485BPOS

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
FORM N-1A
REGISTRATION STATEMENT (No. 002-58542)
		UNDER THE SECURITIES ACT OF 1933	[X]
		Pre-Effective Amendment No. ____	[ ]
		Post-Effective Amendment No. 108	[X]
and
REGISTRATION STATEMENT (No. 811-02737)
		UNDER THE INVESTMENT COMPANY ACT OF 1940	[X]
		Amendment No. 108	[X]
Fidelity Summer Street Trust
(Exact Name of Registrant as Specified in Charter)
245 Summer Street, Boston, Massachusetts 02210
(Address Of Principal Executive Offices) (Zip Code)
Registrant's Telephone Number: 617-563-7000
Scott C. Goebel, Secretary
245 Summer Street
Boston, Massachusetts 02210
(Name and Address of Agent for Service)
It is proposed that this filing will become effective
	( X )	immediately upon filing pursuant to paragraph (b).
	( )	on ( ) pursuant to paragraph (b) at 5:30 p.m. Eastern Time.
	( )	60 days after filing pursuant to paragraph (a)(1) at 5:30 p.m. Eastern Time.
	( )	on ( ) pursuant to paragraph (a)(1) of Rule 485 at 5:30 p.m. Eastern Time.
	( )	75 days after filing pursuant to paragraph (a)(2) at 5:30 p.m. Eastern Time.
	( )	on ( ) pursuant to paragraph (a)(2) of Rule 485 at 5:30 p.m. Eastern Time.
If appropriate, check the following box:
	( )	this post-effective amendment designates a new effective date for a previously filed post-effective amendment.

EXHIBIT INDEX

Exhibit	Exhibit No.
XBRL Instance Document	EX-101.INS
XBRL Taxonomy Extension Schema Document	EX-101.SCH
XBRL Taxonomy Extension Calculation Linkbase Document	EX-101.CAL
XBRL Taxonomy Extension Definition Linkbase Document	EX-101.DEF
XBRL Taxonomy Extension Labels Linkbase Document	EX-101.LAB
XBRL Taxonomy Extension Presentation Linkbase Document	EX-101.PRE

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933 and the Investment Company Act of 1940, the Registrant certifies that it meets all of the requirements for the effectiveness of this Registration Statement pursuant to Rule 485(b) under the Securities Act of 1933 and has duly caused this Post-Effective Amendment No. 108 to the Registration Statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Boston, and Commonwealth of Massachusetts, on the 17th day of July 2013.

	Fidelity Summer Street Trust
	By	/s/Kenneth B. Robins
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||		Kenneth B. Robins, President

Pursuant to the requirements of the Securities Act of 1933, this Registration Statement has been signed below by the following persons in the capacities and on the dates indicated.

(Signature)		(Title)	(Date)
/s/Kenneth B. Robins		President and Treasurer	July 17, 2013
Kenneth B. Robins		(Principal Executive Officer)
/s/Christine Reynolds		Chief Financial Officer	July 17, 2013
Christine Reynolds		(Principal Financial Officer)
/s/James C. Curvey	*	Trustee	July 17, 2013
James C. Curvey
/s/Dennis J. Dirks	*	Trustee	July 17, 2013
Dennis J. Dirks
/s/Alan J. Lacy	*	Trustee	July 17, 2013
Alan J. Lacy
/s/Ned C. Lautenbach	*	Trustee	July 17, 2013
Ned C. Lautenbach
/s/Joseph Mauriello	*	Trustee	July 17, 2013
Joseph Mauriello
/s/Ronald P. O'Hanley	*	Trustee	July 17, 2013
Ronald P. O'Hanley
/s/Robert W. Selander	*	Trustee	July 17, 2013
Robert W. Selander
/s/Cornelia M. Small	*	Trustee	July 17, 2013
Cornelia M. Small
/s/William S. Stavropoulos	*	Trustee	July 17, 2013
William S. Stavropoulos
/s/David M. Thomas	*	Trustee	July 17, 2013
David M. Thomas
/s/Michael E. Wiley	*	Trustee	July 17, 2013
Michael E. Wiley

*	By:	/s/Joseph R. Fleming
		Joseph R. Fleming, pursuant to a power of attorney dated December 1, 2011 and filed herewith.

POWER OF ATTORNEY

We, the undersigned Directors or Trustees, as the case may be, of the following investment companies:

Fidelity Advisor Series I Fidelity Advisor Series VII Fidelity Advisor Series VIII Fidelity Beacon Street Trust Fidelity Capital Trust Fidelity Central Investment Portfolios LLC Fidelity Commonwealth Trust Fidelity Concord Street Trust Fidelity Congress Street Fund Fidelity Contrafund Fidelity Covington Trust Fidelity Destiny Portfolios Fidelity Devonshire Trust Fidelity Exchange Fund Fidelity Financial Trust Fidelity Hanover Street Trust Fidelity Hastings Street Trust Fidelity Investment Trust Fidelity Magellan Fund Fidelity Mt. Vernon Street Trust Fidelity Puritan Trust Fidelity Securities Fund Fidelity Select Portfolios Fidelity Summer Street Trust Fidelity Trend Fund Variable Insurance Products Fund Variable Insurance Products Fund II Variable Insurance Products Fund III Variable Insurance Products Fund IV

in addition to any other investment company for which Fidelity Management & Research Company ("FMR") or an affiliate acts as investment adviser and for which the undersigned individuals serve as Directors or Trustees (collectively, the "Funds"), hereby revoke all previous powers of attorney we have given to sign and otherwise act in our names and behalf in matters involving any investment company for which FMR or an affiliate acts as investment adviser and hereby constitute and appoint Thomas C. Bogle, Joseph R. Fleming, John V. O'Hanlon, Robert W. Helm and Anthony H. Zacharski, each of them singly, our true and lawful attorneys-in-fact, with full power of substitution, and with full power to each of them, to sign for us and in our names in the appropriate capacities, all Registration Statements of the Funds on Form N-1A, or any successors thereto, any and all subsequent Amendments, Pre-Effective Amendments, or Post-Effective Amendments to said Registration Statements or any successors thereto, and any supplements or other instruments in connection therewith, and generally to do all such things in our names and behalf in connection therewith as said attorneys-in-fact deem necessary or appropriate, to comply with the provisions of the Securities Act of 1933 and the Investment Company Act of 1940, and all related requirements of the Securities and Exchange Commission. We hereby ratify and confirm all that said attorneys-in-fact or their substitutes may do or cause to be done by virtue hereof. This power of attorney is effective for all documents filed on or after December 1, 2011.

WITNESS our hands on this first day of December 1, 2011.

/s/James C. Curvey	/s/Robert W. Selander
James C. Curvey	Robert W. Selander
/s/Ronald P. O'Hanley	/s/Cornelia M. Small
Ronald P. O'Hanley	Cornelia M. Small
/s/Dennis J. Dirks	/s/William S. Stavropoulos
Dennis J. Dirks	William S. Stavropoulos
/s/Alan J. Lacy	/s/David M. Thomas
Alan J. Lacy	David M. Thomas
/s/Ned C. Lautenbach	/s/Michael E. Wiley
Ned C. Lautenbach	Michael E. Wiley
/s/Joseph Mauriello
Joseph Mauriello

XML

Inst | Fidelity Global High Income Fund

Fund Summary

Fund/Class:
Fidelity^® Global High Income Fund/Fidelity Advisor^® Global High Income Fund Institutional

Investment Objective

The fund seeks a high level of current income. Growth of capital may also be considered.

Fee Table

The following table describes the fees and expenses that may be incurred when you buy, hold, or sell shares of the fund.

Shareholder fees
(fees paid directly from your investment)

Shareholder Fees	Inst Fidelity Global High Income Fund Institutional Class
Redemption fee on shares held less than 90 days (as a % of amount redeemed)	1.00%

Annual class operating expenses
(expenses that you pay each year as a % of the value of your investment)

Annual Class Operating Expenses	Inst Fidelity Global High Income Fund Institutional Class
Management fee	0.72%
Distribution and/or Service (12b-1) fees	none
Other expenses	0.26%
Total annual operating expenses	0.98%

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:

Expense Example (USD $)	Inst Fidelity Global High Income Fund Institutional Class
1 year	100
3 years	312
5 years	542
10 years	1,201

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 operating expenses or in the example, affect the fund's performance. During the most recent fiscal year, the fund's portfolio turnover rate was 55% of the average value of its portfolio.

Principal Investment Strategies

• Normally investing primarily in income producing debt securities, preferred stocks, and convertible securities, with an emphasis on lower-quality debt securities, of U.S. and non-U.S. issuers, including emerging market countries.
• Potentially investing in non-income producing securities, including defaulted securities and common stocks.
• Investing in companies in troubled or uncertain financial condition.
• Allocating investments across different countries and regions.
• Investing in securities issued throughout the world, including potentially significant investments in U.S. issuers.
• Using a base neutral mix of approximately 60% U.S. high yield, 20% emerging markets debt, 15% European high yield, and 5% Asian high yield.
• Adjusting allocation among markets within the following ranges: U.S. high yield (40%-80%); emerging markets debt (5%-35%); European high yield (0%-30%); and Asian high yield (0%-10%).
• Analyzing an issuer using fundamental factors (e.g., financial condition, earnings outlook, and strategy) and evaluating each security's current price relative to estimated long-term value to select investments.

Principal Investment Risks

• Stock Market Volatility. Stock markets are volatile and can decline significantly in response to adverse issuer, political, regulatory, market, or economic developments. Different parts of the market, including different market sectors, and different types of securities can react differently to these developments.
• Interest Rate Changes. Interest rate increases can cause the price of a debt security to decrease.
• Foreign Exposure. Foreign markets, particularly emerging 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. Emerging markets can be subject to greater social, economic, regulatory, and political uncertainties and can be extremely volatile. Foreign exchange rates also can be extremely volatile.
• 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, also referred to as high yield debt securities) and certain types of other securities involve greater risk of default or price changes due to changes in the credit quality of the issuer. The value of lower-quality debt securities and certain types of other securities can be more volatile due to increased sensitivity to adverse issuer, political, regulatory, market, or economic developments and can be difficult to resell.

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.

Performance

The following information is intended to help you understand the risks of investing in the fund. The information illustrates the performance of the fund's shares over the past year and compares the performance of the fund's shares to the performance of a securities market index and a hypothetical composite of market indexes over various periods of time. The indexes have characteristics relevant to the fund's investment strategies. Index descriptions appear in the Additional Information about the Indexes 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.

Year-by-Year Returns
Calendar Year

During the period shown in the chart:	Returns	Quarter ended
Highest Quarter Return	5.94%	March 31, 2012
Lowest Quarter Return	0.81%	June 30, 2012
Year-to-Date Return	1.49%	March 31, 2013

Average Annual Returns

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.

