v3.25.2
Shareholder Report, Holdings (Details)
Apr. 30, 2025
Fidelity Large Cap Value Index Fund | TH0Member  
Holdings [Line Items]  
Percent of Net Asset Value 4.00%
Fidelity Large Cap Value Index Fund | TH1Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.90%
Fidelity Large Cap Value Index Fund | TH2Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.00%
Fidelity Large Cap Value Index Fund | TH3Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.70%
Fidelity Large Cap Value Index Fund | TH4Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.70%
Fidelity Large Cap Value Index Fund | TH5Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.60%
Fidelity Large Cap Value Index Fund | TH6Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.30%
Fidelity Large Cap Value Index Fund | TH7Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.20%
Fidelity Large Cap Value Index Fund | TH8Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.10%
Fidelity Large Cap Value Index Fund | TH9Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.10%
Fidelity Large Cap Value Index Fund | MSFinancialsSectorMember  
Holdings [Line Items]  
Percent of Net Asset Value 23.40%
Fidelity Large Cap Value Index Fund | Information Technology Member  
Holdings [Line Items]  
Percent of Net Asset Value 8.70%
Fidelity Large Cap Value Index Fund | Healthcare Sector  
Holdings [Line Items]  
Percent of Net Asset Value 14.20%
Fidelity Large Cap Value Index Fund | Real Estate Sector  
Holdings [Line Items]  
Percent of Net Asset Value 4.80%
Fidelity Large Cap Value Index Fund | Industrial Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 14.40%
Fidelity Large Cap Value Index Fund | Materials Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 4.10%
Fidelity Large Cap Value Index Fund | Consumer Discretionary Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 5.90%
Fidelity Large Cap Value Index Fund | Consumer Staples Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 8.50%
Fidelity Large Cap Value Index Fund | Communications Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 4.50%
Fidelity Large Cap Value Index Fund | Energy Sector  
Holdings [Line Items]  
Percent of Net Asset Value 6.30%
Fidelity Large Cap Value Index Fund | Utilities Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 4.90%
Fidelity Large Cap Value Index Fund | United States  
Holdings [Line Items]  
Percent of Net Asset Value 98.90%
Fidelity Large Cap Value Index Fund | Ireland  
Holdings [Line Items]  
Percent of Net Asset Value 0.80%
Fidelity Large Cap Value Index Fund | Canada  
Holdings [Line Items]  
Percent of Net Asset Value 0.10%
Fidelity Large Cap Value Index Fund | BailiwickOfJerseyMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.10%
Fidelity Large Cap Value Index Fund | Bermuda  
Holdings [Line Items]  
Percent of Net Asset Value 0.10%
Fidelity Large Cap Value Index Fund | United Kingdom  
Holdings [Line Items]  
Percent of Net Asset Value 0.00%
Fidelity Large Cap Value Index Fund | Brazil  
Holdings [Line Items]  
Percent of Net Asset Value 0.00%
Fidelity Large Cap Value Index Fund | Puerto Rico  
Holdings [Line Items]  
Percent of Net Asset Value 0.00%
Fidelity Large Cap Value Index Fund | Belgium  
Holdings [Line Items]  
Percent of Net Asset Value 0.00%
Fidelity Large Cap Value Index Fund | AACommonStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 99.70%
Fidelity Large Cap Value Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.30%
Fidelity Mid Cap Index Fund | TH0Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.30%
Fidelity Mid Cap Index Fund | TH1Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.80%
Fidelity Mid Cap Index Fund | TH2Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.70%
Fidelity Mid Cap Index Fund | TH3Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.60%
Fidelity Mid Cap Index Fund | TH4Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.60%
Fidelity Mid Cap Index Fund | TH5Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.60%
Fidelity Mid Cap Index Fund | TH6Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.60%
Fidelity Mid Cap Index Fund | TH7Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.50%
Fidelity Mid Cap Index Fund | TH8Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.50%
Fidelity Mid Cap Index Fund | TH9Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.50%
Fidelity Mid Cap Index Fund | MSFinancialsSectorMember  
Holdings [Line Items]  
Percent of Net Asset Value 16.60%
Fidelity Mid Cap Index Fund | Information Technology Member  
Holdings [Line Items]  
Percent of Net Asset Value 14.00%
