485BPOS

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
FORM N-1A
REGISTRATION STATEMENT (No. 002-41839)
		UNDER THE SECURITIES ACT OF 1933	[X]
		Pre-Effective Amendment No. ____	[ ]
		Post-Effective Amendment No. 206	[X]
and
REGISTRATION STATEMENT (No. 811-02105)
		UNDER THE INVESTMENT COMPANY ACT OF 1940	[X]
		Amendment No. 206	[X]
Fidelity Salem Street Trust
(Exact Name of Registrant as Specified in Charter)
82 Devonshire St., Boston, Massachusetts 02109
(Address Of Principal Executive Offices) (Zip Code)
Registrant's Telephone Number: 617-563-7000
Scott C. Goebel, Secretary
82 Devonshire Street
Boston, Massachusetts 02109
(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. 206 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 19th day of October 2012.

	Fidelity Salem Street Trust
	By	/s/John R. Hebble
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||		John R. Hebble, 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/John R. Hebble		President and Treasurer	October 19, 2012
John R. Hebble		(Principal Executive Officer)
/s/Christine Reynolds		Chief Financial Officer	October 19, 2012
Christine Reynolds		(Principal Financial Officer)
/s/Abigail P. Johnson		Trustee	October 19, 2012
Abigail P. Johnson
/s/James C. Curvey	*	Trustee	October 19, 2012
James C. Curvey
/s/Albert R. Gamper	*	Trustee	October 19, 2012
Albert R. Gamper
/s/Robert F. Gartland	*	Trustee	October 19, 2012
Robert F. Gartland
/s/Arthur E. Johnson	*	Trustee	October 19, 2012
Arthur E. Johnson
/s/Michael E. Kenneally	*	Trustee	October 19, 2012
Michael E. Kenneally
/s/James H. Keyes	*	Trustee	October 19, 2012
James H. Keyes
/s/Marie L. Knowles	*	Trustee	October 19, 2012
Marie L. Knowles
/s/Kenneth L. Wolfe	*	Trustee	October 19, 2012
Kenneth L. Wolfe

*	By:	/s/Joseph R. Fleming
		Joseph R. Fleming, pursuant to a power of attorney dated February 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 Aberdeen Street Trust Fidelity Advisor Series II Fidelity Advisor Series IV Fidelity Boylston Street Trust Fidelity California Municipal Trust Fidelity California Municipal Trust II Fidelity Central Investment Portfolios II LLC Fidelity Charles Street Trust Fidelity Colchester Street Trust Fidelity Court Street Trust Fidelity Court Street Trust II Fidelity Fixed-Income Trust Fidelity Garrison Street Trust Fidelity Hereford Street Trust Fidelity Income Fund   Fidelity Massachusetts Municipal Trust Fidelity Money Market Trust Fidelity Municipal Trust Fidelity Municipal Trust II Fidelity Newbury Street Trust Fidelity New York Municipal Trust Fidelity New York Municipal Trust II Fidelity Oxford Street Trust Fidelity Phillips Street Trust Fidelity Revere Street Trust Fidelity School Street Trust Fidelity Union Street Trust Fidelity Union Street Trust II Variable Insurance Products Fund V

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 February 1, 2011.

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

/s/James C. Curvey	/s/Michael E. Kenneally
James C. Curvey	Michael E. Kenneally
/s/Albert R. Gamper, Jr.	/s/James H. Keyes
Albert R. Gamper, Jr.	James H. Keyes
/s/Robert F. Gartland	/s/Marie L. Knowles
Robert F. Gartland	Marie L. Knowles
/s/Arthur E. Johnson	/s/Kenneth L. Wolfe
Arthur E. Johnson	Kenneth L. Wolfe

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	FIDELITY SALEM STREET TRUST
Prospectus Date	rr_ProspectusDate	Sep. 29, 2012
Document Creation Date	dei_DocumentCreationDate	Sep. 27, 2012

XML

Series | Fidelity Series Commodity Strategy Fund

Fund Summary

Fund/Class:
Fidelity^® Series Commodity Strategy Fund/Fidelity Series Commodity Strategy Fund

Investment Objective

The fund seeks to provide investment returns that correspond to the performance of the commodities market.

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 Commodity Strategy Fund Class: Fidelity Series Commodity Strategy 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 Commodity Strategy Fund Class: Fidelity Series Commodity Strategy Fund
Management fee		0.40%
Distribution and/or Service (12b-1) fees		none
Other expenses		0.20%
Acquired fund fees and expenses	[1]	0.04%
Total annual operating expenses		0.64%
Fee waiver and/or expense reimbursement	[1]	0.04%
Total annual operating expenses after fee waiver and/or expense reimbursement		0.60%

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 Commodity Strategy Fund Class: Fidelity Series Commodity Strategy Fund
1 year	61
3 years	192
5 years	335
10 years	750

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 148% of the average value of its portfolio.

Principal Investment Strategies

• Normally investing in commodity-linked notes, other commodity-linked derivative instruments, short-term investment-grade debt securities, cash, and cash equivalents.
• Investing up to 25% of assets in a wholly-owned subsidiary that invests in commodity-linked total return swaps based on the value of commodities or commodities indices and in other commodity-linked derivative instruments.
• Managing the fund to track an index chosen to represent the commodities market, as well as short-term investment-grade debt securities, which as of July 31, 2012 was the Dow Jones-UBS Commodity Index Total Return^SM.
• Investing in domestic and foreign issuers.
• Engaging in commodity-linked derivatives transactions that have a leveraging effect on the fund.
• Investing in Fidelity's central funds (specialized investment vehicles used by Fidelity funds to invest in particular security types or investment disciplines).

Principal Investment Risks

• Interest Rate Changes. Interest rate increases can cause the price of a debt security to decrease.
• Foreign Exposure. Foreign markets can be more volatile than the U.S. market due to increased risks of adverse issuer, political, regulatory, market, or economic developments and can perform differently from the U.S. market.
• Financial Services Exposure. Changes in government regulation and interest rates and economic downturns can have a significant negative effect on issuers in the financial services sector, including the price of their securities or their ability to meet their payment obligations.
• Subsidiary Risk. Investment in an unregistered subsidiary is not subject to the investor protections of the Investment Company Act of 1940 (1940 Act) and is subject to the risks associated with investing in derivatives and commodity-linked investing in general. Changes in tax and other laws could negatively affect investments in the subsidiary.
• Prepayment. The ability of an issuer of a debt security to repay principal prior to a security's maturity can cause greater price volatility if interest rates change.
• Issuer-Specific Changes. The value of an individual security or particular type of security can be more volatile than, and can perform differently from, the market as a whole. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a security to decrease.
• Leverage Risk. Leverage can increase market exposure, magnify investment risks, and cause losses to be realized more quickly.
• Commodity-Linked Investing. Commodity-linked investments may be more volatile and less liquid than the underlying commodity, instruments, or measures and their value may be affected by the performance of the overall commodities markets as well as weather, political, tax, and other regulatory and market developments.

