v3.26.3
Shareholder Report, Holdings (Details)
Jul. 31, 2026
Fidelity SAI U.S. Value Index Fund | TH0Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.80%
Fidelity SAI U.S. Value Index Fund | TH1Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.60%
Fidelity SAI U.S. Value Index Fund | TH2Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.60%
Fidelity SAI U.S. Value Index Fund | TH3Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.60%
Fidelity SAI U.S. Value Index Fund | TH4Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.20%
Fidelity SAI U.S. Value Index Fund | TH5Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.90%
Fidelity SAI U.S. Value Index Fund | TH6Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.60%
Fidelity SAI U.S. Value Index Fund | TH7Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.30%
Fidelity SAI U.S. Value Index Fund | TH8Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.20%
Fidelity SAI U.S. Value Index Fund | TH9Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.90%
Fidelity SAI U.S. Value Index Fund | MSFinancialsSectorMember  
Holdings [Line Items]  
Percent of Net Asset Value 21.70%
Fidelity SAI U.S. Value Index Fund | Information Technology Member  
Holdings [Line Items]  
Percent of Net Asset Value 25.50%
Fidelity SAI U.S. Value Index Fund | Healthcare Sector  
Holdings [Line Items]  
Percent of Net Asset Value 12.50%
Fidelity SAI U.S. Value Index Fund | Real Estate Sector  
Holdings [Line Items]  
Percent of Net Asset Value 0.30%
Fidelity SAI U.S. Value Index Fund | Industrial Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.70%
Fidelity SAI U.S. Value Index Fund | Materials Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.80%
Fidelity SAI U.S. Value Index Fund | Consumer Discretionary Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 4.30%
Fidelity SAI U.S. Value Index Fund | Consumer Staples Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 4.20%
Fidelity SAI U.S. Value Index Fund | Communications Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 10.30%
Fidelity SAI U.S. Value Index Fund | Energy Sector  
Holdings [Line Items]  
Percent of Net Asset Value 12.60%
Fidelity SAI U.S. Value Index Fund | Utilities Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.90%
Fidelity SAI U.S. Value Index Fund | United States  
Holdings [Line Items]  
Percent of Net Asset Value 99.00%
Fidelity SAI U.S. Value Index Fund | Switzerland  
Holdings [Line Items]  
Percent of Net Asset Value 0.60%
Fidelity SAI U.S. Value Index Fund | Australia  
Holdings [Line Items]  
Percent of Net Asset Value 0.30%
Fidelity SAI U.S. Value Index Fund | Bermuda  
Holdings [Line Items]  
Percent of Net Asset Value 0.10%
Fidelity SAI U.S. Value Index Fund | AACommonStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 99.80%
Fidelity SAI U.S. Value Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.20%
Fidelity SAI U.S. Quality Index Fund | TH0Member  
Holdings [Line Items]  
Percent of Net Asset Value 9.20%
Fidelity SAI U.S. Quality Index Fund | TH1Member  
Holdings [Line Items]  
Percent of Net Asset Value 8.00%
Fidelity SAI U.S. Quality Index Fund | TH2Member  
Holdings [Line Items]  
Percent of Net Asset Value 4.30%
Fidelity SAI U.S. Quality Index Fund | TH3Member  
Holdings [Line Items]  
Percent of Net Asset Value 4.30%
Fidelity SAI U.S. Quality Index Fund | TH4Member  
Holdings [Line Items]  
Percent of Net Asset Value 4.20%
Fidelity SAI U.S. Quality Index Fund | TH5Member  
Holdings [Line Items]  
Percent of Net Asset Value 4.10%
Fidelity SAI U.S. Quality Index Fund | TH6Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.90%
Fidelity SAI U.S. Quality Index Fund | TH7Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.50%
Fidelity SAI U.S. Quality Index Fund | TH8Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.30%
Fidelity SAI U.S. Quality Index Fund | TH9Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.30%
