to sell or buy a security at a favorable price or time. Noninvestment-grade securities generally have less liquidity than investment-grade securities. Liquidity risk also refers to the possibility that the Fund may not be able to sell a security or close out a derivative contract when it wants to. Over-the-counter derivative contracts generally carry greater liquidity risk than exchange-traded contracts.

• Tax Risk. In order to be tax-exempt, tax-exempt securities must meet certain legal requirements. Failure to meet such requirements may cause the interest received and distributed by the Fund to shareholders to be taxable. The federal income tax treatment of payments in respect of certain derivative contracts is unclear. The Fund also may invest in market discount bonds, enter into credit default swap arrangements and other derivative transactions, and engage in other permissible activities that will likely cause the Fund to realize a limited amount of ordinary income or short-term capital gains (which are treated as ordinary income for federal income tax purposes). Consequently, for each of these reasons, the Fund may receive payments, and make distributions, that are treated as ordinary income for federal income tax purposes. Income from the Fund also may be subject to AMT.

• Leverage Risk. Leverage risk is created when an investment, which includes, for example, a derivative contract, exposes the Fund to a level of risk that exceeds the amount invested. Changes in the value of such an investment magnify the Fund’s risk of loss and potential for gain. Investments can have these same results if their returns are based on a multiple of a specified index, security or other benchmark.

• Call Risk. The Fund’s performance may be adversely affected by the possibility that an issuer of a security held by the Fund may redeem the security prior to maturity at a price below or above its current market value.

• Sector Risk. Since the Fund invests at least a majority of its assets in a portfolio of: (1) long-term, Ohio tax-exempt securities; and (2) investment-grade, Ohio tax-exempt securities, the Fund may be subject to additional risks compared to funds that invest in multiple states. Ohio’s economy is  relatively diversified across the manufacturing, agriculture and service sectors. However, the manufacturing sector is the dominant sector within Ohio and exposes the state to the economic dislocations which occur within cyclical industries. A substantial part of the Fund’s portfolio may be comprised of securities issued or credit enhanced by companies in similar businesses or with other similar characteristics. As a result, the Fund will be more susceptible to any economic, business, political or other developments which generally affect these issuers or entities.

• Prepayment Risk. When homeowners prepay their mortgages in response to lower interest rates, the Fund will be required to reinvest the proceeds at the lower interest rates available. Also, when interest rates fall, the price of municipal mortgage-backed securities may not rise to as great an extent as that of other fixed-income securities.

• Credit Enhancement Risk. The securities in which the Fund invests may be subject to credit enhancement (for example, guarantees, letters of credit or bond insurance). If the credit quality of the credit enhancement provider (for example, a bank or bond insurer) is downgraded, the rating on a security credit enhanced by such credit enhancement provider also may be downgraded. Having multiple securities credit enhanced by the same enhancement provider will increase the adverse effects on the Fund that are likely to result from a downgrading of, or a default by, such an enhancement provider. Adverse developments in the banking or bond insurance industries also may negatively affect the Fund.

• Non-Diversification Risk. The Fund is non-diversified. Compared to diversified mutual funds, it may invest a higher percentage of its assets among fewer issuers of portfolio securities. This increases the Fund’s risk by magnifying the impact (positively or negatively) that any one issuer has on the Fund’s Share price and performance.

• Risk Associated with Noninvestment-Grade Securities. The Fund may invest a portion of its assets in securities that are below investment-grade quality (which are also known as junk bonds), which may be subject to greater economic, credit and liquidity risks than investment-grade securities.

• Risk Related to the Economy. Lower-grade bond returns are sensitive to changes in the economy. The value of the Fund’s portfolio may decline in tandem with a drop in the overall value of the stock market based on negative developments in the U.S. and global economies.

• Risk of Investing in Derivative Contracts and Hybrid Instruments. Derivative contracts and hybrid instruments involve risks different from, or possibly greater than, risks associated with investing directly in securities and other traditional investments. Specific risk issues related to the use of such contracts and instruments include valuation and tax issues, increased potential for losses and/or costs to the Fund, and a potential reduction in gains to the Fund. Each of these issues is described in greater detail in this Prospectus. Derivative contracts and hybrid instruments may also involve other risks described in this Prospectus or the Fund’s Statement of Additional Information (SAI), such as interest rate, credit, liquidity and leverage risks.

• Technology Risk. The Adviser uses various technology in managing the Fund, consistent with its investment objective and strategy described in this Prospectus. For example, proprietary and third-party data and systems are utilized to support decision making for the Fund.  Data imprecision, software or other technology malfunctions, programming inaccuracies and similar circumstances may impair the performance of these systems, which may negatively affect Fund performance.

The Shares offered by this Prospectus are not deposits or obligations of any bank, are not endorsed or guaranteed by any bank and are not insured or guaranteed by the U.S. government, the Federal Deposit Insurance Corporation, the Federal Reserve Board or any other government agency.

Performance: Bar Chart and Table

Risk/Return Bar Chart

The bar chart and performance table below reflect historical performance data for the Fund and are intended to help you analyze the Fund's investment risks in light of its historical returns. The bar chart shows the variability of the Fund's F class total returns on a calendar year-by-year basis. The Average Annual Total Return Table shows returns averaged over the stated periods, and includes comparative performance information. The Fund's performance will fluctuate, and past performance (before and after taxes) is not necessarily an indication of future results. Updated performance information for the Fund is available under the "Products" section at FederatedInvestors.com or by calling 1-800-341-7400.

Federated Ohio Municipal Income Fund - F Class

The total returns shown in the bar chart do not reflect the payment of any sales charges or recurring shareholder account fees. If these charges or fees had been included, the returns shown would have been lower.

The Fund's F class total return for the nine-month period from January 1, 2013 to September 30, 2013, was (3.05)%.

Within the periods shown in the bar chart, the Fund's F class highest quarterly return was 5.48% (quarter ended September 30, 2009). Its lowest quarterly return was (4.13)% (quarter ended September 30, 2008).

Average Annual Total Return Table

The Fund's A class commenced operation on November 18, 2008. Accordingly, for the period prior to the commencement of operations, the performance information shown in the Average Annual Total Return table is for the Fund's F class adjusted to reflect the sales charges and expenses of the A class. In addition to Return Before Taxes, Return After Taxes is shown for the Fund's F class to illustrate the effect of federal taxes on Fund returns. After-tax returns are shown only for the F class and after tax returns for the A class will differ from those shown below for the F class. Actual after-tax returns depend on each investor's personal tax situation and are likely to differ from those shown. After-tax returns are calculated using a standard set of assumptions. The stated returns assume the highest historical federal income and capital gains tax rates. These after-tax returns do not reflect the effect of any applicable state and local taxes. After-tax returns are not relevant to investors holding Shares through tax-deferred programs, such as a 401(k) Plan an Individual Retirement Account (IRA) or other tax-advantaged investment plan.

(For the Periods Ended December 31, 2012)

Average Annual Total Returns Federated Ohio Municipal Income Fund		1 Year	5 Years	10 Years
F		4.78%	4.12%	3.94%
F Return After Taxes on Distributions		4.78%	4.12%	3.94%
F Return After Taxes on Distributions and Sale of Fund Shares		4.24%	4.04%	3.94%
A		2.19%	3.43%	3.45%
S&P Municipal Bond Ohio Index (reflects no deduction for fees, expenses or taxes)	[1]	10.23%	5.60%	8.99%
S&P Municipal Bond OH, Investment Grade, 3-Year Plus with Tobacco 2% Constrained Sub-Index (reflects no deduction for fees, expenses or taxes)	[2]	8.51%	5.74%	5.15%
Morningstar Municipal Ohio Funds Category Average	[3]	6.78%	4.72%	3.93%

[1] The Fund has adopted a Distribution (12b-1) Plan for its Class A Shares pursuant to which the A class of the Fund may incur or charge a Distribution (12b-1) fee of up to a maximum amount of 0.05%. No such fee is currently incurred or charged by the A class of the Fund. The A class of the Fund will not incur or charge such a Distribution (12b-1) fee until such time as approved by the Fund's Board of Trustees (the "Trustees").

[2] The Adviser and its affiliates have voluntarily agreed to waive their fees and/or reimburse expenses so that the total annual fund operating expenses (excluding Acquired Fund Fees and Expenses, extraordinary expenses, and proxy-related expenses paid by the Fund, if any) paid by the Fund's A class and F class (after the voluntary waivers and/or reimbursements) will not exceed 0.75% and 0.90% (the "Fee Limit"), respectively, up to but not including the later of (the "Termination Date"): (a) November 1, 2014; or (b) the date of the Fund's next effective Prospectus. While the Adviser and its affiliates currently do not anticipate terminating or increasing these arrangements prior to the Termination Date, these arrangements may only be terminated or the Fee Limit increased prior to the Termination Date with the agreement of the Trustees.

[1] The S&P Municipal Bond Ohio Index (OH Index) consists of bonds in the S&P Municipal Bond Index (Main Index) that have been issued by the state of Ohio or local governments or state or local government entities within Ohio. The Main Index is a broad, comprehensive, market value-weighted index composed of approximately 55,000 bond issues that are exempt from U.S. federal income taxes or subject to the alternative minimum tax (AMT). Eligibility criteria for inclusion in the Main Index include, but are not limited to: the bond issuer must be a state (including the Commonwealth of Puerto Rico and U.S. territories) or local government or a state or local government entity where interest on the bond is exempt from U.S. federal income taxes or subject to the AMT; the bond must be held by a mutual fund for which Standard & Poor's Securities Evaluations, Inc. provides prices; it must be denominated in U.S. dollars and have a minimum par amount of $2 million; and the bond must have a minimum term to maturity and/or call date greater than or equal to one calendar month. The Main Index is rebalanced monthly.

[2] The S&P Municipal Bond OH Investment Grade, 3-Year Plus with Tobacco 2% Constrained Sub-Index (OHIG Index) represents the portion of the OH Index composed solely of bonds that are rated BBB-/Baa3 or higher with remaining maturities of more than three years while limiting tobacco bonds to 2%, by market weighting, of the sub-index.