In addition, the fund is considered non-diversified and can invest a greater portion of assets in securities of a smaller number of individual issuers than a diversified fund. As a result, changes in the market value of a single investment could cause greater fluctuations in share price than would occur in a more diversified fund.

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 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 Years

During the periods shown in the chart:	Returns	Quarter ended
Highest Quarter Return	15.54%	December 31, 2010
Lowest Quarter Return	-11.72%	September 30, 2011
Year-to-Date Return	-4.02%	June 30, 2012

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, 2011

Average Annual Total Returns Series Fidelity Series Commodity Strategy Fund	Past 1 Year	Life of class		Inception Date
Class: Fidelity Series Commodity Strategy Fund Return Before Taxes	(13.89%)	4.51%	[1]	Oct. 01, 2009
Class: Fidelity Series Commodity Strategy Fund Return After Taxes on Distributions	(18.92%)	1.52%	[1]	Oct. 01, 2009
Class: Fidelity Series Commodity Strategy Fund Return After Taxes on Distributions and Sale of Fund Shares	(8.22%)	2.50%	[1]	Oct. 01, 2009
Dow Jones-UBS Commodity Index Total Return (reflects no deduction for fees, expenses, or taxes)	(13.32%)	5.33%	[1]	Oct. 01, 2009

[1] The fund may invest in a wholly-owned subsidiary. The subsidiary has entered into a separate contract with Fidelity Management & Research Company (FMR) for the management of its portfolio pursuant to which the subsidiary pays FMR a fee at an annual rate of 0.30% of its net assets. The subsidiary also pays certain other expenses including custody fees. FMR has contractually agreed to waive the fund's management fee in an amount equal to the management fee paid to FMR by the subsidiary. The fund also may invest in Fidelity Commodity Strategy Central Fund, which in turn invests in its own wholly-owned subsidiary that invests in commodity-linked derivative instruments. FMR has contractually agreed to waive the fund's management fee in an amount equal to its proportionate share of the management fee paid to FMR by the central fund's subsidiary based on the fund's proportionate ownership of the central fund. These arrangements will remain in effect for at least one year from the effective date of the prospectus, and will remain in effect thereafter as long as FMR's contract with the applicable subsidiary is in place. If FMR's contract with a subsidiary is terminated, FMR, in its sole discretion, may discontinue the arrangement.

[1] From October 1, 2009.

XML

Inst | Spartan Real Estate Index Fund

Fund Summary

Fund/Class:
Spartan^® Real Estate Index Fund/Institutional

Investment Objective

The fund seeks to provide investment results that correspond to the total return of equity REITs and other real estate-related investments.

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 Spartan Real Estate Index Fund Institutional Class
Redemption fee on shares held less than 90 days (as a % of amount redeemed)	0.75%

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

Annual Class Operating Expenses		Inst Spartan Real Estate Index Fund Institutional Class
Management fee		0.14%
Distribution and/or Service (12b-1) fees		none
Other expenses		0.02%
Total annual operating expenses	[1]	0.16%
Fee waiver and/or expense reimbursement	[2]	0.07%
Total annual operating expenses after fee waiver and/or expense reimbursement	[1]	0.09%

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 Spartan Real Estate Index Fund Institutional Class
1 year	9
3 years	43
5 years	82
10 years	196

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. For the period from September 8, 2011 to July 31, 2012, the fund's portfolio turnover rate was 67% of the average value of its portfolio.

Principal Investment Strategies

• Normally investing at least 80% of assets in securities included in the Dow Jones U.S. Select Real Estate Securities Index^SM (the Index).
• Lending securities to earn income for the fund.

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 can react differently to these developments.
• Real Estate Industry Concentration. Changes in real estate values or economic downturns can have a significant negative effect on issuers in the real estate industry.
• 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.
• Correlation to Index. The performance of the fund and its index may vary somewhat due to factors such as transaction costs, sample selection, and timing differences associated with additions to and deletions from its index.

In addition, the fund is considered non-diversified and can invest a greater portion of assets in securities of a smaller number of individual issuers than a diversified fund. As a result, changes in the market value of a single investment could cause greater fluctuations in share price than would occur in a more diversified fund.

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

Performance history will be available for the fund after the fund has been in operation for one calendar year.

[1] Differs from the ratios of expenses to average net assets in the Financial Highlights section of the prospectus because of acquired fund fees and expenses. For the period, acquired fund fees and expenses are less than 0.01% and are included in other expenses. As a result, the total annual operating expenses after fee waiver and/or expense reimbursement in the fee table exceed the contractual expense limitations of the fund.

[2] Fidelity Management & Research Company (FMR) has contractually agreed to reimburse Institutional Class of the fund to the extent that total operating expenses (excluding interest, taxes, certain securities lending costs, brokerage commissions, extraordinary expenses, and acquired fund fees and expenses, if any), as a percentage of its average net assets, exceed 0.08%. This arrangement will remain in effect through September 30, 2013, after which date FMR, in its sole discretion, may discontinue the arrangement at any time.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Prospectus Date

rr_ProspectusDate

Sep. 29, 2012

Registrant Name

dei_EntityRegistrantName

FIDELITY SALEM STREET TRUST

Fidelity Commodity Strategy Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

Fund Summary

Fund:
Fidelity^® Commodity Strategy Fund

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The fund seeks to provide investment returns that correspond to the performance of the commodities market.

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)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

at least one year from the effective date of the prospectus

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when fund shares are held in a taxable account. These costs, which are not reflected in annual operating expenses or in the example, affect the fund's performance. During the most recent fiscal year, the fund's portfolio turnover rate was 0% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

0.00%

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 in commodity-linked notes, other commodity-linked derivative instruments, short-term investment-grade debt securities, cash, and cash equivalents.
• Investing up to 25% of assets in a wholly-owned subsidiary that invests in commodity-linked total return swaps based on the value of commodities or commodities indices and in other commodity-linked derivative instruments.
• Managing the fund to track an index chosen to represent the commodities market, as well as short-term investment-grade debt securities, which as of July 31, 2012 was the Dow Jones-UBS Commodity Index Total Return^SM.
• Investing in domestic and foreign issuers.
• Engaging in commodity-linked derivatives transactions that have a leveraging effect on the fund.
• Investing in Fidelity's central funds (specialized investment vehicles used by Fidelity funds to invest in particular security types or investment disciplines).

Risk [Heading]

rr_RiskHeading

Principal Investment Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

• Interest Rate Changes. Interest rate increases can cause the price of a debt security to decrease.
• Foreign Exposure. Foreign markets can be more volatile than the U.S. market due to increased risks of adverse issuer, political, regulatory, market, or economic developments and can perform differently from the U.S. market.
• Financial Services Exposure. Changes in government regulation and interest rates and economic downturns can have a significant negative effect on issuers in the financial services sector, including the price of their securities or their ability to meet their payment obligations.
• Subsidiary Risk. Investment in an unregistered subsidiary is not subject to the investor protections of the Investment Company Act of 1940 (1940 Act) and is subject to the risks associated with investing in derivatives and commodity-linked investing in general. Changes in tax and other laws could negatively affect investments in the subsidiary.
• Prepayment. The ability of an issuer of a debt security to repay principal prior to a security's maturity can cause greater price volatility if interest rates change.
• Issuer-Specific Changes. The value of an individual security or particular type of security can be more volatile than, and can perform differently from, the market as a whole. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a security to decrease.
• Leverage Risk. Leverage can increase market exposure, magnify investment risks, and cause losses to be realized more quickly.
• Commodity-Linked Investing. Commodity-linked investments may be more volatile and less liquid than the underlying commodity, instruments, or measures and their value may be affected by the performance of the overall commodities markets as well as weather, political, tax, and other regulatory and market developments.

