485BPOS

1933 Act File No.	2-57181
1940 Act File No.	811-2677

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.	92
and/or
REGISTRATION STATEMENT UNDER THE INVESTMENT COMPANY ACT OF 1940
	Amendment No.	76

FEDERATED MUNICIPAL BOND FUND, INC.

(Exact Name of Registrant as Specified in Charter)

Federated Hermes Funds

4000 Ericsson Drive

Warrendale, PA 15086-7561

(Address of Principal Executive Offices)

(412) 288-1900

(Registrant’s Telephone Number, including Area Code)

Peter J. Germain, Esquire

1001 Liberty Avenue

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 BOND FUND, INC., 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 11th day of June, 2020.

FEDERATED MUNICIPAL BOND FUND, INC.

BY: /s/ George F. Magera

George F. Magera, 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/ George F. Magera George F. Magera, Assistant Secretary	Attorney In Fact For the Persons Listed Below	June 11, 2020
J. Christopher Donahue *	President and Director (Principal Executive Officer)
Thomas R. Donahue*	Director
Lori A. Hensler*	Treasurer (Principal Financial Officer/Principal Accounting Officer)
John T. Collins*	Director
G. Thomas Hough	Director
Maureen Lally-Green*	Director
Charles F. Mansfield, Jr.*	Director
Thomas O’Neill*	Director
P. Jerome Richey*	Director
John S. Walsh*	Director
*By Power of Attorney

Federated Municipal Bond Fund, Inc. (the “Fund”)

Class A Shares (the “Classes”)

Class B Shares

Class C Shares

Class F Shares

Institutional Shares

Class T Shares

Post-Effective Amendment No. 92

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 Fund filed as part of Post-Effective Amendment No. 91 on May 26, 2020.  The exhibits filed herewith do not constitute the complete publicly filed disclosure for the Fund, and should be used in conjunction with the complete prospectuses for the Fund.

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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Class A B C F IS Shares | FEDERATED MUNICIPAL BOND FUND INC

Federated Municipal Bond Fund, Inc. (the "Fund")

RISK/RETURN SUMMARY: INVESTMENT OBJECTIVE

The Fund's investment objective is to provide for its shareholders a high level of current income which is exempt from 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 Class A Shares (A), Class B Shares (B), Class C Shares (C), Class F Shares (F) or Institutional Shares (IS) of the Fund. 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 and F classes, respectively) of Federated Hermes funds. More information about these and other discounts is available from your financial professional, in the "What Do Shares Cost?" section of the Prospectus on page 18 and in "Appendix B" to this Prospectus. If you purchase the Fund's IS Shares through a broker acting as an agent on behalf of its customers, you may be required to pay a commission to such broker; such commissions, if any, are not reflected in the Example below.

Shareholder Fees (fees paid directly from your investment)

Shareholder Fees - Class A B C F IS Shares - FEDERATED MUNICIPAL BOND FUND INC	A	B	C	F	IS
Maximum Sales Charge (Load)	4.50%	5.50%	1.00%	2.00%	none
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 - Class A B C F IS Shares - FEDERATED MUNICIPAL BOND FUND INC		A	B	C	F	IS
Management Fee		0.45%	0.45%	0.45%	0.45%	0.45%
Distribution (12b-1) Fee		none	0.75%	0.75%	none	none
Other Expenses		0.50%	0.50%	0.50%	0.50%	0.25%
Total Annual Fund Operating Expenses		0.95%	1.70%	1.70%	0.95%	0.70%
Fee Waivers and/or Expense Reimbursements	[1]	(0.11%)	(0.11%)	(0.11%)	(0.11%)	(0.11%)
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements		0.84%	1.59%	1.59%	0.84%	0.59%

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 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 - Class A B C F IS Shares - FEDERATED MUNICIPAL BOND FUND INC - USD ($)	1 Year	3 Years	5 Years	10 Years
A	543	739	952	1,564
B	723	936	1,123	1,810
C	273	536	923	2,009
F	296	500	620	1,255
IS	72	224	390	871

Expense Example, No Redemption - Class A B C F IS Shares - FEDERATED MUNICIPAL BOND FUND INC - USD ($)	1 Year	3 Years	5 Years	10 Years
A	543	739	952	1,564
B	173	536	923	1,810
C	173	536	923	2,009
F	196	400	620	1,255
IS	72	224	390	871

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 9% of the average value of its portfolio.

RISK/RETURN SUMMARY: INVESTMENTS, RISKS and PERFORMANCE What are the Fund's Main Investment Strategies?

The Fund's investment objective is to provide for its shareholders a high level of current income which is exempt from federal regular income tax. The Fund pursues its objective by investing its assets so that normally distributions of annual interest income are exempt from federal regular income tax. The Fund's investment adviser ("Adviser") may also invest the Fund's assets in securities whose interest (while exempt from the federal regular income tax) may be subject to (or may be a specific preference item for purposes of) the federal alternative minimum income tax (AMT) for individuals.

The Adviser may lengthen or shorten duration from time to time based on its interest rate outlook, but the Fund has no set duration parameters. Duration measures the price sensitivity of a fixed-income security to changes in interest rates.

The Fund does not limit itself to securities of a particular maturity range.

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 (including modifiers, sub-categories or gradations) 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 (including modifiers, sub-categories or gradations) by Standard & Poor's, an NRSRO, would be noninvestment-grade securities. The presence of a ratings modifier, sub-category, or gradation (for example, a (+) or (-)) is intended to show relative standing within the major rating categories and does not affect the security credit rating for purposes of the Fund's investment parameters. The Fund does not have a specific minimum quality rating.

