Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	Federated Intermediate Government Fund, Inc.
Prospectus Date	rr_ProspectusDate	Apr. 30, 2013
Federated Intermediate Government Fund, Inc.
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Federated Intermediate Government 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 total return.
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 Institutional Shares (IS) and Service Shares (SS) of the Fund.
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	May 1, 2014
Fee Waiver Or Reimbursement Over Assets Later Of Termination Date Or Next Effective Prospectus	figfi_FeeWaiverOrReimbursementOverAssetsLaterOfTerminationDateOrNextEffectiveProspectus	up to but not including the later of (the "Termination Date"): (a) May 1, 2014; or (b) the date of the Fund's next effective Prospectus.
Portfolio Turnover [Heading]	rr_PortfolioTurnoverHeading	Portfolio Turnover
Portfolio Turnover [Text Block]	rr_PortfolioTurnoverTextBlock	The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund Shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was 123% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	123.00%
Expenses Restated to Reflect Current [Text]	rr_ExpensesRestatedToReflectCurrent	Total Annual Fund Operating Expenses have been restated to reflect an anticipated decrease in Other Expenses.
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 seeks total return, which is defined as income plus capital appreciation. Under normal market conditions, the Fund invests primarily in Treasury, U.S. government securities, government agency and government agency-backed, mortgage-backed securities (MBS). The Fund will only invest in MBS that are issued or guaranteed by U.S. government agencies or U.S. government-sponsored enterprises (GSEs). The Fund typically seeks to maintain an overall average dollar-weighted portfolio duration that is within 20% above or 50% below the Barclays Intermediate Government Index (the "Index") (formerly, Barclays Capital Intermediate Government Index). At times, the Adviser's calculation of portfolio duration may result in variances outside this range. Duration is a measure of the price volatility of a fixed-income security as a result of changes in market rates of interest, based on the weighted average timing of the instrument's expected fixed interest and principal payments. The Adviser seeks to create a portfolio, consisting of U.S. Government securities, MBS, derivative instruments and other securities, that outperform the Index. Based on fundamental analysis, the Adviser will consider a variety of factors when making decisions to purchase or sell particular securities or derivative contracts. The Fund may, but is not required to, use derivative instruments, which are instruments that have a value based on another instrument, exchange rate or index, and may be used as substitutes for securities in which the Fund can invest, or to hedge against a potential loss in the underlying asset. There can be no assurance that the Fund's use of derivative instruments will work as intended. Certain of the government securities in which the Fund invests are not backed by the full faith and credit of the U.S. government, such as those issued by the Federal Home Loan Mortgage Corporation ("Freddie Mac"), the Federal National Mortgage Association ("Fannie Mae"), and the Federal Home Loan Bank System. These entities are, however, supported through federal subsidies, loans or other benefits. The Fund may also invest in government securities that are supported by the full faith and credit of the U.S. government, such as those issued by the Government National Mortgage Association ("Ginnie Mae"). Finally, the Fund may invest in a few government securities that have no explicit financial support, but which are regarded as having implied support because the federal government sponsors their activities. Because the Fund refers to U.S. government securities in its name, it will notify shareholders at least 60 days in advance of any change in its investment policies that would enable the Fund to invest, under normal circumstances, less than 80% of its assets (plus any borrowings for investment purposes) in U.S. government investments.
Risk [Heading]	rr_RiskHeading	What are the Main Risks of Investing in the Fund?
