XML 138 R15.htm IDEA: XBRL DOCUMENT v2.4.0.8
Label Element Value
Risk/Return: rr_RiskReturnAbstract  
Registrant Name dei_EntityRegistrantName FIDELITY INCOME FUND /MA/
Prospectus Date rr_ProspectusDate Sep. 28, 2013
Inst | Fidelity Ultra-Short Bond Fund
  
Risk/Return: rr_RiskReturnAbstract  
Risk/Return [Heading] rr_RiskReturnHeading Fund Summary

Fund/Class:
Fidelity® Ultra-Short Bond Fund/Fidelity Advisor® Ultra-Short Bond Fund Institutional
Objective [Heading] rr_ObjectiveHeading Investment Objective
Objective, Primary [Text Block] rr_ObjectivePrimaryTextBlock The fund seeks to obtain a high level of current income consistent with preservation of capital.
Expense [Heading] rr_ExpenseHeading Fee Table
Expense Narrative [Text Block] rr_ExpenseNarrativeTextBlock The following table describes the fees and expenses that may be incurred when you buy and hold shares of the fund.
Shareholder Fees Caption [Text] rr_ShareholderFeesCaption Shareholder fees
(fees paid directly from your investment)
Operating Expenses Caption [Text] rr_OperatingExpensesCaption Annual class operating expenses
(expenses that you pay each year as a % of the value of your investment)
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 operating expenses or in the example, affect the fund's performance. During the most recent fiscal year, the fund's portfolio turnover rate was 67% of the average value of its portfolio.
Portfolio Turnover, Rate rr_PortfolioTurnoverRate 67.00%
Expense Example Narrative [Text Block] rr_ExpenseExampleNarrativeTextBlock This example helps compare the cost of investing in the fund with the cost of investing in other funds.

Let's say, hypothetically, that the annual return for shares of the fund is 5% and that your shareholder fees and the annual operating expenses for shares of the fund are exactly as described in the fee table. This example illustrates the effect of fees and expenses, but is not meant to suggest actual or expected fees and expenses or returns, all of which may vary. For every $10,000 you invested, here's how much you would pay in total expenses if you sell all of your shares at the end of each time period indicated:
Strategy [Heading] rr_StrategyHeading Principal Investment Strategies
Strategy Narrative [Text Block] rr_StrategyNarrativeTextBlock
  • Normally investing at least 80% of assets in investment-grade debt securities (those of medium and high quality) of all types, and repurchase agreements for those securities.
  • Normally investing in U.S. dollar-denominated money market and investment-grade debt securities and repurchase agreements.
  • Managing the fund to have similar overall interest rate risk to the Barclays® 6 Month Swap Index.
  • Normally maintaining a dollar-weighted average maturity of two years or less.
  • Allocating assets across different market sectors and maturities.
  • Investing more than 25% of total assets in the financial services industries.
  • Investing in domestic and foreign issuers.
  • Analyzing the credit quality of the issuer, security-specific features, current and potential future valuation, and trading opportunities to select investments.
  • Engaging in transactions that have a leveraging effect on the fund, including investments in derivatives - such as swaps (interest rate, total return, and credit default), options, and futures contracts - and forward-settling securities, to adjust the fund's risk exposure.
Strategy Portfolio Concentration [Text] rr_StrategyPortfolioConcentration
  • Investing more than 25% of total assets in the financial services industries.
Risk [Heading] rr_RiskHeading Principal Investment Risks
Risk Narrative [Text Block] rr_RiskNarrativeTextBlock
  • Interest Rate Changes. Interest rate increases can cause the price of a debt security to decrease.
  • Foreign Exposure. Foreign markets can be more volatile than the U.S. market due to increased risks of adverse issuer, political, regulatory, market, or economic developments and can perform differently from the U.S. market.
  • Financial Services Exposure. Changes in government regulation and interest rates and economic downturns can have a significant negative effect on issuers in the financial services sector.
  • Prepayment. The ability of an issuer of a debt security to repay principal prior to a security's maturity can cause greater price volatility if interest rates change.
  • Issuer-Specific Changes. The value of an individual security or particular type of security can be more volatile than, and can perform differently from, the market as a whole.
  • Leverage Risk. Leverage can increase market exposure, magnify investment risks, and cause losses to be realized more quickly.
An investment in the fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. Unlike individual debt securities, which typically pay principal at maturity, the value of an investment in the fund will fluctuate. You could lose money by investing in the fund.
Risk Lose Money [Text] rr_RiskLoseMoney You could lose money by investing in the fund.
Risk Not Insured Depository Institution [Text] rr_RiskNotInsuredDepositoryInstitution An investment in the fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.
Bar Chart and Performance Table [Heading] rr_BarChartAndPerformanceTableHeading Performance
Performance Narrative [Text Block] rr_PerformanceNarrativeTextBlock The following information is intended to help you understand the risks of investing in the fund. The information illustrates the changes in the performance of the fund's shares from year to year and compares the performance of the fund's shares to the performance of a securities market index over various periods of time. The index description appears in the Additional Index Information section of the prospectus. Past performance (before and after taxes) is not an indication of future performance.

