| Form N-CSR Cover | 12 Months Ended |
| Dec. 31, 2024 | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSR |
| Amendment Flag | false |
| Registrant Name | Fidelity Advisor Series I |
| Entity Central Index Key | 0000722574 |
| Entity Investment Company Type | N-1A |
| Document Period End Date | Dec. 31, 2024 |
| Shareholder Report | 12 Months Ended |
| Dec. 31, 2024 USD ($) shares | |
| Shareholder Report [Line Items] | |
| Document Type | N-CSR |
| Amendment Flag | false |
| Registrant Name | Fidelity Advisor Series I |
| Entity Central Index Key | 0000722574 |
| Entity Investment Company Type | N-1A |
| Document Period End Date | Dec. 31, 2024 |
| Fidelity Advisor Mid Cap II Fund - Class Z | |
| Shareholder Report [Line Items] | |
| Fund Name | Fidelity Advisor® Mid Cap II Fund |
| Class Name | Fidelity Advisor® Mid Cap II Fund Class Z |
| Trading Symbol | FZAMX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains information about Fidelity Advisor® Mid Cap II Fund for the period January 1, 2024 to December 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 1-877-208-0098 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 | 1-877-208-0098 |
| 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 Class Z $ 0.58 % |
| Expenses Paid, Amount | $ 63 |
| Expense Ratio, Percent | 0.58% |
| 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-B26"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:italic;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 December 31, 2014 through December 31, 2024. Initial investment of $10,000. Class Z $10,000 $9,862 $11,052 $13,341 $11,375 $14,086 $16,741 $20,989 $17,909 $20,627 $24,206 S&P MidCap 400® Index $10,000 $9,782 $11,811 $13,730 $12,208 $15,407 $17,511 $21,847 $18,993 $22,115 $25,196 Russell 3000® Index $10,000 $10,048 $11,327 $13,721 $13,002 $17,035 $20,593 $25,877 $20,907 $26,334 $32,604 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 Class Z 17.35% 11.44% 9.24% S&P MidCap 400® Index 13.93% 10.34% 9.68% Russell 3000® Index 23.81% 13.86% 12.55% Visit institutional.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 | $ 1,551,980,039 |
| Holdings Count | shares | 180 |
| Advisory Fees Paid, Amount | $ 9,939,485 |
| Investment Company Portfolio Turnover | 52% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics (as of December 31, 2024) KEY FACTS Fund Size $ Number of Holdings 180 Total Advisory Fee $ Portfolio Turnover 52 % |
| Holdings [Text Block] | MARKET SECTORS (% of Fund's net assets) Financials 20.1 Industrials 18.0 Consumer Discretionary 12.3 Health Care 11.7 Information Technology 9.8 Real Estate 6.5 Energy 6.0 Materials 5.2 Consumer Staples 4.9 Utilities 3.4 Communication Services 1.8 Common Stocks 99.7 Short-Term Investments and Net Other Assets (Liabilities) 0.3 ASSET ALLOCATION (% of Fund's net assets) Common Stocks - 99.7 Short-Term Investments and Net Other Assets (Liabilities) - 0.3 United States 91.1 Canada 2.2 Israel 1.6 United Kingdom 1.6 Belgium 0.9 Puerto Rico 0.8 Brazil 0.4 Italy 0.4 France 0.3 Others 0.7 GEOGRAPHIC DIVERSIFICATION (% of Fund's net assets) United States - 91.1 Canada - 2.2 Israel - 1.6 United Kingdom - 1.6 Belgium - 0.9 Puerto Rico - 0.8 Brazil - 0.4 Italy - 0.4 France - 0.3 Others - 0.7 |
| Largest Holdings [Text Block] | TOP HOLDINGS (% of Fund's net assets) US Foods Holding Corp 1.5 Reinsurance Group of America Inc 1.4 East West Bancorp Inc 1.4 ITT Inc 1.3 Williams-Sonoma Inc 1.3 Wintrust Financial Corp 1.3 Performance Food Group Co 1.2 Primerica Inc 1.2 AptarGroup Inc 1.2 Wix.com Ltd 1.2 13.0 |
| Material Fund Change [Text Block] | How has the Fund changed? This is a summary of certain changes to the Fund since January 1, 2024. For more complete information, you may review the Fund's next prospectus, which we expect to be available by March 1, 2025 at fundresearch.fidelity.com/prospectus/sec or upon request at 1-877-208-0098 or by sending an e-mail to fidfunddocuments fidelity.com . The fund's transfer agent and pricing & bookkeeping fees were changed to a fixed rate effective December 1, 2023. Effective March 1, 2024, the fund's management contract was amended to incorporate administrative services previously covered under separate services agreements (transfer agent and pricing & bookkeeping). The amended contract incorporates a management fee rate that may vary by class. The Adviser or an affiliate pays certain expenses of managing and operating the fund out of each class's management fee. |
| Material Fund Change Expenses [Text Block] | The fund's transfer agent and pricing & bookkeeping fees were changed to a fixed rate effective December 1, 2023. Effective March 1, 2024, the fund's management contract was amended to incorporate administrative services previously covered under separate services agreements (transfer agent and pricing & bookkeeping). The amended contract incorporates a management fee rate that may vary by class. The Adviser or an affiliate pays certain expenses of managing and operating the fund out of each class's management fee. |
| Summary of Change Legend [Text Block] | This is a summary of certain changes to the Fund since January 1, 2024. For more complete information, you may review the Fund's next prospectus, which we expect to be available by March 1, 2025 at fundresearch.fidelity.com/prospectus/sec or upon request at 1-877-208-0098 or by sending an e-mail to fidfunddocuments fidelity.com . |
| Updated Prospectus Phone Number | 1-877-208-0098</span>" id="sjs-B40"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;">1-877-208-0098</span> |
| Updated Prospectus Email Address | fidfunddocuments@fidelity.com</span>" id="sjs-B41"><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-B42"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;">fundresearch.fidelity.com/prospectus/sec</span> |
| Fidelity Advisor Mid Cap II Fund - Class C | |
| Shareholder Report [Line Items] | |
| Fund Name | Fidelity Advisor® Mid Cap II Fund |
| Class Name | Fidelity Advisor® Mid Cap II Fund Class C |
| Trading Symbol | FIICX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains information about Fidelity Advisor® Mid Cap II Fund for the period January 1, 2024 to December 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 1-877-208-0098 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 | 1-877-208-0098 |
| 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 Class C $ 1.71 % |
| Expenses Paid, Amount | $ 185 |
| Expense Ratio, Percent | 1.71% |
| 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-B59"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:italic;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 December 31, 2014 through December 31, 2024. Initial investment of $10,000. Class C $10,000 $9,743 $10,789 $12,867 $10,844 $13,272 $15,576 $19,300 $16,268 $18,660 $21,817 S&P MidCap 400® Index $10,000 $9,782 $11,811 $13,730 $12,208 $15,407 $17,511 $21,847 $18,993 $22,115 $25,196 Russell 3000® Index $10,000 $10,048 $11,327 $13,721 $13,002 $17,035 $20,593 $25,877 $20,907 $26,334 $32,604 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 Class C (incl. contingent deferred sales charge) 15.08% 10.11% 8.11% Class C 16.08% 10.11% 8.11% S&P MidCap 400® Index 13.93% 10.34% 9.68% Russell 3000® Index 23.81% 13.86% 12.55% Visit institutional.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 | $ 1,551,980,039 |
| Holdings Count | shares | 180 |
| Advisory Fees Paid, Amount | $ 9,939,485 |
| Investment Company Portfolio Turnover | 52% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics (as of December 31, 2024) KEY FACTS Fund Size $ Number of Holdings 180 Total Advisory Fee $ Portfolio Turnover 52 % |
| Holdings [Text Block] | MARKET SECTORS (% of Fund's net assets) Financials 20.1 Industrials 18.0 Consumer Discretionary 12.3 Health Care 11.7 Information Technology 9.8 Real Estate 6.5 Energy 6.0 Materials 5.2 Consumer Staples 4.9 Utilities 3.4 Communication Services 1.8 Common Stocks 99.7 Short-Term Investments and Net Other Assets (Liabilities) 0.3 ASSET ALLOCATION (% of Fund's net assets) Common Stocks - 99.7 Short-Term Investments and Net Other Assets (Liabilities) - 0.3 United States 91.1 Canada 2.2 Israel 1.6 United Kingdom 1.6 Belgium 0.9 Puerto Rico 0.8 Brazil 0.4 Italy 0.4 France 0.3 Others 0.7 GEOGRAPHIC DIVERSIFICATION (% of Fund's net assets) United States - 91.1 Canada - 2.2 Israel - 1.6 United Kingdom - 1.6 Belgium - 0.9 Puerto Rico - 0.8 Brazil - 0.4 Italy - 0.4 France - 0.3 Others - 0.7 |
| Largest Holdings [Text Block] | TOP HOLDINGS (% of Fund's net assets) US Foods Holding Corp 1.5 Reinsurance Group of America Inc 1.4 East West Bancorp Inc 1.4 ITT Inc 1.3 Williams-Sonoma Inc 1.3 Wintrust Financial Corp 1.3 Performance Food Group Co 1.2 Primerica Inc 1.2 AptarGroup Inc 1.2 Wix.com Ltd 1.2 13.0 |
| Material Fund Change [Text Block] | How has the Fund changed? This is a summary of certain changes to the Fund since January 1, 2024. For more complete information, you may review the Fund's next prospectus, which we expect to be available by March 1, 2025 at fundresearch.fidelity.com/prospectus/sec or upon request at 1-877-208-0098 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: Management fee Operating expenses The fund's transfer agent and pricing & bookkeeping fees were changed to a fixed rate effective December 1, 2023. Effective March 1, 2024, the fund's management contract was amended to incorporate administrative services previously covered under separate services agreements (transfer agent and pricing & bookkeeping). The amended contract incorporates a management fee rate that may vary by class. The Adviser or an affiliate pays certain expenses of managing and operating the fund out of each class's management fee. |
