v3.25.2
Shareholder Report, Holdings (Details)
Apr. 30, 2025
Fidelity Series Global ex U.S. Index Fund | TH0Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.60%
Fidelity Series Global ex U.S. Index Fund | TH1Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.50%
Fidelity Series Global ex U.S. Index Fund | TH2Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.10%
Fidelity Series Global ex U.S. Index Fund | TH3Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.00%
Fidelity Series Global ex U.S. Index Fund | TH4Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.00%
Fidelity Series Global ex U.S. Index Fund | TH5Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.90%
Fidelity Series Global ex U.S. Index Fund | TH6Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.90%
Fidelity Series Global ex U.S. Index Fund | TH7Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.80%
Fidelity Series Global ex U.S. Index Fund | TH8Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.80%
Fidelity Series Global ex U.S. Index Fund | TH9Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.80%
Fidelity Series Global ex U.S. Index Fund | MSFinancialsSectorMember  
Holdings [Line Items]  
Percent of Net Asset Value 25.60%
Fidelity Series Global ex U.S. Index Fund | Information Technology Member  
Holdings [Line Items]  
Percent of Net Asset Value 12.20%
Fidelity Series Global ex U.S. Index Fund | Healthcare Sector  
Holdings [Line Items]  
Percent of Net Asset Value 8.50%
Fidelity Series Global ex U.S. Index Fund | Real Estate Sector  
Holdings [Line Items]  
Percent of Net Asset Value 1.40%
Fidelity Series Global ex U.S. Index Fund | Industrial Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 14.20%
Fidelity Series Global ex U.S. Index Fund | Materials Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 6.00%
Fidelity Series Global ex U.S. Index Fund | Consumer Discretionary Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 10.80%
Fidelity Series Global ex U.S. Index Fund | Consumer Staples Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 7.40%
Fidelity Series Global ex U.S. Index Fund | Communications Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 6.30%
Fidelity Series Global ex U.S. Index Fund | Energy Sector  
Holdings [Line Items]  
Percent of Net Asset Value 4.30%
Fidelity Series Global ex U.S. Index Fund | Utilities Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.90%
Fidelity Series Global ex U.S. Index Fund | Japan  
Holdings [Line Items]  
Percent of Net Asset Value 14.00%
Fidelity Series Global ex U.S. Index Fund | China  
Holdings [Line Items]  
Percent of Net Asset Value 8.80%
Fidelity Series Global ex U.S. Index Fund | Canada  
Holdings [Line Items]  
Percent of Net Asset Value 7.70%
Fidelity Series Global ex U.S. Index Fund | United Kingdom  
Holdings [Line Items]  
Percent of Net Asset Value 7.30%
Fidelity Series Global ex U.S. Index Fund | United States  
Holdings [Line Items]  
Percent of Net Asset Value 7.20%
Fidelity Series Global ex U.S. Index Fund | Germany  
Holdings [Line Items]  
Percent of Net Asset Value 6.60%
Fidelity Series Global ex U.S. Index Fund | France  
Holdings [Line Items]  
Percent of Net Asset Value 6.10%
Fidelity Series Global ex U.S. Index Fund | India  
Holdings [Line Items]  
Percent of Net Asset Value 5.50%
Fidelity Series Global ex U.S. Index Fund | Taiwan  
Holdings [Line Items]  
Percent of Net Asset Value 4.80%
Fidelity Series Global ex U.S. Index Fund | OtherMember  
Holdings [Line Items]  
Percent of Net Asset Value 32.00%
Fidelity Series Global ex U.S. Index Fund | AACommonStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 99.20%
Fidelity Series Global ex U.S. Index Fund | AAPreferredStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.40%
Fidelity Series Global ex U.S. Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.40%
Fidelity International Sustainability Index Fund | TH0Member  
Holdings [Line Items]  
Percent of Net Asset Value 4.80%
Fidelity International Sustainability Index Fund | TH1Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.70%
Fidelity International Sustainability Index Fund | TH2Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.80%
Fidelity International Sustainability Index Fund | TH3Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.70%
Fidelity International Sustainability Index Fund | TH4Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.50%
Fidelity International Sustainability Index Fund | TH5Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.50%
Fidelity International Sustainability Index Fund | TH6Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.50%
Fidelity International Sustainability Index Fund | TH7Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.40%
Fidelity International Sustainability Index Fund | TH8Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.10%
Fidelity International Sustainability Index Fund | TH9Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.10%
Fidelity International Sustainability Index Fund | MSFinancialsSectorMember  
Holdings [Line Items]  
Percent of Net Asset Value 24.60%
Fidelity International Sustainability Index Fund | Information Technology Member  
Holdings [Line Items]  
Percent of Net Asset Value 12.20%
Fidelity International Sustainability Index Fund | Healthcare Sector  
Holdings [Line Items]  
Percent of Net Asset Value 8.20%
Fidelity International Sustainability Index Fund | Real Estate Sector  
Holdings [Line Items]  
Percent of Net Asset Value 1.80%
Fidelity International Sustainability Index Fund | Industrial Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 12.40%
Fidelity International Sustainability Index Fund | Materials Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 5.30%
Fidelity International Sustainability Index Fund | Consumer Discretionary Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 11.00%
Fidelity International Sustainability Index Fund | Consumer Staples Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 7.00%
Fidelity International Sustainability Index Fund | Communications Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 8.30%
Fidelity International Sustainability Index Fund | Energy Sector  
Holdings [Line Items]  
Percent of Net Asset Value 3.80%
Fidelity International Sustainability Index Fund | Utilities Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.90%
Fidelity International Sustainability Index Fund | Japan  
Holdings [Line Items]  
Percent of Net Asset Value 14.60%
Fidelity International Sustainability Index Fund | China  
Holdings [Line Items]  
Percent of Net Asset Value 9.90%
Fidelity International Sustainability Index Fund | Canada  
Holdings [Line Items]  
Percent of Net Asset Value 7.80%
Fidelity International Sustainability Index Fund | United Kingdom  
Holdings [Line Items]  
Percent of Net Asset Value 8.40%
Fidelity International Sustainability Index Fund | United States  
Holdings [Line Items]  
Percent of Net Asset Value 6.90%
Fidelity International Sustainability Index Fund | France  
Holdings [Line Items]  
Percent of Net Asset Value 5.80%
Fidelity International Sustainability Index Fund | India  
Holdings [Line Items]  
Percent of Net Asset Value 5.10%