[3] Morningstar figures represent the average of the total returns reported by all the mutual funds designated by Morningstar as falling into the respective category indicated. Funds designated within the Morningstar Municipal Ohio Funds Category Average (MSTARMOH) include those that invest at least 80% of assets in Ohio municipal debt and can include long-, intermediate- and short-duration portfolios.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	Federated Municipal Securities Income Trust
Prospectus Date	rr_ProspectusDate	Oct. 31, 2013
Federated Municipal High Yield Advantage Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Federated Municipal High Yield Advantage Fund (the "Fund")
Objective [Heading]	rr_ObjectiveHeading	RISK/RETURN SUMMARY: INVESTMENT OBJECTIVE
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund's investment objective is to provide a high level of current income which is generally exempt from the federal regular income tax.
Expense [Heading]	rr_ExpenseHeading	RISK/RETURN SUMMARY: FEES AND EXPENSES
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay if you buy and hold the Fund's Class A Shares (A), Class B Shares (B), Class C Shares (C), Class F Shares (F) and Institutional Shares (IS). You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future at least $100,000 or $1,000,000 in certain classes (e.g., A class and F class, respectively) of Federated funds. More information about these and other discounts is available from your financial professional and in the "What Do Shares Cost?" section of the Prospectus on page 16.
Shareholder Fees Caption [Text]	rr_ShareholderFeesCaption	Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	November 1, 2014
Fee Waiver Or Reimbursement Over Assets Later Of Termination Or Next Effective Prosepectus	fmsit1_FeeWaiverOrReimbursementOverAssetsLaterOfTerminationOrNextEffectiveProsepectus	up to but not including the later of (the "Termination Date"): (a) November 1, 2014; or (b) the date of the Fund's next effective Prospectus.
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	Portfolio Turnover
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was 17% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	17.00%
Expense Breakpoint Discounts [Text]	rr_ExpenseBreakpointDiscounts	You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future at least $100,000 or $1,000,000 in certain classes (e.g., A class and F class, respectively) of Federated funds.
Expense Example [Heading]	rr_ExpenseExampleHeading	Example
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 for the time periods indicated and then redeem all of your Shares at the end of those periods. Expenses assuming no redemption are also shown. The Example also assumes that your investment has a 5% return each year and that operating expenses are as shown in the table above and remain the same. Although your actual costs and returns may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading]	rr_StrategyHeading	RISK/RETURN SUMMARY: INVESTMENTS, RISKS and PERFORMANCE What are the Fund's Main Investment Strategies?
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	The Fund pursues its objective by investing its assets so that, normally (except as discussed herein), distributions of annual interest income are exempt from federal regular income tax (except when investing for "defensive" purposes). Interest from the Fund's investments may be subject to the federal alternative minimum tax for individuals and corporations (AMT). The Fund invests at least a majority of the Fund's assets in a portfolio of: (1) long-term, tax-exempt securities; and (2) medium-quality or noninvestment-grade, tax-exempt securities. Long-term, tax-exempt securities generally include tax-exempt securities with stated maturities of 10 years or more. The Fund also may invest in tax-exempt securities with stated maturities of less than 10 years. Investment-grade securities are securities that receive investment-grade ratings (i.e., generally ratings in the first, second, third or fourth highest rating category) by a nationally recognized statistical rating organization (NRSRO) or unrated securities of comparable quality. For example, securities rated AAA, AA, A or BBB by Standard & Poor's, an NRSRO, would be rated in the first, second, third or fourth ratings category, respectively. Securities rated below investment grade (or noninvestment-grade securities) are securities that do not receive investment grade ratings (i.e., generally ratings below one of the four highest rating categories) by an NRSRO or unrated securities of comparable quality. For example, securities rated B or BB by Standard & Poor's, an NRSRO, would be noninvestment-grade securities. Medium-quality securities generally include securities rated in the third or fourth highest rating category by an NRSRO and unrated securities of comparable quality. For example, tax-exempt securities rated A and BBB by Standard & Poor's, an NRSRO, are rated in the third (A) and fourth (BBB) highest rating categories, respectively. Under relevant SEC guidance, the Fund is permitted to invest in medium-quality and other investment-grade, tax-exempt securities to a greater degree than a high-yield bond fund that does not invest primarily in tax-exempt municipal securities. The Fund invests at least a majority of its assets in medium-quality or noninvestment-grade, tax-exempt securities in an attempt to pursue a higher level of current income than a tax-exempt bond fund that invests purely in investment-grade securities. Although medium-quality securities are still considered investment-grade securities, lower credit ratings do correspond to higher perceived credit risk. Medium-quality, tax-exempt securities generally are subject to interest rate, issuer credit, counterparty credit, liquidity, tax, leverage, call, sector, prepayment, credit enhancement, economic and non-diversification risks as described in this Prospectus. Noninvestment-grade securities, which are also known as junk bonds, also generally are subject to these same risks, as well as the risks of investing in noninvestment-grade securities as described in this Prospectus. The securities in which the Fund may principally invest include tax-exempt securities, which may include, for example, general obligation bonds, special revenue bonds, private activity bonds, tax-increment financing bonds, municipal leases, zero-coupon securities, inverse floaters, municipal mortgage-backed securities and planned amortization classes. Certain of the tax-exempt securities in which the Fund invests may be subject to credit enhancement. The Fund also may principally invest in derivative contracts (such as, for example, futures contracts, option contracts and swap contracts) and hybrid instruments to implement its investment strategies as more fully described in this Prospectus. Derivative contracts and hybrid instruments also may be subject to the risks of investing in derivative contracts and hybrid instruments as described in this Prospectus. The Fund also may invest in certain securities or other investments as described in this Prospectus (such as market discount bonds, credit default swaps and other derivative transactions) that will likely cause the Fund to realize a limited amount of ordinary income or short-term capital gains (which are treated as ordinary income for federal income tax purposes). The Fund invests its assets so that at least 80% of the income that it distributes will be exempt from federal regular income tax, except when investing for "defensive" purposes. This policy may not be changed without shareholder approval.
Risk [Heading]	rr_RiskHeading	What are the Main Risks of Investing in the Fund?
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	All mutual funds take investment risks. Therefore, it is possible to lose money by investing in the Fund. The primary factors that may reduce the Fund's returns include: Interest Rate Risk. Prices of fixed-income securities (including tax-exempt securities) generally fall when interest rates rise. Interest rate changes have a greater effect on prices of fixed-income securities with longer durations. Issuer Credit Risk. It is possible that interest or principal on securities will not be paid when due. Noninvestment-grade securities generally have a higher default risk than investment-grade securities. Such non-payment or default may reduce the value of the Fund's portfolio holdings, its share price and its performance. Counterparty Credit Risk. A party to a transaction involving the Fund may fail to meet its obligations. This could cause the Fund to lose money or to lose the benefit of the transaction or prevent the Fund from selling or buying other securities to implement its investment strategies. Liquidity Risk. Certain securities in which the Fund invests may be less readily marketable and may be subject to greater fluctuation in price than other securities. These features may make it more difficult to sell or buy a security at a favorable price or time. Noninvestment-grade securities generally have less liquidity than investment-grade securities. Liquidity risk also refers to the possibility that the Fund may not be able to sell a security or close out a derivative contract when it wants to. Over-the-counter derivative contracts generally carry greater liquidity risk than exchange-traded contracts. Tax Risk. In order to be tax-exempt, tax-exempt securities must meet certain legal requirements. Failure to meet such requirements may cause the interest received and distributed by the Fund to shareholders to be taxable. The federal income tax treatment of payments in respect of certain derivative contracts is unclear. The Fund also may invest in market discount bonds, enter into credit default swap arrangements and other derivative transactions, and engage in other permissible activities that will likely cause the Fund to realize a limited amount of ordinary income or short-term capital gains (which are treated as ordinary income for federal income tax purposes). Consequently, for each of these reasons, the Fund may receive payments, and make distributions, that are treated as ordinary income for federal income tax purposes. Income from the Fund also may be subject to AMT. Leverage Risk. Leverage risk is created when an investment, which includes, for example, a derivative contract, exposes the Fund to a level of risk that exceeds the amount invested. Changes in the value of such an investment magnify the Fund's risk of loss and potential for gain. Investments can have these same results if their returns are based on a multiple of a specified index, security or other benchmark. Call Risk. The Fund's performance may be adversely affected by the possibility that an issuer of a security held by the Fund may redeem the security prior to maturity at a price below or above its current market value. Sector Risk. A substantial part of the Fund's portfolio may be comprised of securities issued or credit enhanced by companies in similar businesses, or with other similar charateristics.  As a result, the Fund will be more susceptible to any economic, business, political or other developments which generally affect these entities. Prepayment Risk. When homeowners prepay their mortgages in response to lower interest rates, the Fund will be required to reinvest the proceeds at the lower interest rates available. Also, when interest rates fall, the price of municipal mortgage-backed securities may not rise to as great an extent as that of other fixed-income securities. Credit Enhancement Risk. The securities in which the Fund invests may be subject to credit enhancement (for example, guarantees, letters of credit or bond insurance). If the credit quality of the credit enhancement provider (for example, a bank or bond insurer) is downgraded, the rating on a security credit enhanced by such credit enhancement provider also may be downgraded. Having multiple securities credit enhanced by the same enhancement provider will increase the adverse effects on the Fund that are likely to result from a downgrading of, or a default by, such an enhancement provider. Adverse developments in the banking or bond insurance industries also may negatively affect the Fund. Non-Diversification Risk. The Fund is non-diversified. Compared to diversified mutual funds, it may invest a higher percentage of its assets among fewer issuers of portfolio securities. This increases the Fund's risk by magnifying the impact (positively or negatively) that any one issuer has on the Fund's Share price and performance. Risk Associated with Noninvestment-Grade Securities. The Fund may invest a portion of its assets in securities that are below investment-grade quality (which are also known as junk bonds), which may be subject to greater economic, credit and liquidity risks than investment-grade securities. Risk Related to the Economy. Lower-grade bond returns are sensitive to changes in the economy. The value of the Fund's portfolio may decline in tandem with a drop in the overall value of the stock market based on negative developments in the U.S. and global economies. Risk of Investing in Derivative Contracts and Hybrid Instruments. Derivative contracts and hybrid instruments involve risks different from, or possibly greater than, risks associated with investing directly in securities and other traditional investments. Specific risk issues related to the use of such contracts and instruments include valuation and tax issues, increased potential for losses and/or costs to the Fund, and a potential reduction in gains to the Fund. Each of these issues is described in greater detail in this Prospectus. Derivative contracts and hybrid instruments may also involve other risks described in this Prospectus or the Fund's Statement of Additional Information (SAI), such as interest rate, credit, liquidity and leverage risks. Technology Risk. The Adviser uses various technology in managing the Fund, consistent with its investment objective and strategy described in this Prospectus. For example, proprietary and third-party data and systems are utilized to support decision making for the Fund.  Data imprecision, software or other technology malfunctions, programming inaccuracies and similar circumstances may impair the performance of these systems, which may negatively affect Fund performance. The Shares offered by this Prospectus are not deposits or obligations of any bank, are not endorsed or guaranteed by any bank and are not insured or guaranteed by the U.S. government, the Federal Deposit Insurance Corporation, the Federal Reserve Board or any other government agency.
Risk Lose Money [Text]	rr_RiskLoseMoney	All mutual funds take investment risks. Therefore, it is possible to lose money by investing in the Fund.
Risk Nondiversified Status [Text]	rr_RiskNondiversifiedStatus	Non-Diversification Risk. The Fund is non-diversified. Compared to diversified mutual funds, it may invest a higher percentage of its assets among fewer issuers of portfolio securities. This increases the Fund's risk by magnifying the impact (positively or negatively) that any one issuer has on the Fund's Share price and performance.
Risk Not Insured Depository Institution [Text]	rr_RiskNotInsuredDepositoryInstitution	The Shares offered by this Prospectus are not deposits or obligations of any bank, are not endorsed or guaranteed by any bank and are not insured or guaranteed by the U.S. government, the Federal Deposit Insurance Corporation, the Federal Reserve Board or any other government agency.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance: Bar Chart and Table Risk/Return Bar Chart
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The Fund is a portfolio of Federated Municipal Securities Income Trust (the "Trust"), and is the successor to Federated Municipal High Yield Advantage Fund, Inc. ("Predecessor Fund") pursuant to a reorganization as of the close of business on November 10, 2006. Prior to the date of the reorganization, the Fund did not have any investment operations. Accordingly, the performance information and financial information, including information on fees and expenses, provided in this Prospectus for periods prior to the close of business on November 10, 2006, is historical information for the Predecessor Fund. On the date of the reorganization, November 10, 2006, the Predecessor Fund's assets (inclusive of liabilities recorded on the Predecessor Fund's records) were transferred into the Fund and the dissolution of the Predecessor Fund occurred within a short period of time after the date of the reorganization. As a result of the reorganization, the Fund does not have a different investment adviser than the Predecessor Fund, and the shareholders of A class, B class, C class and F class shares of the Predecessor Fund received A class, B class, C class or F class shares of the Fund, respectively. The bar chart and performance table below reflect historical performance data for the Fund and are intended to help you analyze the Fund's investment risks in light of its historical returns. The bar chart shows the variability of the Fund's F class total returns on a calendar year-by-year basis. The Average Annual Total Return Table shows returns averaged over the stated periods, and includes comparative performance information. The Fund's performance will fluctuate, and past performance (before and after taxes) is not necessarily an indication of future results. Updated performance information for the Fund is available under the "Products" section at FederatedInvestors.com or by calling 1-800-341-7400.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The bar chart shows the variability of the Fund's F class total returns on a calendar year-by-year basis.
Performance Availability Phone [Text]	rr_PerformanceAvailabilityPhone	1-800-341-7400
Performance Availability Website Address [Text]	rr_PerformanceAvailabilityWebSiteAddress	FederatedInvestors.com
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	The Fund's performance will fluctuate, and past performance (before and after taxes) is not necessarily an indication of future results.
Bar Chart [Heading]	rr_BarChartHeading	Federated Municipal High Yield Advantage Fund - F Class
Bar Chart Does Not Reflect Sales Loads [Text]	rr_BarChartDoesNotReflectSalesLoads	The total returns shown in the bar chart do not reflect the payment of any sales charges or recurring shareholder account fees. If these charges or fees had been included, the returns shown would have been lower.
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	The total returns shown in the bar chart do not reflect the payment of any sales charges or recurring shareholder account fees. If these charges or fees had been included, the returns shown would have been lower. The Fund's F class total return for the nine-month period from January 1, 2013 to September 30, 2013 was (7.29)%. Within the periods shown in the bar chart, the Fund's F class highest quarterly return was 14.61% (quarter ended September 30, 2009). Its lowest quarterly return was (16.00)% (quarter ended December 31, 2008).
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Return Table
Performance Table Uses Highest Federal Rate	rr_PerformanceTableUsesHighestFederalRate	After-tax returns are calculated using a standard set of assumptions. The stated returns assume the highest historical federal income and capital gains tax rates. The after-tax returns do not reflect the effect of any applicable state and local taxes.
Performance Table Not Relevant to Tax Deferred	rr_PerformanceTableNotRelevantToTaxDeferred	After-tax returns are not relevant to investors holding shares through a 401(k) plan, an Individual Retirement Account or other tax-advantaged investment plan.
Performance Table One Class of after Tax Shown [Text]	rr_PerformanceTableOneClassOfAfterTaxShown	After-tax returns are shown only for the F class and after-tax returns for A, B, C and IS classes will differ from those shown for F class.
Performance Table Narrative	rr_PerformanceTableNarrativeTextBlock	The Fun's IS Class commenced operations on June 11, 2013. For the period prior to commencement of operations of the IS class, the information shown below is for the Fund's F class. The performance of the Fund's F class shown in the performance table below has been adjusted to reflect the expenses of the Fund's IS class for each year for which the expenses of the Fund's IS class would have exceeded the actual expenses paid by the Fund's F class. The performance of the Fund's F class has also been adjusted to reflect differences in sales loads and charges imposed on the purchase and redemption of the Fund's IS class. In addition to Return Before Taxes, Return After Taxes is shown for the Fund's F class to illustrate the effect of federal taxes on Fund returns. After-tax returns are shown only for the F class and after-tax returns for A, B, C and IS classes will differ from those shown for F class. Actual after-tax returns depend on each investor's personal tax situation, and are likely to differ from those shown. After-tax returns are calculated using a standard set of assumptions. The stated returns assume the highest historical federal income and capital gains tax rates. The after-tax returns do not reflect the effect of any applicable state and local taxes. After-tax returns are not relevant to investors holding shares through a 401(k) plan, an Individual Retirement Account or other tax-advantaged investment plan. (For the Period Ended December 31, 2012)
Federated Municipal High Yield Advantage Fund | A
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	4.50%
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, as applicable)	rr_MaximumDeferredSalesChargeOverOther	none
Maximum Sales Charge (Load) Imposed on Reinvested Dividends (and other Distributions) (as a percentage of offering price)	rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther	none
Redemption Fee (as a percentage of amount redeemed, if applicable)	rr_RedemptionFeeOverRedemption	none
Exchange Fee	rr_ExchangeFeeOverRedemption	none
Management Fee	rr_ManagementFeesOverAssets	0.60%
Distribution (12b-1) Fee	rr_DistributionAndService12b1FeesOverAssets	none	[1]
Other Expenses	rr_OtherExpensesOverAssets	0.44%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.04%
Fee Waivers and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	0.15%	[2]
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements	rr_NetExpensesOverAssets	0.89%
Expense Breakpoint, Minimum Investment Required [Amount]	rr_ExpenseBreakpointMinimumInvestmentRequiredAmount	$ 100,000
1 Year	rr_ExpenseExampleYear01	551
3 Years	rr_ExpenseExampleYear03	766
5 Years	rr_ExpenseExampleYear05	998
10 Years	rr_ExpenseExampleYear10	1,664
1 Year	rr_ExpenseExampleNoRedemptionYear01	551
3 Years	rr_ExpenseExampleNoRedemptionYear03	766
5 Years	rr_ExpenseExampleNoRedemptionYear05	998
10 Years	rr_ExpenseExampleNoRedemptionYear10	1,664
1 Year	rr_AverageAnnualReturnYear01	8.35%
5 Years	rr_AverageAnnualReturnYear05	4.19%
10 Years	rr_AverageAnnualReturnYear10	4.57%
Federated Municipal High Yield Advantage Fund | B
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, as applicable)	rr_MaximumDeferredSalesChargeOverOther	5.50%
Maximum Sales Charge (Load) Imposed on Reinvested Dividends (and other Distributions) (as a percentage of offering price)	rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther	none
Redemption Fee (as a percentage of amount redeemed, if applicable)	rr_RedemptionFeeOverRedemption	none
Exchange Fee	rr_ExchangeFeeOverRedemption	none
Management Fee	rr_ManagementFeesOverAssets	0.60%
Distribution (12b-1) Fee	rr_DistributionAndService12b1FeesOverAssets	0.75%
Other Expenses	rr_OtherExpensesOverAssets	0.44%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.79%
Fee Waivers and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	0.15%	[2]
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.64%
1 Year	rr_ExpenseExampleYear01	732
3 Years	rr_ExpenseExampleYear03	963
5 Years	rr_ExpenseExampleYear05	1,170
10 Years	rr_ExpenseExampleYear10	1,908
1 Year	rr_ExpenseExampleNoRedemptionYear01	182
3 Years	rr_ExpenseExampleNoRedemptionYear03	563
5 Years	rr_ExpenseExampleNoRedemptionYear05	970
10 Years	rr_ExpenseExampleNoRedemptionYear10	1,908
1 Year	rr_AverageAnnualReturnYear01	6.93%
5 Years	rr_AverageAnnualReturnYear05	4.04%
10 Years	rr_AverageAnnualReturnYear10	4.41%
Federated Municipal High Yield Advantage Fund | C
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, as applicable)	rr_MaximumDeferredSalesChargeOverOther	1.00%
Maximum Sales Charge (Load) Imposed on Reinvested Dividends (and other Distributions) (as a percentage of offering price)	rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther	none
Redemption Fee (as a percentage of amount redeemed, if applicable)	rr_RedemptionFeeOverRedemption	none
Exchange Fee	rr_ExchangeFeeOverRedemption	none
Management Fee	rr_ManagementFeesOverAssets	0.60%
Distribution (12b-1) Fee	rr_DistributionAndService12b1FeesOverAssets	0.75%
Other Expenses	rr_OtherExpensesOverAssets	0.44%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.79%
Fee Waivers and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	0.15%	[2]
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.64%
1 Year	rr_ExpenseExampleYear01	282
3 Years	rr_ExpenseExampleYear03	563
5 Years	rr_ExpenseExampleYear05	970
10 Years	rr_ExpenseExampleYear10	2,105
1 Year	rr_ExpenseExampleNoRedemptionYear01	182
3 Years	rr_ExpenseExampleNoRedemptionYear03	563
5 Years	rr_ExpenseExampleNoRedemptionYear05	970
10 Years	rr_ExpenseExampleNoRedemptionYear10	2,105
1 Year	rr_AverageAnnualReturnYear01	11.42%
5 Years	rr_AverageAnnualReturnYear05	4.35%
10 Years	rr_AverageAnnualReturnYear10	4.25%
Federated Municipal High Yield Advantage Fund | F
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	1.00%
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, as applicable)	rr_MaximumDeferredSalesChargeOverOther	1.00%
Maximum Sales Charge (Load) Imposed on Reinvested Dividends (and other Distributions) (as a percentage of offering price)	rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther	none
Redemption Fee (as a percentage of amount redeemed, if applicable)	rr_RedemptionFeeOverRedemption	none
Exchange Fee	rr_ExchangeFeeOverRedemption	none
Management Fee	rr_ManagementFeesOverAssets	0.60%
Distribution (12b-1) Fee	rr_DistributionAndService12b1FeesOverAssets	none	[1]
Other Expenses	rr_OtherExpensesOverAssets	0.44%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.04%
Fee Waivers and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	0.15%	[2]
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements	rr_NetExpensesOverAssets	0.89%
Expense Breakpoint, Minimum Investment Required [Amount]	rr_ExpenseBreakpointMinimumInvestmentRequiredAmount	1,000,000
1 Year	rr_ExpenseExampleYear01	305
3 Years	rr_ExpenseExampleYear03	528
5 Years	rr_ExpenseExampleYear05	668
10 Years	rr_ExpenseExampleYear10	1,358
1 Year	rr_ExpenseExampleNoRedemptionYear01	205
3 Years	rr_ExpenseExampleNoRedemptionYear03	428
5 Years	rr_ExpenseExampleNoRedemptionYear05	668
10 Years	rr_ExpenseExampleNoRedemptionYear10	1,358
2003	rr_AnnualReturn2003	7.57%
2004	rr_AnnualReturn2004	6.73%
2005	rr_AnnualReturn2005	6.22%
2006	rr_AnnualReturn2006	7.05%
2007	rr_AnnualReturn2007	(2.51%)
2008	rr_AnnualReturn2008	(23.57%)
2009	rr_AnnualReturn2009	29.11%
2010	rr_AnnualReturn2010	3.47%
2011	rr_AnnualReturn2011	11.02%
2012	rr_AnnualReturn2012	13.28%
Year to Date Return, Label	rr_YearToDateReturnLabel	The Fund's F class total return for the nine-month period
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Sep. 30, 2013
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	(7.29%)
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest quarterly return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Sep. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	14.61%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest quarterly return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(16.00%)
1 Year	rr_AverageAnnualReturnYear01	11.21%
5 Years	rr_AverageAnnualReturnYear05	4.93%
10 Years	rr_AverageAnnualReturnYear10	4.93%
Federated Municipal High Yield Advantage Fund | IS
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, as applicable)	rr_MaximumDeferredSalesChargeOverOther	none
Maximum Sales Charge (Load) Imposed on Reinvested Dividends (and other Distributions) (as a percentage of offering price)	rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther	none
Redemption Fee (as a percentage of amount redeemed, if applicable)	rr_RedemptionFeeOverRedemption	none
Exchange Fee	rr_ExchangeFeeOverRedemption	none
Management Fee	rr_ManagementFeesOverAssets	0.60%
Distribution (12b-1) Fee	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.24%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.84%
Fee Waivers and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	0.20%	[2]
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements	rr_NetExpensesOverAssets	0.64%
1 Year	rr_ExpenseExampleYear01	86
3 Years	rr_ExpenseExampleYear03	268
5 Years	rr_ExpenseExampleYear05	466
10 Years	rr_ExpenseExampleYear10	1,037
1 Year	rr_ExpenseExampleNoRedemptionYear01	86
3 Years	rr_ExpenseExampleNoRedemptionYear03	268
5 Years	rr_ExpenseExampleNoRedemptionYear05	466
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 1,037
1 Year	rr_AverageAnnualReturnYear01	13.28%
5 Years	rr_AverageAnnualReturnYear05	5.05%
10 Years	rr_AverageAnnualReturnYear10	4.97%
Federated Municipal High Yield Advantage Fund | Return After Taxes on Distributions | F
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	11.21%
5 Years	rr_AverageAnnualReturnYear05	4.93%
10 Years	rr_AverageAnnualReturnYear10	4.93%
Federated Municipal High Yield Advantage Fund | Return after Taxes on Distributions and Sale of Fund Shares | F
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	9.02%
5 Years	rr_AverageAnnualReturnYear05	4.96%
10 Years	rr_AverageAnnualReturnYear10	4.98%
Federated Municipal High Yield Advantage Fund | S&P Municipal Bond Index (reflects no deduction for fees, expenses or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	7.41%	[3]
5 Years	rr_AverageAnnualReturnYear05	5.78%	[3]
10 Years	rr_AverageAnnualReturnYear10	5.19%	[3]
Federated Municipal High Yield Advantage Fund | S&P 25% A and Higher/25% BBB/50% High Yield, All 3-Year Plus Sub-Index (reflects no deduction for fees, expenses or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	12.80%	[4]
5 Years	rr_AverageAnnualReturnYear05	6.00%	[4]
10 Years	rr_AverageAnnualReturnYear10	6.28%	[4]
Federated Municipal High Yield Advantage Fund | Morningstar High Yield Municipal Funds Category Average
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	13.77%	[5]
5 Years	rr_AverageAnnualReturnYear05	4.97%	[5]
10 Years	rr_AverageAnnualReturnYear10	4.87%	[5]