| 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: Management fee Operating expenses The fund's transfer agent and pricing & bookkeeping fees were changed to a fixed rate effective December 1, 2023. Effective March 1, 2024, the fund's management contract was amended to incorporate administrative services previously covered under separate services agreements (transfer agent and pricing & bookkeeping). The amended contract incorporates a management fee rate that may vary by class. The Adviser or an affiliate pays certain expenses of managing and operating the fund out of each class's management fee. |
| Summary of Change Legend [Text Block] | This is a summary of certain changes to the Fund since January 1, 2024. For more complete information, you may review the Fund's next prospectus, which we expect to be available by March 1, 2025 at fundresearch.fidelity.com/prospectus/sec or upon request at 1-877-208-0098 or by sending an e-mail to fidfunddocuments fidelity.com . |
| Updated Prospectus Phone Number | 1-877-208-0098</span>" id="sjs-B73"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;">1-877-208-0098</span> |
| Updated Prospectus Email Address | fidfunddocuments@fidelity.com</span>" id="sjs-B74"><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-B75"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;">fundresearch.fidelity.com/prospectus/sec</span> |
| Fidelity Advisor Mid Cap II Fund - Class A | |
| Shareholder Report [Line Items] | |
| Fund Name | Fidelity Advisor® Mid Cap II Fund |
| Class Name | Fidelity Advisor® Mid Cap II Fund Class A |
| Trading Symbol | FIIAX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains information about Fidelity Advisor® Mid Cap II Fund for the period January 1, 2024 to December 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 1-877-208-0098 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 | 1-877-208-0098 |
| 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 Class A $ 0.96 % |
| Expenses Paid, Amount | $ 105 |
| Expense Ratio, Percent | 0.96% |
| 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-B92"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:italic;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 December 31, 2014 through December 31, 2024. Initial investment of $10,000 and the current sales charge was paid. Class A $9,425 $9,251 $10,324 $12,414 $10,540 $12,997 $15,381 $19,214 $16,328 $18,729 $21,898 S&P MidCap 400® Index $10,000 $9,782 $11,811 $13,730 $12,208 $15,407 $17,511 $21,847 $18,993 $22,115 $25,196 Russell 3000® Index $10,000 $10,048 $11,327 $13,721 $13,002 $17,035 $20,593 $25,877 $20,907 $26,334 $32,604 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 Class A (incl. 5.75% sales charge) 10.20% 9.69% 8.15% Class A (without 5.75% sales charge) 16.92% 11.00% 8.80% S&P MidCap 400® Index 13.93% 10.34% 9.68% Russell 3000® Index 23.81% 13.86% 12.55% Visit institutional.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 | $ 1,551,980,039 |
| Holdings Count | shares | 180 |
| Advisory Fees Paid, Amount | $ 9,939,485 |
| Investment Company Portfolio Turnover | 52% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics (as of December 31, 2024) KEY FACTS Fund Size $ Number of Holdings 180 Total Advisory Fee $ Portfolio Turnover 52 % |
| Holdings [Text Block] | MARKET SECTORS (% of Fund's net assets) Financials 20.1 Industrials 18.0 Consumer Discretionary 12.3 Health Care 11.7 Information Technology 9.8 Real Estate 6.5 Energy 6.0 Materials 5.2 Consumer Staples 4.9 Utilities 3.4 Communication Services 1.8 Common Stocks 99.7 Short-Term Investments and Net Other Assets (Liabilities) 0.3 ASSET ALLOCATION (% of Fund's net assets) Common Stocks - 99.7 Short-Term Investments and Net Other Assets (Liabilities) - 0.3 United States 91.1 Canada 2.2 Israel 1.6 United Kingdom 1.6 Belgium 0.9 Puerto Rico 0.8 Brazil 0.4 Italy 0.4 France 0.3 Others 0.7 GEOGRAPHIC DIVERSIFICATION (% of Fund's net assets) United States - 91.1 Canada - 2.2 Israel - 1.6 United Kingdom - 1.6 Belgium - 0.9 Puerto Rico - 0.8 Brazil - 0.4 Italy - 0.4 France - 0.3 Others - 0.7 |
| Largest Holdings [Text Block] | TOP HOLDINGS (% of Fund's net assets) US Foods Holding Corp 1.5 Reinsurance Group of America Inc 1.4 East West Bancorp Inc 1.4 ITT Inc 1.3 Williams-Sonoma Inc 1.3 Wintrust Financial Corp 1.3 Performance Food Group Co 1.2 Primerica Inc 1.2 AptarGroup Inc 1.2 Wix.com Ltd 1.2 13.0 |
| Material Fund Change [Text Block] | How has the Fund changed? This is a summary of certain changes to the Fund since January 1, 2024. For more complete information, you may review the Fund's next prospectus, which we expect to be available by March 1, 2025 at fundresearch.fidelity.com/prospectus/sec or upon request at 1-877-208-0098 or by sending an e-mail to fidfunddocuments fidelity.com . The fund's transfer agent and pricing & bookkeeping fees were changed to a fixed rate effective December 1, 2023. Effective March 1, 2024, the fund's management contract was amended to incorporate administrative services previously covered under separate services agreements (transfer agent and pricing & bookkeeping). The amended contract incorporates a management fee rate that may vary by class. The Adviser or an affiliate pays certain expenses of managing and operating the fund out of each class's management fee. |
| Material Fund Change Expenses [Text Block] | The fund's transfer agent and pricing & bookkeeping fees were changed to a fixed rate effective December 1, 2023. Effective March 1, 2024, the fund's management contract was amended to incorporate administrative services previously covered under separate services agreements (transfer agent and pricing & bookkeeping). The amended contract incorporates a management fee rate that may vary by class. The Adviser or an affiliate pays certain expenses of managing and operating the fund out of each class's management fee. |
| Summary of Change Legend [Text Block] | This is a summary of certain changes to the Fund since January 1, 2024. For more complete information, you may review the Fund's next prospectus, which we expect to be available by March 1, 2025 at fundresearch.fidelity.com/prospectus/sec or upon request at 1-877-208-0098 or by sending an e-mail to fidfunddocuments fidelity.com . |
| Updated Prospectus Phone Number | 1-877-208-0098</span>" id="sjs-B106"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;">1-877-208-0098</span> |
| Updated Prospectus Email Address | fidfunddocuments@fidelity.com</span>" id="sjs-B107"><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-B108"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;">fundresearch.fidelity.com/prospectus/sec</span> |
| Fidelity Advisor Mid Cap II Fund - Class M | |
| Shareholder Report [Line Items] | |
| Fund Name | Fidelity Advisor® Mid Cap II Fund |
| Class Name | Fidelity Advisor® Mid Cap II Fund Class M |
| Trading Symbol | FITIX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains information about Fidelity Advisor® Mid Cap II Fund for the period January 1, 2024 to December 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 1-877-208-0098 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 | 1-877-208-0098 |
| 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 Class M $ 1.21 % |
| Expenses Paid, Amount | $ 131 |
| Expense Ratio, Percent | 1.21% |
| 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-B125"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:italic;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 December 31, 2014 through December 31, 2024. Initial investment of $10,000 and the current sales charge was paid. Class M $9,650 $9,453 $10,523 $12,618 $10,693 $13,155 $15,530 $19,347 $16,408 $18,773 $21,888 S&P MidCap 400® Index $10,000 $9,782 $11,811 $13,730 $12,208 $15,407 $17,511 $21,847 $18,993 $22,115 $25,196 Russell 3000® Index $10,000 $10,048 $11,327 $13,721 $13,002 $17,035 $20,593 $25,877 $20,907 $26,334 $32,604 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 Class M (incl. 3.50% sales charge) 12.51% 9.93% 8.15% Class M (without 3.50% sales charge) 16.59% 10.72% 8.53% S&P MidCap 400® Index 13.93% 10.34% 9.68% Russell 3000® Index 23.81% 13.86% 12.55% Visit institutional.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 | $ 1,551,980,039 |
| Holdings Count | shares | 180 |
| Advisory Fees Paid, Amount | $ 9,939,485 |
| Investment Company Portfolio Turnover | 52% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics (as of December 31, 2024) KEY FACTS Fund Size $ Number of Holdings 180 Total Advisory Fee $ Portfolio Turnover 52 % |
| Holdings [Text Block] | MARKET SECTORS (% of Fund's net assets) Financials 20.1 Industrials 18.0 Consumer Discretionary 12.3 Health Care 11.7 Information Technology 9.8 Real Estate 6.5 Energy 6.0 Materials 5.2 Consumer Staples 4.9 Utilities 3.4 Communication Services 1.8 Common Stocks 99.7 Short-Term Investments and Net Other Assets (Liabilities) 0.3 ASSET ALLOCATION (% of Fund's net assets) Common Stocks - 99.7 Short-Term Investments and Net Other Assets (Liabilities) - 0.3 United States 91.1 Canada 2.2 Israel 1.6 United Kingdom 1.6 Belgium 0.9 Puerto Rico 0.8 Brazil 0.4 Italy 0.4 France 0.3 Others 0.7 GEOGRAPHIC DIVERSIFICATION (% of Fund's net assets) United States - 91.1 Canada - 2.2 Israel - 1.6 United Kingdom - 1.6 Belgium - 0.9 Puerto Rico - 0.8 Brazil - 0.4 Italy - 0.4 France - 0.3 Others - 0.7 |
