Risk/Return Detail Data - FidelitySeriesInvestmentGradeBondFund-PRO - USD ($)			12 Months Ended											60 Months Ended	72 Months Ended		84 Months Ended		96 Months Ended		108 Months Ended		120 Months Ended
		Oct. 30, 2025	Oct. 30, 2025	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Oct. 30, 2025	Oct. 30, 2025		Oct. 30, 2025	[4]	Oct. 30, 2025		Oct. 30, 2025	[9]	Oct. 30, 2025
FidelityCorporateBondFund-AMCIZPRO | Fidelity Corporate Bond Fund | Fidelity Advisor Corporate Bond Fund - Class A
Prospectus Line Items
Maximum Cumulative Sales Charge (as a percentage of Offering Price)		4.00%
Maximum Deferred Sales Charge (as a percentage)	[1]	0.00%
Management Fees (as a percentage of Assets)		0.35%
Distribution and Service (12b-1) Fees		0.25%
Other Expenses (as a percentage of Assets):		0.17%
Expenses (as a percentage of Assets)		0.77%
Fee Waiver or Reimbursement		(0.00%)
Net Expenses (as a percentage of Assets)		0.77%
Expense Example, with Redemption, 1 Year		$ 475
Expense Example, with Redemption, 3 Years		636
Expense Example, with Redemption, 5 Years		811
Expense Example, with Redemption, 10 Years		1,316
Expense Example, No Redemption, 1 Year		475
Expense Example, No Redemption, 3 Years		636
Expense Example, No Redemption, 5 Years		811
Expense Example, No Redemption, 10 Years		$ 1,316
Average Annual Return, Label [Optional Text]			Return Before Taxes
Average Annual Return, Percent			(1.61%)											(0.68%)									1.74%
Annual Return [Percent]				2.49%	8.44%	(16.71%)	(1.53%)	10.45%	14.09%	(2.91%)	6.46%	6.13%	(1.76%)
FidelityCorporateBondFund-AMCIZPRO | Fidelity Corporate Bond Fund | Fidelity Advisor Corporate Bond Fund - Class M
Prospectus Line Items
Maximum Cumulative Sales Charge (as a percentage of Offering Price)		4.00%
Maximum Deferred Sales Charge (as a percentage)	[1]	0.00%
Management Fees (as a percentage of Assets)		0.35%
Distribution and Service (12b-1) Fees		0.25%
Other Expenses (as a percentage of Assets):		0.20%
Expenses (as a percentage of Assets)		0.80%
Fee Waiver or Reimbursement		(0.00%)
Net Expenses (as a percentage of Assets)		0.80%
Expense Example, with Redemption, 1 Year		$ 478
Expense Example, with Redemption, 3 Years		645
Expense Example, with Redemption, 5 Years		826
Expense Example, with Redemption, 10 Years		1,350
Expense Example, No Redemption, 1 Year		478
Expense Example, No Redemption, 3 Years		645
Expense Example, No Redemption, 5 Years		826
Expense Example, No Redemption, 10 Years		$ 1,350
Average Annual Return, Label [Optional Text]			Return Before Taxes
Average Annual Return, Percent			(1.65%)											(0.72%)									1.68%
FidelityCorporateBondFund-AMCIZPRO | Fidelity Corporate Bond Fund | Fidelity Advisor Corporate Bond Fund - Class C
Prospectus Line Items
Maximum Cumulative Sales Charge (as a percentage of Offering Price)		0.00%
Maximum Deferred Sales Charge (as a percentage)	[2]	1.00%
Management Fees (as a percentage of Assets)		0.35%
Distribution and Service (12b-1) Fees		1.00%
Other Expenses (as a percentage of Assets):		0.17%
Expenses (as a percentage of Assets)		1.52%
Fee Waiver or Reimbursement		(0.00%)
Net Expenses (as a percentage of Assets)		1.52%
Expenses Deferred Charges [Text Block]		On Class C shares redeemed less than one year after purchase.
Expense Example, with Redemption, 1 Year		$ 255
Expense Example, with Redemption, 3 Years		480
Expense Example, with Redemption, 5 Years		829
Expense Example, with Redemption, 10 Years		1,610
Expense Example, No Redemption, 1 Year		155
Expense Example, No Redemption, 3 Years		480
Expense Example, No Redemption, 5 Years		829
Expense Example, No Redemption, 10 Years		$ 1,610
Average Annual Return, Label [Optional Text]			Return Before Taxes
Average Annual Return, Percent			0.73%											(0.63%)									1.54%
FidelityCorporateBondFund-AMCIZPRO | Fidelity Corporate Bond Fund | Fidelity Advisor Corporate Bond Fund - Class I
Prospectus Line Items
Maximum Cumulative Sales Charge (as a percentage of Offering Price)		0.00%
Maximum Deferred Sales Charge (as a percentage)		0.00%
Management Fees (as a percentage of Assets)		0.35%
Distribution and Service (12b-1) Fees		0.00%
Other Expenses (as a percentage of Assets):		0.15%
Expenses (as a percentage of Assets)		0.50%
Fee Waiver or Reimbursement		(0.00%)
Net Expenses (as a percentage of Assets)		0.50%
Expense Example, with Redemption, 1 Year		$ 51
Expense Example, with Redemption, 3 Years		160
Expense Example, with Redemption, 5 Years		280
Expense Example, with Redemption, 10 Years		628
Expense Example, No Redemption, 1 Year		51
Expense Example, No Redemption, 3 Years		160
Expense Example, No Redemption, 5 Years		280
Expense Example, No Redemption, 10 Years		$ 628
Average Annual Return, Label [Optional Text]			Return Before Taxes
Average Annual Return, Percent			2.77%											0.41%									2.44%
FidelityCorporateBondFund-AMCIZPRO | Fidelity Corporate Bond Fund | Fidelity Advisor Corporate Bond Fund - Class Z
Prospectus Line Items
Maximum Cumulative Sales Charge (as a percentage of Offering Price)		0.00%
Maximum Deferred Sales Charge (as a percentage)		0.00%
Management Fees (as a percentage of Assets)		0.35%
Distribution and Service (12b-1) Fees		0.00%
Other Expenses (as a percentage of Assets):		0.05%
Expenses (as a percentage of Assets)		0.40%
Fee Waiver or Reimbursement	[3]	(0.04%)
Net Expenses (as a percentage of Assets)		0.36%
Expense Example, with Redemption, 1 Year		$ 37
Expense Example, with Redemption, 3 Years		123
Expense Example, with Redemption, 5 Years		219
Expense Example, with Redemption, 10 Years		500
Expense Example, No Redemption, 1 Year		37
Expense Example, No Redemption, 3 Years		123
Expense Example, No Redemption, 5 Years		219
Expense Example, No Redemption, 10 Years		$ 500
Annual Return, Inception Date		Oct. 02, 2018
Average Annual Return, Label [Optional Text]			Return Before Taxes
Average Annual Return, Percent			2.81%											0.53%			2.51%
FidelityCorporateBondFund-AMCIZPRO | Fidelity Corporate Bond Fund
Prospectus Line Items
Risk/Return [Heading]		Fund Summary Fund /Class: Fidelity® Corporate Bond Fund /Fidelity Advisor® Corporate Bond Fund A, M, C, I, Z
Objective [Heading]		Investment Objective
Objective, Primary [Text Block]		Fidelity® Corporate Bond Fund seeks a high level of current income.
Expense Heading [Optional Text]		Fee Table
Expense Narrative [Text Block]		The following table describes the fees and expenses that may be incurred when you buy, hold, and sell shares of the fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $ 50,000 in the fund or certain other Fidelity ® funds. More information about these and other discounts is available from your investment professional and in the "Fund Distribution" section beginning on page 33 of the prospectus and in the sales charge waiver appendix to the prospectus.