[1] The Fund has adopted a Distribution (12b-1) Plan for its Class A shares and Class F shares pursuant to which the A class and F class of the Fund may incur or charge a Distribution (12b-1) fee of up to a maximum amount of 0.05%. No such fee is currently incurred or charged by the A class or the F class of the Fund. The A class and F class of the Fund will not incur or charge such a Distribution (12b-1) fee until such time as approved by the Fund's Board of Trustees (the "Trustees").

[2] The Adviser and its affiliates have voluntarily agreed to waive their fees and/or reimburse expenses so that the total annual fund operating expenses (excluding Acquired Fund Fees and Expenses, extraordinary expenses and proxy-related expenses paid by the Fund, if any) paid by the Fund's A, B, C ,F and IS classes (after the voluntary waivers and/or reimbursements) will not exceed 0.89%, 1.64%, 1.64%, 0.89% and 0.64% (the "Fee Limit"), respectively, up to but not including the later of (the "Termination Date"): (a) November 1, 2014; or (b) the date of the Fund's next effective Prospectus. While the Adviser and its affiliates currently do not anticipate terminating or increasing these arrangements prior to the Termination Date, these arrangements may only be terminated or the Fee Limit increased prior to the Termination Date with the agreement of the Trustees.

[3] The S&P Municipal Bond Index (Main Index) is a broad, comprehensive, market value-weighted index composed of approximately 55,000 bond issues that are exempt from U.S. federal income taxes or subject to the alternative minimum tax (AMT). Eligibility criteria for inclusion in the Main Index include, but are not limited to: the bond issuer must be a state (including the Commonwealth of Puerto Rico and U.S. territories) or local government or a state or local government entity where interest on the bond is exempt from U.S. federal income taxes or subject to the AMT; the bond must be held by a mutual fund for which Standard & Poor's Securities Evaluations, Inc. provides prices; it must be denominated in U.S. dollars and have a minimum par amount of $2 million; and the bond must have a minimum term to maturity and/or call date greater than or equal to one calendar month. The Main Index is rebalanced monthly.

[4] The S&P 25% A and Higher/25% BBB/50% High Yield, All 3-Year Plus Sub-Index is a custom blended index that represents, by market weighting, 25% of the A-rated and higher component of the Main Index, 25% of the BBB-rated component of the Main Index and 50% of the below investment-grade (bonds with ratings of less than BBB-/Baa3) component of the Main Index, all with remaining maturities of three years or more.

[5] Morningstar figures represent the average of the total returns reported by all the mutual funds designated by Morningstar as falling into the respective category indicated. Funds designated within the Morningstar High Yield Municipal Funds Category Average include those that invest at least 50% of assets in high-income municipal securities that are not rated or that are rated by a major agency such as Standard & Poor's or Moody's Investor Service at the level of BBB (considered part of the high-yield universe within the municipal industry) and below.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	Federated Municipal Securities Income Trust
Prospectus Date	rr_ProspectusDate	Oct. 31, 2013
Document Creation Date	dei_DocumentCreationDate	Oct. 28, 2013

