v3.25.2
Risk/Return Detail Data - FidelityLargeCapStockFund-AMCIZPRO - USD ($)
 12 Months Ended 60 Months Ended 120 Months Ended
Jul. 25, 2025
Jul. 25, 2025
Dec. 31, 2024
Dec. 31, 2023
Dec. 31, 2022
Dec. 31, 2021
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Jul. 25, 2025
Jul. 25, 2025
FidelityLargeCapStockFund-AMCIZPRO | Fidelity Large Cap Stock Fund | Fidelity Advisor Large Cap Stock Fund - Class A                            
Prospectus Line Items                            
Maximum Cumulative Sales Charge (as a percentage of Offering Price) 5.75%                          
Maximum Deferred Sales Charge (as a percentage) [1] 0.00%                          
Management Fees (as a percentage of Assets) [2],[3] 0.76%                          
Distribution and Service (12b-1) Fees 0.25%                          
Other Expenses (as a percentage of Assets): [3] 0.01%                          
Expenses (as a percentage of Assets) 1.02%                          
Expense Example, with Redemption, 1 Year $ 673                          
Expense Example, with Redemption, 3 Years 881                          
Expense Example, with Redemption, 5 Years 1,106                          
Expense Example, with Redemption, 10 Years 1,751                          
Expense Example, No Redemption, 1 Year 673                          
Expense Example, No Redemption, 3 Years 881                          
Expense Example, No Redemption, 5 Years 1,106                          
Expense Example, No Redemption, 10 Years $ 1,751                          
Average Annual Return, Label [Optional Text]   Return Before Taxes                        
Average Annual Return, Percent   26.28%                     14.52% 12.13%
Annual Return [Percent]     26.28% 23.52% (7.95%) 25.83% 9.00% 31.55% (9.15%) 18.15% 16.70% (3.17%)    
FidelityLargeCapStockFund-AMCIZPRO | Fidelity Large Cap Stock Fund | Fidelity Advisor Large Cap Stock Fund - Class M                            
Prospectus Line Items                            
Maximum Cumulative Sales Charge (as a percentage of Offering Price) 3.50%                          
Maximum Deferred Sales Charge (as a percentage) [1] 0.00%                          
Management Fees (as a percentage of Assets) [2],[3] 0.76%                          
Distribution and Service (12b-1) Fees 0.50%                          
Other Expenses (as a percentage of Assets): [3] 0.01%                          
Expenses (as a percentage of Assets) 1.27%                          
Expense Example, with Redemption, 1 Year $ 475                          
Expense Example, with Redemption, 3 Years 739                          
Expense Example, with Redemption, 5 Years 1,023                          
Expense Example, with Redemption, 10 Years 1,830                          
Expense Example, No Redemption, 1 Year 475                          
Expense Example, No Redemption, 3 Years 739                          
Expense Example, No Redemption, 5 Years 1,023                          
Expense Example, No Redemption, 10 Years $ 1,830                          
FidelityLargeCapStockFund-AMCIZPRO | Fidelity Large Cap Stock Fund | Fidelity Advisor Large Cap Stock Fund - Class C                            
Prospectus Line Items                            
Maximum Cumulative Sales Charge (as a percentage of Offering Price) 0.00%                          
Maximum Deferred Sales Charge (as a percentage) [4] 1.00%                          
Management Fees (as a percentage of Assets) [2],[3] 0.76%                          
Distribution and Service (12b-1) Fees 1.00%                          
Other Expenses (as a percentage of Assets): [3] 0.01%                          
Expenses (as a percentage of Assets) 1.77%                          
Expenses Deferred Charges [Text Block] On Class C shares redeemed less than one year after purchase.                          