Visit www.advisor.fidelity.com for updated return information.
Performance Information Illustrates Variability of Returns [Text] rr_PerformanceInformationIllustratesVariabilityOfReturns The information illustrates the changes in the performance of the fund's shares from year to year and compares the performance of the fund's shares to the performance of a securities market index over various periods of time.
Performance Availability Website Address [Text] rr_PerformanceAvailabilityWebSiteAddress www.advisor.fidelity.com
Performance Past Does Not Indicate Future [Text] rr_PerformancePastDoesNotIndicateFuture Past performance (before and after taxes) is not an indication of future performance.
Bar Chart [Heading] rr_BarChartHeading Year-by-Year Returns
Calendar Years
Bar Chart Closing [Text Block] rr_BarChartClosingTextBlock
During the periods shown in the chart:
Returns
Quarter ended
Highest Quarter Return
1.41%
September 30, 2006
Lowest Quarter Return
-6.95%
March 31, 2008
Year-to-Date Return
-0.02%
June 30, 2013
Performance Table Heading rr_PerformanceTableHeading Average Annual Returns
Performance Table Uses Highest Federal Rate rr_PerformanceTableUsesHighestFederalRate After-tax returns are calculated using the historical highest individual federal marginal income tax rates, but do not reflect the impact of state or local taxes.
Performance Table Not Relevant to Tax Deferred rr_PerformanceTableNotRelevantToTaxDeferred The after-tax returns shown are not relevant if you hold your shares in a retirement account or in another tax-deferred arrangement.
Performance Table Explanation after Tax Higher rr_PerformanceTableExplanationAfterTaxHigher Return After Taxes on Distributions and Sale of Fund Shares may be higher than other returns for the same period due to a tax benefit of realizing a capital loss upon the sale of fund shares.
Performance Table Narrative rr_PerformanceTableNarrativeTextBlock After-tax returns are calculated using the historical highest individual federal marginal income tax rates, but do not reflect the impact of state or local taxes. Actual after-tax returns may differ depending on your individual circumstances. The after-tax returns shown are not relevant if you hold your shares in a retirement account or in another tax-deferred arrangement. Return After Taxes on Distributions and Sale of Fund Shares may be higher than other returns for the same period due to a tax benefit of realizing a capital loss upon the sale of fund shares.