In addition, the fund is considered non-diversified and can invest a greater portion of assets in securities of a smaller number of individual issuers than a diversified fund. As a result, changes in the market value of a single investment could cause greater fluctuations in share price than would occur in a more diversified fund.

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 Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

In addition, the fund is considered non-diversified and can invest a greater portion of assets in securities of a smaller number of individual issuers than a diversified fund. As a result, changes in the market value of a single investment could cause greater fluctuations in share price than would occur in a more diversified 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 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 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	15.50%	December 31, 2010
Lowest Quarter Return	-11.65%	September 30, 2011
Year-to-Date Return	-4.05%	June 30, 2012

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, 2011

Fidelity Commodity Strategy Fund | Class: Fidelity Commodity Strategy Fund

Risk/Return:

rr_RiskReturnAbstract

Shareholder fees (fees paid directly from your investment)

rr_ShareholderFeeOther

none

Management fee

rr_ManagementFeesOverAssets

0.40%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.20%

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.05%

^[1]

Total annual fund operating expenses

rr_ExpensesOverAssets

0.65%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.04%

^[1]

Total annual fund operating expenses after fee waiver and/or expense reimbursement

rr_NetExpensesOverAssets

0.61%

1 year

rr_ExpenseExampleYear01

62

3 years

rr_ExpenseExampleYear03

195

5 years

rr_ExpenseExampleYear05

340

10 years

rr_ExpenseExampleYear10

762

2010

rr_AnnualReturn2010

15.84%

2011

rr_AnnualReturn2011

(13.95%)

Year to Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date Return

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Jun. 30, 2012

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

(4.05%)

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter Return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Dec. 31, 2010

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

15.50%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter Return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2011

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(11.65%)

Fidelity Commodity Strategy Fund | Return Before Taxes | Class: Fidelity Commodity Strategy Fund

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity Commodity Strategy Fund

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

Past 1 Year

rr_AverageAnnualReturnYear01

(13.95%)

Life of fund

rr_AverageAnnualReturnSinceInception

0.89%

^[2]

Inception Date

rr_AverageAnnualReturnInceptionDate

Oct. 20, 2009

Fidelity Commodity Strategy Fund | Return After Taxes on Distributions | Class: Fidelity Commodity Strategy Fund

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity Commodity Strategy Fund

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

Past 1 Year

rr_AverageAnnualReturnYear01

(19.29%)

Life of fund

rr_AverageAnnualReturnSinceInception

(2.01%)

^[2]

Inception Date

rr_AverageAnnualReturnInceptionDate

Oct. 20, 2009

Fidelity Commodity Strategy Fund | Return After Taxes on Distributions and Sale of Fund Shares | Class: Fidelity Commodity Strategy Fund

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity Commodity Strategy Fund

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

Past 1 Year

rr_AverageAnnualReturnYear01

(8.56%)

Life of fund

rr_AverageAnnualReturnSinceInception

(0.61%)

^[2]

Inception Date

rr_AverageAnnualReturnInceptionDate

Oct. 20, 2009

Fidelity Commodity Strategy Fund | Dow Jones-UBS Commodity Index Total Return (reflects no deduction for fees, expenses, or taxes)

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Dow Jones-UBS Commodity Index Total Return^SM

Past 1 Year

rr_AverageAnnualReturnYear01

(13.32%)

Life of fund

rr_AverageAnnualReturnSinceInception

1.70%

^[2]

Inception Date

rr_AverageAnnualReturnInceptionDate

Oct. 20, 2009

[1] The fund may invest in a wholly-owned subsidiary. The subsidiary has entered into a separate contract with Fidelity Management & Research Company (FMR) for the management of its portfolio pursuant to which the subsidiary pays FMR a fee at an annual rate of 0.30% of its net assets. The subsidiary also pays certain other expenses including custody fees. FMR has contractually agreed to waive the fund's management fee in an amount equal to the management fee paid to FMR by the subsidiary. This arrangement will remain in effect for at least one year from the effective date of the prospectus, and will remain in effect thereafter as long as FMR's contract with the subsidiary is in place. If FMR's contract with the subsidiary is terminated, FMR, in its sole discretion, may discontinue the arrangement.

[2] From October 20, 2009.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	FIDELITY SALEM STREET TRUST
Prospectus Date	rr_ProspectusDate	Sep. 29, 2012
Inst | Spartan Real Estate Index Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Fund Summary Fund/Class: Spartan® Real Estate Index Fund/Institutional
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The fund seeks to provide investment results that correspond to the total return of equity REITs and other real estate-related investments.
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)
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	September 30, 2013
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. For the period from September 8, 2011 to July 31, 2012, the fund's portfolio turnover rate was 67% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	67.00%
Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]	rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees	Differs from the ratios of expenses to average net assets in the Financial Highlights section of the prospectus because of acquired fund fees and expenses.
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 at least 80% of assets in securities included in the Dow Jones U.S. Select Real Estate Securities IndexSM (the Index). Lending securities to earn income for the fund.
Strategy Portfolio Concentration [Text]	rr_StrategyPortfolioConcentration	Normally investing at least 80% of assets in securities included in the Dow Jones U.S. Select Real Estate Securities IndexSM (the Index).
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 can react differently to these developments. Real Estate Industry Concentration. Changes in real estate values or economic downturns can have a significant negative effect on issuers in the real estate industry. 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. Correlation to Index. The performance of the fund and its index may vary somewhat due to factors such as transaction costs, sample selection, and timing differences associated with additions to and deletions from its index. In addition, the fund is considered non-diversified and can invest a greater portion of assets in securities of a smaller number of individual issuers than a diversified fund. As a result, changes in the market value of a single investment could cause greater fluctuations in share price than would occur in a more diversified fund. 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 Nondiversified Status [Text]	rr_RiskNondiversifiedStatus	In addition, the fund is considered non-diversified and can invest a greater portion of assets in securities of a smaller number of individual issuers than a diversified fund. As a result, changes in the market value of a single investment could cause greater fluctuations in share price than would occur in a more diversified 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 One Year or Less [Text]	rr_PerformanceOneYearOrLess	Performance history will be available for the fund after the fund has been in operation for one calendar year.
Inst | Spartan Real Estate Index Fund | Institutional Class
Risk/Return:	rr_RiskReturnAbstract
Redemption fee on shares held less than 90 days (as a % of amount redeemed)	rr_RedemptionFeeOverRedemption	0.75%
Management fee	rr_ManagementFeesOverAssets	0.14%
Distribution and/or Service (12b-1) fees	rr_DistributionAndService12b1FeesOverAssets	none
Other expenses	rr_OtherExpensesOverAssets	0.02%
Total annual operating expenses	rr_ExpensesOverAssets	0.16%	[1]
Fee waiver and/or expense reimbursement	rr_FeeWaiverOrReimbursementOverAssets	0.07%	[2]
Total annual operating expenses after fee waiver and/or expense reimbursement	rr_NetExpensesOverAssets	0.09%	[1]
1 year	rr_ExpenseExampleYear01	9
3 years	rr_ExpenseExampleYear03	43
5 years	rr_ExpenseExampleYear05	82
10 years	rr_ExpenseExampleYear10	196