Fidelity SAI U.S. Quality Index Fund | MSFinancialsSectorMember  
Holdings [Line Items]  
Percent of Net Asset Value 16.00%
Fidelity SAI U.S. Quality Index Fund | Information Technology Member  
Holdings [Line Items]  
Percent of Net Asset Value 38.90%
Fidelity SAI U.S. Quality Index Fund | Healthcare Sector  
Holdings [Line Items]  
Percent of Net Asset Value 13.90%
Fidelity SAI U.S. Quality Index Fund | Real Estate Sector  
Holdings [Line Items]  
Percent of Net Asset Value 1.60%
Fidelity SAI U.S. Quality Index Fund | Industrial Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 7.30%
Fidelity SAI U.S. Quality Index Fund | Consumer Discretionary Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 4.40%
Fidelity SAI U.S. Quality Index Fund | Consumer Staples Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 9.50%
Fidelity SAI U.S. Quality Index Fund | Communications Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 8.00%
Fidelity SAI U.S. Quality Index Fund | Energy Sector  
Holdings [Line Items]  
Percent of Net Asset Value 0.20%
Fidelity SAI U.S. Quality Index Fund | United States  
Holdings [Line Items]  
Percent of Net Asset Value 100.00%
Fidelity SAI U.S. Quality Index Fund | AACommonStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 99.80%
Fidelity SAI U.S. Quality Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.20%
Fidelity SAI U.S. Momentum Index Fund | TH0Member  
Holdings [Line Items]  
Percent of Net Asset Value 8.90%
Fidelity SAI U.S. Momentum Index Fund | TH1Member  
Holdings [Line Items]  
Percent of Net Asset Value 4.40%
Fidelity SAI U.S. Momentum Index Fund | TH2Member  
Holdings [Line Items]  
Percent of Net Asset Value 4.20%
Fidelity SAI U.S. Momentum Index Fund | TH3Member  
Holdings [Line Items]  
Percent of Net Asset Value 4.00%
Fidelity SAI U.S. Momentum Index Fund | TH4Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.70%
Fidelity SAI U.S. Momentum Index Fund | TH5Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.10%
Fidelity SAI U.S. Momentum Index Fund | TH6Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.00%
Fidelity SAI U.S. Momentum Index Fund | TH7Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.90%
Fidelity SAI U.S. Momentum Index Fund | TH8Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.90%
Fidelity SAI U.S. Momentum Index Fund | TH9Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.80%
Fidelity SAI U.S. Momentum Index Fund | MSFinancialsSectorMember  
Holdings [Line Items]  
Percent of Net Asset Value 8.30%
Fidelity SAI U.S. Momentum Index Fund | Information Technology Member  
Holdings [Line Items]  
Percent of Net Asset Value 39.40%
Fidelity SAI U.S. Momentum Index Fund | Healthcare Sector  
Holdings [Line Items]  
Percent of Net Asset Value 7.60%
Fidelity SAI U.S. Momentum Index Fund | Real Estate Sector  
Holdings [Line Items]  
Percent of Net Asset Value 2.60%
Fidelity SAI U.S. Momentum Index Fund | Industrial Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 14.80%
Fidelity SAI U.S. Momentum Index Fund | Materials Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.20%
Fidelity SAI U.S. Momentum Index Fund | Consumer Discretionary Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 4.70%
Fidelity SAI U.S. Momentum Index Fund | Consumer Staples Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.70%
Fidelity SAI U.S. Momentum Index Fund | Communications Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 9.10%
Fidelity SAI U.S. Momentum Index Fund | Energy Sector  
Holdings [Line Items]  
Percent of Net Asset Value 7.60%
Fidelity SAI U.S. Momentum Index Fund | Utilities Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.90%
Fidelity SAI U.S. Momentum Index Fund | United States  
Holdings [Line Items]  
Percent of Net Asset Value 99.40%
Fidelity SAI U.S. Momentum Index Fund | Australia  
Holdings [Line Items]  