For the periods ended
December 31, 2012
Inst | Fidelity Ultra-Short Bond Fund | Institutional Class
  
Risk/Return: rr_RiskReturnAbstract  
Redemption fee on shares held less than 60 days (as a % of amount redeemed) rr_RedemptionFeeOverRedemption 0.25%
Management fee rr_ManagementFeesOverAssets 0.31%
Distribution and/or Service (12b-1) fees rr_DistributionAndService12b1FeesOverAssets none
Other expenses rr_OtherExpensesOverAssets 0.20%
Total annual operating expenses rr_ExpensesOverAssets 0.51%
1 year rr_ExpenseExampleYear01 $ 52
3 years rr_ExpenseExampleYear03 164
5 years rr_ExpenseExampleYear05 285
10 years rr_ExpenseExampleYear10 $ 640
2005 rr_AnnualReturn2005 2.92%
2006 rr_AnnualReturn2006 4.86%
2007 rr_AnnualReturn2007 (5.12%)
2008 rr_AnnualReturn2008 (7.91%)
2009 rr_AnnualReturn2009 0.87%
2010 rr_AnnualReturn2010 1.09%
2011 rr_AnnualReturn2011 0.02%
2012 rr_AnnualReturn2012 1.57%
Year to Date Return, Label rr_YearToDateReturnLabel Year-to-Date Return
Bar Chart, Year to Date Return, Date rr_BarChartYearToDateReturnDate Jun. 30, 2013
Bar Chart, Year to Date Return rr_BarChartYearToDateReturn (0.02%)
Highest Quarterly Return, Label rr_HighestQuarterlyReturnLabel Highest Quarter Return
Highest Quarterly Return, Date rr_BarChartHighestQuarterlyReturnDate Sep. 30, 2006
Highest Quarterly Return rr_BarChartHighestQuarterlyReturn 1.41%
Lowest Quarterly Return, Label rr_LowestQuarterlyReturnLabel Lowest Quarter Return
Lowest Quarterly Return, Date rr_BarChartLowestQuarterlyReturnDate Mar. 31, 2008
Lowest Quarterly Return rr_BarChartLowestQuarterlyReturn (6.95%)
Inst | Fidelity Ultra-Short Bond Fund | Return Before Taxes | Institutional Class
  
Risk/Return: rr_RiskReturnAbstract  
Column rr_AverageAnnualReturnColumnName Institutional Class
Label rr_AverageAnnualReturnLabel Return Before Taxes
Past 1 year rr_AverageAnnualReturnYear01 1.57%
Past 5 years rr_AverageAnnualReturnYear05 (0.94%)
Life of class rr_AverageAnnualReturnSinceInception (0.16%) [1]
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 16, 2004
Inst | Fidelity Ultra-Short Bond Fund | Return After Taxes on Distributions | Institutional Class
  
Risk/Return: rr_RiskReturnAbstract  
Column rr_AverageAnnualReturnColumnName Institutional Class
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions
Past 1 year rr_AverageAnnualReturnYear01 1.41%
Past 5 years rr_AverageAnnualReturnYear05 (1.20%)
Life of class rr_AverageAnnualReturnSinceInception (0.89%) [1]
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 16, 2004
Inst | Fidelity Ultra-Short Bond Fund | Return After Taxes on Distributions and Sale of Fund Shares | Institutional Class
  
Risk/Return: rr_RiskReturnAbstract  
Column rr_AverageAnnualReturnColumnName Institutional Class
Label rr_AverageAnnualReturnLabel Return After Taxes on Distributions and Sale of Fund Shares
Past 1 year rr_AverageAnnualReturnYear01 1.02%
Past 5 years rr_AverageAnnualReturnYear05 (0.94%)
Life of class rr_AverageAnnualReturnSinceInception (0.54%) [1]
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 16, 2004
Inst | Fidelity Ultra-Short Bond Fund | Barclays® 6 Month Swap Index (reflects no deduction for fees, expenses, or taxes)
  
Risk/Return: rr_RiskReturnAbstract  
Label rr_AverageAnnualReturnLabel Barclays® 6 Month Swap Index
Past 1 year rr_AverageAnnualReturnYear01 0.46%
Past 5 years rr_AverageAnnualReturnYear05 1.33%
Life of class rr_AverageAnnualReturnSinceInception 2.45% [1]
Inception Date rr_AverageAnnualReturnInceptionDate Jun. 16, 2004
[1] From June 16, 2004.