| Form N-CSR Cover | 12 Months Ended |
| Oct. 31, 2024 | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSR |
| Amendment Flag | false |
| Registrant Name | Fidelity Salem Street Trust |
| Entity Central Index Key | 0000035315 |
| Entity Investment Company Type | N-1A |
| Document Period End Date | Oct. 31, 2024 |
| Shareholder Report | 12 Months Ended |
| Oct. 31, 2024 USD ($) shares | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSR |
| Amendment Flag | false |
| Registrant Name | Fidelity Salem Street Trust |
| Entity Central Index Key | 0000035315 |
| Entity Investment Company Type | N-1A |
| Document Period End Date | Oct. 31, 2024 |
| Fidelity SAI Emerging Markets Low Volatility Index Fund | |
| Shareholder Report [Line Items] | |
| Fund Name | Fidelity® SAI Emerging Markets Low Volatility Index Fund |
| Class Name | Fidelity® SAI Emerging Markets Low Volatility Index Fund |
| Trading Symbol | FGKPX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains information about Fidelity® SAI Emerging Markets Low Volatility Index Fund for the period November 1, 2023 to October 31, 2024. |
| Shareholder Report Annual or Semi-Annual | annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the Fund at fundresearch.fidelity.com/prospectus/sec. You can also request this information by contacting us at 1-800-544-3455 or by sending an e-mail to fidfunddocuments@fidelity.com. |
| Additional Information Phone Number | 1-800-544-3455 |
| Additional Information Email | fidfunddocuments@fidelity.com |
| Additional Information Website | fundresearch.fidelity.com/prospectus/sec |
| Expenses [Text Block] | What were your Fund costs for the last year? (based on hypothetical $10,000 investment) FUND COST (PREVIOUS YEAR) Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Fidelity® SAI Emerging Markets Low Volatility Index Fund $ 0.26 % |
| Expenses Paid, Amount | $ 29 |
| Expense Ratio, Percent | 0.26% |
| Factors Affecting Performance [Text Block] | What affected the Fund's performance this period? • • • • • |
| Performance Past Does Not Indicate Future [Text] | The Fund's past performance is not a good predictor of the Fund's future performance.</span>" id="sjs-B25"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;">The Fund's past performance is not a good predictor of the Fund's future performance.</span> |
| Line Graph [Table Text Block] | How did the Fund perform over the life of Fund? CUMULATIVE PERFORMANCE January 30, 2019 through October 31, 2024. Initial investment of $10,000. Fidelity® SAI Emerging Markets Low Volatility Index Fund $10,000 $10,110 $9,595 $11,877 $9,872 $10,999 Fidelity Emerging Markets Low Volatility Focus Index℠ $10,000 $10,258 $9,827 $12,283 $10,249 $11,472 MSCI ACWI (All Country World Index) ex USA Index $10,000 $10,858 $10,590 $13,752 $10,368 $11,640 2019 2020 2021 2022 2023 2024 |
| Average Annual Return [Table Text Block] | AVERAGE ANNUAL TOTAL RETURNS: 1 Year 5 Year Life of Fund A Fidelity® SAI Emerging Markets Low Volatility Index Fund 18.98% 5.30% 4.78% Fidelity Emerging Markets Low Volatility Focus Index℠ 20.82% 6.21% 5.84% MSCI ACWI (All Country World Index) ex USA Index 24.55% 5.95% 6.66% A From January 30, 2019 Visit www.fidelity.com for more recent performance information. The Fund's past performance is not a good predictor of the Fund's future performance. The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares. |
| Performance Inception Date | Jan. 30, 2019 |
| No Deduction of Taxes [Text Block] | The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares. |
| Net Assets | $ 2,628,003,671 |
| Holdings Count | shares | 125 |
| Advisory Fees Paid, Amount | $ 5,304,513 |
| Investment Company Portfolio Turnover | 34% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics (as of October 31, 2024) KEY FACTS Fund Size $ Number of Holdings 125 Total Advisory Fee $ Portfolio Turnover 34 % |
| Holdings [Text Block] | MARKET SECTORS (% of Fund's net assets) Financials 27.6 Information Technology 20.1 Communication Services 13.6 Consumer Staples 9.4 Consumer Discretionary 7.8 Utilities 6.2 Health Care 5.3 Materials 4.2 Industrials 2.2 Energy 1.9 Real Estate 0.4 Common Stocks 98.7 Short-Term Investments and Net Other Assets (Liabilities) 1.3 ASSET ALLOCATION (% of Fund's net assets) Taiwan 25.0 India 21.5 China 15.0 Saudi Arabia 7.8 Korea (South) 7.6 Malaysia 4.9 United Arab Emirates 4.1 Qatar 2.6 Thailand 2.3 Others 9.2 GEOGRAPHIC DIVERSIFICATION (% of Fund's net assets) |
| Largest Holdings [Text Block] | TOP HOLDINGS (% of Fund's net assets) Asustek Computer Inc 1.8 Advanced Info Service PCL 1.7 Uni-President Enterprises Corp 1.7 China Construction Bank Corp H Shares 1.7 Saudi Telecom Co 1.7 Agricultural Bank of China Ltd H Shares 1.6 Bank of China Ltd H Shares 1.6 Industrial & Commercial Bank of China Ltd H Shares 1.6 Bharti Airtel Ltd 1.6 Bank of Communications Co Ltd H Shares 1.6 16.6 |
| Fidelity SAI Emerging Markets Value Index Fund | |
| Shareholder Report [Line Items] | |
| Fund Name | Fidelity® SAI Emerging Markets Value Index Fund |
| Class Name | Fidelity® SAI Emerging Markets Value Index Fund |
| Trading Symbol | FEMVX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains information about Fidelity® SAI Emerging Markets Value Index Fund for the period November 1, 2023 to October 31, 2024. |
| Shareholder Report Annual or Semi-Annual | annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the Fund at fundresearch.fidelity.com/prospectus/sec. You can also request this information by contacting us at 1-800-544-3455 or by sending an e-mail to fidfunddocuments@fidelity.com. |
| Additional Information Phone Number | 1-800-544-3455 |
| Additional Information Email | fidfunddocuments@fidelity.com |
| Additional Information Website | fundresearch.fidelity.com/prospectus/sec |
| Expenses [Text Block] | What were your Fund costs for the last year? (based on hypothetical $10,000 investment) FUND COST (PREVIOUS YEAR) Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Fidelity® SAI Emerging Markets Value Index Fund $ 0.21 % |
| Expenses Paid, Amount | $ 25 |
| Expense Ratio, Percent | 0.21% |
| Factors Affecting Performance [Text Block] | What affected the Fund's performance this period? • • • • |
| Performance Past Does Not Indicate Future [Text] | The Fund's past performance is not a good predictor of the Fund's future performance.</span>" id="sjs-B52"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;">The Fund's past performance is not a good predictor of the Fund's future performance.</span> |
| Line Graph [Table Text Block] | How did the Fund perform over the life of Fund? CUMULATIVE PERFORMANCE May 12, 2020 through October 31, 2024. Initial investment of $10,000. Fidelity® SAI Emerging Markets Value Index Fund $10,000 $11,780 $14,527 $10,868 $12,586 Fidelity Emerging Markets Value Focus Index℠ $10,000 $11,814 $14,782 $11,036 $12,841 MSCI Emerging Markets Index $10,000 $12,298 $14,386 $9,924 $11,000 2020 2021 2022 2023 2024 |
| Average Annual Return [Table Text Block] | AVERAGE ANNUAL TOTAL RETURNS: 1 Year Life of Fund A Fidelity® SAI Emerging Markets Value Index Fund 29.09% 11.46% Fidelity Emerging Markets Value Focus Index℠ 31.84% 12.49% MSCI Emerging Markets Index 25.33% 7.44% A From May 12, 2020 Visit www.fidelity.com for more recent performance information. The Fund's past performance is not a good predictor of the Fund's future performance. The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares. |
| Performance Inception Date | May 12, 2020 |
| No Deduction of Taxes [Text Block] | The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares. |
| Net Assets | $ 5,954,224,579 |
| Holdings Count | shares | 214 |
| Advisory Fees Paid, Amount | $ 6,639,914 |
| Investment Company Portfolio Turnover | 30% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics (as of October 31, 2024) KEY FACTS Fund Size $ Number of Holdings 214 Total Advisory Fee $ Portfolio Turnover 30 % |
| Holdings [Text Block] | MARKET SECTORS (% of Fund's net assets) Information Technology 24.2 Financials 24.2 Consumer Discretionary 13.0 Communication Services 8.8 Industrials 6.9 Materials 5.4 Consumer Staples 4.4 Energy 4.3 Health Care 3.1 Utilities 2.8 Real Estate 1.8 Common Stocks 98.9 Preferred Stocks 0.0 Short-Term Investments and Net Other Assets (Liabilities) 1.1 ASSET ALLOCATION (% of Fund's net assets) China 22.3 India 21.6 Taiwan 20.6 Korea (South) 10.5 Brazil 4.7 Saudi Arabia 3.1 South Africa 3.1 Malaysia 1.6 Indonesia 1.6 Others 10.9 GEOGRAPHIC DIVERSIFICATION (% of Fund's net assets) |
| Largest Holdings [Text Block] | TOP HOLDINGS (% of Fund's net assets) Taiwan Semiconductor Manufacturing Co Ltd 9.0 Tencent Holdings Ltd 3.2 Samsung Electronics Co Ltd 2.4 JD.com Inc A Shares 2.3 Hon Hai Precision Industry Co Ltd 2.2 China Construction Bank Corp H Shares 2.1 Industrial & Commercial Bank of China Ltd H Shares 1.6 Bank of China Ltd H Shares 1.6 Vale SA 1.5 Petroleo Brasileiro SA 1.5 27.4 |
| Fidelity Flex International Index Fund | |
| Shareholder Report [Line Items] | |
| Fund Name | Fidelity Flex® International Index Fund |
| Class Name | Fidelity Flex® International Index Fund |
| Trading Symbol | FITFX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains information about Fidelity Flex® International Index Fund for the period November 1, 2023 to October 31, 2024. |
| Shareholder Report Annual or Semi-Annual | annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the Fund at fundresearch.fidelity.com/prospectus/sec. You can also request this information by contacting us at 1-800-544-3455 or by sending an e-mail to fidfunddocuments@fidelity.com. |
| Material Fund Change Notice [Text Block] | This report describes changes to the Fund that occurred during the reporting period. |
| Additional Information Phone Number | 1-800-544-3455 |
| Additional Information Email | fidfunddocuments@fidelity.com |
| Additional Information Website | fundresearch.fidelity.com/prospectus/sec |
| Expenses [Text Block] | What were your Fund costs for the last year? (based on hypothetical $10,000 investment) FUND COST (PREVIOUS YEAR) Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Fidelity Flex® International Index Fund $ A 0.00 % B A Amount represents less than $.50 B Amount represents less than 0.005% |
| Expenses Paid, Amount | $ 0 |
| Expense Ratio, Percent | 0% |
| Factors Affecting Performance [Text Block] | What affected the Fund's performance this period? • • • • • |
| Performance Past Does Not Indicate Future [Text] | The Fund's past performance is not a good predictor of the Fund's future performance.</span>" id="sjs-B80"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;">The Fund's past performance is not a good predictor of the Fund's future performance.</span> |
| Line Graph [Table Text Block] | How did the Fund perform over the life of Fund? CUMULATIVE PERFORMANCE March 9, 2017 through October 31, 2024. Initial investment of $10,000. Fidelity Flex® International Index Fund $10,000 $11,790 $10,785 $12,014 $11,745 $15,188 $11,452 $12,909 MSCI ACWI (All Country World Index) ex USA Index $10,000 $11,809 $10,855 $12,101 $11,803 $15,326 $11,555 $12,973 2017 2018 2019 2020 2021 2022 2023 2024 |
| Average Annual Return [Table Text Block] | AVERAGE ANNUAL TOTAL RETURNS: 1 Year 5 Year Life of Fund A Fidelity Flex® International Index Fund 23.59% 5.84% 6.30% MSCI ACWI (All Country World Index) ex USA Index 24.55% 5.95% 6.47% A From March 9, 2017 Visit www.401k.com for more recent performance information. The Fund's past performance is not a good predictor of the Fund's future performance. The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares. |
| Performance Inception Date | Mar. 09, 2017 |
| No Deduction of Taxes [Text Block] | The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares. |
| Net Assets | $ 2,536,506,074 |
| Holdings Count | shares | 2,171 |
| Advisory Fees Paid, Amount | $ 0 |
| Investment Company Portfolio Turnover | 4% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics (as of October 31, 2024) KEY FACTS Fund Size $ Number of Holdings 2,171 Total Advisory Fee $ Portfolio Turnover 4 % |
| Holdings [Text Block] | MARKET SECTORS (% of Fund's net assets) Financials 23.8 Industrials 13.4 Information Technology 12.8 Consumer Discretionary 10.8 Health Care 9.0 Consumer Staples 6.8 Materials 6.6 Communication Services 5.0 Energy 4.9 Utilities 3.0 Real Estate 1.6 Common Stocks 97.3 Preferred Stocks 0.4 Short-Term Investments and Net Other Assets (Liabilities) 2.3 ASSET ALLOCATION (% of Fund's net assets) Japan 13.7 China 8.3 United States 8.0 Canada 7.5 United Kingdom 6.7 France 5.8 Germany 5.6 India 5.5 Taiwan 5.4 Others 33.5 GEOGRAPHIC DIVERSIFICATION (% of Fund's net assets) |
| Largest Holdings [Text Block] | TOP HOLDINGS (% of Fund's net assets) Taiwan Semiconductor Manufacturing Co Ltd 3.0 Novo Nordisk A/S Series B 1.4 Tencent Holdings Ltd 1.3 ASML Holding NV 1.1 Nestle SA 1.0 SAP SE 0.9 Astrazeneca PLC 0.9 Roche Holding AG 0.9 Novartis AG 0.8 Shell PLC 0.8 12.1 |
| Material Fund Change [Text Block] | How has the Fund changed? This is a summary of certain changes to the Fund since November 1, 2023. For more complete information, you may review the Fund's next prospectus, which we expect to be available by December 30, 2024 at fundresearch.fidelity.com/prospectus/sec or upon request at 1-800-544-3455 or by sending an e-mail to fidfunddocuments fidelity.com . The fund added a contractual proxy and shareholder meeting expense cap during the reporting period. |
| Material Fund Change Expenses [Text Block] | The fund added a contractual proxy and shareholder meeting expense cap during the reporting period. |
| Summary of Change Legend [Text Block] | This is a summary of certain changes to the Fund since November 1, 2023. For more complete information, you may review the Fund's next prospectus, which we expect to be available by December 30, 2024 at fundresearch.fidelity.com/prospectus/sec or upon request at 1-800-544-3455 or by sending an e-mail to fidfunddocuments fidelity.com . |
| Updated Prospectus Phone Number | 1-800-544-3455</span>" id="sjs-B95"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;">1-800-544-3455</span> |
| Updated Prospectus Email Address | fidfunddocuments@fidelity.com</span>" id="sjs-B96"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;">fidfunddocuments@fidelity.com</span> |
| Updated Prospectus Web Address | fundresearch.fidelity.com/prospectus/sec</span>" id="sjs-B97"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;">fundresearch.fidelity.com/prospectus/sec</span> |
| Fidelity International Sustainability Index Fund | |
| Shareholder Report [Line Items] | |
| Fund Name | Fidelity® International Sustainability Index Fund |
| Class Name | Fidelity® International Sustainability Index Fund |
| Trading Symbol | FNIDX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains information about Fidelity® International Sustainability Index Fund for the period November 1, 2023 to October 31, 2024. |
| Shareholder Report Annual or Semi-Annual | annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the Fund at fundresearch.fidelity.com/prospectus/sec. You can also request this information by contacting us at 1-800-544-8544 or by sending an e-mail to fidfunddocuments@fidelity.com. |
| Additional Information Phone Number | 1-800-544-8544 |
| Additional Information Email | fidfunddocuments@fidelity.com |
| Additional Information Website | fundresearch.fidelity.com/prospectus/sec |
| Expenses [Text Block] | What were your Fund costs for the last year? (based on hypothetical $10,000 investment) FUND COST (PREVIOUS YEAR) Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Fidelity® International Sustainability Index Fund $ 0.20 % |
| Expenses Paid, Amount | $ 22 |
| Expense Ratio, Percent | 0.20% |
| Factors Affecting Performance [Text Block] | What affected the Fund's performance this period? • • • • • • |
| Performance Past Does Not Indicate Future [Text] | The Fund's past performance is not a good predictor of the Fund's future performance.</span>" id="sjs-B113"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;">The Fund's past performance is not a good predictor of the Fund's future performance.</span> |
| Line Graph [Table Text Block] | How did the Fund perform over the life of Fund? CUMULATIVE PERFORMANCE May 9, 2017 through October 31, 2024. Initial investment of $10,000. Fidelity® International Sustainability Index Fund $10,000 $10,960 $9,999 $11,279 $11,447 $14,568 $10,473 $11,801 MSCI ACWI (All Country World Index) ex USA ESG Leaders Index $10,000 $11,000 $10,114 $11,464 $11,667 $14,934 $10,741 $12,069 MSCI ACWI (All Country World Index) ex USA Index $10,000 $11,047 $10,155 $11,320 $11,041 $14,338 $10,809 $12,136 2017 2018 2019 2020 2021 2022 2023 2024 |
| Average Annual Return [Table Text Block] | AVERAGE ANNUAL TOTAL RETURNS: 1 Year 5 Year Life of Fund A Fidelity® International Sustainability Index Fund 23.62% 5.28% 5.17% MSCI ACWI (All Country World Index) ex USA ESG Leaders Index 24.93% 5.63% 5.64% MSCI ACWI (All Country World Index) ex USA Index 24.55% 5.95% 5.67% A From May 9, 2017 Visit www.fidelity.com for more recent performance information. The Fund's past performance is not a good predictor of the Fund's future performance. The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares. |
| Performance Inception Date | May 09, 2017 |
| No Deduction of Taxes [Text Block] | The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares. |
| Net Assets | $ 441,951,608 |
| Holdings Count | shares | 911 |
| Advisory Fees Paid, Amount | $ 857,904 |
| Investment Company Portfolio Turnover | 14% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics (as of October 31, 2024) KEY FACTS Fund Size $ Number of Holdings 911 Total Advisory Fee $ Portfolio Turnover 14 % |
| Holdings [Text Block] | MARKET SECTORS (% of Fund's net assets) Financials 22.7 Industrials 13.5 Information Technology 12.8 Consumer Discretionary 11.1 Health Care 9.8 Communication Services 7.3 Consumer Staples 6.9 Materials 6.4 Energy 4.0 Utilities 2.7 Real Estate 1.7 Common Stocks 98.7 Preferred Stocks 0.2 Short-Term Investments and Net Other Assets (Liabilities) 1.1 ASSET ALLOCATION (% of Fund's net assets) Japan 15.0 China 9.3 United Kingdom 8.4 Taiwan 8.1 Canada 7.8 France 5.9 Switzerland 5.3 India 5.1 Denmark 3.7 Others 31.4 GEOGRAPHIC DIVERSIFICATION (% of Fund's net assets) |
| Largest Holdings [Text Block] | TOP HOLDINGS (% of Fund's net assets) Taiwan Semiconductor Manufacturing Co Ltd 5.6 Novo Nordisk A/S Series B 2.6 Tencent Holdings Ltd 2.4 ASML Holding NV 1.9 Astrazeneca PLC 1.7 Novartis AG 1.6 Alibaba Group Holding Ltd 1.4 LVMH Moet Hennessy Louis Vuitton SE 1.4 HSBC Holdings PLC 1.3 Unilever PLC 1.1 21.0 |
| Fidelity Global ex U.S. Index Fund | |
| Shareholder Report [Line Items] | |
| Fund Name | Fidelity® Global ex U.S. Index Fund |
| Class Name | Fidelity® Global ex U.S. Index Fund |
| Trading Symbol | FSGGX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains information about Fidelity® Global ex U.S. Index Fund for the period November 1, 2023 to October 31, 2024. |
| Shareholder Report Annual or Semi-Annual | annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the Fund at fundresearch.fidelity.com/prospectus/sec. You can also request this information by contacting us at 1-800-544-8544 or by sending an e-mail to fidfunddocuments@fidelity.com. |
| Additional Information Phone Number | 1-800-544-8544 |
| Additional Information Email | fidfunddocuments@fidelity.com |
| Additional Information Website | fundresearch.fidelity.com/prospectus/sec |
| Expenses [Text Block] | What were your Fund costs for the last year? (based on hypothetical $10,000 investment) FUND COST (PREVIOUS YEAR) Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Fidelity® Global ex U.S. Index Fund $ 0.05 % |
| Expenses Paid, Amount | $ 6 |
| Expense Ratio, Percent | 0.05% |
| Factors Affecting Performance [Text Block] | What affected the Fund's performance this period? • • • • • |
| Performance Past Does Not Indicate Future [Text] | The Fund's past performance is not a good predictor of the Fund's future performance.</span>" id="sjs-B140"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;">The Fund's past performance is not a good predictor of the Fund's future performance.</span> |
| Line Graph [Table Text Block] | How did the Fund perform over the past 10 years? CUMULATIVE PERFORMANCE October 31, 2014 through October 31, 2024. Initial investment of $10,000. Fidelity® Global ex U.S. Index Fund $10,000 $9,455 $9,520 $11,788 $10,789 $12,007 $11,737 $15,170 $11,444 $12,903 $15,944 MSCI ACWI (All Country World Index) ex USA Index $10,000 $9,545 $9,583 $11,868 $10,910 $12,161 $11,862 $15,403 $11,613 $13,038 $16,238 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 |
| Average Annual Return [Table Text Block] | AVERAGE ANNUAL TOTAL RETURNS: 1 Year 5 Year 10 Year Fidelity® Global ex U.S. Index Fund 23.57% 5.84% 4.78% MSCI ACWI (All Country World Index) ex USA Index 24.55% 5.95% 4.97% Visit www.fidelity.com for more recent performance information. The Fund's past performance is not a good predictor of the Fund's future performance. The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares. |
| No Deduction of Taxes [Text Block] | The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares. |
| Net Assets | $ 10,844,499,225 |
| Holdings Count | shares | 2,192 |
| Advisory Fees Paid, Amount | $ 5,523,301 |
| Investment Company Portfolio Turnover | 3% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics (as of October 31, 2024) KEY FACTS Fund Size $ Number of Holdings 2,192 Total Advisory Fee $ Portfolio Turnover 3 % |
| Holdings [Text Block] | MARKET SECTORS (% of Fund's net assets) Financials 23.7 Industrials 13.4 Information Technology 12.8 Consumer Discretionary 10.7 Health Care 8.9 Consumer Staples 6.8 Materials 6.6 Communication Services 4.9 Energy 4.7 Utilities 3.0 Real Estate 1.7 Common Stocks 96.8 Preferred Stocks 0.4 Bonds 0.0 Short-Term Investments and Net Other Assets (Liabilities) 2.8 ASSET ALLOCATION (% of Fund's net assets) Japan 13.6 United States 8.4 China 8.2 Canada 7.4 United Kingdom 6.7 France 5.7 Germany 5.6 India 5.4 Taiwan 5.4 Others 33.6 GEOGRAPHIC DIVERSIFICATION (% of Fund's net assets) |
| Largest Holdings [Text Block] | TOP HOLDINGS (% of Fund's net assets) Taiwan Semiconductor Manufacturing Co Ltd 2.9 Novo Nordisk A/S Series B 1.4 Tencent Holdings Ltd 1.3 ASML Holding NV 1.1 Nestle SA 1.0 SAP SE 0.9 Roche Holding AG 0.9 Astrazeneca PLC 0.8 Novartis AG 0.8 Shell PLC 0.8 11.9 |
| Fidelity Total International Index Fund | |
| Shareholder Report [Line Items] | |
| Fund Name | Fidelity® Total International Index Fund |
| Class Name | Fidelity® Total International Index Fund |
| Trading Symbol | FTIHX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains information about Fidelity® Total International Index Fund for the period November 1, 2023 to October 31, 2024. |
| Shareholder Report Annual or Semi-Annual | annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the Fund at fundresearch.fidelity.com/prospectus/sec. You can also request this information by contacting us at 1-800-544-8544 or by sending an e-mail to fidfunddocuments@fidelity.com. |
| Additional Information Phone Number | 1-800-544-8544 |
| Additional Information Email | fidfunddocuments@fidelity.com |
| Additional Information Website | fundresearch.fidelity.com/prospectus/sec |
| Expenses [Text Block] | What were your Fund costs for the last year? (based on hypothetical $10,000 investment) FUND COST (PREVIOUS YEAR) Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Fidelity® Total International Index Fund $ 0.06 % |
| Expenses Paid, Amount | $ 7 |
| Expense Ratio, Percent | 0.06% |
| Factors Affecting Performance [Text Block] | What affected the Fund's performance this period? • • • • • |
| Performance Past Does Not Indicate Future [Text] | The Fund's past performance is not a good predictor of the Fund's future performance.</span>" id="sjs-B166"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;">The Fund's past performance is not a good predictor of the Fund's future performance.</span> |
| Line Graph [Table Text Block] | How did the Fund perform over the life of Fund? CUMULATIVE PERFORMANCE June 7, 2016 through October 31, 2024. Initial investment of $10,000. Fidelity® Total International Index Fund $10,000 $10,090 $12,448 $11,401 $12,641 $12,392 $16,167 $12,124 $13,614 MSCI ACWI (All Country World Index) ex USA Investable Market Index $10,000 $10,131 $12,561 $11,520 $12,802 $12,530 $16,426 $12,311 $13,764 2016 2017 2018 2019 2020 2021 2022 2023 2024 |
| Average Annual Return [Table Text Block] | AVERAGE ANNUAL TOTAL RETURNS: 1 Year 5 Year Life of Fund A Fidelity® Total International Index Fund 23.34% 5.84% 6.36% MSCI ACWI (All Country World Index) ex USA Investable Market Index 24.46% 6.00% 6.61% A From June 7, 2016 Visit www.fidelity.com for more recent performance information. The Fund's past performance is not a good predictor of the Fund's future performance. The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares. |
| Performance Inception Date | Jun. 07, 2016 |