Percent of Net Asset Value 0.20%
Fidelity SAI U.S. Momentum Index Fund | Bermuda  
Holdings [Line Items]  
Percent of Net Asset Value 0.10%
Fidelity SAI U.S. Momentum Index Fund | United Kingdom  
Holdings [Line Items]  
Percent of Net Asset Value 0.20%
Fidelity SAI U.S. Momentum Index Fund | Thailand  
Holdings [Line Items]  
Percent of Net Asset Value 0.10%
Fidelity SAI U.S. Momentum Index Fund | AACommonStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 99.90%
Fidelity SAI U.S. Momentum Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.10%
Fidelity SAI U.S. Large Cap Index Fund | TH0Member  
Holdings [Line Items]  
Percent of Net Asset Value 7.50%
Fidelity SAI U.S. Large Cap Index Fund | TH1Member  
Holdings [Line Items]  
Percent of Net Asset Value 7.00%
Fidelity SAI U.S. Large Cap Index Fund | TH2Member  
Holdings [Line Items]  
Percent of Net Asset Value 5.50%
Fidelity SAI U.S. Large Cap Index Fund | TH3Member  
Holdings [Line Items]  
Percent of Net Asset Value 4.10%
Fidelity SAI U.S. Large Cap Index Fund | TH4Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.30%
Fidelity SAI U.S. Large Cap Index Fund | TH5Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.90%
Fidelity SAI U.S. Large Cap Index Fund | TH6Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.60%
Fidelity SAI U.S. Large Cap Index Fund | TH7Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.90%
Fidelity SAI U.S. Large Cap Index Fund | TH8Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.60%
Fidelity SAI U.S. Large Cap Index Fund | TH9Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.50%
Fidelity SAI U.S. Large Cap Index Fund | MSFinancialsSectorMember  
Holdings [Line Items]  
Percent of Net Asset Value 12.50%
Fidelity SAI U.S. Large Cap Index Fund | Information Technology Member  
Holdings [Line Items]  
Percent of Net Asset Value 36.70%
Fidelity SAI U.S. Large Cap Index Fund | Healthcare Sector  
Holdings [Line Items]  
Percent of Net Asset Value 9.10%
Fidelity SAI U.S. Large Cap Index Fund | Real Estate Sector  
Holdings [Line Items]  
Percent of Net Asset Value 1.90%
Fidelity SAI U.S. Large Cap Index Fund | Industrial Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 8.70%
Fidelity SAI U.S. Large Cap Index Fund | Materials Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.70%
Fidelity SAI U.S. Large Cap Index Fund | Consumer Discretionary Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 9.40%
Fidelity SAI U.S. Large Cap Index Fund | Consumer Staples Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 4.70%
Fidelity SAI U.S. Large Cap Index Fund | Communications Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 9.70%
Fidelity SAI U.S. Large Cap Index Fund | Energy Sector  
Holdings [Line Items]  
Percent of Net Asset Value 3.40%
Fidelity SAI U.S. Large Cap Index Fund | Utilities Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.10%
Fidelity SAI U.S. Large Cap Index Fund | United States  
Holdings [Line Items]  
Percent of Net Asset Value 99.80%
Fidelity SAI U.S. Large Cap Index Fund | Switzerland  
Holdings [Line Items]  
Percent of Net Asset Value 0.10%
Fidelity SAI U.S. Large Cap Index Fund | Netherlands  
Holdings [Line Items]  
Percent of Net Asset Value 0.10%
Fidelity SAI U.S. Large Cap Index Fund | AACommonStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 99.90%
Fidelity SAI U.S. Large Cap Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.10%
Fidelity SAI Small-Mid Cap Momentum Index Fund | TH0Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.40%
Fidelity SAI Small-Mid Cap Momentum Index Fund | TH1Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.30%
Fidelity SAI Small-Mid Cap Momentum Index Fund | TH2Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.30%
Fidelity SAI Small-Mid Cap Momentum Index Fund | TH3Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.30%