For the periods ended
December 31, 2012

Average Annual Total Returns Inst Fidelity Global High Income Fund	Past 1 year	Life of class		Inception Date
Institutional Class Return Before Taxes	16.92%	6.82%	[1]	May 11, 2011
Institutional Class Return After Taxes on Distributions	14.68%	4.89%	[1]	May 11, 2011
Institutional Class Return After Taxes on Distributions and Sale of Fund Shares	10.91%	4.64%	[1]	May 11, 2011
The BofA Merrill Lynch℠ Global High Yield and Emerging Markets Plus Index (reflects no deduction for fees, expenses, or taxes)	19.74%	9.89%	[1]	May 11, 2011
Fidelity Global High Income Composite Index℠ (reflects no deduction for fees, expenses, or taxes)	18.79%	9.01%	[1]	May 11, 2011

[1] From May 11, 2011.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

FIDELITY SUMMER STREET TRUST

Prospectus Date

rr_ProspectusDate

Jun. 29, 2013

Fidelity Capital & Income Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

Fund Summary

Fund:
Fidelity^®Capital & Income Fund

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The fund seeks to provide a combination of income and capital growth.

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 fund 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 60% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

60.00%

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 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:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

• Investing in equity and debt securities, including defaulted securities, with an emphasis on lower-quality debt securities.
• Investing in companies in troubled or uncertain financial condition.
• 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_RiskHeading

Principal Investment Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

• Stock Market Volatility. Stock markets are volatile and can decline significantly in response to adverse issuer, political, regulatory, market, or economic developments. Different parts of the market, including different market sectors, and different types of securities can react differently to these developments.
• Interest Rate Changes. Interest rate increases can cause the price of a debt security to decrease.
• Foreign Exposure. Foreign markets, particularly emerging 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.
• 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, also referred to as high yield debt securities) and certain types of other securities involve greater risk of default or price changes due to changes in the credit quality of the issuer. The value of lower-quality debt securities and certain types of other securities can be more volatile due to increased sensitivity to adverse issuer, political, regulatory, market, or economic developments and can be difficult to resell.

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 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 Information about the Indexes section of the prospectus. Past performance (before and after taxes) is not an indication of future performance.

Visit www.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.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	26.67%	June 30, 2009
Lowest Quarter Return	-23.09%	December 31, 2008
Year-to-Date Return	3.62%	March 31, 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 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.

For the periods ended
December 31, 2012

Fidelity Capital & Income Fund | Class: Fidelity Capital & Income Fund

Risk/Return:

rr_RiskReturnAbstract

Redemption fee on shares held less than 90 days (as a % of amount redeemed)

rr_RedemptionFeeOverRedemption

1.00%

Management fee

rr_ManagementFeesOverAssets

0.57%

Distribution and/or Service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.16%

Total annual fund operating expenses

rr_ExpensesOverAssets

0.73%

1 year

rr_ExpenseExampleYear01

$ 75

3 years

rr_ExpenseExampleYear03

233

5 years

rr_ExpenseExampleYear05

406

10 years

rr_ExpenseExampleYear10

$ 906

2003

rr_AnnualReturn2003

39.13%

2004

rr_AnnualReturn2004

12.57%

2005

rr_AnnualReturn2005

5.04%

2006

rr_AnnualReturn2006

13.04%

2007

rr_AnnualReturn2007

3.82%

2008

rr_AnnualReturn2008

(31.90%)

2009

rr_AnnualReturn2009

72.14%

2010

rr_AnnualReturn2010

17.13%

2011

rr_AnnualReturn2011

(1.91%)

2012

rr_AnnualReturn2012

16.41%

Year to Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date Return

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2013

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

3.62%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter Return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

26.67%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter Return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(23.09%)

Fidelity Capital & Income Fund | Return Before Taxes | Class: Fidelity Capital & Income Fund

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity Capital & Income Fund

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

Past 1 year

rr_AverageAnnualReturnYear01

16.41%

Past 5 years

rr_AverageAnnualReturnYear05

9.41%

Past 10 years

rr_AverageAnnualReturnYear10

11.71%

Fidelity Capital & Income Fund | Return After Taxes on Distributions | Class: Fidelity Capital & Income Fund

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity Capital & Income Fund

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

Past 1 year

rr_AverageAnnualReturnYear01

13.98%

Past 5 years

rr_AverageAnnualReturnYear05

6.72%

Past 10 years

rr_AverageAnnualReturnYear10

9.05%

Fidelity Capital & Income Fund | Return After Taxes on Distributions and Sale of Fund Shares | Class: Fidelity Capital & Income Fund

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity Capital & Income Fund

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

Past 1 year

rr_AverageAnnualReturnYear01

10.58%

Past 5 years

rr_AverageAnnualReturnYear05

6.41%

Past 10 years

rr_AverageAnnualReturnYear10

8.61%

Fidelity Capital & Income Fund | The BofA Merrill Lynch℠ US High Yield Constrained Index (reflects no deduction for fees, expenses, or taxes)

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

The BofA Merrill Lynch^SM US High Yield Constrained Index

Past 1 year

rr_AverageAnnualReturnYear01

15.55%

Past 5 years

rr_AverageAnnualReturnYear05

10.14%

Past 10 years

rr_AverageAnnualReturnYear10

10.38%

XML

Fidelity Focused High Income Fund

Fund Summary

Fund:
Fidelity^®Focused High Income Fund

Investment Objective

The fund seeks a high level of income. The fund may also seek capital appreciation.

Fee Table

The following table describes the fees and expenses that may be incurred when you buy and hold shares of the fund.

Shareholder fees
(fees paid directly from your investment)

Shareholder Fees	Fidelity Focused High Income Fund Class: Fidelity Focused High Income Fund
Redemption fee on shares held less than 90 days (as a % of amount redeemed)	1.00%

Annual fund operating expenses
(expenses that you pay each year as a % of the value of your investment)

Annual Fund Operating Expenses	Fidelity Focused High Income Fund Class: Fidelity Focused High Income Fund
Management fee	0.56%
Distribution and/or Service (12b-1) fees	none
Other expenses	0.25%
Total annual fund operating expenses	0.81%

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:

Expense Example (USD $)	Fidelity Focused High Income Fund Class: Fidelity Focused High Income Fund
1 year	83
3 years	259
5 years	450
10 years	1,002

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 operating expenses or in the example, affect the fund's performance. During the most recent fiscal year, the fund's portfolio turnover rate was 47% of the average value of its portfolio.

Principal Investment Strategies

• Normally investing primarily in income producing debt securities, preferred stocks, and convertible securities, with an emphasis on lower-quality debt securities.
• Normally investing primarily in securities rated BB by Standard & Poor's (S&P), Ba by Moody's Investors Service (Moody's), comparably rated by at least one nationally recognized credit rating agency, or, if unrated, considered by Fidelity Management & Research Company (FMR) to be of comparable quality.
• Potentially investing in securities that have a higher or lower credit quality.
• Potentially investing in non-income producing securities, including defaulted securities and common stocks.
• Investing in companies in troubled or uncertain financial condition.
• 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.

Principal Investment Risks

• Stock Market Volatility. Stock markets are volatile and can decline significantly in response to adverse issuer, political, regulatory, market, or economic developments. Different parts of the market, including different market sectors, and different types of securities can react differently to these developments.
• Interest Rate Changes. Interest rate increases can cause the price of a debt security to decrease.
• Foreign Exposure. Foreign markets, particularly emerging 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.
• 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, also referred to as high yield debt securities) and certain types of other securities involve greater risk of default or price changes due to changes in the credit quality of the issuer. The value of lower-quality debt securities and certain types of other securities can be more volatile due to increased sensitivity to adverse issuer, political, regulatory, market, or economic developments and can be difficult to resell.

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.

Performance

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 Information about the Indexes section of the prospectus. Past performance (before and after taxes) is not an indication of future performance.

Visit www.fidelity.com for updated return information.

Year-by-Year Returns
Calendar Years

During the periods shown in the chart:	Returns	Quarter ended
Highest Quarter Return	10.91%	June 30, 2009
Lowest Quarter Return	-14.61%	December 31, 2008
Year-to-Date Return	1.77%	March 31, 2013

Average Annual Returns

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

Average Annual Total Returns Fidelity Focused High Income Fund	Past 1 year	Past 5 years	Life of fund		Inception Date
Class: Fidelity Focused High Income Fund Return Before Taxes	11.69%	7.30%	6.59%	[1]	Sep. 08, 2004
Class: Fidelity Focused High Income Fund Return After Taxes on Distributions	9.42%	4.48%	4.06%	[1]	Sep. 08, 2004
Class: Fidelity Focused High Income Fund Return After Taxes on Distributions and Sale of Fund Shares	7.68%	4.58%	4.14%	[1]	Sep. 08, 2004
The BofA Merrill Lynch℠ BB US High Yield Constrained Index (reflects no deduction for fees, expenses, or taxes)	13.96%	10.18%	8.30%	[1]	Sep. 08, 2004

[1] From September 8, 2004.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

FIDELITY SUMMER STREET TRUST

Prospectus Date

rr_ProspectusDate

Jun. 29, 2013

A T C | Fidelity Global High Income Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

Fund Summary

Fund/Class:
Fidelity^® Global High Income Fund/Fidelity Advisor^® Global High Income Fund A, T, C

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The fund seeks a high level of current income. Growth of capital may also be considered.

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, hold, or sell shares 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 $50,000 in the fund or certain other Fidelity funds. More information about these and other discounts is available from your investment professional and in the Fund Distribution section beginning on page (Click Here) of the prospectus.

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 55% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

55.00%

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 $50,000 in the fund or certain other Fidelity funds.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

$ 50,000

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 and if you hold your shares:

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

Sell All Shares

Expense Example, No Redemption, By Year, Caption [Text]

rr_ExpenseExampleNoRedemptionByYearCaption

Hold Shares

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

• Normally investing primarily in income producing debt securities, preferred stocks, and convertible securities, with an emphasis on lower-quality debt securities, of U.S. and non-U.S. issuers, including emerging market countries.
• Potentially investing in non-income producing securities, including defaulted securities and common stocks.
• Investing in companies in troubled or uncertain financial condition.
• Allocating investments across different countries and regions.
• Investing in securities issued throughout the world, including potentially significant investments in U.S. issuers.
• Using a base neutral mix of approximately 60% U.S. high yield, 20% emerging markets debt, 15% European high yield, and 5% Asian high yield.
• Adjusting allocation among markets within the following ranges: U.S. high yield (40%-80%); emerging markets debt (5%-35%); European high yield (0%-30%); and Asian high yield (0%-10%).
• Analyzing an issuer using fundamental factors (e.g., financial condition, earnings outlook, and strategy) and evaluating each security's current price relative to estimated long-term value to select investments.