Expense Example, with Redemption, 1 Year $ 280                          
Expense Example, with Redemption, 3 Years 557                          
Expense Example, with Redemption, 5 Years 959                          
Expense Example, with Redemption, 10 Years 1,886                          
Expense Example, No Redemption, 1 Year 180                          
Expense Example, No Redemption, 3 Years 557                          
Expense Example, No Redemption, 5 Years 959                          
Expense Example, No Redemption, 10 Years $ 1,886                          
FidelityLargeCapStockFund-AMCIZPRO | Fidelity Large Cap Stock Fund | Fidelity Advisor Large Cap Stock Fund - Class I                            
Prospectus Line Items                            
Maximum Cumulative Sales Charge (as a percentage of Offering Price) 0.00%                          
Maximum Deferred Sales Charge (as a percentage) 0.00%                          
Management Fees (as a percentage of Assets) [2],[3] 0.76%                          
Distribution and Service (12b-1) Fees 0.00%                          
Other Expenses (as a percentage of Assets): [3] 0.01%                          
Expenses (as a percentage of Assets) 0.77%                          
Expense Example, with Redemption, 1 Year $ 79                          
Expense Example, with Redemption, 3 Years 246                          
Expense Example, with Redemption, 5 Years 428                          
Expense Example, with Redemption, 10 Years 954                          
Expense Example, No Redemption, 1 Year 79                          
Expense Example, No Redemption, 3 Years 246                          
Expense Example, No Redemption, 5 Years 428                          
Expense Example, No Redemption, 10 Years $ 954                          
FidelityLargeCapStockFund-AMCIZPRO | Fidelity Large Cap Stock Fund | Fidelity Advisor Large Cap Stock Fund - Class Z                            
Prospectus Line Items                            
Maximum Cumulative Sales Charge (as a percentage of Offering Price) 0.00%                          
Maximum Deferred Sales Charge (as a percentage) 0.00%                          
Management Fees (as a percentage of Assets) [2],[3] 0.65%                          
Distribution and Service (12b-1) Fees 0.00%                          
Other Expenses (as a percentage of Assets): [3] 0.01%                          
Expenses (as a percentage of Assets) 0.66%                          
Expense Example, with Redemption, 1 Year $ 67                          
Expense Example, with Redemption, 3 Years 211                          
Expense Example, with Redemption, 5 Years 368                          
Expense Example, with Redemption, 10 Years 822                          
Expense Example, No Redemption, 1 Year 67                          
Expense Example, No Redemption, 3 Years 211                          
Expense Example, No Redemption, 5 Years 368                          
Expense Example, No Redemption, 10 Years $ 822                          
FidelityLargeCapStockFund-AMCIZPRO | Fidelity Large Cap Stock Fund                            
Prospectus Line Items                            
Risk/Return [Heading] Fund Summary Fund /Class: Fidelity® Large Cap Stock Fund /Fidelity Advisor® Large Cap Stock Fund A, M, C, I, Z                            
Objective [Heading] Investment Objective                          
Objective, Primary [Text Block] Fidelity® Large Cap Stock Fund seeks long-term growth of capital.                          
Expense Heading [Optional Text] Fee Table                          
Expense Narrative [Text Block] The following table describes the fees and expenses that may be incurred when you buy, hold, and sell shares of the fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $ 50,000 in the fund or certain other Fidelity ® funds. More information about these and other discounts is available from your investment professional and in the "Fund Distribution" section beginning on page 19 of the prospectus and in the sales charge waiver appendix to the prospectus.                          
Shareholder Fees Caption [Optional Text] Shareholder fees                          
Operating Expenses Caption [Optional Text] Annual Operating Expenses                          
Portfolio Turnover [Heading] Portfolio Turnover                          
Portfolio Turnover [Text Block] The fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when fund shares are held in a taxable account. These costs, which are not reflected in annual operating expenses or in the example, affect the fund's performance. During the most recent fiscal year, the fund's portfolio turnover rate was 17 % of the average value of its portfolio.                          
Portfolio Turnover, Rate 17.00%                          
Expenses Deferred Charges [Text Block] Class A and Class M purchases of $1 million or more will not be subject to a front-end sales charge. Such Class A and Class M purchases may be subject, upon redemption, to a contingent deferred sales charge (CDSC) of 1.00% and 0.25%, respectively.                          
Expense Breakpoint Discounts [Text] You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $ 50,000 in the fund or certain other Fidelity ® funds. More information about these and other discounts is available from your investment professional and in the "Fund Distribution" section beginning on page 19 of the prospectus                          
Expense Breakpoint, Minimum Investment Required [Amount] $ 50,000                          
Other Expenses, New Fund, Based on Estimates [Text] Based on estimated amounts for the current fiscal year.                          
Expense Example Narrative [Text Block] This example helps compare the cost of investing in the fund with the cost of investing in other funds. Let's say, hypothetically, that the annual return for shares of the fund is 5% and that the fees and the annual operating expenses for shares of the fund are exactly as described in the fee table. This example illustrates the effect of fees and expenses, but is not meant to suggest actual or expected fees and expenses or returns, all of which may vary. For every $10,000 you invested, here's how much you would pay in total expenses if you sell all of your shares at the end of each time period indicated and if you hold your shares:                          
Strategy [Heading] Principal Investment Strategies                          
Strategy Narrative [Text Block] Normally investing at least 80% of assets in common stocks of companies with large market capitalizations. The Adviser generally defines large market capitalization companies as those whose market capitalization is similar to the market capitalization of companies in the Russell 1000 ® Index or the S&P 500 ® Index. Common stocks (including depositary receipts evidencing ownership of common stock) are a type of equity security that represents an ownership interest in an issuer. Effective December 11, 2025, derivative instruments that provide investment exposure to the investments above or exposure to one or more market risk factors associated with such investments are included in the fund's 80% policy, consistent with the fund's investment policies and limitations with respect to investments in derivatives. Investing in domestic and foreign issuers. Investing in either "growth" stocks or "value" stocks or both. Using fundamental analysis of factors such as each issuer's financial condition and industry position, as well as market and economic conditions, to select investments.                          
Bar Chart and Performance Table [Heading] Performance                          
Performance Narrative [Text Block] The following information is intended to help you understand the risks of investing in the fund. The information illustrates the changes in the performance of Fidelity® Large Cap Stock Fund, a class of shares of the fund, from year to year and compares the performance of this class to the performance of a securities market index over various periods of time. The index description appears in the "Additional Index Information" section of the prospectus. Past performance (before and after taxes) is not an indication of future performance . Visit www.fidelity.com for more recent performance information for Fidelity® Large Cap Stock Fund, a class of shares of the fund. Performance history will be available at institutional.fidelity.com for Class A, Class M, Class C, Class I, and Class Z after Class A, Class M, Class C, Class I, and Class Z have been in operation for one calendar year.                          