[1] Differs from the ratios of expenses to average net assets in the Financial Highlights section of the prospectus because of acquired fund fees and expenses. For the period, acquired fund fees and expenses are less than 0.01% and are included in other expenses. As a result, the total annual operating expenses after fee waiver and/or expense reimbursement in the fee table exceed the contractual expense limitations of the fund.

[2] Fidelity Management & Research Company (FMR) has contractually agreed to reimburse Institutional Class of the fund to the extent that total operating expenses (excluding interest, taxes, certain securities lending costs, brokerage commissions, extraordinary expenses, and acquired fund fees and expenses, if any), as a percentage of its average net assets, exceed 0.08%. This arrangement will remain in effect through September 30, 2013, after which date FMR, in its sole discretion, may discontinue the arrangement at any time.

XML

Fidelity Commodity Strategy Fund

Fund Summary

Fund:
Fidelity^® Commodity Strategy Fund

Investment Objective

The fund seeks to provide investment returns that correspond to the performance of the commodities market.

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 $)	Fidelity Commodity Strategy Fund Class: Fidelity Commodity Strategy Fund
Shareholder fees (fees paid directly from your investment)	none

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

Annual Fund Operating Expenses		Fidelity Commodity Strategy Fund Class: Fidelity Commodity Strategy Fund
Management fee		0.40%
Distribution and/or Service (12b-1) fees		none
Other expenses		0.20%
Acquired fund fees and expenses	[1]	0.05%
Total annual fund operating expenses		0.65%
Fee waiver and/or expense reimbursement	[1]	0.04%
Total annual fund operating expenses after fee waiver and/or expense reimbursement		0.61%

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 Commodity Strategy Fund Class: Fidelity Commodity Strategy Fund
1 year	62
3 years	195
5 years	340
10 years	762

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 0% of the average value of its portfolio.

Principal Investment Strategies

• Normally investing in commodity-linked notes, other commodity-linked derivative instruments, short-term investment-grade debt securities, cash, and cash equivalents.
• Investing up to 25% of assets in a wholly-owned subsidiary that invests in commodity-linked total return swaps based on the value of commodities or commodities indices and in other commodity-linked derivative instruments.
• Managing the fund to track an index chosen to represent the commodities market, as well as short-term investment-grade debt securities, which as of July 31, 2012 was the Dow Jones-UBS Commodity Index Total Return^SM.
• Investing in domestic and foreign issuers.
• Engaging in commodity-linked derivatives transactions that have a leveraging effect on the fund.
• Investing in Fidelity's central funds (specialized investment vehicles used by Fidelity funds to invest in particular security types or investment disciplines).

Principal Investment Risks

• Interest Rate Changes. Interest rate increases can cause the price of a debt security to decrease.
• Foreign Exposure. Foreign markets can be more volatile than the U.S. market due to increased risks of adverse issuer, political, regulatory, market, or economic developments and can perform differently from the U.S. market.
• Financial Services Exposure. Changes in government regulation and interest rates and economic downturns can have a significant negative effect on issuers in the financial services sector, including the price of their securities or their ability to meet their payment obligations.
• Subsidiary Risk. Investment in an unregistered subsidiary is not subject to the investor protections of the Investment Company Act of 1940 (1940 Act) and is subject to the risks associated with investing in derivatives and commodity-linked investing in general. Changes in tax and other laws could negatively affect investments in the subsidiary.
• Prepayment. The ability of an issuer of a debt security to repay principal prior to a security's maturity can cause greater price volatility if interest rates change.
• Issuer-Specific Changes. The value of an individual security or particular type of security can be more volatile than, and can perform differently from, the market as a whole. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a security to decrease.
• Leverage Risk. Leverage can increase market exposure, magnify investment risks, and cause losses to be realized more quickly.
• Commodity-Linked Investing. Commodity-linked investments may be more volatile and less liquid than the underlying commodity, instruments, or measures and their value may be affected by the performance of the overall commodities markets as well as weather, political, tax, and other regulatory and market developments.

In addition, the fund is considered non-diversified and can invest a greater portion of assets in securities of a smaller number of individual issuers than a diversified fund. As a result, changes in the market value of a single investment could cause greater fluctuations in share price than would occur in a more diversified fund.

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 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 Years

During the periods shown in the chart:	Returns	Quarter ended
Highest Quarter Return	15.50%	December 31, 2010
Lowest Quarter Return	-11.65%	September 30, 2011
Year-to-Date Return	-4.05%	June 30, 2012

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, 2011

Average Annual Total Returns Fidelity Commodity Strategy Fund	Past 1 Year	Life of fund		Inception Date
Class: Fidelity Commodity Strategy Fund Return Before Taxes	(13.95%)	0.89%	[1]	Oct. 20, 2009
Class: Fidelity Commodity Strategy Fund Return After Taxes on Distributions	(19.29%)	(2.01%)	[1]	Oct. 20, 2009
Class: Fidelity Commodity Strategy Fund Return After Taxes on Distributions and Sale of Fund Shares	(8.56%)	(0.61%)	[1]	Oct. 20, 2009
Dow Jones-UBS Commodity Index Total Return (reflects no deduction for fees, expenses, or taxes)	(13.32%)	1.70%	[1]	Oct. 20, 2009

[1] The fund may invest in a wholly-owned subsidiary. The subsidiary has entered into a separate contract with Fidelity Management & Research Company (FMR) for the management of its portfolio pursuant to which the subsidiary pays FMR a fee at an annual rate of 0.30% of its net assets. The subsidiary also pays certain other expenses including custody fees. FMR has contractually agreed to waive the fund's management fee in an amount equal to the management fee paid to FMR by the subsidiary. This arrangement will remain in effect for at least one year from the effective date of the prospectus, and will remain in effect thereafter as long as FMR's contract with the subsidiary is in place. If FMR's contract with the subsidiary is terminated, FMR, in its sole discretion, may discontinue the arrangement.

[1] From October 20, 2009.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

FIDELITY SALEM STREET TRUST

Prospectus Date

rr_ProspectusDate

Sep. 29, 2012

F | Fidelity Series Commodity Strategy Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

Fund Summary

Fund/Class:
Fidelity^® Series Commodity Strategy Fund/F

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The fund seeks to provide investment returns that correspond to the performance of the commodities market.

