XML 10 R9.htm IDEA: XBRL DOCUMENT v2.3.0.15
LabelElementValue
Risk/Return:rr_RiskReturnAbstract 
Document Typedei_DocumentTypeOther
Document Period End Datedei_DocumentPeriodEndDateOct. 12, 2011
Registrant Namedei_EntityRegistrantNameFIDELITY SUMMER STREET TRUST
Central Index Keydei_EntityCentralIndexKey0000225322
Amendment Flagdei_AmendmentFlagfalse
Document Creation Datedei_DocumentCreationDateOct. 12, 2011
Document Effective Datedei_DocumentEffectiveDateOct. 12, 2011
Prospectus Daterr_ProspectusDateOct. 12, 2011
Series | Fidelity Series Floating Rate High Income Fund
 
Risk/Return:rr_RiskReturnAbstract 
Risk/Return [Heading]rr_RiskReturnHeading
Fund Summary
Fund/Class:
Fidelity® Series Floating Rate High Income Fund/Fidelity Series Floating Rate High Income Fund
Objective [Heading]rr_ObjectiveHeadingInvestment Objective
Objective, Primary [Text Block]rr_ObjectivePrimaryTextBlockThe fund seeks a high level of current income.
Fee Tablefsst225322_FundFeesAndExpensesAbstract 
Expense [Heading]rr_ExpenseHeadingFee Table
Expense Narrative [Text Block]rr_ExpenseNarrativeTextBlockThe following table describes the fees and expenses that may be incurred when you buy and hold shares of the fund.
Shareholder feesrr_ShareholderFeesAbstract 
Shareholder Fees Caption [Text]rr_ShareholderFeesCaptionShareholder fees (fees paid directly from your investment)
Annual class operating expensesrr_OperatingExpensesAbstract 
Operating Expenses Caption [Text]rr_OperatingExpensesCaptionAnnual class operating expenses (expenses that you pay each year as a % of the value of your investment)
Other Expenses, New Fund, Based on Estimates [Text]rr_OtherExpensesNewFundBasedOnEstimatesBased on estimated amounts for the current fiscal year.
Expense Examplerr_ExpenseExampleAbstract 
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 mutual 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:

Portfolio Turnoverfsst225322_PortfolioTurnoverAltAbstract 
Portfolio Turnover [Heading]rr_PortfolioTurnoverHeadingPortfolio Turnover
Portfolio Turnover [Text Block]rr_PortfolioTurnoverTextBlockThe 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.
Strategy [Heading]rr_StrategyHeadingPrincipal Investment Strategies
Strategy Narrative [Text Block]rr_StrategyNarrativeTextBlock
  • Normally investing at least 80% of assets in floating rate loans, which are often lower-quality debt securities, and other floating rate securities.
  • Investing in companies in troubled or uncertain financial condition.
  • Investing in money market and investment-grade debt securities, and repurchase agreements.
  • Investing in domestic and foreign issuers.
  • Using fundamental analysis of each issuer's financial condition and industry position and market and economic conditions to select investments.
Risk [Heading]rr_RiskHeadingPrincipal Investment Risks
Risk Narrative [Text Block]rr_RiskNarrativeTextBlock
  • 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. Lower-quality debt securities (those of less than investment-grade quality), including floating rate loans, involve greater risk of default on interest and principal payments or price changes due to changes in the credit quality of the issuer. The value of lower-quality debt securities, including floating rate loans, can be more volatile due to increased sensitivity to adverse issuer, political, regulatory, market, or economic developments.
  • Impairment of Collateral. A floating rate loan may not be fully collateralized which may cause the floating rate loan to decline significantly in value.
  • Floating Rate Loan Liquidity. Floating rate loans generally are subject to restrictions on resale. Floating rate loans sometimes trade infrequently in the secondary market. As a result, valuing a floating rate loan can be more difficult, and buying and selling a floating rate loan at an acceptable price can be more difficult or delayed. Difficulty in selling a floating rate loan can result in a loss.
  • Prepayment. The ability of an issuer of a debt security to repay principal prior to a security's maturity can limit the potential for gains when the credit quality of the issuer improves.
  • 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.

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. You could lose money by investing in the fund.

Risk Not Insured Depository Institution [Text]rr_RiskNotInsuredDepositoryInstitutionAn 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.
Risk Lose Money [Text]rr_RiskLoseMoneyYou could lose money by investing in the fund.
Performancefsst225322_FundPastPerformanceAbstract 
Bar Chart and Performance Table [Heading]rr_BarChartAndPerformanceTableHeadingPerformance
Performance One Year or Less [Text]rr_PerformanceOneYearOrLessPerformance history will be available for the fund after the fund has been in operation for one calendar year.
Series | Fidelity Series Floating Rate High Income Fund | Class: Series
 