Fidelity Mid Cap Index Fund | Healthcare Sector  
Holdings [Line Items]  
Percent of Net Asset Value 9.10%
Fidelity Mid Cap Index Fund | Real Estate Sector  
Holdings [Line Items]  
Percent of Net Asset Value 7.80%
Fidelity Mid Cap Index Fund | Industrial Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 16.80%
Fidelity Mid Cap Index Fund | Materials Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 5.20%
Fidelity Mid Cap Index Fund | Consumer Discretionary Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 9.90%
Fidelity Mid Cap Index Fund | Consumer Staples Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 5.10%
Fidelity Mid Cap Index Fund | Communications Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.60%
Fidelity Mid Cap Index Fund | Energy Sector  
Holdings [Line Items]  
Percent of Net Asset Value 5.20%
Fidelity Mid Cap Index Fund | Utilities Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 6.30%
Fidelity Mid Cap Index Fund | United States  
Holdings [Line Items]  
Percent of Net Asset Value 98.80%
Fidelity Mid Cap Index Fund | Canada  
Holdings [Line Items]  
Percent of Net Asset Value 0.20%
Fidelity Mid Cap Index Fund | BailiwickOfJerseyMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.10%
Fidelity Mid Cap Index Fund | Bermuda  
Holdings [Line Items]  
Percent of Net Asset Value 0.10%
Fidelity Mid Cap Index Fund | United Kingdom  
Holdings [Line Items]  
Percent of Net Asset Value 0.10%
Fidelity Mid Cap Index Fund | Brazil  
Holdings [Line Items]  
Percent of Net Asset Value 0.40%
Fidelity Mid Cap Index Fund | Puerto Rico  
Holdings [Line Items]  
Percent of Net Asset Value 0.10%
Fidelity Mid Cap Index Fund | Belgium  
Holdings [Line Items]  
Percent of Net Asset Value 0.00%
Fidelity Mid Cap Index Fund | Korea, Republic of  
Holdings [Line Items]  
Percent of Net Asset Value 0.20%
Fidelity Mid Cap Index Fund | AACommonStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 99.60%
Fidelity Mid Cap Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.40%
Fidelity Flex Mid Cap Index Fund | TH0Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.20%
Fidelity Flex Mid Cap Index Fund | TH1Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.80%
Fidelity Flex Mid Cap Index Fund | TH2Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.70%
Fidelity Flex Mid Cap Index Fund | TH3Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.60%
Fidelity Flex Mid Cap Index Fund | TH4Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.60%
Fidelity Flex Mid Cap Index Fund | TH5Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.60%
Fidelity Flex Mid Cap Index Fund | TH6Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.60%
Fidelity Flex Mid Cap Index Fund | TH7Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.50%
Fidelity Flex Mid Cap Index Fund | TH8Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.50%
Fidelity Flex Mid Cap Index Fund | TH9Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.50%
Fidelity Flex Mid Cap Index Fund | MSFinancialsSectorMember  
Holdings [Line Items]  
Percent of Net Asset Value 16.70%
Fidelity Flex Mid Cap Index Fund | Information Technology Member  
Holdings [Line Items]  
Percent of Net Asset Value 14.00%
Fidelity Flex Mid Cap Index Fund | Healthcare Sector  
Holdings [Line Items]  
Percent of Net Asset Value 9.10%
Fidelity Flex Mid Cap Index Fund | Real Estate Sector  
Holdings [Line Items]  
Percent of Net Asset Value 7.80%
Fidelity Flex Mid Cap Index Fund | Industrial Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 16.90%
Fidelity Flex Mid Cap Index Fund | Materials Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 5.20%
Fidelity Flex Mid Cap Index Fund | Consumer Discretionary Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 9.90%
Fidelity Flex Mid Cap Index Fund | Consumer Staples Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 5.10%
Fidelity Flex Mid Cap Index Fund | Communications Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.60%
Fidelity Flex Mid Cap Index Fund | Energy Sector  
Holdings [Line Items]  
Percent of Net Asset Value 5.20%
Fidelity Flex Mid Cap Index Fund | Utilities Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 6.30%
Fidelity Flex Mid Cap Index Fund | United States  
Holdings [Line Items]  
Percent of Net Asset Value 98.70%
Fidelity Flex Mid Cap Index Fund | Canada  
Holdings [Line Items]  
Percent of Net Asset Value 0.20%
Fidelity Flex Mid Cap Index Fund | BailiwickOfJerseyMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.10%
Fidelity Flex Mid Cap Index Fund | Bermuda  
Holdings [Line Items]  
Percent of Net Asset Value 0.10%