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)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

at least one year from the effective date of the prospectus

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when fund shares are held in a taxable account. These costs, which are not reflected in annual operating expenses or in the example, affect the fund's performance. During the most recent fiscal year, the fund's portfolio turnover rate was 148% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

148.00%

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 in commodity-linked notes, other commodity-linked derivative instruments, short-term investment-grade debt securities, cash, and cash equivalents.
• Investing up to 25% of assets in a wholly-owned subsidiary that invests in commodity-linked total return swaps based on the value of commodities or commodities indices and in other commodity-linked derivative instruments.
• Managing the fund to track an index chosen to represent the commodities market, as well as short-term investment-grade debt securities, which as of July 31, 2012 was the Dow Jones-UBS Commodity Index Total Return^SM.
• Investing in domestic and foreign issuers.
• Engaging in commodity-linked derivatives transactions that have a leveraging effect on the fund.
• Investing in Fidelity's central funds (specialized investment vehicles used by Fidelity funds to invest in particular security types or investment disciplines).

Risk [Heading]

rr_RiskHeading

Principal Investment Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

• Interest Rate Changes. Interest rate increases can cause the price of a debt security to decrease.
• Foreign Exposure. Foreign markets can be more volatile than the U.S. market due to increased risks of adverse issuer, political, regulatory, market, or economic developments and can perform differently from the U.S. market.
• Financial Services Exposure. Changes in government regulation and interest rates and economic downturns can have a significant negative effect on issuers in the financial services sector, including the price of their securities or their ability to meet their payment obligations.
• Subsidiary Risk. Investment in an unregistered subsidiary is not subject to the investor protections of the Investment Company Act of 1940 (1940 Act) and is subject to the risks associated with investing in derivatives and commodity-linked investing in general. Changes in tax and other laws could negatively affect investments in the subsidiary.
• Prepayment. The ability of an issuer of a debt security to repay principal prior to a security's maturity can cause greater price volatility if interest rates change.
• Issuer-Specific Changes. The value of an individual security or particular type of security can be more volatile than, and can perform differently from, the market as a whole. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a security to decrease.
• Leverage Risk. Leverage can increase market exposure, magnify investment risks, and cause losses to be realized more quickly.
• Commodity-Linked Investing. Commodity-linked investments may be more volatile and less liquid than the underlying commodity, instruments, or measures and their value may be affected by the performance of the overall commodities markets as well as weather, political, tax, and other regulatory and market developments.

In addition, the fund is considered non-diversified and can invest a greater portion of assets in securities of a smaller number of individual issuers than a diversified fund. As a result, changes in the market value of a single investment could cause greater fluctuations in share price than would occur in a more diversified fund.

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 Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

In addition, the fund is considered non-diversified and can invest a greater portion of assets in securities of a smaller number of individual issuers than a diversified fund. As a result, changes in the market value of a single investment could cause greater fluctuations in share price than would occur in a more diversified 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 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 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.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 Years

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

During the periods shown in the chart:	Returns	Quarter ended
Highest Quarter Return	15.62%	December 31, 2010
Lowest Quarter Return	-11.67%	September 30, 2011
Year-to-Date Return	-3.90%	June 30, 2012

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, 2011

F | Fidelity Series Commodity Strategy Fund | Class F

Risk/Return:

rr_RiskReturnAbstract

Shareholder fees (fees paid directly from your investment)

rr_ShareholderFeeOther

none

Management fee

rr_ManagementFeesOverAssets

0.40%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

none

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.04%

^[1]

Total annual operating expenses

rr_ExpensesOverAssets

0.44%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.04%

^[1]

Total annual operating expenses after fee waiver and/or expense reimbursement

rr_NetExpensesOverAssets

0.40%

1 year

rr_ExpenseExampleYear01

41

3 years

rr_ExpenseExampleYear03

128

5 years

rr_ExpenseExampleYear05

224

10 years

rr_ExpenseExampleYear10

505

2010

rr_AnnualReturn2010

16.23%

2011

rr_AnnualReturn2011

(13.77%)

Year to Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date Return

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Jun. 30, 2012

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

(3.90%)

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter Return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Dec. 31, 2010

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

15.62%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter Return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2011

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(11.67%)

F | Fidelity Series Commodity Strategy 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

(13.77%)

Life of class

rr_AverageAnnualReturnSinceInception

4.69%

^[2]

Inception Date

rr_AverageAnnualReturnInceptionDate

Oct. 01, 2009

F | Fidelity Series Commodity Strategy 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

(18.85%)

Life of class

rr_AverageAnnualReturnSinceInception

1.66%

^[2]

Inception Date

rr_AverageAnnualReturnInceptionDate

Oct. 01, 2009

F | Fidelity Series Commodity Strategy 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

(8.13%)

Life of class

rr_AverageAnnualReturnSinceInception

2.62%

^[2]

Inception Date

rr_AverageAnnualReturnInceptionDate

Oct. 01, 2009

F | Fidelity Series Commodity Strategy Fund | Dow Jones-UBS Commodity Index Total Return (reflects no deduction for fees, expenses, or taxes)

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Dow Jones-UBS Commodity Index Total Return^SM

Past 1 Year

rr_AverageAnnualReturnYear01

(13.32%)

Life of class

rr_AverageAnnualReturnSinceInception

5.33%

^[2]

Inception Date

rr_AverageAnnualReturnInceptionDate

Oct. 01, 2009

[1] The fund may invest in a wholly-owned subsidiary. The subsidiary has entered into a separate contract with Fidelity Management & Research Company (FMR) for the management of its portfolio pursuant to which the subsidiary pays FMR a fee at an annual rate of 0.30% of its net assets. The subsidiary also pays certain other expenses including custody fees. FMR has contractually agreed to waive the fund's management fee in an amount equal to the management fee paid to FMR by the subsidiary. The fund also may invest in Fidelity Commodity Strategy Central Fund, which in turn invests in its own wholly-owned subsidiary that invests in commodity-linked derivative instruments. FMR has contractually agreed to waive the fund's management fee in an amount equal to its proportionate share of the management fee paid to FMR by the central fund's subsidiary based on the fund's proportionate ownership of the central fund. These arrangements will remain in effect for at least one year from the effective date of the prospectus, and will remain in effect thereafter as long as FMR's contract with the applicable subsidiary is in place. If FMR's contract with a subsidiary is terminated, FMR, in its sole discretion, may discontinue the arrangement.

[2] From October 1, 2009.

XML

Document and Entity Information	12 Months Ended
	Sep. 29, 2012
Risk/Return:
Document Type	485BPOS
Document Period End Date	Jul. 31, 2012
Registrant Name	FIDELITY SALEM STREET TRUST
Central Index Key	0000035315
Amendment Flag	false
Document Creation Date	Sep. 27, 2012
Document Effective Date	Sep. 29, 2012
Prospectus Date	Sep. 29, 2012

XML

Adv Inv | Spartan Real Estate Index Fund

Fund Summary

Fund/Class:
Spartan^® Real Estate Index Fund/Investor, Fidelity Advantage^®

Investment Objective

The fund seeks to provide investment results that correspond to the total return of equity REITs and other real estate-related investments.