| Largest Holdings [Text Block] | TOP HOLDINGS (% of Fund's net assets) US Foods Holding Corp 1.5 Reinsurance Group of America Inc 1.4 East West Bancorp Inc 1.4 ITT Inc 1.3 Williams-Sonoma Inc 1.3 Wintrust Financial Corp 1.3 Performance Food Group Co 1.2 Primerica Inc 1.2 AptarGroup Inc 1.2 Wix.com Ltd 1.2 13.0 |
| Material Fund Change [Text Block] | How has the Fund changed? This is a summary of certain changes to the Fund since January 1, 2024. For more complete information, you may review the Fund's next prospectus, which we expect to be available by March 1, 2025 at fundresearch.fidelity.com/prospectus/sec or upon request at 1-877-208-0098 or by sending an e-mail to fidfunddocuments fidelity.com . The fund's transfer agent and pricing & bookkeeping fees were changed to a fixed rate effective December 1, 2023. Effective March 1, 2024, the fund's management contract was amended to incorporate administrative services previously covered under separate services agreements (transfer agent and pricing & bookkeeping). The amended contract incorporates a management fee rate that may vary by class. The Adviser or an affiliate pays certain expenses of managing and operating the fund out of each class's management fee. |
| Material Fund Change Expenses [Text Block] | The fund's transfer agent and pricing & bookkeeping fees were changed to a fixed rate effective December 1, 2023. Effective March 1, 2024, the fund's management contract was amended to incorporate administrative services previously covered under separate services agreements (transfer agent and pricing & bookkeeping). The amended contract incorporates a management fee rate that may vary by class. The Adviser or an affiliate pays certain expenses of managing and operating the fund out of each class's management fee. |
| Summary of Change Legend [Text Block] | This is a summary of certain changes to the Fund since January 1, 2024. For more complete information, you may review the Fund's next prospectus, which we expect to be available by March 1, 2025 at fundresearch.fidelity.com/prospectus/sec or upon request at 1-877-208-0098 or by sending an e-mail to fidfunddocuments fidelity.com . |
| Updated Prospectus Phone Number | 1-877-208-0098</span>" id="sjs-B139"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;">1-877-208-0098</span> |
| Updated Prospectus Email Address | fidfunddocuments@fidelity.com</span>" id="sjs-B140"><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-B141"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;">fundresearch.fidelity.com/prospectus/sec</span> |
| Fidelity Advisor Mid Cap II Fund - Class I | |
| Shareholder Report [Line Items] | |
| Fund Name | Fidelity Advisor® Mid Cap II Fund |
| Class Name | Fidelity Advisor® Mid Cap II Fund Class I |
| Trading Symbol | FIIMX |
| Annual or Semi-Annual Statement [Text Block] | This annual shareholder report contains information about Fidelity Advisor® Mid Cap II Fund for the period January 1, 2024 to December 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 1-877-208-0098 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 | 1-877-208-0098 |
| 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 Class I $ 0.71 % |
| Expenses Paid, Amount | $ 77 |
| Expense Ratio, Percent | 0.71% |
| 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-B158"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:italic;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 December 31, 2014 through December 31, 2024. Initial investment of $10,000. Class I $10,000 $9,848 $11,020 $13,285 $11,319 $13,995 $16,609 $20,801 $17,728 $20,392 $23,894 S&P MidCap 400® Index $10,000 $9,782 $11,811 $13,730 $12,208 $15,407 $17,511 $21,847 $18,993 $22,115 $25,196 Russell 3000® Index $10,000 $10,048 $11,327 $13,721 $13,002 $17,035 $20,593 $25,877 $20,907 $26,334 $32,604 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 Class I 17.17% 11.29% 9.10% S&P MidCap 400® Index 13.93% 10.34% 9.68% Russell 3000® Index 23.81% 13.86% 12.55% Visit institutional.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 | $ 1,551,980,039 |
| Holdings Count | shares | 180 |
| Advisory Fees Paid, Amount | $ 9,939,485 |
| Investment Company Portfolio Turnover | 52% |
| Additional Fund Statistics [Text Block] | Key Fund Statistics (as of December 31, 2024) KEY FACTS Fund Size $ Number of Holdings 180 Total Advisory Fee $ Portfolio Turnover 52 % |
| Holdings [Text Block] | MARKET SECTORS (% of Fund's net assets) Financials 20.1 Industrials 18.0 Consumer Discretionary 12.3 Health Care 11.7 Information Technology 9.8 Real Estate 6.5 Energy 6.0 Materials 5.2 Consumer Staples 4.9 Utilities 3.4 Communication Services 1.8 Common Stocks 99.7 Short-Term Investments and Net Other Assets (Liabilities) 0.3 ASSET ALLOCATION (% of Fund's net assets) Common Stocks - 99.7 Short-Term Investments and Net Other Assets (Liabilities) - 0.3 United States 91.1 Canada 2.2 Israel 1.6 United Kingdom 1.6 Belgium 0.9 Puerto Rico 0.8 Brazil 0.4 Italy 0.4 France 0.3 Others 0.7 GEOGRAPHIC DIVERSIFICATION (% of Fund's net assets) United States - 91.1 Canada - 2.2 Israel - 1.6 United Kingdom - 1.6 Belgium - 0.9 Puerto Rico - 0.8 Brazil - 0.4 Italy - 0.4 France - 0.3 Others - 0.7 |
| Largest Holdings [Text Block] | TOP HOLDINGS (% of Fund's net assets) US Foods Holding Corp 1.5 Reinsurance Group of America Inc 1.4 East West Bancorp Inc 1.4 ITT Inc 1.3 Williams-Sonoma Inc 1.3 Wintrust Financial Corp 1.3 Performance Food Group Co 1.2 Primerica Inc 1.2 AptarGroup Inc 1.2 Wix.com Ltd 1.2 13.0 |
| Material Fund Change [Text Block] | How has the Fund changed? This is a summary of certain changes to the Fund since January 1, 2024. For more complete information, you may review the Fund's next prospectus, which we expect to be available by March 1, 2025 at fundresearch.fidelity.com/prospectus/sec or upon request at 1-877-208-0098 or by sending an e-mail to fidfunddocuments fidelity.com . The fund's transfer agent and pricing & bookkeeping fees were changed to a fixed rate effective December 1, 2023. Effective March 1, 2024, the fund's management contract was amended to incorporate administrative services previously covered under separate services agreements (transfer agent and pricing & bookkeeping). The amended contract incorporates a management fee rate that may vary by class. The Adviser or an affiliate pays certain expenses of managing and operating the fund out of each class's management fee. |
| Material Fund Change Expenses [Text Block] | The fund's transfer agent and pricing & bookkeeping fees were changed to a fixed rate effective December 1, 2023. Effective March 1, 2024, the fund's management contract was amended to incorporate administrative services previously covered under separate services agreements (transfer agent and pricing & bookkeeping). The amended contract incorporates a management fee rate that may vary by class. The Adviser or an affiliate pays certain expenses of managing and operating the fund out of each class's management fee. |
| Summary of Change Legend [Text Block] | This is a summary of certain changes to the Fund since January 1, 2024. For more complete information, you may review the Fund's next prospectus, which we expect to be available by March 1, 2025 at fundresearch.fidelity.com/prospectus/sec or upon request at 1-877-208-0098 or by sending an e-mail to fidfunddocuments fidelity.com . |
| Updated Prospectus Phone Number | 1-877-208-0098</span>" id="sjs-B172"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:normal;">1-877-208-0098</span> |
| Updated Prospectus Email Address | fidfunddocuments@fidelity.com</span>" id="sjs-B173"><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-B174"><span style="font-family:'Fidelity Sans';font-size:11px;color:#000000;font-style:normal;font-weight:bold;">fundresearch.fidelity.com/prospectus/sec</span> |
| Shareholder Report, Line Graph (Details) - USD ($) | 12 Months Ended | 60 Months Ended | 120 Months Ended | 132 Months Ended | ||||||||||
| Dec. 31, 2024 | Dec. 31, 2024 | Dec. 31, 2024 | Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | |
| C000130154_1_BBIndexMember_1YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 23.81% | |||||||||||||
| C000130154_1_BBIndexMember_5YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 13.86% | |||||||||||||
| C000130154_1_BBIndexMember_10YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 12.55% | |||||||||||||
| C000048876_1_BBIndexMember_1YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 23.81% | |||||||||||||
| C000048876_1_BBIndexMember_5YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 13.86% | |||||||||||||
| C000048876_1_BBIndexMember_10YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 12.55% | |||||||||||||
| C000048874_1_BBIndexMember_1YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 23.81% | |||||||||||||
| C000048874_1_BBIndexMember_5YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 13.86% | |||||||||||||
| C000048874_1_BBIndexMember_10YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 12.55% | |||||||||||||
| C000048877_1_BBIndexMember_1YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 23.81% | |||||||||||||
| C000048877_1_BBIndexMember_5YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 13.86% | |||||||||||||