Risk [Heading]

rr_RiskHeading

Principal Investment Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

• Stock Market Volatility. Stock markets are volatile and can decline significantly in response to adverse issuer, political, regulatory, market, or economic developments. Different parts of the market, including different market sectors, and different types of securities can react differently to these developments.
• Interest Rate Changes. Interest rate increases can cause the price of a debt security to decrease.
• Foreign Exposure. Foreign markets, particularly emerging 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. Emerging markets can be subject to greater social, economic, regulatory, and political uncertainties and can be extremely volatile. Foreign exchange rates also can be extremely volatile.
• 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, also referred to as high yield debt securities) and certain types of other securities involve greater risk of default or price changes due to changes in the credit quality of the issuer. The value of lower-quality debt securities and certain types of other securities can be more volatile due to increased sensitivity to adverse issuer, political, regulatory, market, or economic developments and can be difficult to resell.

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 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 performance of the fund's shares over the past year and compares the performance of the fund's shares to the performance of a securities market index and a hypothetical composite of market indexes over various periods of time. The indexes have characteristics relevant to the fund's investment strategies. Index descriptions appear in the Additional Information about the Indexes 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 performance of the fund's shares over the past year and compares the performance of the fund's shares to the performance of a securities market index and a hypothetical composite of market indexes 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

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

The returns in the bar chart do not reflect any applicable sales charges; if sales charges were reflected, returns would be lower than those shown.

Calendar Year

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

During the period shown in the chart for Class A:	Returns	Quarter ended
Highest Quarter Return	5.88%	March 31, 2012
Lowest Quarter Return	0.75%	June 30, 2012
Year-to-Date Return	1.41%	March 31, 2013

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Returns

Performance Table Does Reflect Sales Loads

rr_PerformanceTableDoesReflectSalesLoads

Unlike the returns in the bar chart, the returns in the table reflect the maximum applicable sales charges.

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 One Class of after Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

After-tax returns for Class A are shown in the table below and after-tax returns for other classes will vary.

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

Unlike the returns in the bar chart, the returns in the table reflect the maximum applicable sales charges. 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. After-tax returns for Class A are shown in the table below and after-tax returns for other classes will vary. 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

A T C | Fidelity Global High Income Fund | Class A

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) on purchases (as a % of offering price)

rr_MaximumCumulativeSalesChargeOverOfferingPrice

4.00%

Maximum contingent deferred sales charge (as a % of the lesser of original purchase price or redemption proceeds)

rr_MaximumDeferredSalesChargeOverOther

none

^[1]

Redemption fee on shares held less than 90 days (as a % of amount redeemed)

rr_RedemptionFeeOverRedemption

1.00%

Management fee

rr_ManagementFeesOverAssets

0.72%

Distribution and/or Service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.27%

Total annual operating expenses

rr_ExpensesOverAssets

1.24%

Expenses Deferred Charges [Text Block]

rr_ExpensesDeferredChargesTextBlock

Class A and Class T purchases of $1 million or more will not be subject to a front-end sales charge. Such Class A and Class T purchases may be subject, upon redemption, to a contingent deferred sales charge (CDSC) of 1.00% or 0.25%, respectively.

1 year

rr_ExpenseExampleYear01

521

3 years

rr_ExpenseExampleYear03

778

5 years

rr_ExpenseExampleYear05

1,054

10 years

rr_ExpenseExampleYear10

1,840

1 year

rr_ExpenseExampleNoRedemptionYear01

521

3 years

rr_ExpenseExampleNoRedemptionYear03

778

5 years

rr_ExpenseExampleNoRedemptionYear05

1,054

10 years

rr_ExpenseExampleNoRedemptionYear10

1,840

2012

rr_AnnualReturn2012

16.63%

Year to Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date Return

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2013

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

1.41%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter Return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Mar. 31, 2012

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

5.88%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter Return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Jun. 30, 2012

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

0.75%

A T C | Fidelity Global High Income Fund | Class T

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) on purchases (as a % of offering price)

rr_MaximumCumulativeSalesChargeOverOfferingPrice

4.00%

Maximum contingent deferred sales charge (as a % of the lesser of original purchase price or redemption proceeds)

rr_MaximumDeferredSalesChargeOverOther

none

^[1]

Redemption fee on shares held less than 90 days (as a % of amount redeemed)

rr_RedemptionFeeOverRedemption

1.00%

Management fee

rr_ManagementFeesOverAssets

0.72%

Distribution and/or Service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.28%

Total annual operating expenses

rr_ExpensesOverAssets

1.25%

Expenses Deferred Charges [Text Block]

rr_ExpensesDeferredChargesTextBlock

Class A and Class T purchases of $1 million or more will not be subject to a front-end sales charge. Such Class A and Class T purchases may be subject, upon redemption, to a contingent deferred sales charge (CDSC) of 1.00% or 0.25%, respectively.

1 year

rr_ExpenseExampleYear01

522

3 years

rr_ExpenseExampleYear03

781

5 years

rr_ExpenseExampleYear05

1,059

10 years

rr_ExpenseExampleYear10

1,851

1 year

rr_ExpenseExampleNoRedemptionYear01

522

3 years

rr_ExpenseExampleNoRedemptionYear03

781

5 years

rr_ExpenseExampleNoRedemptionYear05

1,059

10 years

rr_ExpenseExampleNoRedemptionYear10

1,851

A T C | Fidelity Global High Income Fund | Class C

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) on purchases (as a % of offering price)

rr_MaximumCumulativeSalesChargeOverOfferingPrice

none

Maximum contingent deferred sales charge (as a % of the lesser of original purchase price or redemption proceeds)

rr_MaximumDeferredSalesChargeOverOther

1.00%

^[2]

Redemption fee on shares held less than 90 days (as a % of amount redeemed)

rr_RedemptionFeeOverRedemption

1.00%

Management fee

rr_ManagementFeesOverAssets

0.72%

Distribution and/or Service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other expenses

rr_OtherExpensesOverAssets

0.29%

Total annual operating expenses

rr_ExpensesOverAssets

2.01%

Expenses Deferred Charges [Text Block]

rr_ExpensesDeferredChargesTextBlock

On Class C shares redeemed less than one year after purchase.

1 year

rr_ExpenseExampleYear01

304

3 years

rr_ExpenseExampleYear03

630

5 years

rr_ExpenseExampleYear05

1,083

10 years

rr_ExpenseExampleYear10

2,338

1 year

rr_ExpenseExampleNoRedemptionYear01

204

3 years

rr_ExpenseExampleNoRedemptionYear03

630

5 years

rr_ExpenseExampleNoRedemptionYear05

1,083

10 years

rr_ExpenseExampleNoRedemptionYear10

$ 2,338

A T C | Fidelity Global High Income Fund | Return Before Taxes | Class A

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Class A - Return Before Taxes

Past 1 year

rr_AverageAnnualReturnYear01

11.97%

Life of class

rr_AverageAnnualReturnSinceInception

3.94%

^[3]

Inception Date

rr_AverageAnnualReturnInceptionDate

May 11, 2011

A T C | Fidelity Global High Income Fund | Return Before Taxes | Class T

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Class T - Return Before Taxes

Past 1 year

rr_AverageAnnualReturnYear01

11.95%

Life of class

rr_AverageAnnualReturnSinceInception

3.93%

^[3]

Inception Date

rr_AverageAnnualReturnInceptionDate

May 11, 2011

A T C | Fidelity Global High Income Fund | Return Before Taxes | Class C

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Class C - Return Before Taxes

Past 1 year

rr_AverageAnnualReturnYear01

14.73%

Life of class

rr_AverageAnnualReturnSinceInception

5.74%

^[3]

Inception Date

rr_AverageAnnualReturnInceptionDate

May 11, 2011

A T C | Fidelity Global High Income Fund | Return After Taxes on Distributions | Class A

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Class A - Return After Taxes on Distributions

Past 1 year

rr_AverageAnnualReturnYear01

9.91%

Life of class

rr_AverageAnnualReturnSinceInception

2.15%

^[3]

Inception Date

rr_AverageAnnualReturnInceptionDate

May 11, 2011

A T C | Fidelity Global High Income Fund | Return After Taxes on Distributions and Sale of Fund Shares | Class A

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Class A - Return After Taxes on Distributions and Sale of Fund Shares

Past 1 year

rr_AverageAnnualReturnYear01

7.70%

Life of class

rr_AverageAnnualReturnSinceInception

2.29%

^[3]

Inception Date

rr_AverageAnnualReturnInceptionDate

May 11, 2011

A T C | Fidelity Global High Income Fund | The BofA Merrill Lynch℠ Global High Yield and Emerging Markets Plus Index (reflects no deduction for fees, expenses, or taxes)

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

The BofA Merrill Lynch^SM Global High Yield and Emerging Markets Plus Index

Past 1 year

rr_AverageAnnualReturnYear01

19.74%

Life of class

rr_AverageAnnualReturnSinceInception

9.89%

^[3]

Inception Date

rr_AverageAnnualReturnInceptionDate

May 11, 2011

A T C | Fidelity Global High Income Fund | Fidelity Global High Income Composite Index℠ (reflects no deduction for fees, expenses, or taxes)

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Fidelity Global High Income Composite Index^SM

Past 1 year

rr_AverageAnnualReturnYear01

18.79%

Life of class

rr_AverageAnnualReturnSinceInception

9.01%

^[3]

Inception Date

rr_AverageAnnualReturnInceptionDate

May 11, 2011

[1] Class A and Class T purchases of $1 million or more will not be subject to a front-end sales charge. Such Class A and Class T purchases may be subject, upon redemption, to a contingent deferred sales charge (CDSC) of 1.00% or 0.25%, respectively.

[2] On Class C shares redeemed less than one year after purchase.

[3] From May 11, 2011.

XML

Series | Fidelity Series High Income Fund

Fund Summary

Fund/Class:
Fidelity^®Series High Income Fund/Fidelity Series High Income Fund

Investment Objective

The fund seeks a high level of current income. Growth of capital may also be considered.

Fee Table

The following table describes the fees and expenses that may be incurred when you buy and hold shares of the fund.

Shareholder fees
(fees paid directly from your investment)

Shareholder Fees (USD $)	Series Fidelity Series High Income Fund Class: Fidelity Series High Income Fund
Shareholder fees (fees paid directly from your investment)	none

Annual class operating expenses
(expenses that you pay each year as a % of the value of your investment)

Annual Class Operating Expenses	Series Fidelity Series High Income Fund Class: Fidelity Series High Income Fund
Management fee	0.57%
Distribution and/or Service (12b-1) fees	none
Other expenses	0.14%
Total annual operating expenses	0.71%

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:

Expense Example (USD $)	Series Fidelity Series High Income Fund Class: Fidelity Series High Income Fund
1 year	73
3 years	227
5 years	395
10 years	883

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 operating expenses or in the example, affect the fund's performance. During the most recent fiscal year, the fund's portfolio turnover rate was 45% of the average value of its portfolio.