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 Adv Inv Spartan Real Estate Index Fund (USD $)	Investor Class	Fidelity Advantage Class
Redemption fee on shares held less than 90 days (as a % of amount redeemed)	0.75%	0.75%
Annual index fund fee (for fund balances under $10,000)	10.00	10.00

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

Annual Class Operating Expenses Adv Inv Spartan Real Estate Index Fund		Investor Class	Fidelity Advantage Class
Management fee		0.14%	0.14%
Distribution and/or Service (12b-1) fees		none	none
Other expenses		0.20%	0.06%
Total annual operating expenses	[1]	0.34%	0.20%
Fee waiver and/or expense reimbursement	[2]	0.07%	0.07%
Total annual operating expenses after fee waiver and/or expense reimbursement	[1]	0.27%	0.13%

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 Adv Inv Spartan Real Estate Index Fund (USD $)	Investor Class	Fidelity Advantage Class
1 year	28	13
3 years	101	56
5 years	183	104
10 years	423	247

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. For the period from September 8, 2011 to July 31, 2012, the fund's portfolio turnover rate was 67% of the average value of its portfolio.

Principal Investment Strategies

• Normally investing at least 80% of assets in securities included in the Dow Jones U.S. Select Real Estate Securities Index^SM (the Index).
• Lending securities to earn income for the fund.

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 can react differently to these developments.
• Real Estate Industry Concentration. Changes in real estate values or economic downturns can have a significant negative effect on issuers in the real estate industry.
• 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.
• Correlation to Index. The performance of the fund and its index may vary somewhat due to factors such as transaction costs, sample selection, and timing differences associated with additions to and deletions from its index.

In addition, the fund is considered non-diversified and can invest a greater portion of assets in securities of a smaller number of individual issuers than a diversified fund. As a result, changes in the market value of a single investment could cause greater fluctuations in share price than would occur in a more diversified fund.

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

Performance history will be available for the fund after the fund has been in operation for one calendar year.

[1] Differs from the ratios of expenses to average net assets in the Financial Highlights section of the prospectus because of acquired fund fees and expenses. For the period, acquired fund fees and expenses are less than 0.01% and are included in other expenses. As a result, the total annual operating expenses after fee waiver and/or expense reimbursement in the fee table exceed the contractual expense limitations of the fund.

[2] Fidelity Management & Research Company (FMR) has contractually agreed to reimburse Investor Class and Fidelity Advantage Class of the fund to the extent that total operating expenses (excluding interest, taxes, certain securities lending costs, brokerage commissions, extraordinary expenses, and acquired fund fees and expenses, if any), as a percentage of their respective average net assets, exceed 0.26% and 0.12%, respectively. These arrangements will remain in effect through September 30, 2013, after which date FMR, in its sole discretion, may discontinue these arrangements at any time.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

FIDELITY SALEM STREET TRUST

Prospectus Date

rr_ProspectusDate

Sep. 29, 2012

Series | Fidelity Series Commodity Strategy Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

Fund Summary

Fund/Class:
Fidelity^® Series Commodity Strategy Fund/Fidelity Series Commodity Strategy Fund

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The fund seeks to provide investment returns that correspond to the performance of the commodities market.

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)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

at least one year from the effective date of the prospectus

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when fund shares are held in a taxable account. These costs, which are not reflected in annual operating expenses or in the example, affect the fund's performance. During the most recent fiscal year, the fund's portfolio turnover rate was 148% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

148.00%

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 in commodity-linked notes, other commodity-linked derivative instruments, short-term investment-grade debt securities, cash, and cash equivalents.
• Investing up to 25% of assets in a wholly-owned subsidiary that invests in commodity-linked total return swaps based on the value of commodities or commodities indices and in other commodity-linked derivative instruments.
• Managing the fund to track an index chosen to represent the commodities market, as well as short-term investment-grade debt securities, which as of July 31, 2012 was the Dow Jones-UBS Commodity Index Total Return^SM.
• Investing in domestic and foreign issuers.
• Engaging in commodity-linked derivatives transactions that have a leveraging effect on the fund.
• Investing in Fidelity's central funds (specialized investment vehicles used by Fidelity funds to invest in particular security types or investment disciplines).

Risk [Heading]

rr_RiskHeading

Principal Investment Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

• Interest Rate Changes. Interest rate increases can cause the price of a debt security to decrease.
• Foreign Exposure. Foreign markets can be more volatile than the U.S. market due to increased risks of adverse issuer, political, regulatory, market, or economic developments and can perform differently from the U.S. market.
• Financial Services Exposure. Changes in government regulation and interest rates and economic downturns can have a significant negative effect on issuers in the financial services sector, including the price of their securities or their ability to meet their payment obligations.
• Subsidiary Risk. Investment in an unregistered subsidiary is not subject to the investor protections of the Investment Company Act of 1940 (1940 Act) and is subject to the risks associated with investing in derivatives and commodity-linked investing in general. Changes in tax and other laws could negatively affect investments in the subsidiary.
• Prepayment. The ability of an issuer of a debt security to repay principal prior to a security's maturity can cause greater price volatility if interest rates change.
• Issuer-Specific Changes. The value of an individual security or particular type of security can be more volatile than, and can perform differently from, the market as a whole. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a security to decrease.
• Leverage Risk. Leverage can increase market exposure, magnify investment risks, and cause losses to be realized more quickly.
• Commodity-Linked Investing. Commodity-linked investments may be more volatile and less liquid than the underlying commodity, instruments, or measures and their value may be affected by the performance of the overall commodities markets as well as weather, political, tax, and other regulatory and market developments.

In addition, the fund is considered non-diversified and can invest a greater portion of assets in securities of a smaller number of individual issuers than a diversified fund. As a result, changes in the market value of a single investment could cause greater fluctuations in share price than would occur in a more diversified fund.

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 Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

In addition, the fund is considered non-diversified and can invest a greater portion of assets in securities of a smaller number of individual issuers than a diversified fund. As a result, changes in the market value of a single investment could cause greater fluctuations in share price than would occur in a more diversified 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 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 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	15.54%	December 31, 2010
Lowest Quarter Return	-11.72%	September 30, 2011
Year-to-Date Return	-4.02%	June 30, 2012

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, 2011

Series | Fidelity Series Commodity Strategy Fund | Class: Fidelity Series Commodity Strategy Fund

Risk/Return:

rr_RiskReturnAbstract

Shareholder fees (fees paid directly from your investment)

rr_ShareholderFeeOther

none

Management fee

rr_ManagementFeesOverAssets

0.40%

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

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.20%

Acquired Fund Fees and Expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.04%

^[1]

Total annual operating expenses

rr_ExpensesOverAssets

0.64%

Fee waiver and/or expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

0.04%

^[1]

Total annual operating expenses after fee waiver and/or expense reimbursement

rr_NetExpensesOverAssets

0.60%

1 year

rr_ExpenseExampleYear01

61

3 years

rr_ExpenseExampleYear03

192

5 years

rr_ExpenseExampleYear05

335

10 years

rr_ExpenseExampleYear10

750

2010

rr_AnnualReturn2010

15.96%

2011

rr_AnnualReturn2011

(13.89%)