| No Deduction of Taxes [Text Block] | The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares. |
| Net Assets | $ 13,433,009,806 |
| Holdings Count | shares | 5,088 |
| Advisory Fees Paid, Amount | $ 7,421,867 |
| Investment Company Portfolio Turnover | 5% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics (as of October 31, 2024) KEY FACTS Fund Size $ Number of Holdings 5,088 Total Advisory Fee $ Portfolio Turnover 5 % |
| Holdings [Text Block] | MARKET SECTORS (% of Fund's net assets) Financials 22.2 Industrials 14.3 Information Technology 12.4 Consumer Discretionary 11.1 Health Care 8.9 Materials 7.2 Consumer Staples 7.0 Communication Services 4.9 Energy 4.4 Utilities 3.0 Real Estate 2.5 Common Stocks 97.6 Preferred Stocks 0.3 Short-Term Investments and Net Other Assets (Liabilities) 2.1 ASSET ALLOCATION (% of Fund's net assets) Japan 14.9 China 7.6 Canada 7.5 United Kingdom 7.1 United States 7.1 India 6.0 Taiwan 5.6 France 5.2 Germany 5.1 Others 33.9 GEOGRAPHIC DIVERSIFICATION (% of Fund's net assets) |
| Largest Holdings [Text Block] | TOP HOLDINGS (% of Fund's net assets) Taiwan Semiconductor Manufacturing Co Ltd 2.6 Novo Nordisk A/S Series B 1.2 Tencent Holdings Ltd 1.2 ASML Holding NV 0.9 SAP SE 0.9 Nestle SA 0.8 Astrazeneca PLC 0.7 Novartis AG 0.7 Roche Holding AG 0.7 Shell PLC 0.7 10.4 |
| Fidelity Emerging Markets Index Fund | |
| Shareholder Report [Line Items] | |
| Fund Name | Fidelity® Emerging Markets Index Fund |
| Class Name | Fidelity® Emerging Markets Index Fund |
| Trading Symbol | FPADX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains information about Fidelity® Emerging Markets Index Fund for the period November 1, 2023 to October 31, 2024. |
| Shareholder Report Annual or Semi-Annual | annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the Fund at fundresearch.fidelity.com/prospectus/sec. You can also request this information by contacting us at 1-800-544-8544 or by sending an e-mail to fidfunddocuments@fidelity.com. |
| Additional Information Phone Number | 1-800-544-8544 |
| Additional Information Email | fidfunddocuments@fidelity.com |
| Additional Information Website | fundresearch.fidelity.com/prospectus/sec |
| Expenses [Text Block] | What were your Fund costs for the last year? (based on hypothetical $10,000 investment) FUND COST (PREVIOUS YEAR) Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Fidelity® Emerging Markets Index Fund $ 0.07 % |
| Expenses Paid, Amount | $ 8 |
| Expense Ratio, Percent | 0.07% |
| Factors Affecting Performance [Text Block] | What affected the Fund's performance this period? • • • • • • |
| Performance Past Does Not Indicate Future [Text] | The Fund's past performance is not a good predictor of the Fund's future performance.</span>" id="sjs-B193"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;">The Fund's past performance is not a good predictor of the Fund's future performance.</span> |
| Line Graph [Table Text Block] | How did the Fund perform over the past 10 years? CUMULATIVE PERFORMANCE October 31, 2014 through October 31, 2024. Initial investment of $10,000. Fidelity® Emerging Markets Index Fund $10,000 $8,454 $9,297 $11,741 $10,256 $11,418 $12,393 $14,369 $9,943 $11,011 $13,612 Fidelity Emerging Markets Index Fund Linked Index℠ $10,000 $8,507 $9,373 $11,858 $10,377 $11,611 $12,571 $14,706 $10,145 $11,244 $14,092 MSCI Emerging Markets Index $10,000 $8,550 $9,346 $11,823 $10,347 $11,577 $12,535 $14,663 $10,115 $11,211 $14,051 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 |
| Average Annual Return [Table Text Block] | AVERAGE ANNUAL TOTAL RETURNS: 1 Year 5 Year 10 Year Fidelity® Emerging Markets Index Fund 23.63% 3.58% 3.13% Fidelity Emerging Markets Index Fund Linked Index℠ 25.33% 3.95% 3.49% MSCI Emerging Markets Index 25.33% 3.95% 3.46% Visit www.fidelity.com for more recent performance information. The Fund's past performance is not a good predictor of the Fund's future performance. The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares. |
| No Deduction of Taxes [Text Block] | The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares. |
| Net Assets | $ 8,218,898,629 |
| Holdings Count | shares | 1,338 |
| Advisory Fees Paid, Amount | $ 5,570,358 |
| Investment Company Portfolio Turnover | 5% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics (as of October 31, 2024) KEY FACTS Fund Size $ Number of Holdings 1,338 Total Advisory Fee $ Portfolio Turnover 5 % |
| Holdings [Text Block] | MARKET SECTORS (% of Fund's net assets) Financials 23.2 Information Technology 22.8 Consumer Discretionary 13.1 Communication Services 8.6 Industrials 6.4 Materials 6.2 Consumer Staples 4.7 Energy 4.5 Health Care 3.4 Utilities 2.7 Real Estate 1.3 Common Stocks 96.4 Preferred Stocks 0.5 Bonds 0.0 Short-Term Investments and Net Other Assets (Liabilities) 3.1 ASSET ALLOCATION (% of Fund's net assets) China 26.7 India 18.3 Taiwan 18.1 Korea (South) 9.8 Brazil 4.6 Saudi Arabia 3.8 United States 3.2 South Africa 2.9 Mexico 1.9 Others 10.7 GEOGRAPHIC DIVERSIFICATION (% of Fund's net assets) |
| Largest Holdings [Text Block] | TOP HOLDINGS (% of Fund's net assets) Taiwan Semiconductor Manufacturing Co Ltd 9.6 Tencent Holdings Ltd 4.3 Samsung Electronics Co Ltd 2.5 Alibaba Group Holding Ltd 2.4 Meituan B Shares 1.5 HDFC Bank Ltd 1.2 Hon Hai Precision Industry Co Ltd 1.1 ICICI Bank Ltd 1.1 PDD Holdings Inc Class A ADR 1.0 China Construction Bank Corp H Shares 1.0 25.7 |
| Fidelity U.S. Sustainability Index Fund | |
| Shareholder Report [Line Items] | |
| Fund Name | Fidelity® U.S. Sustainability Index Fund |
| Class Name | Fidelity® U.S. Sustainability Index Fund |
| Trading Symbol | FITLX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains information about Fidelity® U.S. Sustainability Index Fund for the period November 1, 2023 to October 31, 2024. |
| Shareholder Report Annual or Semi-Annual | annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the Fund at fundresearch.fidelity.com/prospectus/sec. You can also request this information by contacting us at 1-800-544-8544 or by sending an e-mail to fidfunddocuments@fidelity.com. |
| Additional Information Phone Number | 1-800-544-8544 |
| Additional Information Email | fidfunddocuments@fidelity.com |
| Additional Information Website | fundresearch.fidelity.com/prospectus/sec |
| Expenses [Text Block] | What were your Fund costs for the last year? (based on hypothetical $10,000 investment) FUND COST (PREVIOUS YEAR) Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Fidelity® U.S. Sustainability Index Fund $ 0.11 % |
| Expenses Paid, Amount | $ 13 |
| Expense Ratio, Percent | 0.11% |
| Factors Affecting Performance [Text Block] | What affected the Fund's performance this period? • • • • |
| Performance Past Does Not Indicate Future [Text] | The Fund's past performance is not a good predictor of the Fund's future performance.</span>" id="sjs-B219"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;">The Fund's past performance is not a good predictor of the Fund's future performance.</span> |
| Line Graph [Table Text Block] | How did the Fund perform over the life of Fund? CUMULATIVE PERFORMANCE May 9, 2017 through October 31, 2024. Initial investment of $10,000. Fidelity® U.S. Sustainability Index Fund $10,000 $10,900 $11,518 $13,483 $14,829 $21,923 $17,848 $20,075 MSCI USA ESG Leaders Index $10,000 $10,904 $11,542 $13,531 $14,897 $22,049 $17,970 $20,235 MSCI USA Index $10,000 $10,813 $11,530 $13,106 $14,543 $20,758 $17,257 $18,905 2017 2018 2019 2020 2021 2022 2023 2024 |
| Average Annual Return [Table Text Block] | AVERAGE ANNUAL TOTAL RETURNS: 1 Year 5 Year Life of Fund A Fidelity® U.S. Sustainability Index Fund 38.21% 15.53% 14.61% MSCI USA ESG Leaders Index 38.49% 15.67% 14.76% MSCI USA Index 37.82% 14.73% 13.65% A From May 9, 2017 Visit www.fidelity.com for more recent performance information. The Fund's past performance is not a good predictor of the Fund's future performance. The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares. |
| Performance Inception Date | May 09, 2017 |
| No Deduction of Taxes [Text Block] | The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares. |
| Net Assets | $ 4,195,026,130 |
| Holdings Count | shares | 292 |
| Advisory Fees Paid, Amount | $ 4,033,182 |
| Investment Company Portfolio Turnover | 9% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics (as of October 31, 2024) KEY FACTS Fund Size $ Number of Holdings 292 Total Advisory Fee $ Portfolio Turnover 9 % |
| Holdings [Text Block] | MARKET SECTORS (% of Fund's net assets) Information Technology 31.4 Financials 11.3 Health Care 9.8 Consumer Discretionary 9.0 Communication Services 8.7 Industrials 7.8 Consumer Staples 4.6 Materials 2.4 Real Estate 2.1 Energy 1.5 Utilities 0.9 Common Stocks 89.5 Short-Term Investments and Net Other Assets (Liabilities) 10.5 ASSET ALLOCATION (% of Fund's net assets) United States 99.5 Brazil 0.3 China 0.2 GEOGRAPHIC DIVERSIFICATION (% of Fund's net assets) |
| Largest Holdings [Text Block] | TOP HOLDINGS (% of Fund's net assets) NVIDIA Corp 11.2 Microsoft Corp 9.9 Alphabet Inc Class A 3.5 Alphabet Inc Class C 3.0 Tesla Inc 2.6 Eli Lilly & Co 2.5 Visa Inc Class A 1.6 Mastercard Inc Class A 1.4 Home Depot Inc/The 1.3 Procter & Gamble Co/The 1.3 38.3 |
| Fidelity SAI International Quality Index Fund | |
| Shareholder Report [Line Items] | |
| Fund Name | Fidelity® SAI International Quality Index Fund |
| Class Name | Fidelity® SAI International Quality Index Fund |
| Trading Symbol | FQITX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains information about Fidelity® SAI International Quality Index Fund for the period November 1, 2023 to October 31, 2024. |
| Shareholder Report Annual or Semi-Annual | annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the Fund at fundresearch.fidelity.com/prospectus/sec. You can also request this information by contacting us at 1-800-544-3455 or by sending an e-mail to fidfunddocuments@fidelity.com. |
| Material Fund Change Notice [Text Block] | This report describes changes to the Fund that occurred during the reporting period. |
| Additional Information Phone Number | 1-800-544-3455 |
| Additional Information Email | fidfunddocuments@fidelity.com |
| Additional Information Website | fundresearch.fidelity.com/prospectus/sec |
| Expenses [Text Block] | What were your Fund costs for the last year? (based on hypothetical $10,000 investment) FUND COST (PREVIOUS YEAR) Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Fidelity® SAI International Quality Index Fund $ 0.18 % |
| Expenses Paid, Amount | $ 20 |
| Expense Ratio, Percent | 0.18% |
| Factors Affecting Performance [Text Block] | What affected the Fund's performance this period? • • • • • • |
| Performance Past Does Not Indicate Future [Text] | The Fund's past performance is not a good predictor of the Fund's future performance.</span>" id="sjs-B247"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;">The Fund's past performance is not a good predictor of the Fund's future performance.</span> |
| Line Graph [Table Text Block] | How did the Fund perform over the life of Fund? CUMULATIVE PERFORMANCE May 12, 2020 through October 31, 2024. Initial investment of $10,000. Fidelity® SAI International Quality Index Fund $10,000 $11,070 $14,644 $11,138 $12,600 Fidelity International Quality Focus Index℠ $10,000 $11,074 $14,711 $11,236 $12,665 MSCI ACWI (All Country World Index) ex USA Index $10,000 $11,310 $14,687 $11,073 $12,432 2020 2021 2022 2023 2024 |
| Average Annual Return [Table Text Block] | AVERAGE ANNUAL TOTAL RETURNS: 1 Year Life of Fund A Fidelity® SAI International Quality Index Fund 21.81% 10.05% Fidelity International Quality Focus Index℠ 22.97% 10.41% MSCI ACWI (All Country World Index) ex USA Index 24.55% 10.26% A From May 12, 2020 Visit www.fidelity.com for more recent performance information. The Fund's past performance is not a good predictor of the Fund's future performance. The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares. |
| Performance Inception Date | May 12, 2020 |
| No Deduction of Taxes [Text Block] | The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares. |
| Net Assets | $ 1,580,584,126 |
| Holdings Count | shares | 134 |
| Advisory Fees Paid, Amount | $ 1,431,195 |
| Investment Company Portfolio Turnover | 39% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics (as of October 31, 2024) KEY FACTS Fund Size $ Number of Holdings 134 Total Advisory Fee $ Portfolio Turnover 39 % |
| Holdings [Text Block] | MARKET SECTORS (% of Fund's net assets) Health Care 17.5 Industrials 16.3 Consumer Discretionary 14.6 Financials 14.1 Information Technology 13.0 Consumer Staples 11.5 Materials 6.0 Communication Services 4.0 Utilities 0.6 Energy 0.4 Real Estate 0.2 Common Stocks 98.2 Short-Term Investments and Net Other Assets (Liabilities) 1.8 ASSET ALLOCATION (% of Fund's net assets) Japan 18.8 Switzerland 15.9 United States 10.8 United Kingdom 10.3 France 8.3 Netherlands 7.1 Germany 6.4 Denmark 5.7 Australia 5.7 Others 11.0 GEOGRAPHIC DIVERSIFICATION (% of Fund's net assets) |
| Largest Holdings [Text Block] | TOP HOLDINGS (% of Fund's net assets) Novo Nordisk A/S Series B 3.7 SAP SE 3.5 ASML Holding NV 3.2 Roche Holding AG 3.2 Novartis AG 3.1 LVMH Moet Hennessy Louis Vuitton SE 3.0 Unilever PLC 2.7 BHP Group Ltd 2.7 Recruit Holdings Co Ltd 2.7 ABB Ltd 2.5 30.3 |
| Material Fund Change [Text Block] | How has the Fund changed? This is a summary of certain changes to the Fund since November 1, 2023. For more complete information, you may review the Fund's next prospectus, which we expect to be available by December 30, 2024 at fundresearch.fidelity.com/prospectus/sec or upon request at 1-800-544-3455 or by sending an e-mail to fidfunddocuments fidelity.com . The fees associated with this class changed during the reporting year. The variations in class fees are primarily the result of the following changes: Operating expenses |
| Material Fund Change Expenses [Text Block] | The fees associated with this class changed during the reporting year. The variations in class fees are primarily the result of the following changes: Operating expenses |
| Summary of Change Legend [Text Block] | This is a summary of certain changes to the Fund since November 1, 2023. For more complete information, you may review the Fund's next prospectus, which we expect to be available by December 30, 2024 at fundresearch.fidelity.com/prospectus/sec or upon request at 1-800-544-3455 or by sending an e-mail to fidfunddocuments fidelity.com . |
| Updated Prospectus Phone Number | 1-800-544-3455</span>" id="sjs-B262"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;">1-800-544-3455</span> |
| Updated Prospectus Email Address | fidfunddocuments@fidelity.com</span>" id="sjs-B263"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;">fidfunddocuments@fidelity.com</span> |
| Updated Prospectus Web Address | fundresearch.fidelity.com/prospectus/sec</span>" id="sjs-B264"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;">fundresearch.fidelity.com/prospectus/sec</span> |
| Fidelity SAI Emerging Markets Index Fund | |
| Shareholder Report [Line Items] | |
| Fund Name | Fidelity® SAI Emerging Markets Index Fund |
| Class Name | Fidelity® SAI Emerging Markets Index Fund |
| Trading Symbol | FERGX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains information about Fidelity® SAI Emerging Markets Index Fund for the period November 1, 2023 to October 31, 2024. |
| Shareholder Report Annual or Semi-Annual | annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the Fund at fundresearch.fidelity.com/prospectus/sec. You can also request this information by contacting us at 1-800-544-3455 or by sending an e-mail to fidfunddocuments@fidelity.com. |
| Additional Information Phone Number | 1-800-544-3455 |
| Additional Information Email | fidfunddocuments@fidelity.com |
| Additional Information Website | fundresearch.fidelity.com/prospectus/sec |
| Expenses [Text Block] | What were your Fund costs for the last year? (based on hypothetical $10,000 investment) FUND COST (PREVIOUS YEAR) Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Fidelity® SAI Emerging Markets Index Fund $ 0.08 % |
| Expenses Paid, Amount | $ 9 |
| Expense Ratio, Percent | 0.08% |
| Factors Affecting Performance [Text Block] | What affected the Fund's performance this period? • • • • • |
| Performance Past Does Not Indicate Future [Text] | The Fund's past performance is not a good predictor of the Fund's future performance.</span>" id="sjs-B280"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;">The Fund's past performance is not a good predictor of the Fund's future performance.</span> |
| Line Graph [Table Text Block] | How did the Fund perform over the life of Fund? CUMULATIVE PERFORMANCE January 5, 2016 through October 31, 2024. Initial investment of $10,000. Fidelity® SAI Emerging Markets Index Fund $10,000 $11,940 $15,074 $13,173 $14,680 $15,882 $18,403 $12,718 $14,063 MSCI Emerging Markets Index $10,000 $12,019 $15,204 $13,306 $14,888 $16,119 $18,856 $13,008 $14,418 2016 2017 2018 2019 2020 2021 2022 2023 2024 |
| Average Annual Return [Table Text Block] | AVERAGE ANNUAL TOTAL RETURNS: 1 Year 5 Year Life of Fund A Fidelity® SAI Emerging Markets Index Fund 23.48% 3.42% 6.45% MSCI Emerging Markets Index 25.33% 3.95% 6.93% A From January 5, 2016 Visit www.fidelity.com for more recent performance information. The Fund's past performance is not a good predictor of the Fund's future performance. The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares. |
| Performance Inception Date | Jan. 05, 2016 |
| No Deduction of Taxes [Text Block] | The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares. |
| Net Assets | $ 5,123,676,032 |
| Holdings Count | shares | 1,318 |
| Advisory Fees Paid, Amount | $ 3,903,648 |
| Investment Company Portfolio Turnover | 29% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics (as of October 31, 2024) KEY FACTS Fund Size $ Number of Holdings 1,318 Total Advisory Fee $ Portfolio Turnover 29 % |
| Holdings [Text Block] | MARKET SECTORS (% of Fund's net assets) Financials 23.3 Information Technology 23.2 Consumer Discretionary 13.3 Communication Services 8.7 Industrials 6.5 Materials 6.4 Consumer Staples 4.9 Energy 4.5 Health Care 3.5 Utilities 2.7 Real Estate 1.5 Common Stocks 98.0 Preferred Stocks 0.5 Short-Term Investments and Net Other Assets (Liabilities) 1.5 ASSET ALLOCATION (% of Fund's net assets) China 27.1 India 18.6 Taiwan 18.4 Korea (South) 9.9 Brazil 4.7 Saudi Arabia 3.9 South Africa 2.9 Mexico 2.0 Indonesia 1.6 Others 10.9 GEOGRAPHIC DIVERSIFICATION (% of Fund's net assets) |
| Largest Holdings [Text Block] | TOP HOLDINGS (% of Fund's net assets) Taiwan Semiconductor Manufacturing Co Ltd 9.8 Tencent Holdings Ltd 4.3 Samsung Electronics Co Ltd 2.6 Alibaba Group Holding Ltd 2.4 Meituan B Shares 1.6 HDFC Bank Ltd 1.2 PDD Holdings Inc Class A ADR 1.1 Hon Hai Precision Industry Co Ltd 1.1 ICICI Bank Ltd 1.1 China Construction Bank Corp H Shares 1.0 26.2 |
| Fidelity SAI International Momentum Index Fund | |
| Shareholder Report [Line Items] | |
| Fund Name | Fidelity® SAI International Momentum Index Fund |
| Class Name | Fidelity® SAI International Momentum Index Fund |
| Trading Symbol | FITMX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains information about Fidelity® SAI International Momentum Index Fund for the period November 1, 2023 to October 31, 2024. |
| Shareholder Report Annual or Semi-Annual | annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the Fund at fundresearch.fidelity.com/prospectus/sec. You can also request this information by contacting us at 1-800-544-3455 or by sending an e-mail to fidfunddocuments@fidelity.com. |
| Additional Information Phone Number | 1-800-544-3455 |
| Additional Information Email | fidfunddocuments@fidelity.com |
| Additional Information Website | fundresearch.fidelity.com/prospectus/sec |
| Expenses [Text Block] | What were your Fund costs for the last year? (based on hypothetical $10,000 investment) FUND COST (PREVIOUS YEAR) Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Fidelity® SAI International Momentum Index Fund $ 0.18 % |
| Expenses Paid, Amount | $ 20 |
| Expense Ratio, Percent | 0.18% |
| Factors Affecting Performance [Text Block] | What affected the Fund's performance this period? • • • • • • |
| Performance Past Does Not Indicate Future [Text] | The Fund's past performance is not a good predictor of the Fund's future performance.</span>" id="sjs-B307"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;">The Fund's past performance is not a good predictor of the Fund's future performance.</span> |
| Line Graph [Table Text Block] | How did the Fund perform over the life of Fund? CUMULATIVE PERFORMANCE May 12, 2020 through October 31, 2024. Initial investment of $10,000. Fidelity® SAI International Momentum Index Fund $10,000 $11,330 $14,679 $10,665 $12,428 Fidelity International Momentum Focus Index℠ $10,000 $11,342 $14,753 $10,780 $12,499 MSCI ACWI (All Country World Index) ex USA Index $10,000 $11,310 $14,687 $11,073 $12,432 2020 2021 2022 2023 2024 |
| Average Annual Return [Table Text Block] | AVERAGE ANNUAL TOTAL RETURNS: 1 Year Life of Fund A Fidelity® SAI International Momentum Index Fund 27.42% 10.82% Fidelity International Momentum Focus Index℠ 28.90% 11.25% MSCI ACWI (All Country World Index) ex USA Index 24.55% 10.26% A From May 12, 2020 Visit www.fidelity.com for more recent performance information. The Fund's past performance is not a good predictor of the Fund's future performance. The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares. |
| Performance Inception Date | May 12, 2020 |
| No Deduction of Taxes [Text Block] | The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares. |
| Net Assets | $ 813,112,674 |
| Holdings Count | shares | 203 |
| Advisory Fees Paid, Amount | $ 1,133,898 |
| Investment Company Portfolio Turnover | 62% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics (as of October 31, 2024) KEY FACTS Fund Size $ Number of Holdings 203 Total Advisory Fee $ Portfolio Turnover 62 % |
| Holdings [Text Block] | MARKET SECTORS (% of Fund's net assets) Financials 23.0 Industrials 20.5 Health Care 13.4 Consumer Discretionary 9.7 Consumer Staples 7.8 Information Technology 7.5 Materials 5.5 Communication Services 3.9 Utilities 3.1 Energy 3.1 Real Estate 1.4 Common Stocks 98.9 Short-Term Investments and Net Other Assets (Liabilities) 1.1 ASSET ALLOCATION (% of Fund's net assets) Japan 26.5 United Kingdom 13.1 France 10.0 Germany 7.7 United States 7.1 Switzerland 5.4 Denmark 5.1 Australia 4.9 Spain 4.7 Others 15.5 GEOGRAPHIC DIVERSIFICATION (% of Fund's net assets) |
| Largest Holdings [Text Block] | TOP HOLDINGS (% of Fund's net assets) Novo Nordisk A/S Series B 3.6 ABB Ltd 2.4 HSBC Holdings PLC 2.3 Hitachi Ltd 2.2 Safran SA 2.2 UniCredit SpA 2.0 Tokio Marine Holdings Inc 2.0 Shell PLC 2.0 Muenchener Rueckversicherungs-Gesellschaft AG in Muenchen 1.9 L'Oreal SA 1.8 22.4 |
| Fidelity SAI International Value Index Fund | |
| Shareholder Report [Line Items] | |
| Fund Name | Fidelity® SAI International Value Index Fund |
| Class Name | Fidelity® SAI International Value Index Fund |
| Trading Symbol | FIWCX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains information about Fidelity® SAI International Value Index Fund for the period November 1, 2023 to October 31, 2024. |
| Shareholder Report Annual or Semi-Annual | annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the Fund at fundresearch.fidelity.com/prospectus/sec. You can also request this information by contacting us at 1-800-544-3455 or by sending an e-mail to fidfunddocuments@fidelity.com. |
| Material Fund Change Notice [Text Block] | This report describes changes to the Fund that occurred during the reporting period. |
| Additional Information Phone Number | 1-800-544-3455 |
| Additional Information Email | fidfunddocuments@fidelity.com |
| Additional Information Website | fundresearch.fidelity.com/prospectus/sec |
| Expenses [Text Block] | What were your Fund costs for the last year? (based on hypothetical $10,000 investment) FUND COST (PREVIOUS YEAR) Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Fidelity® SAI International Value Index Fund $ 0.16 % |
| Expenses Paid, Amount | $ 18 |
| Expense Ratio, Percent | 0.16% |
| Factors Affecting Performance [Text Block] | What affected the Fund's performance this period? • • • • • • |
| Performance Past Does Not Indicate Future [Text] | The Fund's past performance is not a good predictor of the Fund's future performance.</span>" id="sjs-B335"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;">The Fund's past performance is not a good predictor of the Fund's future performance.</span> |
| Line Graph [Table Text Block] | How did the Fund perform over the life of Fund? CUMULATIVE PERFORMANCE December 19, 2017 through October 31, 2024. Initial investment of $10,000. Fidelity® SAI International Value Index Fund $10,000 $8,936 $9,394 $7,575 $10,781 $8,956 $10,770 $12,961 Fidelity International Value Focus Index℠ $10,000 $9,030 $9,524 $7,670 $10,972 $9,158 $10,962 $13,288 MSCI ACWI (All Country World Index) ex USA Index $10,000 $9,061 $10,101 $9,852 $12,794 $9,645 $10,829 $13,487 2017 2018 2019 2020 2021 2022 2023 2024 |