Risk Narrative [Text Block]	rr_RiskNarrativeTextBlock	All mutual funds take investment risks. Therefore, it is possible to lose money by investing in the Fund. The primary factors that may reduce the Fund's returns include: MBS Risk. A rise in interest rates may cause the value of MBS held by the Fund to decline. Certain MBS issued by GSEs are not backed by the full faith and credit of the U.S. government. The Fund's investments in collateralized mortgage obligations (CMOs) may entail greater market, prepayment and liquidity risks than other MBS. Credit Risk. It is possible that interest or principal on securities will not be paid when due. Such non-payment or default may reduce the value of the Fund's portfolio holdings, its share price and its performance. Counterparty Credit Risk. It is possible that a party to a transaction involving the Fund may fail to meet its obligations. This could cause the Fund to lose the benefit of the transaction or prevent the Fund from selling or buying other securities to implement its investment strategy. Interest Rate Risk. Prices of fixed-income securities generally fall when interest rates rise. Prepayment Risk. When homeowners prepay their mortgages in response to lower interest rates, the Fund will be required to reinvest the proceeds at the lower interest rates available. Also, when interest rates fall, the prices of MBS may not rise to as great an extent as those of other fixed-income securities due to the potential prepayment of higher interest mortgages. Liquidity Risk. The CMOs in which the Fund invests may be less readily marketable and may be subject to greater fluctuation in price than other securities. Leverage Risk. Leverage risk is created when an investment 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. Risk of Investing in Derivative Instruments. The Fund's exposure to derivative contracts and hybrid instruments (either directly or through its investment in another investment company) involves risks different from, or possibly greater than, the risks associated with investing directly in securities and other traditional investments. The use of derivatives can lead to losses because of adverse movements in the price or value of the asset, index, rate or instrument underlying a derivative, due to failure of a counterparty, or the failure of the counterparty to meet its obligations under the contract, or due to tax or regulatory constraints. Derivatives may create investment leverage in the Fund, which magnifies the Fund's exposure to the underlying investment. Derivative instruments may be difficult to value, may be illiquid and may be subject to wide swings in valuation caused by changes in the value of the underlying instrument. Over-the-counter derivative contracts generally carry greater liquidity risk than exchange-traded contracts. The loss on derivative transactions may substantially exceed the initial investment. Asset Segregation Risk. The requirement to secure its obligations in connection with certain transactions, including derivatives or other transactions that expose it to an obligation of another party, by owning underlying assets, entering into offsetting transactions or setting aside cash or liquid assets, may cause the Fund to miss favorable trading opportunities, or to realize losses on such offsetting transactions. Technology Risk. 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 Depository Institution [Text]	rr_RiskNotInsuredDepositoryInstitution	The Shares offered by this Prospectus are not deposits or obligations of any bank, are not endorsed or guaranteed by any bank and are not insured or guaranteed by the U.S. government, the Federal Deposit Insurance Corporation, the Federal Reserve Board or any other government agency.
Bar Chart and Performance Table [Heading]	rr_BarChartAndPerformanceTableHeading	Performance: Bar Chart and Table Risk/Return Bar Chart
Performance Narrative [Text Block]	rr_PerformanceNarrativeTextBlock	The bar chart and performance table below reflect historical performance data for the Fund and are intended to help you analyze the Fund's investment risks in light of its historical returns. The bar chart shows the variability of the Fund's IS 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 IS 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 Intermediate Government Fund, Inc. - IS Class
Bar Chart Closing [Text Block]	rr_BarChartClosingTextBlock	The Fund's IS class total return for the three-month period from January 1, 2013 to March 31, 2013, was 0.03%. Within the periods shown in the bar chart, the Fund's IS class highest quarterly return was 3.77% (quarter ended December 31, 2008). Its lowest quarterly return was (1.49)% (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 One Class of after Tax Shown [Text]	rr_PerformanceTableOneClassOfAfterTaxShown	After-tax returns are shown only for the IS class, and after-tax returns for the SS class will differ from those shown for the IS class.
Performance Table Narrative	rr_PerformanceTableNarrativeTextBlock	In addition to Return Before Taxes, Return After Taxes is shown for the Fund's IS class to illustrate the effect of federal taxes on Fund returns. After-tax returns are shown only for the IS class, and after-tax returns for the SS class will differ from those shown for the IS 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 Period Ended December 31, 2012)
Federated Intermediate Government Fund, Inc. | IS
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, as applicable)	rr_MaximumDeferredSalesChargeOverOther	none
