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 580 % of the average value of its portfolio.

Portfolio Turnover, Rate

580.00%

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 securitized debt securities (those of medium and high quality) and repurchase agreements for those securities. Securitized debt securities are interests in pools of mortgages, loans, receivables, or other assets, and include such instruments as mortgage-backed securities, commercial mortgage-backed securities, and other asset-backed securities that are issued by the U.S. Government, its agencies or instrumentalities, foreign governments, financial institutions, trusts and corporations. Payment of principal or interest on securitized debt instruments generally depends on the cash flows generated by the underlying assets and may be supported by letters of credit, surety bonds, or other credit enhancements. 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. 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. 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. Managing the fund to have similar overall interest rate risk to the Bloomberg U.S. Securitized 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. 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.

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, 2026

Bar Chart, Year to Date Return

(2.61%)

Highest Quarterly Return, Label [Optional Text]

Highest Quarter Return

Highest Quarterly Return, Date

Dec. 31, 2023

Highest Quarterly Return

7.56%

Lowest Quarterly Return, Label [Optional Text]

Lowest Quarter Return

Lowest Quarterly Return, Date

Mar. 31, 2022

Lowest Quarterly Return

(5.17%)

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.

FidelitySeriesInvestmentGradeSecuritizedFund-PRO | Fidelity Series Investment Grade Securitized Fund | After Taxes on Distributions | Fidelity Series Investment Grade Securitized Fund

Prospectus Line Items

Average Annual Return, Label [Optional Text]

Return After Taxes on Distributions

Average Annual Return, Percent

6.78%

(0.82%)

0.74%

^[2]

FidelitySeriesInvestmentGradeSecuritizedFund-PRO | Fidelity Series Investment Grade Securitized Fund | After Taxes on Distributions and Sales | Fidelity Series Investment Grade Securitized Fund

Prospectus Line Items

Average Annual Return, Label [Optional Text]

Return After Taxes on Distributions and Sale of Fund Shares

Average Annual Return, Percent

5.13%

(0.20%)

1.02%

^[2]

FidelitySeriesInvestmentGradeSecuritizedFund-PRO | Fidelity Series Investment Grade Securitized Fund | LB371

Prospectus Line Items

Average Annual Return, Label [Optional Text]

Bloomberg U.S. Securitized Index

Average Annual Return, Percent

8.49%

0.22%

1.78%

FidelitySeriesInvestmentGradeSecuritizedFund-PRO | Fidelity Series Investment Grade Securitized Fund | LB001

Prospectus Line Items

Average Annual Return, Label [Optional Text]

Bloomberg U.S. Aggregate Bond Index

Average Annual Return, Percent

7.30%

(0.36%)

2.04%

FidelityAdvisorLimitedTermBondFund-RetailPRO | Fidelity Advisor Limited Term Bond Fund | Fidelity Limited Term Bond Fund

Prospectus Line Items

Management Fees (as a percentage of Assets)

0.20%

Distribution and Service (12b-1) Fees

0.00%

Other Expenses (as a percentage of Assets):

0.10%

Expenses (as a percentage of Assets)

0.30%

Expense Example, with Redemption, 1 Year

$ 31

Expense Example, with Redemption, 3 Years

Expense Example, with Redemption, 5 Years

169

Expense Example, with Redemption, 10 Years

$ 381

Average Annual Return, Label [Optional Text]

Return Before Taxes

Average Annual Return, Percent

6.68%

2.03%

2.63%

Annual Return [Percent]

6.68%

4.91%

6.26%

(5.87%)

(1.24%)

5.16%

6.03%

0.71%

1.88%

2.51%

FidelityAdvisorLimitedTermBondFund-RetailPRO | Fidelity Advisor Limited Term Bond Fund

Prospectus Line Items

Risk/Return [Heading]

Fund Summary Fund /Class: Fidelity Advisor® Limited Term Bond Fund /Fidelity® Limited Term Bond Fund

Objective [Heading]

Investment Objective

Objective, Primary [Text Block]

Fidelity Advisor® Limited Term Bond Fund seeks to provide a high rate of income.