| Average Annual Return [Table Text Block] | AVERAGE ANNUAL TOTAL RETURNS: 1 Year 5 Year Life of Fund A Fidelity® SAI International Value Index Fund 20.34% 6.65% 3.85% Fidelity International Value Focus Index℠ 21.22% 6.89% 4.22% MSCI ACWI (All Country World Index) ex USA Index 24.55% 5.95% 4.45% A From December 19, 2017 Visit www.fidelity.com for more recent performance information. The Fund's past performance is not a good predictor of the Fund's future performance. The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares. |
| Performance Inception Date | Dec. 19, 2017 |
| No Deduction of Taxes [Text Block] | The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares. |
| Net Assets | $ 6,277,390,831 |
| Holdings Count | shares | 204 |
| Advisory Fees Paid, Amount | $ 7,853,225 |
| Investment Company Portfolio Turnover | 59% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics (as of October 31, 2024) KEY FACTS Fund Size $ Number of Holdings 204 Total Advisory Fee $ Portfolio Turnover 59 % |
| Holdings [Text Block] | MARKET SECTORS (% of Fund's net assets) Financials 23.6 Industrials 16.4 Consumer Discretionary 10.9 Health Care 10.2 Materials 8.4 Consumer Staples 6.3 Communication Services 6.3 Information Technology 6.2 Energy 5.5 Utilities 4.0 Real Estate 1.1 Common Stocks 98.9 Short-Term Investments and Net Other Assets (Liabilities) 1.1 ASSET ALLOCATION (% of Fund's net assets) Japan 26.3 Germany 13.3 United Kingdom 11.3 France 11.2 United States 10.2 Singapore 4.6 Italy 3.9 Australia 3.9 Spain 3.4 Others 11.9 GEOGRAPHIC DIVERSIFICATION (% of Fund's net assets) |
| Largest Holdings [Text Block] | TOP HOLDINGS (% of Fund's net assets) Deutsche Telekom AG 2.8 UBS Group AG 2.7 Sanofi SA 2.6 Banco Santander SA 2.2 GSK PLC 2.1 BP PLC 2.1 UniCredit SpA 1.9 British American Tobacco PLC 1.9 Rio Tinto PLC 1.9 BNP Paribas SA 1.9 22.1 |
| Material Fund Change [Text Block] | How has the Fund changed? This is a summary of certain changes to the Fund since November 1, 2023. For more complete information, you may review the Fund's next prospectus, which we expect to be available by December 30, 2024 at fundresearch.fidelity.com/prospectus/sec or upon request at 1-800-544-3455 or by sending an e-mail to fidfunddocuments fidelity.com . The fees associated with this class changed during the reporting year. The variations in class fees are primarily the result of the following changes: Operating expenses |
| Material Fund Change Expenses [Text Block] | The fees associated with this class changed during the reporting year. The variations in class fees are primarily the result of the following changes: Operating expenses |
| Summary of Change Legend [Text Block] | This is a summary of certain changes to the Fund since November 1, 2023. For more complete information, you may review the Fund's next prospectus, which we expect to be available by December 30, 2024 at fundresearch.fidelity.com/prospectus/sec or upon request at 1-800-544-3455 or by sending an e-mail to fidfunddocuments fidelity.com . |
| Updated Prospectus Phone Number | 1-800-544-3455</span>" id="sjs-B350"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;">1-800-544-3455</span> |
| Updated Prospectus Email Address | fidfunddocuments@fidelity.com</span>" id="sjs-B351"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;">fidfunddocuments@fidelity.com</span> |
| Updated Prospectus Web Address | fundresearch.fidelity.com/prospectus/sec</span>" id="sjs-B352"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;">fundresearch.fidelity.com/prospectus/sec</span> |
| Fidelity SAI International Index Fund | |
| Shareholder Report [Line Items] | |
| Fund Name | Fidelity® SAI International Index Fund |
| Class Name | Fidelity® SAI International Index Fund |
| Trading Symbol | FIONX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains information about Fidelity® SAI International Index Fund for the period November 1, 2023 to October 31, 2024. |
| Shareholder Report Annual or Semi-Annual | annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the Fund at fundresearch.fidelity.com/prospectus/sec. You can also request this information by contacting us at 1-800-544-3455 or by sending an e-mail to fidfunddocuments@fidelity.com. |
| Additional Information Phone Number | 1-800-544-3455 |
| Additional Information Email | fidfunddocuments@fidelity.com |
| Additional Information Website | fundresearch.fidelity.com/prospectus/sec |
| Expenses [Text Block] | What were your Fund costs for the last year? (based on hypothetical $10,000 investment) FUND COST (PREVIOUS YEAR) Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Fidelity® SAI International Index Fund $ 0.04 % |
| Expenses Paid, Amount | $ 4 |
| Expense Ratio, Percent | 0.04% |
| Factors Affecting Performance [Text Block] | What affected the Fund's performance this period? • • • • • • |
| Performance Past Does Not Indicate Future [Text] | The Fund's past performance is not a good predictor of the Fund's future performance.</span>" id="sjs-B368"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;">The Fund's past performance is not a good predictor of the Fund's future performance.</span> |
| Line Graph [Table Text Block] | How did the Fund perform over the life of Fund? CUMULATIVE PERFORMANCE January 5, 2016 through October 31, 2024. Initial investment of $10,000. Fidelity® SAI International Index Fund $10,000 $10,190 $12,576 $11,677 $13,004 $12,158 $16,303 $12,554 $14,491 MSCI EAFE Index $10,000 $10,280 $12,715 $11,870 $13,211 $12,328 $16,574 $12,788 $14,662 2016 2017 2018 2019 2020 2021 2022 2023 2024 |
| Average Annual Return [Table Text Block] | AVERAGE ANNUAL TOTAL RETURNS: 1 Year 5 Year Life of Fund A Fidelity® SAI International Index Fund 22.26% 6.38% 6.69% MSCI EAFE Index 23.25% 6.46% 6.93% A From January 5, 2016 Visit www.fidelity.com for more recent performance information. The Fund's past performance is not a good predictor of the Fund's future performance. The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares. |
| Performance Inception Date | Jan. 05, 2016 |
| No Deduction of Taxes [Text Block] | The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares. |
| Net Assets | $ 8,526,926,983 |
| Holdings Count | shares | 740 |
| Advisory Fees Paid, Amount | $ 2,598,054 |
| Investment Company Portfolio Turnover | 4% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics (as of October 31, 2024) KEY FACTS Fund Size $ Number of Holdings 740 Total Advisory Fee $ Portfolio Turnover 4 % |
| Holdings [Text Block] | MARKET SECTORS (% of Fund's net assets) Financials 21.4 Industrials 17.5 Health Care 13.0 Consumer Discretionary 10.9 Consumer Staples 8.3 Information Technology 8.2 Materials 6.2 Communication Services 4.1 Energy 3.5 Utilities 3.2 Real Estate 1.8 Common Stocks 97.7 Preferred Stocks 0.4 Short-Term Investments and Net Other Assets (Liabilities) 1.9 ASSET ALLOCATION (% of Fund's net assets) Japan 22.0 United States 10.9 United Kingdom 10.8 France 9.3 Germany 8.9 Australia 7.5 Switzerland 6.2 Netherlands 4.0 Denmark 3.4 Others 17.0 GEOGRAPHIC DIVERSIFICATION (% of Fund's net assets) |
| Largest Holdings [Text Block] | TOP HOLDINGS (% of Fund's net assets) Novo Nordisk A/S Series B 2.2 ASML Holding NV 1.6 Nestle SA 1.5 SAP SE 1.5 Novartis AG 1.4 Astrazeneca PLC 1.3 Roche Holding AG 1.3 Shell PLC 1.3 LVMH Moet Hennessy Louis Vuitton SE 1.2 Toyota Motor Corp 1.1 14.4 |
| Fidelity Series Global ex U.S. Index Fund | |
| Shareholder Report [Line Items] | |
| Fund Name | Fidelity® Series Global ex U.S. Index Fund |
| Class Name | Fidelity® Series Global ex U.S. Index Fund |
| Trading Symbol | FSGEX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains information about Fidelity® Series Global ex U.S. Index Fund for the period November 1, 2023 to October 31, 2024. |
| Shareholder Report Annual or Semi-Annual | annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the Fund at fundresearch.fidelity.com/prospectus/sec. You can also request this information by contacting us at 1-800-544-8544. |
| Additional Information Phone Number | 1-800-544-8544 |
| Additional Information Website | fundresearch.fidelity.com/prospectus/sec |
| Expenses [Text Block] | What were your Fund costs for the last year? (based on hypothetical $10,000 investment) FUND COST (PREVIOUS YEAR) Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Fidelity® Series Global ex U.S. Index Fund $ 0.01 % |
| Expenses Paid, Amount | $ 1 |
| Expense Ratio, Percent | 0.01% |
| Factors Affecting Performance [Text Block] | What affected the Fund's performance this period? • • • • • |
| Performance Past Does Not Indicate Future [Text] | The Fund's past performance is not a good predictor of the Fund's future performance.</span>" id="sjs-B394"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;">The Fund's past performance is not a good predictor of the Fund's future performance.</span> |
| Line Graph [Table Text Block] | How did the Fund perform over the past 10 years? CUMULATIVE PERFORMANCE October 31, 2014 through October 31, 2024. Initial investment of $10,000. Fidelity® Series Global ex U.S. Index Fund $10,000 $9,447 $9,514 $11,782 $10,783 $12,008 $11,736 $15,179 $11,449 $12,894 $15,937 MSCI ACWI (All Country World Index) ex USA Index $10,000 $9,545 $9,583 $11,868 $10,910 $12,161 $11,862 $15,403 $11,613 $13,038 $16,238 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 |
| Average Annual Return [Table Text Block] | AVERAGE ANNUAL TOTAL RETURNS: 1 Year 5 Year 10 Year Fidelity® Series Global ex U.S. Index Fund 23.60% 5.83% 4.77% MSCI ACWI (All Country World Index) ex USA Index 24.55% 5.95% 4.97% Visit www.fidelity.com for more recent performance information. The Fund's past performance is not a good predictor of the Fund's future performance. The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares. |
| No Deduction of Taxes [Text Block] | The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares. |
| Net Assets | $ 49,437,743,559 |
| Holdings Count | shares | 2,205 |
| Advisory Fees Paid, Amount | $ 0 |
| Investment Company Portfolio Turnover | 3% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics (as of October 31, 2024) KEY FACTS Fund Size $ Number of Holdings 2,205 Total Advisory Fee $ Portfolio Turnover 3 % |
| Holdings [Text Block] | MARKET SECTORS (% of Fund's net assets) Financials 23.3 Industrials 13.1 Information Technology 12.8 Consumer Discretionary 10.6 Health Care 8.9 Consumer Staples 6.8 Materials 6.5 Communication Services 4.9 Energy 4.6 Utilities 3.0 Real Estate 1.6 Common Stocks 95.7 Preferred Stocks 0.4 Bonds 0.0 Short-Term Investments and Net Other Assets (Liabilities) 3.9 ASSET ALLOCATION (% of Fund's net assets) Japan 13.5 United States 9.5 China 8.2 Canada 7.4 United Kingdom 6.6 France 5.7 Germany 5.5 India 5.4 Taiwan 5.3 Others 32.9 GEOGRAPHIC DIVERSIFICATION (% of Fund's net assets) |
| Largest Holdings [Text Block] | TOP HOLDINGS (% of Fund's net assets) Taiwan Semiconductor Manufacturing Co Ltd 2.9 Novo Nordisk A/S Series B 1.3 Tencent Holdings Ltd 1.2 ASML Holding NV 1.1 SAP SE 1.0 Nestle SA 0.9 Roche Holding AG 0.9 Astrazeneca PLC 0.8 Novartis AG 0.8 Shell PLC 0.8 11.7 |
| Fidelity SAI International Low Volatility Index Fund | |
| Shareholder Report [Line Items] | |
| Fund Name | Fidelity® SAI International Low Volatility Index Fund |
| Class Name | Fidelity® SAI International Low Volatility Index Fund |
| Trading Symbol | FSKLX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains information about Fidelity® SAI International Low Volatility Index Fund for the period November 1, 2023 to October 31, 2024. |
| Shareholder Report Annual or Semi-Annual | annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the Fund at fundresearch.fidelity.com/prospectus/sec. You can also request this information by contacting us at 1-800-544-3455 or by sending an e-mail to fidfunddocuments@fidelity.com. |
| Material Fund Change Notice [Text Block] | This report describes changes to the Fund that occurred during the reporting period. |
| Additional Information Phone Number | 1-800-544-3455 |
| Additional Information Email | fidfunddocuments@fidelity.com |
| Additional Information Website | fundresearch.fidelity.com/prospectus/sec |
| Expenses [Text Block] | What were your Fund costs for the last year? (based on hypothetical $10,000 investment) FUND COST (PREVIOUS YEAR) Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Fidelity® SAI International Low Volatility Index Fund $ 0.16 % |
| Expenses Paid, Amount | $ 18 |
| Expense Ratio, Percent | 0.16% |
| Factors Affecting Performance [Text Block] | What affected the Fund's performance this period? • • • • • |
| Performance Past Does Not Indicate Future [Text] | The Fund's past performance is not a good predictor of the Fund's future performance.</span>" id="sjs-B421"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;">The Fund's past performance is not a good predictor of the Fund's future performance.</span> |
| Line Graph [Table Text Block] | How did the Fund perform over the life of Fund? CUMULATIVE PERFORMANCE May 29, 2015 through October 31, 2024. Initial investment of $10,000. Fidelity® SAI International Low Volatility Index Fund $10,000 $9,610 $9,874 $11,272 $11,106 $12,538 $11,120 $13,643 $10,941 $12,371 Fidelity SAI International Low Volatility Index Fund Linked Index℠ $10,000 $9,703 $9,922 $11,376 $11,234 $12,745 $11,318 $13,908 $11,204 $12,606 Fidelity International Low Volatility Focus Index℠ $10,000 $9,610 $9,874 $11,272 $11,106 $12,686 $11,265 $13,843 $11,152 $12,548 MSCI ACWI (All Country World Index) ex USA Index $10,000 $9,176 $9,213 $11,410 $10,488 $11,691 $11,404 $14,808 $11,164 $12,534 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 |
| Average Annual Return [Table Text Block] | AVERAGE ANNUAL TOTAL RETURNS: 1 Year 5 Year Life of Fund A Fidelity® SAI International Low Volatility Index Fund 16.34% 2.80% 3.94% Fidelity SAI International Low Volatility Index Fund Linked Index℠ 17.05% 2.97% 4.22% Fidelity International Low Volatility Focus Index℠ 17.05% 2.97% n/a MSCI ACWI (All Country World Index) ex USA Index 24.55% 5.95% 4.84% A From May 29, 2015 Visit www.fidelity.com for more recent performance information. The Fund's past performance is not a good predictor of the Fund's future performance. The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares. |
| Performance Inception Date | May 29, 2015 |
| No Deduction of Taxes [Text Block] | The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares. |
| Net Assets | $ 5,441,570,004 |
| Holdings Count | shares | 128 |
| Advisory Fees Paid, Amount | $ 10,420,959 |
| Investment Company Portfolio Turnover | 31% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics (as of October 31, 2024) KEY FACTS Fund Size $ Number of Holdings 128 Total Advisory Fee $ Portfolio Turnover 31 % |
| Holdings [Text Block] | MARKET SECTORS (% of Fund's net assets) Financials 17.6 Health Care 16.3 Industrials 13.4 Consumer Staples 13.3 Communication Services 8.8 Utilities 8.2 Materials 6.2 Consumer Discretionary 6.1 Real Estate 5.3 Information Technology 3.9 Common Stocks 99.1 Short-Term Investments and Net Other Assets (Liabilities) 0.9 ASSET ALLOCATION (% of Fund's net assets) Japan 29.7 United Kingdom 13.5 Switzerland 10.9 United States 9.8 Netherlands 5.8 Germany 5.6 Hong Kong 4.8 Denmark 4.5 France 4.1 Others 11.3 GEOGRAPHIC DIVERSIFICATION (% of Fund's net assets) |
| Largest Holdings [Text Block] | TOP HOLDINGS (% of Fund's net assets) Sanofi SA 2.1 Unilever PLC 2.0 RELX PLC 2.0 Reckitt Benckiser Group PLC 2.0 Air Liquide SA 2.0 Deutsche Boerse AG 1.9 Novartis AG 1.9 Roche Holding AG 1.9 Tokio Marine Holdings Inc 1.9 CSL Ltd 1.8 19.5 |
| Material Fund Change [Text Block] | How has the Fund changed? This is a summary of certain changes to the Fund since November 1, 2023. For more complete information, you may review the Fund's next prospectus, which we expect to be available by December 28, 2024 at fundresearch.fidelity.com/prospectus/sec or upon request at 1-800-544-3455 or by sending an e-mail to fidfunddocuments fidelity.com . The fees associated with this class changed during the reporting year. The variations in class fees are primarily the result of the following changes: Operating expenses |
| Material Fund Change Expenses [Text Block] | The fees associated with this class changed during the reporting year. The variations in class fees are primarily the result of the following changes: Operating expenses |
| Summary of Change Legend [Text Block] | This is a summary of certain changes to the Fund since November 1, 2023. For more complete information, you may review the Fund's next prospectus, which we expect to be available by December 28, 2024 at fundresearch.fidelity.com/prospectus/sec or upon request at 1-800-544-3455 or by sending an e-mail to fidfunddocuments fidelity.com . |
| Updated Prospectus Phone Number | 1-800-544-3455</span>" id="sjs-B436"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;">1-800-544-3455</span> |
| Updated Prospectus Email Address | fidfunddocuments@fidelity.com</span>" id="sjs-B437"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;">fidfunddocuments@fidelity.com</span> |
| Updated Prospectus Web Address | fundresearch.fidelity.com/prospectus/sec</span>" id="sjs-B438"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;">fundresearch.fidelity.com/prospectus/sec</span> |
| Fidelity SAI U.S. Low Volatility Index Fund | |
| Shareholder Report [Line Items] | |
| Fund Name | Fidelity® SAI U.S. Low Volatility Index Fund |
| Class Name | Fidelity® SAI U.S. Low Volatility Index Fund |
| Trading Symbol | FSUVX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains information about Fidelity® SAI U.S. Low Volatility Index Fund for the period November 1, 2023 to October 31, 2024. |
| Shareholder Report Annual or Semi-Annual | annual shareholder report |
| Additional Information [Text Block] | You can find additional information about the Fund at fundresearch.fidelity.com/prospectus/sec. You can also request this information by contacting us at 1-800-544-3455 or by sending an e-mail to fidfunddocuments@fidelity.com. |
| Additional Information Phone Number | 1-800-544-3455 |
| Additional Information Email | fidfunddocuments@fidelity.com |
| Additional Information Website | fundresearch.fidelity.com/prospectus/sec |
| Expenses [Text Block] | What were your Fund costs for the last year? (based on hypothetical $10,000 investment) FUND COST (PREVIOUS YEAR) Costs of a $10,000 investment Costs paid as a percentage of a $10,000 investment Fidelity® SAI U.S. Low Volatility Index Fund $ 0.11 % |
| Expenses Paid, Amount | $ 13 |
| Expense Ratio, Percent | 0.11% |
| Factors Affecting Performance [Text Block] | What affected the Fund's performance this period? • • • • |
| Performance Past Does Not Indicate Future [Text] | The Fund's past performance is not a good predictor of the Fund's future performance.</span>" id="sjs-B454"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;">The Fund's past performance is not a good predictor of the Fund's future performance.</span> |
| Line Graph [Table Text Block] | How did the Fund perform over the life of Fund? CUMULATIVE PERFORMANCE May 29, 2015 through October 31, 2024. Initial investment of $10,000. Fidelity® SAI U.S. Low Volatility Index Fund $10,000 $10,220 $10,993 $13,038 $14,184 $16,684 $17,044 $22,369 $20,492 $21,801 Fidelity SAI U.S. Low Volatility Index Fund Linked Index℠ $10,000 $10,235 $11,023 $13,098 $14,264 $16,795 $17,177 $22,550 $20,677 $22,013 Fidelity U.S. Low Volatility Focus Index℠ $10,000 $10,220 $10,993 $13,038 $14,184 $16,549 $16,927 $22,221 $20,375 $21,692 S&P 500® Index $10,000 $9,949 $10,398 $12,855 $13,799 $15,776 $17,308 $24,735 $21,121 $23,264 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 |
| Average Annual Return [Table Text Block] | AVERAGE ANNUAL TOTAL RETURNS: 1 Year 5 Year Life of Fund A Fidelity® SAI U.S. Low Volatility Index Fund 29.21% 11.04% 11.63% Fidelity SAI U.S. Low Volatility Index Fund Linked Index℠ 29.39% 11.14% 11.76% Fidelity U.S. Low Volatility Focus Index℠ 29.39% 11.14% n/a S&P 500® Index 38.02% 15.27% 13.19% A From May 29, 2015 Visit www.fidelity.com for more recent performance information. The Fund's past performance is not a good predictor of the Fund's future performance. The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares. |
| Performance Inception Date | May 29, 2015 |
| No Deduction of Taxes [Text Block] | The graph and table do not reflect the deduction of taxes that a shareholder would pay on fund distributions or redemption of fund shares. |
| Net Assets | $ 16,879,173,125 |
| Holdings Count | shares | 176 |
| Advisory Fees Paid, Amount | $ 13,229,356 |
| Investment Company Portfolio Turnover | 32% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics (as of October 31, 2024) KEY FACTS Fund Size $ Number of Holdings 176 Total Advisory Fee $ Portfolio Turnover 32 % |
| Holdings [Text Block] | MARKET SECTORS (% of Fund's net assets) Information Technology 28.4 Health Care 13.0 Financials 11.7 Industrials 9.4 Consumer Discretionary 8.3 Consumer Staples 7.2 Communication Services 6.9 Real Estate 4.5 Utilities 4.3 Materials 4.3 Energy 1.8 Common Stocks 99.8 Short-Term Investments and Net Other Assets (Liabilities) 0.2 ASSET ALLOCATION (% of Fund's net assets) United States 100.0 GEOGRAPHIC DIVERSIFICATION (% of Fund's net assets) |
| Largest Holdings [Text Block] | TOP HOLDINGS (% of Fund's net assets) Microsoft Corp 7.7 Apple Inc 4.3 NVIDIA Corp 3.9 Eli Lilly & Co 3.3 Visa Inc Class A 3.0 UnitedHealth Group Inc 2.9 Home Depot Inc/The 2.9 Procter & Gamble Co/The 2.8 Johnson & Johnson 2.6 Oracle Corp 2.6 36.0 |
| Shareholder Report, Line Graph (Details) - USD ($) | 12 Months Ended | 60 Months Ended | 72 Months Ended | 96 Months Ended | 108 Months Ended | 120 Months Ended | 132 Months Ended | ||||||||||
| Oct. 31, 2024 | Oct. 31, 2024 | Oct. 31, 2024 | Oct. 31, 2024 | Oct. 31, 2024 | Oct. 31, 2024 | Oct. 31, 2024 | Oct. 31, 2023 | Oct. 31, 2022 | Oct. 31, 2021 | Oct. 31, 2020 | Oct. 31, 2019 | Oct. 31, 2018 | Oct. 31, 2017 | Oct. 31, 2016 | Oct. 31, 2015 | Oct. 31, 2014 | |
| C000206607_1_BBIndexMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 24.55% | ||||||||||||||||
| C000206607_1_BBIndexMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 5.95% | ||||||||||||||||
| C000206607_1_BBIndexMember_LOCMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 6.66% | ||||||||||||||||
| C000218746_1_BBIndexMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 25.33% | ||||||||||||||||
| C000218746_1_BBIndexMember_LOCMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 7.44% | ||||||||||||||||
| C000177582_0_BBIndexMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 24.55% | ||||||||||||||||
| C000177582_0_BBIndexMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 5.95% | ||||||||||||||||
| C000177582_0_BBIndexMember_LOCMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 6.47% | ||||||||||||||||
| C000183133_1_BBIndexMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 24.55% | ||||||||||||||||
| C000183133_1_BBIndexMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 5.95% | ||||||||||||||||
| C000183133_1_BBIndexMember_LOCMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 5.67% | ||||||||||||||||
| C000103365_0_BBIndexMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 24.55% | ||||||||||||||||
| C000103365_0_BBIndexMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 5.95% | ||||||||||||||||
| C000103365_0_BBIndexMember_10YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 4.97% | ||||||||||||||||
| C000170041_0_BBIndexMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 24.46% | ||||||||||||||||
| C000170041_0_BBIndexMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 6% | ||||||||||||||||
| C000170041_0_BBIndexMember_LOCMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 6.61% | ||||||||||||||||
| C000103361_1_BBIndexMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 25.33% | ||||||||||||||||
| C000103361_1_BBIndexMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 3.95% | ||||||||||||||||
| C000103361_1_BBIndexMember_10YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 3.46% | ||||||||||||||||
| C000183136_1_BBIndexMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 37.82% | ||||||||||||||||
| C000183136_1_BBIndexMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 14.73% | ||||||||||||||||
| C000183136_1_BBIndexMember_LOCMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 13.65% | ||||||||||||||||
| C000218748_1_BBIndexMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 24.55% | ||||||||||||||||
| C000218748_1_BBIndexMember_LOCMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 10.26% | ||||||||||||||||
| C000163541_0_BBIndexMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 25.33% | ||||||||||||||||
| C000163541_0_BBIndexMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 3.95% | ||||||||||||||||
| C000163541_0_BBIndexMember_LOCMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 6.93% | ||||||||||||||||