Fidelity Flex Mid Cap Index Fund | United Kingdom  
Holdings [Line Items]  
Percent of Net Asset Value 0.10%
Fidelity Flex Mid Cap Index Fund | Brazil  
Holdings [Line Items]  
Percent of Net Asset Value 0.50%
Fidelity Flex Mid Cap Index Fund | Puerto Rico  
Holdings [Line Items]  
Percent of Net Asset Value 0.10%
Fidelity Flex Mid Cap Index Fund | Belgium  
Holdings [Line Items]  
Percent of Net Asset Value 0.00%
Fidelity Flex Mid Cap Index Fund | Korea, Republic of  
Holdings [Line Items]  
Percent of Net Asset Value 0.20%
Fidelity Flex Mid Cap Index Fund | AACommonStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 99.80%
Fidelity Flex Mid Cap Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.20%
Fidelity Flex Mid Cap Index Fund | AAPreferredStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.00%
Fidelity Large Cap Growth Index Fund | TH0Member  
Holdings [Line Items]  
Percent of Net Asset Value 11.40%
Fidelity Large Cap Growth Index Fund | TH1Member  
Holdings [Line Items]  
Percent of Net Asset Value 10.70%
Fidelity Large Cap Growth Index Fund | TH2Member  
Holdings [Line Items]  
Percent of Net Asset Value 9.20%
Fidelity Large Cap Growth Index Fund | TH3Member  
Holdings [Line Items]  
Percent of Net Asset Value 6.40%
Fidelity Large Cap Growth Index Fund | TH4Member  
Holdings [Line Items]  
Percent of Net Asset Value 4.00%
Fidelity Large Cap Growth Index Fund | TH5Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.40%
Fidelity Large Cap Growth Index Fund | TH6Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.30%
Fidelity Large Cap Growth Index Fund | TH7Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.10%
Fidelity Large Cap Growth Index Fund | TH8Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.80%
Fidelity Large Cap Growth Index Fund | TH9Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.80%
Fidelity Large Cap Growth Index Fund | MSFinancialsSectorMember  
Holdings [Line Items]  
Percent of Net Asset Value 7.50%
Fidelity Large Cap Growth Index Fund | Information Technology Member  
Holdings [Line Items]  
Percent of Net Asset Value 46.50%
Fidelity Large Cap Growth Index Fund | Healthcare Sector  
Holdings [Line Items]  
Percent of Net Asset Value 7.80%
Fidelity Large Cap Growth Index Fund | Real Estate Sector  
Holdings [Line Items]  
Percent of Net Asset Value 0.60%
Fidelity Large Cap Growth Index Fund | Industrial Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 4.90%
Fidelity Large Cap Growth Index Fund | Materials Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.60%
Fidelity Large Cap Growth Index Fund | Consumer Discretionary Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 14.60%
Fidelity Large Cap Growth Index Fund | Consumer Staples Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.80%
Fidelity Large Cap Growth Index Fund | Communications Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 12.80%
Fidelity Large Cap Growth Index Fund | Energy Sector  
Holdings [Line Items]  
Percent of Net Asset Value 0.50%
Fidelity Large Cap Growth Index Fund | Utilities Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.20%
Fidelity Large Cap Growth Index Fund | United States  
Holdings [Line Items]  
Percent of Net Asset Value 99.70%
Fidelity Large Cap Growth Index Fund | Brazil  
Holdings [Line Items]  
Percent of Net Asset Value 0.20%
Fidelity Large Cap Growth Index Fund | Puerto Rico  
Holdings [Line Items]  
Percent of Net Asset Value 0.00%
Fidelity Large Cap Growth Index Fund | Korea, Republic of  
Holdings [Line Items]  
Percent of Net Asset Value 0.10%
Fidelity Large Cap Growth Index Fund | Mexico  
Holdings [Line Items]  
Percent of Net Asset Value 0.00%
Fidelity Large Cap Growth Index Fund | AACommonStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 99.80%
Fidelity Large Cap Growth Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.20%
Fidelity Flex Small Cap Index Fund | TH0Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.70%
Fidelity Flex Small Cap Index Fund | TH1Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.60%
Fidelity Flex Small Cap Index Fund | TH2Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.60%
Fidelity Flex Small Cap Index Fund | TH3Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.50%
Fidelity Flex Small Cap Index Fund | TH4Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.50%
Fidelity Flex Small Cap Index Fund | TH5Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.50%
Fidelity Flex Small Cap Index Fund | TH6Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.40%
Fidelity Flex Small Cap Index Fund | TH7Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.40%