Principal Investment Strategies

• Normally investing primarily in income producing debt securities, preferred stocks, and convertible securities, with an emphasis on lower-quality debt securities.
• Potentially investing in non-income producing securities, including defaulted securities and common stocks.
• Investing in companies in troubled or uncertain financial condition.
• Managing the fund to have similar credit quality distribution to an index representing the overall high yield bond market, which as of April 30, 2013, was The BofA Merrill Lynch^SM US High Yield Constrained Index.
• 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.

Principal Investment Risks

• Stock Market Volatility. Stock markets are volatile and can decline significantly in response to adverse issuer, political, regulatory, market, or economic developments. Different parts of the market, including different market sectors, and different types of securities can react differently to these developments.
• Interest Rate Changes. Interest rate increases can cause the price of a debt security to decrease.
• Foreign Exposure. Foreign markets, particularly emerging 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.
• 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, also referred to as high yield debt securities) and certain types of other securities involve greater risk of default or price changes due to changes in the credit quality of the issuer. The value of lower-quality debt securities and certain types of other securities can be more volatile due to increased sensitivity to adverse issuer, political, regulatory, market, or economic developments and can be difficult to resell.

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.

Performance

The following information is intended to help you understand the risks of investing in the fund. The information illustrates the performance of the fund's shares over the past 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 Information about the Index section of the prospectus. Past performance (before and after taxes) is not an indication of future performance.

Visit www.fidelity.com for updated return information.

Year-by-Year Returns
Calendar Year

During the period shown in the chart:	Returns	Quarter ended
Highest Quarter Return	6.09%	March 31, 2012
Lowest Quarter Return	1.32%	June 30, 2012
Year-to-Date Return	2.96%	March 31, 2013

Average Annual Returns

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.

For the periods ended
December 31, 2012

Average Annual Total Returns Series Fidelity Series High Income Fund	Past 1 year	Life of class		Inception Date
Class: Fidelity Series High Income Fund Return Before Taxes	15.71%	8.04%	[1]	Mar. 10, 2011
Class: Fidelity Series High Income Fund Return After Taxes on Distributions	13.39%	5.84%	[1]	Mar. 10, 2011
Class: Fidelity Series High Income Fund Return After Taxes on Distributions and Sale of Fund Shares	10.13%	5.52%	[1]	Mar. 10, 2011
The BofA Merrill Lynch℠ US High Yield Constrained Index (reflects no deduction for fees, expenses, or taxes)	15.55%	8.76%	[1]	Mar. 10, 2011

[1] From March 10, 2011.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

FIDELITY SUMMER STREET TRUST

Prospectus Date

rr_ProspectusDate

Jun. 29, 2013

F | Fidelity Series High Income Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

Fund Summary

Fund/Class:
Fidelity^®Series High Income Fund/F

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The fund seeks a high level of current income. Growth of capital may also be considered.

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 45% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

45.00%

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 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:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

• Normally investing primarily in income producing debt securities, preferred stocks, and convertible securities, with an emphasis on lower-quality debt securities.
• Potentially investing in non-income producing securities, including defaulted securities and common stocks.
• Investing in companies in troubled or uncertain financial condition.
• Managing the fund to have similar credit quality distribution to an index representing the overall high yield bond market, which as of April 30, 2013, was The BofA Merrill Lynch^SM US High Yield Constrained Index.
• 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_RiskHeading

Principal Investment Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

• Stock Market Volatility. Stock markets are volatile and can decline significantly in response to adverse issuer, political, regulatory, market, or economic developments. Different parts of the market, including different market sectors, and different types of securities can react differently to these developments.
• Interest Rate Changes. Interest rate increases can cause the price of a debt security to decrease.
• Foreign Exposure. Foreign markets, particularly emerging 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.
• 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, also referred to as high yield debt securities) and certain types of other securities involve greater risk of default or price changes due to changes in the credit quality of the issuer. The value of lower-quality debt securities and certain types of other securities can be more volatile due to increased sensitivity to adverse issuer, political, regulatory, market, or economic developments and can be difficult to resell.

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 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 performance of the fund's shares over the past 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 Information about the Index section of the prospectus. Past performance (before and after taxes) is not an indication of future performance.

Visit www.401k.com and log in for updated return information.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The information illustrates the performance of the fund's shares over the past 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.401k.com and log in for updated return information

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 Year

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

During the period shown in the chart:	Returns	Quarter ended
Highest Quarter Return	6.12%	March 31, 2012
Lowest Quarter Return	1.36%	June 30, 2012
Year-to-Date Return	2.99%	March 31, 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 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.

For the periods ended
December 31, 2012

F | Fidelity Series High Income Fund | Class F

Risk/Return:

rr_RiskReturnAbstract

Shareholder fees (fees paid directly from your investment)

rr_ShareholderFeeOther

none

Management fee

rr_ManagementFeesOverAssets

0.57%

Distribution and/or Service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.01%

Total annual operating expenses

rr_ExpensesOverAssets

0.58%

1 year

rr_ExpenseExampleYear01

59

3 years

rr_ExpenseExampleYear03

186

5 years

rr_ExpenseExampleYear05

324

10 years

rr_ExpenseExampleYear10

$ 726

2012

rr_AnnualReturn2012

15.86%

Year to Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date Return

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2013

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

2.99%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter Return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Mar. 31, 2012

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

6.12%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter Return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Jun. 30, 2012

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

1.36%

F | Fidelity Series High Income Fund | Return Before Taxes | Class F

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class F

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

Past 1 year

rr_AverageAnnualReturnYear01

15.86%

Life of class

rr_AverageAnnualReturnSinceInception

8.17%

^[1]

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 10, 2011

F | Fidelity Series High Income Fund | Return After Taxes on Distributions | Class F

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class F

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

Past 1 year

rr_AverageAnnualReturnYear01

13.48%

Life of class

rr_AverageAnnualReturnSinceInception

5.92%

^[1]

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 10, 2011

F | Fidelity Series High Income Fund | Return After Taxes on Distributions and Sale of Fund Shares | Class F

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class F

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

Past 1 year

rr_AverageAnnualReturnYear01

10.22%

Life of class

rr_AverageAnnualReturnSinceInception

5.61%

^[1]

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 10, 2011

F | Fidelity Series High Income Fund | The BofA Merrill Lynch℠ US High Yield Constrained Index (reflects no deduction for fees, expenses, or taxes)

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

The BofA Merrill Lynch^SM US High Yield Constrained Index

Past 1 year

rr_AverageAnnualReturnYear01

15.55%

Life of class

rr_AverageAnnualReturnSinceInception

8.76%

^[1]

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 10, 2011

[1] From March 10, 2011.

XML

Fidelity Capital & Income Fund

Fund Summary

Fund:
Fidelity^®Capital & Income Fund

Investment Objective

The fund seeks to provide a combination of income and capital growth.

Fee Table

The following table describes the fees and expenses that may be incurred when you buy and hold shares of the fund.

Shareholder fees
(fees paid directly from your investment)

Shareholder Fees	Fidelity Capital & Income Fund Class: Fidelity Capital & Income Fund
Redemption fee on shares held less than 90 days (as a % of amount redeemed)	1.00%

Annual fund operating expenses
(expenses that you pay each year as a % of the value of your investment)

Annual Fund Operating Expenses	Fidelity Capital & Income Fund Class: Fidelity Capital & Income Fund
Management fee	0.57%
Distribution and/or Service (12b-1) fees	none
Other expenses	0.16%
Total annual fund operating expenses	0.73%

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:

Expense Example (USD $)	Fidelity Capital & Income Fund Class: Fidelity Capital & Income Fund
1 year	75
3 years	233
5 years	406
10 years	906

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 operating expenses or in the example, affect the fund's performance. During the most recent fiscal year, the fund's portfolio turnover rate was 60% of the average value of its portfolio.

Principal Investment Strategies

• Investing in equity and debt securities, including defaulted securities, with an emphasis on lower-quality debt securities.
• Investing in companies in troubled or uncertain financial condition.
• 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.

Principal Investment Risks

• Stock Market Volatility. Stock markets are volatile and can decline significantly in response to adverse issuer, political, regulatory, market, or economic developments. Different parts of the market, including different market sectors, and different types of securities can react differently to these developments.
• Interest Rate Changes. Interest rate increases can cause the price of a debt security to decrease.
• Foreign Exposure. Foreign markets, particularly emerging 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.
• 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, also referred to as high yield debt securities) and certain types of other securities involve greater risk of default or price changes due to changes in the credit quality of the issuer. The value of lower-quality debt securities and certain types of other securities can be more volatile due to increased sensitivity to adverse issuer, political, regulatory, market, or economic developments and can be difficult to resell.

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.

Performance

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 Information about the Indexes section of the prospectus. Past performance (before and after taxes) is not an indication of future performance.

Visit www.fidelity.com for updated return information.

Year-by-Year Returns
Calendar Years

During the periods shown in the chart:	Returns	Quarter ended
Highest Quarter Return	26.67%	June 30, 2009
Lowest Quarter Return	-23.09%	December 31, 2008
Year-to-Date Return	3.62%	March 31, 2013

Average Annual Returns

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.

For the periods ended
December 31, 2012

Average Annual Total Returns Fidelity Capital & Income Fund	Past 1 year	Past 5 years	Past 10 years
Class: Fidelity Capital & Income Fund Return Before Taxes	16.41%	9.41%	11.71%
Class: Fidelity Capital & Income Fund Return After Taxes on Distributions	13.98%	6.72%	9.05%
Class: Fidelity Capital & Income Fund Return After Taxes on Distributions and Sale of Fund Shares	10.58%	6.41%	8.61%
The BofA Merrill Lynch℠ US High Yield Constrained Index (reflects no deduction for fees, expenses, or taxes)	15.55%	10.14%	10.38%

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

FIDELITY SUMMER STREET TRUST

Prospectus Date

rr_ProspectusDate

Jun. 29, 2013

Series | Fidelity Series High Income Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

Fund Summary

Fund/Class:
Fidelity^®Series High Income Fund/Fidelity Series High Income Fund

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The fund seeks a high level of current income. Growth of capital may also be considered.