| C000218747_1_BBIndexMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 24.55% | ||||||||||||||||
| C000218747_1_BBIndexMember_LOCMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 10.26% | ||||||||||||||||
| C000195573_1_BBIndexMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 24.55% | ||||||||||||||||
| C000195573_1_BBIndexMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 5.95% | ||||||||||||||||
| C000195573_1_BBIndexMember_LOCMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 4.45% | ||||||||||||||||
| C000163542_0_BBIndexMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 23.25% | ||||||||||||||||
| C000163542_0_BBIndexMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 6.46% | ||||||||||||||||
| C000163542_0_BBIndexMember_LOCMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 6.93% | ||||||||||||||||
| C000079292_0_BBIndexMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 24.55% | ||||||||||||||||
| C000079292_0_BBIndexMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 5.95% | ||||||||||||||||
| C000079292_0_BBIndexMember_10YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 4.97% | ||||||||||||||||
| C000155835_0_LG_BBIndexMember_10YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | MSCI ACWI (All Country World Index) ex USA Index</span>" id="sjs-G122"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">MSCI ACWI (All Country World Index) ex USA Index</span> | ||||||||||||||||
| C000155835_0_BBIndexMember_AsOf_2015Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 10,000 | ||||||||||||||||
| C000155835_0_BBIndexMember_AsOf_2016Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 9,176 | ||||||||||||||||
| C000155835_0_BBIndexMember_AsOf_2017Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 9,213 | ||||||||||||||||
| C000155835_0_BBIndexMember_AsOf_2018Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 11,410 | ||||||||||||||||
| C000155835_0_BBIndexMember_AsOf_2019Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 10,488 | ||||||||||||||||
| C000155835_0_BBIndexMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 11,691 | ||||||||||||||||
| C000155835_0_BBIndexMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 11,404 | ||||||||||||||||
| C000155835_0_BBIndexMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 14,808 | ||||||||||||||||
| C000155835_0_BBIndexMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 11,164 | ||||||||||||||||
| C000155835_0_BBIndexMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 12,534 | $ 12,534 | $ 12,534 | $ 12,534 | $ 12,534 | $ 12,534 | $ 12,534 | ||||||||||
| C000155835_2_BBIndexMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 24.55% | ||||||||||||||||
| C000155835_2_BBIndexMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 5.95% | ||||||||||||||||
| C000155835_2_BBIndexMember_LOCMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 4.84% | ||||||||||||||||
| C000155834_0_LG_BBIndexMember_10YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | S&P 500® Index</span>" id="sjs-G164"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">S&P 500® Index</span> | ||||||||||||||||
| C000155834_0_BBIndexMember_AsOf_2015Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,000 | ||||||||||||||||
| C000155834_0_BBIndexMember_AsOf_2016Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 9,949 | ||||||||||||||||
| C000155834_0_BBIndexMember_AsOf_2017Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,398 | ||||||||||||||||
| C000155834_0_BBIndexMember_AsOf_2018Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 12,855 | ||||||||||||||||
| C000155834_0_BBIndexMember_AsOf_2019Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 13,799 | ||||||||||||||||
| C000155834_0_BBIndexMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 15,776 | ||||||||||||||||
| C000155834_0_BBIndexMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 17,308 | ||||||||||||||||
| C000155834_0_BBIndexMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 24,735 | ||||||||||||||||
| C000155834_0_BBIndexMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 21,121 | ||||||||||||||||
| C000155834_0_BBIndexMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 23,264 | $ 23,264 | $ 23,264 | 23,264 | 23,264 | $ 23,264 | 23,264 | ||||||||||
| C000155834_2_BBIndexMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 38.02% | ||||||||||||||||
| C000155834_2_BBIndexMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 15.27% | ||||||||||||||||
| C000155834_2_BBIndexMember_LOCMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 13.19% | ||||||||||||||||
| C000206607_LG_ClassMember_6YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | Fidelity® SAI Emerging Markets Low Volatility Index Fund</span>" id="sjs-D206"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Fidelity® SAI Emerging Markets Low Volatility Index Fund</span> | ||||||||||||||||
| C000206607_ClassMember_AsOf_2019Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,000 | ||||||||||||||||
| C000206607_ClassMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,110 | ||||||||||||||||
| C000206607_ClassMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 9,595 | ||||||||||||||||
| C000206607_ClassMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,877 | ||||||||||||||||
| C000206607_ClassMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 9,872 | ||||||||||||||||
| C000206607_ClassMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 10,999 | $ 10,999 | $ 10,999 | 10,999 | 10,999 | 10,999 | 10,999 | ||||||||||
| C000206607_LG_1_AdditionalIndexMember_6YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | Fidelity Emerging Markets Low Volatility Focus Index℠</span>" id="sjs-D227"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Fidelity Emerging Markets Low Volatility Focus Index℠</span> | ||||||||||||||||
| C000206607_1_AdditionalIndexMember_AsOf_2019Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,000 | ||||||||||||||||
| C000206607_1_AdditionalIndexMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,258 | ||||||||||||||||
| C000206607_1_AdditionalIndexMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 9,827 | ||||||||||||||||
| C000206607_1_AdditionalIndexMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 12,283 | ||||||||||||||||
| C000206607_1_AdditionalIndexMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,249 | ||||||||||||||||
| C000206607_1_AdditionalIndexMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,472 | 11,472 | $ 11,472 | 11,472 | 11,472 | 11,472 | 11,472 | ||||||||||
| C000206607_LG_2_AdditionalIndexMember_6YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | MSCI ACWI (All Country World Index) ex USA Index</span>" id="sjs-D248"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">MSCI ACWI (All Country World Index) ex USA Index</span> | ||||||||||||||||
| C000206607_2_AdditionalIndexMember_AsOf_2019Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,000 | ||||||||||||||||
| C000206607_2_AdditionalIndexMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,858 | ||||||||||||||||
| C000206607_2_AdditionalIndexMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,590 | ||||||||||||||||
| C000206607_2_AdditionalIndexMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 13,752 | ||||||||||||||||
| C000206607_2_AdditionalIndexMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,368 | ||||||||||||||||
| C000206607_2_AdditionalIndexMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 11,640 | $ 11,640 | $ 11,640 | 11,640 | 11,640 | 11,640 | 11,640 | ||||||||||
| C000206607_NoLoadClassMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 18.98% | ||||||||||||||||
| C000206607_NoLoadClassMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 5.30% | ||||||||||||||||
| C000206607_NoLoadClassMember_2023-11-01_2024-10-31Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 4.78% | ||||||||||||||||
| C000206607_0_AdditionalIndexMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 20.82% | ||||||||||||||||
| C000206607_0_AdditionalIndexMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 6.21% | ||||||||||||||||
| C000206607_0_AdditionalIndexMember_LOCMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 5.84% | ||||||||||||||||
| C000218746_LG_ClassMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | Fidelity® SAI Emerging Markets Value Index Fund</span>" id="sjs-C287"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Fidelity® SAI Emerging Markets Value Index Fund</span> | ||||||||||||||||
| C000218746_ClassMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,000 | ||||||||||||||||
| C000218746_ClassMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,780 | ||||||||||||||||
| C000218746_ClassMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 14,527 | ||||||||||||||||
| C000218746_ClassMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,868 | ||||||||||||||||
| C000218746_ClassMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 12,586 | $ 12,586 | 12,586 | 12,586 | 12,586 | 12,586 | 12,586 | ||||||||||
| C000218746_LG_1_AdditionalIndexMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | Fidelity Emerging Markets Value Focus Index℠</span>" id="sjs-C305"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Fidelity Emerging Markets Value Focus Index℠</span> | ||||||||||||||||
| C000218746_1_AdditionalIndexMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,000 | ||||||||||||||||
| C000218746_1_AdditionalIndexMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,814 | ||||||||||||||||
| C000218746_1_AdditionalIndexMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 14,782 | ||||||||||||||||
| C000218746_1_AdditionalIndexMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,036 | ||||||||||||||||
| C000218746_1_AdditionalIndexMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 12,841 | $ 12,841 | 12,841 | 12,841 | 12,841 | 12,841 | 12,841 | ||||||||||
| C000218746_LG_2_AdditionalIndexMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | MSCI Emerging Markets Index</span>" id="sjs-C323"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">MSCI Emerging Markets Index</span> | ||||||||||||||||
| C000218746_2_AdditionalIndexMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,000 | ||||||||||||||||
| C000218746_2_AdditionalIndexMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 12,298 | ||||||||||||||||
| C000218746_2_AdditionalIndexMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 14,386 | ||||||||||||||||
| C000218746_2_AdditionalIndexMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 9,924 | ||||||||||||||||
| C000218746_2_AdditionalIndexMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 11,000 | $ 11,000 | 11,000 | $ 11,000 | 11,000 | 11,000 | 11,000 | ||||||||||
| C000218746_NoLoadClassMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 29.09% | ||||||||||||||||
| C000218746_NoLoadClassMember_2023-11-01_2024-10-31Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 11.46% | ||||||||||||||||
| C000218746_0_AdditionalIndexMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 31.84% | ||||||||||||||||
| C000218746_0_AdditionalIndexMember_LOCMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 12.49% | ||||||||||||||||
| C000177582_LG_ClassMember_8YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | Fidelity Flex® International Index Fund</span>" id="sjs-E353"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Fidelity Flex® International Index Fund</span> | ||||||||||||||||
| C000177582_ClassMember_AsOf_2017Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,000 | ||||||||||||||||
| C000177582_ClassMember_AsOf_2018Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,790 | ||||||||||||||||
| C000177582_ClassMember_AsOf_2019Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,785 | ||||||||||||||||
| C000177582_ClassMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 12,014 | ||||||||||||||||
| C000177582_ClassMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,745 | ||||||||||||||||
| C000177582_ClassMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 15,188 | ||||||||||||||||
| C000177582_ClassMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,452 | ||||||||||||||||
| C000177582_ClassMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 12,909 | 12,909 | 12,909 | $ 12,909 | 12,909 | 12,909 | 12,909 | ||||||||||
| C000177582_LG_1_AdditionalIndexMember_8YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | MSCI ACWI (All Country World Index) ex USA Index</span>" id="sjs-E380"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">MSCI ACWI (All Country World Index) ex USA Index</span> | ||||||||||||||||
| C000177582_1_AdditionalIndexMember_AsOf_2017Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,000 | ||||||||||||||||
| C000177582_1_AdditionalIndexMember_AsOf_2018Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,809 | ||||||||||||||||
| C000177582_1_AdditionalIndexMember_AsOf_2019Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,855 | ||||||||||||||||
| C000177582_1_AdditionalIndexMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 12,101 | ||||||||||||||||
| C000177582_1_AdditionalIndexMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,803 | ||||||||||||||||
| C000177582_1_AdditionalIndexMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 15,326 | ||||||||||||||||
| C000177582_1_AdditionalIndexMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,555 | ||||||||||||||||
| C000177582_1_AdditionalIndexMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 12,973 | $ 12,973 | 12,973 | $ 12,973 | 12,973 | 12,973 | 12,973 | ||||||||||
| C000177582_NoLoadClassMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 23.59% | ||||||||||||||||
| C000177582_NoLoadClassMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 5.84% | ||||||||||||||||
| C000177582_NoLoadClassMember_2023-11-01_2024-10-31Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 6.30% | ||||||||||||||||
| C000183133_LG_ClassMember_8YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | Fidelity® International Sustainability Index Fund</span>" id="sjs-E416"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Fidelity® International Sustainability Index Fund</span> | ||||||||||||||||
| C000183133_ClassMember_AsOf_2017Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,000 | ||||||||||||||||
| C000183133_ClassMember_AsOf_2018Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,960 | ||||||||||||||||
| C000183133_ClassMember_AsOf_2019Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 9,999 | ||||||||||||||||
| C000183133_ClassMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,279 | ||||||||||||||||
| C000183133_ClassMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,447 | ||||||||||||||||
| C000183133_ClassMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 14,568 | ||||||||||||||||
| C000183133_ClassMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,473 | ||||||||||||||||
| C000183133_ClassMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 11,801 | $ 11,801 | 11,801 | $ 11,801 | 11,801 | 11,801 | 11,801 | ||||||||||
| C000183133_LG_1_AdditionalIndexMember_8YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | MSCI ACWI (All Country World Index) ex USA ESG Leaders Index</span>" id="sjs-E443"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">MSCI ACWI (All Country World Index) ex USA ESG Leaders Index</span> | ||||||||||||||||
| C000183133_1_AdditionalIndexMember_AsOf_2017Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,000 | ||||||||||||||||
| C000183133_1_AdditionalIndexMember_AsOf_2018Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,000 | ||||||||||||||||
| C000183133_1_AdditionalIndexMember_AsOf_2019Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,114 | ||||||||||||||||
| C000183133_1_AdditionalIndexMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,464 | ||||||||||||||||
| C000183133_1_AdditionalIndexMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,667 | ||||||||||||||||
| C000183133_1_AdditionalIndexMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 14,934 | ||||||||||||||||
| C000183133_1_AdditionalIndexMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,741 | ||||||||||||||||
| C000183133_1_AdditionalIndexMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 12,069 | 12,069 | 12,069 | $ 12,069 | 12,069 | 12,069 | 12,069 | ||||||||||
| C000183133_LG_2_AdditionalIndexMember_8YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | MSCI ACWI (All Country World Index) ex USA Index</span>" id="sjs-E470"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">MSCI ACWI (All Country World Index) ex USA Index</span> | ||||||||||||||||
| C000183133_2_AdditionalIndexMember_AsOf_2017Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,000 | ||||||||||||||||
| C000183133_2_AdditionalIndexMember_AsOf_2018Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,047 | ||||||||||||||||
| C000183133_2_AdditionalIndexMember_AsOf_2019Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,155 | ||||||||||||||||
| C000183133_2_AdditionalIndexMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,320 | ||||||||||||||||
| C000183133_2_AdditionalIndexMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,041 | ||||||||||||||||
| C000183133_2_AdditionalIndexMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 14,338 | ||||||||||||||||
| C000183133_2_AdditionalIndexMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,809 | ||||||||||||||||
| C000183133_2_AdditionalIndexMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 12,136 | $ 12,136 | 12,136 | $ 12,136 | 12,136 | 12,136 | $ 12,136 | ||||||||||
| C000183133_NoLoadClassMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 23.62% | ||||||||||||||||
| C000183133_NoLoadClassMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 5.28% | ||||||||||||||||
| C000183133_NoLoadClassMember_2023-11-01_2024-10-31Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 5.17% | ||||||||||||||||
| C000183133_0_AdditionalIndexMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 24.93% | ||||||||||||||||
| C000183133_0_AdditionalIndexMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 5.63% | ||||||||||||||||
| C000183133_0_AdditionalIndexMember_LOCMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 5.64% | ||||||||||||||||
| C000103365_LG_ClassMember_11YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | Fidelity® Global ex U.S. Index Fund</span>" id="sjs-H515"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Fidelity® Global ex U.S. Index Fund</span> | ||||||||||||||||
| C000103365_ClassMember_AsOf_2014Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 10,000 | ||||||||||||||||
| C000103365_ClassMember_AsOf_2015Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 9,455 | ||||||||||||||||
| C000103365_ClassMember_AsOf_2016Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 9,520 | ||||||||||||||||
| C000103365_ClassMember_AsOf_2017Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,788 | ||||||||||||||||
| C000103365_ClassMember_AsOf_2018Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,789 | ||||||||||||||||
| C000103365_ClassMember_AsOf_2019Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 12,007 | ||||||||||||||||
| C000103365_ClassMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,737 | ||||||||||||||||
| C000103365_ClassMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 15,170 | ||||||||||||||||
| C000103365_ClassMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,444 | ||||||||||||||||
| C000103365_ClassMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 12,903 | ||||||||||||||||
| C000103365_ClassMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 15,944 | $ 15,944 | 15,944 | 15,944 | 15,944 | 15,944 | $ 15,944 | ||||||||||
| C000103365_LG_1_AdditionalIndexMember_11YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | MSCI ACWI (All Country World Index) ex USA Index</span>" id="sjs-H551"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">MSCI ACWI (All Country World Index) ex USA Index</span> | ||||||||||||||||
| C000103365_1_AdditionalIndexMember_AsOf_2014Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,000 | ||||||||||||||||
| C000103365_1_AdditionalIndexMember_AsOf_2015Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 9,545 | ||||||||||||||||
| C000103365_1_AdditionalIndexMember_AsOf_2016Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 9,583 | ||||||||||||||||
| C000103365_1_AdditionalIndexMember_AsOf_2017Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,868 | ||||||||||||||||
| C000103365_1_AdditionalIndexMember_AsOf_2018Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,910 | ||||||||||||||||
| C000103365_1_AdditionalIndexMember_AsOf_2019Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 12,161 | ||||||||||||||||
| C000103365_1_AdditionalIndexMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,862 | ||||||||||||||||
| C000103365_1_AdditionalIndexMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 15,403 | ||||||||||||||||
| C000103365_1_AdditionalIndexMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,613 | ||||||||||||||||
| C000103365_1_AdditionalIndexMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 13,038 | ||||||||||||||||
| C000103365_1_AdditionalIndexMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 16,238 | $ 16,238 | 16,238 | 16,238 | $ 16,238 | $ 16,238 | $ 16,238 | ||||||||||
| C000103365_NoLoadClassMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 23.57% | ||||||||||||||||
| C000103365_NoLoadClassMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 5.84% | ||||||||||||||||
| C000103365_NoLoadClassMember_10YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 4.78% | ||||||||||||||||
| C000170041_LG_ClassMember_9YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | Fidelity® Total International Index Fund</span>" id="sjs-F596"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Fidelity® Total International Index Fund</span> | ||||||||||||||||
| C000170041_ClassMember_AsOf_2016Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,000 | ||||||||||||||||
| C000170041_ClassMember_AsOf_2017Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,090 | ||||||||||||||||
| C000170041_ClassMember_AsOf_2018Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 12,448 | ||||||||||||||||
| C000170041_ClassMember_AsOf_2019Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,401 | ||||||||||||||||
| C000170041_ClassMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 12,641 | ||||||||||||||||
| C000170041_ClassMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 12,392 | ||||||||||||||||
| C000170041_ClassMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 16,167 | ||||||||||||||||
| C000170041_ClassMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 12,124 | ||||||||||||||||
| C000170041_ClassMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 13,614 | $ 13,614 | 13,614 | 13,614 | $ 13,614 | $ 13,614 | 13,614 | ||||||||||
| C000170041_LG_1_AdditionalIndexMember_9YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | MSCI ACWI (All Country World Index) ex USA Investable Market Index</span>" id="sjs-F626"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">MSCI ACWI (All Country World Index) ex USA Investable Market Index</span> | ||||||||||||||||
| C000170041_1_AdditionalIndexMember_AsOf_2016Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,000 | ||||||||||||||||
| C000170041_1_AdditionalIndexMember_AsOf_2017Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,131 | ||||||||||||||||
| C000170041_1_AdditionalIndexMember_AsOf_2018Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 12,561 | ||||||||||||||||
| C000170041_1_AdditionalIndexMember_AsOf_2019Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,520 | ||||||||||||||||
| C000170041_1_AdditionalIndexMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 12,802 | ||||||||||||||||
| C000170041_1_AdditionalIndexMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 12,530 | ||||||||||||||||
| C000170041_1_AdditionalIndexMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 16,426 | ||||||||||||||||
| C000170041_1_AdditionalIndexMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 12,311 | ||||||||||||||||
| C000170041_1_AdditionalIndexMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 13,764 | $ 13,764 | 13,764 | 13,764 | $ 13,764 | 13,764 | $ 13,764 | ||||||||||
| C000170041_NoLoadClassMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 23.34% | ||||||||||||||||
| C000170041_NoLoadClassMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 5.84% | ||||||||||||||||
| C000170041_NoLoadClassMember_2023-11-01_2024-10-31Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 6.36% | ||||||||||||||||
| C000103361_LG_ClassMember_11YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | Fidelity® Emerging Markets Index Fund</span>" id="sjs-H665"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Fidelity® Emerging Markets Index Fund</span> | ||||||||||||||||
| C000103361_ClassMember_AsOf_2014Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,000 | ||||||||||||||||