Fidelity International Sustainability Index Fund | Taiwan  
Holdings [Line Items]  
Percent of Net Asset Value 7.00%
Fidelity International Sustainability Index Fund | OtherMember  
Holdings [Line Items]  
Percent of Net Asset Value 30.80%
Fidelity International Sustainability Index Fund | Switzerland  
Holdings [Line Items]  
Percent of Net Asset Value 3.70%
Fidelity International Sustainability Index Fund | AACommonStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 97.30%
Fidelity International Sustainability Index Fund | AAPreferredStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.20%
Fidelity International Sustainability Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember  
Holdings [Line Items]  
Percent of Net Asset Value 2.50%
Fidelity Emerging Markets Index Fund | TH0Member  
Holdings [Line Items]  
Percent of Net Asset Value 8.80%
Fidelity Emerging Markets Index Fund | TH1Member  
Holdings [Line Items]  
Percent of Net Asset Value 5.00%
Fidelity Emerging Markets Index Fund | TH2Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.10%
Fidelity Emerging Markets Index Fund | TH3Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.30%
Fidelity Emerging Markets Index Fund | TH4Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.70%
Fidelity Emerging Markets Index Fund | TH5Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.40%
Fidelity Emerging Markets Index Fund | TH6Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.30%
Fidelity Emerging Markets Index Fund | TH7Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.20%
Fidelity Emerging Markets Index Fund | TH8Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.10%
Fidelity Emerging Markets Index Fund | TH9Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.10%
Fidelity Emerging Markets Index Fund | MSFinancialsSectorMember  
Holdings [Line Items]  
Percent of Net Asset Value 25.20%
Fidelity Emerging Markets Index Fund | Information Technology Member  
Holdings [Line Items]  
Percent of Net Asset Value 21.50%
Fidelity Emerging Markets Index Fund | Healthcare Sector  
Holdings [Line Items]  
Percent of Net Asset Value 3.30%
Fidelity Emerging Markets Index Fund | Real Estate Sector  
Holdings [Line Items]  
Percent of Net Asset Value 1.30%
Fidelity Emerging Markets Index Fund | Industrial Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 6.50%
Fidelity Emerging Markets Index Fund | Materials Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 5.80%
Fidelity Emerging Markets Index Fund | Consumer Discretionary Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 13.60%
Fidelity Emerging Markets Index Fund | Consumer Staples Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 5.10%
Fidelity Emerging Markets Index Fund | Communications Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 9.90%
Fidelity Emerging Markets Index Fund | Energy Sector  
Holdings [Line Items]  
Percent of Net Asset Value 4.20%
Fidelity Emerging Markets Index Fund | Utilities Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.50%
Fidelity Emerging Markets Index Fund | China  
Holdings [Line Items]  
Percent of Net Asset Value 29.10%
Fidelity Emerging Markets Index Fund | India  
Holdings [Line Items]  
Percent of Net Asset Value 19.00%
Fidelity Emerging Markets Index Fund | Taiwan  
Holdings [Line Items]  
Percent of Net Asset Value 16.80%
Fidelity Emerging Markets Index Fund | OtherMember  
Holdings [Line Items]  
Percent of Net Asset Value 11.20%
Fidelity Emerging Markets Index Fund | Korea, Republic of  
Holdings [Line Items]  
Percent of Net Asset Value 9.20%
Fidelity Emerging Markets Index Fund | Brazil  
Holdings [Line Items]  
Percent of Net Asset Value 4.40%
Fidelity Emerging Markets Index Fund | Saudi Arabia  
Holdings [Line Items]  
Percent of Net Asset Value 3.90%
Fidelity Emerging Markets Index Fund | South Africa  
Holdings [Line Items]  
Percent of Net Asset Value 2.80%
Fidelity Emerging Markets Index Fund | Mexico  
Holdings [Line Items]  
Percent of Net Asset Value 2.20%
Fidelity Emerging Markets Index Fund | United Arab Emirates  
Holdings [Line Items]  
Percent of Net Asset Value 1.40%
Fidelity Emerging Markets Index Fund | AACommonStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 98.40%
Fidelity Emerging Markets Index Fund | AAPreferredStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.50%
Fidelity Emerging Markets Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember  
Holdings [Line Items]  
Percent of Net Asset Value 1.10%
Fidelity U.S. Sustainability Index Fund | TH0Member  
Holdings [Line Items]  
Percent of Net Asset Value 10.20%
Fidelity U.S. Sustainability Index Fund | TH1Member  
Holdings [Line Items]  
Percent of Net Asset Value 9.90%
Fidelity U.S. Sustainability Index Fund | TH2Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.40%
Fidelity U.S. Sustainability Index Fund | TH3Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.20%
Fidelity U.S. Sustainability Index Fund | TH4Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.10%
Fidelity U.S. Sustainability Index Fund | TH5Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.80%
Fidelity U.S. Sustainability Index Fund | TH6Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.20%
Fidelity U.S. Sustainability Index Fund | TH7Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.70%
Fidelity U.S. Sustainability Index Fund | TH8Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.40%
Fidelity U.S. Sustainability Index Fund | TH9Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.40%
Fidelity U.S. Sustainability Index Fund | MSFinancialsSectorMember  
Holdings [Line Items]  
Percent of Net Asset Value 12.90%
Fidelity U.S. Sustainability Index Fund | Information Technology Member  
Holdings [Line Items]  
Percent of Net Asset Value 30.00%
Fidelity U.S. Sustainability Index Fund | Healthcare Sector  
Holdings [Line Items]  
Percent of Net Asset Value 10.20%
Fidelity U.S. Sustainability Index Fund | Real Estate Sector  
Holdings [Line Items]  
Percent of Net Asset Value 2.20%
Fidelity U.S. Sustainability Index Fund | Industrial Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 7.80%
Fidelity U.S. Sustainability Index Fund | Materials Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.50%
Fidelity U.S. Sustainability Index Fund | Consumer Discretionary Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 10.20%
Fidelity U.S. Sustainability Index Fund | Consumer Staples Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 5.40%
Fidelity U.S. Sustainability Index Fund | Communications Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 8.80%
Fidelity U.S. Sustainability Index Fund | Energy Sector  
Holdings [Line Items]  
Percent of Net Asset Value 1.50%
Fidelity U.S. Sustainability Index Fund | Utilities Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.00%
Fidelity U.S. Sustainability Index Fund | United States  
Holdings [Line Items]  
Percent of Net Asset Value 98.70%
Fidelity U.S. Sustainability Index Fund | Brazil  
Holdings [Line Items]  
Percent of Net Asset Value 0.40%
Fidelity U.S. Sustainability Index Fund | Ireland  
Holdings [Line Items]  
Percent of Net Asset Value 0.70%
Fidelity U.S. Sustainability Index Fund | Netherlands  