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 45% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

45.00%

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 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:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

• Normally investing primarily in income producing debt securities, preferred stocks, and convertible securities, with an emphasis on lower-quality debt securities.
• Potentially investing in non-income producing securities, including defaulted securities and common stocks.
• Investing in companies in troubled or uncertain financial condition.
• Managing the fund to have similar credit quality distribution to an index representing the overall high yield bond market, which as of April 30, 2013, was The BofA Merrill Lynch^SM US High Yield Constrained Index.
• 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_RiskHeading

Principal Investment Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

• Stock Market Volatility. Stock markets are volatile and can decline significantly in response to adverse issuer, political, regulatory, market, or economic developments. Different parts of the market, including different market sectors, and different types of securities can react differently to these developments.
• Interest Rate Changes. Interest rate increases can cause the price of a debt security to decrease.
• Foreign Exposure. Foreign markets, particularly emerging 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.
• 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, also referred to as high yield debt securities) and certain types of other securities involve greater risk of default or price changes due to changes in the credit quality of the issuer. The value of lower-quality debt securities and certain types of other securities can be more volatile due to increased sensitivity to adverse issuer, political, regulatory, market, or economic developments and can be difficult to resell.

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 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 performance of the fund's shares over the past 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 Information about the Index section of the prospectus. Past performance (before and after taxes) is not an indication of future performance.

Visit www.fidelity.com for updated return information.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The information illustrates the performance of the fund's shares over the past 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.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 Year

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

During the period shown in the chart:	Returns	Quarter ended
Highest Quarter Return	6.09%	March 31, 2012
Lowest Quarter Return	1.32%	June 30, 2012
Year-to-Date Return	2.96%	March 31, 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 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.

For the periods ended
December 31, 2012

Series | Fidelity Series High Income Fund | Class: Fidelity Series High Income Fund

Risk/Return:

rr_RiskReturnAbstract

Shareholder fees (fees paid directly from your investment)

rr_ShareholderFeeOther

none

Management fee

rr_ManagementFeesOverAssets

0.57%

Distribution and/or Service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.14%

Total annual operating expenses

rr_ExpensesOverAssets

0.71%

1 year

rr_ExpenseExampleYear01

73

3 years

rr_ExpenseExampleYear03

227

5 years

rr_ExpenseExampleYear05

395

10 years

rr_ExpenseExampleYear10

$ 883

2012

rr_AnnualReturn2012

15.71%

Year to Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date Return

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2013

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

2.96%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter Return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Mar. 31, 2012

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

6.09%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter Return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Jun. 30, 2012

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

1.32%

Series | Fidelity Series High Income Fund | Return Before Taxes | Class: Fidelity Series High Income Fund

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity Series High Income Fund

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

Past 1 year

rr_AverageAnnualReturnYear01

15.71%

Life of class

rr_AverageAnnualReturnSinceInception

8.04%

^[1]

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 10, 2011

Series | Fidelity Series High Income Fund | Return After Taxes on Distributions | Class: Fidelity Series High Income Fund

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity Series High Income Fund

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

Past 1 year

rr_AverageAnnualReturnYear01

13.39%

Life of class

rr_AverageAnnualReturnSinceInception

5.84%

^[1]

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 10, 2011

Series | Fidelity Series High Income Fund | Return After Taxes on Distributions and Sale of Fund Shares | Class: Fidelity Series High Income Fund

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity Series High Income Fund

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

Past 1 year

rr_AverageAnnualReturnYear01

10.13%

Life of class

rr_AverageAnnualReturnSinceInception

5.52%

^[1]

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 10, 2011

Series | Fidelity Series High Income Fund | The BofA Merrill Lynch℠ US High Yield Constrained Index (reflects no deduction for fees, expenses, or taxes)

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

The BofA Merrill Lynch^SM US High Yield Constrained Index

Past 1 year

rr_AverageAnnualReturnYear01

15.55%

Life of class

rr_AverageAnnualReturnSinceInception

8.76%

^[1]

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 10, 2011

[1] From March 10, 2011.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

FIDELITY SUMMER STREET TRUST

Prospectus Date

rr_ProspectusDate

Jun. 29, 2013

Retail | Fidelity Global High Income Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

Fund Summary

Fund/Class:
Fidelity^® Global High Income Fund/Fidelity Global High Income Fund

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The fund seeks a high level of current income. Growth of capital may also be considered.

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, hold, or sell 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 55% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

55.00%

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 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:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

• Normally investing primarily in income producing debt securities, preferred stocks, and convertible securities, with an emphasis on lower-quality debt securities, of U.S. and non-U.S. issuers, including emerging market countries.
• Potentially investing in non-income producing securities, including defaulted securities and common stocks.
• Investing in companies in troubled or uncertain financial condition.
• Allocating investments across different countries and regions.
• Investing in securities issued throughout the world, including potentially significant investments in U.S. issuers.
• Using a base neutral mix of approximately 60% U.S. high yield, 20% emerging markets debt, 15% European high yield, and 5% Asian high yield.
• Adjusting allocation among markets within the following ranges: U.S. high yield (40%-80%); emerging markets debt (5%-35%); European high yield (0%-30%); and Asian high yield (0%-10%).
• Analyzing an issuer using fundamental factors (e.g., financial condition, earnings outlook, and strategy) and evaluating each security's current price relative to estimated long-term value to select investments.

Risk [Heading]

rr_RiskHeading

Principal Investment Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

• Stock Market Volatility. Stock markets are volatile and can decline significantly in response to adverse issuer, political, regulatory, market, or economic developments. Different parts of the market, including different market sectors, and different types of securities can react differently to these developments.
• Interest Rate Changes. Interest rate increases can cause the price of a debt security to decrease.
• Foreign Exposure. Foreign markets, particularly emerging 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. Emerging markets can be subject to greater social, economic, regulatory, and political uncertainties and can be extremely volatile. Foreign exchange rates also can be extremely volatile.
• 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, also referred to as high yield debt securities) and certain types of other securities involve greater risk of default or price changes due to changes in the credit quality of the issuer. The value of lower-quality debt securities and certain types of other securities can be more volatile due to increased sensitivity to adverse issuer, political, regulatory, market, or economic developments and can be difficult to resell.

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 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 performance of the fund's shares over the past year and compares the performance of the fund's shares to the performance of a securities market index and a hypothetical composite of market indexes over various periods of time. The indexes have characteristics relevant to the fund's investment strategies. Index descriptions appear in the Additional Information about the Indexes section of the prospectus. Past performance (before and after taxes) is not an indication of future performance.

Visit www.fidelity.com for updated return information.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The information illustrates the performance of the fund's shares over the past year and compares the performance of the fund's shares to the performance of a securities market index and a hypothetical composite of market indexes over various periods of time.

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

www.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 Year

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

During the period shown in the chart:	Returns	Quarter ended
Highest Quarter Return	5.95%	March 31, 2012
Lowest Quarter Return	0.81%	June 30, 2012
Year-to-Date Return	1.49%	March 31, 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 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.

For the periods ended
December 31, 2012

Retail | Fidelity Global High Income Fund | Class: Fidelity Global High Income Fund

Risk/Return:

rr_RiskReturnAbstract

Redemption fee on shares held less than 90 days (as a % of amount redeemed)

rr_RedemptionFeeOverRedemption

1.00%

Management fee

rr_ManagementFeesOverAssets

0.72%

Distribution and/or Service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.24%

Total annual operating expenses

rr_ExpensesOverAssets

0.96%

1 year

rr_ExpenseExampleYear01

$ 98

3 years

rr_ExpenseExampleYear03

306

5 years

rr_ExpenseExampleYear05

531

10 years

rr_ExpenseExampleYear10

$ 1,178

2012

rr_AnnualReturn2012

16.96%

Year to Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date Return

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2013

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

1.49%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter Return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Mar. 31, 2012

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

5.95%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter Return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Jun. 30, 2012

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

0.81%

Retail | Fidelity Global High Income Fund | Return Before Taxes | Class: Fidelity Global High Income Fund

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity Global High Income Fund

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

Past 1 year

rr_AverageAnnualReturnYear01

16.96%

Life of class

rr_AverageAnnualReturnSinceInception

6.84%

^[1]

Inception Date

rr_AverageAnnualReturnInceptionDate

May 11, 2011

Retail | Fidelity Global High Income Fund | Return After Taxes on Distributions | Class: Fidelity Global High Income Fund

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity Global High Income Fund

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

Past 1 year

rr_AverageAnnualReturnYear01

14.70%

Life of class

rr_AverageAnnualReturnSinceInception

4.91%

^[1]

Inception Date

rr_AverageAnnualReturnInceptionDate

May 11, 2011

Retail | Fidelity Global High Income Fund | Return After Taxes on Distributions and Sale of Fund Shares | Class: Fidelity Global High Income Fund

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity Global High Income Fund

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

Past 1 year

rr_AverageAnnualReturnYear01

10.93%

Life of class

rr_AverageAnnualReturnSinceInception

4.66%

^[1]

Inception Date

rr_AverageAnnualReturnInceptionDate

May 11, 2011

Retail | Fidelity Global High Income Fund | The BofA Merrill Lynch℠ Global High Yield and Emerging Markets Plus Index (reflects no deduction for fees, expenses, or taxes)

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

The BofA Merrill Lynch^SM Global High Yield and Emerging Markets Plus Index

Past 1 year

rr_AverageAnnualReturnYear01

19.74%

Life of class

rr_AverageAnnualReturnSinceInception

9.89%

^[1]

Inception Date

rr_AverageAnnualReturnInceptionDate

May 11, 2011

Retail | Fidelity Global High Income Fund | Fidelity Global High Income Composite Index℠ (reflects no deduction for fees, expenses, or taxes)

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Fidelity Global High Income Composite Index^SM

Past 1 year

rr_AverageAnnualReturnYear01

18.79%

Life of class

rr_AverageAnnualReturnSinceInception

9.01%

^[1]

Inception Date

rr_AverageAnnualReturnInceptionDate

May 11, 2011

[1] From May 11, 2011.

XML

Retail | Fidelity Global High Income Fund

Fund Summary

Fund/Class:
Fidelity^® Global High Income Fund/Fidelity Global High Income Fund

Investment Objective

The fund seeks a high level of current income. Growth of capital may also be considered.

Fee Table

The following table describes the fees and expenses that may be incurred when you buy, hold, or sell shares of the fund.

Shareholder fees
(fees paid directly from your investment)

Shareholder Fees	Retail Fidelity Global High Income Fund Class: Fidelity Global High Income Fund
Redemption fee on shares held less than 90 days (as a % of amount redeemed)	1.00%

Annual class operating expenses
(expenses that you pay each year as a % of the value of your investment)

Annual Class Operating Expenses	Retail Fidelity Global High Income Fund Class: Fidelity Global High Income Fund
Management fee	0.72%
Distribution and/or Service (12b-1) fees	none
Other expenses	0.24%
Total annual operating expenses	0.96%

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:

Expense Example (USD $)	Retail Fidelity Global High Income Fund Class: Fidelity Global High Income Fund
1 year	98
3 years	306
5 years	531
10 years	1,178

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 operating expenses or in the example, affect the fund's performance. During the most recent fiscal year, the fund's portfolio turnover rate was 55% of the average value of its portfolio.