Shareholder feesrr_ShareholderFeesAbstract 
Shareholder fees (fees paid directly from your investment)rr_ShareholderFeeOther none
Annual class operating expensesrr_OperatingExpensesAbstract 
Management feerr_ManagementFeesOverAssets0.57%
Distribution and/or Service (12b-1) feesrr_DistributionAndService12b1FeesOverAssets none
Other expensesrr_OtherExpensesOverAssets0.20%[1]
Total annual operating expensesrr_ExpensesOverAssets0.77%
Expense Examplerr_ExpenseExampleAbstract 
1 yearrr_ExpenseExampleYear0179
3 yearsrr_ExpenseExampleYear03246
F | Fidelity Series Floating Rate High Income Fund
 
Risk/Return:rr_RiskReturnAbstract 
Risk/Return [Heading]rr_RiskReturnHeading
Fund Summary
Fund/Class:
Fidelity® Series Floating Rate High Income Fund/F
Objective [Heading]rr_ObjectiveHeadingInvestment Objective
Objective, Primary [Text Block]rr_ObjectivePrimaryTextBlockThe fund seeks a high level of current income.
Fee Tablefsst225322_FundFeesAndExpensesAbstract 
Expense [Heading]rr_ExpenseHeadingFee Table
Expense Narrative [Text Block]rr_ExpenseNarrativeTextBlockThe following table describes the fees and expenses that may be incurred when you buy and hold shares of the fund.
Shareholder feesrr_ShareholderFeesAbstract 
Shareholder Fees Caption [Text]rr_ShareholderFeesCaptionShareholder fees (fees paid directly from your investment)
Annual class operating expensesrr_OperatingExpensesAbstract 
Operating Expenses Caption [Text]rr_OperatingExpensesCaptionAnnual class operating expenses (expenses that you pay each year as a % of the value of your investment)
Other Expenses, New Fund, Based on Estimates [Text]rr_OtherExpensesNewFundBasedOnEstimatesBased on estimated amounts for the current fiscal year.
Expense Examplerr_ExpenseExampleAbstract 
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 mutual 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:

Portfolio Turnoverfsst225322_PortfolioTurnoverAltAbstract 
Portfolio Turnover [Heading]rr_PortfolioTurnoverHeadingPortfolio Turnover
Portfolio Turnover [Text Block]rr_PortfolioTurnoverTextBlockThe 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.
Strategy [Heading]rr_StrategyHeadingPrincipal Investment Strategies
Strategy Narrative [Text Block]rr_StrategyNarrativeTextBlock
  • Normally investing at least 80% of assets in floating rate loans, which are often lower-quality debt securities, and other floating rate securities.
  • Investing in companies in troubled or uncertain financial condition.
  • Investing in money market and investment-grade debt securities, and repurchase agreements.
  • Investing in domestic and foreign issuers.
  • Using fundamental analysis of each issuer's financial condition and industry position and market and economic conditions to select investments.
Risk [Heading]rr_RiskHeadingPrincipal Investment Risks
Risk Narrative [Text Block]rr_RiskNarrativeTextBlock
  • 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. Lower-quality debt securities (those of less than investment-grade quality), including floating rate loans, involve greater risk of default on interest and principal payments or price changes due to changes in the credit quality of the issuer. The value of lower-quality debt securities, including floating rate loans, can be more volatile due to increased sensitivity to adverse issuer, political, regulatory, market, or economic developments.
  • Impairment of Collateral. A floating rate loan may not be fully collateralized which may cause the floating rate loan to decline significantly in value.
  • Floating Rate Loan Liquidity. Floating rate loans generally are subject to restrictions on resale. Floating rate loans sometimes trade infrequently in the secondary market. As a result, valuing a floating rate loan can be more difficult, and buying and selling a floating rate loan at an acceptable price can be more difficult or delayed. Difficulty in selling a floating rate loan can result in a loss.
  • Prepayment. The ability of an issuer of a debt security to repay principal prior to a security's maturity can limit the potential for gains when the credit quality of the issuer improves.
  • 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.

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. You could lose money by investing in the fund.

Risk Not Insured Depository Institution [Text]rr_RiskNotInsuredDepositoryInstitutionAn 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.
Risk Lose Money [Text]rr_RiskLoseMoneyYou could lose money by investing in the fund.
Performancefsst225322_FundPastPerformanceAbstract 
Bar Chart and Performance Table [Heading]rr_BarChartAndPerformanceTableHeadingPerformance
Performance One Year or Less [Text]rr_PerformanceOneYearOrLessPerformance history will be available for the fund after the fund has been in operation for one calendar year.
F | Fidelity Series Floating Rate High Income Fund | Class F
 
Shareholder feesrr_ShareholderFeesAbstract 
Shareholder fees (fees paid directly from your investment)rr_ShareholderFeeOther none
Annual class operating expensesrr_OperatingExpensesAbstract 
Management feerr_ManagementFeesOverAssets0.57%
Distribution and/or Service (12b-1) feesrr_DistributionAndService12b1FeesOverAssets none
Other expensesrr_OtherExpensesOverAssets0.06%[1]
Total annual operating expensesrr_ExpensesOverAssets0.63%
Expense Examplerr_ExpenseExampleAbstract 
1 yearrr_ExpenseExampleYear0164
3 yearsrr_ExpenseExampleYear03 202
[1]Based on estimated amounts for the current fiscal year.