Holdings [Line Items]  
Percent of Net Asset Value 0.20%
Fidelity U.S. Sustainability Index Fund | BailiwickOfJerseyMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.00%
Fidelity U.S. Sustainability Index Fund | AACommonStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 92.50%
Fidelity U.S. Sustainability Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember  
Holdings [Line Items]  
Percent of Net Asset Value 7.50%
Fidelity SAI International Quality Index Fund | TH0Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.60%
Fidelity SAI International Quality Index Fund | TH1Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.20%
Fidelity SAI International Quality Index Fund | TH2Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.20%
Fidelity SAI International Quality Index Fund | TH3Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.20%
Fidelity SAI International Quality Index Fund | TH4Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.10%
Fidelity SAI International Quality Index Fund | TH5Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.00%
Fidelity SAI International Quality Index Fund | TH6Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.70%
Fidelity SAI International Quality Index Fund | TH7Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.70%
Fidelity SAI International Quality Index Fund | TH8Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.60%
Fidelity SAI International Quality Index Fund | TH9Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.60%
Fidelity SAI International Quality Index Fund | MSFinancialsSectorMember  
Holdings [Line Items]  
Percent of Net Asset Value 20.50%
Fidelity SAI International Quality Index Fund | Information Technology Member  
Holdings [Line Items]  
Percent of Net Asset Value 9.50%
Fidelity SAI International Quality Index Fund | Healthcare Sector  
Holdings [Line Items]  
Percent of Net Asset Value 16.30%
Fidelity SAI International Quality Index Fund | Real Estate Sector  
Holdings [Line Items]  
Percent of Net Asset Value 0.20%
Fidelity SAI International Quality Index Fund | Industrial Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 16.70%
Fidelity SAI International Quality Index Fund | Materials Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 4.20%
Fidelity SAI International Quality Index Fund | Consumer Discretionary Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 12.60%
Fidelity SAI International Quality Index Fund | Consumer Staples Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 13.20%
Fidelity SAI International Quality Index Fund | Communications Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 4.90%
Fidelity SAI International Quality Index Fund | Energy Sector  
Holdings [Line Items]  
Percent of Net Asset Value 0.40%
Fidelity SAI International Quality Index Fund | Utilities Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.50%
Fidelity SAI International Quality Index Fund | Japan  
Holdings [Line Items]  
Percent of Net Asset Value 20.60%
Fidelity SAI International Quality Index Fund | United Kingdom  
Holdings [Line Items]  
Percent of Net Asset Value 10.70%
Fidelity SAI International Quality Index Fund | United States  
Holdings [Line Items]  
Percent of Net Asset Value 14.30%
Fidelity SAI International Quality Index Fund | Germany  
Holdings [Line Items]  
Percent of Net Asset Value 6.10%
Fidelity SAI International Quality Index Fund | France  
Holdings [Line Items]  
Percent of Net Asset Value 8.30%
Fidelity SAI International Quality Index Fund | OtherMember  
Holdings [Line Items]  
Percent of Net Asset Value 12.10%
Fidelity SAI International Quality Index Fund | Switzerland  
Holdings [Line Items]  
Percent of Net Asset Value 12.30%
Fidelity SAI International Quality Index Fund | Netherlands  
Holdings [Line Items]  
Percent of Net Asset Value 7.10%
Fidelity SAI International Quality Index Fund | Australia  
Holdings [Line Items]  
Percent of Net Asset Value 4.80%
Fidelity SAI International Quality Index Fund | Denmark  
Holdings [Line Items]  
Percent of Net Asset Value 3.70%
Fidelity SAI International Quality Index Fund | AACommonStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 99.00%
Fidelity SAI International Quality Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember  
Holdings [Line Items]  
Percent of Net Asset Value 1.00%
Fidelity Flex International Index Fund | TH0Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.60%
Fidelity Flex International Index Fund | TH1Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.40%
Fidelity Flex International Index Fund | TH2Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.10%
Fidelity Flex International Index Fund | TH3Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.00%
Fidelity Flex International Index Fund | TH4Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.00%
Fidelity Flex International Index Fund | TH5Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.90%
Fidelity Flex International Index Fund | TH6Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.90%
Fidelity Flex International Index Fund | TH7Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.80%
Fidelity Flex International Index Fund | TH8Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.80%
Fidelity Flex International Index Fund | TH9Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.80%
Fidelity Flex International Index Fund | MSFinancialsSectorMember  
Holdings [Line Items]  
Percent of Net Asset Value 25.60%
Fidelity Flex International Index Fund | Information Technology Member  
Holdings [Line Items]  
Percent of Net Asset Value 12.10%
Fidelity Flex International Index Fund | Healthcare Sector  
Holdings [Line Items]  
Percent of Net Asset Value 8.30%
Fidelity Flex International Index Fund | Real Estate Sector  
Holdings [Line Items]  
Percent of Net Asset Value 1.50%
Fidelity Flex International Index Fund | Industrial Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 14.00%
Fidelity Flex International Index Fund | Materials Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 6.00%
Fidelity Flex International Index Fund | Consumer Discretionary Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 10.70%
Fidelity Flex International Index Fund | Consumer Staples Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 7.50%
Fidelity Flex International Index Fund | Communications Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 6.10%
Fidelity Flex International Index Fund | Energy Sector  
Holdings [Line Items]  
Percent of Net Asset Value 4.20%
Fidelity Flex International Index Fund | Utilities Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.90%
Fidelity Flex International Index Fund | Japan  
Holdings [Line Items]  
Percent of Net Asset Value 13.90%
Fidelity Flex International Index Fund | China  
Holdings [Line Items]  
Percent of Net Asset Value 8.70%
Fidelity Flex International Index Fund | Canada  
Holdings [Line Items]  
Percent of Net Asset Value 7.60%
Fidelity Flex International Index Fund | United Kingdom  
Holdings [Line Items]  
Percent of Net Asset Value 7.30%
Fidelity Flex International Index Fund | United States  
Holdings [Line Items]  
Percent of Net Asset Value 7.80%