Principal Investment Strategies

• Normally investing primarily in income producing debt securities, preferred stocks, and convertible securities, with an emphasis on lower-quality debt securities, of U.S. and non-U.S. issuers, including emerging market countries.
• Potentially investing in non-income producing securities, including defaulted securities and common stocks.
• Investing in companies in troubled or uncertain financial condition.
• Allocating investments across different countries and regions.
• Investing in securities issued throughout the world, including potentially significant investments in U.S. issuers.
• Using a base neutral mix of approximately 60% U.S. high yield, 20% emerging markets debt, 15% European high yield, and 5% Asian high yield.
• Adjusting allocation among markets within the following ranges: U.S. high yield (40%-80%); emerging markets debt (5%-35%); European high yield (0%-30%); and Asian high yield (0%-10%).
• Analyzing an issuer using fundamental factors (e.g., financial condition, earnings outlook, and strategy) and evaluating each security's current price relative to estimated long-term value to select investments.

Principal Investment Risks

• Stock Market Volatility. Stock markets are volatile and can decline significantly in response to adverse issuer, political, regulatory, market, or economic developments. Different parts of the market, including different market sectors, and different types of securities can react differently to these developments.
• Interest Rate Changes. Interest rate increases can cause the price of a debt security to decrease.
• Foreign Exposure. Foreign markets, particularly emerging 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. Emerging markets can be subject to greater social, economic, regulatory, and political uncertainties and can be extremely volatile. Foreign exchange rates also can be extremely volatile.
• 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, also referred to as high yield debt securities) and certain types of other securities involve greater risk of default or price changes due to changes in the credit quality of the issuer. The value of lower-quality debt securities and certain types of other securities can be more volatile due to increased sensitivity to adverse issuer, political, regulatory, market, or economic developments and can be difficult to resell.

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.

Performance

The following information is intended to help you understand the risks of investing in the fund. The information illustrates the performance of the fund's shares over the past year and compares the performance of the fund's shares to the performance of a securities market index and a hypothetical composite of market indexes over various periods of time. The indexes have characteristics relevant to the fund's investment strategies. Index descriptions appear in the Additional Information about the Indexes section of the prospectus. Past performance (before and after taxes) is not an indication of future performance.

Visit www.fidelity.com for updated return information.

Year-by-Year Returns
Calendar Year

During the period shown in the chart:	Returns	Quarter ended
Highest Quarter Return	5.95%	March 31, 2012
Lowest Quarter Return	0.81%	June 30, 2012
Year-to-Date Return	1.49%	March 31, 2013

Average Annual Returns

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.

For the periods ended
December 31, 2012

Average Annual Total Returns Retail Fidelity Global High Income Fund	Past 1 year	Life of class		Inception Date
Class: Fidelity Global High Income Fund Return Before Taxes	16.96%	6.84%	[1]	May 11, 2011
Class: Fidelity Global High Income Fund Return After Taxes on Distributions	14.70%	4.91%	[1]	May 11, 2011
Class: Fidelity Global High Income Fund Return After Taxes on Distributions and Sale of Fund Shares	10.93%	4.66%	[1]	May 11, 2011
The BofA Merrill Lynch℠ Global High Yield and Emerging Markets Plus Index (reflects no deduction for fees, expenses, or taxes)	19.74%	9.89%	[1]	May 11, 2011
Fidelity Global High Income Composite Index℠ (reflects no deduction for fees, expenses, or taxes)	18.79%	9.01%	[1]	May 11, 2011

[1] From May 11, 2011.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

FIDELITY SUMMER STREET TRUST

Prospectus Date

rr_ProspectusDate

Jun. 29, 2013

Inst | Fidelity Global High Income Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

Fund Summary

Fund/Class:
Fidelity^® Global High Income Fund/Fidelity Advisor^® Global High Income Fund Institutional

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The fund seeks a high level of current income. Growth of capital may also be considered.

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, hold, or sell 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 55% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

55.00%

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 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:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

• Normally investing primarily in income producing debt securities, preferred stocks, and convertible securities, with an emphasis on lower-quality debt securities, of U.S. and non-U.S. issuers, including emerging market countries.
• Potentially investing in non-income producing securities, including defaulted securities and common stocks.
• Investing in companies in troubled or uncertain financial condition.
• Allocating investments across different countries and regions.
• Investing in securities issued throughout the world, including potentially significant investments in U.S. issuers.
• Using a base neutral mix of approximately 60% U.S. high yield, 20% emerging markets debt, 15% European high yield, and 5% Asian high yield.
• Adjusting allocation among markets within the following ranges: U.S. high yield (40%-80%); emerging markets debt (5%-35%); European high yield (0%-30%); and Asian high yield (0%-10%).
• Analyzing an issuer using fundamental factors (e.g., financial condition, earnings outlook, and strategy) and evaluating each security's current price relative to estimated long-term value to select investments.

Risk [Heading]

rr_RiskHeading

Principal Investment Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

• Stock Market Volatility. Stock markets are volatile and can decline significantly in response to adverse issuer, political, regulatory, market, or economic developments. Different parts of the market, including different market sectors, and different types of securities can react differently to these developments.
• Interest Rate Changes. Interest rate increases can cause the price of a debt security to decrease.
• Foreign Exposure. Foreign markets, particularly emerging 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. Emerging markets can be subject to greater social, economic, regulatory, and political uncertainties and can be extremely volatile. Foreign exchange rates also can be extremely volatile.
• 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, also referred to as high yield debt securities) and certain types of other securities involve greater risk of default or price changes due to changes in the credit quality of the issuer. The value of lower-quality debt securities and certain types of other securities can be more volatile due to increased sensitivity to adverse issuer, political, regulatory, market, or economic developments and can be difficult to resell.

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 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 performance of the fund's shares over the past year and compares the performance of the fund's shares to the performance of a securities market index and a hypothetical composite of market indexes over various periods of time. The indexes have characteristics relevant to the fund's investment strategies. Index descriptions appear in the Additional Information about the Indexes 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 performance of the fund's shares over the past year and compares the performance of the fund's shares to the performance of a securities market index and a hypothetical composite of market indexes 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 Year

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

During the period shown in the chart:	Returns	Quarter ended
Highest Quarter Return	5.94%	March 31, 2012
Lowest Quarter Return	0.81%	June 30, 2012
Year-to-Date Return	1.49%	March 31, 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 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.

For the periods ended
December 31, 2012

Inst | Fidelity Global High Income Fund | Institutional Class

Risk/Return:

rr_RiskReturnAbstract

Redemption fee on shares held less than 90 days (as a % of amount redeemed)

rr_RedemptionFeeOverRedemption

1.00%

Management fee

rr_ManagementFeesOverAssets

0.72%

Distribution and/or Service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.26%

Total annual operating expenses

rr_ExpensesOverAssets

0.98%

1 year

rr_ExpenseExampleYear01

$ 100

3 years

rr_ExpenseExampleYear03

312

5 years

rr_ExpenseExampleYear05

542

10 years

rr_ExpenseExampleYear10

$ 1,201

2012

rr_AnnualReturn2012

16.92%

Year to Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date Return

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2013

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

1.49%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter Return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Mar. 31, 2012

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

5.94%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter Return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Jun. 30, 2012

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

0.81%

Inst | Fidelity Global High Income 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

16.92%

Life of class

rr_AverageAnnualReturnSinceInception

6.82%

^[1]

Inception Date

rr_AverageAnnualReturnInceptionDate

May 11, 2011

Inst | Fidelity Global High Income 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

14.68%

Life of class

rr_AverageAnnualReturnSinceInception

4.89%

^[1]

Inception Date

rr_AverageAnnualReturnInceptionDate

May 11, 2011

Inst | Fidelity Global High Income 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

10.91%

Life of class

rr_AverageAnnualReturnSinceInception

4.64%

^[1]

Inception Date

rr_AverageAnnualReturnInceptionDate

May 11, 2011

Inst | Fidelity Global High Income Fund | The BofA Merrill Lynch℠ Global High Yield and Emerging Markets Plus Index (reflects no deduction for fees, expenses, or taxes)

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

The BofA Merrill Lynch^SM Global High Yield and Emerging Markets Plus Index

Past 1 year

rr_AverageAnnualReturnYear01

19.74%

Life of class

rr_AverageAnnualReturnSinceInception

9.89%

^[1]

Inception Date

rr_AverageAnnualReturnInceptionDate

May 11, 2011

Inst | Fidelity Global High Income Fund | Fidelity Global High Income Composite Index℠ (reflects no deduction for fees, expenses, or taxes)

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Fidelity Global High Income Composite Index^SM

Past 1 year

rr_AverageAnnualReturnYear01

18.79%

Life of class

rr_AverageAnnualReturnSinceInception

9.01%

^[1]

Inception Date

rr_AverageAnnualReturnInceptionDate

May 11, 2011

[1] From May 11, 2011.

XML

A T C | Fidelity Global High Income Fund

Fund Summary

Fund/Class:
Fidelity^® Global High Income Fund/Fidelity Advisor^® Global High Income Fund A, T, C

Investment Objective

The fund seeks a high level of current income. Growth of capital may also be considered.

Fee Table

The following table describes the fees and expenses that may be incurred when you buy, hold, or sell shares 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 $50,000 in the fund or certain other Fidelity funds. More information about these and other discounts is available from your investment professional and in the Fund Distribution section beginning on page (Click Here) of the prospectus.

Shareholder fees
(fees paid directly from your investment)

Shareholder Fees A T C Fidelity Global High Income Fund	Class A		Class T		Class C
Maximum sales charge (load) on purchases (as a % of offering price)	4.00%		4.00%		none
Maximum contingent deferred sales charge (as a % of the lesser of original purchase price or redemption proceeds)	none	[1]	none	[1]	1.00%	[2]
Redemption fee on shares held less than 90 days (as a % of amount redeemed)	1.00%		1.00%		1.00%

Annual class operating expenses
(expenses that you pay each year as a % of the value of your investment)

Annual Class Operating Expenses A T C Fidelity Global High Income Fund	Class A	Class T	Class C
Management fee	0.72%	0.72%	0.72%
Distribution and/or Service (12b-1) fees	0.25%	0.25%	1.00%
Other expenses	0.27%	0.28%	0.29%
Total annual operating expenses	1.24%	1.25%	2.01%

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 and if you hold your shares:

Sell All Shares

Expense Example A T C Fidelity Global High Income Fund (USD $)	Class A	Class T	Class C
1 year	521	522	304
3 years	778	781	630
5 years	1,054	1,059	1,083
10 years	1,840	1,851	2,338

Hold Shares

Expense Example, No Redemption A T C Fidelity Global High Income Fund (USD $)	Class A	Class T	Class C
1 year	521	522	204
3 years	778	781	630
5 years	1,054	1,059	1,083
10 years	1,840	1,851	2,338

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 operating expenses or in the example, affect the fund's performance. During the most recent fiscal year, the fund's portfolio turnover rate was 55% of the average value of its portfolio.