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	Federated Municipal Securities Income Trust
Prospectus Date	rr_ProspectusDate	Oct. 31, 2013
Federated Ohio Municipal Income Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Federated Ohio Municipal Income Fund (the "Fund")
Objective [Heading]	rr_ObjectiveHeading	RISK/RETURN SUMMARY: INVESTMENT OBJECTIVE
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund's investment objective is to provide current income exempt from federal regular income tax (federal regular income tax does not include the federal alternative minimum tax (AMT)) and the personal income taxes imposed by the state of Ohio and Ohio municipalities.
Expense [Heading]	rr_ExpenseHeading	RISK/RETURN SUMMARY: FEES AND EXPENSES
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay if you buy and hold Class A Shares (A) and Class F Shares (F) of the Fund. You may qualify for certain sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 and $1,000,000 in certain classes (e.g., A class and F class, respectively) of Federated funds. More information about these and other discounts is available from your financial professional and in the "What Do Shares Cost?" section of the Prospectus on page 14.
Shareholder Fees Caption [Text]	rr_ShareholderFeesCaption	Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	November 1, 2014
Fee Waiver Or Reimbursement Over Assets Later Of Termination Or Next Effective Prosepectus	fmsit1_FeeWaiverOrReimbursementOverAssetsLaterOfTerminationOrNextEffectiveProsepectus	up to but not including the later of (the “Termination Date”): (a) November 1, 2014; or (b) the date of the Fund’s next effective Prospectus.
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	Portfolio Turnover
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was 15% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	15.00%
Expense Breakpoint Discounts [Text]	rr_ExpenseBreakpointDiscounts	You may qualify for certain sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 and $1,000,000 in certain classes (e.g., A class and F class, respectively) of Federated funds.
Expense Example [Heading]	rr_ExpenseExampleHeading	Example
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 for the time periods indicated and then redeem all of your Shares at the end of those periods. Expenses assuming no redemption are also shown. The Example also assumes that your investment has a 5% return each year and that operating expenses are as shown in the table above and remain the same. Although your actual costs and returns may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading]	rr_StrategyHeading	RISK/RETURN SUMMARY: INVESTMENTS, RISKS and PERFORMANCE What are the Fund's Main Investment Strategies?
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	The Fund pursues its objective by investing its assets so that, normally (except as discussed herein), distributions of annual interest income are exempt from federal regular income tax and the personal income taxes imposed by the state of Ohio and Ohio municipalities. Interest from the Fund’s investments may be subject to the federal AMT for individuals and corporations. The Fund does not limit itself to securities of a particular maturity range. Currently, at least a majority of the Fund’s assets will be invested in long-term securities (i.e., securities with stated maturities of 10 years or more). The Fund also will invest at least a majority of its assets in securities rated investment-grade (or unrated securities of comparable quality) and may purchase securities rated below investment-grade (or unrated securities of comparable quality), which are also known as junk bonds, up to 49% of its assets. Investment-grade securities are securities that receive investment-grade ratings (i.e., generally ratings in the first, second, third or fourth highest rating category) by a nationally recognized statistical rating organization (NRSRO) or unrated securities of comparable quality. For example, securities rated AAA, AA, A or BBB by Standard & Poor’s, an NRSRO,would be rated in the first, second, third or fourth ratings category, respectively. Securities rated below investment-grade (or noninvestment-grade securities) are securities that do not receive investment-grade ratings (i.e., generally ratings below one of the four highest rating categories) by an NRSRO or unrated securities of comparable quality. For example, securities rated B or BB by Standard & Poor’s, an NRSRO, would be noninvestment-grade securities. The Fund does not have a specific minimum quality rating. The securities in which the Fund may principally invest include tax-exempt securities, which may include, for example, general obligation bonds, special revenue bonds, private activity bonds, tax-increment financing bonds, municipal leases, zero-coupon securities, inverse floaters, municipal mortgage-backed securities and planned amortization classes. Certain of the tax-exempt securities in which the Fund invests may be subject to credit enhancement. The Fund also may principally invest in derivative contracts (such as, for example, futures contracts, option contracts and swap contracts) and hybrid instruments to implement its investment strategies as more fully described in this Prospectus. The Fund also may invest in certain securities or other investments as described in this Prospectus (such as market discount bonds, credit default swaps and other derivative transactions) that will likely cause the Fund to realize a limited amount of ordinary income or short-term capital gains (which are treated as ordinary income for federal income tax purposes). Because the Fund refers to Ohio municipal investments in its name, it has an investment policy that it will normally invest its assets so that at least 80% of the income that it distributes will be exempt from federal regular income tax and the personal income taxes imposed by the state of Ohio and Ohio municipalities. This policy may not be changed without shareholder approval.
Risk [Heading]	rr_RiskHeading	What are the Main Risks of Investing in the Fund?
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	All mutual funds take investment risks. Therefore, it is possible to lose money by investing in the Fund. The primary factors that may reduce the Fund’s returns include: Interest Rate Risk. Prices of fixed-income securities (including tax-exempt securities) generally fall when interest rates rise. Interest rate changes have a greater effect on prices of fixed-income securities with longer durations. Issuer Credit Risk. It is possible that interest or principal on securities will not be paid when due. Noninvestment-grade securities generally have a higher default risk than investment-grade securities. Such non-payment or default may reduce the value of the Fund’s portfolio holdings, its share price and its performance. Counterparty Credit Risk. A party to a transaction involving the Fund may fail to meet its obligations. This could cause the Fund to lose money or to lose the benefit of the transaction or prevent the Fund from selling or buying other securities to implement its investment strategies. Liquidity Risk. Certain securities in which the Fund invests may be less readily marketable and may be subject to greater fluctuation in price than other securities. These features may make it more difficult to sell or buy a security at a favorable price or time. Noninvestment-grade securities generally have less liquidity than investment-grade securities. Liquidity risk also refers to the possibility that the Fund may not be able to sell a security or close out a derivative contract when it wants to. Over-the-counter derivative contracts generally carry greater liquidity risk than exchange-traded contracts. Tax Risk. In order to be tax-exempt, tax-exempt securities must meet certain legal requirements. Failure to meet such requirements may cause the interest received and distributed by the Fund to shareholders to be taxable. The federal income tax treatment of payments in respect of certain derivative contracts is unclear. The Fund also may invest in market discount bonds, enter into credit default swap arrangements and other derivative transactions, and engage in other permissible activities that will likely cause the Fund to realize a limited amount of ordinary income or short-term capital gains (which are treated as ordinary income for federal income tax purposes). Consequently, for each of these reasons, the Fund may receive payments, and make distributions, that are treated as ordinary income for federal income tax purposes. Income from the Fund also may be subject to AMT. Leverage Risk. Leverage risk is created when an investment, which includes, for example, a derivative contract, exposes the Fund to a level of risk that exceeds the amount invested. Changes in the value of such an investment magnify the Fund’s risk of loss and potential for gain. Investments can have these same results if their returns are based on a multiple of a specified index, security or other benchmark. Call Risk. The Fund’s performance may be adversely affected by the possibility that an issuer of a security held by the Fund may redeem the security prior to maturity at a price below or above its current market value. Sector Risk. Since the Fund invests at least a majority of its assets in a portfolio of: (1) long-term, Ohio tax-exempt securities; and (2) investment-grade, Ohio tax-exempt securities, the Fund may be subject to additional risks compared to funds that invest in multiple states. Ohio’s economy is  relatively diversified across the manufacturing, agriculture and service sectors. However, the manufacturing sector is the dominant sector within Ohio and exposes the state to the economic dislocations which occur within cyclical industries. A substantial part of the Fund’s portfolio may be comprised of securities issued or credit enhanced by companies in similar businesses or with other similar characteristics. As a result, the Fund will be more susceptible to any economic, business, political or other developments which generally affect these issuers or entities. Prepayment Risk. When homeowners prepay their mortgages in response to lower interest rates, the Fund will be required to reinvest the proceeds at the lower interest rates available. Also, when interest rates fall, the price of municipal mortgage-backed securities may not rise to as great an extent as that of other fixed-income securities. Credit Enhancement Risk. The securities in which the Fund invests may be subject to credit enhancement (for example, guarantees, letters of credit or bond insurance). If the credit quality of the credit enhancement provider (for example, a bank or bond insurer) is downgraded, the rating on a security credit enhanced by such credit enhancement provider also may be downgraded. Having multiple securities credit enhanced by the same enhancement provider will increase the adverse effects on the Fund that are likely to result from a downgrading of, or a default by, such an enhancement provider. Adverse developments in the banking or bond insurance industries also may negatively affect the Fund. Non-Diversification Risk. The Fund is non-diversified. Compared to diversified mutual funds, it may invest a higher percentage of its assets among fewer issuers of portfolio securities. This increases the Fund’s risk by magnifying the impact (positively or negatively) that any one issuer has on the Fund’s Share price and performance. Risk Associated with Noninvestment-Grade Securities. The Fund may invest a portion of its assets in securities that are below investment-grade quality (which are also known as junk bonds), which may be subject to greater economic, credit and liquidity risks than investment-grade securities. Risk Related to the Economy. Lower-grade bond returns are sensitive to changes in the economy. The value of the Fund’s portfolio may decline in tandem with a drop in the overall value of the stock market based on negative developments in the U.S. and global economies. Risk of Investing in Derivative Contracts and Hybrid Instruments. Derivative contracts and hybrid instruments involve risks different from, or possibly greater than, risks associated with investing directly in securities and other traditional investments. Specific risk issues related to the use of such contracts and instruments include valuation and tax issues, increased potential for losses and/or costs to the Fund, and a potential reduction in gains to the Fund. Each of these issues is described in greater detail in this Prospectus. Derivative contracts and hybrid instruments may also involve other risks described in this Prospectus or the Fund’s Statement of Additional Information (SAI), such as interest rate, credit, liquidity and leverage risks. Technology Risk. The Adviser uses various technology in managing the Fund, consistent with its investment objective and strategy described in this Prospectus. For example, proprietary and third-party data and systems are utilized to support decision making for the Fund.  Data imprecision, software or other technology malfunctions, programming inaccuracies and similar circumstances may impair the performance of these systems, which may negatively affect Fund performance. The Shares offered by this Prospectus are not deposits or obligations of any bank, are not endorsed or guaranteed by any bank and are not insured or guaranteed by the U.S. government, the Federal Deposit Insurance Corporation, the Federal Reserve Board or any other government agency.
Risk Lose Money [Text]	rr_RiskLoseMoney	All mutual funds take investment risks. Therefore, it is possible to lose money by investing in the Fund.
Risk Nondiversified Status [Text]	rr_RiskNondiversifiedStatus	Non-Diversification Risk. The Fund is non-diversified. Compared to diversified mutual funds, it may invest a higher percentage of its assets among fewer issuers of portfolio securities. This increases the Fund’s risk by magnifying the impact (positively or negatively) that any one issuer has on the Fund’s Share price and performance.
Risk Not Insured Depository Institution [Text]	rr_RiskNotInsuredDepositoryInstitution	The Shares offered by this Prospectus are not deposits or obligations of any bank, are not endorsed or guaranteed by any bank and are not insured or guaranteed by the U.S. government, the Federal Deposit Insurance Corporation, the Federal Reserve Board or any other government agency.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance: Bar Chart and Table Risk/Return Bar Chart
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The bar chart and performance table below reflect historical performance data for the Fund and are intended to help you analyze the Fund's investment risks in light of its historical returns. The bar chart shows the variability of the Fund's F class total returns on a calendar year-by-year basis. The Average Annual Total Return Table shows returns averaged over the stated periods, and includes comparative performance information. The Fund's performance will fluctuate, and past performance (before and after taxes) is not necessarily an indication of future results. Updated performance information for the Fund is available under the "Products" section at FederatedInvestors.com or by calling 1-800-341-7400.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The bar chart shows the variability of the Fund's F class total returns on a calendar year-by-year basis.
Performance Availability Phone [Text]	rr_PerformanceAvailabilityPhone	1-800-341-7400
Performance Availability Website Address [Text]	rr_PerformanceAvailabilityWebSiteAddress	FederatedInvestors.com
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	The Fund's performance will fluctuate, and past performance (before and after taxes) is not necessarily an indication of future results.
Bar Chart [Heading]	rr_BarChartHeading	Federated Ohio Municipal Income Fund - F Class
Bar Chart Does Not Reflect Sales Loads [Text]	rr_BarChartDoesNotReflectSalesLoads	The total returns shown in the bar chart do not reflect the payment of any sales charges or recurring shareholder account fees. If these charges or fees had been included, the returns shown would have been lower.
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	The total returns shown in the bar chart do not reflect the payment of any sales charges or recurring shareholder account fees. If these charges or fees had been included, the returns shown would have been lower. The Fund's F class total return for the nine-month period from January 1, 2013 to September 30, 2013, was (3.05)%. Within the periods shown in the bar chart, the Fund's F class highest quarterly return was 5.48% (quarter ended September 30, 2009). Its lowest quarterly return was (4.13)% (quarter ended September 30, 2008).
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Return Table
Performance Table Uses Highest Federal Rate	rr_PerformanceTableUsesHighestFederalRate	After-tax returns are calculated using a standard set of assumptions. The stated returns assume the highest historical federal income and capital gains tax rates. These after-tax returns do not reflect the effect of any applicable state and local taxes.
Performance Table Not Relevant to Tax Deferred	rr_PerformanceTableNotRelevantToTaxDeferred	After-tax returns are not relevant to investors holding Shares through tax-deferred programs, such as a 401(k) Plan an Individual Retirement Account (IRA) or other tax-advantaged investment plan.
Performance Table One Class of after Tax Shown [Text]	rr_PerformanceTableOneClassOfAfterTaxShown	After-tax returns are shown only for the F class and after tax returns for the A class will differ from those shown below for the F class.
Performance Table Narrative	rr_PerformanceTableNarrativeTextBlock	The Fund's A class commenced operation on November 18, 2008. Accordingly, for the period prior to the commencement of operations, the performance information shown in the Average Annual Total Return table is for the Fund's F class adjusted to reflect the sales charges and expenses of the A class. In addition to Return Before Taxes, Return After Taxes is shown for the Fund's F class to illustrate the effect of federal taxes on Fund returns. After-tax returns are shown only for the F class and after tax returns for the A class will differ from those shown below for the F class. Actual after-tax returns depend on each investor's personal tax situation and are likely to differ from those shown. After-tax returns are calculated using a standard set of assumptions. The stated returns assume the highest historical federal income and capital gains tax rates. These after-tax returns do not reflect the effect of any applicable state and local taxes. After-tax returns are not relevant to investors holding Shares through tax-deferred programs, such as a 401(k) Plan an Individual Retirement Account (IRA) or other tax-advantaged investment plan. (For the Periods Ended December 31, 2012)
Federated Ohio Municipal Income Fund | A
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	4.50%
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, as applicable)	rr_MaximumDeferredSalesChargeOverOther	none
Maximum Sales Charge (Load) Imposed on Reinvested Dividends (and other Distributions) (as a percentage of offering price)	rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther	none
Redemption Fee (as a percentage of amount redeemed, if applicable)	rr_RedemptionFeeOverRedemption	none
Exchange Fee	rr_ExchangeFeeOverRedemption	none
Management Fee	rr_ManagementFeesOverAssets	0.40%
Distribution (12b-1) Fee	rr_DistributionAndService12b1FeesOverAssets	none	[1]
Other Expenses	rr_OtherExpensesOverAssets	0.49%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.89%
Fee Waivers and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	0.14%	[2]
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements	rr_NetExpensesOverAssets	0.75%
Expense Breakpoint, Minimum Investment Required [Amount]	rr_ExpenseBreakpointMinimumInvestmentRequiredAmount	$ 100,000
1 Year	rr_ExpenseExampleYear01	537
3 Years	rr_ExpenseExampleYear03	721
5 Years	rr_ExpenseExampleYear05	921
10 Years	rr_ExpenseExampleYear10	1,497
1 Year	rr_ExpenseExampleNoRedemptionYear01	537
3 Years	rr_ExpenseExampleNoRedemptionYear03	721
5 Years	rr_ExpenseExampleNoRedemptionYear05	921
10 Years	rr_ExpenseExampleNoRedemptionYear10	1,497
1 Year	rr_AverageAnnualReturnYear01	2.19%
5 Years	rr_AverageAnnualReturnYear05	3.43%
10 Years	rr_AverageAnnualReturnYear10	3.45%
Federated Ohio Municipal Income Fund | F
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	1.00%
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, as applicable)	rr_MaximumDeferredSalesChargeOverOther	1.00%
Maximum Sales Charge (Load) Imposed on Reinvested Dividends (and other Distributions) (as a percentage of offering price)	rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther	none
Redemption Fee (as a percentage of amount redeemed, if applicable)	rr_RedemptionFeeOverRedemption	none
Exchange Fee	rr_ExchangeFeeOverRedemption	none
Management Fee	rr_ManagementFeesOverAssets	0.40%
Distribution (12b-1) Fee	rr_DistributionAndService12b1FeesOverAssets	0.40%
Other Expenses	rr_OtherExpensesOverAssets	0.49%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.29%
Fee Waivers and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	0.39%	[2]
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements	rr_NetExpensesOverAssets	0.90%
Expense Breakpoint, Minimum Investment Required [Amount]	rr_ExpenseBreakpointMinimumInvestmentRequiredAmount	1,000,000
1 Year	rr_ExpenseExampleYear01	230
3 Years	rr_ExpenseExampleYear03	505
5 Years	rr_ExpenseExampleYear05	800
10 Years	rr_ExpenseExampleYear10	1,641
1 Year	rr_ExpenseExampleNoRedemptionYear01	130
3 Years	rr_ExpenseExampleNoRedemptionYear03	405
5 Years	rr_ExpenseExampleNoRedemptionYear05	700
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 1,541
2003	rr_AnnualReturn2003	5.49%
2004	rr_AnnualReturn2004	4.47%
2005	rr_AnnualReturn2005	3.16%
2006	rr_AnnualReturn2006	4.65%
2007	rr_AnnualReturn2007	1.16%
2008	rr_AnnualReturn2008	(6.32%)
2009	rr_AnnualReturn2009	11.51%
2010	rr_AnnualReturn2010	1.48%
2011	rr_AnnualReturn2011	9.10%
2012	rr_AnnualReturn2012	6.81%
Year to Date Return, Label	rr_YearToDateReturnLabel	The Fund's F class total return for the nine-month period
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Sep. 30, 2013
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	(3.05%)
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest quarterly return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Sep. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	5.48%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest quarterly return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Sep. 30, 2008
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(4.13%)
1 Year	rr_AverageAnnualReturnYear01	4.78%
5 Years	rr_AverageAnnualReturnYear05	4.12%
10 Years	rr_AverageAnnualReturnYear10	3.94%
Federated Ohio Municipal Income Fund | Return After Taxes on Distributions | F
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	4.78%
5 Years	rr_AverageAnnualReturnYear05	4.12%
10 Years	rr_AverageAnnualReturnYear10	3.94%
Federated Ohio Municipal Income Fund | Return After Taxes on Distributions and Sale of Fund Shares | F
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	4.24%
5 Years	rr_AverageAnnualReturnYear05	4.04%
10 Years	rr_AverageAnnualReturnYear10	3.94%
Federated Ohio Municipal Income Fund | S&P Municipal Bond Ohio Index (reflects no deduction for fees, expenses or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	10.23%	[3]
5 Years	rr_AverageAnnualReturnYear05	5.60%	[3]
10 Years	rr_AverageAnnualReturnYear10	8.99%	[3]
Federated Ohio Municipal Income Fund | S&P Municipal Bond OH, Investment Grade, 3-Year Plus with Tobacco 2% Constrained Sub-Index (reflects no deduction for fees, expenses or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	8.51%	[4]
5 Years	rr_AverageAnnualReturnYear05	5.74%	[4]
10 Years	rr_AverageAnnualReturnYear10	5.15%	[4]
Federated Ohio Municipal Income Fund | Morningstar Municipal Ohio Funds Category Average
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	6.78%	[5]
5 Years	rr_AverageAnnualReturnYear05	4.72%	[5]
10 Years	rr_AverageAnnualReturnYear10	3.93%	[5]

[1] The Fund has adopted a Distribution (12b-1) Plan for its Class A Shares pursuant to which the A class of the Fund may incur or charge a Distribution (12b-1) fee of up to a maximum amount of 0.05%. No such fee is currently incurred or charged by the A class of the Fund. The A class of the Fund will not incur or charge such a Distribution (12b-1) fee until such time as approved by the Fund's Board of Trustees (the "Trustees").