Fidelity Flex International Index Fund | Germany  
Holdings [Line Items]  
Percent of Net Asset Value 6.60%
Fidelity Flex International Index Fund | France  
Holdings [Line Items]  
Percent of Net Asset Value 6.10%
Fidelity Flex International Index Fund | India  
Holdings [Line Items]  
Percent of Net Asset Value 5.40%
Fidelity Flex International Index Fund | Taiwan  
Holdings [Line Items]  
Percent of Net Asset Value 4.80%
Fidelity Flex International Index Fund | OtherMember  
Holdings [Line Items]  
Percent of Net Asset Value 31.80%
Fidelity Flex International Index Fund | AACommonStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 98.50%
Fidelity Flex International Index Fund | AAPreferredStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.40%
Fidelity Flex International Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember  
Holdings [Line Items]  
Percent of Net Asset Value 1.10%
Fidelity SAI International Low Volatility Index Fund | TH0Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.10%
Fidelity SAI International Low Volatility Index Fund | TH1Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.10%
Fidelity SAI International Low Volatility Index Fund | TH2Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.10%
Fidelity SAI International Low Volatility Index Fund | TH3Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.00%
Fidelity SAI International Low Volatility Index Fund | TH4Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.00%
Fidelity SAI International Low Volatility Index Fund | TH5Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.00%
Fidelity SAI International Low Volatility Index Fund | TH6Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.90%
Fidelity SAI International Low Volatility Index Fund | TH7Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.90%
Fidelity SAI International Low Volatility Index Fund | TH8Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.90%
Fidelity SAI International Low Volatility Index Fund | TH9Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.80%
Fidelity SAI International Low Volatility Index Fund | MSFinancialsSectorMember  
Holdings [Line Items]  
Percent of Net Asset Value 19.70%
Fidelity SAI International Low Volatility Index Fund | Information Technology Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.40%
Fidelity SAI International Low Volatility Index Fund | Healthcare Sector  
Holdings [Line Items]  
Percent of Net Asset Value 15.40%
Fidelity SAI International Low Volatility Index Fund | Real Estate Sector  
Holdings [Line Items]  
Percent of Net Asset Value 4.70%
Fidelity SAI International Low Volatility Index Fund | Industrial Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 12.80%
Fidelity SAI International Low Volatility Index Fund | Materials Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 5.50%
Fidelity SAI International Low Volatility Index Fund | Consumer Discretionary Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 6.40%
Fidelity SAI International Low Volatility Index Fund | Consumer Staples Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 12.30%
Fidelity SAI International Low Volatility Index Fund | Communications Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 9.80%
Fidelity SAI International Low Volatility Index Fund | Utilities Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 8.50%
Fidelity SAI International Low Volatility Index Fund | Japan  
Holdings [Line Items]  
Percent of Net Asset Value 29.60%
Fidelity SAI International Low Volatility Index Fund | United Kingdom  
Holdings [Line Items]  
Percent of Net Asset Value 12.80%
Fidelity SAI International Low Volatility Index Fund | United States  
Holdings [Line Items]  
Percent of Net Asset Value 12.20%
Fidelity SAI International Low Volatility Index Fund | Germany  
Holdings [Line Items]  
Percent of Net Asset Value 5.80%
Fidelity SAI International Low Volatility Index Fund | France  
Holdings [Line Items]  
Percent of Net Asset Value 4.10%
Fidelity SAI International Low Volatility Index Fund | OtherMember  
Holdings [Line Items]  
Percent of Net Asset Value 12.60%
Fidelity SAI International Low Volatility Index Fund | Switzerland  
Holdings [Line Items]  
Percent of Net Asset Value 9.60%
Fidelity SAI International Low Volatility Index Fund | Netherlands  
Holdings [Line Items]  
Percent of Net Asset Value 5.10%
Fidelity SAI International Low Volatility Index Fund | Denmark  
Holdings [Line Items]  
Percent of Net Asset Value 3.40%
Fidelity SAI International Low Volatility Index Fund | Hong Kong  
Holdings [Line Items]  
Percent of Net Asset Value 4.80%
Fidelity SAI International Low Volatility Index Fund | AACommonStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 98.50%
Fidelity SAI International Low Volatility Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember  
Holdings [Line Items]  
Percent of Net Asset Value 1.50%
Fidelity SAI Emerging Markets Index Fund | TH0Member  
Holdings [Line Items]  
Percent of Net Asset Value 8.50%
Fidelity SAI Emerging Markets Index Fund | TH1Member  
Holdings [Line Items]  
Percent of Net Asset Value 4.90%
Fidelity SAI Emerging Markets Index Fund | TH2Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.00%
Fidelity SAI Emerging Markets Index Fund | TH3Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.30%
Fidelity SAI Emerging Markets Index Fund | TH4Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.70%
Fidelity SAI Emerging Markets Index Fund | TH5Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.40%
Fidelity SAI Emerging Markets Index Fund | TH6Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.20%
Fidelity SAI Emerging Markets Index Fund | TH7Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.20%
Fidelity SAI Emerging Markets Index Fund | TH8Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.10%
Fidelity SAI Emerging Markets Index Fund | TH9Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.00%
Fidelity SAI Emerging Markets Index Fund | MSFinancialsSectorMember  
Holdings [Line Items]  
Percent of Net Asset Value 24.40%
Fidelity SAI Emerging Markets Index Fund | Information Technology Member  
Holdings [Line Items]  
Percent of Net Asset Value 20.80%
Fidelity SAI Emerging Markets Index Fund | Healthcare Sector  
Holdings [Line Items]  
Percent of Net Asset Value 3.20%
Fidelity SAI Emerging Markets Index Fund | Real Estate Sector  
Holdings [Line Items]  
Percent of Net Asset Value 1.30%
Fidelity SAI Emerging Markets Index Fund | Industrial Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 6.10%
Fidelity SAI Emerging Markets Index Fund | Materials Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 5.80%
Fidelity SAI Emerging Markets Index Fund | Consumer Discretionary Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 13.20%
Fidelity SAI Emerging Markets Index Fund | Consumer Staples Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 4.80%
Fidelity SAI Emerging Markets Index Fund | Communications Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 9.60%
Fidelity SAI Emerging Markets Index Fund | Energy Sector  
Holdings [Line Items]  
Percent of Net Asset Value 4.10%
Fidelity SAI Emerging Markets Index Fund | Utilities Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.50%