Expense Heading [Optional Text]

Fee Table

Expense Narrative [Text Block]

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]

Portfolio Turnover, Rate

81.00%

Expense Example Narrative [Text Block]

Strategy [Heading]

Principal Investment Strategies

Strategy Narrative [Text Block]

Normally investing at least 80% of assets in debt securities 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). 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. 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. Allocating the fund's assets across investment-grade, high yield, and emerging markets debt securities. Using the Fidelity Limited Term Composite Index℠ as a guide in allocating assets across the investment-grade and high yield asset classes. Emerging markets include countries that have an emerging stock market as defined by MSCI, countries or markets with low- to middle-income economies as classified by the World Bank, and other countries or markets that the Adviser identifies as having similar emerging markets characteristics. Investing up to 30% of assets in lower-quality debt securities (those of less than investment-grade quality, also referred to as high yield debt securities or junk bonds). Normally maintaining a dollar-weighted average maturity between two and five years. Managing the fund to have similar overall interest rate risk to the index. Investing in domestic and foreign issuers. Allocating assets across different asset classes, market sectors, and maturities. Investing in collateralized loan obligations (CLO). Analyzing the credit quality of the issuer, the issuer's potential for success, the credit, currency, and economic risks of the security and its 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, a hypothetical composite of market indexes, and an additional index over various periods of time. The hypothetical composite of market indexes and additional index have 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, a hypothetical composite of market indexes, 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, 2026

Bar Chart, Year to Date Return

(0.22%)

Highest Quarterly Return, Label [Optional Text]

Highest Quarter Return

Highest Quarterly Return, Date

Jun. 30, 2020

Highest Quarterly Return

4.56%

Lowest Quarterly Return, Label [Optional Text]

Lowest Quarter Return

Lowest Quarterly Return, Date

Mar. 31, 2022

Lowest Quarterly Return

(3.65%)

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

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

FidelityAdvisorLimitedTermBondFund-RetailPRO | Fidelity Advisor Limited Term Bond Fund | After Taxes on Distributions | Fidelity Limited Term Bond Fund

Prospectus Line Items

Average Annual Return, Label [Optional Text]

Return After Taxes on Distributions

Average Annual Return, Percent

4.98%

0.99%

1.67%

FidelityAdvisorLimitedTermBondFund-RetailPRO | Fidelity Advisor Limited Term Bond Fund | After Taxes on Distributions and Sales | Fidelity Limited Term 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

3.93%

1.11%

1.61%

FidelityAdvisorLimitedTermBondFund-RetailPRO | Fidelity Advisor Limited Term Bond Fund | LB001

Prospectus Line Items

Average Annual Return, Label [Optional Text]

Bloomberg U.S. Aggregate Bond Index

Average Annual Return, Percent

7.30%

(0.36%)

2.01%

FidelityAdvisorLimitedTermBondFund-RetailPRO | Fidelity Advisor Limited Term Bond Fund | F1871

Prospectus Line Items

Average Annual Return, Label [Optional Text]

Fidelity Limited Term Composite Index℠

Average Annual Return, Percent

6.67%

2.03%

2.67%

FidelityAdvisorLimitedTermBondFund-RetailPRO | Fidelity Advisor Limited Term Bond Fund | LB087

Prospectus Line Items

Average Annual Return, Label [Optional Text]

Bloomberg U.S. 1-5 Year Government/Credit Bond Index

Average Annual Return, Percent

6.11%

1.56%

2.17%

FidelityAdvisorLimitedTermBondFund-AMCIZPRO | Fidelity Advisor Limited Term Bond Fund | Fidelity Advisor Limited Term Bond Fund - Class A

Prospectus Line Items

Maximum Cumulative Sales Charge (as a percentage of Offering Price)

2.75%

Maximum Deferred Sales Charge (as a percentage)

^[3]

0.00%

Management Fees (as a percentage of Assets)

0.20%

Distribution and Service (12b-1) Fees

0.25%

Other Expenses (as a percentage of Assets):

0.15%

Expenses (as a percentage of Assets)

0.60%

Fee Waiver or Reimbursement

(0.00%)

Net Expenses (as a percentage of Assets)

0.60%

Expenses Deferred Charges [Text Block]

Purchases of $250,000 or more will not be subject to a front-end sales charge, but may be subject to a 0.50% contingent deferred sales charge (CDSC) if the intermediary firm has elected an upfront finder's fee at the time the shares are purchased, or a 0.75% CDSC if the shares purchased are recordkept in a Fidelity Advisor ® 401(k) Retirement Plan.