Performance Information Illustrates Variability of Returns [Text] The information illustrates the changes in the performance of Fidelity® Large Cap Stock Fund, a class of shares of the fund, from year to year and compares the performance of this class to the performance of a securities market index over various periods of time.                          
Performance One Year or Less [Text] Performance history will be available at institutional.fidelity.com for Class A, Class M, Class C, Class I, and Class Z after Class A, Class M, Class C, Class I, and Class Z have been in operation for one calendar year.                          
Performance Availability Website Address [Text] www.fidelity.com                          
Performance Past Does Not Indicate Future [Text] Past performance (before and after taxes) is not an indication of future performance                          
Bar Chart [Heading] Year-by-Year Returns                          
Bar Chart, Returns for Class Not Offered in Prospectus [Text] * The returns shown above are for Fidelity® Large Cap Stock Fund, a class of shares of the fund that is not offered through this prospectus. Class A, Class M, Class C, Class I, and Class Z   would have substantially similar annual returns to Fidelity® Large Cap Stock Fund because the classes are invested in the same portfolio of securities. Class A's, Class M's, Class C's, Class I's, and Class Z's   returns would differ from Fidelity® Large Cap Stock Fund's returns only to the extent that the classes do not have the same expenses.                          
Year to Date Return, Label [Optional Text]    Year-to-Date Return                          
Bar Chart, Year to Date Return, Date Jun. 30, 2025                          
Bar Chart, Year to Date Return 12.57%                          
Highest Quarterly Return, Label [Optional Text]    Highest Quarter Return                          
Highest Quarterly Return, Date Dec. 31, 2020                          
Highest Quarterly Return 19.07%                          
Lowest Quarterly Return, Label [Optional Text]    Lowest Quarter Return                          
Lowest Quarterly Return, Date Mar. 31, 2020                          
Lowest Quarterly Return (24.95%)                          
Performance Table Heading Average Annual Returns                          
Performance Table Uses Highest Federal Rate After-tax returns are calculated using the historical highest individual federal marginal income tax rates, but do not reflect the impact of state or local taxes.                          
Performance Table Not Relevant to Tax Deferred The after-tax returns shown are not relevant if you hold your shares in a retirement account or in another tax-deferred arrangement, such as an employee benefit plan (profit sharing, 401(k), or 403(b) plan).                          
Performance Table Explanation after Tax Higher Return After Taxes on Distributions and Sale of Fund Shares may be higher than other returns for the same period due to a tax benefit of realizing a capital loss upon the sale of fund shares.                          
Performance Table Narrative After-tax returns are calculated using the historical highest individual federal marginal income tax rates, but do not reflect the impact of state or local taxes. Actual after-tax returns may differ depending on your individual circumstances. The after-tax returns shown are not relevant if you hold your shares in a retirement account or in another tax-deferred arrangement, such as an employee benefit plan (profit sharing, 401(k), or 403(b) plan). Return After Taxes on Distributions and Sale of Fund Shares may be higher than other returns for the same period due to a tax benefit of realizing a capital loss upon the sale of fund shares.                          
FidelityLargeCapStockFund-AMCIZPRO | Fidelity Large Cap Stock Fund | After Taxes on Distributions | Fidelity Advisor Large Cap Stock Fund - Class A                            
Prospectus Line Items                            
Average Annual Return, Label [Optional Text]   Return After Taxes on Distributions                        
Average Annual Return, Percent   24.98%                     13.46% 10.84%
FidelityLargeCapStockFund-AMCIZPRO | Fidelity Large Cap Stock Fund | After Taxes on Distributions and Sales | Fidelity Advisor Large Cap Stock Fund - Class A                            
Prospectus Line Items                            
Average Annual Return, Label [Optional Text]   Return After Taxes on Distributions and Sale of Fund Shares                        
Average Annual Return, Percent   16.40%                     11.42% 9.61%
FidelityLargeCapStockFund-AMCIZPRO | Fidelity Large Cap Stock Fund | SP001                            
Prospectus Line Items                            
Average Annual Return, Label [Optional Text]   S&P 500® Index                        
Average Annual Return, Percent   25.02%                     14.53% 13.10%
Document Type 485BPOS                          
Registrant Name Fidelity Concord Street Trust                          
[1]
A Class A and Class M purchases of $1 million or more will not be subject to a front-end sales charge. Such Class A and Class M purchases may be subject, upon redemption, to a contingent deferred sales charge (CDSC) of 1.00% and 0.25%, respectively.
[2]
A The management fee comprises a basic fee, which may vary by class, that is adjusted up or down (subject to a maximum rate) based on the performance of the fund or a designated class of the fund relative to that of the S&P 500® Index. Please see "Fund Services - Fund Management - Advisory Fee(s)" for additional information.
[3]
B Based on estimated amounts for the current fiscal year.
[4]
B On Class C shares redeemed less than one year after purchase.