v3.25.2
Shareholder Report, Line Graph (Details) - USD ($)
12 Months Ended 84 Months Ended 108 Months Ended
Jun. 30, 2025
Jun. 30, 2025
Jun. 30, 2025
C000212599_LG_ClassMember_7YRMember      
Account Value [Line Items]      
Line Graph and Table Measure Name   <span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Fidelity® Small Cap Value Index Fund</span>  
C000212599_ClassMember_AsOf_2019Member      
Account Value [Line Items]      
Accumulated Value $ 10,000    
C000212599_ClassMember_AsOf_2020Member      
Account Value [Line Items]      
Accumulated Value 8,311    
C000212599_ClassMember_AsOf_2021Member      
Account Value [Line Items]      
Accumulated Value 14,387    
C000212599_ClassMember_AsOf_2022Member      
Account Value [Line Items]      
Accumulated Value 12,042    
C000212599_ClassMember_AsOf_2023Member      
Account Value [Line Items]      
Accumulated Value 12,781    
C000212599_ClassMember_AsOf_2024Member      
Account Value [Line Items]      
Accumulated Value 14,165    
C000212599_ClassMember_AsOf_2025Member      
Account Value [Line Items]      
Accumulated Value 14,979    
C000212599_LG_1_AdditionalIndexMember_7YRMember      
Account Value [Line Items]      
Line Graph and Table Measure Name   <span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Russell 2000® Value Index</span>  
C000212599_1_AdditionalIndexMember_AsOf_2019Member      
Account Value [Line Items]      
Accumulated Value 10,000    
C000212599_1_AdditionalIndexMember_AsOf_2020Member      
Account Value [Line Items]      
Accumulated Value 8,323    
C000212599_1_AdditionalIndexMember_AsOf_2021Member      
Account Value [Line Items]      
Accumulated Value 14,423    
C000212599_1_AdditionalIndexMember_AsOf_2022Member      
Account Value [Line Items]      
Accumulated Value 12,075    
C000212599_1_AdditionalIndexMember_AsOf_2023Member      
Account Value [Line Items]      
Accumulated Value 12,800    
C000212599_1_AdditionalIndexMember_AsOf_2024Member      
Account Value [Line Items]      
Accumulated Value 14,195    
C000212599_1_AdditionalIndexMember_AsOf_2025Member      
Account Value [Line Items]      
Accumulated Value 14,980    
C000212599_LG_2_AdditionalIndexMember_7YRMember      
Account Value [Line Items]      
Line Graph and Table Measure Name   <span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Russell 3000® Index</span>  
C000212599_2_AdditionalIndexMember_AsOf_2019Member      
Account Value [Line Items]      
Accumulated Value 10,000    
C000212599_2_AdditionalIndexMember_AsOf_2020Member      
Account Value [Line Items]      
Accumulated Value 10,459    
C000212599_2_AdditionalIndexMember_AsOf_2021Member      
Account Value [Line Items]      
Accumulated Value 15,078    
C000212599_2_AdditionalIndexMember_AsOf_2022Member      
Account Value [Line Items]      
Accumulated Value 12,987    
C000212599_2_AdditionalIndexMember_AsOf_2023Member      
Account Value [Line Items]      
Accumulated Value 15,449    
C000212599_2_AdditionalIndexMember_AsOf_2024Member      
Account Value [Line Items]      
Accumulated Value 19,021    
C000212599_2_AdditionalIndexMember_AsOf_2025Member      
Account Value [Line Items]      
Accumulated Value 21,931    
C000212598_LG_ClassMember_7YRMember      
Account Value [Line Items]      
Line Graph and Table Measure Name   <span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Fidelity® Small Cap Growth Index Fund</span>  
C000212598_ClassMember_AsOf_2019Member      
Account Value [Line Items]      
Accumulated Value 10,000    
C000212598_ClassMember_AsOf_2020Member      
Account Value [Line Items]      
Accumulated Value 10,359    
C000212598_ClassMember_AsOf_2021Member      
