v3.25.2
Shareholder Report, Holdings (Details)
Apr. 30, 2025
Fidelity ZERO Large Cap Index Fund | TH0Member  
Holdings [Line Items]  
Percent of Net Asset Value 6.70%
Fidelity ZERO Large Cap Index Fund | TH1Member  
Holdings [Line Items]  
Percent of Net Asset Value 6.20%
Fidelity ZERO Large Cap Index Fund | TH2Member  
Holdings [Line Items]  
Percent of Net Asset Value 5.50%
Fidelity ZERO Large Cap Index Fund | TH3Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.60%
Fidelity ZERO Large Cap Index Fund | TH4Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.50%
Fidelity ZERO Large Cap Index Fund | TH5Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.10%
Fidelity ZERO Large Cap Index Fund | TH6Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.90%
Fidelity ZERO Large Cap Index Fund | TH7Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.90%
Fidelity ZERO Large Cap Index Fund | TH8Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.60%
Fidelity ZERO Large Cap Index Fund | TH9Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.60%
Fidelity ZERO Large Cap Index Fund | MSFinancialsSectorMember  
Holdings [Line Items]  
Percent of Net Asset Value 14.50%
Fidelity ZERO Large Cap Index Fund | Information Technology Member  
Holdings [Line Items]  
Percent of Net Asset Value 30.60%
Fidelity ZERO Large Cap Index Fund | Healthcare Sector  
Holdings [Line Items]  
Percent of Net Asset Value 10.70%
Fidelity ZERO Large Cap Index Fund | Real Estate Sector  
Holdings [Line Items]  
Percent of Net Asset Value 2.20%
Fidelity ZERO Large Cap Index Fund | Industrial Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 8.50%
Fidelity ZERO Large Cap Index Fund | Materials Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.10%
Fidelity ZERO Large Cap Index Fund | Consumer Discretionary Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 10.20%
Fidelity ZERO Large Cap Index Fund | Consumer Staples Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 6.00%
Fidelity ZERO Large Cap Index Fund | Communications Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 9.20%
Fidelity ZERO Large Cap Index Fund | Energy Sector  
Holdings [Line Items]  
Percent of Net Asset Value 3.20%
Fidelity ZERO Large Cap Index Fund | Utilities Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.50%
Fidelity ZERO Large Cap Index Fund | United States  
Holdings [Line Items]  
Percent of Net Asset Value 99.30%
Fidelity ZERO Large Cap Index Fund | Ireland  
Holdings [Line Items]  
Percent of Net Asset Value 0.40%
Fidelity ZERO Large Cap Index Fund | Netherlands  
Holdings [Line Items]  
Percent of Net Asset Value 0.10%
Fidelity ZERO Large Cap Index Fund | Switzerland  
Holdings [Line Items]  
Percent of Net Asset Value 0.10%
Fidelity ZERO Large Cap Index Fund | United Kingdom  
Holdings [Line Items]  
Percent of Net Asset Value 0.10%
Fidelity ZERO Large Cap Index Fund | Canada  
Holdings [Line Items]  
Percent of Net Asset Value 0.00%
Fidelity ZERO Large Cap Index Fund | BailiwickOfJerseyMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.00%
Fidelity ZERO Large Cap Index Fund | AACommonStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 99.70%
Fidelity ZERO Large Cap Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.30%
Fidelity SAI Japan Stock Index Fund | TH0Member  
Holdings [Line Items]  
Percent of Net Asset Value 4.60%
Fidelity SAI Japan Stock Index Fund | TH1Member  
Holdings [Line Items]  
Percent of Net Asset Value 4.20%
Fidelity SAI Japan Stock Index Fund | TH2Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.80%
Fidelity SAI Japan Stock Index Fund | TH3Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.90%
Fidelity SAI Japan Stock Index Fund | TH4Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.30%
Fidelity SAI Japan Stock Index Fund | TH5Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.30%
Fidelity SAI Japan Stock Index Fund | TH6Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.10%
Fidelity SAI Japan Stock Index Fund | TH7Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.00%
Fidelity SAI Japan Stock Index Fund | TH8Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.80%
Fidelity SAI Japan Stock Index Fund | TH9Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.70%
Fidelity SAI Japan Stock Index Fund | MSFinancialsSectorMember  
Holdings [Line Items]  
Percent of Net Asset Value 15.80%
Fidelity SAI Japan Stock Index Fund | Information Technology Member  
Holdings [Line Items]  
Percent of Net Asset Value 12.80%
Fidelity SAI Japan Stock Index Fund | Healthcare Sector  
Holdings [Line Items]  