Principal Investment Strategies

• Normally investing primarily in income producing debt securities, preferred stocks, and convertible securities, with an emphasis on lower-quality debt securities, of U.S. and non-U.S. issuers, including emerging market countries.
• Potentially investing in non-income producing securities, including defaulted securities and common stocks.
• Investing in companies in troubled or uncertain financial condition.
• Allocating investments across different countries and regions.
• Investing in securities issued throughout the world, including potentially significant investments in U.S. issuers.
• Using a base neutral mix of approximately 60% U.S. high yield, 20% emerging markets debt, 15% European high yield, and 5% Asian high yield.
• Adjusting allocation among markets within the following ranges: U.S. high yield (40%-80%); emerging markets debt (5%-35%); European high yield (0%-30%); and Asian high yield (0%-10%).
• Analyzing an issuer using fundamental factors (e.g., financial condition, earnings outlook, and strategy) and evaluating each security's current price relative to estimated long-term value to select investments.

Principal Investment Risks

• Stock Market Volatility. Stock markets are volatile and can decline significantly in response to adverse issuer, political, regulatory, market, or economic developments. Different parts of the market, including different market sectors, and different types of securities can react differently to these developments.
• Interest Rate Changes. Interest rate increases can cause the price of a debt security to decrease.
• Foreign Exposure. Foreign markets, particularly emerging 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. Emerging markets can be subject to greater social, economic, regulatory, and political uncertainties and can be extremely volatile. Foreign exchange rates also can be extremely volatile.
• 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, also referred to as high yield debt securities) and certain types of other securities involve greater risk of default or price changes due to changes in the credit quality of the issuer. The value of lower-quality debt securities and certain types of other securities can be more volatile due to increased sensitivity to adverse issuer, political, regulatory, market, or economic developments and can be difficult to resell.

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.

Performance

The following information is intended to help you understand the risks of investing in the fund. The information illustrates the performance of the fund's shares over the past year and compares the performance of the fund's shares to the performance of a securities market index and a hypothetical composite of market indexes over various periods of time. The indexes have characteristics relevant to the fund's investment strategies. Index descriptions appear in the Additional Information about the Indexes 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.

Year-by-Year Returns

The returns in the bar chart do not reflect any applicable sales charges; if sales charges were reflected, returns would be lower than those shown.

Calendar Year

During the period shown in the chart for Class A:	Returns	Quarter ended
Highest Quarter Return	5.88%	March 31, 2012
Lowest Quarter Return	0.75%	June 30, 2012
Year-to-Date Return	1.41%	March 31, 2013

Average Annual Returns

Unlike the returns in the bar chart, the returns in the table reflect the maximum applicable sales charges. 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. After-tax returns for Class A are shown in the table below and after-tax returns for other classes will vary. 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

Average Annual Total Returns A T C Fidelity Global High Income Fund	Past 1 year	Life of class		Inception Date
Class A Return Before Taxes	11.97%	3.94%	[1]	May 11, 2011
Class A Return After Taxes on Distributions	9.91%	2.15%	[1]	May 11, 2011
Class A Return After Taxes on Distributions and Sale of Fund Shares	7.70%	2.29%	[1]	May 11, 2011
Class T Return Before Taxes	11.95%	3.93%	[1]	May 11, 2011
Class C Return Before Taxes	14.73%	5.74%	[1]	May 11, 2011
The BofA Merrill Lynch℠ Global High Yield and Emerging Markets Plus Index (reflects no deduction for fees, expenses, or taxes)	19.74%	9.89%	[1]	May 11, 2011
Fidelity Global High Income Composite Index℠ (reflects no deduction for fees, expenses, or taxes)	18.79%	9.01%	[1]	May 11, 2011

[1] Class A and Class T purchases of $1 million or more will not be subject to a front-end sales charge. Such Class A and Class T purchases may be subject, upon redemption, to a contingent deferred sales charge (CDSC) of 1.00% or 0.25%, respectively.

[2] On Class C shares redeemed less than one year after purchase.

[1] From May 11, 2011.

XML

Fidelity High Income Fund

Fund Summary

Fund:
Fidelity^®High Income Fund

Investment Objective

The fund seeks a high level of current income. Growth of capital may also be considered.

Fee Table

The following table describes the fees and expenses that may be incurred when you buy and hold shares of the fund.

Shareholder fees
(fees paid directly from your investment)

Shareholder Fees	Fidelity High Income Fund Class: Fidelity High Income Fund
Redemption fee on shares held less than 90 days (as a % of amount redeemed)	1.00%

Annual fund operating expenses
(expenses that you pay each year as a % of the value of your investment)

Annual Fund Operating Expenses	Fidelity High Income Fund Class: Fidelity High Income Fund
Management fee	0.56%
Distribution and/or Service (12b-1) fees	none
Other expenses	0.16%
Total annual fund operating expenses	0.72%

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:

Expense Example (USD $)	Fidelity High Income Fund Class: Fidelity High Income Fund
1 year	74
3 years	230
5 years	401
10 years	894

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 operating expenses or in the example, affect the fund's performance. During the most recent fiscal year, the fund's portfolio turnover rate was 44% of the average value of its portfolio.

Principal Investment Strategies

• Normally investing primarily in income producing debt securities, preferred stocks, and convertible securities, with an emphasis on lower-quality debt securities.
• Potentially investing in non-income producing securities, including defaulted securities and common stocks.
• Investing in companies in troubled or uncertain financial condition.
• Managing the fund to have similar credit quality distribution to an index representing the overall high yield bond market, which as of April 30, 2013, was The BofA Merrill Lynch^SM US High Yield Constrained Index.
• 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.

Principal Investment Risks

• Stock Market Volatility. Stock markets are volatile and can decline significantly in response to adverse issuer, political, regulatory, market, or economic developments. Different parts of the market, including different market sectors, and different types of securities can react differently to these developments.
• Interest Rate Changes. Interest rate increases can cause the price of a debt security to decrease.
• Foreign Exposure. Foreign markets, particularly emerging 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.
• 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, also referred to as high yield debt securities) and certain types of other securities involve greater risk of default or price changes due to changes in the credit quality of the issuer. The value of lower-quality debt securities and certain types of other securities can be more volatile due to increased sensitivity to adverse issuer, political, regulatory, market, or economic developments and can be difficult to resell.

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.

Performance

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 Information about the Indexes section of the prospectus. Past performance (before and after taxes) is not an indication of future performance.

Visit www.fidelity.com for updated return information.

Year-by-Year Returns
Calendar Years

During the periods shown in the chart:	Returns	Quarter ended
Highest Quarter Return	19.53%	June 30, 2009
Lowest Quarter Return	-18.16%	December 31, 2008
Year-to-Date Return	2.88%	March 31, 2013

Average Annual Returns

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.

For the periods ended
December 31, 2012

Average Annual Total Returns Fidelity High Income Fund	Past 1 year	Past 5 years	Past 10 years
Class: Fidelity High Income Fund Return Before Taxes	14.89%	9.32%	9.86%
Class: Fidelity High Income Fund Return After Taxes on Distributions	12.47%	6.57%	7.08%
Class: Fidelity High Income Fund Return After Taxes on Distributions and Sale of Fund Shares	9.60%	6.29%	6.83%
The BofA Merrill Lynch℠ US High Yield Constrained Index (reflects no deduction for fees, expenses, or taxes)	15.55%	10.14%	10.38%

XML

F | Fidelity Series High Income Fund

Fund Summary

Fund/Class:
Fidelity^®Series High Income Fund/F

Investment Objective

The fund seeks a high level of current income. Growth of capital may also be considered.

Fee Table

The following table describes the fees and expenses that may be incurred when you buy and hold shares of the fund.

Shareholder fees
(fees paid directly from your investment)

Shareholder Fees (USD $)	F Fidelity Series High Income Fund Class F
Shareholder fees (fees paid directly from your investment)	none

Annual class operating expenses
(expenses that you pay each year as a % of the value of your investment)

Annual Class Operating Expenses	F Fidelity Series High Income Fund Class F
Management fee	0.57%
Distribution and/or Service (12b-1) fees	none
Other expenses	0.01%
Total annual operating expenses	0.58%

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:

Expense Example (USD $)	F Fidelity Series High Income Fund Class F
1 year	59
3 years	186
5 years	324
10 years	726

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 operating expenses or in the example, affect the fund's performance. During the most recent fiscal year, the fund's portfolio turnover rate was 45% of the average value of its portfolio.

Principal Investment Strategies

• Normally investing primarily in income producing debt securities, preferred stocks, and convertible securities, with an emphasis on lower-quality debt securities.
• Potentially investing in non-income producing securities, including defaulted securities and common stocks.
• Investing in companies in troubled or uncertain financial condition.
• Managing the fund to have similar credit quality distribution to an index representing the overall high yield bond market, which as of April 30, 2013, was The BofA Merrill Lynch^SM US High Yield Constrained Index.
• 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.

Principal Investment Risks

• Stock Market Volatility. Stock markets are volatile and can decline significantly in response to adverse issuer, political, regulatory, market, or economic developments. Different parts of the market, including different market sectors, and different types of securities can react differently to these developments.
• Interest Rate Changes. Interest rate increases can cause the price of a debt security to decrease.
• Foreign Exposure. Foreign markets, particularly emerging 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.
• 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, also referred to as high yield debt securities) and certain types of other securities involve greater risk of default or price changes due to changes in the credit quality of the issuer. The value of lower-quality debt securities and certain types of other securities can be more volatile due to increased sensitivity to adverse issuer, political, regulatory, market, or economic developments and can be difficult to resell.

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.

Performance

The following information is intended to help you understand the risks of investing in the fund. The information illustrates the performance of the fund's shares over the past 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 Information about the Index section of the prospectus. Past performance (before and after taxes) is not an indication of future performance.

Visit www.401k.com and log in for updated return information.

Year-by-Year Returns
Calendar Year

During the period shown in the chart:	Returns	Quarter ended
Highest Quarter Return	6.12%	March 31, 2012
Lowest Quarter Return	1.36%	June 30, 2012
Year-to-Date Return	2.99%	March 31, 2013

Average Annual Returns

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.