| C000103361_ClassMember_AsOf_2015Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 8,454 | ||||||||||||||||
| C000103361_ClassMember_AsOf_2016Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 9,297 | ||||||||||||||||
| C000103361_ClassMember_AsOf_2017Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,741 | ||||||||||||||||
| C000103361_ClassMember_AsOf_2018Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,256 | ||||||||||||||||
| C000103361_ClassMember_AsOf_2019Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,418 | ||||||||||||||||
| C000103361_ClassMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 12,393 | ||||||||||||||||
| C000103361_ClassMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 14,369 | ||||||||||||||||
| C000103361_ClassMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 9,943 | ||||||||||||||||
| C000103361_ClassMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,011 | ||||||||||||||||
| C000103361_ClassMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 13,612 | $ 13,612 | 13,612 | 13,612 | 13,612 | 13,612 | $ 13,612 | ||||||||||
| C000103361_LG_1_AdditionalIndexMember_11YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | Fidelity Emerging Markets Index Fund Linked Index℠</span>" id="sjs-H701"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Fidelity Emerging Markets Index Fund Linked Index℠</span> | ||||||||||||||||
| C000103361_1_AdditionalIndexMember_AsOf_2014Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,000 | ||||||||||||||||
| C000103361_1_AdditionalIndexMember_AsOf_2015Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 8,507 | ||||||||||||||||
| C000103361_1_AdditionalIndexMember_AsOf_2016Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 9,373 | ||||||||||||||||
| C000103361_1_AdditionalIndexMember_AsOf_2017Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,858 | ||||||||||||||||
| C000103361_1_AdditionalIndexMember_AsOf_2018Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,377 | ||||||||||||||||
| C000103361_1_AdditionalIndexMember_AsOf_2019Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,611 | ||||||||||||||||
| C000103361_1_AdditionalIndexMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 12,571 | ||||||||||||||||
| C000103361_1_AdditionalIndexMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 14,706 | ||||||||||||||||
| C000103361_1_AdditionalIndexMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,145 | ||||||||||||||||
| C000103361_1_AdditionalIndexMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,244 | ||||||||||||||||
| C000103361_1_AdditionalIndexMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 14,092 | 14,092 | 14,092 | 14,092 | 14,092 | 14,092 | $ 14,092 | ||||||||||
| C000103361_LG_2_AdditionalIndexMember_11YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | MSCI Emerging Markets Index</span>" id="sjs-H737"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">MSCI Emerging Markets Index</span> | ||||||||||||||||
| C000103361_2_AdditionalIndexMember_AsOf_2014Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,000 | ||||||||||||||||
| C000103361_2_AdditionalIndexMember_AsOf_2015Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 8,550 | ||||||||||||||||
| C000103361_2_AdditionalIndexMember_AsOf_2016Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 9,346 | ||||||||||||||||
| C000103361_2_AdditionalIndexMember_AsOf_2017Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,823 | ||||||||||||||||
| C000103361_2_AdditionalIndexMember_AsOf_2018Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,347 | ||||||||||||||||
| C000103361_2_AdditionalIndexMember_AsOf_2019Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,577 | ||||||||||||||||
| C000103361_2_AdditionalIndexMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 12,535 | ||||||||||||||||
| C000103361_2_AdditionalIndexMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 14,663 | ||||||||||||||||
| C000103361_2_AdditionalIndexMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,115 | ||||||||||||||||
| C000103361_2_AdditionalIndexMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,211 | ||||||||||||||||
| C000103361_2_AdditionalIndexMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 14,051 | $ 14,051 | 14,051 | $ 14,051 | 14,051 | $ 14,051 | $ 14,051 | ||||||||||
| C000103361_NoLoadClassMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 23.63% | ||||||||||||||||
| C000103361_NoLoadClassMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 3.58% | ||||||||||||||||
| C000103361_NoLoadClassMember_10YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 3.13% | ||||||||||||||||
| C000103361_0_AdditionalIndexMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 25.33% | ||||||||||||||||
| C000103361_0_AdditionalIndexMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 3.95% | ||||||||||||||||
| C000103361_0_AdditionalIndexMember_10YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 3.49% | ||||||||||||||||
| C000183136_LG_ClassMember_8YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | Fidelity® U.S. Sustainability Index Fund</span>" id="sjs-E791"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Fidelity® U.S. Sustainability Index Fund</span> | ||||||||||||||||
| C000183136_ClassMember_AsOf_2017Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,000 | ||||||||||||||||
| C000183136_ClassMember_AsOf_2018Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,900 | ||||||||||||||||
| C000183136_ClassMember_AsOf_2019Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,518 | ||||||||||||||||
| C000183136_ClassMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 13,483 | ||||||||||||||||
| C000183136_ClassMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 14,829 | ||||||||||||||||
| C000183136_ClassMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 21,923 | ||||||||||||||||
| C000183136_ClassMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 17,848 | ||||||||||||||||
| C000183136_ClassMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 20,075 | $ 20,075 | 20,075 | $ 20,075 | 20,075 | $ 20,075 | 20,075 | ||||||||||
| C000183136_LG_1_AdditionalIndexMember_8YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | MSCI USA ESG Leaders Index</span>" id="sjs-E818"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">MSCI USA ESG Leaders Index</span> | ||||||||||||||||
| C000183136_1_AdditionalIndexMember_AsOf_2017Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,000 | ||||||||||||||||
| C000183136_1_AdditionalIndexMember_AsOf_2018Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,904 | ||||||||||||||||
| C000183136_1_AdditionalIndexMember_AsOf_2019Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,542 | ||||||||||||||||
| C000183136_1_AdditionalIndexMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 13,531 | ||||||||||||||||
| C000183136_1_AdditionalIndexMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 14,897 | ||||||||||||||||
| C000183136_1_AdditionalIndexMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 22,049 | ||||||||||||||||
| C000183136_1_AdditionalIndexMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 17,970 | ||||||||||||||||
| C000183136_1_AdditionalIndexMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 20,235 | 20,235 | 20,235 | $ 20,235 | 20,235 | 20,235 | 20,235 | ||||||||||
| C000183136_LG_2_AdditionalIndexMember_8YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | MSCI USA Index</span>" id="sjs-E845"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">MSCI USA Index</span> | ||||||||||||||||
| C000183136_2_AdditionalIndexMember_AsOf_2017Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,000 | ||||||||||||||||
| C000183136_2_AdditionalIndexMember_AsOf_2018Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,813 | ||||||||||||||||
| C000183136_2_AdditionalIndexMember_AsOf_2019Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,530 | ||||||||||||||||
| C000183136_2_AdditionalIndexMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 13,106 | ||||||||||||||||
| C000183136_2_AdditionalIndexMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 14,543 | ||||||||||||||||
| C000183136_2_AdditionalIndexMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 20,758 | ||||||||||||||||
| C000183136_2_AdditionalIndexMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 17,257 | ||||||||||||||||
| C000183136_2_AdditionalIndexMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 18,905 | $ 18,905 | 18,905 | $ 18,905 | 18,905 | 18,905 | 18,905 | ||||||||||
| C000183136_NoLoadClassMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 38.21% | ||||||||||||||||
| C000183136_NoLoadClassMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 15.53% | ||||||||||||||||
| C000183136_NoLoadClassMember_2023-11-01_2024-10-31Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 14.61% | ||||||||||||||||
| C000183136_0_AdditionalIndexMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 38.49% | ||||||||||||||||
| C000183136_0_AdditionalIndexMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 15.67% | ||||||||||||||||
| C000183136_0_AdditionalIndexMember_LOCMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 14.76% | ||||||||||||||||
| C000218748_LG_ClassMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | Fidelity® SAI International Quality Index Fund</span>" id="sjs-C890"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Fidelity® SAI International Quality Index Fund</span> | ||||||||||||||||
| C000218748_ClassMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,000 | ||||||||||||||||
| C000218748_ClassMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,070 | ||||||||||||||||
| C000218748_ClassMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 14,644 | ||||||||||||||||
| C000218748_ClassMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,138 | ||||||||||||||||
| C000218748_ClassMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 12,600 | $ 12,600 | 12,600 | 12,600 | 12,600 | 12,600 | 12,600 | ||||||||||
| C000218748_LG_1_AdditionalIndexMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | Fidelity International Quality Focus Index℠</span>" id="sjs-C908"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Fidelity International Quality Focus Index℠</span> | ||||||||||||||||
| C000218748_1_AdditionalIndexMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,000 | ||||||||||||||||
| C000218748_1_AdditionalIndexMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,074 | ||||||||||||||||
| C000218748_1_AdditionalIndexMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 14,711 | ||||||||||||||||
| C000218748_1_AdditionalIndexMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,236 | ||||||||||||||||
| C000218748_1_AdditionalIndexMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 12,665 | $ 12,665 | 12,665 | 12,665 | 12,665 | 12,665 | 12,665 | ||||||||||
| C000218748_LG_2_AdditionalIndexMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | MSCI ACWI (All Country World Index) ex USA Index</span>" id="sjs-C926"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">MSCI ACWI (All Country World Index) ex USA Index</span> | ||||||||||||||||
| C000218748_2_AdditionalIndexMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,000 | ||||||||||||||||
| C000218748_2_AdditionalIndexMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,310 | ||||||||||||||||
| C000218748_2_AdditionalIndexMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 14,687 | ||||||||||||||||
| C000218748_2_AdditionalIndexMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,073 | ||||||||||||||||
| C000218748_2_AdditionalIndexMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 12,432 | $ 12,432 | 12,432 | 12,432 | $ 12,432 | 12,432 | 12,432 | ||||||||||
| C000218748_NoLoadClassMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 21.81% | ||||||||||||||||
| C000218748_NoLoadClassMember_2023-11-01_2024-10-31Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 10.05% | ||||||||||||||||
| C000218748_0_AdditionalIndexMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 22.97% | ||||||||||||||||
| C000218748_0_AdditionalIndexMember_LOCMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 10.41% | ||||||||||||||||
| C000163541_LG_ClassMember_9YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | Fidelity® SAI Emerging Markets Index Fund</span>" id="sjs-F956"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Fidelity® SAI Emerging Markets Index Fund</span> | ||||||||||||||||
| C000163541_ClassMember_AsOf_2016Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,000 | ||||||||||||||||
| C000163541_ClassMember_AsOf_2017Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,940 | ||||||||||||||||
| C000163541_ClassMember_AsOf_2018Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 15,074 | ||||||||||||||||
| C000163541_ClassMember_AsOf_2019Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 13,173 | ||||||||||||||||
| C000163541_ClassMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 14,680 | ||||||||||||||||
| C000163541_ClassMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 15,882 | ||||||||||||||||
| C000163541_ClassMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 18,403 | ||||||||||||||||
| C000163541_ClassMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 12,718 | ||||||||||||||||
| C000163541_ClassMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 14,063 | 14,063 | 14,063 | 14,063 | $ 14,063 | 14,063 | 14,063 | ||||||||||
| C000163541_LG_1_AdditionalIndexMember_9YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | MSCI Emerging Markets Index</span>" id="sjs-F986"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">MSCI Emerging Markets Index</span> | ||||||||||||||||
| C000163541_1_AdditionalIndexMember_AsOf_2016Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,000 | ||||||||||||||||
| C000163541_1_AdditionalIndexMember_AsOf_2017Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 12,019 | ||||||||||||||||
| C000163541_1_AdditionalIndexMember_AsOf_2018Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 15,204 | ||||||||||||||||
| C000163541_1_AdditionalIndexMember_AsOf_2019Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 13,306 | ||||||||||||||||
| C000163541_1_AdditionalIndexMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 14,888 | ||||||||||||||||
| C000163541_1_AdditionalIndexMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 16,119 | ||||||||||||||||
| C000163541_1_AdditionalIndexMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 18,856 | ||||||||||||||||
| C000163541_1_AdditionalIndexMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 13,008 | ||||||||||||||||
| C000163541_1_AdditionalIndexMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 14,418 | $ 14,418 | 14,418 | 14,418 | $ 14,418 | 14,418 | 14,418 | ||||||||||
| C000163541_NoLoadClassMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 23.48% | ||||||||||||||||
| C000163541_NoLoadClassMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 3.42% | ||||||||||||||||
| C000163541_NoLoadClassMember_2023-11-01_2024-10-31Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 6.45% | ||||||||||||||||
| C000218747_LG_ClassMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | Fidelity® SAI International Momentum Index Fund</span>" id="sjs-C1025"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Fidelity® SAI International Momentum Index Fund</span> | ||||||||||||||||
| C000218747_ClassMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,000 | ||||||||||||||||
| C000218747_ClassMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,330 | ||||||||||||||||
| C000218747_ClassMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 14,679 | ||||||||||||||||
| C000218747_ClassMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,665 | ||||||||||||||||
| C000218747_ClassMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 12,428 | $ 12,428 | 12,428 | 12,428 | 12,428 | 12,428 | 12,428 | ||||||||||
| C000218747_LG_1_AdditionalIndexMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | Fidelity International Momentum Focus Index℠</span>" id="sjs-C1043"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Fidelity International Momentum Focus Index℠</span> | ||||||||||||||||
| C000218747_1_AdditionalIndexMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,000 | ||||||||||||||||
| C000218747_1_AdditionalIndexMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,342 | ||||||||||||||||
| C000218747_1_AdditionalIndexMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 14,753 | ||||||||||||||||
| C000218747_1_AdditionalIndexMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,780 | ||||||||||||||||
| C000218747_1_AdditionalIndexMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 12,499 | $ 12,499 | 12,499 | 12,499 | 12,499 | 12,499 | 12,499 | ||||||||||
| C000218747_LG_2_AdditionalIndexMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | MSCI ACWI (All Country World Index) ex USA Index</span>" id="sjs-C1061"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">MSCI ACWI (All Country World Index) ex USA Index</span> | ||||||||||||||||
| C000218747_2_AdditionalIndexMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,000 | ||||||||||||||||
| C000218747_2_AdditionalIndexMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,310 | ||||||||||||||||
| C000218747_2_AdditionalIndexMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 14,687 | ||||||||||||||||
| C000218747_2_AdditionalIndexMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,073 | ||||||||||||||||
| C000218747_2_AdditionalIndexMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 12,432 | $ 12,432 | 12,432 | $ 12,432 | 12,432 | 12,432 | 12,432 | ||||||||||
| C000218747_NoLoadClassMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 27.42% | ||||||||||||||||
| C000218747_NoLoadClassMember_2023-11-01_2024-10-31Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 10.82% | ||||||||||||||||
| C000218747_0_AdditionalIndexMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 28.90% | ||||||||||||||||
| C000218747_0_AdditionalIndexMember_LOCMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 11.25% | ||||||||||||||||
| C000195573_LG_ClassMember_8YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | Fidelity® SAI International Value Index Fund</span>" id="sjs-E1091"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Fidelity® SAI International Value Index Fund</span> | ||||||||||||||||
| C000195573_ClassMember_AsOf_2017Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,000 | ||||||||||||||||
| C000195573_ClassMember_AsOf_2018Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 8,936 | ||||||||||||||||
| C000195573_ClassMember_AsOf_2019Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 9,394 | ||||||||||||||||
| C000195573_ClassMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 7,575 | ||||||||||||||||
| C000195573_ClassMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,781 | ||||||||||||||||
| C000195573_ClassMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 8,956 | ||||||||||||||||
| C000195573_ClassMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,770 | ||||||||||||||||
| C000195573_ClassMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 12,961 | 12,961 | 12,961 | $ 12,961 | 12,961 | 12,961 | 12,961 | ||||||||||
| C000195573_LG_1_AdditionalIndexMember_8YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | Fidelity International Value Focus Index℠</span>" id="sjs-E1118"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Fidelity International Value Focus Index℠</span> | ||||||||||||||||
| C000195573_1_AdditionalIndexMember_AsOf_2017Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,000 | ||||||||||||||||
| C000195573_1_AdditionalIndexMember_AsOf_2018Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 9,030 | ||||||||||||||||
| C000195573_1_AdditionalIndexMember_AsOf_2019Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 9,524 | ||||||||||||||||
| C000195573_1_AdditionalIndexMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 7,670 | ||||||||||||||||
| C000195573_1_AdditionalIndexMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,972 | ||||||||||||||||
| C000195573_1_AdditionalIndexMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 9,158 | ||||||||||||||||
| C000195573_1_AdditionalIndexMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,962 | ||||||||||||||||
| C000195573_1_AdditionalIndexMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 13,288 | 13,288 | 13,288 | $ 13,288 | 13,288 | 13,288 | 13,288 | ||||||||||
| C000195573_LG_2_AdditionalIndexMember_8YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | MSCI ACWI (All Country World Index) ex USA Index</span>" id="sjs-E1145"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">MSCI ACWI (All Country World Index) ex USA Index</span> | ||||||||||||||||
| C000195573_2_AdditionalIndexMember_AsOf_2017Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,000 | ||||||||||||||||
| C000195573_2_AdditionalIndexMember_AsOf_2018Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 9,061 | ||||||||||||||||
| C000195573_2_AdditionalIndexMember_AsOf_2019Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,101 | ||||||||||||||||
| C000195573_2_AdditionalIndexMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 9,852 | ||||||||||||||||
| C000195573_2_AdditionalIndexMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 12,794 | ||||||||||||||||
| C000195573_2_AdditionalIndexMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 9,645 | ||||||||||||||||
| C000195573_2_AdditionalIndexMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,829 | ||||||||||||||||
| C000195573_2_AdditionalIndexMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 13,487 | $ 13,487 | 13,487 | $ 13,487 | $ 13,487 | 13,487 | 13,487 | ||||||||||
| C000195573_NoLoadClassMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 20.34% | ||||||||||||||||
| C000195573_NoLoadClassMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 6.65% | ||||||||||||||||
| C000195573_NoLoadClassMember_2023-11-01_2024-10-31Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 3.85% | ||||||||||||||||
| C000195573_0_AdditionalIndexMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 21.22% | ||||||||||||||||
| C000195573_0_AdditionalIndexMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 6.89% | ||||||||||||||||
| C000195573_0_AdditionalIndexMember_LOCMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 4.22% | ||||||||||||||||
| C000163542_LG_ClassMember_9YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | Fidelity® SAI International Index Fund</span>" id="sjs-F1190"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Fidelity® SAI International Index Fund</span> | ||||||||||||||||
| C000163542_ClassMember_AsOf_2016Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,000 | ||||||||||||||||
| C000163542_ClassMember_AsOf_2017Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,190 | ||||||||||||||||
| C000163542_ClassMember_AsOf_2018Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 12,576 | ||||||||||||||||
| C000163542_ClassMember_AsOf_2019Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,677 | ||||||||||||||||
| C000163542_ClassMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 13,004 | ||||||||||||||||
| C000163542_ClassMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 12,158 | ||||||||||||||||
| C000163542_ClassMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 16,303 | ||||||||||||||||
| C000163542_ClassMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 12,554 | ||||||||||||||||
| C000163542_ClassMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 14,491 | $ 14,491 | 14,491 | 14,491 | $ 14,491 | 14,491 | 14,491 | ||||||||||
| C000163542_LG_1_AdditionalIndexMember_9YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | MSCI EAFE Index</span>" id="sjs-F1220"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">MSCI EAFE Index</span> | ||||||||||||||||
| C000163542_1_AdditionalIndexMember_AsOf_2016Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,000 | ||||||||||||||||
| C000163542_1_AdditionalIndexMember_AsOf_2017Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,280 | ||||||||||||||||
| C000163542_1_AdditionalIndexMember_AsOf_2018Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 12,715 | ||||||||||||||||
| C000163542_1_AdditionalIndexMember_AsOf_2019Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,870 | ||||||||||||||||
| C000163542_1_AdditionalIndexMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 13,211 | ||||||||||||||||
| C000163542_1_AdditionalIndexMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 12,328 | ||||||||||||||||
| C000163542_1_AdditionalIndexMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 16,574 | ||||||||||||||||
| C000163542_1_AdditionalIndexMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 12,788 | ||||||||||||||||
| C000163542_1_AdditionalIndexMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 14,662 | $ 14,662 | 14,662 | 14,662 | $ 14,662 | 14,662 | $ 14,662 | ||||||||||
| C000163542_NoLoadClassMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 22.26% | ||||||||||||||||