Account Value [Line Items]      
Accumulated Value 15,675    
C000212598_ClassMember_AsOf_2022Member      
Account Value [Line Items]      
Accumulated Value 10,451    
C000212598_ClassMember_AsOf_2023Member      
Account Value [Line Items]      
Accumulated Value 12,413    
C000212598_ClassMember_AsOf_2024Member      
Account Value [Line Items]      
Accumulated Value 13,562    
C000212598_ClassMember_AsOf_2025Member      
Account Value [Line Items]      
Accumulated Value 14,891    
C000212598_LG_1_AdditionalIndexMember_7YRMember      
Account Value [Line Items]      
Line Graph and Table Measure Name   <span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Russell 2000® Growth Index</span>  
C000212598_1_AdditionalIndexMember_AsOf_2019Member      
Account Value [Line Items]      
Accumulated Value 10,000    
C000212598_1_AdditionalIndexMember_AsOf_2020Member      
Account Value [Line Items]      
Accumulated Value 10,369    
C000212598_1_AdditionalIndexMember_AsOf_2021Member      
Account Value [Line Items]      
Accumulated Value 15,695    
C000212598_1_AdditionalIndexMember_AsOf_2022Member      
Account Value [Line Items]      
Accumulated Value 10,448    
C000212598_1_AdditionalIndexMember_AsOf_2023Member      
Account Value [Line Items]      
Accumulated Value 12,384    
C000212598_1_AdditionalIndexMember_AsOf_2024Member      
Account Value [Line Items]      
Accumulated Value 13,516    
C000212598_1_AdditionalIndexMember_AsOf_2025Member      
Account Value [Line Items]      
Accumulated Value 14,830    
C000212598_LG_2_AdditionalIndexMember_7YRMember      
Account Value [Line Items]      
Line Graph and Table Measure Name   <span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Russell 3000® Index</span>  
C000212598_2_AdditionalIndexMember_AsOf_2019Member      
Account Value [Line Items]      
Accumulated Value 10,000    
C000212598_2_AdditionalIndexMember_AsOf_2020Member      
Account Value [Line Items]      
Accumulated Value 10,459    
C000212598_2_AdditionalIndexMember_AsOf_2021Member      
Account Value [Line Items]      
Accumulated Value 15,078    
C000212598_2_AdditionalIndexMember_AsOf_2022Member      
Account Value [Line Items]      
Accumulated Value 12,987    
C000212598_2_AdditionalIndexMember_AsOf_2023Member      
Account Value [Line Items]      
Accumulated Value 15,449    
C000212598_2_AdditionalIndexMember_AsOf_2024Member      
Account Value [Line Items]      
Accumulated Value 19,021    
C000212598_2_AdditionalIndexMember_AsOf_2025Member      
Account Value [Line Items]      
Accumulated Value 21,931    
C000212595_LG_ClassMember_7YRMember      
Account Value [Line Items]      
Line Graph and Table Measure Name   <span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Fidelity® SAI Municipal Bond Index Fund</span>  
C000212595_ClassMember_AsOf_2019Member      
Account Value [Line Items]      
Accumulated Value 10,000    
C000212595_ClassMember_AsOf_2020Member      
Account Value [Line Items]      
Accumulated Value 10,296    
C000212595_ClassMember_AsOf_2021Member      
Account Value [Line Items]      
Accumulated Value 10,656    
C000212595_ClassMember_AsOf_2022Member      
Account Value [Line Items]      
Accumulated Value 9,618    
C000212595_ClassMember_AsOf_2023Member      
Account Value [Line Items]      
Accumulated Value 9,876    
C000212595_ClassMember_AsOf_2024Member      
Account Value [Line Items]      
Accumulated Value 10,163    
C000212595_ClassMember_AsOf_2025Member      
Account Value [Line Items]      
Accumulated Value 10,266    
C000212595_LG_1_AdditionalIndexMember_7YRMember      
Account Value [Line Items]      