Expense Example, with Redemption, 1 Year

$ 335

Expense Example, with Redemption, 3 Years

462

Expense Example, with Redemption, 5 Years

601

Expense Example, with Redemption, 10 Years

1,004

Expense Example, No Redemption, 1 Year

335

Expense Example, No Redemption, 3 Years

462

Expense Example, No Redemption, 5 Years

601

Expense Example, No Redemption, 10 Years

$ 1,004

Average Annual Return, Label [Optional Text]

Return Before Taxes

Average Annual Return, Percent

3.45%

1.16%

2.03%

Annual Return [Percent]

6.37%

4.60%

5.95%

(6.17%)

(1.54%)

4.85%

5.72%

0.40%

1.57%

2.11%

FidelityAdvisorLimitedTermBondFund-AMCIZPRO | Fidelity Advisor Limited Term Bond Fund | Fidelity Advisor Limited Term Bond Fund - Class M

Prospectus Line Items

Maximum Cumulative Sales Charge (as a percentage of Offering Price)

2.75%

Maximum Deferred Sales Charge (as a percentage)

^[4]

0.00%

Management Fees (as a percentage of Assets)

0.20%

Distribution and Service (12b-1) Fees

0.25%

Other Expenses (as a percentage of Assets):

0.15%

Expenses (as a percentage of Assets)

0.60%

Fee Waiver or Reimbursement

(0.00%)

Net Expenses (as a percentage of Assets)

0.60%

Expenses Deferred Charges [Text Block]

Purchases of $250,000 or more will not be subject to a front-end sales charge but may be subject to a 0.25% CDSC if a finder's fee is paid at the time the shares are purchased.

Expense Example, with Redemption, 1 Year

$ 335

Expense Example, with Redemption, 3 Years

462

Expense Example, with Redemption, 5 Years

601

Expense Example, with Redemption, 10 Years

1,004

Expense Example, No Redemption, 1 Year

335

Expense Example, No Redemption, 3 Years

462

Expense Example, No Redemption, 5 Years

601

Expense Example, No Redemption, 10 Years

$ 1,004

Average Annual Return, Label [Optional Text]

Return Before Taxes

Average Annual Return, Percent

3.36%

1.16%

2.03%

FidelityAdvisorLimitedTermBondFund-AMCIZPRO | Fidelity Advisor Limited Term Bond Fund | Fidelity Advisor Limited Term 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)

^[5]

1.00%

Management Fees (as a percentage of Assets)

0.20%

Distribution and Service (12b-1) Fees

1.00%

Other Expenses (as a percentage of Assets):

0.17%

Expenses (as a percentage of Assets)

1.37%

Fee Waiver or Reimbursement

(0.00%)

Net Expenses (as a percentage of Assets)

1.37%

Expenses Deferred Charges [Text Block]

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

Expense Example, with Redemption, 1 Year

$ 239

Expense Example, with Redemption, 3 Years

434

Expense Example, with Redemption, 5 Years

750

Expense Example, with Redemption, 10 Years

1,435

Expense Example, No Redemption, 1 Year

139

Expense Example, No Redemption, 3 Years

434

Expense Example, No Redemption, 5 Years

750

Expense Example, No Redemption, 10 Years

$ 1,435

Average Annual Return, Label [Optional Text]

Return Before Taxes

Average Annual Return, Percent

4.47%

0.94%

1.68%

FidelityAdvisorLimitedTermBondFund-AMCIZPRO | Fidelity Advisor Limited Term Bond Fund | Fidelity Advisor Limited Term 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)

0.20%

Distribution and Service (12b-1) Fees

0.00%

Other Expenses (as a percentage of Assets):

0.15%

Expenses (as a percentage of Assets)

0.35%

Fee Waiver or Reimbursement

^[6]

(0.05%)

Net Expenses (as a percentage of Assets)

0.30%

Expense Example, with Redemption, 1 Year

$ 31

Expense Example, with Redemption, 3 Years

106

Expense Example, with Redemption, 5 Years

190

Expense Example, with Redemption, 10 Years

437

Expense Example, No Redemption, 1 Year

Expense Example, No Redemption, 3 Years

106

Expense Example, No Redemption, 5 Years

190

Expense Example, No Redemption, 10 Years

$ 437

Average Annual Return, Label [Optional Text]

Return Before Taxes

Average Annual Return, Percent

6.68%

2.01%

2.59%

FidelityAdvisorLimitedTermBondFund-AMCIZPRO | Fidelity Advisor Limited Term Bond Fund | Fidelity Advisor Limited Term 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)