Shareholder Fees Caption [Optional Text]		Shareholder fees
Operating Expenses Caption [Optional Text]		Annual Operating Expenses
Fee Waiver or Reimbursement over Assets, Date of Termination		Dec. 31, 2026
Portfolio Turnover [Heading]		Portfolio Turnover
Portfolio Turnover [Text Block]		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 43 % of the average value of its portfolio.
Portfolio Turnover, Rate		43.00%
Expenses Deferred Charges [Text Block]		Class A and Class M purchases of $1 million or more will not be subject to a front-end sales charge. Such Class A and Class M purchases may be subject, upon redemption, to a contingent deferred sales charge (CDSC) of 0.75% and 0.25%, respectively.
Expense Breakpoint Discounts [Text]		You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $ 50,000 in the fund or certain other Fidelity ® funds. More information about these and other discounts is available from your investment professional and in the "Fund Distribution" section beginning on page 33 of the prospectus
Expense Breakpoint, Minimum Investment Required [Amount]		$ 50,000
Expense Example Narrative [Text Block]		This example helps compare the cost of investing in the fund with the cost of investing in other funds. Let's say, hypothetically, that the annual return for shares of the fund is 5% and that the fees and the annual operating expenses for shares of the fund are exactly as described in the fee table. This example illustrates the effect of fees and expenses, but is not meant to suggest actual or expected fees and expenses or returns, all of which may vary. For every $10,000 you invested, here's how much you would pay in total expenses if you sell all of your shares at the end of each time period indicated and if you hold your shares:
Strategy [Heading]		Principal Investment Strategies
Strategy Narrative [Text Block]		Normally investing at least 80% of assets in corporate bonds and other corporate debt securities and repurchase agreements for those securities. Corporate debt securities are bonds and other debt securities issued by corporations and other business structures to borrow money. The issuer usually pays a fixed, variable, or floating rate of interest, and must repay the amount borrowed, usually at the maturity of the security. Corporate debt securities include repurchase agreements with corporate counterparties and other securities, such as hybrids and synthetic securities, believed to have corporate debt-like characteristics, (e.g., securities classified as Tier 2 Regulatory capital, securities that rank above share capital in an insolvency waterfall, securities with maturity dates and non-cancellable interest payment structures). A repurchase agreement is an agreement to buy a security at one price and a simultaneous agreement to sell it back at an agreed-upon price. Effective December 11, 2025, derivative instruments that provide investment exposure to the investments above or exposure to one or more market risk factors associated with such investments are included in the fund's 80% policy, consistent with the fund's investment policies and limitations with respect to investments in derivatives.   Normally investing primarily in investment-grade corporate debt securities and repurchase agreements for those securities. Managing the fund to have similar overall interest rate risk to the Bloomberg U.S. Credit Bond Index. Investing in domestic and foreign issuers. Analyzing the credit quality of the issuer, security-specific features, current and potential future valuation, and trading opportunities to select investments. Investing in lower-quality debt securities (those of less than investment-grade quality, also referred to as high yield debt securities or junk bonds). Engaging in transactions that have a leveraging effect on the fund, including investments in derivatives - such as swaps (interest rate, total return, and credit default), options, and futures contracts - and forward-settling securities, to adjust the fund's risk exposure. Investing in Fidelity's Central funds (specialized investment vehicles used by Fidelity® funds to invest in particular security types or investment disciplines) consistent with the asset classes discussed above.
Bar Chart and Performance Table [Heading]		Performance
Performance Narrative [Text Block]		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 and an additional index over various periods of time. The additional index has characteristics relevant to the fund's investment strategies. Index descriptions appear in the "Additional Index Information" section of the prospectus. Past performance (before and after taxes) is not an indication of future performance. Visit institutional.fidelity.com for more recent performance information.
Performance Information Illustrates Variability of Returns [Text]		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 and an additional index over various periods of time.
Performance Availability Website Address [Text]		institutional.fidelity.com
Performance Past Does Not Indicate Future [Text]		Past performance (before and after taxes) is not an indication of future performance.
Bar Chart [Heading]		Year-by-Year Returns
Bar Chart Narrative [Text Block]		The returns in the bar chart do not reflect any applicable sales charges; if sales charges were reflected, returns would be lower than those shown.
Bar Chart Does Not Reflect Sales Loads [Text]		The returns in the bar chart do not reflect any applicable sales charges; if sales charges were reflected, returns would be lower than those shown.
Year to Date Return, Label [Optional Text]		Year-to-Date Return
Bar Chart, Year to Date Return, Date		Sep. 30, 2025
Bar Chart, Year to Date Return		6.74%
Highest Quarterly Return, Label [Optional Text]		Highest Quarter Return
Highest Quarterly Return, Date		Jun. 30, 2020
Highest Quarterly Return		10.15%
Lowest Quarterly Return, Label [Optional Text]		Lowest Quarter Return
Lowest Quarterly Return, Date		Jun. 30, 2022
Lowest Quarterly Return		(7.80%)
Performance Table Heading		Average Annual Returns
Performance Table Does Reflect Sales Loads		Unlike the returns in the bar chart, the returns in the table reflect the maximum applicable sales charges.
Performance Table Uses Highest Federal Rate		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		The after-tax returns shown are not relevant if you hold your shares in a retirement account or in another tax-deferred arrangement, such as an employee benefit plan (profit sharing, 401(k), or 403(b) plan).
Performance Table One Class of after Tax Shown [Text]		After-tax returns for Class A are shown in the table below and after-tax returns for other classes will vary.
Performance Table Explanation after Tax Higher		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		Unlike the returns in the bar chart, the returns in the table reflect the maximum applicable sales charges. After-tax returns are calculated using the historical highest individual federal marginal income tax rates, but do not reflect the impact of state or local taxes. After-tax returns for Class A are shown in the table below and after-tax returns for other classes will vary. Actual after-tax returns may differ depending on your individual circumstances. The after-tax returns shown are not relevant if you hold your shares in a retirement account or in another tax-deferred arrangement, such as an employee benefit plan (profit sharing, 401(k), or 403(b) plan). 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.
FidelityCorporateBondFund-AMCIZPRO | Fidelity Corporate Bond Fund | After Taxes on Distributions | Fidelity Advisor Corporate Bond Fund - Class A
Prospectus Line Items
Average Annual Return, Label [Optional Text]			Return After Taxes on Distributions
Average Annual Return, Percent			(2.97%)											(1.92%)									0.47%
FidelityCorporateBondFund-AMCIZPRO | Fidelity Corporate Bond Fund | After Taxes on Distributions and Sales | Fidelity Advisor Corporate Bond Fund - Class A
Prospectus Line Items
Average Annual Return, Label [Optional Text]			Return After Taxes on Distributions and Sale of Fund Shares
Average Annual Return, Percent			(0.89%)											(1.00%)									0.79%
FidelityCorporateBondFund-AMCIZPRO | Fidelity Corporate Bond Fund | LB004
Prospectus Line Items
Average Annual Return, Label [Optional Text]			Bloomberg U.S. Credit Bond Index
Average Annual Return, Percent			2.03%											0.23%									2.29%
FidelityCorporateBondFund-AMCIZPRO | Fidelity Corporate Bond Fund | LB001
Prospectus Line Items
Average Annual Return, Label [Optional Text]			Bloomberg U.S. Aggregate Bond Index
Average Annual Return, Percent			1.25%											(0.33%)									1.35%
FidelitySeriesBondIndexFund-PRO | Fidelity Series Bond Index Fund | Fidelity Series Bond Index Fund
Prospectus Line Items
Management Fees (as a percentage of Assets)		0.00%
Distribution and Service (12b-1) Fees		0.00%
Other Expenses (as a percentage of Assets):		0.00%
Expenses (as a percentage of Assets)		0.00%
Expense Example, with Redemption, 1 Year		$ 0
Expense Example, with Redemption, 3 Years		0
Expense Example, with Redemption, 5 Years		0
Expense Example, with Redemption, 10 Years		$ 0
Annual Return, Inception Date		Apr. 26, 2019
Average Annual Return, Label [Optional Text]			Return Before Taxes
Average Annual Return, Percent			1.40%											(0.32%)	0.65%	[5]
Annual Return [Percent]				1.40%	5.52%	(12.98%)	(1.80%)	7.65%
FidelitySeriesBondIndexFund-PRO | Fidelity Series Bond Index Fund
Prospectus Line Items
Risk/Return [Heading]		Fund Summary Fund: Fidelity® Series Bond Index Fund
Objective [Heading]		Investment Objective
Objective, Primary [Text Block]		Fidelity® Series Bond Index Fund seeks to provide investment results that correspond to the aggregate price and interest performance of the debt securities in the Bloomberg U.S. Aggregate Bond Index.