Percent of Net Asset Value 7.50%
Fidelity SAI Japan Stock Index Fund | Real Estate Sector  
Holdings [Line Items]  
Percent of Net Asset Value 2.40%
Fidelity SAI Japan Stock Index Fund | Industrial Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 23.00%
Fidelity SAI Japan Stock Index Fund | Materials Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.50%
Fidelity SAI Japan Stock Index Fund | Consumer Discretionary Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 18.30%
Fidelity SAI Japan Stock Index Fund | Consumer Staples Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 5.50%
Fidelity SAI Japan Stock Index Fund | Communications Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 8.20%
Fidelity SAI Japan Stock Index Fund | Energy Sector  
Holdings [Line Items]  
Percent of Net Asset Value 0.70%
Fidelity SAI Japan Stock Index Fund | Utilities Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.00%
Fidelity SAI Japan Stock Index Fund | United States  
Holdings [Line Items]  
Percent of Net Asset Value 1.30%
Fidelity SAI Japan Stock Index Fund | Japan  
Holdings [Line Items]  
Percent of Net Asset Value 98.70%
Fidelity SAI Japan Stock Index Fund | AACommonStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 98.70%
Fidelity SAI Japan Stock Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember  
Holdings [Line Items]  
Percent of Net Asset Value 1.30%
Fidelity SAI Canada Equity Index Fund | TH0Member  
Holdings [Line Items]  
Percent of Net Asset Value 7.70%
Fidelity SAI Canada Equity Index Fund | TH1Member  
Holdings [Line Items]  
Percent of Net Asset Value 5.20%
Fidelity SAI Canada Equity Index Fund | TH2Member  
Holdings [Line Items]  
Percent of Net Asset Value 5.10%
Fidelity SAI Canada Equity Index Fund | TH3Member  
Holdings [Line Items]  
Percent of Net Asset Value 4.70%
Fidelity SAI Canada Equity Index Fund | TH4Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.30%
Fidelity SAI Canada Equity Index Fund | TH5Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.30%
Fidelity SAI Canada Equity Index Fund | TH6Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.20%
Fidelity SAI Canada Equity Index Fund | TH7Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.10%
Fidelity SAI Canada Equity Index Fund | TH8Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.80%
Fidelity SAI Canada Equity Index Fund | TH9Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.80%
Fidelity SAI Canada Equity Index Fund | MSFinancialsSectorMember  
Holdings [Line Items]  
Percent of Net Asset Value 37.10%
Fidelity SAI Canada Equity Index Fund | Information Technology Member  
Holdings [Line Items]  
Percent of Net Asset Value 10.60%
Fidelity SAI Canada Equity Index Fund | Real Estate Sector  
Holdings [Line Items]  
Percent of Net Asset Value 0.30%
Fidelity SAI Canada Equity Index Fund | Industrial Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 11.00%
Fidelity SAI Canada Equity Index Fund | Materials Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 12.10%
Fidelity SAI Canada Equity Index Fund | Consumer Discretionary Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.40%
Fidelity SAI Canada Equity Index Fund | Consumer Staples Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 4.60%
Fidelity SAI Canada Equity Index Fund | Communications Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.00%
Fidelity SAI Canada Equity Index Fund | Energy Sector  
Holdings [Line Items]  
Percent of Net Asset Value 16.50%
Fidelity SAI Canada Equity Index Fund | Utilities Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.00%
Fidelity SAI Canada Equity Index Fund | United States  
Holdings [Line Items]  
Percent of Net Asset Value 0.90%
Fidelity SAI Canada Equity Index Fund | Canada  
Holdings [Line Items]  
Percent of Net Asset Value 96.40%
Fidelity SAI Canada Equity Index Fund | Brazil  
Holdings [Line Items]  
Percent of Net Asset Value 1.70%
Fidelity SAI Canada Equity Index Fund | Zambia  
Holdings [Line Items]  
Percent of Net Asset Value 0.40%
Fidelity SAI Canada Equity Index Fund | CongoDemocraticRepublicOfMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.30%
Fidelity SAI Canada Equity Index Fund | Chile  
Holdings [Line Items]  
Percent of Net Asset Value 0.30%
Fidelity SAI Canada Equity Index Fund | AACommonStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 99.60%
Fidelity SAI Canada Equity Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.40%
Fidelity ZERO Extended Market Index Fund | TH0Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.40%