0.20%

Distribution and Service (12b-1) Fees

0.00%

Other Expenses (as a percentage of Assets):

0.05%

Expenses (as a percentage of Assets)

0.25%

Fee Waiver or Reimbursement

(0.00%)

Net Expenses (as a percentage of Assets)

0.25%

Expense Example, with Redemption, 1 Year

$ 26

Expense Example, with Redemption, 3 Years

Expense Example, with Redemption, 5 Years

141

Expense Example, with Redemption, 10 Years

318

Expense Example, No Redemption, 1 Year

Expense Example, No Redemption, 3 Years

Expense Example, No Redemption, 5 Years

141

Expense Example, No Redemption, 10 Years

$ 318

Annual Return, Inception Date

Oct. 02, 2018

Average Annual Return, Label [Optional Text]

Return Before Taxes

Average Annual Return, Percent

6.74%

2.10%

3.09%

^[7]

FidelityAdvisorLimitedTermBondFund-AMCIZPRO | Fidelity Advisor Limited Term Bond Fund

Prospectus Line Items

Risk/Return [Heading]

Fund Summary Fund /Class: Fidelity Advisor® Limited Term Bond Fund /A, M, C, I, Z

Objective [Heading]

Investment Objective

Objective, Primary [Text Block]

Fidelity Advisor® Limited Term Bond Fund seeks to provide a high rate of 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 36 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, 2027

Portfolio Turnover [Heading]

Portfolio Turnover

Portfolio Turnover [Text Block]

Portfolio Turnover, Rate

81.00%

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 36 of the prospectus

Expense Breakpoint, Minimum Investment Required [Amount]

$ 50,000

Expense Example Narrative [Text Block]

Strategy [Heading]

Principal Investment Strategies

Strategy Narrative [Text Block]

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, a hypothetical composite of market indexes, and an additional index over various periods of time. The hypothetical composite of market indexes and additional index have 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, a hypothetical composite of market indexes, 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, 2026

Bar Chart, Year to Date Return

(0.45%)

Highest Quarterly Return, Label [Optional Text]

Highest Quarter Return

Highest Quarterly Return, Date

Jun. 30, 2020

Highest Quarterly Return

4.50%

Lowest Quarterly Return, Label [Optional Text]

Lowest Quarter Return

Lowest Quarterly Return, Date

Mar. 31, 2022

Lowest Quarterly Return

(3.73%)

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

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.

FidelityAdvisorLimitedTermBondFund-AMCIZPRO | Fidelity Advisor Limited Term Bond Fund | After Taxes on Distributions | Fidelity Advisor Limited Term Bond Fund - Class A

Prospectus Line Items

Average Annual Return, Label [Optional Text]

Return After Taxes on Distributions

Average Annual Return, Percent

1.92%

0.24%

1.19%

FidelityAdvisorLimitedTermBondFund-AMCIZPRO | Fidelity Advisor Limited Term Bond Fund | After Taxes on Distributions and Sales | Fidelity Advisor Limited Term 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

2.02%

0.49%

1.19%

FidelityAdvisorLimitedTermBondFund-AMCIZPRO | Fidelity Advisor Limited Term Bond Fund | LB001

Prospectus Line Items

Average Annual Return, Label [Optional Text]

Bloomberg U.S. Aggregate Bond Index

Average Annual Return, Percent

7.30%

(0.36%)

2.01%

FidelityAdvisorLimitedTermBondFund-AMCIZPRO | Fidelity Advisor Limited Term Bond Fund | F1871

Prospectus Line Items

Average Annual Return, Label [Optional Text]

Fidelity Limited Term Composite Index℠

Average Annual Return, Percent

6.67%

2.03%

2.67%

FidelityAdvisorLimitedTermBondFund-AMCIZPRO | Fidelity Advisor Limited Term Bond Fund | LB087

Prospectus Line Items

Average Annual Return, Label [Optional Text]

Bloomberg U.S. 1-5 Year Government/Credit Bond Index

Average Annual Return, Percent

6.11%

1.56%

2.17%

FidelityAdvisorMortgageSecuritiesFund-RetailPRO | Fidelity Advisor Mortgage Securities Fund | Fidelity Mortgage Securities Fund

Prospectus Line Items

Management Fees (as a percentage of Assets)