The types of securities in which the Fund may principally invest include tax-exempt securities, such as the following types: general obligation bonds, special revenue bonds, private activity bonds, tax increment financing bonds, municipal leases, zero-coupon securities, inverse floaters, municipal mortgage-backed securities, planned amortization classes, variable rate demand instruments, municipal notes and municipal auction rate securities. 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, options contracts and swap contracts) and hybrid instruments to implement its investment strategies. For example, the Fund may use derivative contracts or hybrid instruments in an attempt to benefit from changes in the value of the underlying instrument(s), to gain exposure to the municipal bond sector, to increase or decrease the effective duration of the Fund's portfolio or to hedge against potential losses. There can be no assurance that the Fund's use of derivative contracts or hybrid instruments will work as intended. Derivative investments made by the Fund are included within the Fund's 80% policy (as described below) and are calculated at market value.

The Fund also may invest in certain securities or other investments as described herein (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 will normally invest its assets so that at least 80% of the income that it distributes will be exempt from federal regular income tax. This policy may not be changed without shareholder approval.

What are the Main (or Principal) 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:

• Tax-Exempt Securities Risk. The amount of public information available about tax-exempt securities is generally less than for corporate equities or bonds. The secondary market for tax-exempt securities also tends to be less well-developed and less liquid than many other securities markets, which may limit the Fund's ability to sell its tax-exempt securities at attractive prices. Special factors, such as legislative changes, and state and local economic and business developments, may adversely affect the yield and/or value of the Fund's investments in tax-exempt securities. Tax-exempt issuers can and have defaulted on obligations, been downgraded or commenced insolvency proceedings. Like other issuers and securities, the likelihood that the credit risk associated with such issuers and such securities will increase is greater during times of economic stress and financial instability.

• 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.

• 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.

• 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.

• 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.

• Prepayment and Extension 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. When interest rates rise, homeowners are less likely to prepay their mortgages. A decreased rate of prepayments lengthens the expected maturity of a mortgage-backed security, and the price of mortgage-backed securities may decrease more than the price of other fixed income securities when interest rates rise.

• 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, such as interest rate, credit, liquidity and leverage risks.

• Risk Associated with Noninvestment-Grade Securities. Securities rated below investment-grade may be subject to greater interest rate, credit and liquidity risks than investment-grade securities. These securities are considered speculative with respect to the issuer's ability to pay interest and repay principal.

• Risk Related to the Economy. The value of the Fund's portfolio may decline in tandem with a drop in the overall value of the markets in which the Fund invests and/or other markets. Economic, political and financial conditions, industry or economic trends and developments or public health risks, such as epidemics or pandemics, may, from time to time, and for varying periods of time, cause the Fund to experience volatility, illiquidity, shareholder redemptions or other potentially adverse effects. Among other investments, lower-grade bonds may be particularly sensitive to changes in the economy.

• 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 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.

• 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.

• 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.

• Interest Rate Risk. Prices of fixed-income securities (including tax-exempt securities) generally fall when interest rates rise. The longer the duration of a fixed-income security, the more susceptible it is to interest rate risk. Recent and potential future changes in monetary policy made by central banks and/or their governments are likely to affect the level of interest rates.

• Technology Risk. The Adviser uses various technologies in managing the Fund, consistent with its investment objective(s) 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 Municipal Bond Fund, Inc. - 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 three-month period from January 1, 2020 to March 31, 2020, was (1.37)%.

Within the periods shown in the bar chart, the Fund's A class highest quarterly return was 4.07% (quarter ended June 30, 2011). Its lowest quarterly return was (5.51)% (quarter ended December 31, 2010).

Average Annual Total Return Table

The Fund's IS class commenced operations on July 27, 2017. For the periods prior to the commencement of operations of the Fund's IS class, the performance information shown below is for the Fund's A class. The performance of the A class has not been adjusted to reflect the expenses applicable to the IS class since the IS class has a lower expense ratio than the expense ratio of the A class. The performance of the A class has been adjusted to remove any voluntary waiver of the Fund expenses related to the A class that may have occurred during the periods prior to the commencement of operations of the IS class. The performance shown in the table has been adjusted to reflect differences between the sales loads and charges imposed on the purchase and redemption of the Fund's IS class and A class.

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 A class, and after-tax returns for B, C, F and IS classes will differ from those shown below for 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 a 401(k) plan, an Individual Retirement Account or other tax-advantaged investment plan.

(For the Periods Ended December 31, 2019)

Average Annual Total Returns - Class A B C F IS Shares - FEDERATED MUNICIPAL BOND FUND INC		1 Year	5 Years	10 Years
A		3.11%	2.26%	3.64%
A | Return After Taxes on Distributions		2.95%	2.21%	3.61%
A | Return After Taxes on Distributions and Sale of Fund Shares		2.98%	2.38%	3.55%
B		1.75%	2.06%	3.43%
C		6.15%	2.41%	3.27%
F		5.92%	3.01%	4.01%
IS		8.33%	3.27%	4.15%
S&P Municipal Bond Index (reflects no deduction for fees, expenses or taxes)	[1]	7.26%	3.50%	4.41%
S&P Municipal Bond 3-Year Plus Index (reflects no deduction for fees, expenses or taxes)	[2]	8.22%	4.00%	5.02%
Morningstar Municipal National Long Funds Average	[3]	8.37%	3.52%	4.38%

[1] The Adviser and certain of its affiliates, on their own initiative, have agreed to waive certain amounts of their respective fees and/or reimburse expenses. Total annual fund operating expenses (excluding acquired fund fees and expenses, interest expense, 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 0.83%, 1.58%, 1.58%, 0.83% and 0.58% (the "Fee Limit"), respectively, up to but not including the later of (the "Termination Date"): (a) June 1, 2021; 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 Directors.

[1] The S&P Municipal Bond 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 3-Year Plus Index consists of bonds in the Main Index that are rated at least "BBB-" by Standard & Poor's, "Baa3" by Moody's or "BBB-" by Fitch Ratings. All bonds must also have a minimum maturity of three years and a maximum maturity of up to, but not including, fifteen years as measured from the rebalancing date.

[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.

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Class T Shares | FEDERATED MUNICIPAL BOND FUND INC

Federated Municipal Bond Fund, Inc. (the "Fund")

RISK/RETURN SUMMARY: INVESTMENT OBJECTIVE

The Fund's investment objective is to provide for its shareholders a high level of current income which is exempt from 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 T Shares (T).