| C000048877_1_BBIndexMember_10YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 12.55% | |||||||||||||
| C000048878_1_BBIndexMember_1YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 23.81% | |||||||||||||
| C000048878_1_BBIndexMember_5YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 13.86% | |||||||||||||
| C000048878_1_BBIndexMember_10YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 12.55% | |||||||||||||
| C000130154_LG_ClassMember_11YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Class Z</span>" id="sjs-E50"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Class Z</span> | |||||||||||||
| C000130154_ClassMember_AsOf_2014Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 10,000 | |||||||||||||
| C000130154_ClassMember_AsOf_2015Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 9,862 | |||||||||||||
| C000130154_ClassMember_AsOf_2016Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 11,052 | |||||||||||||
| C000130154_ClassMember_AsOf_2017Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 13,341 | |||||||||||||
| C000130154_ClassMember_AsOf_2018Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 11,375 | |||||||||||||
| C000130154_ClassMember_AsOf_2019Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 14,086 | |||||||||||||
| C000130154_ClassMember_AsOf_2020Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 16,741 | |||||||||||||
| C000130154_ClassMember_AsOf_2021Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 20,989 | |||||||||||||
| C000130154_ClassMember_AsOf_2022Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 17,909 | |||||||||||||
| C000130154_ClassMember_AsOf_2023Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 20,627 | |||||||||||||
| C000130154_ClassMember_AsOf_2024Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 24,206 | $ 24,206 | $ 24,206 | $ 24,206 | ||||||||||
| C000130154_LG_1_AdditionalIndexMember_11YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | S&P MidCap 400® Index</span>" id="sjs-E86"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">S&P MidCap 400® Index</span> | |||||||||||||
| C000130154_1_AdditionalIndexMember_AsOf_2014Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 10,000 | |||||||||||||
| C000130154_1_AdditionalIndexMember_AsOf_2015Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 9,782 | |||||||||||||
| C000130154_1_AdditionalIndexMember_AsOf_2016Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 11,811 | |||||||||||||
| C000130154_1_AdditionalIndexMember_AsOf_2017Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 13,730 | |||||||||||||
| C000130154_1_AdditionalIndexMember_AsOf_2018Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 12,208 | |||||||||||||
| C000130154_1_AdditionalIndexMember_AsOf_2019Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 15,407 | |||||||||||||
| C000130154_1_AdditionalIndexMember_AsOf_2020Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 17,511 | |||||||||||||
| C000130154_1_AdditionalIndexMember_AsOf_2021Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 21,847 | |||||||||||||
| C000130154_1_AdditionalIndexMember_AsOf_2022Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 18,993 | |||||||||||||
| C000130154_1_AdditionalIndexMember_AsOf_2023Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 22,115 | |||||||||||||
| C000130154_1_AdditionalIndexMember_AsOf_2024Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 25,196 | 25,196 | 25,196 | $ 25,196 | ||||||||||
| C000130154_LG_2_AdditionalIndexMember_11YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Russell 3000® Index</span>" id="sjs-E122"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Russell 3000® Index</span> | |||||||||||||
| C000130154_2_AdditionalIndexMember_AsOf_2014Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 10,000 | |||||||||||||
| C000130154_2_AdditionalIndexMember_AsOf_2015Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 10,048 | |||||||||||||
| C000130154_2_AdditionalIndexMember_AsOf_2016Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 11,327 | |||||||||||||
| C000130154_2_AdditionalIndexMember_AsOf_2017Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 13,721 | |||||||||||||
| C000130154_2_AdditionalIndexMember_AsOf_2018Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 13,002 | |||||||||||||
| C000130154_2_AdditionalIndexMember_AsOf_2019Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 17,035 | |||||||||||||
| C000130154_2_AdditionalIndexMember_AsOf_2020Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 20,593 | |||||||||||||
| C000130154_2_AdditionalIndexMember_AsOf_2021Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 25,877 | |||||||||||||
| C000130154_2_AdditionalIndexMember_AsOf_2022Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 20,907 | |||||||||||||
| C000130154_2_AdditionalIndexMember_AsOf_2023Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 26,334 | |||||||||||||
| C000130154_2_AdditionalIndexMember_AsOf_2024Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 32,604 | $ 32,604 | $ 32,604 | $ 32,604 | ||||||||||
| C000130154_NoLoadClassMember_1YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 17.35% | |||||||||||||
| C000130154_NoLoadClassMember_5YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 11.44% | |||||||||||||
| C000130154_NoLoadClassMember_10YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 9.24% | |||||||||||||
| C000130154_0_AdditionalIndexMember_1YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 13.93% | |||||||||||||
| C000130154_0_AdditionalIndexMember_5YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 10.34% | |||||||||||||
| C000130154_0_AdditionalIndexMember_10YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 9.68% | |||||||||||||
| C000048876_LG_ClassMember_11YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Class C</span>" id="sjs-E176"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Class C</span> | |||||||||||||
| C000048876_ClassMember_AsOf_2014Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 10,000 | |||||||||||||
| C000048876_ClassMember_AsOf_2015Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 9,743 | |||||||||||||
| C000048876_ClassMember_AsOf_2016Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 10,789 | |||||||||||||
| C000048876_ClassMember_AsOf_2017Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 12,867 | |||||||||||||
| C000048876_ClassMember_AsOf_2018Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 10,844 | |||||||||||||
| C000048876_ClassMember_AsOf_2019Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 13,272 | |||||||||||||
| C000048876_ClassMember_AsOf_2020Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 15,576 | |||||||||||||
| C000048876_ClassMember_AsOf_2021Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 19,300 | |||||||||||||
| C000048876_ClassMember_AsOf_2022Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 16,268 | |||||||||||||
| C000048876_ClassMember_AsOf_2023Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 18,660 | |||||||||||||
| C000048876_ClassMember_AsOf_2024Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 21,817 | $ 21,817 | $ 21,817 | $ 21,817 | ||||||||||
| C000048876_LG_1_AdditionalIndexMember_11YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | S&P MidCap 400® Index</span>" id="sjs-E212"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">S&P MidCap 400® Index</span> | |||||||||||||
| C000048876_1_AdditionalIndexMember_AsOf_2014Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 10,000 | |||||||||||||
| C000048876_1_AdditionalIndexMember_AsOf_2015Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 9,782 | |||||||||||||
| C000048876_1_AdditionalIndexMember_AsOf_2016Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 11,811 | |||||||||||||
| C000048876_1_AdditionalIndexMember_AsOf_2017Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 13,730 | |||||||||||||
| C000048876_1_AdditionalIndexMember_AsOf_2018Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 12,208 | |||||||||||||
| C000048876_1_AdditionalIndexMember_AsOf_2019Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 15,407 | |||||||||||||
| C000048876_1_AdditionalIndexMember_AsOf_2020Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 17,511 | |||||||||||||
| C000048876_1_AdditionalIndexMember_AsOf_2021Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 21,847 | |||||||||||||
| C000048876_1_AdditionalIndexMember_AsOf_2022Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 18,993 | |||||||||||||
| C000048876_1_AdditionalIndexMember_AsOf_2023Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 22,115 | |||||||||||||
| C000048876_1_AdditionalIndexMember_AsOf_2024Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 25,196 | 25,196 | 25,196 | $ 25,196 | ||||||||||
| C000048876_LG_2_AdditionalIndexMember_11YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Russell 3000® Index</span>" id="sjs-E248"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Russell 3000® Index</span> | |||||||||||||
| C000048876_2_AdditionalIndexMember_AsOf_2014Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 10,000 | |||||||||||||
| C000048876_2_AdditionalIndexMember_AsOf_2015Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 10,048 | |||||||||||||
| C000048876_2_AdditionalIndexMember_AsOf_2016Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 11,327 | |||||||||||||
| C000048876_2_AdditionalIndexMember_AsOf_2017Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 13,721 | |||||||||||||