Expense Heading [Optional Text]		Fee Table
Expense Narrative [Text Block]		The following table describes the fees and expenses that may be incurred when you buy, hold, and sell shares of the fund.
Shareholder Fees Caption [Optional Text]		Shareholder fees
Shareholder Fee, Other		$ 0
Operating Expenses Caption [Optional Text]		Annual Operating Expenses
Portfolio Turnover [Heading]		Portfolio Turnover
Portfolio Turnover [Text Block]		The fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when fund shares are held in a taxable account. These costs, which are not reflected in annual operating expenses or in the example, affect the fund's performance. During the most recent fiscal year, the fund's portfolio turnover rate was 55 % of the average value of its portfolio.
Portfolio Turnover, Rate		55.00%
Expense Example Narrative [Text Block]		This example helps compare the cost of investing in the fund with the cost of investing in other funds. Let's say, hypothetically, that the annual return for shares of the fund is 5% and that the 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]		Principal Investment Strategies
Strategy Narrative [Text Block]		Normally investing at least 80% of assets in bonds included in the Bloomberg U.S. Aggregate Bond Index. The Bloomberg U.S. Aggregate Bond Index is a broad based, flagship benchmark that measures the investment grade, US dollar-denominated, fixed-rate taxable bond market. The index includes Treasuries, government-related and corporate securities, mortgage-backed securities (agency fixed-rate pass-throughs), asset-backed securities and collateralized mortgage-backed securities (agency and non-agency). Effective December 11, 2025, derivative instruments that provide investment exposure to the investments above or exposure to one or more market risk factors associated with such investments are included in the fund's 80% policy, consistent with the fund's investment policies and limitations with respect to investments in derivatives.   Using statistical sampling techniques based on duration, maturity, interest rate sensitivity, security structure, and credit quality to attempt to replicate the returns of the Bloomberg U.S. Aggregate Bond Index using a smaller number of securities. Engaging in transactions that have a leveraging effect on the fund, including investments in derivatives - such as swaps (interest rate, total return, and credit default), options, and futures contracts - and forward-settling securities, to adjust the fund's risk exposure.
Bar Chart and Performance Table [Heading]		Performance
Performance Narrative [Text Block]		The following information is intended to help you understand the risks of investing in the fund. The information illustrates the changes in the performance of the fund's shares from year to year and compares the performance of the fund's shares to the performance of a securities market index over various periods of time. The index description appears in the "Additional Index Information" section of the prospectus. Past performance (before and after taxes) is not an indication of future performance. The performance shown does not reflect the impact of any fees paid at the fee-based account or plan level, if applicable. Visit www.fidelity.com for more recent performance information.
Performance Information Illustrates Variability of Returns [Text]		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]		www.fidelity.com
Performance Past Does Not Indicate Future [Text]		Past performance (before and after taxes) is not an indication of future performance.
Bar Chart [Heading]		Year-by-Year Returns
Year to Date Return, Label [Optional Text]		Year-to-Date Return
Bar Chart, Year to Date Return, Date		Sep. 30, 2025
Bar Chart, Year to Date Return		6.08%
Highest Quarterly Return, Label [Optional Text]		Highest Quarter Return
Highest Quarterly Return, Date		Dec. 31, 2023
Highest Quarterly Return		6.63%
Lowest Quarterly Return, Label [Optional Text]		Lowest Quarter Return
Lowest Quarterly Return, Date		Mar. 31, 2022
Lowest Quarterly Return		(5.81%)
Performance Table Heading		Average Annual Returns
Performance Table Uses Highest Federal Rate		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		The after-tax returns shown are not relevant if you hold your shares in a retirement account or in another tax-deferred arrangement, such as an employee benefit plan (profit sharing, 401(k), or 403(b) plan).
Performance Table Explanation after Tax Higher		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		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, such as an employee benefit plan (profit sharing, 401(k), or 403(b) plan). 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.
FidelitySeriesBondIndexFund-PRO | Fidelity Series Bond Index Fund | After Taxes on Distributions | Fidelity Series Bond Index Fund
Prospectus Line Items
Average Annual Return, Label [Optional Text]			Return After Taxes on Distributions
Average Annual Return, Percent			(0.08%)											(1.42%)	(0.46%)	[5]
FidelitySeriesBondIndexFund-PRO | Fidelity Series Bond Index Fund | After Taxes on Distributions and Sales | Fidelity Series Bond Index Fund
Prospectus Line Items
Average Annual Return, Label [Optional Text]			Return After Taxes on Distributions and Sale of Fund Shares
Average Annual Return, Percent			0.82%											(0.68%)	0.05%	[5]
FidelitySeriesBondIndexFund-PRO | Fidelity Series Bond Index Fund | LB001
Prospectus Line Items
Average Annual Return, Label [Optional Text]			Bloomberg U.S. Aggregate Bond Index
Average Annual Return, Percent			1.25%											(0.33%)	0.67%
FidelitySeriesInvestmentGradeBondFund-PRO | Fidelity Series Investment Grade Bond Fund | Fidelity Series Investment Grade Bond Fund
Prospectus Line Items
Management Fees (as a percentage of Assets)		0.00%
Distribution and Service (12b-1) Fees		0.00%
Other Expenses (as a percentage of Assets):		0.00%
Expenses (as a percentage of Assets)		0.00%
Expense Example, with Redemption, 1 Year		$ 0
Expense Example, with Redemption, 3 Years		0
Expense Example, with Redemption, 5 Years		0
Expense Example, with Redemption, 10 Years		$ 0
Average Annual Return, Label [Optional Text]			Return Before Taxes
Average Annual Return, Percent			2.15%											0.86%									2.20%
Annual Return [Percent]				2.15%	6.79%	(12.65%)	(0.33%)	9.91%	9.73%	(0.17%)	4.38%	4.35%	(0.24%)
FidelitySeriesInvestmentGradeBondFund-PRO | Fidelity Series Investment Grade Bond Fund
Prospectus Line Items
Risk/Return [Heading]		Fund Summary Fund: Fidelity® Series Investment Grade Bond Fund
Objective [Heading]		Investment Objective
Objective, Primary [Text Block]		Fidelity® Series Investment Grade Bond Fund seeks a high level of current income.
Expense Heading [Optional Text]		Fee Table
Expense Narrative [Text Block]		The following table describes the fees and expenses that may be incurred when you buy, hold, and sell shares of the fund.
Shareholder Fees Caption [Optional Text]		Shareholder fees
Shareholder Fee, Other		$ 0
Operating Expenses Caption [Optional Text]		Annual Operating Expenses
Portfolio Turnover [Heading]		Portfolio Turnover
Portfolio Turnover [Text Block]		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 203 % of the average value of its portfolio.