| C000163542_NoLoadClassMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 6.38% | ||||||||||||||||
| C000163542_NoLoadClassMember_2023-11-01_2024-10-31Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 6.69% | ||||||||||||||||
| C000079292_LG_ClassMember_11YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | Fidelity® Series Global ex U.S. Index Fund</span>" id="sjs-H1259"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Fidelity® Series Global ex U.S. Index Fund</span> | ||||||||||||||||
| C000079292_ClassMember_AsOf_2014Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,000 | ||||||||||||||||
| C000079292_ClassMember_AsOf_2015Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 9,447 | ||||||||||||||||
| C000079292_ClassMember_AsOf_2016Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 9,514 | ||||||||||||||||
| C000079292_ClassMember_AsOf_2017Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,782 | ||||||||||||||||
| C000079292_ClassMember_AsOf_2018Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,783 | ||||||||||||||||
| C000079292_ClassMember_AsOf_2019Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 12,008 | ||||||||||||||||
| C000079292_ClassMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,736 | ||||||||||||||||
| C000079292_ClassMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 15,179 | ||||||||||||||||
| C000079292_ClassMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,449 | ||||||||||||||||
| C000079292_ClassMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 12,894 | ||||||||||||||||
| C000079292_ClassMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 15,937 | $ 15,937 | 15,937 | 15,937 | 15,937 | 15,937 | $ 15,937 | ||||||||||
| C000079292_LG_1_AdditionalIndexMember_11YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | MSCI ACWI (All Country World Index) ex USA Index</span>" id="sjs-H1295"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">MSCI ACWI (All Country World Index) ex USA Index</span> | ||||||||||||||||
| C000079292_1_AdditionalIndexMember_AsOf_2014Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 10,000 | ||||||||||||||||
| C000079292_1_AdditionalIndexMember_AsOf_2015Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 9,545 | ||||||||||||||||
| C000079292_1_AdditionalIndexMember_AsOf_2016Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 9,583 | ||||||||||||||||
| C000079292_1_AdditionalIndexMember_AsOf_2017Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,868 | ||||||||||||||||
| C000079292_1_AdditionalIndexMember_AsOf_2018Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,910 | ||||||||||||||||
| C000079292_1_AdditionalIndexMember_AsOf_2019Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 12,161 | ||||||||||||||||
| C000079292_1_AdditionalIndexMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,862 | ||||||||||||||||
| C000079292_1_AdditionalIndexMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 15,403 | ||||||||||||||||
| C000079292_1_AdditionalIndexMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,613 | ||||||||||||||||
| C000079292_1_AdditionalIndexMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 13,038 | ||||||||||||||||
| C000079292_1_AdditionalIndexMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 16,238 | $ 16,238 | 16,238 | 16,238 | 16,238 | $ 16,238 | $ 16,238 | ||||||||||
| C000079292_NoLoadClassMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 23.60% | ||||||||||||||||
| C000079292_NoLoadClassMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 5.83% | ||||||||||||||||
| C000079292_NoLoadClassMember_10YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 4.77% | ||||||||||||||||
| C000155835_LG_ClassMember_10YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | Fidelity® SAI International Low Volatility Index Fund</span>" id="sjs-G1340"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Fidelity® SAI International Low Volatility Index Fund</span> | ||||||||||||||||
| C000155835_ClassMember_AsOf_2015Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,000 | ||||||||||||||||
| C000155835_ClassMember_AsOf_2016Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 9,610 | ||||||||||||||||
| C000155835_ClassMember_AsOf_2017Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 9,874 | ||||||||||||||||
| C000155835_ClassMember_AsOf_2018Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,272 | ||||||||||||||||
| C000155835_ClassMember_AsOf_2019Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,106 | ||||||||||||||||
| C000155835_ClassMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 12,538 | ||||||||||||||||
| C000155835_ClassMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,120 | ||||||||||||||||
| C000155835_ClassMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 13,643 | ||||||||||||||||
| C000155835_ClassMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,941 | ||||||||||||||||
| C000155835_ClassMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 12,371 | $ 12,371 | 12,371 | 12,371 | 12,371 | $ 12,371 | 12,371 | ||||||||||
| C000155835_LG_1_AdditionalIndexMember_10YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | Fidelity SAI International Low Volatility Index Fund Linked Index℠</span>" id="sjs-G1373"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Fidelity SAI International Low Volatility Index Fund Linked Index℠</span> | ||||||||||||||||
| C000155835_1_AdditionalIndexMember_AsOf_2015Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,000 | ||||||||||||||||
| C000155835_1_AdditionalIndexMember_AsOf_2016Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 9,703 | ||||||||||||||||
| C000155835_1_AdditionalIndexMember_AsOf_2017Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 9,922 | ||||||||||||||||
| C000155835_1_AdditionalIndexMember_AsOf_2018Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,376 | ||||||||||||||||
| C000155835_1_AdditionalIndexMember_AsOf_2019Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,234 | ||||||||||||||||
| C000155835_1_AdditionalIndexMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 12,745 | ||||||||||||||||
| C000155835_1_AdditionalIndexMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,318 | ||||||||||||||||
| C000155835_1_AdditionalIndexMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 13,908 | ||||||||||||||||
| C000155835_1_AdditionalIndexMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,204 | ||||||||||||||||
| C000155835_1_AdditionalIndexMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 12,606 | 12,606 | 12,606 | 12,606 | 12,606 | $ 12,606 | 12,606 | ||||||||||
| C000155835_LG_2_AdditionalIndexMember_10YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | Fidelity International Low Volatility Focus Index℠</span>" id="sjs-G1406"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Fidelity International Low Volatility Focus Index℠</span> | ||||||||||||||||
| C000155835_2_AdditionalIndexMember_AsOf_2015Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,000 | ||||||||||||||||
| C000155835_2_AdditionalIndexMember_AsOf_2016Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 9,610 | ||||||||||||||||
| C000155835_2_AdditionalIndexMember_AsOf_2017Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 9,874 | ||||||||||||||||
| C000155835_2_AdditionalIndexMember_AsOf_2018Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,272 | ||||||||||||||||
| C000155835_2_AdditionalIndexMember_AsOf_2019Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,106 | ||||||||||||||||
| C000155835_2_AdditionalIndexMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 12,686 | ||||||||||||||||
| C000155835_2_AdditionalIndexMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,265 | ||||||||||||||||
| C000155835_2_AdditionalIndexMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 13,843 | ||||||||||||||||
| C000155835_2_AdditionalIndexMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,152 | ||||||||||||||||
| C000155835_2_AdditionalIndexMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 12,548 | $ 12,548 | 12,548 | 12,548 | 12,548 | $ 12,548 | 12,548 | ||||||||||
| C000155835_NoLoadClassMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 16.34% | ||||||||||||||||
| C000155835_NoLoadClassMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 2.80% | ||||||||||||||||
| C000155835_NoLoadClassMember_2023-11-01_2024-10-31Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 3.94% | ||||||||||||||||
| C000155835_0_AdditionalIndexMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 17.05% | ||||||||||||||||
| C000155835_0_AdditionalIndexMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 2.97% | ||||||||||||||||
| C000155835_0_AdditionalIndexMember_LOCMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 4.22% | ||||||||||||||||
| C000155835_1_AdditionalIndexMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 17.05% | ||||||||||||||||
| C000155835_1_AdditionalIndexMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 2.97% | ||||||||||||||||
| C000155835_1_AdditionalIndexMember_LOCMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | |||||||||||||||||
| C000155834_LG_ClassMember_10YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | Fidelity® SAI U.S. Low Volatility Index Fund</span>" id="sjs-G1466"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Fidelity® SAI U.S. Low Volatility Index Fund</span> | ||||||||||||||||
| C000155834_ClassMember_AsOf_2015Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,000 | ||||||||||||||||
| C000155834_ClassMember_AsOf_2016Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,220 | ||||||||||||||||
| C000155834_ClassMember_AsOf_2017Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,993 | ||||||||||||||||
| C000155834_ClassMember_AsOf_2018Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 13,038 | ||||||||||||||||
| C000155834_ClassMember_AsOf_2019Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 14,184 | ||||||||||||||||
| C000155834_ClassMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 16,684 | ||||||||||||||||
| C000155834_ClassMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 17,044 | ||||||||||||||||
| C000155834_ClassMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 22,369 | ||||||||||||||||
| C000155834_ClassMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 20,492 | ||||||||||||||||
| C000155834_ClassMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 21,801 | $ 21,801 | 21,801 | 21,801 | 21,801 | $ 21,801 | 21,801 | ||||||||||
| C000155834_LG_1_AdditionalIndexMember_10YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | Fidelity SAI U.S. Low Volatility Index Fund Linked Index℠</span>" id="sjs-G1499"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Fidelity SAI U.S. Low Volatility Index Fund Linked Index℠</span> | ||||||||||||||||
| C000155834_1_AdditionalIndexMember_AsOf_2015Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,000 | ||||||||||||||||
| C000155834_1_AdditionalIndexMember_AsOf_2016Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 10,235 | ||||||||||||||||
| C000155834_1_AdditionalIndexMember_AsOf_2017Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 11,023 | ||||||||||||||||
| C000155834_1_AdditionalIndexMember_AsOf_2018Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 13,098 | ||||||||||||||||
| C000155834_1_AdditionalIndexMember_AsOf_2019Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 14,264 | ||||||||||||||||
| C000155834_1_AdditionalIndexMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 16,795 | ||||||||||||||||
| C000155834_1_AdditionalIndexMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 17,177 | ||||||||||||||||
| C000155834_1_AdditionalIndexMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 22,550 | ||||||||||||||||
| C000155834_1_AdditionalIndexMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 20,677 | ||||||||||||||||
| C000155834_1_AdditionalIndexMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | 22,013 | 22,013 | 22,013 | 22,013 | 22,013 | $ 22,013 | 22,013 | ||||||||||
| C000155834_LG_2_AdditionalIndexMember_10YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Line Graph and Table Measure Name | Fidelity U.S. Low Volatility Focus Index℠</span>" id="sjs-G1532"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Fidelity U.S. Low Volatility Focus Index℠</span> | ||||||||||||||||
| C000155834_2_AdditionalIndexMember_AsOf_2015Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 10,000 | ||||||||||||||||
| C000155834_2_AdditionalIndexMember_AsOf_2016Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 10,220 | ||||||||||||||||
| C000155834_2_AdditionalIndexMember_AsOf_2017Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 10,993 | ||||||||||||||||
| C000155834_2_AdditionalIndexMember_AsOf_2018Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 13,038 | ||||||||||||||||
| C000155834_2_AdditionalIndexMember_AsOf_2019Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 14,184 | ||||||||||||||||
| C000155834_2_AdditionalIndexMember_AsOf_2020Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 16,549 | ||||||||||||||||
| C000155834_2_AdditionalIndexMember_AsOf_2021Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 16,927 | ||||||||||||||||
| C000155834_2_AdditionalIndexMember_AsOf_2022Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 22,221 | ||||||||||||||||
| C000155834_2_AdditionalIndexMember_AsOf_2023Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 20,375 | ||||||||||||||||
| C000155834_2_AdditionalIndexMember_AsOf_2024Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Account Value | $ 21,692 | $ 21,692 | $ 21,692 | $ 21,692 | $ 21,692 | $ 21,692 | $ 21,692 | ||||||||||
| C000155834_NoLoadClassMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 29.21% | ||||||||||||||||
| C000155834_NoLoadClassMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 11.04% | ||||||||||||||||
| C000155834_NoLoadClassMember_2023-11-01_2024-10-31Member | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 11.63% | ||||||||||||||||
| C000155834_0_AdditionalIndexMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 29.39% | ||||||||||||||||
| C000155834_0_AdditionalIndexMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 11.14% | ||||||||||||||||
| C000155834_0_AdditionalIndexMember_LOCMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 11.76% | ||||||||||||||||
| C000155834_1_AdditionalIndexMember_1YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 29.39% | ||||||||||||||||
| C000155834_1_AdditionalIndexMember_5YRMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent | 11.14% | ||||||||||||||||
| C000155834_1_AdditionalIndexMember_LOCMember | |||||||||||||||||
| Account Value [Line Items] | |||||||||||||||||
| Average Annual Return, Percent |
| Shareholder Report, Holdings (Details) | Oct. 31, 2024 |
| Fidelity SAI Emerging Markets Low Volatility Index Fund | TH0Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.80% |
| Fidelity SAI Emerging Markets Low Volatility Index Fund | TH1Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.70% |
| Fidelity SAI Emerging Markets Low Volatility Index Fund | TH2Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.70% |
| Fidelity SAI Emerging Markets Low Volatility Index Fund | TH3Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.70% |
| Fidelity SAI Emerging Markets Low Volatility Index Fund | TH4Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.70% |
| Fidelity SAI Emerging Markets Low Volatility Index Fund | TH5Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.60% |
| Fidelity SAI Emerging Markets Low Volatility Index Fund | TH6Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.60% |
| Fidelity SAI Emerging Markets Low Volatility Index Fund | TH7Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.60% |
| Fidelity SAI Emerging Markets Low Volatility Index Fund | TH8Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.60% |
| Fidelity SAI Emerging Markets Low Volatility Index Fund | TH9Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.60% |
| Fidelity SAI Emerging Markets Low Volatility Index Fund | MSFinancialsSectorMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 27.60% |
| Fidelity SAI Emerging Markets Low Volatility Index Fund | Information Technology Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 20.10% |
| Fidelity SAI Emerging Markets Low Volatility Index Fund | Healthcare Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.30% |
| Fidelity SAI Emerging Markets Low Volatility Index Fund | Real Estate Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.40% |
| Fidelity SAI Emerging Markets Low Volatility Index Fund | Industrial Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.20% |
| Fidelity SAI Emerging Markets Low Volatility Index Fund | Materials Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.20% |
| Fidelity SAI Emerging Markets Low Volatility Index Fund | Consumer Discretionary Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 7.80% |
| Fidelity SAI Emerging Markets Low Volatility Index Fund | Consumer Staples Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 9.40% |
| Fidelity SAI Emerging Markets Low Volatility Index Fund | Communications Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.60% |
| Fidelity SAI Emerging Markets Low Volatility Index Fund | Energy Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.90% |
| Fidelity SAI Emerging Markets Low Volatility Index Fund | Utilities Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.20% |
| Fidelity SAI Emerging Markets Low Volatility Index Fund | Taiwan | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 25% |
| Fidelity SAI Emerging Markets Low Volatility Index Fund | India | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 21.50% |
| Fidelity SAI Emerging Markets Low Volatility Index Fund | China | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 15% |
| Fidelity SAI Emerging Markets Low Volatility Index Fund | Saudi Arabia | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 7.80% |
| Fidelity SAI Emerging Markets Low Volatility Index Fund | Korea, Republic of | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 7.60% |
| Fidelity SAI Emerging Markets Low Volatility Index Fund | Malaysia | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.90% |
| Fidelity SAI Emerging Markets Low Volatility Index Fund | United Arab Emirates | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.10% |
| Fidelity SAI Emerging Markets Low Volatility Index Fund | Qatar | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.60% |
| Fidelity SAI Emerging Markets Low Volatility Index Fund | Thailand | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.30% |
| Fidelity SAI Emerging Markets Low Volatility Index Fund | OtherMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 9.20% |
| Fidelity SAI Emerging Markets Low Volatility Index Fund | AACommonStocksMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 98.70% |
| Fidelity SAI Emerging Markets Low Volatility Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.30% |
| Fidelity SAI Emerging Markets Value Index Fund | TH0Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 9% |
| Fidelity SAI Emerging Markets Value Index Fund | TH1Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.20% |
| Fidelity SAI Emerging Markets Value Index Fund | TH2Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.40% |
| Fidelity SAI Emerging Markets Value Index Fund | TH3Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.30% |
| Fidelity SAI Emerging Markets Value Index Fund | TH4Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.20% |
| Fidelity SAI Emerging Markets Value Index Fund | TH5Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.10% |
| Fidelity SAI Emerging Markets Value Index Fund | TH6Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.60% |
| Fidelity SAI Emerging Markets Value Index Fund | TH7Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.60% |
| Fidelity SAI Emerging Markets Value Index Fund | TH8Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.50% |
| Fidelity SAI Emerging Markets Value Index Fund | TH9Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.50% |
| Fidelity SAI Emerging Markets Value Index Fund | MSFinancialsSectorMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 24.20% |
| Fidelity SAI Emerging Markets Value Index Fund | Information Technology Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 24.20% |
| Fidelity SAI Emerging Markets Value Index Fund | Healthcare Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.10% |
| Fidelity SAI Emerging Markets Value Index Fund | Real Estate Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.80% |
| Fidelity SAI Emerging Markets Value Index Fund | Industrial Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.90% |
| Fidelity SAI Emerging Markets Value Index Fund | Materials Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.40% |
| Fidelity SAI Emerging Markets Value Index Fund | Consumer Discretionary Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13% |
| Fidelity SAI Emerging Markets Value Index Fund | Consumer Staples Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.40% |
| Fidelity SAI Emerging Markets Value Index Fund | Communications Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 8.80% |
| Fidelity SAI Emerging Markets Value Index Fund | Energy Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.30% |
| Fidelity SAI Emerging Markets Value Index Fund | Utilities Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.80% |
| Fidelity SAI Emerging Markets Value Index Fund | Taiwan | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 20.60% |
| Fidelity SAI Emerging Markets Value Index Fund | India | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 21.60% |
| Fidelity SAI Emerging Markets Value Index Fund | China | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 22.30% |
| Fidelity SAI Emerging Markets Value Index Fund | Saudi Arabia | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.10% |
| Fidelity SAI Emerging Markets Value Index Fund | Korea, Republic of | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.50% |
| Fidelity SAI Emerging Markets Value Index Fund | Malaysia | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.60% |
| Fidelity SAI Emerging Markets Value Index Fund | OtherMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.90% |
| Fidelity SAI Emerging Markets Value Index Fund | Brazil | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.70% |
| Fidelity SAI Emerging Markets Value Index Fund | South Africa | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.10% |
| Fidelity SAI Emerging Markets Value Index Fund | Indonesia | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.60% |
| Fidelity SAI Emerging Markets Value Index Fund | AACommonStocksMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 98.90% |
| Fidelity SAI Emerging Markets Value Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.10% |
| Fidelity SAI Emerging Markets Value Index Fund | AAPreferredStocksMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0% |
| Fidelity Flex International Index Fund | TH0Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3% |
| Fidelity Flex International Index Fund | TH1Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.40% |
| Fidelity Flex International Index Fund | TH2Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.30% |
| Fidelity Flex International Index Fund | TH3Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.10% |
| Fidelity Flex International Index Fund | TH4Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1% |
| Fidelity Flex International Index Fund | TH5Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.90% |
| Fidelity Flex International Index Fund | TH6Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.90% |
| Fidelity Flex International Index Fund | TH7Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.90% |
| Fidelity Flex International Index Fund | TH8Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.80% |
| Fidelity Flex International Index Fund | TH9Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.80% |
| Fidelity Flex International Index Fund | MSFinancialsSectorMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 23.80% |
| Fidelity Flex International Index Fund | Information Technology Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 12.80% |
| Fidelity Flex International Index Fund | Healthcare Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 9% |
| Fidelity Flex International Index Fund | Real Estate Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.60% |
| Fidelity Flex International Index Fund | Industrial Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.40% |
| Fidelity Flex International Index Fund | Materials Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.60% |
| Fidelity Flex International Index Fund | Consumer Discretionary Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.80% |
| Fidelity Flex International Index Fund | Consumer Staples Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.80% |