Shareholder Fees (fees paid directly from your investment)

Shareholder Fees	Class T Shares FEDERATED MUNICIPAL BOND FUND INC T
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	2.50%
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	Class T Shares FEDERATED MUNICIPAL BOND FUND INC T
Management Fee	0.45%
Distribution (12b-1) Fee	none
Other Expenses	0.50%	[1]
Total Annual Fund Operating Expenses	0.95%
Fee Waivers and/or Expense Reimbursements	(0.11%)	[2]
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements	0.84%

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	Class T Shares FEDERATED MUNICIPAL BOND FUND INC T USD ($)
1 Year	$ 345
3 Years	545
5 Years	762
10 Years	$ 1,387

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 9% of the average value of its portfolio.

RISK/RETURN SUMMARY: INVESTMENTS, RISKS and PERFORMANCE What are the Fund's Main Investment Strategies?

The Fund's investment objective is to provide for its shareholders a high level of current income which is exempt from federal regular income tax. The Fund pursues its objective by investing its assets so that normally distributions of annual interest income are exempt from federal regular income tax. The Fund's investment adviser ("Adviser") may also invest the Fund's assets in securities whose interest (while exempt from the federal regular income tax) may be subject to (or may be a specific preference item for purposes of) the federal alternative minimum income tax (AMT) for individuals.

The Adviser may lengthen or shorten duration from time to time based on its interest rate outlook, but the Fund has no set duration parameters. Duration measures the price sensitivity of a fixed-income security to changes in interest rates.

The Fund does not limit itself to securities of a particular maturity range.

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 (including modifiers, sub-categories or gradations) 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 (including modifiers, sub-categories or gradations) by Standard & Poor's, an NRSRO, would be noninvestment-grade securities. The presence of a ratings modifier, sub-category, or gradation (for example, a (+) or (-)) is intended to show relative standing within the major rating categories and does not affect the security credit rating for purposes of the Fund's investment parameters. The Fund does not have a specific minimum quality rating.

The types of securities in which the Fund may principally invest include tax-exempt securities, such as the following types: general obligation bonds, special revenue bonds, private activity bonds, tax increment financing bonds, municipal leases, zero-coupon securities, inverse floaters, municipal mortgage-backed securities, planned amortization classes, variable rate demand instruments, municipal notes and municipal auction rate securities. 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, options contracts and swap contracts) and hybrid instruments to implement its investment strategies. For example, the Fund may use derivative contracts or hybrid instruments in an attempt to benefit from changes in the value of the underlying instrument(s), to gain exposure to the municipal bond sector, to increase or decrease the effective duration of the Fund's portfolio or to hedge against potential losses. There can be no assurance that the Fund's use of derivative contracts or hybrid instruments will work as intended. Derivative investments made by the Fund are included within the Fund's 80% policy (as described below) and are calculated at market value.

The Fund also may invest in certain securities or other investments as described herein (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 will normally invest its assets so that at least 80% of the income that it distributes will be exempt from federal regular income tax. This policy may not be changed without shareholder approval.

What are the Main (or Principal) 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:

• Tax-Exempt Securities Risk. The amount of public information available about tax-exempt securities is generally less than for corporate equities or bonds. The secondary market for tax-exempt securities also tends to be less well-developed and less liquid than many other securities markets, which may limit the Fund's ability to sell its tax-exempt securities at attractive prices. Special factors, such as legislative changes, and state and local economic and business developments, may adversely affect the yield and/or value of the Fund's investments in tax-exempt securities. Tax-exempt issuers can and have defaulted on obligations, been downgraded or commenced insolvency proceedings. Like other issuers and securities, the likelihood that the credit risk associated with such issuers and such securities will increase is greater during times of economic stress and financial instability.

• 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.

• 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.

• 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.

• 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.

• Prepayment and Extension 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. When interest rates rise, homeowners are less likely to prepay their mortgages. A decreased rate of prepayments lengthens the expected maturity of a mortgage-backed security, and the price of mortgage-backed securities may decrease more than the price of other fixed income securities when interest rates rise.

• 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, such as interest rate, credit, liquidity and leverage risks.

• Risk Associated with Noninvestment-Grade Securities. Securities rated below investment-grade may be subject to greater interest rate, credit and liquidity risks than investment-grade securities. These securities are considered speculative with respect to the issuer's ability to pay interest and repay principal.

• Risk Related to the Economy. The value of the Fund's portfolio may decline in tandem with a drop in the overall value of the markets in which the Fund invests and/or other markets. Economic, political and financial conditions, industry or economic trends and developments or public health risks, such as epidemics or pandemics, may, from time to time, and for varying periods of time, cause the Fund to experience volatility, illiquidity, shareholder redemptions or other potentially adverse effects. Among other investments, lower-grade bonds may be particularly sensitive to changes in the economy.

• 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 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.

• 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.

• 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.

• Interest Rate Risk. Prices of fixed-income securities (including tax-exempt securities) generally fall when interest rates rise. The longer the duration of a fixed-income security, the more susceptible it is to interest rate risk. Recent and potential future changes in monetary policy made by central banks and/or their governments are likely to affect the level of interest rates.

• Technology Risk. The Adviser uses various technologies in managing the Fund, consistent with its investment objective(s) 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. The Fund's Class T Shares ("T class") has not yet commenced operations. The Fund currently offers five other classes of shares: Class A Shares ("A class"), Class B Shares, Class C Shares, Class F Shares and Institutional Shares The T class performance information shown below is for the Fund's A class and has not been adjusted since the T class is expected to have the same net expense ratio as the A class.

The bar chart and performance table below 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 T 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 Bond Fund, Inc. - T 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 T class total return for the three-month period from January 1, 2020 to March 31, 2020, was (1.37)%.

Within the periods shown in the bar chart, the Fund's T class highest quarterly return was 4.07% (quarter ended June 30, 2011). Its lowest quarterly return was (5.51)% (quarter ended December 31, 2010).