Line Graph and Table Measure Name   <span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Bloomberg Municipal Bond Index</span>  
C000212595_1_AdditionalIndexMember_AsOf_2019Member      
Account Value [Line Items]      
Accumulated Value 10,000    
C000212595_1_AdditionalIndexMember_AsOf_2020Member      
Account Value [Line Items]      
Accumulated Value 10,410    
C000212595_1_AdditionalIndexMember_AsOf_2021Member      
Account Value [Line Items]      
Accumulated Value 10,843    
C000212595_1_AdditionalIndexMember_AsOf_2022Member      
Account Value [Line Items]      
Accumulated Value 9,914    
C000212595_1_AdditionalIndexMember_AsOf_2023Member      
Account Value [Line Items]      
Accumulated Value 10,230    
C000212595_1_AdditionalIndexMember_AsOf_2024Member      
Account Value [Line Items]      
Accumulated Value 10,558    
C000212595_1_AdditionalIndexMember_AsOf_2025Member      
Account Value [Line Items]      
Accumulated Value 10,676    
C000183196_LG_ClassMember_9YRMember      
Account Value [Line Items]      
Line Graph and Table Measure Name     <span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Fidelity® Municipal Income 2025 Fund</span>
C000183196_ClassMember_AsOf_2017Member      
Account Value [Line Items]      
Accumulated Value 10,000    
C000183196_ClassMember_AsOf_2018Member      
Account Value [Line Items]      
Accumulated Value 9,964    
C000183196_ClassMember_AsOf_2019Member      
Account Value [Line Items]      
Accumulated Value 9,960    
C000183196_ClassMember_AsOf_2020Member      
Account Value [Line Items]      
Accumulated Value 10,709    
C000183196_ClassMember_AsOf_2021Member      
Account Value [Line Items]      
Accumulated Value 10,973    
C000183196_ClassMember_AsOf_2022Member      
Account Value [Line Items]      
Accumulated Value 11,413    
C000183196_ClassMember_AsOf_2023Member      
Account Value [Line Items]      
Accumulated Value 10,849    
C000183196_ClassMember_AsOf_2024Member      
Account Value [Line Items]      
Accumulated Value 10,920    
C000183196_ClassMember_AsOf_2025Member      
Account Value [Line Items]      
Accumulated Value 11,270    
C000183196_LG_1_AdditionalIndexMember_9YRMember      
Account Value [Line Items]      
Line Graph and Table Measure Name     <span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Bloomberg Municipal Bond 2025 Ex Tobacco/Prepaid Gas Index</span>
C000183196_1_AdditionalIndexMember_AsOf_2017Member      
Account Value [Line Items]      
Accumulated Value 10,000    
C000183196_1_AdditionalIndexMember_AsOf_2018Member      
Account Value [Line Items]      
Accumulated Value 10,001    
C000183196_1_AdditionalIndexMember_AsOf_2019Member      
Account Value [Line Items]      
Accumulated Value 10,008    
C000183196_1_AdditionalIndexMember_AsOf_2020Member      
Account Value [Line Items]      
Accumulated Value 10,749    
C000183196_1_AdditionalIndexMember_AsOf_2021Member      
Account Value [Line Items]      
Accumulated Value 11,225    
C000183196_1_AdditionalIndexMember_AsOf_2022Member      
Account Value [Line Items]      
Accumulated Value 11,480    
C000183196_1_AdditionalIndexMember_AsOf_2023Member      
Account Value [Line Items]      
Accumulated Value 10,989    
C000183196_1_AdditionalIndexMember_AsOf_2024Member      
Account Value [Line Items]      
Accumulated Value 11,072    
C000183196_1_AdditionalIndexMember_AsOf_2025Member      
Account Value [Line Items]      
Accumulated Value 11,397    
C000183196_LG_2_AdditionalIndexMember_9YRMember      
Account Value [Line Items]      
Line Graph and Table Measure Name     <span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Bloomberg Municipal Bond Index</span>
C000183196_2_AdditionalIndexMember_AsOf_2017Member      