| C000048876_2_AdditionalIndexMember_AsOf_2018Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 13,002 | |||||||||||||
| C000048876_2_AdditionalIndexMember_AsOf_2019Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 17,035 | |||||||||||||
| C000048876_2_AdditionalIndexMember_AsOf_2020Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 20,593 | |||||||||||||
| C000048876_2_AdditionalIndexMember_AsOf_2021Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 25,877 | |||||||||||||
| C000048876_2_AdditionalIndexMember_AsOf_2022Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 20,907 | |||||||||||||
| C000048876_2_AdditionalIndexMember_AsOf_2023Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 26,334 | |||||||||||||
| C000048876_2_AdditionalIndexMember_AsOf_2024Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 32,604 | $ 32,604 | $ 32,604 | $ 32,604 | ||||||||||
| C000048876_ClassMember_1YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 15.08% | |||||||||||||
| C000048876_ClassMember_5YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 10.11% | |||||||||||||
| C000048876_ClassMember_10YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 8.11% | |||||||||||||
| C000048876_NoLoadClassMember_1YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 16.08% | |||||||||||||
| C000048876_NoLoadClassMember_5YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 10.11% | |||||||||||||
| C000048876_NoLoadClassMember_10YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 8.11% | |||||||||||||
| C000048876_0_AdditionalIndexMember_1YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 13.93% | |||||||||||||
| C000048876_0_AdditionalIndexMember_5YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 10.34% | |||||||||||||
| C000048876_0_AdditionalIndexMember_10YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 9.68% | |||||||||||||
| C000048874_LG_ClassMember_11YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Class A</span>" id="sjs-E311"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Class A</span> | |||||||||||||
| C000048874_ClassMember_AsOf_2014Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 9,425 | |||||||||||||
| C000048874_ClassMember_AsOf_2015Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 9,251 | |||||||||||||
| C000048874_ClassMember_AsOf_2016Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 10,324 | |||||||||||||
| C000048874_ClassMember_AsOf_2017Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 12,414 | |||||||||||||
| C000048874_ClassMember_AsOf_2018Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 10,540 | |||||||||||||
| C000048874_ClassMember_AsOf_2019Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 12,997 | |||||||||||||
| C000048874_ClassMember_AsOf_2020Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 15,381 | |||||||||||||
| C000048874_ClassMember_AsOf_2021Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 19,214 | |||||||||||||
| C000048874_ClassMember_AsOf_2022Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 16,328 | |||||||||||||
| C000048874_ClassMember_AsOf_2023Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 18,729 | |||||||||||||
| C000048874_ClassMember_AsOf_2024Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 21,898 | $ 21,898 | $ 21,898 | $ 21,898 | ||||||||||
| C000048874_LG_1_AdditionalIndexMember_11YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | S&P MidCap 400® Index</span>" id="sjs-E347"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">S&P MidCap 400® Index</span> | |||||||||||||
| C000048874_1_AdditionalIndexMember_AsOf_2014Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 10,000 | |||||||||||||
| C000048874_1_AdditionalIndexMember_AsOf_2015Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 9,782 | |||||||||||||
| C000048874_1_AdditionalIndexMember_AsOf_2016Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 11,811 | |||||||||||||
| C000048874_1_AdditionalIndexMember_AsOf_2017Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 13,730 | |||||||||||||
| C000048874_1_AdditionalIndexMember_AsOf_2018Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 12,208 | |||||||||||||
| C000048874_1_AdditionalIndexMember_AsOf_2019Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 15,407 | |||||||||||||
| C000048874_1_AdditionalIndexMember_AsOf_2020Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 17,511 | |||||||||||||
| C000048874_1_AdditionalIndexMember_AsOf_2021Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 21,847 | |||||||||||||
| C000048874_1_AdditionalIndexMember_AsOf_2022Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 18,993 | |||||||||||||
| C000048874_1_AdditionalIndexMember_AsOf_2023Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 22,115 | |||||||||||||
| C000048874_1_AdditionalIndexMember_AsOf_2024Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 25,196 | 25,196 | 25,196 | $ 25,196 | ||||||||||
| C000048874_LG_2_AdditionalIndexMember_11YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Russell 3000® Index</span>" id="sjs-E383"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Russell 3000® Index</span> | |||||||||||||
| C000048874_2_AdditionalIndexMember_AsOf_2014Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 10,000 | |||||||||||||
| C000048874_2_AdditionalIndexMember_AsOf_2015Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 10,048 | |||||||||||||
| C000048874_2_AdditionalIndexMember_AsOf_2016Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 11,327 | |||||||||||||
| C000048874_2_AdditionalIndexMember_AsOf_2017Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 13,721 | |||||||||||||
| C000048874_2_AdditionalIndexMember_AsOf_2018Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 13,002 | |||||||||||||
| C000048874_2_AdditionalIndexMember_AsOf_2019Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 17,035 | |||||||||||||
| C000048874_2_AdditionalIndexMember_AsOf_2020Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 20,593 | |||||||||||||
| C000048874_2_AdditionalIndexMember_AsOf_2021Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 25,877 | |||||||||||||
| C000048874_2_AdditionalIndexMember_AsOf_2022Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 20,907 | |||||||||||||
| C000048874_2_AdditionalIndexMember_AsOf_2023Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 26,334 | |||||||||||||
| C000048874_2_AdditionalIndexMember_AsOf_2024Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 32,604 | $ 32,604 | $ 32,604 | $ 32,604 | ||||||||||
| C000048874_ClassMember_1YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 10.20% | |||||||||||||
| C000048874_ClassMember_5YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 9.69% | |||||||||||||
| C000048874_ClassMember_10YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 8.15% | |||||||||||||
| C000048874_NoLoadClassMember_1YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 16.92% | |||||||||||||
| C000048874_NoLoadClassMember_5YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 11% | |||||||||||||
| C000048874_NoLoadClassMember_10YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 8.80% | |||||||||||||
| C000048874_0_AdditionalIndexMember_1YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 13.93% | |||||||||||||
| C000048874_0_AdditionalIndexMember_5YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 10.34% | |||||||||||||
| C000048874_0_AdditionalIndexMember_10YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 9.68% | |||||||||||||
| C000048877_LG_ClassMember_11YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Class M</span>" id="sjs-E446"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Class M</span> | |||||||||||||
| C000048877_ClassMember_AsOf_2014Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 9,650 | |||||||||||||
| C000048877_ClassMember_AsOf_2015Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 9,453 | |||||||||||||
| C000048877_ClassMember_AsOf_2016Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 10,523 | |||||||||||||
| C000048877_ClassMember_AsOf_2017Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 12,618 | |||||||||||||
| C000048877_ClassMember_AsOf_2018Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 10,693 | |||||||||||||
| C000048877_ClassMember_AsOf_2019Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 13,155 | |||||||||||||
| C000048877_ClassMember_AsOf_2020Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 15,530 | |||||||||||||
| C000048877_ClassMember_AsOf_2021Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 19,347 | |||||||||||||
| C000048877_ClassMember_AsOf_2022Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 16,408 | |||||||||||||
| C000048877_ClassMember_AsOf_2023Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 18,773 | |||||||||||||
| C000048877_ClassMember_AsOf_2024Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 21,888 | $ 21,888 | $ 21,888 | $ 21,888 | ||||||||||
| C000048877_LG_1_AdditionalIndexMember_11YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | S&P MidCap 400® Index</span>" id="sjs-E482"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">S&P MidCap 400® Index</span> | |||||||||||||
| C000048877_1_AdditionalIndexMember_AsOf_2014Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 10,000 | |||||||||||||
| C000048877_1_AdditionalIndexMember_AsOf_2015Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 9,782 | |||||||||||||