Fidelity SAI Small-Mid Cap Momentum Index Fund | TH4Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.20%
Fidelity SAI Small-Mid Cap Momentum Index Fund | TH5Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.20%
Fidelity SAI Small-Mid Cap Momentum Index Fund | TH6Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.20%
Fidelity SAI Small-Mid Cap Momentum Index Fund | TH7Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.20%
Fidelity SAI Small-Mid Cap Momentum Index Fund | TH8Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.20%
Fidelity SAI Small-Mid Cap Momentum Index Fund | TH9Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.20%
Fidelity SAI Small-Mid Cap Momentum Index Fund | MSFinancialsSectorMember  
Holdings [Line Items]  
Percent of Net Asset Value 13.00%
Fidelity SAI Small-Mid Cap Momentum Index Fund | Information Technology Member  
Holdings [Line Items]  
Percent of Net Asset Value 17.90%
Fidelity SAI Small-Mid Cap Momentum Index Fund | Healthcare Sector  
Holdings [Line Items]  
Percent of Net Asset Value 11.60%
Fidelity SAI Small-Mid Cap Momentum Index Fund | Real Estate Sector  
Holdings [Line Items]  
Percent of Net Asset Value 6.30%
Fidelity SAI Small-Mid Cap Momentum Index Fund | Industrial Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 22.50%
Fidelity SAI Small-Mid Cap Momentum Index Fund | Materials Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.30%
Fidelity SAI Small-Mid Cap Momentum Index Fund | Consumer Discretionary Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 6.60%
Fidelity SAI Small-Mid Cap Momentum Index Fund | Consumer Staples Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.80%
Fidelity SAI Small-Mid Cap Momentum Index Fund | Communications Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 4.20%
Fidelity SAI Small-Mid Cap Momentum Index Fund | Energy Sector  
Holdings [Line Items]  
Percent of Net Asset Value 10.30%
Fidelity SAI Small-Mid Cap Momentum Index Fund | Utilities Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.30%
Fidelity SAI Small-Mid Cap Momentum Index Fund | United States  
Holdings [Line Items]  
Percent of Net Asset Value 95.90%
Fidelity SAI Small-Mid Cap Momentum Index Fund | Switzerland  
Holdings [Line Items]  
Percent of Net Asset Value 0.30%
Fidelity SAI Small-Mid Cap Momentum Index Fund | Bermuda  
Holdings [Line Items]  
Percent of Net Asset Value 1.00%
Fidelity SAI Small-Mid Cap Momentum Index Fund | Thailand  
Holdings [Line Items]  
Percent of Net Asset Value 1.10%
Fidelity SAI Small-Mid Cap Momentum Index Fund | Puerto Rico  
Holdings [Line Items]  
Percent of Net Asset Value 0.70%
Fidelity SAI Small-Mid Cap Momentum Index Fund | Singapore  
Holdings [Line Items]  
Percent of Net Asset Value 0.30%
Fidelity SAI Small-Mid Cap Momentum Index Fund | Monaco  
Holdings [Line Items]  
Percent of Net Asset Value 0.20%
Fidelity SAI Small-Mid Cap Momentum Index Fund | Norway  
Holdings [Line Items]  
Percent of Net Asset Value 0.20%
Fidelity SAI Small-Mid Cap Momentum Index Fund | Canada  
Holdings [Line Items]  
Percent of Net Asset Value 0.20%
Fidelity SAI Small-Mid Cap Momentum Index Fund | OtherMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.10%
Fidelity SAI Small-Mid Cap Momentum Index Fund | AACommonStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 99.80%
Fidelity SAI Small-Mid Cap Momentum Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.20%
Fidelity SAI Real Estate Index Fund | TH0Member  
Holdings [Line Items]  
Percent of Net Asset Value 9.20%
Fidelity SAI Real Estate Index Fund | TH1Member  
Holdings [Line Items]  
Percent of Net Asset Value 8.00%
Fidelity SAI Real Estate Index Fund | TH2Member  
Holdings [Line Items]  
Percent of Net Asset Value 5.40%
Fidelity SAI Real Estate Index Fund | TH3Member  
Holdings [Line Items]  
Percent of Net Asset Value 4.70%
Fidelity SAI Real Estate Index Fund | TH4Member  
Holdings [Line Items]  
Percent of Net Asset Value 4.10%