Maximum Sales Charge (Load) Imposed on Reinvested Dividends (and other Distributions) (as a percentage of offering price)	rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther	none
Redemption Fee (as a percentage of amount redeemed, if applicable)	rr_RedemptionFeeOverRedemption	none
Exchange Fee	rr_ExchangeFeeOverRedemption	none
Management Fee	rr_ManagementFeesOverAssets	0.40%
Distribution (12b-1) Fee	rr_DistributionAndService12b1FeesOverAssets	none
Other Expenses	rr_OtherExpensesOverAssets	0.88%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.28%
Fee Waivers and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	0.98%	[1]
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements	rr_NetExpensesOverAssets	0.30%
1 Year	rr_ExpenseExampleYear01	130
3 Years	rr_ExpenseExampleYear03	406
5 Years	rr_ExpenseExampleYear05	702
10 Years	rr_ExpenseExampleYear10	1,545
2003	rr_AnnualReturn2003	1.84%
2004	rr_AnnualReturn2004	0.99%
2005	rr_AnnualReturn2005	1.26%
2006	rr_AnnualReturn2006	4.33%
2007	rr_AnnualReturn2007	6.74%
2008	rr_AnnualReturn2008	6.58%
2009	rr_AnnualReturn2009	2.37%
2010	rr_AnnualReturn2010	4.50%
2011	rr_AnnualReturn2011	4.76%
2012	rr_AnnualReturn2012	2.09%
Year to Date Return, Label	rr_YearToDateReturnLabel	The Fund's IS class total return for the three-month period
Bar Chart, Year to Date Return, Date	rr_BarChartYearToDateReturnDate	Mar. 31, 2013
Bar Chart, Year to Date Return	rr_BarChartYearToDateReturn	0.03%
Highest Quarterly Return, Label	rr_HighestQuarterlyReturnLabel	highest quarterly return
Highest Quarterly Return, Date	rr_BarChartHighestQuarterlyReturnDate	Dec. 31, 2008
Highest Quarterly Return	rr_BarChartHighestQuarterlyReturn	3.77%
Lowest Quarterly Return, Label	rr_LowestQuarterlyReturnLabel	lowest quarterly return
Lowest Quarterly Return, Date	rr_BarChartLowestQuarterlyReturnDate	Dec. 31, 2010
Lowest Quarterly Return	rr_BarChartLowestQuarterlyReturn	(1.49%)
1 Year	rr_AverageAnnualReturnYear01	2.09%
5 Years	rr_AverageAnnualReturnYear05	4.05%
10 Years	rr_AverageAnnualReturnYear10	3.53%
Federated Intermediate Government Fund, Inc. | SS
Risk/Return:	rr_RiskReturnAbstract
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice	none
Maximum Deferred Sales Charge (Load) (as a percentage of original purchase price or redemption proceeds, as applicable)	rr_MaximumDeferredSalesChargeOverOther	none
Maximum Sales Charge (Load) Imposed on Reinvested Dividends (and other Distributions) (as a percentage of offering price)	rr_MaximumSalesChargeOnReinvestedDividendsAndDistributionsOverOther	none
Redemption Fee (as a percentage of amount redeemed, if applicable)	rr_RedemptionFeeOverRedemption	none
Exchange Fee	rr_ExchangeFeeOverRedemption	none
Management Fee	rr_ManagementFeesOverAssets	0.40%
Distribution (12b-1) Fee	rr_DistributionAndService12b1FeesOverAssets	none	[2]
Other Expenses	rr_OtherExpensesOverAssets	1.13%
Total Annual Fund Operating Expenses	rr_ExpensesOverAssets	1.53%
Fee Waivers and/or Expense Reimbursements	rr_FeeWaiverOrReimbursementOverAssets	0.98%	[1]
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements	rr_NetExpensesOverAssets	0.55%
1 Year	rr_ExpenseExampleYear01	156
3 Years	rr_ExpenseExampleYear03	483
5 Years	rr_ExpenseExampleYear05	834
10 Years	rr_ExpenseExampleYear10	1,824
1 Year	rr_AverageAnnualReturnYear01	1.89%
5 Years	rr_AverageAnnualReturnYear05	3.84%
10 Years	rr_AverageAnnualReturnYear10	3.30%
Federated Intermediate Government Fund, Inc. | Return After Taxes on Distributions | IS
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	1.53%
5 Years	rr_AverageAnnualReturnYear05	3.23%
10 Years	rr_AverageAnnualReturnYear10	2.47%
Federated Intermediate Government Fund, Inc. | Return After Taxes on Distributions and Sale of Fund Shares | IS
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	1.35%
5 Years	rr_AverageAnnualReturnYear05	2.98%
10 Years	rr_AverageAnnualReturnYear10	2.38%
Federated Intermediate Government Fund, Inc. | Barclays Intermediate Government Index (reflects no deduction for fees, expenses or taxes)
Risk/Return:	rr_RiskReturnAbstract
1 Year	rr_AverageAnnualReturnYear01	1.73%	[3]
5 Years	rr_AverageAnnualReturnYear05	4.51%	[3]
10 Years	rr_AverageAnnualReturnYear10	4.10%	[3]

[1] Total Annual Fund Operating Expenses have been restated to reflect an anticipated decrease in Other Expenses. The Adviser and its affiliates have voluntarily agreed to waive their fees and/or reimburse expenses so that the total annual fund operating expenses (excluding Acquired Fund Fees and Expenses, if any) paid by the Fund's IS and SS classes (after the voluntary waivers and/or reimbursements) will not exceed 0.30% and 0.55% (the "Fee Limit"), respectively, up to but not including the later of (the "Termination Date"): (a) May 1, 2014; or (b) the date of the Fund's next effective Prospectus. While the Adviser and its affiliates currently do not anticipate terminating or increasing these arrangements prior to the Termination Date, these arrangements may only be terminated or the Fee Limit increased prior to the Termination Date with the agreement of the Fund's Board of Directors.

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

[3] Barclays Intermediate Government Index is an unmanaged index comprised of all publicly issued, non-convertible domestic debt of the U.S. government or any agency thereof, or any quasi-federal corporation and of corporate debt guaranteed by the U.S. government. Only notes and bonds with minimum outstanding principal of $1 million and minimum maturity of one year and maximum maturity of ten years are included.