Year to Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date Return

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Jun. 30, 2012

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

(4.02%)

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter Return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Dec. 31, 2010

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

15.54%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter Return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2011

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(11.72%)

Series | Fidelity Series Commodity Strategy Fund | Return Before Taxes | Class: Fidelity Series Commodity Strategy Fund

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity Series Commodity Strategy Fund

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

Past 1 Year

rr_AverageAnnualReturnYear01

(13.89%)

Life of class

rr_AverageAnnualReturnSinceInception

4.51%

^[2]

Inception Date

rr_AverageAnnualReturnInceptionDate

Oct. 01, 2009

Series | Fidelity Series Commodity Strategy Fund | Return After Taxes on Distributions | Class: Fidelity Series Commodity Strategy Fund

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity Series Commodity Strategy Fund

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

Past 1 Year

rr_AverageAnnualReturnYear01

(18.92%)

Life of class

rr_AverageAnnualReturnSinceInception

1.52%

^[2]

Inception Date

rr_AverageAnnualReturnInceptionDate

Oct. 01, 2009

Series | Fidelity Series Commodity Strategy Fund | Return After Taxes on Distributions and Sale of Fund Shares | Class: Fidelity Series Commodity Strategy Fund

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity Series Commodity Strategy Fund

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

Past 1 Year

rr_AverageAnnualReturnYear01

(8.22%)

Life of class

rr_AverageAnnualReturnSinceInception

2.50%

^[2]

Inception Date

rr_AverageAnnualReturnInceptionDate

Oct. 01, 2009

Series | Fidelity Series Commodity Strategy Fund | Dow Jones-UBS Commodity Index Total Return (reflects no deduction for fees, expenses, or taxes)

Risk/Return:

rr_RiskReturnAbstract

Label

rr_AverageAnnualReturnLabel

Dow Jones-UBS Commodity Index Total Return^SM

Past 1 Year

rr_AverageAnnualReturnYear01

(13.32%)

Life of class

rr_AverageAnnualReturnSinceInception

5.33%

^[2]

Inception Date

rr_AverageAnnualReturnInceptionDate

Oct. 01, 2009

[1] The fund may invest in a wholly-owned subsidiary. The subsidiary has entered into a separate contract with Fidelity Management & Research Company (FMR) for the management of its portfolio pursuant to which the subsidiary pays FMR a fee at an annual rate of 0.30% of its net assets. The subsidiary also pays certain other expenses including custody fees. FMR has contractually agreed to waive the fund's management fee in an amount equal to the management fee paid to FMR by the subsidiary. The fund also may invest in Fidelity Commodity Strategy Central Fund, which in turn invests in its own wholly-owned subsidiary that invests in commodity-linked derivative instruments. FMR has contractually agreed to waive the fund's management fee in an amount equal to its proportionate share of the management fee paid to FMR by the central fund's subsidiary based on the fund's proportionate ownership of the central fund. These arrangements will remain in effect for at least one year from the effective date of the prospectus, and will remain in effect thereafter as long as FMR's contract with the applicable subsidiary is in place. If FMR's contract with a subsidiary is terminated, FMR, in its sole discretion, may discontinue the arrangement.

[2] From October 1, 2009.

XML

F | Fidelity Series Commodity Strategy Fund

Fund Summary

Fund/Class:
Fidelity^® Series Commodity Strategy Fund/F

Investment Objective

The fund seeks to provide investment returns that correspond to the performance of the commodities market.

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 Commodity Strategy 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 Commodity Strategy Fund Class F
Management fee		0.40%
Distribution and/or Service (12b-1) fees		none
Other expenses		none
Acquired fund fees and expenses	[1]	0.04%
Total annual operating expenses		0.44%
Fee waiver and/or expense reimbursement	[1]	0.04%
Total annual operating expenses after fee waiver and/or expense reimbursement		0.40%

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 Commodity Strategy Fund Class F
1 year	41
3 years	128
5 years	224
10 years	505

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 148% of the average value of its portfolio.

Principal Investment Strategies

• Normally investing in commodity-linked notes, other commodity-linked derivative instruments, short-term investment-grade debt securities, cash, and cash equivalents.
• Investing up to 25% of assets in a wholly-owned subsidiary that invests in commodity-linked total return swaps based on the value of commodities or commodities indices and in other commodity-linked derivative instruments.
• Managing the fund to track an index chosen to represent the commodities market, as well as short-term investment-grade debt securities, which as of July 31, 2012 was the Dow Jones-UBS Commodity Index Total Return^SM.
• Investing in domestic and foreign issuers.
• Engaging in commodity-linked derivatives transactions that have a leveraging effect on the fund.
• Investing in Fidelity's central funds (specialized investment vehicles used by Fidelity funds to invest in particular security types or investment disciplines).

Principal Investment Risks

• Interest Rate Changes. Interest rate increases can cause the price of a debt security to decrease.
• Foreign Exposure. Foreign markets can be more volatile than the U.S. market due to increased risks of adverse issuer, political, regulatory, market, or economic developments and can perform differently from the U.S. market.
• Financial Services Exposure. Changes in government regulation and interest rates and economic downturns can have a significant negative effect on issuers in the financial services sector, including the price of their securities or their ability to meet their payment obligations.
• Subsidiary Risk. Investment in an unregistered subsidiary is not subject to the investor protections of the Investment Company Act of 1940 (1940 Act) and is subject to the risks associated with investing in derivatives and commodity-linked investing in general. Changes in tax and other laws could negatively affect investments in the subsidiary.
• Prepayment. The ability of an issuer of a debt security to repay principal prior to a security's maturity can cause greater price volatility if interest rates change.
• Issuer-Specific Changes. The value of an individual security or particular type of security can be more volatile than, and can perform differently from, the market as a whole. A decline in the credit quality of an issuer or a provider of credit support or a maturity-shortening structure for a security can cause the price of a security to decrease.
• Leverage Risk. Leverage can increase market exposure, magnify investment risks, and cause losses to be realized more quickly.
• Commodity-Linked Investing. Commodity-linked investments may be more volatile and less liquid than the underlying commodity, instruments, or measures and their value may be affected by the performance of the overall commodities markets as well as weather, political, tax, and other regulatory and market developments.

In addition, the fund is considered non-diversified and can invest a greater portion of assets in securities of a smaller number of individual issuers than a diversified fund. As a result, changes in the market value of a single investment could cause greater fluctuations in share price than would occur in a more diversified fund.