| Fidelity Flex International Index Fund | Communications Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5% |
| Fidelity Flex International Index Fund | Energy Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.90% |
| Fidelity Flex International Index Fund | Utilities Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3% |
| Fidelity Flex International Index Fund | Taiwan | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.40% |
| Fidelity Flex International Index Fund | India | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.50% |
| Fidelity Flex International Index Fund | China | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 8.30% |
| Fidelity Flex International Index Fund | OtherMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 33.50% |
| Fidelity Flex International Index Fund | Japan | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.70% |
| Fidelity Flex International Index Fund | United States | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 8% |
| Fidelity Flex International Index Fund | Canada | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 7.50% |
| Fidelity Flex International Index Fund | United Kingdom | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.70% |
| Fidelity Flex International Index Fund | France | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.80% |
| Fidelity Flex International Index Fund | Germany | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.60% |
| Fidelity Flex International Index Fund | AACommonStocksMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 97.30% |
| Fidelity Flex International Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.30% |
| Fidelity Flex International Index Fund | AAPreferredStocksMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.40% |
| Fidelity International Sustainability Index Fund | TH0Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.60% |
| Fidelity International Sustainability Index Fund | TH1Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.60% |
| Fidelity International Sustainability Index Fund | TH2Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.40% |
| Fidelity International Sustainability Index Fund | TH3Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.90% |
| Fidelity International Sustainability Index Fund | TH4Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.70% |
| Fidelity International Sustainability Index Fund | TH5Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.60% |
| Fidelity International Sustainability Index Fund | TH6Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.40% |
| Fidelity International Sustainability Index Fund | TH7Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.40% |
| Fidelity International Sustainability Index Fund | TH8Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.30% |
| Fidelity International Sustainability Index Fund | TH9Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.10% |
| Fidelity International Sustainability Index Fund | MSFinancialsSectorMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 22.70% |
| Fidelity International Sustainability Index Fund | Information Technology Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 12.80% |
| Fidelity International Sustainability Index Fund | Healthcare Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 9.80% |
| Fidelity International Sustainability Index Fund | Real Estate Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.70% |
| Fidelity International Sustainability Index Fund | Industrial Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.50% |
| Fidelity International Sustainability Index Fund | Materials Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.40% |
| Fidelity International Sustainability Index Fund | Consumer Discretionary Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 11.10% |
| Fidelity International Sustainability Index Fund | Consumer Staples Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.90% |
| Fidelity International Sustainability Index Fund | Communications Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 7.30% |
| Fidelity International Sustainability Index Fund | Energy Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4% |
| Fidelity International Sustainability Index Fund | Utilities Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.70% |
| Fidelity International Sustainability Index Fund | Taiwan | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 8.10% |
| Fidelity International Sustainability Index Fund | India | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.10% |
| Fidelity International Sustainability Index Fund | China | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 9.30% |
| Fidelity International Sustainability Index Fund | OtherMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 31.40% |
| Fidelity International Sustainability Index Fund | Japan | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 15% |
| Fidelity International Sustainability Index Fund | Canada | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 7.80% |
| Fidelity International Sustainability Index Fund | United Kingdom | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 8.40% |
| Fidelity International Sustainability Index Fund | France | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.90% |
| Fidelity International Sustainability Index Fund | Switzerland | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.30% |
| Fidelity International Sustainability Index Fund | Denmark | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.70% |
| Fidelity International Sustainability Index Fund | AACommonStocksMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 98.70% |
| Fidelity International Sustainability Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.10% |
| Fidelity International Sustainability Index Fund | AAPreferredStocksMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.20% |
| Fidelity Global ex U.S. Index Fund | TH0Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.90% |
| Fidelity Global ex U.S. Index Fund | TH1Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.40% |
| Fidelity Global ex U.S. Index Fund | TH2Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.30% |
| Fidelity Global ex U.S. Index Fund | TH3Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.10% |
| Fidelity Global ex U.S. Index Fund | TH4Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1% |
| Fidelity Global ex U.S. Index Fund | TH5Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.90% |
| Fidelity Global ex U.S. Index Fund | TH6Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.90% |
| Fidelity Global ex U.S. Index Fund | TH7Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.80% |
| Fidelity Global ex U.S. Index Fund | TH8Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.80% |
| Fidelity Global ex U.S. Index Fund | TH9Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.80% |
| Fidelity Global ex U.S. Index Fund | MSFinancialsSectorMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 23.70% |
| Fidelity Global ex U.S. Index Fund | Information Technology Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 12.80% |
| Fidelity Global ex U.S. Index Fund | Healthcare Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 8.90% |
| Fidelity Global ex U.S. Index Fund | Real Estate Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.70% |
| Fidelity Global ex U.S. Index Fund | Industrial Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.40% |
| Fidelity Global ex U.S. Index Fund | Materials Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.60% |
| Fidelity Global ex U.S. Index Fund | Consumer Discretionary Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.70% |
| Fidelity Global ex U.S. Index Fund | Consumer Staples Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.80% |
| Fidelity Global ex U.S. Index Fund | Communications Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.90% |
| Fidelity Global ex U.S. Index Fund | Energy Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.70% |
| Fidelity Global ex U.S. Index Fund | Utilities Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3% |
| Fidelity Global ex U.S. Index Fund | Taiwan | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.40% |
| Fidelity Global ex U.S. Index Fund | India | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.40% |
| Fidelity Global ex U.S. Index Fund | China | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 8.20% |
| Fidelity Global ex U.S. Index Fund | OtherMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 33.60% |
| Fidelity Global ex U.S. Index Fund | Japan | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.60% |
| Fidelity Global ex U.S. Index Fund | United States | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 8.40% |
| Fidelity Global ex U.S. Index Fund | Canada | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 7.40% |
| Fidelity Global ex U.S. Index Fund | United Kingdom | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.70% |
| Fidelity Global ex U.S. Index Fund | France | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.70% |
| Fidelity Global ex U.S. Index Fund | Germany | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.60% |
| Fidelity Global ex U.S. Index Fund | AACommonStocksMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 96.80% |
| Fidelity Global ex U.S. Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.80% |
| Fidelity Global ex U.S. Index Fund | AAPreferredStocksMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.40% |
| Fidelity Global ex U.S. Index Fund | AABondsMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0% |
| Fidelity Total International Index Fund | TH0Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.60% |
| Fidelity Total International Index Fund | TH1Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.20% |
| Fidelity Total International Index Fund | TH2Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.20% |
| Fidelity Total International Index Fund | TH3Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.90% |
| Fidelity Total International Index Fund | TH4Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.90% |
| Fidelity Total International Index Fund | TH5Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.80% |
| Fidelity Total International Index Fund | TH6Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.70% |
| Fidelity Total International Index Fund | TH7Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.70% |
| Fidelity Total International Index Fund | TH8Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.70% |
| Fidelity Total International Index Fund | TH9Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.70% |
| Fidelity Total International Index Fund | MSFinancialsSectorMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 22.20% |
| Fidelity Total International Index Fund | Information Technology Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 12.40% |
| Fidelity Total International Index Fund | Healthcare Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 8.90% |
| Fidelity Total International Index Fund | Real Estate Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.50% |
| Fidelity Total International Index Fund | Industrial Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 14.30% |
| Fidelity Total International Index Fund | Materials Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 7.20% |
| Fidelity Total International Index Fund | Consumer Discretionary Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 11.10% |
| Fidelity Total International Index Fund | Consumer Staples Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 7% |
| Fidelity Total International Index Fund | Communications Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.90% |
| Fidelity Total International Index Fund | Energy Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.40% |
| Fidelity Total International Index Fund | Utilities Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3% |
| Fidelity Total International Index Fund | Taiwan | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.60% |
| Fidelity Total International Index Fund | India | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6% |
| Fidelity Total International Index Fund | China | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 7.60% |
| Fidelity Total International Index Fund | OtherMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 33.90% |
| Fidelity Total International Index Fund | Japan | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 14.90% |
| Fidelity Total International Index Fund | United States | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 7.10% |
| Fidelity Total International Index Fund | Canada | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 7.50% |
| Fidelity Total International Index Fund | United Kingdom | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 7.10% |
| Fidelity Total International Index Fund | France | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.20% |
| Fidelity Total International Index Fund | Germany | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.10% |
| Fidelity Total International Index Fund | AACommonStocksMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 97.60% |
| Fidelity Total International Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.10% |
| Fidelity Total International Index Fund | AAPreferredStocksMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.30% |
| Fidelity Emerging Markets Index Fund | TH0Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 9.60% |
| Fidelity Emerging Markets Index Fund | TH1Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.30% |
| Fidelity Emerging Markets Index Fund | TH2Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.50% |
| Fidelity Emerging Markets Index Fund | TH3Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.40% |
| Fidelity Emerging Markets Index Fund | TH4Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.50% |
| Fidelity Emerging Markets Index Fund | TH5Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.20% |
| Fidelity Emerging Markets Index Fund | TH6Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.10% |
| Fidelity Emerging Markets Index Fund | TH7Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.10% |
| Fidelity Emerging Markets Index Fund | TH8Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1% |
| Fidelity Emerging Markets Index Fund | TH9Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1% |
| Fidelity Emerging Markets Index Fund | MSFinancialsSectorMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 23.20% |
| Fidelity Emerging Markets Index Fund | Information Technology Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 22.80% |
| Fidelity Emerging Markets Index Fund | Healthcare Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.40% |
| Fidelity Emerging Markets Index Fund | Real Estate Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.30% |
| Fidelity Emerging Markets Index Fund | Industrial Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.40% |
| Fidelity Emerging Markets Index Fund | Materials Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.20% |
| Fidelity Emerging Markets Index Fund | Consumer Discretionary Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.10% |
| Fidelity Emerging Markets Index Fund | Consumer Staples Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.70% |
| Fidelity Emerging Markets Index Fund | Communications Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 8.60% |
| Fidelity Emerging Markets Index Fund | Energy Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.50% |
| Fidelity Emerging Markets Index Fund | Utilities Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.70% |
| Fidelity Emerging Markets Index Fund | Taiwan | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 18.10% |
| Fidelity Emerging Markets Index Fund | India | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 18.30% |
| Fidelity Emerging Markets Index Fund | China | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 26.70% |
| Fidelity Emerging Markets Index Fund | Saudi Arabia | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.80% |
| Fidelity Emerging Markets Index Fund | Korea, Republic of | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 9.80% |
| Fidelity Emerging Markets Index Fund | OtherMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.70% |
| Fidelity Emerging Markets Index Fund | Brazil | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.60% |
| Fidelity Emerging Markets Index Fund | South Africa | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.90% |
| Fidelity Emerging Markets Index Fund | United States | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.20% |
| Fidelity Emerging Markets Index Fund | Mexico | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.90% |
| Fidelity Emerging Markets Index Fund | AACommonStocksMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 96.40% |
| Fidelity Emerging Markets Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.10% |
| Fidelity Emerging Markets Index Fund | AAPreferredStocksMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.50% |
| Fidelity Emerging Markets Index Fund | AABondsMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0% |
| Fidelity U.S. Sustainability Index Fund | TH0Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 11.20% |
| Fidelity U.S. Sustainability Index Fund | TH1Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 9.90% |
| Fidelity U.S. Sustainability Index Fund | TH2Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.50% |
| Fidelity U.S. Sustainability Index Fund | TH3Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3% |
| Fidelity U.S. Sustainability Index Fund | TH4Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.60% |
| Fidelity U.S. Sustainability Index Fund | TH5Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.50% |
| Fidelity U.S. Sustainability Index Fund | TH6Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.60% |
| Fidelity U.S. Sustainability Index Fund | TH7Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.40% |
| Fidelity U.S. Sustainability Index Fund | TH8Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.30% |
| Fidelity U.S. Sustainability Index Fund | TH9Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.30% |
| Fidelity U.S. Sustainability Index Fund | MSFinancialsSectorMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 11.30% |
| Fidelity U.S. Sustainability Index Fund | Information Technology Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 31.40% |
| Fidelity U.S. Sustainability Index Fund | Healthcare Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 9.80% |
| Fidelity U.S. Sustainability Index Fund | Real Estate Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.10% |
| Fidelity U.S. Sustainability Index Fund | Industrial Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 7.80% |
| Fidelity U.S. Sustainability Index Fund | Materials Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.40% |
| Fidelity U.S. Sustainability Index Fund | Consumer Discretionary Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 9% |
| Fidelity U.S. Sustainability Index Fund | Consumer Staples Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.60% |
| Fidelity U.S. Sustainability Index Fund | Communications Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 8.70% |
| Fidelity U.S. Sustainability Index Fund | Energy Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.50% |
| Fidelity U.S. Sustainability Index Fund | Utilities Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.90% |
| Fidelity U.S. Sustainability Index Fund | China | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.20% |
| Fidelity U.S. Sustainability Index Fund | Brazil | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.30% |
| Fidelity U.S. Sustainability Index Fund | United States | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 99.50% |
| Fidelity U.S. Sustainability Index Fund | AACommonStocksMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 89.50% |
| Fidelity U.S. Sustainability Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.50% |
| Fidelity SAI International Quality Index Fund | TH0Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.70% |
| Fidelity SAI International Quality Index Fund | TH1Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.50% |
| Fidelity SAI International Quality Index Fund | TH2Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.20% |
| Fidelity SAI International Quality Index Fund | TH3Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.20% |
| Fidelity SAI International Quality Index Fund | TH4Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.10% |
| Fidelity SAI International Quality Index Fund | TH5Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3% |
| Fidelity SAI International Quality Index Fund | TH6Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.70% |
| Fidelity SAI International Quality Index Fund | TH7Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.70% |
| Fidelity SAI International Quality Index Fund | TH8Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.70% |
| Fidelity SAI International Quality Index Fund | TH9Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.50% |
| Fidelity SAI International Quality Index Fund | MSFinancialsSectorMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 14.10% |
| Fidelity SAI International Quality Index Fund | Information Technology Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13% |
| Fidelity SAI International Quality Index Fund | Healthcare Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 17.50% |
| Fidelity SAI International Quality Index Fund | Real Estate Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.20% |
| Fidelity SAI International Quality Index Fund | Industrial Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 16.30% |
| Fidelity SAI International Quality Index Fund | Materials Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6% |
| Fidelity SAI International Quality Index Fund | Consumer Discretionary Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 14.60% |
| Fidelity SAI International Quality Index Fund | Consumer Staples Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 11.50% |
| Fidelity SAI International Quality Index Fund | Communications Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4% |
| Fidelity SAI International Quality Index Fund | Energy Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.40% |
| Fidelity SAI International Quality Index Fund | Utilities Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.60% |
| Fidelity SAI International Quality Index Fund | OtherMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 11% |
| Fidelity SAI International Quality Index Fund | Japan | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 18.80% |
| Fidelity SAI International Quality Index Fund | United States | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.80% |
| Fidelity SAI International Quality Index Fund | United Kingdom | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.30% |
| Fidelity SAI International Quality Index Fund | France | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 8.30% |
| Fidelity SAI International Quality Index Fund | Germany | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.40% |
| Fidelity SAI International Quality Index Fund | Switzerland | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 15.90% |
| Fidelity SAI International Quality Index Fund | Denmark | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.70% |
| Fidelity SAI International Quality Index Fund | Netherlands | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 7.10% |
| Fidelity SAI International Quality Index Fund | Australia | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.70% |
| Fidelity SAI International Quality Index Fund | AACommonStocksMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 98.20% |
| Fidelity SAI International Quality Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.80% |
| Fidelity SAI Emerging Markets Index Fund | TH0Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 9.80% |
| Fidelity SAI Emerging Markets Index Fund | TH1Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.30% |
| Fidelity SAI Emerging Markets Index Fund | TH2Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.60% |
| Fidelity SAI Emerging Markets Index Fund | TH3Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.40% |
| Fidelity SAI Emerging Markets Index Fund | TH4Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.60% |
| Fidelity SAI Emerging Markets Index Fund | TH5Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.20% |
| Fidelity SAI Emerging Markets Index Fund | TH6Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.10% |
| Fidelity SAI Emerging Markets Index Fund | TH7Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.10% |
| Fidelity SAI Emerging Markets Index Fund | TH8Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.10% |
| Fidelity SAI Emerging Markets Index Fund | TH9Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1% |