Account Value [Line Items]      
Accumulated Value 10,000    
C000183196_2_AdditionalIndexMember_AsOf_2018Member      
Account Value [Line Items]      
Accumulated Value 10,005    
C000183196_2_AdditionalIndexMember_AsOf_2019Member      
Account Value [Line Items]      
Accumulated Value 10,162    
C000183196_2_AdditionalIndexMember_AsOf_2020Member      
Account Value [Line Items]      
Accumulated Value 10,843    
C000183196_2_AdditionalIndexMember_AsOf_2021Member      
Account Value [Line Items]      
Accumulated Value 11,325    
C000183196_2_AdditionalIndexMember_AsOf_2022Member      
Account Value [Line Items]      
Accumulated Value 11,797    
C000183196_2_AdditionalIndexMember_AsOf_2023Member      
Account Value [Line Items]      
Accumulated Value 10,786    
C000183196_2_AdditionalIndexMember_AsOf_2024Member      
Account Value [Line Items]      
Accumulated Value 11,130    
C000183196_2_AdditionalIndexMember_AsOf_2025Member      
Account Value [Line Items]      
Accumulated Value 11,487    
C000183198_LG_ClassMember_9YRMember      
Account Value [Line Items]      
Line Graph and Table Measure Name     <span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Class I</span>
C000183198_ClassMember_AsOf_2017Member      
Account Value [Line Items]      
Accumulated Value 10,000    
C000183198_ClassMember_AsOf_2018Member      
Account Value [Line Items]      
Accumulated Value 9,964    
C000183198_ClassMember_AsOf_2019Member      
Account Value [Line Items]      
Accumulated Value 9,960    
C000183198_ClassMember_AsOf_2020Member      
Account Value [Line Items]      
Accumulated Value 10,709    
C000183198_ClassMember_AsOf_2021Member      
Account Value [Line Items]      
Accumulated Value 10,984    
C000183198_ClassMember_AsOf_2022Member      
Account Value [Line Items]      
Accumulated Value 11,413    
C000183198_ClassMember_AsOf_2023Member      
Account Value [Line Items]      
Accumulated Value 10,848    
C000183198_ClassMember_AsOf_2024Member      
Account Value [Line Items]      
Accumulated Value 10,920    
C000183198_ClassMember_AsOf_2025Member      
Account Value [Line Items]      
Accumulated Value 11,270    
C000183198_LG_1_AdditionalIndexMember_9YRMember      
Account Value [Line Items]      
Line Graph and Table Measure Name     <span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Bloomberg Municipal Bond 2025 Ex Tobacco/Prepaid Gas Index</span>
C000183198_1_AdditionalIndexMember_AsOf_2017Member      
Account Value [Line Items]      
Accumulated Value 10,000    
C000183198_1_AdditionalIndexMember_AsOf_2018Member      
Account Value [Line Items]      
Accumulated Value 10,001    
C000183198_1_AdditionalIndexMember_AsOf_2019Member      
Account Value [Line Items]      
Accumulated Value 10,008    
C000183198_1_AdditionalIndexMember_AsOf_2020Member      
Account Value [Line Items]      
Accumulated Value 10,749    
C000183198_1_AdditionalIndexMember_AsOf_2021Member      
Account Value [Line Items]      
Accumulated Value 11,225    
C000183198_1_AdditionalIndexMember_AsOf_2022Member      
Account Value [Line Items]      
Accumulated Value 11,480    
C000183198_1_AdditionalIndexMember_AsOf_2023Member      
Account Value [Line Items]      
Accumulated Value 10,989    
C000183198_1_AdditionalIndexMember_AsOf_2024Member      
Account Value [Line Items]      
Accumulated Value 11,072    
C000183198_1_AdditionalIndexMember_AsOf_2025Member      
Account Value [Line Items]      
Accumulated Value 11,397    
C000183198_LG_2_AdditionalIndexMember_9YRMember      
Account Value [Line Items]      
Line Graph and Table Measure Name     <span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Bloomberg Municipal Bond Index</span>