[2] The Adviser and its affiliates have voluntarily agreed to waive their fees and/or reimburse expenses so that the total annual fund operating expenses (excluding Acquired Fund Fees and Expenses, extraordinary expenses, and proxy-related expenses paid by the Fund, if any) paid by the Fund's A class and F class (after the voluntary waivers and/or reimbursements) will not exceed 0.75% and 0.90% (the "Fee Limit"), respectively, up to but not including the later of (the "Termination Date"): (a) November 1, 2014; or (b) the date of the Fund's next effective Prospectus. While the Adviser and its affiliates currently do not anticipate terminating or increasing these arrangements prior to the Termination Date, these arrangements may only be terminated or the Fee Limit increased prior to the Termination Date with the agreement of the Trustees.

[3] The S&P Municipal Bond Ohio Index (OH Index) consists of bonds in the S&P Municipal Bond Index (Main Index) that have been issued by the state of Ohio or local governments or state or local government entities within Ohio. The Main Index is a broad, comprehensive, market value-weighted index composed of approximately 55,000 bond issues that are exempt from U.S. federal income taxes or subject to the alternative minimum tax (AMT). Eligibility criteria for inclusion in the Main Index include, but are not limited to: the bond issuer must be a state (including the Commonwealth of Puerto Rico and U.S. territories) or local government or a state or local government entity where interest on the bond is exempt from U.S. federal income taxes or subject to the AMT; the bond must be held by a mutual fund for which Standard & Poor's Securities Evaluations, Inc. provides prices; it must be denominated in U.S. dollars and have a minimum par amount of $2 million; and the bond must have a minimum term to maturity and/or call date greater than or equal to one calendar month. The Main Index is rebalanced monthly.

[4] The S&P Municipal Bond OH Investment Grade, 3-Year Plus with Tobacco 2% Constrained Sub-Index (OHIG Index) represents the portion of the OH Index composed solely of bonds that are rated BBB-/Baa3 or higher with remaining maturities of more than three years while limiting tobacco bonds to 2%, by market weighting, of the sub-index.

[5] Morningstar figures represent the average of the total returns reported by all the mutual funds designated by Morningstar as falling into the respective category indicated. Funds designated within the Morningstar Municipal Ohio Funds Category Average (MSTARMOH) include those that invest at least 80% of assets in Ohio municipal debt and can include long-, intermediate- and short-duration portfolios.

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Federated Municipal High Yield Advantage Fund

Federated Municipal High Yield Advantage Fund (the "Fund")

RISK/RETURN SUMMARY: INVESTMENT OBJECTIVE

The Fund's investment objective is to provide a high level of current income which is generally exempt from the federal regular income tax.

RISK/RETURN SUMMARY: FEES AND EXPENSES

This table describes the fees and expenses that you may pay if you buy and hold the Fund's Class A Shares (A), Class B Shares (B), Class C Shares (C), Class F Shares (F) and Institutional Shares (IS). You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future at least $100,000 or $1,000,000 in certain classes (e.g., A class and F class, respectively) of Federated funds. More information about these and other discounts is available from your financial professional and in the "What Do Shares Cost?" section of the Prospectus on page 16.

Shareholder Fees (fees paid directly from your investment)

Shareholder Fees Federated Municipal High Yield Advantage Fund	A	B	C	F	IS
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	4.50%	none	none	1.00%	none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, as applicable)	none	5.50%	1.00%	1.00%	none
Maximum Sales Charge (Load) Imposed on Reinvested Dividends (and other Distributions) (as a percentage of offering price)	none	none	none	none	none
Redemption Fee (as a percentage of amount redeemed, if applicable)	none	none	none	none	none
Exchange Fee	none	none	none	none	none

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses Federated Municipal High Yield Advantage Fund		A		B	C	F		IS
Management Fee		0.60%		0.60%	0.60%	0.60%		0.60%
Distribution (12b-1) Fee		none	[1]	0.75%	0.75%	none	[1]	none
Other Expenses		0.44%		0.44%	0.44%	0.44%		0.24%
Total Annual Fund Operating Expenses		1.04%		1.79%	1.79%	1.04%		0.84%
Fee Waivers and/or Expense Reimbursements	[2]	0.15%		0.15%	0.15%	0.15%		0.20%
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements		0.89%		1.64%	1.64%	0.89%		0.64%

Example

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 for the time periods indicated and then redeem all of your Shares at the end of those periods. Expenses assuming no redemption are also shown. The Example also assumes that your investment has a 5% return each year and that operating expenses are as shown in the table above and remain the same. Although your actual costs and returns may be higher or lower, based on these assumptions your costs would be:

Expense Example Federated Municipal High Yield Advantage Fund (USD $)	1 Year	3 Years	5 Years	10 Years
A	551	766	998	1,664
B	732	963	1,170	1,908
C	282	563	970	2,105
F	305	528	668	1,358
IS	86	268	466	1,037

Expense Example, No Redemption Federated Municipal High Yield Advantage Fund (USD $)	1 Year	3 Years	5 Years	10 Years
A	551	766	998	1,664
B	182	563	970	1,908
C	182	563	970	2,105
F	205	428	668	1,358
IS	86	268	466	1,037

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was 17% of the average value of its portfolio.

RISK/RETURN SUMMARY: INVESTMENTS, RISKS and PERFORMANCE

What are the Fund's Main Investment Strategies?

The Fund pursues its objective by investing its assets so that, normally (except as discussed herein), distributions of annual interest income are exempt from federal regular income tax (except when investing for "defensive" purposes). Interest from the Fund's investments may be subject to the federal alternative minimum tax for individuals and corporations (AMT). The Fund invests at least a majority of the Fund's assets in a portfolio of: (1) long-term, tax-exempt securities; and (2) medium-quality or noninvestment-grade, tax-exempt securities. Long-term, tax-exempt securities generally include tax-exempt securities with stated maturities of 10 years or more. The Fund also may invest in tax-exempt securities with stated maturities of less than 10 years. Investment-grade securities are securities that receive investment-grade ratings (i.e., generally ratings in the first, second, third or fourth highest rating category) by a nationally recognized statistical rating organization (NRSRO) or unrated securities of comparable quality. For example, securities rated AAA, AA, A or BBB by Standard & Poor's, an NRSRO, would be rated in the first, second, third or fourth ratings category, respectively. Securities rated below investment grade (or noninvestment-grade securities) are securities that do not receive investment grade ratings (i.e., generally ratings below one of the four highest rating categories) by an NRSRO or unrated securities of comparable quality. For example, securities rated B or BB by Standard & Poor's, an NRSRO, would be noninvestment-grade securities.

Medium-quality securities generally include securities rated in the third or fourth highest rating category by an NRSRO and unrated securities of comparable quality. For example, tax-exempt securities rated A and BBB by Standard & Poor's, an NRSRO, are rated in the third (A) and fourth (BBB) highest rating categories, respectively. Under relevant SEC guidance, the Fund is permitted to invest in medium-quality and other investment-grade, tax-exempt securities to a greater degree than a high-yield bond fund that does not invest primarily in tax-exempt municipal securities. The Fund invests at least a majority of its assets in medium-quality or noninvestment-grade, tax-exempt securities in an attempt to pursue a higher level of current income than a tax-exempt bond fund that invests purely in investment-grade securities.

Although medium-quality securities are still considered investment-grade securities, lower credit ratings do correspond to higher perceived credit risk. Medium-quality, tax-exempt securities generally are subject to interest rate, issuer credit, counterparty credit, liquidity, tax, leverage, call, sector, prepayment, credit enhancement, economic and non-diversification risks as described in this Prospectus. Noninvestment-grade securities, which are also known as junk bonds, also generally are subject to these same risks, as well as the risks of investing in noninvestment-grade securities as described in this Prospectus. The securities in which the Fund may principally invest include tax-exempt securities, which may include, for example, general obligation bonds, special revenue bonds, private activity bonds, tax-increment financing bonds, municipal leases, zero-coupon securities, inverse floaters, municipal mortgage-backed securities and planned amortization classes. Certain of the tax-exempt securities in which the Fund invests may be subject to credit enhancement.

The Fund also may principally invest in derivative contracts (such as, for example, futures contracts, option contracts and swap contracts) and hybrid instruments to implement its investment strategies as more fully described in this Prospectus. Derivative contracts and hybrid instruments also may be subject to the risks of investing in derivative contracts and hybrid instruments as described in this Prospectus.

The Fund also may invest in certain securities or other investments as described in this Prospectus (such as market discount bonds, credit default swaps and other derivative transactions) that will likely cause the Fund to realize a limited amount of ordinary income or short-term capital gains (which are treated as ordinary income for federal income tax purposes).

The Fund invests its assets so that at least 80% of the income that it distributes will be exempt from federal regular income tax, except when investing for "defensive" purposes. This policy may not be changed without shareholder approval.

What are the Main Risks of Investing in the Fund?

All mutual funds take investment risks. Therefore, it is possible to lose money by investing in the Fund. The primary factors that may reduce the Fund's returns include:

• Interest Rate Risk. Prices of fixed-income securities (including tax-exempt securities) generally fall when interest rates rise. Interest rate changes have a greater effect on prices of fixed-income securities with longer durations.

• Issuer Credit Risk. It is possible that interest or principal on securities will not be paid when due. Noninvestment-grade securities generally have a higher default risk than investment-grade securities. Such non-payment or default may reduce the value of the Fund's portfolio holdings, its share price and its performance.

• Counterparty Credit Risk. A party to a transaction involving the Fund may fail to meet its obligations. This could cause the Fund to lose money or to lose the benefit of the transaction or prevent the Fund from selling or buying other securities to implement its investment strategies.

• Liquidity Risk. Certain securities in which the Fund invests may be less readily marketable and may be subject to greater fluctuation in price than other securities. These features may make it more difficult to sell or buy a security at a favorable price or time. Noninvestment-grade securities generally have less liquidity than investment-grade securities. Liquidity risk also refers to the possibility that the Fund may not be able to sell a security or close out a derivative contract when it wants to. Over-the-counter derivative contracts generally carry greater liquidity risk than exchange-traded contracts.

• Tax Risk. In order to be tax-exempt, tax-exempt securities must meet certain legal requirements. Failure to meet such requirements may cause the interest received and distributed by the Fund to shareholders to be taxable. The federal income tax treatment of payments in respect of certain derivative contracts is unclear. The Fund also may invest in market discount bonds, enter into credit default swap arrangements and other derivative transactions, and engage in other permissible activities that will likely cause the Fund to realize a limited amount of ordinary income or short-term capital gains (which are treated as ordinary income for federal income tax purposes). Consequently, for each of these reasons, the Fund may receive payments, and make distributions, that are treated as ordinary income for federal income tax purposes. Income from the Fund also may be subject to AMT.

• Leverage Risk. Leverage risk is created when an investment, which includes, for example, a derivative contract, exposes the Fund to a level of risk that exceeds the amount invested. Changes in the value of such an investment magnify the Fund's risk of loss and potential for gain. Investments can have these same results if their returns are based on a multiple of a specified index, security or other benchmark.

• Call Risk. The Fund's performance may be adversely affected by the possibility that an issuer of a security held by the Fund may redeem the security prior to maturity at a price below or above its current market value.

• Sector Risk. A substantial part of the Fund's portfolio may be comprised of securities issued or credit enhanced by companies in similar businesses, or with other similar charateristics.  As a result, the Fund will be more susceptible to any economic, business, political or other developments which generally affect these entities.

• Prepayment Risk. When homeowners prepay their mortgages in response to lower interest rates, the Fund will be required to reinvest the proceeds at the lower interest rates available. Also, when interest rates fall, the price of municipal mortgage-backed securities may not rise to as great an extent as that of other fixed-income securities.

• Credit Enhancement Risk. The securities in which the Fund invests may be subject to credit enhancement (for example, guarantees, letters of credit or bond insurance). If the credit quality of the credit enhancement provider (for example, a bank or bond insurer) is downgraded, the rating on a security credit enhanced by such credit enhancement provider also may be downgraded. Having multiple securities credit enhanced by the same enhancement provider will increase the adverse effects on the Fund that are likely to result from a downgrading of, or a default by, such an enhancement provider. Adverse developments in the banking or bond insurance industries also may negatively affect the Fund.

• Non-Diversification Risk. The Fund is non-diversified. Compared to diversified mutual funds, it may invest a higher percentage of its assets among fewer issuers of portfolio securities. This increases the Fund's risk by magnifying the impact (positively or negatively) that any one issuer has on the Fund's Share price and performance.

• Risk Associated with Noninvestment-Grade Securities. The Fund may invest a portion of its assets in securities that are below investment-grade quality (which are also known as junk bonds), which may be subject to greater economic, credit and liquidity risks than investment-grade securities.