| Fidelity SAI Emerging Markets Index Fund | MSFinancialsSectorMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 23.30% |
| Fidelity SAI Emerging Markets Index Fund | Information Technology Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 23.20% |
| Fidelity SAI Emerging Markets Index Fund | Healthcare Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.50% |
| Fidelity SAI Emerging Markets Index Fund | Real Estate Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.50% |
| Fidelity SAI Emerging Markets Index Fund | Industrial Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.50% |
| Fidelity SAI Emerging Markets Index Fund | Materials Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.40% |
| Fidelity SAI Emerging Markets Index Fund | Consumer Discretionary Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.30% |
| Fidelity SAI Emerging Markets Index Fund | Consumer Staples Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.90% |
| Fidelity SAI Emerging Markets Index Fund | Communications Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 8.70% |
| Fidelity SAI Emerging Markets Index Fund | Energy Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.50% |
| Fidelity SAI Emerging Markets Index Fund | Utilities Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.70% |
| Fidelity SAI Emerging Markets Index Fund | Taiwan | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 18.40% |
| Fidelity SAI Emerging Markets Index Fund | India | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 18.60% |
| Fidelity SAI Emerging Markets Index Fund | China | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 27.10% |
| Fidelity SAI Emerging Markets Index Fund | Saudi Arabia | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.90% |
| Fidelity SAI Emerging Markets Index Fund | Korea, Republic of | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 9.90% |
| Fidelity SAI Emerging Markets Index Fund | OtherMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.90% |
| Fidelity SAI Emerging Markets Index Fund | Brazil | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.70% |
| Fidelity SAI Emerging Markets Index Fund | South Africa | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.90% |
| Fidelity SAI Emerging Markets Index Fund | Indonesia | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.60% |
| Fidelity SAI Emerging Markets Index Fund | Mexico | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2% |
| Fidelity SAI Emerging Markets Index Fund | AACommonStocksMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 98% |
| Fidelity SAI Emerging Markets Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.50% |
| Fidelity SAI Emerging Markets Index Fund | AAPreferredStocksMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.50% |
| Fidelity SAI International Momentum Index Fund | TH0Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.60% |
| Fidelity SAI International Momentum Index Fund | TH1Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.40% |
| Fidelity SAI International Momentum Index Fund | TH2Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.30% |
| Fidelity SAI International Momentum Index Fund | TH3Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.20% |
| Fidelity SAI International Momentum Index Fund | TH4Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.20% |
| Fidelity SAI International Momentum Index Fund | TH5Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2% |
| Fidelity SAI International Momentum Index Fund | TH6Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2% |
| Fidelity SAI International Momentum Index Fund | TH7Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2% |
| Fidelity SAI International Momentum Index Fund | TH8Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.90% |
| Fidelity SAI International Momentum Index Fund | TH9Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.80% |
| Fidelity SAI International Momentum Index Fund | MSFinancialsSectorMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 23% |
| Fidelity SAI International Momentum Index Fund | Information Technology Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 7.50% |
| Fidelity SAI International Momentum Index Fund | Healthcare Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.40% |
| Fidelity SAI International Momentum Index Fund | Real Estate Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.40% |
| Fidelity SAI International Momentum Index Fund | Industrial Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 20.50% |
| Fidelity SAI International Momentum Index Fund | Materials Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.50% |
| Fidelity SAI International Momentum Index Fund | Consumer Discretionary Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 9.70% |
| Fidelity SAI International Momentum Index Fund | Consumer Staples Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 7.80% |
| Fidelity SAI International Momentum Index Fund | Communications Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.90% |
| Fidelity SAI International Momentum Index Fund | Energy Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.10% |
| Fidelity SAI International Momentum Index Fund | Utilities Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.10% |
| Fidelity SAI International Momentum Index Fund | OtherMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 15.50% |
| Fidelity SAI International Momentum Index Fund | Japan | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 26.50% |
| Fidelity SAI International Momentum Index Fund | United States | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 7.10% |
| Fidelity SAI International Momentum Index Fund | United Kingdom | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.10% |
| Fidelity SAI International Momentum Index Fund | France | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10% |
| Fidelity SAI International Momentum Index Fund | Germany | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 7.70% |
| Fidelity SAI International Momentum Index Fund | Switzerland | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.40% |
| Fidelity SAI International Momentum Index Fund | Denmark | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.10% |
| Fidelity SAI International Momentum Index Fund | Australia | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.90% |
| Fidelity SAI International Momentum Index Fund | Spain | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.70% |
| Fidelity SAI International Momentum Index Fund | AACommonStocksMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 98.90% |
| Fidelity SAI International Momentum Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.10% |
| Fidelity SAI International Value Index Fund | TH0Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.80% |
| Fidelity SAI International Value Index Fund | TH1Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.70% |
| Fidelity SAI International Value Index Fund | TH2Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.60% |
| Fidelity SAI International Value Index Fund | TH3Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.20% |
| Fidelity SAI International Value Index Fund | TH4Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.10% |
| Fidelity SAI International Value Index Fund | TH5Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.10% |
| Fidelity SAI International Value Index Fund | TH6Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.90% |
| Fidelity SAI International Value Index Fund | TH7Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.90% |
| Fidelity SAI International Value Index Fund | TH8Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.90% |
| Fidelity SAI International Value Index Fund | TH9Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.90% |
| Fidelity SAI International Value Index Fund | MSFinancialsSectorMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 23.60% |
| Fidelity SAI International Value Index Fund | Information Technology Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.20% |
| Fidelity SAI International Value Index Fund | Healthcare Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.20% |
| Fidelity SAI International Value Index Fund | Real Estate Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.10% |
| Fidelity SAI International Value Index Fund | Industrial Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 16.40% |
| Fidelity SAI International Value Index Fund | Materials Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 8.40% |
| Fidelity SAI International Value Index Fund | Consumer Discretionary Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.90% |
| Fidelity SAI International Value Index Fund | Consumer Staples Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.30% |
| Fidelity SAI International Value Index Fund | Communications Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.30% |
| Fidelity SAI International Value Index Fund | Energy Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.50% |
| Fidelity SAI International Value Index Fund | Utilities Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4% |
| Fidelity SAI International Value Index Fund | OtherMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 11.90% |
| Fidelity SAI International Value Index Fund | Japan | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 26.30% |
| Fidelity SAI International Value Index Fund | United States | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.20% |
| Fidelity SAI International Value Index Fund | United Kingdom | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 11.30% |
| Fidelity SAI International Value Index Fund | France | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 11.20% |
| Fidelity SAI International Value Index Fund | Germany | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.30% |
| Fidelity SAI International Value Index Fund | Australia | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.90% |
| Fidelity SAI International Value Index Fund | Spain | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.40% |
| Fidelity SAI International Value Index Fund | Singapore | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.60% |
| Fidelity SAI International Value Index Fund | Italy | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.90% |
| Fidelity SAI International Value Index Fund | AACommonStocksMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 98.90% |
| Fidelity SAI International Value Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.10% |
| Fidelity SAI International Index Fund | TH0Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.20% |
| Fidelity SAI International Index Fund | TH1Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.60% |
| Fidelity SAI International Index Fund | TH2Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.50% |
| Fidelity SAI International Index Fund | TH3Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.50% |
| Fidelity SAI International Index Fund | TH4Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.40% |
| Fidelity SAI International Index Fund | TH5Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.30% |
| Fidelity SAI International Index Fund | TH6Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.30% |
| Fidelity SAI International Index Fund | TH7Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.30% |
| Fidelity SAI International Index Fund | TH8Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.20% |
| Fidelity SAI International Index Fund | TH9Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.10% |
| Fidelity SAI International Index Fund | MSFinancialsSectorMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 21.40% |
| Fidelity SAI International Index Fund | Information Technology Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 8.20% |
| Fidelity SAI International Index Fund | Healthcare Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13% |
| Fidelity SAI International Index Fund | Real Estate Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.80% |
| Fidelity SAI International Index Fund | Industrial Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 17.50% |
| Fidelity SAI International Index Fund | Materials Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.20% |
| Fidelity SAI International Index Fund | Consumer Discretionary Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.90% |
| Fidelity SAI International Index Fund | Consumer Staples Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 8.30% |
| Fidelity SAI International Index Fund | Communications Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.10% |
| Fidelity SAI International Index Fund | Energy Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.50% |
| Fidelity SAI International Index Fund | Utilities Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.20% |
| Fidelity SAI International Index Fund | OtherMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 17% |
| Fidelity SAI International Index Fund | Japan | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 22% |
| Fidelity SAI International Index Fund | United States | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.90% |
| Fidelity SAI International Index Fund | United Kingdom | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.80% |
| Fidelity SAI International Index Fund | France | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 9.30% |
| Fidelity SAI International Index Fund | Germany | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 8.90% |
| Fidelity SAI International Index Fund | Switzerland | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.20% |
| Fidelity SAI International Index Fund | Denmark | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.40% |
| Fidelity SAI International Index Fund | Netherlands | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4% |
| Fidelity SAI International Index Fund | Australia | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 7.50% |
| Fidelity SAI International Index Fund | AACommonStocksMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 97.70% |
| Fidelity SAI International Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.90% |
| Fidelity SAI International Index Fund | AAPreferredStocksMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.40% |
| Fidelity Series Global ex U.S. Index Fund | TH0Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.90% |
| Fidelity Series Global ex U.S. Index Fund | TH1Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.30% |
| Fidelity Series Global ex U.S. Index Fund | TH2Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.20% |
| Fidelity Series Global ex U.S. Index Fund | TH3Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.10% |
| Fidelity Series Global ex U.S. Index Fund | TH4Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1% |
| Fidelity Series Global ex U.S. Index Fund | TH5Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.90% |
| Fidelity Series Global ex U.S. Index Fund | TH6Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.90% |
| Fidelity Series Global ex U.S. Index Fund | TH7Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.80% |
| Fidelity Series Global ex U.S. Index Fund | TH8Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.80% |
| Fidelity Series Global ex U.S. Index Fund | TH9Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.80% |
| Fidelity Series Global ex U.S. Index Fund | MSFinancialsSectorMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 23.30% |
| Fidelity Series Global ex U.S. Index Fund | Information Technology Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 12.80% |
| Fidelity Series Global ex U.S. Index Fund | Healthcare Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 8.90% |
| Fidelity Series Global ex U.S. Index Fund | Real Estate Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.60% |
| Fidelity Series Global ex U.S. Index Fund | Industrial Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.10% |
| Fidelity Series Global ex U.S. Index Fund | Materials Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.50% |
| Fidelity Series Global ex U.S. Index Fund | Consumer Discretionary Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.60% |
| Fidelity Series Global ex U.S. Index Fund | Consumer Staples Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.80% |
| Fidelity Series Global ex U.S. Index Fund | Communications Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.90% |
| Fidelity Series Global ex U.S. Index Fund | Energy Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.60% |
| Fidelity Series Global ex U.S. Index Fund | Utilities Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3% |
| Fidelity Series Global ex U.S. Index Fund | Taiwan | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.30% |
| Fidelity Series Global ex U.S. Index Fund | India | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.40% |
| Fidelity Series Global ex U.S. Index Fund | China | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 8.20% |
| Fidelity Series Global ex U.S. Index Fund | OtherMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 32.90% |
| Fidelity Series Global ex U.S. Index Fund | Japan | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.50% |
| Fidelity Series Global ex U.S. Index Fund | United States | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 9.50% |
| Fidelity Series Global ex U.S. Index Fund | Canada | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 7.40% |
| Fidelity Series Global ex U.S. Index Fund | United Kingdom | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.60% |
| Fidelity Series Global ex U.S. Index Fund | France | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.70% |
| Fidelity Series Global ex U.S. Index Fund | Germany | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.50% |
| Fidelity Series Global ex U.S. Index Fund | AACommonStocksMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 95.70% |
| Fidelity Series Global ex U.S. Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.90% |
| Fidelity Series Global ex U.S. Index Fund | AAPreferredStocksMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.40% |
| Fidelity Series Global ex U.S. Index Fund | AABondsMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0% |
| Fidelity SAI International Low Volatility Index Fund | TH0Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.10% |
| Fidelity SAI International Low Volatility Index Fund | TH1Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2% |
| Fidelity SAI International Low Volatility Index Fund | TH2Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2% |
| Fidelity SAI International Low Volatility Index Fund | TH3Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2% |
| Fidelity SAI International Low Volatility Index Fund | TH4Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2% |
| Fidelity SAI International Low Volatility Index Fund | TH5Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.90% |
| Fidelity SAI International Low Volatility Index Fund | TH6Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.90% |
| Fidelity SAI International Low Volatility Index Fund | TH7Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.90% |
| Fidelity SAI International Low Volatility Index Fund | TH8Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.90% |
| Fidelity SAI International Low Volatility Index Fund | TH9Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.80% |
| Fidelity SAI International Low Volatility Index Fund | MSFinancialsSectorMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 17.60% |
| Fidelity SAI International Low Volatility Index Fund | Information Technology Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.90% |
| Fidelity SAI International Low Volatility Index Fund | Healthcare Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 16.30% |
| Fidelity SAI International Low Volatility Index Fund | Real Estate Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.30% |
| Fidelity SAI International Low Volatility Index Fund | Industrial Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.40% |
| Fidelity SAI International Low Volatility Index Fund | Materials Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.20% |
| Fidelity SAI International Low Volatility Index Fund | Consumer Discretionary Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.10% |
| Fidelity SAI International Low Volatility Index Fund | Consumer Staples Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.30% |
| Fidelity SAI International Low Volatility Index Fund | Communications Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 8.80% |
| Fidelity SAI International Low Volatility Index Fund | Utilities Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 8.20% |
| Fidelity SAI International Low Volatility Index Fund | OtherMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 11.30% |
| Fidelity SAI International Low Volatility Index Fund | Japan | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 29.70% |
| Fidelity SAI International Low Volatility Index Fund | United States | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 9.80% |
| Fidelity SAI International Low Volatility Index Fund | United Kingdom | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13.50% |
| Fidelity SAI International Low Volatility Index Fund | France | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.10% |
| Fidelity SAI International Low Volatility Index Fund | Germany | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.60% |
| Fidelity SAI International Low Volatility Index Fund | Switzerland | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 10.90% |
| Fidelity SAI International Low Volatility Index Fund | Denmark | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.50% |
| Fidelity SAI International Low Volatility Index Fund | Netherlands | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.80% |
| Fidelity SAI International Low Volatility Index Fund | Hong Kong | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.80% |
| Fidelity SAI International Low Volatility Index Fund | AACommonStocksMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 99.10% |
| Fidelity SAI International Low Volatility Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.90% |
| Fidelity SAI U.S. Low Volatility Index Fund | TH0Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 7.70% |
| Fidelity SAI U.S. Low Volatility Index Fund | TH1Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.30% |
| Fidelity SAI U.S. Low Volatility Index Fund | TH2Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.90% |
| Fidelity SAI U.S. Low Volatility Index Fund | TH3Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.30% |
| Fidelity SAI U.S. Low Volatility Index Fund | TH4Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3% |
| Fidelity SAI U.S. Low Volatility Index Fund | TH5Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.90% |
| Fidelity SAI U.S. Low Volatility Index Fund | TH6Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.90% |
| Fidelity SAI U.S. Low Volatility Index Fund | TH7Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.80% |
| Fidelity SAI U.S. Low Volatility Index Fund | TH8Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.60% |
| Fidelity SAI U.S. Low Volatility Index Fund | TH9Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.60% |
| Fidelity SAI U.S. Low Volatility Index Fund | MSFinancialsSectorMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 11.70% |
| Fidelity SAI U.S. Low Volatility Index Fund | Information Technology Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 28.40% |
| Fidelity SAI U.S. Low Volatility Index Fund | Healthcare Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 13% |
| Fidelity SAI U.S. Low Volatility Index Fund | Real Estate Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.50% |
| Fidelity SAI U.S. Low Volatility Index Fund | Industrial Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 9.40% |
| Fidelity SAI U.S. Low Volatility Index Fund | Materials Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.30% |
| Fidelity SAI U.S. Low Volatility Index Fund | Consumer Discretionary Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 8.30% |
| Fidelity SAI U.S. Low Volatility Index Fund | Consumer Staples Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 7.20% |
| Fidelity SAI U.S. Low Volatility Index Fund | Communications Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.90% |
| Fidelity SAI U.S. Low Volatility Index Fund | Energy Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.80% |
| Fidelity SAI U.S. Low Volatility Index Fund | Utilities Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.30% |
| Fidelity SAI U.S. Low Volatility Index Fund | United States | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 100% |
| Fidelity SAI U.S. Low Volatility Index Fund | AACommonStocksMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 99.80% |
| Fidelity SAI U.S. Low Volatility Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.20% |