Average Annual Total Return Table

The Fund's T class has not yet commenced operations. The T class performance information shown below is for the Fund's A class as described above.

In addition to Return Before Taxes, Return After Taxes is shown for the Fund's T 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 a 401(k) plan, an Individual Retirement Account or other tax-advantaged investment plan.

(For the Periods Ended December 31, 2019)

Average Annual Total Returns - Class T Shares - FEDERATED MUNICIPAL BOND FUND INC		1 Year	5 Years	10 Years
T		3.11%	2.26%	3.64%
T | Return After Taxes on Distributions		2.95%	2.21%	3.61%
T | Return After Taxes on Distributions and Sale of Fund Shares		2.98%	2.38%	3.55%
S&P Municipal Bond Index (reflects no deduction for fees, expenses or taxes)	[1]	7.26%	3.50%	4.41%
S&P Municipal Bond 3-Year Plus Index (reflects no deduction for fees, expenses or taxes)	[2]	8.22%	4.00%	5.02%
Morningstar Municipal National Long Funds Average	[3]	8.37%	3.52%	4.38%

[1] Because the Fund's T Shares are new, "Other Expenses" are based on estimated amounts for the current fiscal year.

[2] The Adviser and certain of its affiliates, on their own initiative, have agreed to waive certain amounts of their respective fees and/or reimburse expenses. Total annual fund operating expenses (excluding acquired fund fees and expenses, interest expense, extraordinary expenses and proxy-related expenses paid by the Fund, if any) paid by the Fund's T class (after the voluntary waivers and/or reimbursements) will not exceed 0.83% (the "Fee Limit") up to but not including the later of (the "Termination Date"): (a) June 1, 2021; 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 Directors.

[1] The S&P Municipal Bond 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 3-Year Plus Index consists of bonds in the Main Index that are rated at least "BBB-" by Standard & Poor's, "Baa3" by Moody's or "BBB-" by Fitch Ratings. All bonds must also have a minimum maturity of three years and a maximum maturity of up to, but not including, fifteen years as measured from the rebalancing date.

[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.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	FEDERATED MUNICIPAL BOND FUND INC
Prospectus Date	rr_ProspectusDate	May 31, 2020
Document Creation Date	dei_DocumentCreationDate	May 26, 2020