• Risk Related to the Economy. Lower-grade bond returns are sensitive to changes in the economy. The value of the Fund's portfolio may decline in tandem with a drop in the overall value of the stock market based on negative developments in the U.S. and global economies.

• Risk of Investing in Derivative Contracts and Hybrid Instruments. Derivative contracts and hybrid instruments involve risks different from, or possibly greater than, risks associated with investing directly in securities and other traditional investments. Specific risk issues related to the use of such contracts and instruments include valuation and tax issues, increased potential for losses and/or costs to the Fund, and a potential reduction in gains to the Fund. Each of these issues is described in greater detail in this Prospectus. Derivative contracts and hybrid instruments may also involve other risks described in this Prospectus or the Fund's Statement of Additional Information (SAI), such as interest rate, credit, liquidity and leverage risks.

• Technology Risk. The Adviser uses various technology in managing the Fund, consistent with its investment objective and strategy described in this Prospectus. For example, proprietary and third-party data and systems are utilized to support decision making for the Fund.  Data imprecision, software or other technology malfunctions, programming inaccuracies and similar circumstances may impair the performance of these systems, which may negatively affect Fund performance.

The Shares offered by this Prospectus are not deposits or obligations of any bank, are not endorsed or guaranteed by any bank and are not insured or guaranteed by the U.S. government, the Federal Deposit Insurance Corporation, the Federal Reserve Board or any other government agency.

Performance: Bar Chart and Table

Risk/Return Bar Chart

The Fund is a portfolio of Federated Municipal Securities Income Trust (the "Trust"), and is the successor to Federated Municipal High Yield Advantage Fund, Inc. ("Predecessor Fund") pursuant to a reorganization as of the close of business on November 10, 2006. Prior to the date of the reorganization, the Fund did not have any investment operations. Accordingly, the performance information and financial information, including information on fees and expenses, provided in this Prospectus for periods prior to the close of business on November 10, 2006, is historical information for the Predecessor Fund. On the date of the reorganization, November 10, 2006, the Predecessor Fund's assets (inclusive of liabilities recorded on the Predecessor Fund's records) were transferred into the Fund and the dissolution of the Predecessor Fund occurred within a short period of time after the date of the reorganization. As a result of the reorganization, the Fund does not have a different investment adviser than the Predecessor Fund, and the shareholders of A class, B class, C class and F class shares of the Predecessor Fund received A class, B class, C class or F class shares of the Fund, respectively. The bar chart and performance table below reflect historical performance data for the Fund and are intended to help you analyze the Fund's investment risks in light of its historical returns. The bar chart shows the variability of the Fund's F class total returns on a calendar year-by-year basis. The Average Annual Total Return Table shows returns averaged over the stated periods, and includes comparative performance information. The Fund's performance will fluctuate, and past performance (before and after taxes) is not necessarily an indication of future results. Updated performance information for the Fund is available under the "Products" section at FederatedInvestors.com or by calling 1-800-341-7400.

Federated Municipal High Yield Advantage Fund - F Class

The total returns shown in the bar chart do not reflect the payment of any sales charges or recurring shareholder account fees. If these charges or fees had been included, the returns shown would have been lower.

The Fund's F class total return for the nine-month period from January 1, 2013 to September 30, 2013 was (7.29)%.

Within the periods shown in the bar chart, the Fund's F class highest quarterly return was 14.61% (quarter ended September 30, 2009). Its lowest quarterly return was (16.00)% (quarter ended December 31, 2008).

Average Annual Total Return Table

The Fun's IS Class commenced operations on June 11, 2013. For the period prior to commencement of operations of the IS class, the information shown below is for the Fund's F class. The performance of the Fund's F class shown in the performance table below has been adjusted to reflect the expenses of the Fund's IS class for each year for which the expenses of the Fund's IS class would have exceeded the actual expenses paid by the Fund's F class. The performance of the Fund's F class has also been adjusted to reflect differences in sales loads and charges imposed on the purchase and redemption of the Fund's IS class. In addition to Return Before Taxes, Return After Taxes is shown for the Fund's F class to illustrate the effect of federal taxes on Fund returns. After-tax returns are shown only for the F class and after-tax returns for A, B, C and IS classes will differ from those shown for F class. Actual after-tax returns depend on each investor's personal tax situation, and are likely to differ from those shown. After-tax returns are calculated using a standard set of assumptions. The stated returns assume the highest historical federal income and capital gains tax rates. The after-tax returns do not reflect the effect of any applicable state and local taxes. After-tax returns are not relevant to investors holding shares through a 401(k) plan, an Individual Retirement Account or other tax-advantaged investment plan.

(For the Period Ended December 31, 2012)

Average Annual Total Returns Federated Municipal High Yield Advantage Fund		1 Year	5 Years	10 Years
F		11.21%	4.93%	4.93%
F Return After Taxes on Distributions		11.21%	4.93%	4.93%
F Return after Taxes on Distributions and Sale of Fund Shares		9.02%	4.96%	4.98%
A		8.35%	4.19%	4.57%
B		6.93%	4.04%	4.41%
C		11.42%	4.35%	4.25%
IS		13.28%	5.05%	4.97%
S&P Municipal Bond Index (reflects no deduction for fees, expenses or taxes)	[1]	7.41%	5.78%	5.19%
S&P 25% A and Higher/25% BBB/50% High Yield, All 3-Year Plus Sub-Index (reflects no deduction for fees, expenses or taxes)	[2]	12.80%	6.00%	6.28%
Morningstar High Yield Municipal Funds Category Average	[3]	13.77%	4.97%	4.87%

[1] The Fund has adopted a Distribution (12b-1) Plan for its Class A shares and Class F shares pursuant to which the A class and F class of the Fund may incur or charge a Distribution (12b-1) fee of up to a maximum amount of 0.05%. No such fee is currently incurred or charged by the A class or the F class of the Fund. The A class and F class of the Fund will not incur or charge such a Distribution (12b-1) fee until such time as approved by the Fund's Board of Trustees (the "Trustees").

[2] The Adviser and its affiliates have voluntarily agreed to waive their fees and/or reimburse expenses so that the total annual fund operating expenses (excluding Acquired Fund Fees and Expenses, extraordinary expenses and proxy-related expenses paid by the Fund, if any) paid by the Fund's A, B, C ,F and IS classes (after the voluntary waivers and/or reimbursements) will not exceed 0.89%, 1.64%, 1.64%, 0.89% and 0.64% (the "Fee Limit"), respectively, up to but not including the later of (the "Termination Date"): (a) November 1, 2014; or (b) the date of the Fund's next effective Prospectus. While the Adviser and its affiliates currently do not anticipate terminating or increasing these arrangements prior to the Termination Date, these arrangements may only be terminated or the Fee Limit increased prior to the Termination Date with the agreement of the Trustees.

[1] The S&P Municipal Bond Index (Main Index) is a broad, comprehensive, market value-weighted index composed of approximately 55,000 bond issues that are exempt from U.S. federal income taxes or subject to the alternative minimum tax (AMT). Eligibility criteria for inclusion in the Main Index include, but are not limited to: the bond issuer must be a state (including the Commonwealth of Puerto Rico and U.S. territories) or local government or a state or local government entity where interest on the bond is exempt from U.S. federal income taxes or subject to the AMT; the bond must be held by a mutual fund for which Standard & Poor's Securities Evaluations, Inc. provides prices; it must be denominated in U.S. dollars and have a minimum par amount of $2 million; and the bond must have a minimum term to maturity and/or call date greater than or equal to one calendar month. The Main Index is rebalanced monthly.

[2] The S&P 25% A and Higher/25% BBB/50% High Yield, All 3-Year Plus Sub-Index is a custom blended index that represents, by market weighting, 25% of the A-rated and higher component of the Main Index, 25% of the BBB-rated component of the Main Index and 50% of the below investment-grade (bonds with ratings of less than BBB-/Baa3) component of the Main Index, all with remaining maturities of three years or more.