0.28%

Distribution and Service (12b-1) Fees

0.00%

Other Expenses (as a percentage of Assets):

0.17%

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

8.27%

(0.07%)

1.52%

Annual Return [Percent]

8.27%

1.01%

4.90%

(12.21%)

(1.04%)

4.40%

6.41%

0.78%

2.34%

1.86%

FidelityAdvisorMortgageSecuritiesFund-RetailPRO | Fidelity Advisor Mortgage Securities Fund

Prospectus Line Items

Risk/Return [Heading]

Fund Summary Fund /Class: Fidelity Advisor® Mortgage Securities Fund /Fidelity® Mortgage Securities Fund

Objective [Heading]

Investment Objective

Objective, Primary [Text Block]

Fidelity Advisor® Mortgage Securities Fund seeks a high level of current income, consistent with prudent investment risk. In seeking current income, the fund may also consider the potential for capital gain.

Expense Heading [Optional Text]

Fee Table

Expense Narrative [Text Block]

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]

Portfolio Turnover, Rate

607.00%

Expense Example Narrative [Text Block]

Strategy [Heading]

Principal Investment Strategies

Strategy Narrative [Text Block]

Normally investing at least 80% of assets in investment-grade mortgage-related securities (those of medium and high quality) and repurchase agreements for those securities. Mortgage-related securities include mortgage-backed securities (MBS) such as residential mortgage-backed securities, commercial mortgage-backed securities, stripped mortgage-backed securities, collateralized mortgage obligations, inverse floating rate obligations, mortgage pass-through securities, and other similar types of securities representing an interest in or that are secured by pools of mortgages. 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. 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. Investing in U.S. Government securities and instruments related to U.S. 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. Managing the fund to have similar overall interest rate risk to the Bloomberg U.S. MBS Index. Allocating assets across different market sectors and maturities. 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.

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]

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, 2026

Bar Chart, Year to Date Return

(3.04%)

Highest Quarterly Return, Label [Optional Text]

Highest Quarter Return

Highest Quarterly Return, Date

Dec. 31, 2023

Highest Quarterly Return

7.76%

Lowest Quarterly Return, Label [Optional Text]

Lowest Quarter Return

Lowest Quarterly Return, Date

Sep. 30, 2022

Lowest Quarterly Return

(5.46%)

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

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

FidelityAdvisorMortgageSecuritiesFund-RetailPRO | Fidelity Advisor Mortgage Securities Fund | After Taxes on Distributions | Fidelity Mortgage Securities Fund

Prospectus Line Items

Average Annual Return, Label [Optional Text]

Return After Taxes on Distributions

Average Annual Return, Percent

6.53%

(1.20%)

0.42%

FidelityAdvisorMortgageSecuritiesFund-RetailPRO | Fidelity Advisor Mortgage Securities Fund | After Taxes on Distributions and Sales | Fidelity Mortgage Securities Fund

Prospectus Line Items

Average Annual Return, Label [Optional Text]

Return After Taxes on Distributions and Sale of Fund Shares

Average Annual Return, Percent

4.86%

(0.53%)

0.69%

FidelityAdvisorMortgageSecuritiesFund-RetailPRO | Fidelity Advisor Mortgage Securities Fund | LB001

Prospectus Line Items

Average Annual Return, Label [Optional Text]

Bloomberg U.S. Aggregate Bond Index

Average Annual Return, Percent

7.30%

(0.36%)

2.01%

FidelityAdvisorMortgageSecuritiesFund-RetailPRO | Fidelity Advisor Mortgage Securities Fund | LB006

Prospectus Line Items

Average Annual Return, Label [Optional Text]

Bloomberg U.S. MBS Index

Average Annual Return, Percent

8.58%

0.15%

1.59%

FidelityLimitedTermSecuritizedCompletionFund-PRO | Fidelity Limited Term Securitized Completion Fund | Fidelity Limited Term Securitized Completion 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

Expense Example, with Redemption, 5 Years

Expense Example, with Redemption, 10 Years

$ 0

Annual Return, Inception Date

May 30, 2024

Average Annual Return, Label [Optional Text]

Return Before Taxes

Average Annual Return, Percent

6.42%

6.65%

^[8]

Annual Return [Percent]

6.42%

FidelityLimitedTermSecuritizedCompletionFund-PRO | Fidelity Limited Term Securitized Completion Fund