C000183198_2_AdditionalIndexMember_AsOf_2017Member      
Account Value [Line Items]      
Accumulated Value 10,000    
C000183198_2_AdditionalIndexMember_AsOf_2018Member      
Account Value [Line Items]      
Accumulated Value 10,005    
C000183198_2_AdditionalIndexMember_AsOf_2019Member      
Account Value [Line Items]      
Accumulated Value 10,162    
C000183198_2_AdditionalIndexMember_AsOf_2020Member      
Account Value [Line Items]      
Accumulated Value 10,843    
C000183198_2_AdditionalIndexMember_AsOf_2021Member      
Account Value [Line Items]      
Accumulated Value 11,325    
C000183198_2_AdditionalIndexMember_AsOf_2022Member      
Account Value [Line Items]      
Accumulated Value 11,797    
C000183198_2_AdditionalIndexMember_AsOf_2023Member      
Account Value [Line Items]      
Accumulated Value 10,786    
C000183198_2_AdditionalIndexMember_AsOf_2024Member      
Account Value [Line Items]      
Accumulated Value 11,130    
C000183198_2_AdditionalIndexMember_AsOf_2025Member      
Account Value [Line Items]      
Accumulated Value 11,487    
C000183197_LG_ClassMember_9YRMember      
Account Value [Line Items]      
Line Graph and Table Measure Name     <span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Class A</span>
C000183197_ClassMember_AsOf_2017Member      
Account Value [Line Items]      
Accumulated Value 9,725    
C000183197_ClassMember_AsOf_2018Member      
Account Value [Line Items]      
Accumulated Value 9,688    
C000183197_ClassMember_AsOf_2019Member      
Account Value [Line Items]      
Accumulated Value 9,660    
C000183197_ClassMember_AsOf_2020Member      
Account Value [Line Items]      
Accumulated Value 10,360    
C000183197_ClassMember_AsOf_2021Member      
Account Value [Line Items]      
Accumulated Value 10,589    
C000183197_ClassMember_AsOf_2022Member      
Account Value [Line Items]      
Accumulated Value 10,986    
C000183197_ClassMember_AsOf_2023Member      
Account Value [Line Items]      
Accumulated Value 10,417    
C000183197_ClassMember_AsOf_2024Member      
Account Value [Line Items]      
Accumulated Value 10,459    
C000183197_ClassMember_AsOf_2025Member      
Account Value [Line Items]      
Accumulated Value 10,767    
C000183197_LG_1_AdditionalIndexMember_9YRMember      
Account Value [Line Items]      
Line Graph and Table Measure Name     <span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Bloomberg Municipal Bond 2025 Ex Tobacco/Prepaid Gas Index</span>
C000183197_1_AdditionalIndexMember_AsOf_2017Member      
Account Value [Line Items]      
Accumulated Value 10,000    
C000183197_1_AdditionalIndexMember_AsOf_2018Member      
Account Value [Line Items]      
Accumulated Value 10,001    
C000183197_1_AdditionalIndexMember_AsOf_2019Member      
Account Value [Line Items]      
Accumulated Value 10,008    
C000183197_1_AdditionalIndexMember_AsOf_2020Member      
Account Value [Line Items]      
Accumulated Value 10,749    
C000183197_1_AdditionalIndexMember_AsOf_2021Member      
Account Value [Line Items]      
Accumulated Value 11,225    
C000183197_1_AdditionalIndexMember_AsOf_2022Member      
Account Value [Line Items]      
Accumulated Value 11,480    
C000183197_1_AdditionalIndexMember_AsOf_2023Member      
Account Value [Line Items]      
Accumulated Value 10,989    
C000183197_1_AdditionalIndexMember_AsOf_2024Member      
Account Value [Line Items]      
Accumulated Value 11,072    
C000183197_1_AdditionalIndexMember_AsOf_2025Member      
Account Value [Line Items]      
Accumulated Value 11,397    
C000183197_LG_2_AdditionalIndexMember_9YRMember      
Account Value [Line Items]      