Fidelity ZERO Extended Market Index Fund | TH1Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.40%
Fidelity ZERO Extended Market Index Fund | TH2Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.40%
Fidelity ZERO Extended Market Index Fund | TH3Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.40%
Fidelity ZERO Extended Market Index Fund | TH4Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.40%
Fidelity ZERO Extended Market Index Fund | TH5Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.40%
Fidelity ZERO Extended Market Index Fund | TH6Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.40%
Fidelity ZERO Extended Market Index Fund | TH7Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.40%
Fidelity ZERO Extended Market Index Fund | TH8Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.40%
Fidelity ZERO Extended Market Index Fund | TH9Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.40%
Fidelity ZERO Extended Market Index Fund | MSFinancialsSectorMember  
Holdings [Line Items]  
Percent of Net Asset Value 18.20%
Fidelity ZERO Extended Market Index Fund | Information Technology Member  
Holdings [Line Items]  
Percent of Net Asset Value 11.90%
Fidelity ZERO Extended Market Index Fund | Healthcare Sector  
Holdings [Line Items]  
Percent of Net Asset Value 12.20%
Fidelity ZERO Extended Market Index Fund | Real Estate Sector  
Holdings [Line Items]  
Percent of Net Asset Value 7.00%
Fidelity ZERO Extended Market Index Fund | Industrial Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 19.30%
Fidelity ZERO Extended Market Index Fund | Materials Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 5.10%
Fidelity ZERO Extended Market Index Fund | Consumer Discretionary Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 12.00%
Fidelity ZERO Extended Market Index Fund | Consumer Staples Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 4.50%
Fidelity ZERO Extended Market Index Fund | Communications Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.60%
Fidelity ZERO Extended Market Index Fund | Energy Sector  
Holdings [Line Items]  
Percent of Net Asset Value 3.30%
Fidelity ZERO Extended Market Index Fund | Utilities Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.70%
Fidelity ZERO Extended Market Index Fund | United States  
Holdings [Line Items]  
Percent of Net Asset Value 98.30%
Fidelity ZERO Extended Market Index Fund | Switzerland  
Holdings [Line Items]  
Percent of Net Asset Value 0.10%
Fidelity ZERO Extended Market Index Fund | United Kingdom  
Holdings [Line Items]  
Percent of Net Asset Value 0.60%
Fidelity ZERO Extended Market Index Fund | Canada  
Holdings [Line Items]  
Percent of Net Asset Value 0.10%
Fidelity ZERO Extended Market Index Fund | Puerto Rico  
Holdings [Line Items]  
Percent of Net Asset Value 0.30%
Fidelity ZERO Extended Market Index Fund | Bermuda  
Holdings [Line Items]  
Percent of Net Asset Value 0.20%
Fidelity ZERO Extended Market Index Fund | Sweden  
Holdings [Line Items]  
Percent of Net Asset Value 0.20%
Fidelity ZERO Extended Market Index Fund | Thailand  
Holdings [Line Items]  
Percent of Net Asset Value 0.10%
Fidelity ZERO Extended Market Index Fund | Belgium  
Holdings [Line Items]  
Percent of Net Asset Value 0.10%
Fidelity ZERO Extended Market Index Fund | AACommonStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 99.80%
Fidelity ZERO Extended Market Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.20%
Fidelity SAI International Small Cap Index Fund | TH0Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.50%
Fidelity SAI International Small Cap Index Fund | TH1Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.40%
Fidelity SAI International Small Cap Index Fund | TH2Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.40%
Fidelity SAI International Small Cap Index Fund | TH3Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.40%
Fidelity SAI International Small Cap Index Fund | TH4Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.40%
Fidelity SAI International Small Cap Index Fund | TH5Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.40%
Fidelity SAI International Small Cap Index Fund | TH6Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.30%
Fidelity SAI International Small Cap Index Fund | TH7Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.30%
Fidelity SAI International Small Cap Index Fund | TH8Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.30%
Fidelity SAI International Small Cap Index Fund | TH9Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.30%
Fidelity SAI International Small Cap Index Fund | MSFinancialsSectorMember  