Fidelity SAI Emerging Markets Index Fund | China  
Holdings [Line Items]  
Percent of Net Asset Value 28.20%
Fidelity SAI Emerging Markets Index Fund | United States  
Holdings [Line Items]  
Percent of Net Asset Value 4.30%
Fidelity SAI Emerging Markets Index Fund | India  
Holdings [Line Items]  
Percent of Net Asset Value 18.40%
Fidelity SAI Emerging Markets Index Fund | Taiwan  
Holdings [Line Items]  
Percent of Net Asset Value 16.30%
Fidelity SAI Emerging Markets Index Fund | OtherMember  
Holdings [Line Items]  
Percent of Net Asset Value 11.00%
Fidelity SAI Emerging Markets Index Fund | Korea, Republic of  
Holdings [Line Items]  
Percent of Net Asset Value 8.90%
Fidelity SAI Emerging Markets Index Fund | Brazil  
Holdings [Line Items]  
Percent of Net Asset Value 4.30%
Fidelity SAI Emerging Markets Index Fund | Saudi Arabia  
Holdings [Line Items]  
Percent of Net Asset Value 3.80%
Fidelity SAI Emerging Markets Index Fund | South Africa  
Holdings [Line Items]  
Percent of Net Asset Value 2.70%
Fidelity SAI Emerging Markets Index Fund | Mexico  
Holdings [Line Items]  
Percent of Net Asset Value 2.10%
Fidelity SAI Emerging Markets Index Fund | AACommonStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 95.30%
Fidelity SAI Emerging Markets Index Fund | AAPreferredStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.50%
Fidelity SAI Emerging Markets Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember  
Holdings [Line Items]  
Percent of Net Asset Value 4.20%
Fidelity SAI Emerging Markets Low Volatility Index Fund | TH0Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.60%
Fidelity SAI Emerging Markets Low Volatility Index Fund | TH1Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.60%
Fidelity SAI Emerging Markets Low Volatility Index Fund | TH2Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.60%
Fidelity SAI Emerging Markets Low Volatility Index Fund | TH3Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.60%
Fidelity SAI Emerging Markets Low Volatility Index Fund | TH4Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.50%
Fidelity SAI Emerging Markets Low Volatility Index Fund | TH5Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.50%
Fidelity SAI Emerging Markets Low Volatility Index Fund | TH6Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.50%
Fidelity SAI Emerging Markets Low Volatility Index Fund | TH7Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.50%
Fidelity SAI Emerging Markets Low Volatility Index Fund | TH8Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.40%
Fidelity SAI Emerging Markets Low Volatility Index Fund | TH9Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.40%
Fidelity SAI Emerging Markets Low Volatility Index Fund | MSFinancialsSectorMember  
Holdings [Line Items]  
Percent of Net Asset Value 28.30%
Fidelity SAI Emerging Markets Low Volatility Index Fund | Information Technology Member  
Holdings [Line Items]  
Percent of Net Asset Value 16.50%
Fidelity SAI Emerging Markets Low Volatility Index Fund | Healthcare Sector  
Holdings [Line Items]  
Percent of Net Asset Value 4.80%
Fidelity SAI Emerging Markets Low Volatility Index Fund | Real Estate Sector  
Holdings [Line Items]  
Percent of Net Asset Value 0.40%
Fidelity SAI Emerging Markets Low Volatility Index Fund | Industrial Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.10%
Fidelity SAI Emerging Markets Low Volatility Index Fund | Materials Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.40%
Fidelity SAI Emerging Markets Low Volatility Index Fund | Consumer Discretionary Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 8.10%
Fidelity SAI Emerging Markets Low Volatility Index Fund | Consumer Staples Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 7.90%
Fidelity SAI Emerging Markets Low Volatility Index Fund | Communications Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 13.10%
Fidelity SAI Emerging Markets Low Volatility Index Fund | Energy Sector  
Holdings [Line Items]  
Percent of Net Asset Value 3.30%
Fidelity SAI Emerging Markets Low Volatility Index Fund | Utilities Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 7.20%
Fidelity SAI Emerging Markets Low Volatility Index Fund | China  
Holdings [Line Items]  
Percent of Net Asset Value 21.60%
Fidelity SAI Emerging Markets Low Volatility Index Fund | United States  
Holdings [Line Items]  
Percent of Net Asset Value 4.90%
Fidelity SAI Emerging Markets Low Volatility Index Fund | India  
Holdings [Line Items]  
Percent of Net Asset Value 18.50%
Fidelity SAI Emerging Markets Low Volatility Index Fund | Taiwan  
Holdings [Line Items]  
Percent of Net Asset Value 21.20%
Fidelity SAI Emerging Markets Low Volatility Index Fund | OtherMember  
Holdings [Line Items]  
Percent of Net Asset Value 9.70%
Fidelity SAI Emerging Markets Low Volatility Index Fund | Korea, Republic of  
Holdings [Line Items]  
Percent of Net Asset Value 5.70%
Fidelity SAI Emerging Markets Low Volatility Index Fund | Saudi Arabia  
Holdings [Line Items]  
Percent of Net Asset Value 7.50%
Fidelity SAI Emerging Markets Low Volatility Index Fund | United Arab Emirates  
Holdings [Line Items]  
Percent of Net Asset Value 4.00%
Fidelity SAI Emerging Markets Low Volatility Index Fund | Malaysia  
Holdings [Line Items]  
Percent of Net Asset Value 4.60%
Fidelity SAI Emerging Markets Low Volatility Index Fund | Kuwait  
Holdings [Line Items]  
Percent of Net Asset Value 2.30%
Fidelity SAI Emerging Markets Low Volatility Index Fund | AACommonStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 95.10%
Fidelity SAI Emerging Markets Low Volatility Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember  
Holdings [Line Items]  
Percent of Net Asset Value 4.90%
Fidelity SAI U.S. Low Volatility Index Fund | TH0Member  
Holdings [Line Items]  
Percent of Net Asset Value 7.40%
Fidelity SAI U.S. Low Volatility Index Fund | TH1Member  
Holdings [Line Items]  
Percent of Net Asset Value 4.00%
Fidelity SAI U.S. Low Volatility Index Fund | TH2Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.50%
Fidelity SAI U.S. Low Volatility Index Fund | TH3Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.20%
Fidelity SAI U.S. Low Volatility Index Fund | TH4Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.10%
Fidelity SAI U.S. Low Volatility Index Fund | TH5Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.80%
Fidelity SAI U.S. Low Volatility Index Fund | TH6Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.70%
Fidelity SAI U.S. Low Volatility Index Fund | TH7Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.50%
Fidelity SAI U.S. Low Volatility Index Fund | TH8Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.40%
Fidelity SAI U.S. Low Volatility Index Fund | TH9Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.30%
Fidelity SAI U.S. Low Volatility Index Fund | MSFinancialsSectorMember  
Holdings [Line Items]  
Percent of Net Asset Value 13.00%
Fidelity SAI U.S. Low Volatility Index Fund | Information Technology Member  
Holdings [Line Items]  
Percent of Net Asset Value 26.30%
Fidelity SAI U.S. Low Volatility Index Fund | Healthcare Sector  
Holdings [Line Items]  