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 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 Years

During the periods shown in the chart:	Returns	Quarter ended
Highest Quarter Return	15.62%	December 31, 2010
Lowest Quarter Return	-11.67%	September 30, 2011
Year-to-Date Return	-3.90%	June 30, 2012

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, 2011

Average Annual Total Returns F Fidelity Series Commodity Strategy Fund	Past 1 Year	Life of class		Inception Date
Class F Return Before Taxes	(13.77%)	4.69%	[1]	Oct. 01, 2009
Class F Return After Taxes on Distributions	(18.85%)	1.66%	[1]	Oct. 01, 2009
Class F Return After Taxes on Distributions and Sale of Fund Shares	(8.13%)	2.62%	[1]	Oct. 01, 2009
Dow Jones-UBS Commodity Index Total Return (reflects no deduction for fees, expenses, or taxes)	(13.32%)	5.33%	[1]	Oct. 01, 2009

[1] The fund may invest in a wholly-owned subsidiary. The subsidiary has entered into a separate contract with Fidelity Management & Research Company (FMR) for the management of its portfolio pursuant to which the subsidiary pays FMR a fee at an annual rate of 0.30% of its net assets. The subsidiary also pays certain other expenses including custody fees. FMR has contractually agreed to waive the fund's management fee in an amount equal to the management fee paid to FMR by the subsidiary. The fund also may invest in Fidelity Commodity Strategy Central Fund, which in turn invests in its own wholly-owned subsidiary that invests in commodity-linked derivative instruments. FMR has contractually agreed to waive the fund's management fee in an amount equal to its proportionate share of the management fee paid to FMR by the central fund's subsidiary based on the fund's proportionate ownership of the central fund. These arrangements will remain in effect for at least one year from the effective date of the prospectus, and will remain in effect thereafter as long as FMR's contract with the applicable subsidiary is in place. If FMR's contract with a subsidiary is terminated, FMR, in its sole discretion, may discontinue the arrangement.

[1] From October 1, 2009.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	FIDELITY SALEM STREET TRUST
Prospectus Date	rr_ProspectusDate	Sep. 29, 2012
Adv Inv | Spartan Real Estate Index Fund
Risk/Return:	rr_RiskReturnAbstract
Risk/Return [Heading]	rr_RiskReturnHeading	Fund Summary Fund/Class: Spartan® Real Estate Index Fund/Investor, Fidelity Advantage®
Objective [Heading]	rr_ObjectiveHeading	Investment Objective
Objective, Primary [Text Block]	rr_ObjectivePrimaryTextBlock	The fund seeks to provide investment results that correspond to the total return of equity REITs and other real estate-related investments.
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)
Fee Waiver or Reimbursement over Assets, Date of Termination	rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination	September 30, 2013
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. For the period from September 8, 2011 to July 31, 2012, the fund's portfolio turnover rate was 67% of the average value of its portfolio.
Portfolio Turnover, Rate	rr_PortfolioTurnoverRate	67.00%
Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]	rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees	Differs from the ratios of expenses to average net assets in the Financial Highlights section of the prospectus because of acquired fund fees and expenses.
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 at least 80% of assets in securities included in the Dow Jones U.S. Select Real Estate Securities IndexSM (the Index). Lending securities to earn income for the fund.
Strategy Portfolio Concentration [Text]	rr_StrategyPortfolioConcentration	Normally investing at least 80% of assets in securities included in the Dow Jones U.S. Select Real Estate Securities IndexSM (the Index).
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 can react differently to these developments. Real Estate Industry Concentration. Changes in real estate values or economic downturns can have a significant negative effect on issuers in the real estate industry. 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. Correlation to Index. The performance of the fund and its index may vary somewhat due to factors such as transaction costs, sample selection, and timing differences associated with additions to and deletions from its index. In addition, the fund is considered non-diversified and can invest a greater portion of assets in securities of a smaller number of individual issuers than a diversified fund. As a result, changes in the market value of a single investment could cause greater fluctuations in share price than would occur in a more diversified fund. 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 Nondiversified Status [Text]	rr_RiskNondiversifiedStatus	In addition, the fund is considered non-diversified and can invest a greater portion of assets in securities of a smaller number of individual issuers than a diversified fund. As a result, changes in the market value of a single investment could cause greater fluctuations in share price than would occur in a more diversified 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 One Year or Less [Text]	rr_PerformanceOneYearOrLess	Performance history will be available for the fund after the fund has been in operation for one calendar year.
Adv Inv | Spartan Real Estate Index Fund | Investor Class
Risk/Return:	rr_RiskReturnAbstract
Redemption fee on shares held less than 90 days (as a % of amount redeemed)	rr_RedemptionFeeOverRedemption	0.75%
Annual index fund fee (for fund balances under $10,000)	rr_MaximumAccountFee	10.00
Management fee	rr_ManagementFeesOverAssets	0.14%
Distribution and/or Service (12b-1) fees	rr_DistributionAndService12b1FeesOverAssets	none
Other expenses	rr_OtherExpensesOverAssets	0.20%
Total annual operating expenses	rr_ExpensesOverAssets	0.34%	[1]
Fee waiver and/or expense reimbursement	rr_FeeWaiverOrReimbursementOverAssets	0.07%	[2]
Total annual operating expenses after fee waiver and/or expense reimbursement	rr_NetExpensesOverAssets	0.27%	[1]
1 year	rr_ExpenseExampleYear01	28
3 years	rr_ExpenseExampleYear03	101
5 years	rr_ExpenseExampleYear05	183
10 years	rr_ExpenseExampleYear10	423
Adv Inv | Spartan Real Estate Index Fund | Fidelity Advantage Class
Risk/Return:	rr_RiskReturnAbstract
Redemption fee on shares held less than 90 days (as a % of amount redeemed)	rr_RedemptionFeeOverRedemption	0.75%
Annual index fund fee (for fund balances under $10,000)	rr_MaximumAccountFee	10.00
Management fee	rr_ManagementFeesOverAssets	0.14%
Distribution and/or Service (12b-1) fees	rr_DistributionAndService12b1FeesOverAssets	none
Other expenses	rr_OtherExpensesOverAssets	0.06%
Total annual operating expenses	rr_ExpensesOverAssets	0.20%	[1]
Fee waiver and/or expense reimbursement	rr_FeeWaiverOrReimbursementOverAssets	0.07%	[2]
Total annual operating expenses after fee waiver and/or expense reimbursement	rr_NetExpensesOverAssets	0.13%	[1]
1 year	rr_ExpenseExampleYear01	13
3 years	rr_ExpenseExampleYear03	56
5 years	rr_ExpenseExampleYear05	104
10 years	rr_ExpenseExampleYear10	247

[1] Differs from the ratios of expenses to average net assets in the Financial Highlights section of the prospectus because of acquired fund fees and expenses. For the period, acquired fund fees and expenses are less than 0.01% and are included in other expenses. As a result, the total annual operating expenses after fee waiver and/or expense reimbursement in the fee table exceed the contractual expense limitations of the fund.

[2] Fidelity Management & Research Company (FMR) has contractually agreed to reimburse Investor Class and Fidelity Advantage Class of the fund to the extent that total operating expenses (excluding interest, taxes, certain securities lending costs, brokerage commissions, extraordinary expenses, and acquired fund fees and expenses, if any), as a percentage of their respective average net assets, exceed 0.26% and 0.12%, respectively. These arrangements will remain in effect through September 30, 2013, after which date FMR, in its sole discretion, may discontinue these arrangements at any time.