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	FEDERATED MUNICIPAL BOND FUND INC
Prospectus Date	rr_ProspectusDate	May 31, 2020
Class A B C F IS Shares | FEDERATED MUNICIPAL BOND FUND INC
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Federated Municipal Bond Fund, Inc. (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 for its shareholders a high level of current income which is exempt from 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 Class A Shares (A), Class B Shares (B), Class C Shares (C), Class F Shares (F) or Institutional Shares (IS) of the Fund. 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 and F classes, respectively) of Federated Hermes funds. More information about these and other discounts is available from your financial professional, in the "What Do Shares Cost?" section of the Prospectus on page 18 and in "Appendix B" to this Prospectus. If you purchase the Fund's IS Shares through a broker acting as an agent on behalf of its customers, you may be required to pay a commission to such broker; such commissions, if any, are not reflected in the Example below.
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	June 1, 2021
Fee Waiver Or Reimbursement Over Assets, Later Of Termination Or Next Effective Prospectus	fmsfi_FeeWaiverOrReimbursementOverAssetsLaterOfTerminationOrNextEffectiveProspectus	up to but not including the later of (the "Termination Date"): (a) June 1, 2021; 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 9% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	9.00%
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 and F classes, respectively) of Federated Hermes funds.
Expense Exchange Traded Fund Commissions [Text]	rr_ExpenseExchangeTradedFundCommissions	If you purchase the Fund's IS Shares through a broker acting as an agent on behalf of its customers, you may be required to pay a commission to such broker; such commissions, if any, are not reflected in the Example below.
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 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's investment objective is to provide for its shareholders a high level of current income which is exempt from federal regular income tax. The Fund pursues its objective by investing its assets so that normally distributions of annual interest income are exempt from federal regular income tax. The Fund's investment adviser ("Adviser") may also invest the Fund's assets in securities whose interest (while exempt from the federal regular income tax) may be subject to (or may be a specific preference item for purposes of) the federal alternative minimum income tax (AMT) for individuals. The Adviser may lengthen or shorten duration from time to time based on its interest rate outlook, but the Fund has no set duration parameters. Duration measures the price sensitivity of a fixed-income security to changes in interest rates. The Fund does not limit itself to securities of a particular maturity range. 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 (including modifiers, sub-categories or gradations) 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 (including modifiers, sub-categories or gradations) by Standard & Poor's, an NRSRO, would be noninvestment-grade securities. The presence of a ratings modifier, sub-category, or gradation (for example, a (+) or (-)) is intended to show relative standing within the major rating categories and does not affect the security credit rating for purposes of the Fund's investment parameters. The Fund does not have a specific minimum quality rating. The types of securities in which the Fund may principally invest include tax-exempt securities, such as the following types: general obligation bonds, special revenue bonds, private activity bonds, tax increment financing bonds, municipal leases, zero-coupon securities, inverse floaters, municipal mortgage-backed securities, planned amortization classes, variable rate demand instruments, municipal notes and municipal auction rate securities. 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, options contracts and swap contracts) and hybrid instruments to implement its investment strategies. For example, the Fund may use derivative contracts or hybrid instruments in an attempt to benefit from changes in the value of the underlying instrument(s), to gain exposure to the municipal bond sector, to increase or decrease the effective duration of the Fund's portfolio or to hedge against potential losses. There can be no assurance that the Fund's use of derivative contracts or hybrid instruments will work as intended. Derivative investments made by the Fund are included within the Fund's 80% policy (as described below) and are calculated at market value. The Fund also may invest in certain securities or other investments as described herein (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 will normally invest its assets so that at least 80% of the income that it distributes will be exempt from federal regular income tax. This policy may not be changed without shareholder approval.
Risk [Heading]	rr_RiskHeading	What are the Main (or Principal) 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: Tax-Exempt Securities Risk. The amount of public information available about tax-exempt securities is generally less than for corporate equities or bonds. The secondary market for tax-exempt securities also tends to be less well-developed and less liquid than many other securities markets, which may limit the Fund's ability to sell its tax-exempt securities at attractive prices. Special factors, such as legislative changes, and state and local economic and business developments, may adversely affect the yield and/or value of the Fund's investments in tax-exempt securities. Tax-exempt issuers can and have defaulted on obligations, been downgraded or commenced insolvency proceedings. Like other issuers and securities, the likelihood that the credit risk associated with such issuers and such securities will increase is greater during times of economic stress and financial instability. 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. 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. 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. 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. Prepayment and Extension 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. When interest rates rise, homeowners are less likely to prepay their mortgages. A decreased rate of prepayments lengthens the expected maturity of a mortgage-backed security, and the price of mortgage-backed securities may decrease more than the price of other fixed income securities when interest rates rise. 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, such as interest rate, credit, liquidity and leverage risks. Risk Associated with Noninvestment-Grade Securities. Securities rated below investment-grade may be subject to greater interest rate, credit and liquidity risks than investment-grade securities. These securities are considered speculative with respect to the issuer's ability to pay interest and repay principal. Risk Related to the Economy. The value of the Fund's portfolio may decline in tandem with a drop in the overall value of the markets in which the Fund invests and/or other markets. Economic, political and financial conditions, industry or economic trends and developments or public health risks, such as epidemics or pandemics, may, from time to time, and for varying periods of time, cause the Fund to experience volatility, illiquidity, shareholder redemptions or other potentially adverse effects. Among other investments, lower-grade bonds may be particularly sensitive to changes in the economy. 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 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. 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. 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. Interest Rate Risk. Prices of fixed-income securities (including tax-exempt securities) generally fall when interest rates rise. The longer the duration of a fixed-income security, the more susceptible it is to interest rate risk. Recent and potential future changes in monetary policy made by central banks and/or their governments are likely to affect the level of interest rates. Technology Risk. The Adviser uses various technologies in managing the Fund, consistent with its investment objective(s) 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 Not Insured [Text]	rr_RiskNotInsured	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 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.
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 Bond Fund, Inc. - 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 three-month period from January 1, 2020 to March 31, 2020, was (1.37)%. Within the periods shown in the bar chart, the Fund's A class highest quarterly return was 4.07% (quarter ended June 30, 2011). Its lowest quarterly return was (5.51)% (quarter ended December 31, 2010).
Performance Table Heading	rr_PerformanceTableHeading	Average Annual Total Return Table