Percent of Net Asset Value 12.10%
Fidelity SAI U.S. Low Volatility Index Fund | Real Estate Sector  
Holdings [Line Items]  
Percent of Net Asset Value 4.30%
Fidelity SAI U.S. Low Volatility Index Fund | Industrial Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 9.90%
Fidelity SAI U.S. Low Volatility Index Fund | Materials Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.90%
Fidelity SAI U.S. Low Volatility Index Fund | Consumer Discretionary Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 8.90%
Fidelity SAI U.S. Low Volatility Index Fund | Consumer Staples Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 7.90%
Fidelity SAI U.S. Low Volatility Index Fund | Communications Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 7.40%
Fidelity SAI U.S. Low Volatility Index Fund | Energy Sector  
Holdings [Line Items]  
Percent of Net Asset Value 1.30%
Fidelity SAI U.S. Low Volatility Index Fund | Utilities Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 4.80%
Fidelity SAI U.S. Low Volatility Index Fund | United States  
Holdings [Line Items]  
Percent of Net Asset Value 99.30%
Fidelity SAI U.S. Low Volatility Index Fund | Ireland  
Holdings [Line Items]  
Percent of Net Asset Value 0.60%
Fidelity SAI U.S. Low Volatility Index Fund | Puerto Rico  
Holdings [Line Items]  
Percent of Net Asset Value 0.10%
Fidelity SAI U.S. Low Volatility Index Fund | AACommonStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 99.80%
Fidelity SAI U.S. Low Volatility Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.20%
Fidelity Total International Index Fund | TH0Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.20%
Fidelity Total International Index Fund | TH1Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.20%
Fidelity Total International Index Fund | TH2Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.00%
Fidelity Total International Index Fund | TH3Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.90%
Fidelity Total International Index Fund | TH4Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.90%
Fidelity Total International Index Fund | TH5Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.80%
Fidelity Total International Index Fund | TH6Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.80%
Fidelity Total International Index Fund | TH7Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.70%
Fidelity Total International Index Fund | TH8Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.70%
Fidelity Total International Index Fund | TH9Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.70%
Fidelity Total International Index Fund | MSFinancialsSectorMember  
Holdings [Line Items]  
Percent of Net Asset Value 23.60%
Fidelity Total International Index Fund | Information Technology Member  
Holdings [Line Items]  
Percent of Net Asset Value 11.60%
Fidelity Total International Index Fund | Healthcare Sector  
Holdings [Line Items]  
Percent of Net Asset Value 7.80%
Fidelity Total International Index Fund | Real Estate Sector  
Holdings [Line Items]  
Percent of Net Asset Value 2.60%
Fidelity Total International Index Fund | Industrial Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 14.60%
Fidelity Total International Index Fund | Materials Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 6.70%
Fidelity Total International Index Fund | Consumer Discretionary Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 10.10%
Fidelity Total International Index Fund | Consumer Staples Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 7.10%
Fidelity Total International Index Fund | Communications Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 5.50%
Fidelity Total International Index Fund | Energy Sector  
Holdings [Line Items]  
Percent of Net Asset Value 4.10%
Fidelity Total International Index Fund | Utilities Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.00%
Fidelity Total International Index Fund | Japan  
Holdings [Line Items]  
Percent of Net Asset Value 14.90%
Fidelity Total International Index Fund | China  
Holdings [Line Items]  
Percent of Net Asset Value 7.70%
Fidelity Total International Index Fund | Canada  
Holdings [Line Items]  
Percent of Net Asset Value 7.20%
Fidelity Total International Index Fund | United Kingdom  
Holdings [Line Items]  
Percent of Net Asset Value 7.30%
Fidelity Total International Index Fund | United States  
Holdings [Line Items]  
Percent of Net Asset Value 9.00%
Fidelity Total International Index Fund | Germany  
Holdings [Line Items]  
Percent of Net Asset Value 5.80%
Fidelity Total International Index Fund | France  
Holdings [Line Items]  
Percent of Net Asset Value 5.40%
Fidelity Total International Index Fund | India  
Holdings [Line Items]  
Percent of Net Asset Value 5.60%
Fidelity Total International Index Fund | Taiwan  
Holdings [Line Items]  
Percent of Net Asset Value 4.70%
Fidelity Total International Index Fund | OtherMember  
Holdings [Line Items]  
Percent of Net Asset Value 32.40%
Fidelity Total International Index Fund | AACommonStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 96.40%
Fidelity Total International Index Fund | AAPreferredStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.30%
Fidelity Total International Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember  
Holdings [Line Items]  
Percent of Net Asset Value 3.30%
Fidelity SAI International Momentum Index Fund | TH0Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.60%
Fidelity SAI International Momentum Index Fund | TH1Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.70%
Fidelity SAI International Momentum Index Fund | TH2Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.50%
Fidelity SAI International Momentum Index Fund | TH3Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.40%
Fidelity SAI International Momentum Index Fund | TH4Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.40%
Fidelity SAI International Momentum Index Fund | TH5Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.40%
Fidelity SAI International Momentum Index Fund | TH6Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.30%
Fidelity SAI International Momentum Index Fund | TH7Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.20%
Fidelity SAI International Momentum Index Fund | TH8Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.10%
Fidelity SAI International Momentum Index Fund | TH9Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.10%
Fidelity SAI International Momentum Index Fund | MSFinancialsSectorMember  
Holdings [Line Items]  
Percent of Net Asset Value 25.00%
Fidelity SAI International Momentum Index Fund | Information Technology Member  
Holdings [Line Items]  
Percent of Net Asset Value 8.10%
Fidelity SAI International Momentum Index Fund | Healthcare Sector  
Holdings [Line Items]  
Percent of Net Asset Value 9.60%
Fidelity SAI International Momentum Index Fund | Real Estate Sector  
Holdings [Line Items]  
Percent of Net Asset Value 1.60%
Fidelity SAI International Momentum Index Fund | Industrial Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 20.90%
Fidelity SAI International Momentum Index Fund | Materials Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 6.10%