Holdings [Line Items]  
Percent of Net Asset Value 13.40%
Fidelity SAI International Small Cap Index Fund | Information Technology Member  
Holdings [Line Items]  
Percent of Net Asset Value 8.20%
Fidelity SAI International Small Cap Index Fund | Healthcare Sector  
Holdings [Line Items]  
Percent of Net Asset Value 5.40%
Fidelity SAI International Small Cap Index Fund | Real Estate Sector  
Holdings [Line Items]  
Percent of Net Asset Value 11.50%
Fidelity SAI International Small Cap Index Fund | Industrial Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 23.20%
Fidelity SAI International Small Cap Index Fund | Materials Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 9.40%
Fidelity SAI International Small Cap Index Fund | Consumer Discretionary Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 12.70%
Fidelity SAI International Small Cap Index Fund | Consumer Staples Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 5.90%
Fidelity SAI International Small Cap Index Fund | Communications Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 4.20%
Fidelity SAI International Small Cap Index Fund | Energy Sector  
Holdings [Line Items]  
Percent of Net Asset Value 2.50%
Fidelity SAI International Small Cap Index Fund | Utilities Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.40%
Fidelity SAI International Small Cap Index Fund | Switzerland  
Holdings [Line Items]  
Percent of Net Asset Value 4.60%
Fidelity SAI International Small Cap Index Fund | United Kingdom  
Holdings [Line Items]  
Percent of Net Asset Value 12.60%
Fidelity SAI International Small Cap Index Fund | Japan  
Holdings [Line Items]  
Percent of Net Asset Value 36.10%
Fidelity SAI International Small Cap Index Fund | Sweden  
Holdings [Line Items]  
Percent of Net Asset Value 5.30%
Fidelity SAI International Small Cap Index Fund | Australia  
Holdings [Line Items]  
Percent of Net Asset Value 9.70%
Fidelity SAI International Small Cap Index Fund | Germany  
Holdings [Line Items]  
Percent of Net Asset Value 4.20%
Fidelity SAI International Small Cap Index Fund | France  
Holdings [Line Items]  
Percent of Net Asset Value 3.30%
Fidelity SAI International Small Cap Index Fund | Italy  
Holdings [Line Items]  
Percent of Net Asset Value 3.10%
Fidelity SAI International Small Cap Index Fund | Israel  
Holdings [Line Items]  
Percent of Net Asset Value 3.10%
Fidelity SAI International Small Cap Index Fund | OtherMember  
Holdings [Line Items]  
Percent of Net Asset Value 18.00%
Fidelity SAI International Small Cap Index Fund | AACommonStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 98.50%
Fidelity SAI International Small Cap Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember  
Holdings [Line Items]  
Percent of Net Asset Value 1.20%
Fidelity SAI International Small Cap Index Fund | AAPreferredStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.30%
Fidelity ZERO International Index Fund | TH0Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.40%
Fidelity ZERO International Index Fund | TH1Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.30%
Fidelity ZERO International Index Fund | TH2Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.10%
Fidelity ZERO International Index Fund | TH3Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.00%
Fidelity ZERO International Index Fund | TH4Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.00%
Fidelity ZERO International Index Fund | TH5Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.90%
Fidelity ZERO International Index Fund | TH6Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.80%
Fidelity ZERO International Index Fund | TH7Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.80%
Fidelity ZERO International Index Fund | TH8Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.80%
Fidelity ZERO International Index Fund | TH9Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.70%
Fidelity ZERO International Index Fund | MSFinancialsSectorMember  
Holdings [Line Items]  
Percent of Net Asset Value 25.30%
Fidelity ZERO International Index Fund | Information Technology Member  
Holdings [Line Items]  
Percent of Net Asset Value 12.10%
Fidelity ZERO International Index Fund | Healthcare Sector  
Holdings [Line Items]  
Percent of Net Asset Value 7.70%
Fidelity ZERO International Index Fund | Real Estate Sector  
Holdings [Line Items]  
Percent of Net Asset Value 1.70%
Fidelity ZERO International Index Fund | Industrial Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 14.50%