For the periods ended
December 31, 2012

Average Annual Total Returns F Fidelity Series High Income Fund	Past 1 year	Life of class		Inception Date
Class F Return Before Taxes	15.86%	8.17%	[1]	Mar. 10, 2011
Class F Return After Taxes on Distributions	13.48%	5.92%	[1]	Mar. 10, 2011
Class F Return After Taxes on Distributions and Sale of Fund Shares	10.22%	5.61%	[1]	Mar. 10, 2011
The BofA Merrill Lynch℠ US High Yield Constrained Index (reflects no deduction for fees, expenses, or taxes)	15.55%	8.76%	[1]	Mar. 10, 2011

[1] From March 10, 2011.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	FIDELITY SUMMER STREET TRUST
Prospectus Date	rr_ProspectusDate	Jun. 29, 2013
Document Creation Date	dei_DocumentCreationDate	Jun. 27, 2013

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

FIDELITY SUMMER STREET TRUST

Prospectus Date

rr_ProspectusDate

Jun. 29, 2013

Fidelity Focused High Income Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

Fund Summary

Fund:
Fidelity^®Focused High Income Fund

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The fund seeks a high level of income. The fund may also seek capital appreciation.

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 fund 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 47% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

47.00%

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 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:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

• Normally investing primarily in income producing debt securities, preferred stocks, and convertible securities, with an emphasis on lower-quality debt securities.
• Normally investing primarily in securities rated BB by Standard & Poor's (S&P), Ba by Moody's Investors Service (Moody's), comparably rated by at least one nationally recognized credit rating agency, or, if unrated, considered by Fidelity Management & Research Company (FMR) to be of comparable quality.
• Potentially investing in securities that have a higher or lower credit quality.
• Potentially investing in non-income producing securities, including defaulted securities and common stocks.
• Investing in companies in troubled or uncertain financial condition.
• 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_RiskHeading

Principal Investment Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

• Stock Market Volatility. Stock markets are volatile and can decline significantly in response to adverse issuer, political, regulatory, market, or economic developments. Different parts of the market, including different market sectors, and different types of securities can react differently to these developments.
• Interest Rate Changes. Interest rate increases can cause the price of a debt security to decrease.
• Foreign Exposure. Foreign markets, particularly emerging 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.
• 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, also referred to as high yield debt securities) and certain types of other securities involve greater risk of default or price changes due to changes in the credit quality of the issuer. The value of lower-quality debt securities and certain types of other securities can be more volatile due to increased sensitivity to adverse issuer, political, regulatory, market, or economic developments and can be difficult to resell.

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 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 Information about the Indexes section of the prospectus. Past performance (before and after taxes) is not an indication of future performance.

Visit www.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.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	10.91%	June 30, 2009
Lowest Quarter Return	-14.61%	December 31, 2008
Year-to-Date Return	1.77%	March 31, 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

Fidelity Focused High Income Fund | Class: Fidelity Focused High Income Fund

Risk/Return:

rr_RiskReturnAbstract

Redemption fee on shares held less than 90 days (as a % of amount redeemed)

rr_RedemptionFeeOverRedemption

1.00%

Management fee

rr_ManagementFeesOverAssets

0.56%

Distribution and/or Service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.25%

Total annual fund operating expenses

rr_ExpensesOverAssets

0.81%

1 year

rr_ExpenseExampleYear01

$ 83

3 years

rr_ExpenseExampleYear03

259

5 years

rr_ExpenseExampleYear05

450

10 years

rr_ExpenseExampleYear10

$ 1,002

2005

rr_AnnualReturn2005

2.81%

2006

rr_AnnualReturn2006

8.50%

2007

rr_AnnualReturn2007

3.09%

2008

rr_AnnualReturn2008

(20.50%)

2009

rr_AnnualReturn2009

35.07%

2010

rr_AnnualReturn2010

12.05%

2011

rr_AnnualReturn2011

5.87%

2012

rr_AnnualReturn2012

11.69%

Year to Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date Return

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2013

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

1.77%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter Return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

10.91%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter Return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(14.61%)

Fidelity Focused High Income Fund | Return Before Taxes | Class: Fidelity Focused High Income Fund

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity Focused High Income Fund

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

Past 1 year

rr_AverageAnnualReturnYear01

11.69%

Past 5 years

rr_AverageAnnualReturnYear05

7.30%

Life of fund

rr_AverageAnnualReturnSinceInception

6.59%

^[1]

Inception Date

rr_AverageAnnualReturnInceptionDate

Sep. 08, 2004

Fidelity Focused High Income Fund | Return After Taxes on Distributions | Class: Fidelity Focused High Income Fund

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity Focused High Income Fund

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

Past 1 year

rr_AverageAnnualReturnYear01

9.42%

Past 5 years

rr_AverageAnnualReturnYear05

4.48%

Life of fund

rr_AverageAnnualReturnSinceInception

4.06%

^[1]

Inception Date

rr_AverageAnnualReturnInceptionDate

Sep. 08, 2004

Fidelity Focused High Income Fund | Return After Taxes on Distributions and Sale of Fund Shares | Class: Fidelity Focused High Income Fund

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity Focused High Income Fund

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

Past 1 year

rr_AverageAnnualReturnYear01

7.68%

Past 5 years

rr_AverageAnnualReturnYear05

4.58%

Life of fund

rr_AverageAnnualReturnSinceInception

4.14%

^[1]

Inception Date

rr_AverageAnnualReturnInceptionDate

Sep. 08, 2004

Fidelity Focused High Income Fund | The BofA Merrill Lynch℠ BB US High Yield Constrained Index (reflects no deduction for fees, expenses, or taxes)

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

The BofA Merrill Lynch^SM BB US High Yield Constrained Index

Past 1 year

rr_AverageAnnualReturnYear01

13.96%

Past 5 years

rr_AverageAnnualReturnYear05

10.18%

Life of fund

rr_AverageAnnualReturnSinceInception

8.30%

^[1]

Inception Date

rr_AverageAnnualReturnInceptionDate

Sep. 08, 2004

[1] From September 8, 2004.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

FIDELITY SUMMER STREET TRUST

Prospectus Date

rr_ProspectusDate

Jun. 29, 2013

Fidelity High Income Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

Fund Summary

Fund:
Fidelity^®High Income Fund

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The fund seeks a high level of current income. Growth of capital may also be considered.

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 fund 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 44% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

44.00%

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 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:

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

• Normally investing primarily in income producing debt securities, preferred stocks, and convertible securities, with an emphasis on lower-quality debt securities.
• Potentially investing in non-income producing securities, including defaulted securities and common stocks.
• Investing in companies in troubled or uncertain financial condition.
• Managing the fund to have similar credit quality distribution to an index representing the overall high yield bond market, which as of April 30, 2013, was The BofA Merrill Lynch^SM US High Yield Constrained Index.
• 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_RiskHeading

Principal Investment Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

• Stock Market Volatility. Stock markets are volatile and can decline significantly in response to adverse issuer, political, regulatory, market, or economic developments. Different parts of the market, including different market sectors, and different types of securities can react differently to these developments.
• Interest Rate Changes. Interest rate increases can cause the price of a debt security to decrease.
• Foreign Exposure. Foreign markets, particularly emerging 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.
• 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, also referred to as high yield debt securities) and certain types of other securities involve greater risk of default or price changes due to changes in the credit quality of the issuer. The value of lower-quality debt securities and certain types of other securities can be more volatile due to increased sensitivity to adverse issuer, political, regulatory, market, or economic developments and can be difficult to resell.

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 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 Information about the Indexes section of the prospectus. Past performance (before and after taxes) is not an indication of future performance.

Visit www.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.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	19.53%	June 30, 2009
Lowest Quarter Return	-18.16%	December 31, 2008
Year-to-Date Return	2.88%	March 31, 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 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.

For the periods ended
December 31, 2012

Fidelity High Income Fund | Class: Fidelity High Income Fund

Risk/Return:

rr_RiskReturnAbstract

Redemption fee on shares held less than 90 days (as a % of amount redeemed)

rr_RedemptionFeeOverRedemption

1.00%

Management fee

rr_ManagementFeesOverAssets

0.56%

Distribution and/or Service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.16%

Total annual fund operating expenses

rr_ExpensesOverAssets

0.72%

1 year

rr_ExpenseExampleYear01

$ 74

3 years

rr_ExpenseExampleYear03

230

5 years

rr_ExpenseExampleYear05

401

10 years

rr_ExpenseExampleYear10

$ 894

2003

rr_AnnualReturn2003

27.48%

2004

rr_AnnualReturn2004

9.69%

2005

rr_AnnualReturn2005

3.45%

2006

rr_AnnualReturn2006

10.74%

2007

rr_AnnualReturn2007

2.36%

2008

rr_AnnualReturn2008

(23.72%)

2009

rr_AnnualReturn2009

51.46%

2010

rr_AnnualReturn2010

13.73%

2011

rr_AnnualReturn2011

3.41%

2012

rr_AnnualReturn2012

14.89%

Year to Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date Return

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2013

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

2.88%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter Return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

19.53%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter Return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(18.16%)

Fidelity High Income Fund | Return Before Taxes | Class: Fidelity High Income Fund

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity High Income Fund

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

Past 1 year

rr_AverageAnnualReturnYear01

14.89%

Past 5 years

rr_AverageAnnualReturnYear05

9.32%

Past 10 years

rr_AverageAnnualReturnYear10

9.86%

Fidelity High Income Fund | Return After Taxes on Distributions | Class: Fidelity High Income Fund

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity High Income Fund

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

Past 1 year

rr_AverageAnnualReturnYear01

12.47%

Past 5 years

rr_AverageAnnualReturnYear05

6.57%

Past 10 years

rr_AverageAnnualReturnYear10

7.08%

Fidelity High Income Fund | Return After Taxes on Distributions and Sale of Fund Shares | Class: Fidelity High Income Fund

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity High Income Fund

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

Past 1 year

rr_AverageAnnualReturnYear01

9.60%

Past 5 years

rr_AverageAnnualReturnYear05

6.29%

Past 10 years

rr_AverageAnnualReturnYear10

6.83%

Fidelity High Income Fund | The BofA Merrill Lynch℠ US High Yield Constrained Index (reflects no deduction for fees, expenses, or taxes)

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

The BofA Merrill Lynch^SM US High Yield Constrained Index

Past 1 year

rr_AverageAnnualReturnYear01

15.55%

Past 5 years

rr_AverageAnnualReturnYear05

10.14%

Past 10 years

rr_AverageAnnualReturnYear10

10.38%

XML

Document and Entity Information	12 Months Ended
	Jun. 29, 2013
Risk/Return:
Document Type	485BPOS
Document Period End Date	Apr. 30, 2013
Registrant Name	FIDELITY SUMMER STREET TRUST
Central Index Key	0000225322
Amendment Flag	false
Document Creation Date	Jun. 27, 2013
Document Effective Date	Jun. 29, 2013
Prospectus Date	Jun. 29, 2013