Performance Table Does Reflect Sales Loads	rr_PerformanceTableDoesReflectSalesLoads	The performance shown in the table has been adjusted to reflect differences between the sales loads and charges imposed on the purchase and redemption of the Fund's IS class and A class.
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 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 A class, and after-tax returns for B, C, F and IS classes will differ from those shown below for A class.
Performance Table Narrative	rr_PerformanceTableNarrativeTextBlock	The Fund's IS class commenced operations on July 27, 2017. For the periods prior to the commencement of operations of the Fund's IS class, the performance information shown below is for the Fund's A class. The performance of the A class has not been adjusted to reflect the expenses applicable to the IS class since the IS class has a lower expense ratio than the expense ratio of the A class. The performance of the A class has been adjusted to remove any voluntary waiver of the Fund expenses related to the A class that may have occurred during the periods prior to the commencement of operations of the IS class. The performance shown in the table has been adjusted to reflect differences between the sales loads and charges imposed on the purchase and redemption of the Fund's IS class and A class. 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 A class, and after-tax returns for B, C, F and IS classes will differ from those shown below for 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 a 401(k) plan, an Individual Retirement Account or other tax-advantaged investment plan. (For the Periods Ended December 31, 2019)
Class A B C F IS Shares | FEDERATED MUNICIPAL BOND FUND INC | A
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load)	rr_MaximumCumulativeSalesChargeOverOfferingPrice	4.50%
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	0.45%
Distribution (12b-1) Fee	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.50%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.95%
Fee Waivers and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.11%)	[1]
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements	rr_NetExpensesOverAssets	0.84%
Expense Breakpoint, Minimum Investment Required [Amount]	rr_ExpenseBreakpointMinimumInvestmentRequiredAmount	$ 100,000
1 Year	rr_ExpenseExampleYear01	543
3 Years	rr_ExpenseExampleYear03	739
5 Years	rr_ExpenseExampleYear05	952
10 Years	rr_ExpenseExampleYear10	1,564
1 Year	rr_ExpenseExampleNoRedemptionYear01	543
3 Years	rr_ExpenseExampleNoRedemptionYear03	739
5 Years	rr_ExpenseExampleNoRedemptionYear05	952
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 1,564
2010	rr_AnnualReturn2010	0.59%
2011	rr_AnnualReturn2011	11.18%
2012	rr_AnnualReturn2012	8.39%
2013	rr_AnnualReturn2013	(4.17%)
2014	rr_AnnualReturn2014	10.03%
2015	rr_AnnualReturn2015	2.66%
2016	rr_AnnualReturn2016	0.47%
2017	rr_AnnualReturn2017	5.07%
2018	rr_AnnualReturn2018	0.07%
2019	rr_AnnualReturn2019	7.96%
Year to Date Return, Label	rr_YearToDateReturnLabel	The Fund's A class total return for the three-month period
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Mar. 31, 2020
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	(1.37%)
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest quarterly return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2011
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	4.07%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest quarterly return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2010
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(5.51%)
1 Year	rr_AverageAnnualReturnYear01	3.11%
5 Years	rr_AverageAnnualReturnYear05	2.26%
10 Years	rr_AverageAnnualReturnYear10	3.64%
Class A B C F IS Shares | FEDERATED MUNICIPAL BOND FUND INC | B
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load)	rr_MaximumCumulativeSalesChargeOverOfferingPrice	5.50%
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	0.45%
Distribution (12b-1) Fee	rr_DistributionAndService12b1FeesOverAssets	0.75%
Other Expenses	rr_OtherExpensesOverAssets	0.50%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.70%
Fee Waivers and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.11%)	[1]
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.59%
1 Year	rr_ExpenseExampleYear01	$ 723
3 Years	rr_ExpenseExampleYear03	936
5 Years	rr_ExpenseExampleYear05	1,123
10 Years	rr_ExpenseExampleYear10	1,810
1 Year	rr_ExpenseExampleNoRedemptionYear01	173
3 Years	rr_ExpenseExampleNoRedemptionYear03	536
5 Years	rr_ExpenseExampleNoRedemptionYear05	923
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 1,810
1 Year	rr_AverageAnnualReturnYear01	1.75%
5 Years	rr_AverageAnnualReturnYear05	2.06%
10 Years	rr_AverageAnnualReturnYear10	3.43%
Class A B C F IS Shares | FEDERATED MUNICIPAL BOND FUND INC | C
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load)	rr_MaximumCumulativeSalesChargeOverOfferingPrice	1.00%
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	0.45%
Distribution (12b-1) Fee	rr_DistributionAndService12b1FeesOverAssets	0.75%
Other Expenses	rr_OtherExpensesOverAssets	0.50%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.70%
Fee Waivers and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.11%)	[1]
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements	rr_NetExpensesOverAssets	1.59%
1 Year	rr_ExpenseExampleYear01	$ 273
3 Years	rr_ExpenseExampleYear03	536
5 Years	rr_ExpenseExampleYear05	923
10 Years	rr_ExpenseExampleYear10	2,009
1 Year	rr_ExpenseExampleNoRedemptionYear01	173
3 Years	rr_ExpenseExampleNoRedemptionYear03	536
5 Years	rr_ExpenseExampleNoRedemptionYear05	923
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 2,009
1 Year	rr_AverageAnnualReturnYear01	6.15%
5 Years	rr_AverageAnnualReturnYear05	2.41%
10 Years	rr_AverageAnnualReturnYear10	3.27%
Class A B C F IS Shares | FEDERATED MUNICIPAL BOND FUND INC | F
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load)	rr_MaximumCumulativeSalesChargeOverOfferingPrice	2.00%
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	0.45%
Distribution (12b-1) Fee	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.50%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.95%
Fee Waivers and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.11%)	[1]
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements	rr_NetExpensesOverAssets	0.84%
Expense Breakpoint, Minimum Investment Required [Amount]	rr_ExpenseBreakpointMinimumInvestmentRequiredAmount	$ 1,000,000
1 Year	rr_ExpenseExampleYear01	296
3 Years	rr_ExpenseExampleYear03	500
5 Years	rr_ExpenseExampleYear05	620
10 Years	rr_ExpenseExampleYear10	1,255
1 Year	rr_ExpenseExampleNoRedemptionYear01	196
3 Years	rr_ExpenseExampleNoRedemptionYear03	400
5 Years	rr_ExpenseExampleNoRedemptionYear05	620
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 1,255
1 Year	rr_AverageAnnualReturnYear01	5.92%
5 Years	rr_AverageAnnualReturnYear05	3.01%
10 Years	rr_AverageAnnualReturnYear10	4.01%
Class A B C F IS Shares | FEDERATED MUNICIPAL BOND FUND INC | IS
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load)	rr_MaximumCumulativeSalesChargeOverOfferingPrice	none
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	0.45%
Distribution (12b-1) Fee	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.25%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.70%
Fee Waivers and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.11%)	[1]
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements	rr_NetExpensesOverAssets	0.59%
1 Year	rr_ExpenseExampleYear01	$ 72
3 Years	rr_ExpenseExampleYear03	224
5 Years	rr_ExpenseExampleYear05	390
10 Years	rr_ExpenseExampleYear10	871
1 Year	rr_ExpenseExampleNoRedemptionYear01	72
3 Years	rr_ExpenseExampleNoRedemptionYear03	224
5 Years	rr_ExpenseExampleNoRedemptionYear05	390
10 Years	rr_ExpenseExampleNoRedemptionYear10	$ 871
1 Year	rr_AverageAnnualReturnYear01	8.33%
5 Years	rr_AverageAnnualReturnYear05	3.27%
10 Years	rr_AverageAnnualReturnYear10	4.15%
Class A B C F IS Shares | FEDERATED MUNICIPAL BOND FUND INC | Return After Taxes on Distributions | A
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	2.95%
5 Years	rr_AverageAnnualReturnYear05	2.21%
10 Years	rr_AverageAnnualReturnYear10	3.61%
Class A B C F IS Shares | FEDERATED MUNICIPAL BOND FUND INC | Return After Taxes on Distributions and Sale of Fund Shares | A
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	2.98%
5 Years	rr_AverageAnnualReturnYear05	2.38%
10 Years	rr_AverageAnnualReturnYear10	3.55%
Class A B C F IS Shares | FEDERATED MUNICIPAL BOND FUND INC | S&P Municipal Bond Index (reflects no deduction for fees, expenses or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	7.26%	[2]
5 Years	rr_AverageAnnualReturnYear05	3.50%	[2]
10 Years	rr_AverageAnnualReturnYear10	4.41%	[2]
Class A B C F IS Shares | FEDERATED MUNICIPAL BOND FUND INC | S&P Municipal Bond 3-Year Plus Index (reflects no deduction for fees, expenses or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	8.22%	[3]
5 Years	rr_AverageAnnualReturnYear05	4.00%	[3]
10 Years	rr_AverageAnnualReturnYear10	5.02%	[3]
Class A B C F IS Shares | FEDERATED MUNICIPAL BOND FUND INC | Morningstar Municipal National Long Funds Average
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	8.37%	[4]
5 Years	rr_AverageAnnualReturnYear05	3.52%	[4]
10 Years	rr_AverageAnnualReturnYear10	4.38%	[4]