Fidelity ZERO International Index Fund | Materials Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 5.90%
Fidelity ZERO International Index Fund | Consumer Discretionary Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 10.70%
Fidelity ZERO International Index Fund | Consumer Staples Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 6.80%
Fidelity ZERO International Index Fund | Communications Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 5.60%
Fidelity ZERO International Index Fund | Energy Sector  
Holdings [Line Items]  
Percent of Net Asset Value 3.90%
Fidelity ZERO International Index Fund | Utilities Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.90%
Fidelity ZERO International Index Fund | United States  
Holdings [Line Items]  
Percent of Net Asset Value 9.50%
Fidelity ZERO International Index Fund | United Kingdom  
Holdings [Line Items]  
Percent of Net Asset Value 7.30%
Fidelity ZERO International Index Fund | Canada  
Holdings [Line Items]  
Percent of Net Asset Value 7.40%
Fidelity ZERO International Index Fund | Japan  
Holdings [Line Items]  
Percent of Net Asset Value 16.40%
Fidelity ZERO International Index Fund | Australia  
Holdings [Line Items]  
Percent of Net Asset Value 4.50%
Fidelity ZERO International Index Fund | Germany  
Holdings [Line Items]  
Percent of Net Asset Value 6.00%
Fidelity ZERO International Index Fund | France  
Holdings [Line Items]  
Percent of Net Asset Value 5.40%
Fidelity ZERO International Index Fund | OtherMember  
Holdings [Line Items]  
Percent of Net Asset Value 31.40%
Fidelity ZERO International Index Fund | China  
Holdings [Line Items]  
Percent of Net Asset Value 7.10%
Fidelity ZERO International Index Fund | Taiwan  
Holdings [Line Items]  
Percent of Net Asset Value 5.00%
Fidelity ZERO International Index Fund | AACommonStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 96.80%
Fidelity ZERO International Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember  
Holdings [Line Items]  
Percent of Net Asset Value 2.90%
Fidelity ZERO International Index Fund | AAPreferredStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.30%
Fidelity ZERO Total Market Index Fund | TH0Member  
Holdings [Line Items]  
Percent of Net Asset Value 6.00%
Fidelity ZERO Total Market Index Fund | TH1Member  
Holdings [Line Items]  
Percent of Net Asset Value 5.60%
Fidelity ZERO Total Market Index Fund | TH2Member  
Holdings [Line Items]  
Percent of Net Asset Value 5.10%
Fidelity ZERO Total Market Index Fund | TH3Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.20%
Fidelity ZERO Total Market Index Fund | TH4Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.30%
Fidelity ZERO Total Market Index Fund | TH5Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.90%
Fidelity ZERO Total Market Index Fund | TH6Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.80%
Fidelity ZERO Total Market Index Fund | TH7Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.70%
Fidelity ZERO Total Market Index Fund | TH8Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.50%
Fidelity ZERO Total Market Index Fund | TH9Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.40%
Fidelity ZERO Total Market Index Fund | MSFinancialsSectorMember  
Holdings [Line Items]  
Percent of Net Asset Value 14.80%
Fidelity ZERO Total Market Index Fund | Information Technology Member  
Holdings [Line Items]  
Percent of Net Asset Value 28.90%
Fidelity ZERO Total Market Index Fund | Healthcare Sector  
Holdings [Line Items]  
Percent of Net Asset Value 10.90%
Fidelity ZERO Total Market Index Fund | Real Estate Sector  
Holdings [Line Items]  
Percent of Net Asset Value 2.70%
Fidelity ZERO Total Market Index Fund | Industrial Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 9.60%
Fidelity ZERO Total Market Index Fund | Materials Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.30%
Fidelity ZERO Total Market Index Fund | Consumer Discretionary Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 10.40%
Fidelity ZERO Total Market Index Fund | Consumer Staples Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 5.80%
Fidelity ZERO Total Market Index Fund | Communications Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 8.60%
Fidelity ZERO Total Market Index Fund | Energy Sector  
Holdings [Line Items]  
Percent of Net Asset Value 3.20%
Fidelity ZERO Total Market Index Fund | Utilities Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.50%
Fidelity ZERO Total Market Index Fund | United States  
Holdings [Line Items]  
Percent of Net Asset Value 99.30%
Fidelity ZERO Total Market Index Fund | Ireland  
Holdings [Line Items]  