Portfolio Turnover, Rate		203.00%
Expense Example Narrative [Text Block]		This example helps compare the cost of investing in the fund with the cost of investing in other funds. Let's say, hypothetically, that the annual return for shares of the fund is 5% and that the 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]		Principal Investment Strategies
Strategy Narrative [Text Block]		Normally investing at least 80% of assets in investment-grade debt securities (those of medium and high quality) of all types and repurchase agreements for those securities. Debt securities are used by issuers to borrow money. The issuer usually pays a fixed, variable, or floating rate of interest, and must repay the amount borrowed, usually at the maturity of the security. Debt securities include corporate bonds, government securities (including Treasury securities), repurchase agreements, money market securities, mortgage and other asset-backed securities, loans and loan participations, and other securities, such as hybrids and synthetic securities, believed to have debt-like characteristics (e.g., securities classified as Tier 2 Regulatory capital, securities that rank above share capital in an insolvency waterfall, securities with maturity dates and non-cancellable interest payment structures).  Investment grade securities in which the fund invests include securities or issuers rated at least BBB- or its equivalent by at least one nationally recognized statistical ratings organization (NRSRO), or, if unrated, determined by the Adviser to be of comparable quality. A repurchase agreement is an agreement to buy a security at one price and a simultaneous agreement to sell it back at an agreed-upon price. Effective December 11, 2025, derivative instruments that provide investment exposure to the investments above or exposure to one or more market risk factors associated with such investments are included in the fund's 80% policy, consistent with the fund's investment policies and limitations with respect to investments in derivatives.   Managing the fund to have similar overall interest rate risk to the Bloomberg U.S. Aggregate Bond Index. Allocating assets across different market sectors and maturities. Investing in domestic and foreign issuers. Analyzing the credit quality of the issuer, security-specific features, current and potential future valuation, and trading opportunities to select investments. Potentially investing in lower-quality debt securities (those of less than investment-grade quality, also referred to as high yield debt securities or junk bonds). Engaging in transactions that have a leveraging effect on the fund, including investments in derivatives - such as swaps (interest rate, total return, and credit default), options, and futures contracts - and forward-settling securities, to adjust the fund's risk exposure. Investing in Fidelity's Central funds (specialized investment vehicles used by Fidelity® funds to invest in particular security types or investment disciplines) consistent with the asset classes discussed above.
Bar Chart and Performance Table [Heading]		Performance
Performance Narrative [Text Block]		The following information is intended to help you understand the risks of investing in the fund. The information illustrates the changes in the performance of the fund's shares from year to year and compares the performance of the fund's shares to the performance of a securities market index over various periods of time. The index description appears in the "Additional Index Information" section of the prospectus. Past performance (before and after taxes) is not an indication of future performance. The performance shown does not reflect the impact of any fees paid at the fee-based account or plan level, if applicable. Visit www.fidelity.com for more recent performance information.
Performance Information Illustrates Variability of Returns [Text]		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]		www.fidelity.com
Performance Past Does Not Indicate Future [Text]		Past performance (before and after taxes) is not an indication of future performance.
Bar Chart [Heading]		Year-by-Year Returns
Year to Date Return, Label [Optional Text]		Year-to-Date Return
Bar Chart, Year to Date Return, Date		Sep. 30, 2025
Bar Chart, Year to Date Return		6.60%
Highest Quarterly Return, Label [Optional Text]		Highest Quarter Return
Highest Quarterly Return, Date		Dec. 31, 2023
Highest Quarterly Return		6.92%
Lowest Quarterly Return, Label [Optional Text]		Lowest Quarter Return
Lowest Quarterly Return, Date		Mar. 31, 2022
Lowest Quarterly Return		(5.57%)
Performance Table Heading		Average Annual Returns
Performance Table Uses Highest Federal Rate		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		The after-tax returns shown are not relevant if you hold your shares in a retirement account or in another tax-deferred arrangement, such as an employee benefit plan (profit sharing, 401(k), or 403(b) plan).
Performance Table Explanation after Tax Higher		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		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, such as an employee benefit plan (profit sharing, 401(k), or 403(b) plan). 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.
FidelitySeriesInvestmentGradeBondFund-PRO | Fidelity Series Investment Grade Bond Fund | After Taxes on Distributions | Fidelity Series Investment Grade Bond Fund
Prospectus Line Items
Average Annual Return, Label [Optional Text]			Return After Taxes on Distributions
Average Annual Return, Percent			0.41%											(0.69%)									0.73%
FidelitySeriesInvestmentGradeBondFund-PRO | Fidelity Series Investment Grade Bond Fund | After Taxes on Distributions and Sales | Fidelity Series Investment Grade Bond Fund
Prospectus Line Items
Average Annual Return, Label [Optional Text]			Return After Taxes on Distributions and Sale of Fund Shares
Average Annual Return, Percent			1.31%											0.06%									1.08%
FidelitySeriesInvestmentGradeBondFund-PRO | Fidelity Series Investment Grade Bond Fund | LB001
Prospectus Line Items
Average Annual Return, Label [Optional Text]			Bloomberg U.S. Aggregate Bond Index
Average Annual Return, Percent			1.25%											(0.33%)									1.35%
FidelityFlexUSBondIndexFund-PRO | Fidelity Flex U.S. Bond Index Fund | Fidelity Flex U.S. Bond Index Fund
Prospectus Line Items
Management Fees (as a percentage of Assets)		0.00%
Distribution and Service (12b-1) Fees		0.00%
Other Expenses (as a percentage of Assets):		0.00%
Expenses (as a percentage of Assets)	[6]	0.00%
Expense Example, with Redemption, 1 Year		$ 0
Expense Example, with Redemption, 3 Years		0
Expense Example, with Redemption, 5 Years		0
Expense Example, with Redemption, 10 Years		$ 0
Annual Return, Inception Date		Mar. 09, 2017
Average Annual Return, Label [Optional Text]			Return Before Taxes
Average Annual Return, Percent			1.30%											(0.35%)					1.33%	[7]
Annual Return [Percent]				1.30%	5.45%	(12.96%)	(1.89%)	7.72%	8.56%	0.11%
FidelityFlexUSBondIndexFund-PRO | Fidelity Flex U.S. Bond Index Fund
Prospectus Line Items
Risk/Return [Heading]		Fund Summary Fund: Fidelity Flex® U.S. Bond Index Fund
Objective [Heading]		Investment Objective
Objective, Primary [Text Block]		Fidelity Flex® U.S. Bond Index Fund seeks to provide investment results that correspond to the aggregate price and interest performance of the debt securities in the Bloomberg U.S. Aggregate Bond Index.
Expense Heading [Optional Text]		Fee Table
Expense Narrative [Text Block]		The following table describes the fees and expenses that may be incurred when you buy, hold, and sell shares of the fund. You may pay other fees, such as brokerage commissions, which are not reflected in the tables and examples below.
Shareholder Fees Caption [Optional Text]		Shareholder fees
Shareholder Fee, Other		$ 0
Operating Expenses Caption [Optional Text]		Annual Operating Expenses
Portfolio Turnover [Heading]		Portfolio Turnover
Portfolio Turnover [Text Block]		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 68 % of the average value of its portfolio.