Fidelity SAI International Momentum Index Fund | Consumer Discretionary Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 12.80%
Fidelity SAI International Momentum Index Fund | Consumer Staples Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 6.00%
Fidelity SAI International Momentum Index Fund | Communications Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 4.80%
Fidelity SAI International Momentum Index Fund | Energy Sector  
Holdings [Line Items]  
Percent of Net Asset Value 1.50%
Fidelity SAI International Momentum Index Fund | Utilities Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.70%
Fidelity SAI International Momentum Index Fund | Japan  
Holdings [Line Items]  
Percent of Net Asset Value 25.90%
Fidelity SAI International Momentum Index Fund | United Kingdom  
Holdings [Line Items]  
Percent of Net Asset Value 14.70%
Fidelity SAI International Momentum Index Fund | United States  
Holdings [Line Items]  
Percent of Net Asset Value 4.50%
Fidelity SAI International Momentum Index Fund | Germany  
Holdings [Line Items]  
Percent of Net Asset Value 14.40%
Fidelity SAI International Momentum Index Fund | France  
Holdings [Line Items]  
Percent of Net Asset Value 8.30%
Fidelity SAI International Momentum Index Fund | OtherMember  
Holdings [Line Items]  
Percent of Net Asset Value 12.20%
Fidelity SAI International Momentum Index Fund | Switzerland  
Holdings [Line Items]  
Percent of Net Asset Value 5.40%
Fidelity SAI International Momentum Index Fund | Australia  
Holdings [Line Items]  
Percent of Net Asset Value 5.50%
Fidelity SAI International Momentum Index Fund | Italy  
Holdings [Line Items]  
Percent of Net Asset Value 5.20%
Fidelity SAI International Momentum Index Fund | Spain  
Holdings [Line Items]  
Percent of Net Asset Value 3.90%
Fidelity SAI International Momentum Index Fund | AACommonStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 99.10%
Fidelity SAI International Momentum Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.90%
Fidelity SAI Emerging Markets Value Index Fund | TH0Member  
Holdings [Line Items]  
Percent of Net Asset Value 7.90%
Fidelity SAI Emerging Markets Value Index Fund | TH1Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.80%
Fidelity SAI Emerging Markets Value Index Fund | TH2Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.20%
Fidelity SAI Emerging Markets Value Index Fund | TH3Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.10%
Fidelity SAI Emerging Markets Value Index Fund | TH4Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.90%
Fidelity SAI Emerging Markets Value Index Fund | TH5Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.80%
Fidelity SAI Emerging Markets Value Index Fund | TH6Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.60%
Fidelity SAI Emerging Markets Value Index Fund | TH7Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.60%
Fidelity SAI Emerging Markets Value Index Fund | TH8Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.50%
Fidelity SAI Emerging Markets Value Index Fund | TH9Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.40%
Fidelity SAI Emerging Markets Value Index Fund | MSFinancialsSectorMember  
Holdings [Line Items]  
Percent of Net Asset Value 23.80%
Fidelity SAI Emerging Markets Value Index Fund | Information Technology Member  
Holdings [Line Items]  
Percent of Net Asset Value 21.30%
Fidelity SAI Emerging Markets Value Index Fund | Healthcare Sector  
Holdings [Line Items]  
Percent of Net Asset Value 3.60%
Fidelity SAI Emerging Markets Value Index Fund | Real Estate Sector  
Holdings [Line Items]  
Percent of Net Asset Value 1.60%
Fidelity SAI Emerging Markets Value Index Fund | Industrial Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 6.60%
Fidelity SAI Emerging Markets Value Index Fund | Materials Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 5.40%
Fidelity SAI Emerging Markets Value Index Fund | Consumer Discretionary Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 13.20%
Fidelity SAI Emerging Markets Value Index Fund | Consumer Staples Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 4.70%
Fidelity SAI Emerging Markets Value Index Fund | Communications Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 9.90%
Fidelity SAI Emerging Markets Value Index Fund | Energy Sector  
Holdings [Line Items]  
Percent of Net Asset Value 4.50%
Fidelity SAI Emerging Markets Value Index Fund | Utilities Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.00%
Fidelity SAI Emerging Markets Value Index Fund | China  
Holdings [Line Items]  
Percent of Net Asset Value 28.10%
Fidelity SAI Emerging Markets Value Index Fund | United States  
Holdings [Line Items]  
Percent of Net Asset Value 2.70%
Fidelity SAI Emerging Markets Value Index Fund | India  
Holdings [Line Items]  
Percent of Net Asset Value 15.90%
Fidelity SAI Emerging Markets Value Index Fund | Taiwan  
Holdings [Line Items]  
Percent of Net Asset Value 17.70%
Fidelity SAI Emerging Markets Value Index Fund | OtherMember  
Holdings [Line Items]  
Percent of Net Asset Value 13.00%
Fidelity SAI Emerging Markets Value Index Fund | Korea, Republic of  
Holdings [Line Items]  
Percent of Net Asset Value 10.10%
Fidelity SAI Emerging Markets Value Index Fund | Brazil  
Holdings [Line Items]  
Percent of Net Asset Value 3.90%
Fidelity SAI Emerging Markets Value Index Fund | Saudi Arabia  
Holdings [Line Items]  
Percent of Net Asset Value 3.80%
Fidelity SAI Emerging Markets Value Index Fund | South Africa  
Holdings [Line Items]  
Percent of Net Asset Value 2.80%
Fidelity SAI Emerging Markets Value Index Fund | Mexico  
Holdings [Line Items]  
Percent of Net Asset Value 2.00%
Fidelity SAI Emerging Markets Value Index Fund | AACommonStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 97.50%
Fidelity SAI Emerging Markets Value Index Fund | AAPreferredStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.10%
Fidelity SAI Emerging Markets Value Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember  
Holdings [Line Items]  
Percent of Net Asset Value 2.40%
Fidelity Global ex U.S. Index Fund | TH0Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.60%
Fidelity Global ex U.S. Index Fund | TH1Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.40%
Fidelity Global ex U.S. Index Fund | TH2Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.10%
Fidelity Global ex U.S. Index Fund | TH3Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.00%
Fidelity Global ex U.S. Index Fund | TH4Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.00%
Fidelity Global ex U.S. Index Fund | TH5Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.00%
Fidelity Global ex U.S. Index Fund | TH6Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.90%
Fidelity Global ex U.S. Index Fund | TH7Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.80%
Fidelity Global ex U.S. Index Fund | TH8Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.80%
Fidelity Global ex U.S. Index Fund | TH9Member  
Holdings [Line Items]  
Percent of Net Asset Value 0.80%
Fidelity Global ex U.S. Index Fund | MSFinancialsSectorMember  
Holdings [Line Items]  
Percent of Net Asset Value 25.50%
Fidelity Global ex U.S. Index Fund | Information Technology Member  