[3] Morningstar figures represent the average of the total returns reported by all the mutual funds designated by Morningstar as falling into the respective category indicated. Funds designated within the Morningstar High Yield Municipal Funds Category Average include those that invest at least 50% of assets in high-income municipal securities that are not rated or that are rated by a major agency such as Standard & Poor's or Moody's Investor Service at the level of BBB (considered part of the high-yield universe within the municipal industry) and below.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	Federated Municipal Securities Income Trust
Prospectus Date	rr_ProspectusDate	Oct. 31, 2013
Federated Michigan Intermediate Municipal Trust
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Federated Michigan Intermediate Municipal Trust (the "Fund")
Objective [Heading]	rr_ObjectiveHeading	RISK/RETURN SUMMARY: INVESTMENT OBJECTIVE
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The Fund's investment objective is to provide current income exempt from federal regular income tax and personal income taxes imposed by the state of Michigan and Michigan municipalities.
Expense [Heading]	rr_ExpenseHeading	RISK/RETURN SUMMARY: FEES AND EXPENSES
Expense Narrative [Text Block]	rr_ExpenseNarrativeTextBlock	This table describes the fees and expenses that you may pay if you buy and hold Class A Shares (A) of the Fund. You may qualify for certain sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in certain classes (e.g., A class) of Federated funds. More information about these and other discounts is available from your financial professional and in the "What Do Shares Cost?" section of the Prospectus on page 14.
Shareholder Fees Caption [Text]	rr_ShareholderFeesCaption	Shareholder Fees (fees paid directly from your investment)
Operating Expenses Caption [Text]	rr_OperatingExpensesCaption	Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	November 1, 2014
Fee Waiver Or Reimbursement Over Assets Later Of Termination Or Next Effective Prosepectus	fmsit1_FeeWaiverOrReimbursementOverAssetsLaterOfTerminationOrNextEffectiveProsepectus	up to but not including the later of (the "Termination Date"): (a) November 1, 2014; or (b) the date of the Fund's next effective Prospectus.
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	Portfolio Turnover
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was 8% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	8.00%
Expense Breakpoint Discounts [Text]	rr_ExpenseBreakpointDiscounts	You may qualify for certain sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in certain classes (e.g., A class) of Federated funds.
Expense Breakpoint, Minimum Investment Required [Amount]	rr_ExpenseBreakpointMinimumInvestmentRequiredAmount	$ 50,000
Expense Example [Heading]	rr_ExpenseExampleHeading	Example
Expense Example Narrative [Text Block]	rr_ExpenseExampleNarrativeTextBlock	This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 for the time periods indicated and then redeem all of your Shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that operating expenses are as shown in the table above and remain the same. Although your actual costs and returns may be higher or lower, based on these assumptions your costs would be:
Strategy [Heading]	rr_StrategyHeading	RISK/RETURN SUMMARY: INVESTMENTS, RISKS and PERFORMANCE What are the Fund's Main Investment Strategies?
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	The Fund pursues its objective by investing at least a majority of its assets in a portfolio of tax-exempt securities so that, normally (except as discussed herein), distributions of annual interest income are exempt from federal regular income tax and the personal income taxes imposed by the state of Michigan and Michigan municipalities. Interest from the Fund's investments may be subject to the federal alternative minimum tax (AMT) for individuals and corporations. The Fund's portfolio securities will be investment grade or of comparable quality. Investment-grade securities are securities that receive investment grade ratings (i.e., generally ratings in the first, second, third or fourth highest rating category) by a nationally recognized statistical ratings organization (NRSRO) or unrated securities of comparable quality. For example, securities rated AAA, AA, A or BBB by Standard & Poor's, an NRSRO, would be rated in the first, second, third or fourth highest rating category, respectively. The Fund's dollar-weighted average portfolio maturity is between three and ten years, and its average-weighted duration is between three and seven years. The securities in which the Fund may principally invest include tax-exempt securities, which may include, for example, general obligation bonds, special revenue bonds, private activity bonds, tax-increment financing bonds, municipal leases, zero-coupon securities, inverse floaters, municipal mortgage-backed securities and planned amortization classes. Certain of the tax-exempt securities in which the Fund invests may be subject to credit enhancement. The Fund also may principally invest in derivative contracts (such as, for example, futures contracts, option contracts and swap contracts) and hybrid instruments to implement its investment strategies as more fully described in this Prospectus. The Fund also may invest in certain securities or other investments as described in this Prospectus (such as market discount bonds, credit default swaps and other derivative transactions) that will likely cause the Fund to realize a limited amount of ordinary income or short-term capital gains (which are treated as ordinary income for federal income tax purposes). Because the Fund refers to Michigan municipal investments in its name, it has an investment policy that it will normally invest its assets so that at least 80% of the income that it distributes will be exempt from federal regular income tax and the personal income taxes imposed by the state of Michigan and Michigan municipalities. This policy may not be changed without shareholder approval.
Risk [Heading]	rr_RiskHeading	What are the Main Risks of Investing in the Fund?
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	All mutual funds take investment risks. Therefore, it is possible to lose money by investing in the Fund. The primary factors that may reduce the Fund's returns include: Interest Rate Risk. Prices of fixed-income securities (including tax-exempt securities) generally fall when interest rates rise. Interest rate changes have a greater effect on prices of fixed-income securities with longer durations. Issuer Credit Risk. It is possible that interest or principal on securities will not be paid when due. Such non-payment or default may reduce the value of the Fund's portfolio holdings, its share price and its performance. Counterparty Credit Risk. A party to a transaction involving the Fund may fail to meet its obligations. This could cause the Fund to lose money or to lose the benefit of the transaction or prevent the Fund from selling or buying other securities to implement its investment strategies. Liquidity Risk. Certain securities in which the Fund invests may be less readily marketable and may be subject to greater fluctuation in price than other securities. These features may make it more difficult to sell or buy a security at a favorable price or time. Liquidity risk also refers to the possibility that the Fund may not be able to sell a security or close out a derivative contract when it wants to. Over-the-counter derivative contracts generally carry greater liquidity risk than exchange-traded contracts. Tax Risk. In order to be tax-exempt, tax-exempt securities must meet certain legal requirements. Failure to meet such requirements may cause the interest received and distributed by the Fund to shareholders to be taxable. The federal income tax treatment of payments in respect of certain derivative contracts is unclear. The Fund also may invest in market discount bonds, enter into credit default swap arrangements and other derivative transactions, and engage in other permissible activities that will likely cause the Fund to realize a limited amount of ordinary income or short-term capital gains (which are treated as ordinary income for federal income tax purposes). Consequently, for each of these reasons, the Fund may receive payments, and make distributions, that are treated as ordinary income for federal income tax purposes. Income from the Fund also may be subject to AMT. Leverage Risk. Leverage risk is created when an investment, which includes, for example, a derivative contract, exposes the Fund to a level of risk that exceeds the amount invested. Changes in the value of such an investment magnify the Fund's risk of loss and potential for gain. Investments can have these same results if their returns are based on a multiple of a specified index, security or other benchmark. Call Risk. The Fund's performance may be adversely affected by the possibility that an issuer of a security held by the Fund may redeem the security prior to maturity at a price below or above its current market value. Sector Risk. Since the Fund invests at least a majority of its assets in a portfolio of Michigan tax-exempt securities, the Fund may be subject to additional risks compared to funds that invest in multiple states. Although it has diversified, Michigan's economy is still heavily dependent upon certain industries, especially automobile, manufacturing and related industries. Any downturns in these industries may adversely affect the economy of the state. A substantial part of the Fund's portfolio may be comprised of securities issued or credit enhanced by companies in similar businesses, or with other similar characteristics. As a result, the Fund will be more susceptible to any economic, business, political or other developments which generally affect these entities. Prepayment Risk. When homeowners prepay their mortgages in response to lower interest rates, the Fund will be required to reinvest the proceeds at the lower interest rates available. Also, when interest rates fall, the price of municipal mortgage-backed securities may not rise to as great an extent as that of other fixed-income securities. Credit Enhancement Risk. The securities in which the Fund invests may be subject to credit enhancement (for example, guarantees, letters of credit or bond insurance). If the credit quality of the credit enhancement provider (for example, a bank or bond insurer) is downgraded, the rating on a security credit enhanced by such credit enhancement provider also may be downgraded. Having multiple securities credit enhanced by the same enhancement provider will increase the adverse effects on the Fund that are likely to result from a downgrading of, or a default by, such an enhancement provider. Adverse developments in the banking or bond insurance industries also may negatively affect the Fund. Non-Diversification Risk. The Fund is non-diversified. Compared to diversified mutual funds, it may invest a higher percentage of its assets among fewer issuers of portfolio securities. This increases the Fund's risk by magnifying the impact (positively or negatively) that any one issuer has on the Fund's Share price and performance. Risk Related to the Economy. Lower-grade bond returns are sensitive to changes in the economy. The value of the Fund's portfolio may decline in tandem with a drop in the overall value of the stock market based on negative developments in the U.S. and global economies. Risk of Investing in Derivative Contracts and Hybrid Instruments. Derivative contracts and hybrid instruments involve risks different from, or possibly greater than, risks associated with investing directly in securities and other traditional investments. Specific risk issues related to the use of such contracts and instruments include valuation and tax issues, increased potential for losses and/or costs to the Fund, and a potential reduction in gains to the Fund. Each of these issues is described in greater detail in this Prospectus. Derivative contracts and hybrid instruments may also involve other risks described in this Prospectus or the Fund's Statement of Additional Information (SAI), such as interest rate, credit, liquidity and leverage risks. Technology Risk. The Adviser uses various technology in managing the Fund, consistent with its investment objective and strategy described in this Prospectus. For example, proprietary and third-party data and systems are utilized to support decision making for the Fund.  Data imprecision, software or other technology malfunctions, programming inaccuracies and similar circumstances may impair the performance of these systems, which may negatively affect Fund performance. The Shares offered by this Prospectus are not deposits or obligations of any bank, are not endorsed or guaranteed by any bank and are not insured or guaranteed by the U.S. government, the Federal Deposit Insurance Corporation, the Federal Reserve Board or any other government agency.
Risk Lose Money [Text]	rr_RiskLoseMoney	All mutual funds take investment risks. Therefore, it is possible to lose money by investing in the Fund.
Risk Nondiversified Status [Text]	rr_RiskNondiversifiedStatus	Non–Diversification Risk. The Fund is non-diversified. Compared to diversified mutual funds, it may invest a higher percentage of its assets among fewer issuers of portfolio securities. This increases the Fund's risk by magnifying the impact (positively or negatively) that any one issuer has on the Fund's Share price and performance.
Risk Not Insured Depository Institution [Text]	rr_RiskNotInsuredDepositoryInstitution	The Shares offered by this Prospectus are not deposits or obligations of any bank, are not endorsed or guaranteed by any bank and are not insured or guaranteed by the U.S. government, the Federal Deposit Insurance Corporation, the Federal Reserve Board or any other government agency.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance: Bar Chart and Table Risk/Return Bar Chart
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The bar chart and performance table below reflect historical performance data for the Fund and are intended to help you analyze the Fund's investment risks in light of its historical returns. The bar chart shows the variability of the Fund's A class total returns on a calendar year-by-year basis. The Average Annual Total Return Table shows returns averaged over the stated periods, and includes comparative performance information. The Fund's performance will fluctuate, and past performance (before and after taxes) is not necessarily an indication of future results. Updated performance information for the Fund is available under the "Products" section at FederatedInvestors.com or by calling 1-800-341-7400.
Performance Information Illustrates Variability of Returns [Text]	rr_PerformanceInformationIllustratesVariabilityOfReturns	The bar chart shows the variability of the Fund's A class total returns on a calendar year-by-year basis.
Performance Availability Phone [Text]	rr_PerformanceAvailabilityPhone	1-800-341-7400
Performance Availability Website Address [Text]	rr_PerformanceAvailabilityWebSiteAddress	FederatedInvestors.com
Performance Past Does Not Indicate Future [Text]	rr_PerformancePastDoesNotIndicateFuture	The Fund's performance will fluctuate, and past performance (before and after taxes) is not necessarily an indication of future results.
Bar Chart [Heading]	rr_BarChartHeading	Federated Michigan Intermediate Municipal Trust - A Class
Bar Chart Does Not Reflect Sales Loads [Text]	rr_BarChartDoesNotReflectSalesLoads	The total returns shown in the bar chart do not reflect payment of any sales charges or recurring shareholder account fees. If these charges or fees had been included, the returns shown would have been lower.
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	The total returns shown in the bar chart do not reflect payment of any sales charges or recurring shareholder account fees. If these charges or fees had been included, the returns shown would have been lower. The Fund's A class total return for the nine-month period from January 1, 2013 to September 30, 2013, was (2.79)%. Within the periods shown in the bar chart, the Fund's A class highest quarterly return was 5.33% (quarter ended September 30, 2009). Its lowest quarterly return was (3.14)% (quarter ended December 31, 2010).
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Return Table
Performance Table Uses Highest Federal Rate	rr_PerformanceTableUsesHighestFederalRate	After-tax returns are calculated using a standard set of assumptions. The stated returns assume the highest historical federal income and capital gains tax rates. These after-tax returns do not reflect the effect of any applicable state and local taxes.
Performance Table Not Relevant to Tax Deferred	rr_PerformanceTableNotRelevantToTaxDeferred	After-tax returns are not relevant to investors holding shares through tax-deferred programs, such as a 401(k) plan, an Individual Retirement Account (IRA) or other tax-advantaged investment plan.
Performance Table One Class of after Tax Shown [Text]	rr_PerformanceTableOneClassOfAfterTaxShown	In addition to Return Before Taxes, Return After Taxes is shown for the Fund's A class to illustrate the effect of federal taxes on Fund returns.
Performance Table Narrative	rr_PerformanceTableNarrativeTextBlock	In addition to Return Before Taxes, Return After Taxes is shown for the Fund's A class to illustrate the effect of federal taxes on Fund returns. Actual after-tax returns depend on each investor's personal tax situation, and are likely to differ from those shown. After-tax returns are calculated using a standard set of assumptions. The stated returns assume the highest historical federal income and capital gains tax rates. These after-tax returns do not reflect the effect of any applicable state and local taxes. After-tax returns are not relevant to investors holding shares through tax-deferred programs, such as a 401(k) plan, an Individual Retirement Account (IRA) or other tax-advantaged investment plan. (For the Periods Ended December 31, 2012)
Federated Michigan Intermediate Municipal Trust | A
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	3.00%
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, as applicable)	rr_MaximumDeferredSalesChargeOverOther	none
Maximum Sales Charge (Load) Imposed on Reinvested Dividends (and other Distributions) (as a percentage of offering price)	rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther	none
Redemption Fee (as a percentage of amount redeemed, if applicable)	rr_RedemptionFeeOverRedemption	none
Exchange Fee	rr_ExchangeFeeOverRedemption	none
Management Fee	rr_ManagementFeesOverAssets	0.40%
Distribution (12b-1) Fee	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.49%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.89%
Fee Waivers and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	0.14%	[1]
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements	rr_NetExpensesOverAssets	0.75%
1 Year	rr_ExpenseExampleYear01	388
3 Years	rr_ExpenseExampleYear03	575
5 Years	rr_ExpenseExampleYear05	778
10 Years	rr_ExpenseExampleYear10	$ 1,363
2003	rr_AnnualReturn2003	5.05%
2004	rr_AnnualReturn2004	2.59%
2005	rr_AnnualReturn2005	1.72%
2006	rr_AnnualReturn2006	3.69%
2007	rr_AnnualReturn2007	3.69%
2008	rr_AnnualReturn2008	(0.81%)
2009	rr_AnnualReturn2009	8.19%
2010	rr_AnnualReturn2010	2.64%
2011	rr_AnnualReturn2011	9.44%
2012	rr_AnnualReturn2012	5.44%
Year to Date Return, Label	rr_YearToDateReturnLabel	The Fund's A class total return for the nine-month period
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Sep. 30, 2013
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	(2.79%)
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest quarterly return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Sep. 30, 2009
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	5.33%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest quarterly return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2010
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(3.14%)
1 Year	rr_AverageAnnualReturnYear01	2.29%
5 Years	rr_AverageAnnualReturnYear05	4.27%
10 Years	rr_AverageAnnualReturnYear10	3.81%
Federated Michigan Intermediate Municipal Trust | Return After Taxes on Distributions | A
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	2.25%
5 Years	rr_AverageAnnualReturnYear05	4.26%
10 Years	rr_AverageAnnualReturnYear10	3.80%
Federated Michigan Intermediate Municipal Trust | Return After Taxes on Distributions and Sale of Fund Shares | A
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	2.60%
5 Years	rr_AverageAnnualReturnYear05	4.17%
10 Years	rr_AverageAnnualReturnYear10	3.79%
Federated Michigan Intermediate Municipal Trust | S&P Municipal Bond Intermediate Index (reflects no deduction of fees, expenses or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	5.34%	[2]
5 Years	rr_AverageAnnualReturnYear05	6.12%	[2]
10 Years	rr_AverageAnnualReturnYear10	5.14%	[2]
Federated Michigan Intermediate Municipal Trust | Morningstar Municipal Single State Intermediate Funds Category Average
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	4.72%	[3]
5 Years	rr_AverageAnnualReturnYear05	4.53%	[3]
10 Years	rr_AverageAnnualReturnYear10	3.74%	[3]

[1] Effective November 1, 2013, the Adviser and its affiliates have voluntarily agreed to waive their fees and/or reimburse expenses so that the total annual fund operating expenses (excluding Acquired Fund Fees and Expenses, extraordinary expenses and proxy-related expenses paid by the Fund, if any) paid by the Fund's A class (after the voluntary waivers and/or reimbursements) will not exceed 0.75% (the "Fee Limit") up to but not including the later of (the "Termination Date"): (a) November 1, 2014; or (b) the date of the Fund's next effective Prospectus. While the Adviser and its affiliates currently do not anticipate terminating or increasing these arrangements prior to the Termination Date, these arrangements may only be terminated or the Fee Limit increased prior to the Termination Date with the agreement of the Fund's Board of Trustees.

[2] The S&P Municipal Bond Intermediate Index consists of bonds in the S&P Municipal Bond Index (Main Index) with a minimum maturity of three years and a maximum maturity of up to, but not including, 15 years as measured from the rebalancing date of the Main Index. The Main Index is a broad, comprehensive, market value-weighted index composed of approximately 55,000 bond issues that are exempt from U.S. federal income taxes or subject to the alternative minimum tax (AMT). Eligibility criteria for inclusion in the Main Index include, but are not limited to: the bond issuer must be a state (including the Commonwealth of Puerto Rico and U.S. territories) or a local government or a state or local government entity where interest on the bond is exempt from U.S. federal income taxes or subject to the AMT; the bond must be held by a mutual fund for which Standard & Poor's Securities Evaluations, Inc. provides prices; it must be denominated in U.S. dollars and have a minimum par amount of $2 million; and the bond must have a minimum term to maturity and/or call date greater than or equal to one calendar month. The Main Index is rebalanced monthly.

[3] Morningstar figures represent the average of the total returns reported by all the mutual funds designed by Morningstar as falling into the respective category indicated.

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Federated Pennsylvania Municipal Income Fund

Federated Pennsylvania Municipal Income Fund (the "Fund")

RISK/RETURN SUMMARY: INVESTMENT OBJECTIVE

The Fund's investment objective is to provide current income exempt from federal regular income tax (federal regular income tax does not include the federal alternative minimum tax (AMT)) and the personal income taxes imposed by the state of Pennsylvania and Pennsylvania municipalities.

RISK/RETURN SUMMARY: FEES AND EXPENSES

This table describes the fees and expenses that you may pay if you buy and hold Class A Shares (A) and Class B Shares (B) of the Fund. You may qualify for certain sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in certain classes (e.g., A class) of Federated funds. More information about these and other discounts is available from your financial professional and in the "What Do Shares Cost?" section of the Prospectus on page 15.

Shareholder Fees (fees paid directly from your investment)

Shareholder Fees Federated Pennsylvania Municipal Income Fund	A	B
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	4.50%	none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, as applicable)	none	5.50%
Maximum Sales Charge (Load) Imposed on Reinvested Dividends (and other Distributions) (as a percentage of offering price)	none	none
Redemption Fee (as a percentage of amount redeemed, if applicable)	none	none
Exchange Fee	none	none

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses Federated Pennsylvania Municipal Income Fund		A		B
Management Fee		0.40%		0.40%
Distribution (12b-1) Fee		none	[1]	0.75%
Other Expenses		0.45%		0.45%
Total Annual Fund Operating Expenses		0.85%		1.60%
Fee Waivers and/or Expense Reimbursements	[2]	0.10%		0.08%
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements		0.75%		1.52%

Example

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds.

The Example assumes that you invest $10,000 for the time periods indicated and then redeem all of your Shares at the end of those periods. Expenses assuming no redemption are also shown. The Example also assumes that your investment has a 5% return each year and that operating expenses are as shown in the table above and remain the same. Although your actual costs and returns may be higher or lower, based on these assumptions your costs would be:

Expense Example Federated Pennsylvania Municipal Income Fund (USD $)	1 Year	3 Years	5 Years	10 Years
A	533	709	900	1,452
B	713	905	1,071	1,699

Expense Example, No Redemption Federated Pennsylvania Municipal Income Fund (USD $)	1 Year	3 Years	5 Years	10 Years
A	533	709	900	1,452
B	163	505	871	1,699

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was 7% of the average value of its portfolio.