Percent of Net Asset Value 0.40%
Fidelity ZERO Total Market Index Fund | Netherlands  
Holdings [Line Items]  
Percent of Net Asset Value 0.10%
Fidelity ZERO Total Market Index Fund | Switzerland  
Holdings [Line Items]  
Percent of Net Asset Value 0.10%
Fidelity ZERO Total Market Index Fund | United Kingdom  
Holdings [Line Items]  
Percent of Net Asset Value 0.10%
Fidelity ZERO Total Market Index Fund | Canada  
Holdings [Line Items]  
Percent of Net Asset Value 0.00%
Fidelity ZERO Total Market Index Fund | BailiwickOfJerseyMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.00%
Fidelity ZERO Total Market Index Fund | Puerto Rico  
Holdings [Line Items]  
Percent of Net Asset Value 0.00%
Fidelity ZERO Total Market Index Fund | Bermuda  
Holdings [Line Items]  
Percent of Net Asset Value 0.00%
Fidelity ZERO Total Market Index Fund | AACommonStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 99.70%
Fidelity ZERO Total Market Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.30%
Fidelity SAI Global ex U.S. Low Volatility Index Fund | TH0Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.50%
Fidelity SAI Global ex U.S. Low Volatility Index Fund | TH1Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.30%
Fidelity SAI Global ex U.S. Low Volatility Index Fund | TH2Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.20%
Fidelity SAI Global ex U.S. Low Volatility Index Fund | TH3Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.20%
Fidelity SAI Global ex U.S. Low Volatility Index Fund | TH4Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.10%
Fidelity SAI Global ex U.S. Low Volatility Index Fund | TH5Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.80%
Fidelity SAI Global ex U.S. Low Volatility Index Fund | TH6Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.70%
Fidelity SAI Global ex U.S. Low Volatility Index Fund | TH7Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.70%
Fidelity SAI Global ex U.S. Low Volatility Index Fund | TH8Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.70%
Fidelity SAI Global ex U.S. Low Volatility Index Fund | TH9Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.70%
Fidelity SAI Global ex U.S. Low Volatility Index Fund | MSFinancialsSectorMember  
Holdings [Line Items]  
Percent of Net Asset Value 23.20%
Fidelity SAI Global ex U.S. Low Volatility Index Fund | Information Technology Member  
Holdings [Line Items]  
Percent of Net Asset Value 5.90%
Fidelity SAI Global ex U.S. Low Volatility Index Fund | Healthcare Sector  
Holdings [Line Items]  
Percent of Net Asset Value 11.90%
Fidelity SAI Global ex U.S. Low Volatility Index Fund | Real Estate Sector  
Holdings [Line Items]  
Percent of Net Asset Value 2.50%
Fidelity SAI Global ex U.S. Low Volatility Index Fund | Industrial Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 10.20%
Fidelity SAI Global ex U.S. Low Volatility Index Fund | Materials Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.10%
Fidelity SAI Global ex U.S. Low Volatility Index Fund | Consumer Discretionary Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 6.30%
Fidelity SAI Global ex U.S. Low Volatility Index Fund | Consumer Staples Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 10.70%
Fidelity SAI Global ex U.S. Low Volatility Index Fund | Communications Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 10.90%
Fidelity SAI Global ex U.S. Low Volatility Index Fund | Energy Sector  
Holdings [Line Items]  
Percent of Net Asset Value 2.30%
Fidelity SAI Global ex U.S. Low Volatility Index Fund | Utilities Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 8.20%
Fidelity SAI Global ex U.S. Low Volatility Index Fund | United States  
Holdings [Line Items]  
Percent of Net Asset Value 15.70%
Fidelity SAI Global ex U.S. Low Volatility Index Fund | Switzerland  
Holdings [Line Items]  
Percent of Net Asset Value 3.80%
Fidelity SAI Global ex U.S. Low Volatility Index Fund | United Kingdom  
Holdings [Line Items]  
Percent of Net Asset Value 6.20%
Fidelity SAI Global ex U.S. Low Volatility Index Fund | Canada  
Holdings [Line Items]  
Percent of Net Asset Value 10.10%
Fidelity SAI Global ex U.S. Low Volatility Index Fund | Japan  
Holdings [Line Items]  
Percent of Net Asset Value 20.40%
Fidelity SAI Global ex U.S. Low Volatility Index Fund | OtherMember  
Holdings [Line Items]  
Percent of Net Asset Value 15.90%
Fidelity SAI Global ex U.S. Low Volatility Index Fund | China  
Holdings [Line Items]  
Percent of Net Asset Value 11.90%
Fidelity SAI Global ex U.S. Low Volatility Index Fund | Taiwan  