[1] The Adviser and certain of its affiliates, on their own initiative, have agreed to waive certain amounts of their respective fees and/or reimburse expenses. Total annual fund operating expenses (excluding acquired fund fees and expenses, interest expense, 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 0.83%, 1.58%, 1.58%, 0.83% and 0.58% (the "Fee Limit"), respectively, up to but not including the later of (the "Termination Date"): (a) June 1, 2021; 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 Directors.

[2] The S&P Municipal Bond 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] The S&P Municipal Bond 3-Year Plus Index consists of bonds in the Main Index that are rated at least "BBB-" by Standard & Poor's, "Baa3" by Moody's or "BBB-" by Fitch Ratings. All bonds must also have a minimum maturity of three years and a maximum maturity of up to, but not including, fifteen years as measured from the rebalancing date.

[4] 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.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Document Type	dei_DocumentType	485BPOS
Document Period End Date	dei_DocumentPeriodEndDate	Mar. 31, 2020
Registrant Name	dei_EntityRegistrantName	FEDERATED MUNICIPAL BOND FUND INC
Central Index Key	dei_EntityCentralIndexKey	0000201801
Amendment Flag	dei_AmendmentFlag	false
Document Creation Date	dei_DocumentCreationDate	May 26, 2020
Document Effective Date	dei_DocumentEffectiveDate	May 28, 2020
Prospectus Date	rr_ProspectusDate	May 31, 2020
Entity Inv Company Type	dei_EntityInvCompanyType	N-1A