Fidelity SAI Real Estate Index Fund | TH5Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.90%
Fidelity SAI Real Estate Index Fund | TH6Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.60%
Fidelity SAI Real Estate Index Fund | TH7Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.40%
Fidelity SAI Real Estate Index Fund | TH8Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.80%
Fidelity SAI Real Estate Index Fund | TH9Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.80%
Fidelity SAI Real Estate Index Fund | TI0Member  
Holdings [Line Items]  
Percent of Net Asset Value 31.30%
Fidelity SAI Real Estate Index Fund | TI1Member  
Holdings [Line Items]  
Percent of Net Asset Value 17.00%
Fidelity SAI Real Estate Index Fund | TI2Member  
Holdings [Line Items]  
Percent of Net Asset Value 15.10%
Fidelity SAI Real Estate Index Fund | TI3Member  
Holdings [Line Items]  
Percent of Net Asset Value 11.30%
Fidelity SAI Real Estate Index Fund | TI4Member  
Holdings [Line Items]  
Percent of Net Asset Value 10.80%
Fidelity SAI Real Estate Index Fund | TI5Member  
Holdings [Line Items]  
Percent of Net Asset Value 6.60%
Fidelity SAI Real Estate Index Fund | TI6Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.00%
Fidelity SAI Real Estate Index Fund | TI7Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.90%
Fidelity SAI Real Estate Index Fund | TI8Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.90%
Fidelity SAI Real Estate Index Fund | United States  
Holdings [Line Items]  
Percent of Net Asset Value 100.00%
Fidelity SAI Real Estate Index Fund | AACommonStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 99.90%
Fidelity SAI Real Estate Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.10%
Fidelity Real Estate Index Fund | TH0Member  
Holdings [Line Items]  
Percent of Net Asset Value 9.20%
Fidelity Real Estate Index Fund | TH1Member  
Holdings [Line Items]  
Percent of Net Asset Value 8.00%
Fidelity Real Estate Index Fund | TH2Member  
Holdings [Line Items]  
Percent of Net Asset Value 5.30%
Fidelity Real Estate Index Fund | TH3Member  
Holdings [Line Items]  
Percent of Net Asset Value 4.70%
Fidelity Real Estate Index Fund | TH4Member  
Holdings [Line Items]  
Percent of Net Asset Value 4.10%
Fidelity Real Estate Index Fund | TH5Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.90%
Fidelity Real Estate Index Fund | TH6Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.60%
Fidelity Real Estate Index Fund | TH7Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.40%
Fidelity Real Estate Index Fund | TH8Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.80%
Fidelity Real Estate Index Fund | TH9Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.70%
Fidelity Real Estate Index Fund | TI0Member  
Holdings [Line Items]  
Percent of Net Asset Value 31.20%
Fidelity Real Estate Index Fund | TI1Member  
Holdings [Line Items]  
Percent of Net Asset Value 16.90%
Fidelity Real Estate Index Fund | TI2Member  
Holdings [Line Items]  
Percent of Net Asset Value 15.10%
Fidelity Real Estate Index Fund | TI3Member  
Holdings [Line Items]  
Percent of Net Asset Value 11.30%
Fidelity Real Estate Index Fund | TI4Member  
Holdings [Line Items]  
Percent of Net Asset Value 10.70%
Fidelity Real Estate Index Fund | TI5Member  
Holdings [Line Items]  
Percent of Net Asset Value 6.60%
Fidelity Real Estate Index Fund | TI6Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.90%
Fidelity Real Estate Index Fund | TI7Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.90%
Fidelity Real Estate Index Fund | TI8Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.00%
Fidelity Real Estate Index Fund | United States  
Holdings [Line Items]  
Percent of Net Asset Value 100.00%
Fidelity Real Estate Index Fund | AACommonStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 99.60%
Fidelity Real Estate Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.40%