| C000048877_1_AdditionalIndexMember_AsOf_2016Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 11,811 | |||||||||||||
| C000048877_1_AdditionalIndexMember_AsOf_2017Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 13,730 | |||||||||||||
| C000048877_1_AdditionalIndexMember_AsOf_2018Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 12,208 | |||||||||||||
| C000048877_1_AdditionalIndexMember_AsOf_2019Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 15,407 | |||||||||||||
| C000048877_1_AdditionalIndexMember_AsOf_2020Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 17,511 | |||||||||||||
| C000048877_1_AdditionalIndexMember_AsOf_2021Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 21,847 | |||||||||||||
| C000048877_1_AdditionalIndexMember_AsOf_2022Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 18,993 | |||||||||||||
| C000048877_1_AdditionalIndexMember_AsOf_2023Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 22,115 | |||||||||||||
| C000048877_1_AdditionalIndexMember_AsOf_2024Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 25,196 | 25,196 | 25,196 | $ 25,196 | ||||||||||
| C000048877_LG_2_AdditionalIndexMember_11YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Russell 3000® Index</span>" id="sjs-E518"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Russell 3000® Index</span> | |||||||||||||
| C000048877_2_AdditionalIndexMember_AsOf_2014Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 10,000 | |||||||||||||
| C000048877_2_AdditionalIndexMember_AsOf_2015Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 10,048 | |||||||||||||
| C000048877_2_AdditionalIndexMember_AsOf_2016Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 11,327 | |||||||||||||
| C000048877_2_AdditionalIndexMember_AsOf_2017Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 13,721 | |||||||||||||
| C000048877_2_AdditionalIndexMember_AsOf_2018Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 13,002 | |||||||||||||
| C000048877_2_AdditionalIndexMember_AsOf_2019Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 17,035 | |||||||||||||
| C000048877_2_AdditionalIndexMember_AsOf_2020Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 20,593 | |||||||||||||
| C000048877_2_AdditionalIndexMember_AsOf_2021Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 25,877 | |||||||||||||
| C000048877_2_AdditionalIndexMember_AsOf_2022Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 20,907 | |||||||||||||
| C000048877_2_AdditionalIndexMember_AsOf_2023Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 26,334 | |||||||||||||
| C000048877_2_AdditionalIndexMember_AsOf_2024Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 32,604 | $ 32,604 | $ 32,604 | $ 32,604 | ||||||||||
| C000048877_ClassMember_1YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 12.51% | |||||||||||||
| C000048877_ClassMember_5YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 9.93% | |||||||||||||
| C000048877_ClassMember_10YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 8.15% | |||||||||||||
| C000048877_NoLoadClassMember_1YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 16.59% | |||||||||||||
| C000048877_NoLoadClassMember_5YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 10.72% | |||||||||||||
| C000048877_NoLoadClassMember_10YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 8.53% | |||||||||||||
| C000048877_0_AdditionalIndexMember_1YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 13.93% | |||||||||||||
| C000048877_0_AdditionalIndexMember_5YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 10.34% | |||||||||||||
| C000048877_0_AdditionalIndexMember_10YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 9.68% | |||||||||||||
| C000048878_LG_ClassMember_11YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Class I</span>" id="sjs-E581"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Class I</span> | |||||||||||||
| C000048878_ClassMember_AsOf_2014Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 10,000 | |||||||||||||
| C000048878_ClassMember_AsOf_2015Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 9,848 | |||||||||||||
| C000048878_ClassMember_AsOf_2016Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 11,020 | |||||||||||||
| C000048878_ClassMember_AsOf_2017Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 13,285 | |||||||||||||
| C000048878_ClassMember_AsOf_2018Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 11,319 | |||||||||||||
| C000048878_ClassMember_AsOf_2019Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 13,995 | |||||||||||||
| C000048878_ClassMember_AsOf_2020Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 16,609 | |||||||||||||
| C000048878_ClassMember_AsOf_2021Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 20,801 | |||||||||||||
| C000048878_ClassMember_AsOf_2022Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 17,728 | |||||||||||||
| C000048878_ClassMember_AsOf_2023Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 20,392 | |||||||||||||
| C000048878_ClassMember_AsOf_2024Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 23,894 | $ 23,894 | $ 23,894 | $ 23,894 | ||||||||||
| C000048878_LG_1_AdditionalIndexMember_11YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | S&P MidCap 400® Index</span>" id="sjs-E617"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">S&P MidCap 400® Index</span> | |||||||||||||
| C000048878_1_AdditionalIndexMember_AsOf_2014Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 10,000 | |||||||||||||
| C000048878_1_AdditionalIndexMember_AsOf_2015Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 9,782 | |||||||||||||
| C000048878_1_AdditionalIndexMember_AsOf_2016Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 11,811 | |||||||||||||
| C000048878_1_AdditionalIndexMember_AsOf_2017Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 13,730 | |||||||||||||
| C000048878_1_AdditionalIndexMember_AsOf_2018Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 12,208 | |||||||||||||
| C000048878_1_AdditionalIndexMember_AsOf_2019Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 15,407 | |||||||||||||
| C000048878_1_AdditionalIndexMember_AsOf_2020Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 17,511 | |||||||||||||
| C000048878_1_AdditionalIndexMember_AsOf_2021Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 21,847 | |||||||||||||
| C000048878_1_AdditionalIndexMember_AsOf_2022Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 18,993 | |||||||||||||
| C000048878_1_AdditionalIndexMember_AsOf_2023Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 22,115 | |||||||||||||
| C000048878_1_AdditionalIndexMember_AsOf_2024Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | 25,196 | 25,196 | 25,196 | $ 25,196 | ||||||||||
| C000048878_LG_2_AdditionalIndexMember_11YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Line Graph and Table Measure Name | Russell 3000® Index</span>" id="sjs-E653"><span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Russell 3000® Index</span> | |||||||||||||
| C000048878_2_AdditionalIndexMember_AsOf_2014Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 10,000 | |||||||||||||
| C000048878_2_AdditionalIndexMember_AsOf_2015Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 10,048 | |||||||||||||
| C000048878_2_AdditionalIndexMember_AsOf_2016Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 11,327 | |||||||||||||
| C000048878_2_AdditionalIndexMember_AsOf_2017Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 13,721 | |||||||||||||
| C000048878_2_AdditionalIndexMember_AsOf_2018Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 13,002 | |||||||||||||
| C000048878_2_AdditionalIndexMember_AsOf_2019Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 17,035 | |||||||||||||
| C000048878_2_AdditionalIndexMember_AsOf_2020Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 20,593 | |||||||||||||
| C000048878_2_AdditionalIndexMember_AsOf_2021Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 25,877 | |||||||||||||
| C000048878_2_AdditionalIndexMember_AsOf_2022Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 20,907 | |||||||||||||
| C000048878_2_AdditionalIndexMember_AsOf_2023Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 26,334 | |||||||||||||
| C000048878_2_AdditionalIndexMember_AsOf_2024Member | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Account Value | $ 32,604 | $ 32,604 | $ 32,604 | $ 32,604 | ||||||||||
| C000048878_NoLoadClassMember_1YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 17.17% | |||||||||||||
| C000048878_NoLoadClassMember_5YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 11.29% | |||||||||||||
| C000048878_NoLoadClassMember_10YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 9.10% | |||||||||||||
| C000048878_0_AdditionalIndexMember_1YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 13.93% | |||||||||||||
| C000048878_0_AdditionalIndexMember_5YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 10.34% | |||||||||||||
| C000048878_0_AdditionalIndexMember_10YRMember | ||||||||||||||
| Account Value [Line Items] | ||||||||||||||
| Average Annual Return, Percent | 9.68% |
| Shareholder Report, Holdings (Details) | Dec. 31, 2024 |
| Fidelity Advisor Mid Cap II Fund - Class Z | TH0Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.50% |
| Fidelity Advisor Mid Cap II Fund - Class Z | TH1Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.40% |