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	FEDERATED MUNICIPAL BOND FUND INC
Prospectus Date	rr_ProspectusDate	May 31, 2020
Class T Shares | FEDERATED MUNICIPAL BOND FUND INC
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Federated Municipal Bond Fund, Inc. (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 for its shareholders a high level of current income which is exempt from 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 T Shares (T).
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	June 1, 2021
Fee Waiver Or Reimbursement Over Assets, Later Of Termination Or Next Effective Prospectus	fmsfi_FeeWaiverOrReimbursementOverAssetsLaterOfTerminationOrNextEffectiveProspectus	up to but not including the later of (the "Termination Date"): (a) June 1, 2021; 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 9% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	9.00%
Other Expenses, New Fund, Based on Estimates [Text]	rr_OtherExpensesNewFundBasedOnEstimates	Because the Fund's T Shares are new, "Other Expenses" are based on estimated amounts for the current fiscal year.
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's investment objective is to provide for its shareholders a high level of current income which is exempt from federal regular income tax. The Fund pursues its objective by investing its assets so that normally distributions of annual interest income are exempt from federal regular income tax. The Fund's investment adviser ("Adviser") may also invest the Fund's assets in securities whose interest (while exempt from the federal regular income tax) may be subject to (or may be a specific preference item for purposes of) the federal alternative minimum income tax (AMT) for individuals. The Adviser may lengthen or shorten duration from time to time based on its interest rate outlook, but the Fund has no set duration parameters. Duration measures the price sensitivity of a fixed-income security to changes in interest rates. The Fund does not limit itself to securities of a particular maturity range. 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 (including modifiers, sub-categories or gradations) 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 (including modifiers, sub-categories or gradations) by Standard & Poor's, an NRSRO, would be noninvestment-grade securities. The presence of a ratings modifier, sub-category, or gradation (for example, a (+) or (-)) is intended to show relative standing within the major rating categories and does not affect the security credit rating for purposes of the Fund's investment parameters. The Fund does not have a specific minimum quality rating. The types of securities in which the Fund may principally invest include tax-exempt securities, such as the following types: general obligation bonds, special revenue bonds, private activity bonds, tax increment financing bonds, municipal leases, zero-coupon securities, inverse floaters, municipal mortgage-backed securities, planned amortization classes, variable rate demand instruments, municipal notes and municipal auction rate securities. 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, options contracts and swap contracts) and hybrid instruments to implement its investment strategies. For example, the Fund may use derivative contracts or hybrid instruments in an attempt to benefit from changes in the value of the underlying instrument(s), to gain exposure to the municipal bond sector, to increase or decrease the effective duration of the Fund's portfolio or to hedge against potential losses. There can be no assurance that the Fund's use of derivative contracts or hybrid instruments will work as intended. Derivative investments made by the Fund are included within the Fund's 80% policy (as described below) and are calculated at market value. The Fund also may invest in certain securities or other investments as described herein (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 will normally invest its assets so that at least 80% of the income that it distributes will be exempt from federal regular income tax. This policy may not be changed without shareholder approval.
Risk [Heading]	rr_RiskHeading	What are the Main (or Principal) 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: Tax-Exempt Securities Risk. The amount of public information available about tax-exempt securities is generally less than for corporate equities or bonds. The secondary market for tax-exempt securities also tends to be less well-developed and less liquid than many other securities markets, which may limit the Fund's ability to sell its tax-exempt securities at attractive prices. Special factors, such as legislative changes, and state and local economic and business developments, may adversely affect the yield and/or value of the Fund's investments in tax-exempt securities. Tax-exempt issuers can and have defaulted on obligations, been downgraded or commenced insolvency proceedings. Like other issuers and securities, the likelihood that the credit risk associated with such issuers and such securities will increase is greater during times of economic stress and financial instability. 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. 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. 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. 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. Prepayment and Extension 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. When interest rates rise, homeowners are less likely to prepay their mortgages. A decreased rate of prepayments lengthens the expected maturity of a mortgage-backed security, and the price of mortgage-backed securities may decrease more than the price of other fixed income securities when interest rates rise. 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, such as interest rate, credit, liquidity and leverage risks. Risk Associated with Noninvestment-Grade Securities. Securities rated below investment-grade may be subject to greater interest rate, credit and liquidity risks than investment-grade securities. These securities are considered speculative with respect to the issuer's ability to pay interest and repay principal. Risk Related to the Economy. The value of the Fund's portfolio may decline in tandem with a drop in the overall value of the markets in which the Fund invests and/or other markets. Economic, political and financial conditions, industry or economic trends and developments or public health risks, such as epidemics or pandemics, may, from time to time, and for varying periods of time, cause the Fund to experience volatility, illiquidity, shareholder redemptions or other potentially adverse effects. Among other investments, lower-grade bonds may be particularly sensitive to changes in the economy. 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 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. 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. 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. Interest Rate Risk. Prices of fixed-income securities (including tax-exempt securities) generally fall when interest rates rise. The longer the duration of a fixed-income security, the more susceptible it is to interest rate risk. Recent and potential future changes in monetary policy made by central banks and/or their governments are likely to affect the level of interest rates. Technology Risk. The Adviser uses various technologies in managing the Fund, consistent with its investment objective(s) 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 Not Insured [Text]	rr_RiskNotInsured	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. The Fund's Class T Shares ("T class") has not yet commenced operations. The Fund currently offers five other classes of shares: Class A Shares ("A class"), Class B Shares, Class C Shares, Class F Shares and Institutional Shares The T class performance information shown below is for the Fund's A class and has not been adjusted since the T class is expected to have the same net expense ratio as the A class. The bar chart and performance table below 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 T 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 and performance table below reflect historical performance data for the Fund. The bar chart and performance table below 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 T 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 Bond Fund, Inc. - T 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 T class total return for the three-month period from January 1, 2020 to March 31, 2020, was (1.37)%. Within the periods shown in the bar chart, the Fund's T class highest quarterly return was 4.07% (quarter ended June 30, 2011). Its lowest quarterly return was (5.51)% (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 a 401(k) plan, an Individual Retirement Account or other tax-advantaged investment plan.
Performance Table Narrative	rr_PerformanceTableNarrativeTextBlock	The Fund's T class has not yet commenced operations. The T class performance information shown below is for the Fund's A class as described above. In addition to Return Before Taxes, Return After Taxes is shown for the Fund's T 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 a 401(k) plan, an Individual Retirement Account or other tax-advantaged investment plan. (For the Periods Ended December 31, 2019)
Class T Shares | FEDERATED MUNICIPAL BOND FUND INC | T
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	2.50%
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	0.45%
Distribution (12b-1) Fee	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.50%	[1]
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	0.95%
Fee Waivers and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	(0.11%)	[2]
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements	rr_NetExpensesOverAssets	0.84%
1 Year	rr_ExpenseExampleYear01	$ 345
3 Years	rr_ExpenseExampleYear03	545
5 Years	rr_ExpenseExampleYear05	762
10 Years	rr_ExpenseExampleYear10	$ 1,387
2010	rr_AnnualReturn2010	0.59%
2011	rr_AnnualReturn2011	11.18%
2012	rr_AnnualReturn2012	8.39%
2013	rr_AnnualReturn2013	(4.17%)
2014	rr_AnnualReturn2014	10.03%
2015	rr_AnnualReturn2015	2.66%
2016	rr_AnnualReturn2016	0.47%
2017	rr_AnnualReturn2017	5.07%
2018	rr_AnnualReturn2018	0.07%
2019	rr_AnnualReturn2019	7.96%
Year to Date Return, Label	rr_YearToDateReturnLabel	The Fund's T class total return for the three-month period
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Mar. 31, 2020
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	(1.37%)
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest quarterly return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Jun. 30, 2011
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	4.07%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest quarterly return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2010
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(5.51%)
1 Year	rr_AverageAnnualReturnYear01	3.11%
5 Years	rr_AverageAnnualReturnYear05	2.26%
10 Years	rr_AverageAnnualReturnYear10	3.64%
Class T Shares | FEDERATED MUNICIPAL BOND FUND INC | Return After Taxes on Distributions | T
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	2.95%
5 Years	rr_AverageAnnualReturnYear05	2.21%
10 Years	rr_AverageAnnualReturnYear10	3.61%
Class T Shares | FEDERATED MUNICIPAL BOND FUND INC | Return After Taxes on Distributions and Sale of Fund Shares | T
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	2.98%
5 Years	rr_AverageAnnualReturnYear05	2.38%
10 Years	rr_AverageAnnualReturnYear10	3.55%
Class T Shares | FEDERATED MUNICIPAL BOND FUND INC | S&P Municipal Bond Index (reflects no deduction for fees, expenses or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	7.26%	[3]
5 Years	rr_AverageAnnualReturnYear05	3.50%	[3]
10 Years	rr_AverageAnnualReturnYear10	4.41%	[3]
Class T Shares | FEDERATED MUNICIPAL BOND FUND INC | S&P Municipal Bond 3-Year Plus Index (reflects no deduction for fees, expenses or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	8.22%	[4]
5 Years	rr_AverageAnnualReturnYear05	4.00%	[4]
10 Years	rr_AverageAnnualReturnYear10	5.02%	[4]
Class T Shares | FEDERATED MUNICIPAL BOND FUND INC | Morningstar Municipal National Long Funds Average
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	8.37%	[5]
5 Years	rr_AverageAnnualReturnYear05	3.52%	[5]
10 Years	rr_AverageAnnualReturnYear10	4.38%	[5]

[1] Because the Fund's T Shares are new, "Other Expenses" are based on estimated amounts for the current fiscal year.

[2] The Adviser and certain of its affiliates, on their own initiative, have agreed to waive certain amounts of their respective fees and/or reimburse expenses. Total annual fund operating expenses (excluding acquired fund fees and expenses, interest expense, extraordinary expenses and proxy-related expenses paid by the Fund, if any) paid by the Fund's T class (after the voluntary waivers and/or reimbursements) will not exceed 0.83% (the "Fee Limit") up to but not including the later of (the "Termination Date"): (a) June 1, 2021; 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 Directors.

[3] The S&P Municipal Bond 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 3-Year Plus Index consists of bonds in the Main Index that are rated at least "BBB-" by Standard & Poor's, "Baa3" by Moody's or "BBB-" by Fitch Ratings. All bonds must also have a minimum maturity of three years and a maximum maturity of up to, but not including, fifteen years as measured from the rebalancing date.

[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.