Portfolio Turnover, Rate		68.00%
Expense Example Narrative [Text Block]		This example helps compare the cost of investing in the fund with the cost of investing in other funds. Let's say, hypothetically, that the annual return for shares of the fund is 5% and that the 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. This example does not include any fees paid at the fee-based account or plan level. 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]		Principal Investment Strategies
Strategy Narrative [Text Block]		Normally investing at least 80% of assets in bonds included in the Bloomberg U.S. Aggregate Bond Index. The Bloomberg U.S. Aggregate Bond Index is a broad based, flagship benchmark that measures the investment grade, US dollar-denominated, fixed-rate taxable bond market. The index includes Treasuries, government-related and corporate securities, mortgage-backed securities (agency fixed-rate pass-throughs), asset-backed securities and collateralized mortgage-backed securities (agency and non-agency). Effective December 11, 2025, derivative instruments that provide investment exposure to the investments above or exposure to one or more market risk factors associated with such investments are included in the fund's 80% policy, consistent with the fund's investment policies and limitations with respect to investments in derivatives.   Using statistical sampling techniques based on duration, maturity, interest rate sensitivity, security structure, and credit quality to attempt to replicate the returns of the Bloomberg U.S. Aggregate Bond Index using a smaller number of securities. Engaging in transactions that have a leveraging effect on the fund, including investments in derivatives - such as swaps (interest rate, total return, and credit default), options, and futures contracts - and forward-settling securities, to adjust the fund's risk exposure. Investing in Fidelity's Central funds (specialized investment vehicles used by Fidelity® funds to invest in particular security types or investment disciplines) consistent with the asset classes discussed above.
Bar Chart and Performance Table [Heading]		Performance
Performance Narrative [Text Block]		The following information is intended to help you understand the risks of investing in the fund. The information illustrates the changes in the performance of the fund's shares from year to year and compares the performance of the fund's shares to the performance of a securities market index over various periods of time. The index description appears in the "Additional Index Information" section of the prospectus. Past performance (before and after taxes) is not an indication of future performance. The performance shown does not reflect the impact of any fees paid at the fee-based account or plan level. Visit www.401k.com and log in or www.fidelity.com for more recent performance information.
Performance Information Illustrates Variability of Returns [Text]		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]		www.401k.com and log in or www.fidelity.com
Performance Past Does Not Indicate Future [Text]		Past performance (before and after taxes) is not an indication of future performance.
Bar Chart [Heading]		Year-by-Year Returns
Year to Date Return, Label [Optional Text]		Year-to-Date Return
Bar Chart, Year to Date Return, Date		Sep. 30, 2025
Bar Chart, Year to Date Return		6.16%
Highest Quarterly Return, Label [Optional Text]		Highest Quarter Return
Highest Quarterly Return, Date		Dec. 31, 2023
Highest Quarterly Return		6.64%
Lowest Quarterly Return, Label [Optional Text]		Lowest Quarter Return
Lowest Quarterly Return, Date		Mar. 31, 2022
Lowest Quarterly Return		(5.79%)
Performance Table Heading		Average Annual Returns
Performance Table Uses Highest Federal Rate		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		The after-tax returns shown are not relevant if you hold your shares in a retirement account or in another tax-deferred arrangement, such as an employee benefit plan (profit sharing, 401(k), or 403(b) plan).
Performance Table Explanation after Tax Higher		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		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, such as an employee benefit plan (profit sharing, 401(k), or 403(b) plan). 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.
FidelityFlexUSBondIndexFund-PRO | Fidelity Flex U.S. Bond Index Fund | After Taxes on Distributions | Fidelity Flex U.S. Bond Index Fund
Prospectus Line Items
Average Annual Return, Label [Optional Text]			Return After Taxes on Distributions
Average Annual Return, Percent			(0.14%)											(1.38%)					0.22%	[7]
FidelityFlexUSBondIndexFund-PRO | Fidelity Flex U.S. Bond Index Fund | After Taxes on Distributions and Sales | Fidelity Flex U.S. Bond Index Fund
Prospectus Line Items
Average Annual Return, Label [Optional Text]			Return After Taxes on Distributions and Sale of Fund Shares
Average Annual Return, Percent			0.80%											(0.67%)					0.56%	[7]
FidelityFlexUSBondIndexFund-PRO | Fidelity Flex U.S. Bond Index Fund | LB001
Prospectus Line Items
Average Annual Return, Label [Optional Text]			Bloomberg U.S. Aggregate Bond Index
Average Annual Return, Percent			1.25%											(0.33%)					1.37%
FidelityUSBondIndexFund-PRO | Fidelity U.S. Bond Index Fund | Fidelity U.S. Bond Index Fund
Prospectus Line Items
Management Fees (as a percentage of Assets)		0.025%
Distribution and Service (12b-1) Fees		0.00%
Other Expenses (as a percentage of Assets):		0.00%
Expenses (as a percentage of Assets)		0.025%
Expense Example, with Redemption, 1 Year		$ 3
Expense Example, with Redemption, 3 Years		8
Expense Example, with Redemption, 5 Years		14
Expense Example, with Redemption, 10 Years		$ 32
Average Annual Return, Label [Optional Text]			Return Before Taxes
Average Annual Return, Percent			1.34%											(0.31%)									1.33%
Annual Return [Percent]				1.34%	5.55%	(13.04%)	(1.79%)	7.80%	8.48%	0.03%	3.49%	2.51%	0.63%
FidelityUSBondIndexFund-PRO | Fidelity U.S. Bond Index Fund
Prospectus Line Items
Risk/Return [Heading]		Fund Summary Fund: Fidelity® U.S. Bond Index Fund
Objective [Heading]		Investment Objective
Objective, Primary [Text Block]		Fidelity® U.S. Bond Index Fund seeks to provide investment results that correspond to the aggregate price and interest performance of the debt securities in the Bloomberg U.S. Aggregate Bond Index.
Expense Heading [Optional Text]		Fee Table
Expense Narrative [Text Block]		The following table describes the fees and expenses that may be incurred when you buy, hold, and sell shares of the fund. You may pay other fees, such as brokerage commissions, which are not reflected in the tables and examples below.
Shareholder Fees Caption [Optional Text]		Shareholder fees
Shareholder Fee, Other		$ 0
Operating Expenses Caption [Optional Text]		Annual Operating Expenses
Portfolio Turnover [Heading]		Portfolio Turnover
Portfolio Turnover [Text Block]		The fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when fund shares are held in a taxable account. These costs, which are not reflected in annual operating expenses or in the example, affect the fund's performance. During the most recent fiscal year, the fund's portfolio turnover rate was 45 % of the average value of its portfolio.
Portfolio Turnover, Rate		45.00%
Expense Example Narrative [Text Block]		This example helps compare the cost of investing in the fund with the cost of investing in other funds. Let's say, hypothetically, that the annual return for shares of the fund is 5% and that the 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]		Principal Investment Strategies
Strategy Narrative [Text Block]		Normally investing at least 80% of assets in bonds included in the Bloomberg U.S. Aggregate Bond Index. The Bloomberg U.S. Aggregate Bond Index is a broad based, flagship benchmark that measures the investment grade, US dollar-denominated, fixed-rate taxable bond market. The index includes Treasuries, government-related and corporate securities, mortgage-backed securities (agency fixed-rate pass-throughs), asset-backed securities and collateralized mortgage-backed securities (agency and non-agency). Effective December 11, 2025, derivative instruments that provide investment exposure to the investments above or exposure to one or more market risk factors associated with such investments are included in the fund's 80% policy, consistent with the fund's investment policies and limitations with respect to investments in derivatives.   Using statistical sampling techniques based on duration, maturity, interest rate sensitivity, security structure, and credit quality to attempt to replicate the returns of the Bloomberg U.S. Aggregate Bond Index using a smaller number of securities. Engaging in transactions that have a leveraging effect on the fund, including investments in derivatives - such as swaps (interest rate, total return, and credit default), options, and futures contracts - and forward-settling securities, to adjust the fund's risk exposure. Investing in Fidelity's Central funds (specialized investment vehicles used by Fidelity® funds to invest in particular security types or investment disciplines) consistent with the asset classes discussed above.