Holdings [Line Items]  
Percent of Net Asset Value 9.20%
Fidelity SAI Global ex U.S. Low Volatility Index Fund | Saudi Arabia  
Holdings [Line Items]  
Percent of Net Asset Value 3.50%
Fidelity SAI Global ex U.S. Low Volatility Index Fund | Hong Kong  
Holdings [Line Items]  
Percent of Net Asset Value 3.30%
Fidelity SAI Global ex U.S. Low Volatility Index Fund | AACommonStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 94.20%
Fidelity SAI Global ex U.S. Low Volatility Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember  
Holdings [Line Items]  
Percent of Net Asset Value 2.30%
Fidelity SAI Global ex U.S. Low Volatility Index Fund | AAInternationalEquityFundsMember  
Holdings [Line Items]  
Percent of Net Asset Value 3.50%
Fidelity Series International Index Fund | TH0Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.80%
Fidelity Series International Index Fund | TH1Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.60%
Fidelity Series International Index Fund | TH2Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.50%
Fidelity Series International Index Fund | TH3Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.30%
Fidelity Series International Index Fund | TH4Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.20%
Fidelity Series International Index Fund | TH5Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.20%
Fidelity Series International Index Fund | TH6Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.20%
Fidelity Series International Index Fund | TH7Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.20%
Fidelity Series International Index Fund | TH8Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.10%
Fidelity Series International Index Fund | TH9Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.00%
Fidelity Series International Index Fund | MSFinancialsSectorMember  
Holdings [Line Items]  
Percent of Net Asset Value 23.20%
Fidelity Series International Index Fund | Information Technology Member  
Holdings [Line Items]  
Percent of Net Asset Value 8.00%
Fidelity Series International Index Fund | Healthcare Sector  
Holdings [Line Items]  
Percent of Net Asset Value 11.70%
Fidelity Series International Index Fund | Real Estate Sector  
Holdings [Line Items]  
Percent of Net Asset Value 1.80%
Fidelity Series International Index Fund | Industrial Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 18.00%
Fidelity Series International Index Fund | Materials Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 5.50%
Fidelity Series International Index Fund | Consumer Discretionary Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 10.10%
Fidelity Series International Index Fund | Consumer Staples Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 8.50%
Fidelity Series International Index Fund | Communications Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 5.10%
Fidelity Series International Index Fund | Energy Sector  
Holdings [Line Items]  
Percent of Net Asset Value 3.00%
Fidelity Series International Index Fund | Utilities Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.20%
Fidelity Series International Index Fund | United States  
Holdings [Line Items]  
Percent of Net Asset Value 12.30%
Fidelity Series International Index Fund | Netherlands  
Holdings [Line Items]  
Percent of Net Asset Value 3.90%
Fidelity Series International Index Fund | Switzerland  
Holdings [Line Items]  
Percent of Net Asset Value 4.80%
Fidelity Series International Index Fund | United Kingdom  
Holdings [Line Items]  
Percent of Net Asset Value 11.40%
Fidelity Series International Index Fund | Japan  
Holdings [Line Items]  
Percent of Net Asset Value 21.60%
Fidelity Series International Index Fund | Sweden  
Holdings [Line Items]  
Percent of Net Asset Value 3.10%
Fidelity Series International Index Fund | Australia  
Holdings [Line Items]  
Percent of Net Asset Value 6.60%
Fidelity Series International Index Fund | Germany  
Holdings [Line Items]  
Percent of Net Asset Value 10.10%
Fidelity Series International Index Fund | France  
Holdings [Line Items]  
Percent of Net Asset Value 9.50%
Fidelity Series International Index Fund | OtherMember  
Holdings [Line Items]  
Percent of Net Asset Value 16.70%
Fidelity Series International Index Fund | AACommonStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 97.80%
Fidelity Series International Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember  
Holdings [Line Items]  
Percent of Net Asset Value 1.90%
Fidelity Series International Index Fund | AAPreferredStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.30%