Fidelity Flex Small Cap Index Fund | TH8Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.40%
Fidelity Flex Small Cap Index Fund | TH9Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.40%
Fidelity Flex Small Cap Index Fund | MSFinancialsSectorMember  
Holdings [Line Items]  
Percent of Net Asset Value 19.80%
Fidelity Flex Small Cap Index Fund | Information Technology Member  
Holdings [Line Items]  
Percent of Net Asset Value 12.60%
Fidelity Flex Small Cap Index Fund | Healthcare Sector  
Holdings [Line Items]  
Percent of Net Asset Value 17.10%
Fidelity Flex Small Cap Index Fund | Real Estate Sector  
Holdings [Line Items]  
Percent of Net Asset Value 6.20%
Fidelity Flex Small Cap Index Fund | Industrial Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 17.30%
Fidelity Flex Small Cap Index Fund | Materials Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.80%
Fidelity Flex Small Cap Index Fund | Consumer Discretionary Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 9.10%
Fidelity Flex Small Cap Index Fund | Consumer Staples Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.30%
Fidelity Flex Small Cap Index Fund | Communications Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.40%
Fidelity Flex Small Cap Index Fund | Energy Sector  
Holdings [Line Items]  
Percent of Net Asset Value 4.60%
Fidelity Flex Small Cap Index Fund | Utilities Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.30%
Fidelity Flex Small Cap Index Fund | United States  
Holdings [Line Items]  
Percent of Net Asset Value 97.00%
Fidelity Flex Small Cap Index Fund | Canada  
Holdings [Line Items]  
Percent of Net Asset Value 0.60%
Fidelity Flex Small Cap Index Fund | Bermuda  
Holdings [Line Items]  
Percent of Net Asset Value 0.10%
Fidelity Flex Small Cap Index Fund | Brazil  
Holdings [Line Items]  
Percent of Net Asset Value 0.30%
Fidelity Flex Small Cap Index Fund | Puerto Rico  
Holdings [Line Items]  
Percent of Net Asset Value 0.30%
Fidelity Flex Small Cap Index Fund | Thailand  
Holdings [Line Items]  
Percent of Net Asset Value 0.30%
Fidelity Flex Small Cap Index Fund | Norway  
Holdings [Line Items]  
Percent of Net Asset Value 0.20%
Fidelity Flex Small Cap Index Fund | Cameroon  
Holdings [Line Items]  
Percent of Net Asset Value 0.20%
Fidelity Flex Small Cap Index Fund | India  
Holdings [Line Items]  
Percent of Net Asset Value 0.10%
Fidelity Flex Small Cap Index Fund | OtherMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.90%
Fidelity Flex Small Cap Index Fund | AACommonStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 99.50%
Fidelity Flex Small Cap Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.50%
Fidelity Small Cap Index Fund | TH0Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.80%
Fidelity Small Cap Index Fund | TH1Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.60%
Fidelity Small Cap Index Fund | TH2Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.60%
Fidelity Small Cap Index Fund | TH3Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.50%
Fidelity Small Cap Index Fund | TH4Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.50%
Fidelity Small Cap Index Fund | TH5Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.50%
Fidelity Small Cap Index Fund | TH6Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.50%
Fidelity Small Cap Index Fund | TH7Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.40%
Fidelity Small Cap Index Fund | TH8Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.40%
Fidelity Small Cap Index Fund | TH9Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.40%
Fidelity Small Cap Index Fund | MSFinancialsSectorMember  
Holdings [Line Items]  
Percent of Net Asset Value 19.80%
Fidelity Small Cap Index Fund | Information Technology Member  
Holdings [Line Items]  
Percent of Net Asset Value 12.50%
Fidelity Small Cap Index Fund | Healthcare Sector  
Holdings [Line Items]  
Percent of Net Asset Value 17.00%
Fidelity Small Cap Index Fund | Real Estate Sector  
Holdings [Line Items]  
Percent of Net Asset Value 6.10%
Fidelity Small Cap Index Fund | Industrial Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 17.40%
Fidelity Small Cap Index Fund | Materials Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.80%
Fidelity Small Cap Index Fund | Consumer Discretionary Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 9.10%
Fidelity Small Cap Index Fund | Consumer Staples Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.30%
Fidelity Small Cap Index Fund | Communications Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.50%