Bar Chart and Performance Table [Heading]		Performance
Performance Narrative [Text Block]		The following information is intended to help you understand the risks of investing in the fund. The information illustrates the changes in the performance of the fund's shares from year to year and compares the performance of the fund's shares to the performance of a securities market index over various periods of time. The index description appears in the "Additional Index Information" section of the prospectus. Past performance (before and after taxes) is not an indication of future performance. Visit www.fidelity.com for more recent performance information.
Performance Information Illustrates Variability of Returns [Text]		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]		www.fidelity.com
Performance Past Does Not Indicate Future [Text]		Past performance (before and after taxes) is not an indication of future performance.
Bar Chart [Heading]		Year-by-Year Returns
Year to Date Return, Label [Optional Text]		Year-to-Date Return
Bar Chart, Year to Date Return, Date		Sep. 30, 2025
Bar Chart, Year to Date Return		6.05%
Highest Quarterly Return, Label [Optional Text]		Highest Quarter Return
Highest Quarterly Return, Date		Dec. 31, 2023
Highest Quarterly Return		6.63%
Lowest Quarterly Return, Label [Optional Text]		Lowest Quarter Return
Lowest Quarterly Return, Date		Mar. 31, 2022
Lowest Quarterly Return		(5.88%)
Performance Table Heading		Average Annual Returns
Performance Table Uses Highest Federal Rate		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		The after-tax returns shown are not relevant if you hold your shares in a retirement account or in another tax-deferred arrangement, such as an employee benefit plan (profit sharing, 401(k), or 403(b) plan).
Performance Table Explanation after Tax Higher		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		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, such as an employee benefit plan (profit sharing, 401(k), or 403(b) plan). 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.
FidelityUSBondIndexFund-PRO | Fidelity U.S. Bond Index Fund | After Taxes on Distributions | Fidelity U.S. Bond Index Fund
Prospectus Line Items
Average Annual Return, Label [Optional Text]			Return After Taxes on Distributions
Average Annual Return, Percent			(0.04%)											(1.39%)									0.22%
FidelityUSBondIndexFund-PRO | Fidelity U.S. Bond Index Fund | After Taxes on Distributions and Sales | Fidelity U.S. Bond Index Fund
Prospectus Line Items
Average Annual Return, Label [Optional Text]			Return After Taxes on Distributions and Sale of Fund Shares
Average Annual Return, Percent			0.79%											(0.65%)									0.55%
FidelityUSBondIndexFund-PRO | Fidelity U.S. Bond Index Fund | LB001
Prospectus Line Items
Average Annual Return, Label [Optional Text]			Bloomberg U.S. Aggregate Bond Index
Average Annual Return, Percent			1.25%											(0.33%)									1.35%
FidelitySeriesShort-TermCreditFund-PRO | Fidelity Series Short-Term Credit Fund | Fidelity Series Short-Term Credit Fund
Prospectus Line Items
Management Fees (as a percentage of Assets)		0.00%
Distribution and Service (12b-1) Fees		0.00%
Other Expenses (as a percentage of Assets):		0.00%
Expenses (as a percentage of Assets)		0.00%
Expense Example, with Redemption, 1 Year		$ 0
Expense Example, with Redemption, 3 Years		0
Expense Example, with Redemption, 5 Years		0
Expense Example, with Redemption, 10 Years		$ 0
Annual Return, Inception Date		Mar. 27, 2015
Average Annual Return, Label [Optional Text]			Return Before Taxes
Average Annual Return, Percent			5.46%											2.41%									2.23%	[8]
Annual Return [Percent]				5.46%	6.07%	(3.07%)	(0.27%)	4.14%	5.07%	1.64%	1.50%	1.55%
FidelitySeriesShort-TermCreditFund-PRO | Fidelity Series Short-Term Credit Fund
Prospectus Line Items
Risk/Return [Heading]		Fund Summary Fund: Fidelity® Series Short-Term Credit Fund
Objective [Heading]		Investment Objective
Objective, Primary [Text Block]		Fidelity® Series Short-Term Credit Fund seeks to obtain a high level of current income consistent with the preservation of capital.
Expense Heading [Optional Text]		Fee Table
Expense Narrative [Text Block]		The following table describes the fees and expenses that may be incurred when you buy, hold, and sell shares of the fund.
Shareholder Fees Caption [Optional Text]		Shareholder fees
Shareholder Fee, Other		$ 0
Operating Expenses Caption [Optional Text]		Annual Operating Expenses
Portfolio Turnover [Heading]		Portfolio Turnover
Portfolio Turnover [Text Block]		The fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when fund shares are held in a taxable account. These costs, which are not reflected in annual operating expenses or in the example, affect the fund's performance. During the most recent fiscal year, the fund's portfolio turnover rate was 67 % of the average value of its portfolio.
Portfolio Turnover, Rate		67.00%
Expense Example Narrative [Text Block]		This example helps compare the cost of investing in the fund with the cost of investing in other funds. Let's say, hypothetically, that the annual return for shares of the fund is 5% and that the 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]		Principal Investment Strategies
Strategy Narrative [Text Block]		Normally investing at least 80% of assets in investment-grade debt securities (those of medium and high quality) of all types and repurchase agreements for those securities. Debt securities are used by issuers to borrow money. The issuer usually pays a fixed, variable, or floating rate of interest, and must repay the amount borrowed, usually at the maturity of the security. Debt securities include corporate bonds, government securities (including Treasury securities), repurchase agreements, money market securities, mortgage and other asset-backed securities, loans and loan participations, and other securities, such as hybrids and synthetic securities, believed to have debt-like characteristics (e.g., securities classified as Tier 2 Regulatory capital, securities that rank above share capital in an insolvency waterfall, securities with maturity dates and non-cancellable interest payment structures).  Investment grade securities in which the fund invests include securities or issuers rated at least BBB- or its equivalent by at least one nationally recognized statistical ratings organization (NRSRO), or, if unrated, determined by the Adviser to be of comparable quality. A repurchase agreement is an agreement to buy a security at one price and a simultaneous agreement to sell it back at an agreed-upon price. Effective December 11, 2025, derivative instruments that provide investment exposure to the investments above or exposure to one or more market risk factors associated with such investments are included in the fund's 80% policy, consistent with the fund's investment policies and limitations with respect to investments in derivatives.   Managing the fund to have similar overall interest rate risk to the Bloomberg U.S. Credit 1-3 Years Bond Index. Normally maintaining a dollar-weighted average maturity of three years or less. Allocating assets across different market sectors and maturities. Investing in domestic and foreign issuers. Analyzing the credit quality of the issuer, security-specific features, current and potential future valuation, and trading opportunities to select investments. Engaging in transactions that have a leveraging effect on the fund, including investments in derivatives - such as swaps (interest rate, total return, and credit default), options, and futures contracts - and forward-settling securities, to adjust the fund's risk exposure.
Bar Chart and Performance Table [Heading]		Performance
Performance Narrative [Text Block]		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 and an additional index over various periods of time. The additional index has characteristics relevant to the fund's investment strategies. Index descriptions appear in the "Additional Index Information" section of the prospectus. Past performance (before and after taxes) is not an indication of future performance. The performance shown does not reflect the impact of any fees paid at the fee-based account or plan level, if applicable. Visit www.fidelity.com for more recent performance information.
Performance Information Illustrates Variability of Returns [Text]		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 and an additional index over various periods of time.
Performance Availability Website Address [Text]		www.fidelity.com
Performance Past Does Not Indicate Future [Text]		Past performance (before and after taxes) is not an indication of future performance.