| Fidelity Advisor Mid Cap II Fund - Class Z | TH2Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.40% |
| Fidelity Advisor Mid Cap II Fund - Class Z | TH3Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.30% |
| Fidelity Advisor Mid Cap II Fund - Class Z | TH4Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.30% |
| Fidelity Advisor Mid Cap II Fund - Class Z | TH5Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.30% |
| Fidelity Advisor Mid Cap II Fund - Class Z | TH6Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.20% |
| Fidelity Advisor Mid Cap II Fund - Class Z | TH7Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.20% |
| Fidelity Advisor Mid Cap II Fund - Class Z | TH8Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.20% |
| Fidelity Advisor Mid Cap II Fund - Class Z | TH9Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.20% |
| Fidelity Advisor Mid Cap II Fund - Class Z | MSFinancialsSectorMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 20.10% |
| Fidelity Advisor Mid Cap II Fund - Class Z | Information Technology Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 9.80% |
| Fidelity Advisor Mid Cap II Fund - Class Z | Healthcare Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 11.70% |
| Fidelity Advisor Mid Cap II Fund - Class Z | Real Estate Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.50% |
| Fidelity Advisor Mid Cap II Fund - Class Z | Industrial Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 18% |
| Fidelity Advisor Mid Cap II Fund - Class Z | Materials Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.20% |
| Fidelity Advisor Mid Cap II Fund - Class Z | Consumer Discretionary Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 12.30% |
| Fidelity Advisor Mid Cap II Fund - Class Z | Consumer Staples Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.90% |
| Fidelity Advisor Mid Cap II Fund - Class Z | Communications Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.80% |
| Fidelity Advisor Mid Cap II Fund - Class Z | Energy Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6% |
| Fidelity Advisor Mid Cap II Fund - Class Z | Utilities Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.40% |
| Fidelity Advisor Mid Cap II Fund - Class Z | United States | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 91.10% |
| Fidelity Advisor Mid Cap II Fund - Class Z | Canada | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.20% |
| Fidelity Advisor Mid Cap II Fund - Class Z | Israel | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.60% |
| Fidelity Advisor Mid Cap II Fund - Class Z | United Kingdom | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.60% |
| Fidelity Advisor Mid Cap II Fund - Class Z | Belgium | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.90% |
| Fidelity Advisor Mid Cap II Fund - Class Z | Puerto Rico | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.80% |
| Fidelity Advisor Mid Cap II Fund - Class Z | Brazil | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.40% |
| Fidelity Advisor Mid Cap II Fund - Class Z | Italy | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.40% |
| Fidelity Advisor Mid Cap II Fund - Class Z | France | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.30% |
| Fidelity Advisor Mid Cap II Fund - Class Z | OtherMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.70% |
| Fidelity Advisor Mid Cap II Fund - Class Z | AACommonStocksMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 99.70% |
| Fidelity Advisor Mid Cap II Fund - Class Z | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.30% |
| Fidelity Advisor Mid Cap II Fund - Class C | TH0Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.50% |
| Fidelity Advisor Mid Cap II Fund - Class C | TH1Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.40% |
| Fidelity Advisor Mid Cap II Fund - Class C | TH2Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.40% |
| Fidelity Advisor Mid Cap II Fund - Class C | TH3Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.30% |
| Fidelity Advisor Mid Cap II Fund - Class C | TH4Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.30% |
| Fidelity Advisor Mid Cap II Fund - Class C | TH5Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.30% |
| Fidelity Advisor Mid Cap II Fund - Class C | TH6Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.20% |
| Fidelity Advisor Mid Cap II Fund - Class C | TH7Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.20% |
| Fidelity Advisor Mid Cap II Fund - Class C | TH8Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.20% |
| Fidelity Advisor Mid Cap II Fund - Class C | TH9Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.20% |
| Fidelity Advisor Mid Cap II Fund - Class C | MSFinancialsSectorMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 20.10% |
| Fidelity Advisor Mid Cap II Fund - Class C | Information Technology Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 9.80% |
| Fidelity Advisor Mid Cap II Fund - Class C | Healthcare Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 11.70% |
| Fidelity Advisor Mid Cap II Fund - Class C | Real Estate Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.50% |
| Fidelity Advisor Mid Cap II Fund - Class C | Industrial Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 18% |
| Fidelity Advisor Mid Cap II Fund - Class C | Materials Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.20% |
| Fidelity Advisor Mid Cap II Fund - Class C | Consumer Discretionary Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 12.30% |
| Fidelity Advisor Mid Cap II Fund - Class C | Consumer Staples Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.90% |
| Fidelity Advisor Mid Cap II Fund - Class C | Communications Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.80% |
| Fidelity Advisor Mid Cap II Fund - Class C | Energy Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6% |
| Fidelity Advisor Mid Cap II Fund - Class C | Utilities Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.40% |
| Fidelity Advisor Mid Cap II Fund - Class C | United States | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 91.10% |
| Fidelity Advisor Mid Cap II Fund - Class C | Canada | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.20% |
| Fidelity Advisor Mid Cap II Fund - Class C | Israel | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.60% |
| Fidelity Advisor Mid Cap II Fund - Class C | United Kingdom | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.60% |
| Fidelity Advisor Mid Cap II Fund - Class C | Belgium | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.90% |
| Fidelity Advisor Mid Cap II Fund - Class C | Puerto Rico | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.80% |
| Fidelity Advisor Mid Cap II Fund - Class C | Brazil | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.40% |
| Fidelity Advisor Mid Cap II Fund - Class C | Italy | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.40% |
| Fidelity Advisor Mid Cap II Fund - Class C | France | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.30% |
| Fidelity Advisor Mid Cap II Fund - Class C | OtherMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.70% |
| Fidelity Advisor Mid Cap II Fund - Class C | AACommonStocksMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 99.70% |
| Fidelity Advisor Mid Cap II Fund - Class C | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.30% |
| Fidelity Advisor Mid Cap II Fund - Class A | TH0Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.50% |
| Fidelity Advisor Mid Cap II Fund - Class A | TH1Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.40% |
| Fidelity Advisor Mid Cap II Fund - Class A | TH2Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.40% |
| Fidelity Advisor Mid Cap II Fund - Class A | TH3Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.30% |
| Fidelity Advisor Mid Cap II Fund - Class A | TH4Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.30% |
| Fidelity Advisor Mid Cap II Fund - Class A | TH5Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.30% |
| Fidelity Advisor Mid Cap II Fund - Class A | TH6Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.20% |
| Fidelity Advisor Mid Cap II Fund - Class A | TH7Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.20% |
| Fidelity Advisor Mid Cap II Fund - Class A | TH8Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.20% |
| Fidelity Advisor Mid Cap II Fund - Class A | TH9Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.20% |
| Fidelity Advisor Mid Cap II Fund - Class A | MSFinancialsSectorMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 20.10% |
| Fidelity Advisor Mid Cap II Fund - Class A | Information Technology Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 9.80% |
| Fidelity Advisor Mid Cap II Fund - Class A | Healthcare Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 11.70% |
| Fidelity Advisor Mid Cap II Fund - Class A | Real Estate Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.50% |
| Fidelity Advisor Mid Cap II Fund - Class A | Industrial Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 18% |
| Fidelity Advisor Mid Cap II Fund - Class A | Materials Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.20% |
| Fidelity Advisor Mid Cap II Fund - Class A | Consumer Discretionary Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 12.30% |
| Fidelity Advisor Mid Cap II Fund - Class A | Consumer Staples Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.90% |