Line Graph and Table Measure Name     <span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Bloomberg Municipal Bond Index</span>
C000183197_2_AdditionalIndexMember_AsOf_2017Member      
Account Value [Line Items]      
Accumulated Value 10,000    
C000183197_2_AdditionalIndexMember_AsOf_2018Member      
Account Value [Line Items]      
Accumulated Value 10,005    
C000183197_2_AdditionalIndexMember_AsOf_2019Member      
Account Value [Line Items]      
Accumulated Value 10,162    
C000183197_2_AdditionalIndexMember_AsOf_2020Member      
Account Value [Line Items]      
Accumulated Value 10,843    
C000183197_2_AdditionalIndexMember_AsOf_2021Member      
Account Value [Line Items]      
Accumulated Value 11,325    
C000183197_2_AdditionalIndexMember_AsOf_2022Member      
Account Value [Line Items]      
Accumulated Value 11,797    
C000183197_2_AdditionalIndexMember_AsOf_2023Member      
Account Value [Line Items]      
Accumulated Value 10,786    
C000183197_2_AdditionalIndexMember_AsOf_2024Member      
Account Value [Line Items]      
Accumulated Value 11,130    
C000183197_2_AdditionalIndexMember_AsOf_2025Member      
Account Value [Line Items]      
Accumulated Value 11,487    
C000212597_LG_ClassMember_7YRMember      
Account Value [Line Items]      
Line Graph and Table Measure Name   <span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Fidelity® Mid Cap Value Index Fund</span>  
C000212597_ClassMember_AsOf_2019Member      
Account Value [Line Items]      
Accumulated Value 10,000    
C000212597_ClassMember_AsOf_2020Member      
Account Value [Line Items]      
Accumulated Value 8,735    
C000212597_ClassMember_AsOf_2021Member      
Account Value [Line Items]      
Accumulated Value 13,349    
C000212597_ClassMember_AsOf_2022Member      
Account Value [Line Items]      
Accumulated Value 12,003    
C000212597_ClassMember_AsOf_2023Member      
Account Value [Line Items]      
Accumulated Value 13,271    
C000212597_ClassMember_AsOf_2024Member      
Account Value [Line Items]      
Accumulated Value 14,858    
C000212597_ClassMember_AsOf_2025Member      
Account Value [Line Items]      
Accumulated Value 16,559    
C000212597_LG_1_AdditionalIndexMember_7YRMember      
Account Value [Line Items]      
Line Graph and Table Measure Name   <span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Russell Midcap® Value Index</span>  
C000212597_1_AdditionalIndexMember_AsOf_2019Member      
Account Value [Line Items]      
Accumulated Value 10,000    
C000212597_1_AdditionalIndexMember_AsOf_2020Member      
Account Value [Line Items]      
Accumulated Value 8,756    
C000212597_1_AdditionalIndexMember_AsOf_2021Member      
Account Value [Line Items]      
Accumulated Value 13,402    
C000212597_1_AdditionalIndexMember_AsOf_2022Member      
Account Value [Line Items]      
Accumulated Value 12,062    
C000212597_1_AdditionalIndexMember_AsOf_2023Member      
Account Value [Line Items]      
Accumulated Value 13,329    
C000212597_1_AdditionalIndexMember_AsOf_2024Member      
Account Value [Line Items]      
Accumulated Value 14,925    
C000212597_1_AdditionalIndexMember_AsOf_2025Member      
Account Value [Line Items]      
Accumulated Value 16,647    
C000212597_LG_2_AdditionalIndexMember_7YRMember      
Account Value [Line Items]      
Line Graph and Table Measure Name   <span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Russell 3000® Index</span>  
C000212597_2_AdditionalIndexMember_AsOf_2019Member      
Account Value [Line Items]      
Accumulated Value 10,000    
C000212597_2_AdditionalIndexMember_AsOf_2020Member      
Account Value [Line Items]      
Accumulated Value 10,459    