Prospectus Line Items

Risk/Return [Heading]

Fund Summary Fund: Fidelity® Limited Term Securitized Completion Fund

Objective [Heading]

Investment Objective

Objective, Primary [Text Block]

Fidelity® Limited Term Securitized Completion 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]

Portfolio Turnover, Rate

155.00%

Expense Example Narrative [Text Block]

Strategy [Heading]

Principal Investment Strategies

Strategy Narrative [Text Block]

Normally investing at least 80% of assets in investment-grade securitized debt securities (those of medium and high quality) and repurchase agreements for those securities. Securitized debt securities are interests in pools of mortgages, loans, receivables, or other assets, and include such instruments as mortgage-backed securities, commercial mortgage-backed securities, and other asset-backed securities that are issued by the U.S. Government, its agencies or instrumentalities, foreign governments, financial institutions, trusts and corporations. Payment of principal or interest on securitized debt instruments generally depends on the cash flows generated by the underlying assets and may be supported by letters of credit, surety bonds, or other credit enhancements. 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. 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. 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. Managing the fund to have similar overall interest rate risk to the Fidelity Limited Term Securitized Completion Fund Composite Blended 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. Normally maintaining a dollar-weighted average maturity between two and five years. Allocating assets across different market sectors and maturities. 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.

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 performance of the fund's shares over the past year and compares the performance of the fund's shares to the performance of a securities market index, a hypothetical composite of market indexes, and an additional index over various periods of time. The hypothetical composite of market indexes and additional index have 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 performance of the fund's shares over the past year and compares the performance of the fund's shares to the performance of a securities market index, a hypothetical composite of market indexes, 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, 2026

Bar Chart, Year to Date Return

0.84%

Highest Quarterly Return, Label [Optional Text]

Highest Quarter Return

Highest Quarterly Return, Date

Mar. 31, 2025

Highest Quarterly Return

1.76%

Lowest Quarterly Return, Label [Optional Text]

Lowest Quarter Return

Lowest Quarterly Return, Date

Dec. 31, 2025

Lowest Quarterly Return

1.26%

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

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

FidelityLimitedTermSecuritizedCompletionFund-PRO | Fidelity Limited Term Securitized Completion Fund | After Taxes on Distributions | Fidelity Limited Term Securitized Completion Fund

Prospectus Line Items

Average Annual Return, Label [Optional Text]

Return After Taxes on Distributions

Average Annual Return, Percent

4.46%

4.66%

^[8]

FidelityLimitedTermSecuritizedCompletionFund-PRO | Fidelity Limited Term Securitized Completion Fund | After Taxes on Distributions and Sales | Fidelity Limited Term Securitized Completion Fund

Prospectus Line Items

Average Annual Return, Label [Optional Text]

Return After Taxes on Distributions and Sale of Fund Shares

Average Annual Return, Percent

3.77%

4.23%

^[8]

FidelityLimitedTermSecuritizedCompletionFund-PRO | Fidelity Limited Term Securitized Completion Fund | LB001

Prospectus Line Items

Average Annual Return, Label [Optional Text]

Bloomberg U.S. Aggregate Bond Index

Average Annual Return, Percent

7.30%

6.70%

FidelityLimitedTermSecuritizedCompletionFund-PRO | Fidelity Limited Term Securitized Completion Fund | IXTGB

Prospectus Line Items

Average Annual Return, Label [Optional Text]

Fidelity Limited Term Securitized Completion Fund Composite Blended Index

Average Annual Return, Percent

6.24%

6.55%

FidelityLimitedTermSecuritizedCompletionFund-PRO | Fidelity Limited Term Securitized Completion Fund | LB074

Prospectus Line Items

Average Annual Return, Label [Optional Text]

Bloomberg U.S. Fixed Rate Asset-Backed Securities Index

Average Annual Return, Percent

5.93%

6.36%

FidelityAdvisorMortgageSecuritiesFund-AMCIZPRO | Fidelity Advisor Mortgage Securities Fund | Fidelity Advisor Mortgage Securities 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)

^[9]

0.00%

Management Fees (as a percentage of Assets)

0.28%

Distribution and Service (12b-1) Fees

0.25%

Other Expenses (as a percentage of Assets):

0.26%

Expenses (as a percentage of Assets)

0.79%

Fee Waiver or Reimbursement

(0.00%)

Net Expenses (as a percentage of Assets)