Bar Chart [Heading]		Year-by-Year Returns
Year to Date Return, Label [Optional Text]		Year-to-Date Return
Bar Chart, Year to Date Return, Date		Sep. 30, 2025
Bar Chart, Year to Date Return		4.50%
Highest Quarterly Return, Label [Optional Text]		Highest Quarter Return
Highest Quarterly Return, Date		Jun. 30, 2020
Highest Quarterly Return		4.05%
Lowest Quarterly Return, Label [Optional Text]		Lowest Quarter Return
Lowest Quarterly Return, Date		Mar. 31, 2022
Lowest Quarterly Return		(2.38%)
Performance Table Heading		Average Annual Returns
Performance Table Uses Highest Federal Rate		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		The after-tax returns shown are not relevant if you hold your shares in a retirement account or in another tax-deferred arrangement, such as an employee benefit plan (profit sharing, 401(k), or 403(b) plan).
Performance Table Explanation after Tax Higher		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		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, such as an employee benefit plan (profit sharing, 401(k), or 403(b) plan). 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.
FidelitySeriesShort-TermCreditFund-PRO | Fidelity Series Short-Term Credit Fund | After Taxes on Distributions | Fidelity Series Short-Term Credit Fund
Prospectus Line Items
Average Annual Return, Label [Optional Text]			Return After Taxes on Distributions
Average Annual Return, Percent			3.86%											1.37%									1.32%	[8]
FidelitySeriesShort-TermCreditFund-PRO | Fidelity Series Short-Term Credit Fund | After Taxes on Distributions and Sales | Fidelity Series Short-Term Credit Fund
Prospectus Line Items
Average Annual Return, Label [Optional Text]			Return After Taxes on Distributions and Sale of Fund Shares
Average Annual Return, Percent			3.31%											1.42%									1.32%	[8]
FidelitySeriesShort-TermCreditFund-PRO | Fidelity Series Short-Term Credit Fund | LB001
Prospectus Line Items
Average Annual Return, Label [Optional Text]			Bloomberg U.S. Aggregate Bond Index
Average Annual Return, Percent			1.25%											(0.33%)									1.23%
FidelitySeriesShort-TermCreditFund-PRO | Fidelity Series Short-Term Credit Fund | IX139
Prospectus Line Items
Average Annual Return, Label [Optional Text]			Bloomberg U.S. Credit 1-3 Years Bond Index
Average Annual Return, Percent			5.11%											2.04%									2.13%
FidelityCorporateBondFund-RetailPRO | Fidelity Corporate Bond Fund | Fidelity Corporate Bond Fund
Prospectus Line Items
Management Fees (as a percentage of Assets)		0.35%
Distribution and Service (12b-1) Fees		0.00%
Other Expenses (as a percentage of Assets):		0.10%
Expenses (as a percentage of Assets)		0.45%
Expense Example, with Redemption, 1 Year		$ 46
Expense Example, with Redemption, 3 Years		144
Expense Example, with Redemption, 5 Years		252
Expense Example, with Redemption, 10 Years		$ 567
Average Annual Return, Label [Optional Text]			Return Before Taxes
Average Annual Return, Percent			2.82%											0.45%									2.49%
Annual Return [Percent]				2.82%	8.79%	(16.44%)	(1.22%)	10.79%	14.46%	(2.58%)	6.82%	6.49%	(1.42%)
FidelityCorporateBondFund-RetailPRO | Fidelity Corporate Bond Fund
Prospectus Line Items
Risk/Return [Heading]		Fund Summary Fund /Class: Fidelity® Corporate Bond Fund /Fidelity® Corporate Bond Fund
Objective [Heading]		Investment Objective
Objective, Primary [Text Block]		Fidelity® Corporate Bond Fund seeks a high level of current income.
Expense Heading [Optional Text]		Fee Table
Expense Narrative [Text Block]		The following table describes the fees and expenses that may be incurred when you buy, hold, and sell shares of the fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below.
Shareholder Fees Caption [Optional Text]		Shareholder fees
Shareholder Fee, Other		$ 0
Operating Expenses Caption [Optional Text]		Annual Operating Expenses
Portfolio Turnover [Heading]		Portfolio Turnover
Portfolio Turnover [Text Block]		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 43 % of the average value of its portfolio.
Portfolio Turnover, Rate		43.00%
Expense Example Narrative [Text Block]		This example helps compare the cost of investing in the fund with the cost of investing in other funds. Let's say, hypothetically, that the annual return for shares of the fund is 5% and that the 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]		Principal Investment Strategies
Strategy Narrative [Text Block]		Normally investing at least 80% of assets in corporate bonds and other corporate debt securities and repurchase agreements for those securities. Corporate debt securities are bonds and other debt securities issued by corporations and other business structures to borrow money. The issuer usually pays a fixed, variable, or floating rate of interest, and must repay the amount borrowed, usually at the maturity of the security. Corporate debt securities include repurchase agreements with corporate counterparties and other securities, such as hybrids and synthetic securities, believed to have corporate debt-like characteristics, (e.g., securities classified as Tier 2 Regulatory capital, securities that rank above share capital in an insolvency waterfall, securities with maturity dates and non-cancellable interest payment structures). A repurchase agreement is an agreement to buy a security at one price and a simultaneous agreement to sell it back at an agreed-upon price. Effective December 11, 2025, derivative instruments that provide investment exposure to the investments above or exposure to one or more market risk factors associated with such investments are included in the fund's 80% policy, consistent with the fund's investment policies and limitations with respect to investments in derivatives.   Normally investing primarily in investment-grade corporate debt securities and repurchase agreements for those securities. Managing the fund to have similar overall interest rate risk to the Bloomberg U.S. Credit Bond Index. Investing in domestic and foreign issuers. Analyzing the credit quality of the issuer, security-specific features, current and potential future valuation, and trading opportunities to select investments. Investing in lower-quality debt securities (those of less than investment-grade quality, also referred to as high yield debt securities or junk bonds). Engaging in transactions that have a leveraging effect on the fund, including investments in derivatives - such as swaps (interest rate, total return, and credit default), options, and futures contracts - and forward-settling securities, to adjust the fund's risk exposure. Investing in Fidelity's Central funds (specialized investment vehicles used by Fidelity® funds to invest in particular security types or investment disciplines) consistent with the asset classes discussed above.
Bar Chart and Performance Table [Heading]		Performance
Performance Narrative [Text Block]		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 and an additional index over various periods of time. The additional index has characteristics relevant to the fund's investment strategies. Index descriptions appear in the "Additional Index Information" section of the prospectus. Past performance (before and after taxes) is not an indication of future performance. Visit www.fidelity.com for more recent performance information.
Performance Information Illustrates Variability of Returns [Text]		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 and an additional index over various periods of time.
Performance Availability Website Address [Text]		www.fidelity.com
Performance Past Does Not Indicate Future [Text]		Past performance (before and after taxes) is not an indication of future performance.
Bar Chart [Heading]		Year-by-Year Returns
Year to Date Return, Label [Optional Text]		Year-to-Date Return
Bar Chart, Year to Date Return, Date		Sep. 30, 2025
Bar Chart, Year to Date Return		7.00%
Highest Quarterly Return, Label [Optional Text]		Highest Quarter Return
Highest Quarterly Return, Date		Jun. 30, 2020
Highest Quarterly Return		10.23%
Lowest Quarterly Return, Label [Optional Text]		Lowest Quarter Return
Lowest Quarterly Return, Date		Jun. 30, 2022
Lowest Quarterly Return		(7.73%)
Performance Table Heading		Average Annual Returns
Performance Table Uses Highest Federal Rate		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		The after-tax returns shown are not relevant if you hold your shares in a retirement account or in another tax-deferred arrangement, such as an employee benefit plan (profit sharing, 401(k), or 403(b) plan).