| Fidelity Advisor Mid Cap II Fund - Class A | Communications Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.80% |
| Fidelity Advisor Mid Cap II Fund - Class A | Energy Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6% |
| Fidelity Advisor Mid Cap II Fund - Class A | Utilities Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.40% |
| Fidelity Advisor Mid Cap II Fund - Class A | United States | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 91.10% |
| Fidelity Advisor Mid Cap II Fund - Class A | Canada | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.20% |
| Fidelity Advisor Mid Cap II Fund - Class A | Israel | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.60% |
| Fidelity Advisor Mid Cap II Fund - Class A | United Kingdom | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.60% |
| Fidelity Advisor Mid Cap II Fund - Class A | Belgium | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.90% |
| Fidelity Advisor Mid Cap II Fund - Class A | Puerto Rico | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.80% |
| Fidelity Advisor Mid Cap II Fund - Class A | Brazil | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.40% |
| Fidelity Advisor Mid Cap II Fund - Class A | Italy | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.40% |
| Fidelity Advisor Mid Cap II Fund - Class A | France | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.30% |
| Fidelity Advisor Mid Cap II Fund - Class A | OtherMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.70% |
| Fidelity Advisor Mid Cap II Fund - Class A | AACommonStocksMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 99.70% |
| Fidelity Advisor Mid Cap II Fund - Class A | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.30% |
| Fidelity Advisor Mid Cap II Fund - Class M | TH0Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.50% |
| Fidelity Advisor Mid Cap II Fund - Class M | TH1Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.40% |
| Fidelity Advisor Mid Cap II Fund - Class M | TH2Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.40% |
| Fidelity Advisor Mid Cap II Fund - Class M | TH3Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.30% |
| Fidelity Advisor Mid Cap II Fund - Class M | TH4Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.30% |
| Fidelity Advisor Mid Cap II Fund - Class M | TH5Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.30% |
| Fidelity Advisor Mid Cap II Fund - Class M | TH6Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.20% |
| Fidelity Advisor Mid Cap II Fund - Class M | TH7Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.20% |
| Fidelity Advisor Mid Cap II Fund - Class M | TH8Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.20% |
| Fidelity Advisor Mid Cap II Fund - Class M | TH9Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.20% |
| Fidelity Advisor Mid Cap II Fund - Class M | MSFinancialsSectorMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 20.10% |
| Fidelity Advisor Mid Cap II Fund - Class M | Information Technology Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 9.80% |
| Fidelity Advisor Mid Cap II Fund - Class M | Healthcare Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 11.70% |
| Fidelity Advisor Mid Cap II Fund - Class M | Real Estate Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.50% |
| Fidelity Advisor Mid Cap II Fund - Class M | Industrial Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 18% |
| Fidelity Advisor Mid Cap II Fund - Class M | Materials Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.20% |
| Fidelity Advisor Mid Cap II Fund - Class M | Consumer Discretionary Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 12.30% |
| Fidelity Advisor Mid Cap II Fund - Class M | Consumer Staples Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.90% |
| Fidelity Advisor Mid Cap II Fund - Class M | Communications Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.80% |
| Fidelity Advisor Mid Cap II Fund - Class M | Energy Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6% |
| Fidelity Advisor Mid Cap II Fund - Class M | Utilities Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.40% |
| Fidelity Advisor Mid Cap II Fund - Class M | United States | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 91.10% |
| Fidelity Advisor Mid Cap II Fund - Class M | Canada | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.20% |
| Fidelity Advisor Mid Cap II Fund - Class M | Israel | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.60% |
| Fidelity Advisor Mid Cap II Fund - Class M | United Kingdom | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.60% |
| Fidelity Advisor Mid Cap II Fund - Class M | Belgium | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.90% |
| Fidelity Advisor Mid Cap II Fund - Class M | Puerto Rico | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.80% |
| Fidelity Advisor Mid Cap II Fund - Class M | Brazil | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.40% |
| Fidelity Advisor Mid Cap II Fund - Class M | Italy | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.40% |
| Fidelity Advisor Mid Cap II Fund - Class M | France | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.30% |
| Fidelity Advisor Mid Cap II Fund - Class M | OtherMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.70% |
| Fidelity Advisor Mid Cap II Fund - Class M | AACommonStocksMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 99.70% |
| Fidelity Advisor Mid Cap II Fund - Class M | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.30% |
| Fidelity Advisor Mid Cap II Fund - Class I | TH0Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.50% |
| Fidelity Advisor Mid Cap II Fund - Class I | TH1Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.40% |
| Fidelity Advisor Mid Cap II Fund - Class I | TH2Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.40% |
| Fidelity Advisor Mid Cap II Fund - Class I | TH3Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.30% |
| Fidelity Advisor Mid Cap II Fund - Class I | TH4Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.30% |
| Fidelity Advisor Mid Cap II Fund - Class I | TH5Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.30% |
| Fidelity Advisor Mid Cap II Fund - Class I | TH6Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.20% |
| Fidelity Advisor Mid Cap II Fund - Class I | TH7Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.20% |
| Fidelity Advisor Mid Cap II Fund - Class I | TH8Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.20% |
| Fidelity Advisor Mid Cap II Fund - Class I | TH9Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.20% |
| Fidelity Advisor Mid Cap II Fund - Class I | MSFinancialsSectorMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 20.10% |
| Fidelity Advisor Mid Cap II Fund - Class I | Information Technology Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 9.80% |
| Fidelity Advisor Mid Cap II Fund - Class I | Healthcare Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 11.70% |
| Fidelity Advisor Mid Cap II Fund - Class I | Real Estate Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6.50% |
| Fidelity Advisor Mid Cap II Fund - Class I | Industrial Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 18% |
| Fidelity Advisor Mid Cap II Fund - Class I | Materials Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 5.20% |
| Fidelity Advisor Mid Cap II Fund - Class I | Consumer Discretionary Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 12.30% |
| Fidelity Advisor Mid Cap II Fund - Class I | Consumer Staples Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 4.90% |
| Fidelity Advisor Mid Cap II Fund - Class I | Communications Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.80% |
| Fidelity Advisor Mid Cap II Fund - Class I | Energy Sector | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 6% |
| Fidelity Advisor Mid Cap II Fund - Class I | Utilities Sector Member | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 3.40% |
| Fidelity Advisor Mid Cap II Fund - Class I | United States | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 91.10% |
| Fidelity Advisor Mid Cap II Fund - Class I | Canada | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 2.20% |
| Fidelity Advisor Mid Cap II Fund - Class I | Israel | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.60% |
| Fidelity Advisor Mid Cap II Fund - Class I | United Kingdom | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 1.60% |
| Fidelity Advisor Mid Cap II Fund - Class I | Belgium | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.90% |
| Fidelity Advisor Mid Cap II Fund - Class I | Puerto Rico | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.80% |
| Fidelity Advisor Mid Cap II Fund - Class I | Brazil | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.40% |
| Fidelity Advisor Mid Cap II Fund - Class I | Italy | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.40% |
| Fidelity Advisor Mid Cap II Fund - Class I | France | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.30% |
| Fidelity Advisor Mid Cap II Fund - Class I | OtherMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.70% |
| Fidelity Advisor Mid Cap II Fund - Class I | AACommonStocksMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 99.70% |
| Fidelity Advisor Mid Cap II Fund - Class I | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember | |
| Holdings [Line Items] | |
| Percent of Net Asset Value | 0.30% |