RISK/RETURN SUMMARY: INVESTMENTS, RISKS and PERFORMANCE

What are the Fund's Main Investment Strategies?

The Fund pursues its objective by investing its assets so that, normally (except as discussed herein), distributions of annual interest income are exempt from federal regular income tax and the Commonwealth of Pennsylvania personal income tax. Interest from the Fund's investments may be subject to the federal AMT for individuals and corporations.

The Fund does not limit itself to securities of a particular maturity range. Currently, at least a majority of the Fund's assets will be invested in long-term securities (i.e., securities with stated maturities of 10 years or more).

The Fund also will invest at least a majority of its assets in securities rated investment-grade (or unrated securities of comparable quality), and may purchase securities rated below investment-grade (or unrated securities of comparable quality), which are also known as junk bonds, up to 49% of its assets. Investment-grade securities are securities that receive investment-grade ratings (i.e., generally ratings in the first, second, third or fourth highest rating category) by a nationally recognized statistical rating organization (NRSRO) or unrated securities of comparable quality. For example, securities rated AAA, AA, A or BBB by Standard & Poor's, an NRSRO, would be rated in the first, second, third or fourth ratings category, respectively. Securities rated below investment-grade (or noninvestment-grade securities) are securities that do not receive investment-grade ratings (i.e., generally ratings below one of the four highest rating categories) by an NRSRO or unrated securities of comparable quality. For example, securities rated B or BB by Standard & Poor's, an NRSRO, would be noninvestment-grade securities. The Fund does not have a specific minimum quality rating.

The securities in which the Fund may principally invest include tax-exempt securities, which may include, for example, general obligation bonds, special revenue bonds, private activity bonds, tax-increment financing bonds, municipal leases, zero-coupon securities, inverse floaters, municipal mortgage-backed securities and planned amortization classes. Certain of the tax-exempt securities in which the Fund invests may be subject to credit enhancement.

The Fund also may principally invest in derivative contracts (such as, for example, futures contracts, option contracts and swap contracts) and hybrid instruments to implement its investment strategies as more fully described in this Prospectus.

The Fund also may invest in certain securities or other investments as described in this Prospectus (such as market discount bonds, credit default swaps and other derivative transactions) that will likely cause the Fund to realize a limited amount of ordinary income or short-term capital gains (which are treated as ordinary income for federal income tax purposes).

Because the Fund refers to Pennsylvania municipal investments in its name, it has an investment policy that it will normally invest its assets so that at least 80% of the income that it distributes will be exempt from federal regular income tax and the Commonwealth of Pennsylvania personal income tax. This policy may not be changed without shareholder approval.

What are the Main Risks of Investing in the Fund?

All mutual funds take investment risks. Therefore, it is possible to lose money by investing in the Fund. The primary factors that may reduce the Fund's returns include:

• Interest Rate Risk. Prices of fixed-income securities (including tax-exempt securities) generally fall when interest rates rise. Interest rate changes have a greater effect on prices of fixed-income securities with longer durations.

• Issuer Credit Risk. It is possible that interest or principal on securities will not be paid when due. Noninvestment-grade securities generally have a higher default risk than investment-grade securities. Such non-payment or default may reduce the value of the Fund's portfolio holdings, its share price and its performance.

• Counterparty Credit Risk. A party to a transaction involving the Fund may fail to meet its obligations. This could cause the Fund to lose money or to lose the benefit of the transaction or prevent the Fund from selling or buying other securities to implement its investment strategies.

• Liquidity Risk. Certain securities in which the Fund invests may be less readily marketable and may be subject to greater fluctuation in price than other securities. These features may make it more difficult to sell or buy a security at a favorable price or time. Noninvestment-grade securities generally have less liquidity than investment-grade securities. Liquidity risk also refers to the possibility that the Fund may not be able to sell a security or close out a derivative contract when it wants to. Over-the-counter derivative contracts generally carry greater liquidity risk than exchange-traded contracts.

• Tax Risk. In order to be tax-exempt, tax-exempt securities must meet certain legal requirements. Failure to meet such requirements may cause the interest received and distributed by the Fund to shareholders to be taxable. The federal income tax treatment of payments in respect of certain derivative contracts is unclear. The Fund also may invest in market discount bonds, enter into credit default swap arrangements and other derivative transactions, and engage in other permissible activities that will likely cause the Fund to realize a limited amount of ordinary income or short-term capital gains (which are treated as ordinary income for federal income tax purposes). Consequently, for each of these reasons, the Fund may receive payments, and make distributions, that are treated as ordinary income for federal income tax purposes. Income from the Fund also may be subject to AMT.

• Leverage Risk. Leverage risk is created when an investment, which includes, for example, a derivative contract, exposes the Fund to a level of risk that exceeds the amount invested. Changes in the value of such an investment magnify the Fund's risk of loss and potential for gain. Investments can have these same results if their returns are based on a multiple of a specified index, security or other benchmark.

• Call Risk. The Fund's performance may be adversely affected by the possibility that an issuer of a security held by the Fund may redeem the security prior to maturity at a price below or above its current market value.

• Sector Risk. Since the Fund invests at least a majority of its assets in a portfolio of: (1) long-term Pennsylvania tax-exempt securities; and (2) investment-grade Pennsylvania tax-exempt securities, the Fund may be subject to additional risks compared to funds that invest in multiple states. Pennsylvania's economy has diversified away from the concentration in heavy industry and manufacturing, which existed prior to the downsizing of the steel industry, and improved its mixture of technology-based businesses, health care services and education services. Despite the improvements in its employment base, Pennsylvania is still subject to the cyclical impact which an economic downturn has on the manufacturing sector. A substantial part of the Fund's portfolio also may be comprised of securities issued or credit enhanced by companies in similar businesses or with other similar characteristics. As a result, the Fund will be more susceptible to any economic, business, political or other developments which generally affect these issuers or entities.

• Prepayment Risk. When homeowners prepay their mortgages in response to lower interest rates, the Fund will be required to reinvest the proceeds at the lower interest rates available. Also, when interest rates fall, the price of municipal mortgage-backed securities may not rise to as great an extent as that of other fixed-income securities.

• Credit Enhancement Risk. The securities in which the Fund invests may be subject to credit enhancement (for example, guarantees, letters of credit or bond insurance). If the credit quality of the credit enhancement provider (for example, a bank or bond insurer) is downgraded, the rating on a security credit enhanced by such credit enhancement provider also may be downgraded. Having multiple securities credit enhanced by the same enhancement provider will increase the adverse effects on the Fund that are likely to result from a downgrading of, or a default by, such an enhancement provider. Adverse developments in the banking or bond insurance industries also may negatively affect the Fund.

• Non-Diversification Risk. The Fund is non-diversified. Compared to diversified mutual funds, it may invest a higher percentage of its assets among fewer issuers of portfolio securities. This increases the Fund's risk by magnifying the impact (positively or negatively) that any one issuer has on the Fund's Share price and performance.

• Risk Associated with Noninvestment-Grade Securities. The Fund may invest a portion of its assets in securities that are below investment-grade quality (which are also known as junk bonds), which may be subject to greater economic, credit and liquidity risks than investment-grade securities.

• Risk Related to the Economy. Lower-grade bond returns are sensitive to changes in the economy. The value of the Fund's portfolio may decline in tandem with a drop in the overall value of the stock market based on negative developments in the U.S. and global economies.

• Risk of Investing in Derivative Contracts and Hybrid Instruments. Derivative contracts and hybrid instruments involve risks different from, or possibly greater than, risks associated with investing directly in securities and other traditional investments. Specific risk issues related to the use of such contracts and instruments include valuation and tax issues, increased potential for losses and/or costs to the Fund, and a potential reduction in gains to the Fund. Each of these issues is described in greater detail in this Prospectus. Derivative contracts and hybrid instruments may also involve other risks described in this Prospectus or the Fund's Statement of Additional Information (SAI), such as interest rate, credit, liquidity and leverage risks.

• Technology Risk. The Adviser uses various technology in managing the Fund, consistent with its investment objective and strategy described in this Prospectus. For example, proprietary and third-party data and systems are utilized to support decision making for the Fund.  Data imprecision, software or other technology malfunctions, programming inaccuracies and similar circumstances may impair the performance of these systems, which may negatively affect Fund performance.

The Shares offered by this Prospectus are not deposits or obligations of any bank, are not endorsed or guaranteed by any bank and are not insured or guaranteed by the U.S. government, the Federal Deposit Insurance Corporation, the Federal Reserve Board or any other government agency.

Performance: Bar Chart and Table

Risk/Return Bar Chart

The bar chart and performance table below reflect historical performance data for the Fund and are intended to help you analyze the Fund's investment risks in light of its historical returns. The bar chart shows the variability of the Fund's A class total returns on a calendar year-by-year basis. The Average Annual Total Return Table shows returns averaged over the stated periods and includes comparative performance information. The Fund's performance will fluctuate, and past performance (before and after taxes) is not necessarily an indication of future results. Updated performance information for the Fund is available under the "Products" section at FederatedInvestors.com or by calling 1-800-341-7400.

Federated Pennsylvania Municipal Income Fund - A Class

The total returns shown in the bar chart do not reflect the payment of any sales charges or recurring shareholder account fees. If these charges or fees had been included, the returns shown would have been lower.

The Fund's A class total return for the nine-month period from January 1, 2013 to September 30, 2013, was (3.69)%.

Within the periods shown in the bar chart, the Fund's A class highest quarterly return was 7.17% (quarter ended September 30, 2009). Its lowest quarterly return was (4.85)% (quarter ended December 31, 2008).

Average Annual Total Return Table

In addition to Return Before Taxes, Return After Taxes is shown for the Fund's A class to illustrate the effect of federal taxes on Fund returns. After-tax returns are shown only for the A class and after tax returns for the B class will differ from those shown below for the A class. Actual after-tax returns depend on each investor's personal tax situation, and are likely to differ from those shown. After-tax returns are calculated using a standard set of assumptions. The stated returns assume the highest historical federal income and capital gains tax rates. These after-tax returns do not reflect the effect of any applicable state and local taxes. After-tax returns are not relevant to investors holding Shares through tax-deferred programs, such as a 401(k) plan, an Individual Retirement Account (IRA) or other tax-advantaged investment plan.

(For the Period Ended December 31, 2012)

Average Annual Total Returns Federated Pennsylvania Municipal Income Fund		1 Year	5 Years	10 Years
A		2.39%	3.27%	3.41%
A Return After Taxes on Distributions		2.39%	3.27%	3.41%
A Return After Taxes on Distributions and Sale of Fund Shares		2.78%	3.35%	3.50%
B		0.78%	3.07%	3.24%
S&P Municipal Bond Pennsylvania Index (reflects no deduction for fees, expenses or taxes)	[1]	6.88%	5.74%	5.18%
S&P Municipal Bond PA, Investment Grade, 3-Year Plus Sub-Index (reflects no deduction for fees, expenses or taxes)	[2]	8.00%	6.51%	5.56%
Morningstar Municipal Pennsylvania Funds Category Average	[3]	7.36%	5.08%	4.25%

[1] The Fund has adopted a Distribution (12b-1) Plan for its Class A shares pursuant to which the A class of the Fund may incur or charge a Distribution (12b-1) fee of up to a maximum amount of 0.05%. No such fee is currently incurred or charged by the A class of the Fund. The A class of the Fund will not incur or charge such a Distribution (12b-1) fee until such time as approved by the Fund's Board of Trustees (the “Trustees”).

[2] The Adviser and its affiliates have voluntarily agreed to waive their fees and/or reimburse expenses so that the total annual fund operating expenses (excluding Acquired Fund Fees and Expenses, extraordinary expenses, and proxy-related expenses, paid by the Fund, if any) paid by the Fund's A class and B class (after the voluntary waivers and/or reimbursements) will not exceed 0.75% and 1.52% (the "Fee Limit"), respectively, up to but not including the later of (the "Termination Date"): (a) November 1, 2014; or (b) the date of the Fund's next effective Prospectus. While the Adviser and its affiliates currently do not anticipate terminating or increasing these arrangements prior to the Termination Date, these arrangements may only be terminated or the Fee Limit increased prior to the Termination Date with the agreement of the Fund's Board of Trustees.

[1] The S&P Municipal Bond Pennsylvania Index (PA Index) consists of bonds in the S&P Municipal Bond Index (Main Index) that have been issued by the Commonwealth of Pennsylvania or local governments or state or local government entities within Pennsylvania. The Main Index is a broad, comprehensive, market value-weighted index composed of approximately 55,000 bond issues that are exempt from U.S. federal income taxes or subject to the alternative minimum tax (AMT). Eligibility criteria for inclusion in the Main Index include, but are not limited to: the bond issuer must be a state (including the Commonwealth of Puerto Rico and U.S. territories) or a local government or a state or local entity where interest on the bond is exempt from U.S. federal income taxes or subject to the AMT; the bond must be held by a mutual fund for which Standard & Poor's Securities Evaluations, Inc. provides prices; it must be denominated in U.S. dollars and have a minimum par amount of $2 million; and the bond must have a minimum term to maturity and/or call date greater than or equal to one calendar month. The Main Index is rebalanced monthly.

[2] The S&P Municipal Bond PA, Investment Grade, 3-Year Plus Sub-Index represents the return of the portion of the PA Index composed solely of bonds that are rated at least BBB with remaining maturities of more than three years that are not subject to AMT.

[3] Morningstar figures represent the average of the total returns reported by all the mutual funds designated by Morningstar as falling into the respective category indicated. Funds designated within the Morningstar Municipal Pennsylvania Funds Category Average include those that invest at least 80% of assets in Pennsylvania municipal debt and can include long-, intermediate- and short-duration portfolios.

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Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Document Type	dei_DocumentType	485BPOS
Document Period End Date	dei_DocumentPeriodEndDate	Aug. 31, 2013
Registrant Name	dei_EntityRegistrantName	Federated Municipal Securities Income Trust
Central Index Key	dei_EntityCentralIndexKey	0000866700
Amendment Flag	dei_AmendmentFlag	false
Document Creation Date	dei_DocumentCreationDate	Oct. 28, 2013
Document Effective Date	dei_DocumentEffectiveDate	Oct. 29, 2013
Prospectus Date	rr_ProspectusDate	Oct. 31, 2013