Fidelity Small Cap Index Fund | Energy Sector  
Holdings [Line Items]  
Percent of Net Asset Value 4.60%
Fidelity Small Cap Index Fund | Utilities Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.20%
Fidelity Small Cap Index Fund | United States  
Holdings [Line Items]  
Percent of Net Asset Value 97.00%
Fidelity Small Cap Index Fund | Canada  
Holdings [Line Items]  
Percent of Net Asset Value 0.60%
Fidelity Small Cap Index Fund | Bermuda  
Holdings [Line Items]  
Percent of Net Asset Value 0.10%
Fidelity Small Cap Index Fund | Brazil  
Holdings [Line Items]  
Percent of Net Asset Value 0.30%
Fidelity Small Cap Index Fund | Puerto Rico  
Holdings [Line Items]  
Percent of Net Asset Value 0.30%
Fidelity Small Cap Index Fund | Thailand  
Holdings [Line Items]  
Percent of Net Asset Value 0.30%
Fidelity Small Cap Index Fund | Norway  
Holdings [Line Items]  
Percent of Net Asset Value 0.20%
Fidelity Small Cap Index Fund | Cameroon  
Holdings [Line Items]  
Percent of Net Asset Value 0.20%
Fidelity Small Cap Index Fund | India  
Holdings [Line Items]  
Percent of Net Asset Value 0.10%
Fidelity Small Cap Index Fund | OtherMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.90%
Fidelity Small Cap Index Fund | AACommonStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 99.30%
Fidelity Small Cap Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.70%
Fidelity Series Large Cap Growth Index Fund | TH0Member  
Holdings [Line Items]  
Percent of Net Asset Value 11.40%
Fidelity Series Large Cap Growth Index Fund | TH1Member  
Holdings [Line Items]  
Percent of Net Asset Value 10.70%
Fidelity Series Large Cap Growth Index Fund | TH2Member  
Holdings [Line Items]  
Percent of Net Asset Value 9.20%
Fidelity Series Large Cap Growth Index Fund | TH3Member  
Holdings [Line Items]  
Percent of Net Asset Value 6.40%
Fidelity Series Large Cap Growth Index Fund | TH4Member  
Holdings [Line Items]  
Percent of Net Asset Value 4.00%
Fidelity Series Large Cap Growth Index Fund | TH5Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.40%
Fidelity Series Large Cap Growth Index Fund | TH6Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.30%
Fidelity Series Large Cap Growth Index Fund | TH7Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.10%
Fidelity Series Large Cap Growth Index Fund | TH8Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.80%
Fidelity Series Large Cap Growth Index Fund | TH9Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.80%
Fidelity Series Large Cap Growth Index Fund | MSFinancialsSectorMember  
Holdings [Line Items]  
Percent of Net Asset Value 7.50%
Fidelity Series Large Cap Growth Index Fund | Information Technology Member  
Holdings [Line Items]  
Percent of Net Asset Value 46.40%
Fidelity Series Large Cap Growth Index Fund | Healthcare Sector  
Holdings [Line Items]  
Percent of Net Asset Value 7.80%
Fidelity Series Large Cap Growth Index Fund | Real Estate Sector  
Holdings [Line Items]  
Percent of Net Asset Value 0.60%
Fidelity Series Large Cap Growth Index Fund | Industrial Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 4.90%
Fidelity Series Large Cap Growth Index Fund | Materials Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.60%
Fidelity Series Large Cap Growth Index Fund | Consumer Discretionary Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 14.60%
Fidelity Series Large Cap Growth Index Fund | Consumer Staples Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.80%
Fidelity Series Large Cap Growth Index Fund | Communications Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 12.80%
Fidelity Series Large Cap Growth Index Fund | Energy Sector  
Holdings [Line Items]  
Percent of Net Asset Value 0.50%
Fidelity Series Large Cap Growth Index Fund | Utilities Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.20%
Fidelity Series Large Cap Growth Index Fund | United States  
Holdings [Line Items]  
Percent of Net Asset Value 99.70%
Fidelity Series Large Cap Growth Index Fund | Brazil  
Holdings [Line Items]  
Percent of Net Asset Value 0.20%
Fidelity Series Large Cap Growth Index Fund | Puerto Rico  
Holdings [Line Items]  
Percent of Net Asset Value 0.00%
Fidelity Series Large Cap Growth Index Fund | Korea, Republic of  
Holdings [Line Items]  
Percent of Net Asset Value 0.10%
Fidelity Series Large Cap Growth Index Fund | Mexico  
Holdings [Line Items]  
Percent of Net Asset Value 0.00%
Fidelity Series Large Cap Growth Index Fund | AACommonStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 99.70%
Fidelity Series Large Cap Growth Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.30%