0.79%

Expense Example, with Redemption, 1 Year

$ 477

Expense Example, with Redemption, 3 Years

642

Expense Example, with Redemption, 5 Years

821

Expense Example, with Redemption, 10 Years

1,339

Expense Example, No Redemption, 1 Year

477

Expense Example, No Redemption, 3 Years

642

Expense Example, No Redemption, 5 Years

821

Expense Example, No Redemption, 10 Years

$ 1,339

Average Annual Return, Label [Optional Text]

Return Before Taxes

Average Annual Return, Percent

3.59%

(1.22%)

0.76%

Annual Return [Percent]

7.91%

0.64%

4.53%

(12.49%)

(1.39%)

4.06%

6.05%

0.43%

1.90%

1.61%

FidelityAdvisorMortgageSecuritiesFund-AMCIZPRO | Fidelity Advisor Mortgage Securities Fund | Fidelity Advisor Mortgage Securities 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)

^[9]

0.00%

Management Fees (as a percentage of Assets)

0.28%

Distribution and Service (12b-1) Fees

0.25%

Other Expenses (as a percentage of Assets):

0.28%

Expenses (as a percentage of Assets)

0.81%

Fee Waiver or Reimbursement

(0.00%)

Net Expenses (as a percentage of Assets)

0.81%

Expense Example, with Redemption, 1 Year

$ 479

Expense Example, with Redemption, 3 Years

648

Expense Example, with Redemption, 5 Years

832

Expense Example, with Redemption, 10 Years

1,362

Expense Example, No Redemption, 1 Year

479

Expense Example, No Redemption, 3 Years

648

Expense Example, No Redemption, 5 Years

832

Expense Example, No Redemption, 10 Years

$ 1,362

Average Annual Return, Label [Optional Text]

Return Before Taxes

Average Annual Return, Percent

3.58%

(1.21%)

0.75%

FidelityAdvisorMortgageSecuritiesFund-AMCIZPRO | Fidelity Advisor Mortgage Securities Fund | Fidelity Advisor Mortgage Securities 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)

^[10]

1.00%

Management Fees (as a percentage of Assets)

0.28%

Distribution and Service (12b-1) Fees

1.00%

Other Expenses (as a percentage of Assets):

0.32%

Expenses (as a percentage of Assets)

1.60%

Fee Waiver or Reimbursement

(0.00%)

Net Expenses (as a percentage of Assets)

1.60%

Expenses Deferred Charges [Text Block]

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

Expense Example, with Redemption, 1 Year

$ 263

Expense Example, with Redemption, 3 Years

505

Expense Example, with Redemption, 5 Years

871

Expense Example, with Redemption, 10 Years

1,683

Expense Example, No Redemption, 1 Year

163

Expense Example, No Redemption, 3 Years

505

Expense Example, No Redemption, 5 Years

871

Expense Example, No Redemption, 10 Years

$ 1,683

Average Annual Return, Label [Optional Text]

Return Before Taxes

Average Annual Return, Percent

6.10%

(1.20%)

0.55%

FidelityAdvisorMortgageSecuritiesFund-AMCIZPRO | Fidelity Advisor Mortgage Securities Fund | Fidelity Advisor Mortgage Securities 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)

0.28%

Distribution and Service (12b-1) Fees

0.00%

Other Expenses (as a percentage of Assets):

0.32%

Expenses (as a percentage of Assets)

0.60%

Fee Waiver or Reimbursement

(0.00%)

Net Expenses (as a percentage of Assets)

0.60%

Expense Example, with Redemption, 1 Year

$ 61

Expense Example, with Redemption, 3 Years

192

Expense Example, with Redemption, 5 Years

335

Expense Example, with Redemption, 10 Years

750

Expense Example, No Redemption, 1 Year

Expense Example, No Redemption, 3 Years

192

Expense Example, No Redemption, 5 Years

335

Expense Example, No Redemption, 10 Years

$ 750

Average Annual Return, Label [Optional Text]

Return Before Taxes

Average Annual Return, Percent

8.24%

(0.14%)

1.47%

FidelityAdvisorMortgageSecuritiesFund-AMCIZPRO | Fidelity Advisor Mortgage Securities Fund | Fidelity Advisor Mortgage Securities 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)

0.28%

Distribution and Service (12b-1) Fees

0.00%

Other Expenses (as a percentage of Assets):