C000212597_2_AdditionalIndexMember_AsOf_2021Member      
Account Value [Line Items]      
Accumulated Value 15,078    
C000212597_2_AdditionalIndexMember_AsOf_2022Member      
Account Value [Line Items]      
Accumulated Value 12,987    
C000212597_2_AdditionalIndexMember_AsOf_2023Member      
Account Value [Line Items]      
Accumulated Value 15,449    
C000212597_2_AdditionalIndexMember_AsOf_2024Member      
Account Value [Line Items]      
Accumulated Value 19,021    
C000212597_2_AdditionalIndexMember_AsOf_2025Member      
Account Value [Line Items]      
Accumulated Value 21,931    
C000212596_LG_ClassMember_7YRMember      
Account Value [Line Items]      
Line Graph and Table Measure Name   <span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Fidelity® Mid Cap Growth Index Fund</span>  
C000212596_ClassMember_AsOf_2019Member      
Account Value [Line Items]      
Accumulated Value 10,000    
C000212596_ClassMember_AsOf_2020Member      
Account Value [Line Items]      
Accumulated Value 10,886    
C000212596_ClassMember_AsOf_2021Member      
Account Value [Line Items]      
Accumulated Value 15,643    
C000212596_ClassMember_AsOf_2022Member      
Account Value [Line Items]      
Accumulated Value 11,018    
C000212596_ClassMember_AsOf_2023Member      
Account Value [Line Items]      
Accumulated Value 13,566    
C000212596_ClassMember_AsOf_2024Member      
Account Value [Line Items]      
Accumulated Value 15,601    
C000212596_ClassMember_AsOf_2025Member      
Account Value [Line Items]      
Accumulated Value 19,711    
C000212596_LG_1_AdditionalIndexMember_7YRMember      
Account Value [Line Items]      
Line Graph and Table Measure Name   <span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Russell Midcap® Growth Index</span>  
C000212596_1_AdditionalIndexMember_AsOf_2019Member      
Account Value [Line Items]      
Accumulated Value 10,000    
C000212596_1_AdditionalIndexMember_AsOf_2020Member      
Account Value [Line Items]      
Accumulated Value 10,946    
C000212596_1_AdditionalIndexMember_AsOf_2021Member      
Account Value [Line Items]      
Accumulated Value 15,738    
C000212596_1_AdditionalIndexMember_AsOf_2022Member      
Account Value [Line Items]      
Accumulated Value 11,083    
C000212596_1_AdditionalIndexMember_AsOf_2023Member      
Account Value [Line Items]      
Accumulated Value 13,647    
C000212596_1_AdditionalIndexMember_AsOf_2024Member      
Account Value [Line Items]      
Accumulated Value 15,702    
C000212596_1_AdditionalIndexMember_AsOf_2025Member      
Account Value [Line Items]      
Accumulated Value 19,861    
C000212596_LG_2_AdditionalIndexMember_7YRMember      
Account Value [Line Items]      
Line Graph and Table Measure Name   <span style="font-family:'Fidelity Sans';font-size:9px;color:#000000;font-style:normal;font-weight:normal;">Russell 3000® Index</span>  
C000212596_2_AdditionalIndexMember_AsOf_2019Member      
Account Value [Line Items]      
Accumulated Value 10,000    
C000212596_2_AdditionalIndexMember_AsOf_2020Member      
Account Value [Line Items]      
Accumulated Value 10,459    
C000212596_2_AdditionalIndexMember_AsOf_2021Member      
Account Value [Line Items]      
Accumulated Value 15,078    
C000212596_2_AdditionalIndexMember_AsOf_2022Member      
Account Value [Line Items]      
Accumulated Value 12,987    
C000212596_2_AdditionalIndexMember_AsOf_2023Member      
Account Value [Line Items]      
Accumulated Value 15,449    
C000212596_2_AdditionalIndexMember_AsOf_2024Member      
Account Value [Line Items]      
Accumulated Value 19,021    
C000212596_2_AdditionalIndexMember_AsOf_2025Member      
Account Value [Line Items]      
Accumulated Value $ 21,931