Performance Table Explanation after Tax Higher		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		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, such as an employee benefit plan (profit sharing, 401(k), or 403(b) plan). 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.
FidelityCorporateBondFund-RetailPRO | Fidelity Corporate Bond Fund | After Taxes on Distributions | Fidelity Corporate Bond Fund
Prospectus Line Items
Average Annual Return, Label [Optional Text]			Return After Taxes on Distributions
Average Annual Return, Percent			1.30%											(0.92%)									1.08%
FidelityCorporateBondFund-RetailPRO | Fidelity Corporate Bond Fund | After Taxes on Distributions and Sales | Fidelity Corporate Bond Fund
Prospectus Line Items
Average Annual Return, Label [Optional Text]			Return After Taxes on Distributions and Sale of Fund Shares
Average Annual Return, Percent			1.77%											(0.19%)									1.31%
FidelityCorporateBondFund-RetailPRO | Fidelity Corporate Bond Fund | LB004
Prospectus Line Items
Average Annual Return, Label [Optional Text]			Bloomberg U.S. Credit Bond Index
Average Annual Return, Percent			2.03%											0.23%									2.29%
FidelityCorporateBondFund-RetailPRO | Fidelity Corporate Bond Fund | LB001
Prospectus Line Items
Average Annual Return, Label [Optional Text]			Bloomberg U.S. Aggregate Bond Index
Average Annual Return, Percent			1.25%											(0.33%)									1.35%
FidelitySeriesGovernmentMoneyMarketFund-PRO | Fidelity Series Government Money Market Fund | Fidelity Series Government Money Market Fund
Prospectus Line Items
Management Fees (as a percentage of Assets)		0.00%
Distribution and Service (12b-1) Fees		0.00%
Other Expenses (as a percentage of Assets):		0.00%
Expenses (as a percentage of Assets)		0.00%
Expense Example, with Redemption, 1 Year		$ 0
Expense Example, with Redemption, 3 Years		0
Expense Example, with Redemption, 5 Years		0
Expense Example, with Redemption, 10 Years		$ 0
Annual Return, Inception Date		Apr. 22, 2016
Average Annual Return, Label [Optional Text]			Fidelity® Series Government Money Market Fund
Average Annual Return, Percent			5.37%											2.54%							2.06%
Annual Return [Percent]				5.37%	5.22%	1.67%	0.08%	0.50%	2.27%	1.90%	0.86%
FidelitySeriesGovernmentMoneyMarketFund-PRO | Fidelity Series Government Money Market Fund
Prospectus Line Items
Risk/Return [Heading]		Fund Summary Fund: Fidelity® Series Government Money Market Fund
Objective [Heading]		Investment Objective
Objective, Primary [Text Block]		Fidelity® Series Government Money Market Fund seeks as high a level of current income as is consistent with preservation of capital and liquidity.
Expense Heading [Optional Text]		Fee Table
Expense Narrative [Text Block]		The following table describes the fees and expenses that may be incurred when you buy, hold, and sell shares of the fund.
Shareholder Fees Caption [Optional Text]		Shareholder fees
Shareholder Fee, Other		$ 0
Operating Expenses Caption [Optional Text]		Annual Operating Expenses
Expense Example Narrative [Text Block]		This example helps compare the cost of investing in the fund with the cost of investing in other funds. Let's say, hypothetically, that the annual return for shares of the fund is 5% and that the 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]		Principal Investment Strategies
Strategy Narrative [Text Block]		Normally investing at least 99.5% of total assets in cash, U.S. Government securities and/or repurchase agreements that are collateralized fully (i.e., collateralized by cash or government securities). Investing in U.S. Government securities issued by entities that are chartered or sponsored by Congress but whose securities are neither issued nor guaranteed by the U.S. Treasury. Investing in compliance with industry-standard regulatory requirements for money market funds for the quality, maturity, liquidity, and diversification of investments. In addition, the fund normally invests at least 80% of its assets in U.S. Government securities and repurchase agreements for those securities. U.S. Government securities are high-quality securities issued or guaranteed by the U.S. Treasury or by an agency or instrumentality of the U.S. Government. U.S. Government securities may be backed by the full faith and credit of the U.S. Treasury, the right to borrow from the U.S. Treasury, or the agency or instrumentality issuing or guaranteeing the security. Certain issuers of U.S. Government securities, including Fannie Mae, Freddie Mac, and the Federal Home Loan Banks, are sponsored or chartered by Congress but their securities are neither issued nor guaranteed by the U.S. Treasury. The issuer usually pays a fixed, variable, or floating rate of interest, and must repay the amount borrowed, usually at the maturity of the security. A repurchase agreement is an agreement to buy a security at one price and a simultaneous agreement to sell it back at an agreed-upon price. A repurchase agreement entered into by the fund may be collateralized by U.S. Government securities or cash.
Bar Chart and Performance Table [Heading]		Performance
Performance Narrative [Text Block]		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.   Past performance is not an indication of future performance. The performance shown does not reflect the impact of any fees paid at the fee-based account or plan level, if applicable. Visit www.fidelity.com for more recent performance information.
Performance Information Illustrates Variability of Returns [Text]		The information illustrates the changes in the performance of the fund's shares from year to year.
Performance Availability Website Address [Text]		www.fidelity.com
Performance Past Does Not Indicate Future [Text]		Past performance is not an indication of future performance.
Bar Chart [Heading]		Year-by-Year Returns
Year to Date Return, Label [Optional Text]		Year-to-Date Return
Bar Chart, Year to Date Return, Date		Sep. 30, 2025
Bar Chart, Year to Date Return		3.34%
Highest Quarterly Return, Label [Optional Text]		Highest Quarter Return
Highest Quarterly Return, Date		Dec. 31, 2023
Highest Quarterly Return		1.37%
Lowest Quarterly Return, Label [Optional Text]		Lowest Quarter Return
Lowest Quarterly Return, Date		Jun. 30, 2021
Lowest Quarterly Return		0.02%
Performance Table Heading		Average Annual Returns
Document Type		485BPOS
Registrant Name		Fidelity Salem Street Trust

[1] A Class A and Class M purchases of $1 million or more will not be subject to a front-end sales charge. Such Class A and Class M purchases may be subject, upon redemption, to a contingent deferred sales charge (CDSC) of 0.75% and 0.25%, respectively.

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

[3] A Fidelity Management & Research Company LLC (FMR) has contractually agreed to reimburse Class Z of the fund to the extent that total operating expenses (excluding interest, certain taxes, fees and expenses of the Independent Trustees, extraordinary expenses, and acquired fund fees and expenses (including fees and expenses associated with a wholly owned subsidiary), if any, as well as non-operating expenses such as brokerage commissions and fees and expenses associated with the fund's securities lending program, if applicable), as a percentage of its average net assets, exceed 0.36% (the Expense Cap). If at any time during the current fiscal year expenses for Class Z of the fund fall below the Expense Cap, FMR reserves the right to recoup through the end of the fiscal year any expenses that were reimbursed during the current fiscal year up to, but not in excess of, the Expense Cap. This arrangement will remain in effect through December 31, 2026 . FMR may not terminate this arrangement before the expiration date without the approval of the Board of Trustees and may extend it in its discretion after that date.

[4] A From October 2, 2018 .

[5] A From April 26, 2019 .

[6] A The fund is available only to certain fee-based accounts and advisory programs offered by Fidelity. Advisory account clients, retirement plans, plan sponsors and/or plan participants typically pay an advisory fee that generally covers investment advisory and administrative services.

[7] A From March 9, 2017 .

[8] A From March 27, 2015 .

[9] A From April 22, 2016 .