0.12%

Expenses (as a percentage of Assets)

0.40%

Fee Waiver or Reimbursement

^[11]

(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

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

8.38%

0.03%

1.78%

^[12]

FidelityAdvisorMortgageSecuritiesFund-AMCIZPRO | Fidelity Advisor Mortgage Securities Fund

Prospectus Line Items

Risk/Return [Heading]

Fund Summary Fund /Class: Fidelity Advisor® Mortgage Securities Fund /A, M, C, I, Z

Objective [Heading]

Investment Objective

Objective, Primary [Text Block]

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 34 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, 2027

Portfolio Turnover [Heading]

Portfolio Turnover

Portfolio Turnover [Text Block]

Portfolio Turnover, Rate

607.00%

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]

Expense Breakpoint, Minimum Investment Required [Amount]

$ 50,000

Expense Example Narrative [Text Block]

Strategy [Heading]

Principal Investment Strategies

Strategy Narrative [Text Block]

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]

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, 2026

Bar Chart, Year to Date Return

(3.31%)

Highest Quarterly Return, Label [Optional Text]

Highest Quarter Return

Highest Quarterly Return, Date

Dec. 31, 2023

Highest Quarterly Return

7.70%

Lowest Quarterly Return, Label [Optional Text]

Lowest Quarter Return

Lowest Quarterly Return, Date

Sep. 30, 2022

Lowest Quarterly Return

(5.48%)

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

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

FidelityAdvisorMortgageSecuritiesFund-AMCIZPRO | Fidelity Advisor Mortgage Securities Fund | After Taxes on Distributions | Fidelity Advisor Mortgage Securities Fund - Class A

Prospectus Line Items

Average Annual Return, Label [Optional Text]

Return After Taxes on Distributions

Average Annual Return, Percent

2.07%

(2.21%)

(0.19%)

FidelityAdvisorMortgageSecuritiesFund-AMCIZPRO | Fidelity Advisor Mortgage Securities Fund | After Taxes on Distributions and Sales | Fidelity Advisor Mortgage Securities 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

2.10%

(1.34%)

0.17%

FidelityAdvisorMortgageSecuritiesFund-AMCIZPRO | Fidelity Advisor Mortgage Securities Fund | LB001

Prospectus Line Items

Average Annual Return, Label [Optional Text]

Bloomberg U.S. Aggregate Bond Index

Average Annual Return, Percent

7.30%

(0.36%)

2.01%

FidelityAdvisorMortgageSecuritiesFund-AMCIZPRO | Fidelity Advisor Mortgage Securities Fund | LB006

Prospectus Line Items

Average Annual Return, Label [Optional Text]

Bloomberg U.S. MBS Index

Average Annual Return, Percent

8.58%

0.15%

1.59%

Document Type

485BPOS

Registrant Name

Fidelity Advisor Series II

[1]	A Fidelity Management & Research Company LLC (FMR) has contractually agreed to reimburse the fund to the extent that total operating expenses (excluding interest, fees and expenses of the Independent Trustees, 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 0.003% (the Expense Cap). If at any time during the current fiscal year expenses for 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, 2029 . 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.
[2]	A From August 17, 2018 .
[3]	A Purchases of $250,000 or more will not be subject to a front-end sales charge, but may be subject to a 0.50% contingent deferred sales charge (CDSC) if the intermediary firm has elected an upfront finder's fee at the time the shares are purchased, or a 0.75% CDSC if the shares purchased are recordkept in a Fidelity Advisor ® 401(k) Retirement Plan.
[4]	B Purchases of $250,000 or more will not be subject to a front-end sales charge but may be subject to a 0.25% CDSC if a finder's fee is paid at the time the shares are purchased.
[5]	C On Class C shares redeemed less than one year after purchase.
[6]	A Fidelity Management & Research Company LLC (FMR) has contractually agreed to reimburse Class I of the fund to the extent that total operating expenses (excluding interest, certain taxes, fees and expenses of the Independent Trustees, proxy and shareholder meeting expenses, 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 0.30% (the Expense Cap). If at any time during the current fiscal year expenses for Class I 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, 2027 . 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.
[7]	A From October 2, 2018 .
[8]	A From May 30, 2024 .
[9]	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.
[10]	B On Class C shares redeemed less than one year after purchase.
[11]	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, 2027 . 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.
[12]	A From October 2, 2018 .