Holdings [Line Items]  
Percent of Net Asset Value 12.30%
Fidelity Global ex U.S. Index Fund | Healthcare Sector  
Holdings [Line Items]  
Percent of Net Asset Value 8.40%
Fidelity Global ex U.S. Index Fund | Real Estate Sector  
Holdings [Line Items]  
Percent of Net Asset Value 1.50%
Fidelity Global ex U.S. Index Fund | Industrial Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 13.70%
Fidelity Global ex U.S. Index Fund | Materials Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 6.10%
Fidelity Global ex U.S. Index Fund | Consumer Discretionary Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 10.50%
Fidelity Global ex U.S. Index Fund | Consumer Staples Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 7.40%
Fidelity Global ex U.S. Index Fund | Communications Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 6.00%
Fidelity Global ex U.S. Index Fund | Energy Sector  
Holdings [Line Items]  
Percent of Net Asset Value 4.30%
Fidelity Global ex U.S. Index Fund | Utilities Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.80%
Fidelity Global ex U.S. Index Fund | Japan  
Holdings [Line Items]  
Percent of Net Asset Value 13.70%
Fidelity Global ex U.S. Index Fund | China  
Holdings [Line Items]  
Percent of Net Asset Value 8.60%
Fidelity Global ex U.S. Index Fund | Canada  
Holdings [Line Items]  
Percent of Net Asset Value 7.60%
Fidelity Global ex U.S. Index Fund | United Kingdom  
Holdings [Line Items]  
Percent of Net Asset Value 7.30%
Fidelity Global ex U.S. Index Fund | United States  
Holdings [Line Items]  
Percent of Net Asset Value 8.20%
Fidelity Global ex U.S. Index Fund | Germany  
Holdings [Line Items]  
Percent of Net Asset Value 6.50%
Fidelity Global ex U.S. Index Fund | France  
Holdings [Line Items]  
Percent of Net Asset Value 6.10%
Fidelity Global ex U.S. Index Fund | India  
Holdings [Line Items]  
Percent of Net Asset Value 5.40%
Fidelity Global ex U.S. Index Fund | Taiwan  
Holdings [Line Items]  
Percent of Net Asset Value 4.80%
Fidelity Global ex U.S. Index Fund | OtherMember  
Holdings [Line Items]  
Percent of Net Asset Value 31.80%
Fidelity Global ex U.S. Index Fund | AACommonStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 98.10%
Fidelity Global ex U.S. Index Fund | AAPreferredStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.40%
Fidelity Global ex U.S. Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember  
Holdings [Line Items]  
Percent of Net Asset Value 1.50%
Fidelity SAI International Value Index Fund | TH0Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.60%
Fidelity SAI International Value Index Fund | TH1Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.50%
Fidelity SAI International Value Index Fund | TH2Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.40%
Fidelity SAI International Value Index Fund | TH3Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.30%
Fidelity SAI International Value Index Fund | TH4Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.20%
Fidelity SAI International Value Index Fund | TH5Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.10%
Fidelity SAI International Value Index Fund | TH6Member  
Holdings [Line Items]  
Percent of Net Asset Value 2.10%
Fidelity SAI International Value Index Fund | TH7Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.90%
Fidelity SAI International Value Index Fund | TH8Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.90%
Fidelity SAI International Value Index Fund | TH9Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.70%
Fidelity SAI International Value Index Fund | MSFinancialsSectorMember  
Holdings [Line Items]  
Percent of Net Asset Value 25.10%
Fidelity SAI International Value Index Fund | Information Technology Member  
Holdings [Line Items]  
Percent of Net Asset Value 5.60%
Fidelity SAI International Value Index Fund | Healthcare Sector  
Holdings [Line Items]  
Percent of Net Asset Value 9.60%
Fidelity SAI International Value Index Fund | Real Estate Sector  
Holdings [Line Items]  
Percent of Net Asset Value 0.80%
Fidelity SAI International Value Index Fund | Industrial Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 17.30%
Fidelity SAI International Value Index Fund | Materials Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 7.20%
Fidelity SAI International Value Index Fund | Consumer Discretionary Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 10.80%
Fidelity SAI International Value Index Fund | Consumer Staples Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 7.20%
Fidelity SAI International Value Index Fund | Communications Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 6.20%
Fidelity SAI International Value Index Fund | Energy Sector  
Holdings [Line Items]  
Percent of Net Asset Value 4.80%
Fidelity SAI International Value Index Fund | Utilities Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 4.00%
Fidelity SAI International Value Index Fund | Japan  
Holdings [Line Items]  
Percent of Net Asset Value 25.80%
Fidelity SAI International Value Index Fund | United Kingdom  
Holdings [Line Items]  
Percent of Net Asset Value 11.80%
Fidelity SAI International Value Index Fund | United States  
Holdings [Line Items]  
Percent of Net Asset Value 9.60%
Fidelity SAI International Value Index Fund | Germany  
Holdings [Line Items]  
Percent of Net Asset Value 11.30%
Fidelity SAI International Value Index Fund | France  
Holdings [Line Items]  
Percent of Net Asset Value 13.30%
Fidelity SAI International Value Index Fund | OtherMember  
Holdings [Line Items]  
Percent of Net Asset Value 12.00%
Fidelity SAI International Value Index Fund | Australia  
Holdings [Line Items]  
Percent of Net Asset Value 4.10%
Fidelity SAI International Value Index Fund | Spain  
Holdings [Line Items]  
Percent of Net Asset Value 5.20%
Fidelity SAI International Value Index Fund | Singapore  
Holdings [Line Items]  
Percent of Net Asset Value 4.20%
Fidelity SAI International Value Index Fund | Sweden  
Holdings [Line Items]  
Percent of Net Asset Value 2.70%
Fidelity SAI International Value Index Fund | AACommonStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 98.60%
Fidelity SAI International Value Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember  
Holdings [Line Items]  
Percent of Net Asset Value 1.40%
Fidelity SAI International Index Fund | TH0Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.80%
Fidelity SAI International Index Fund | TH1Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.60%
Fidelity SAI International Index Fund | TH2Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.50%
Fidelity SAI International Index Fund | TH3Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.30%
Fidelity SAI International Index Fund | TH4Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.20%
Fidelity SAI International Index Fund | TH5Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.20%
Fidelity SAI International Index Fund | TH6Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.20%
Fidelity SAI International Index Fund | TH7Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.20%
Fidelity SAI International Index Fund | TH8Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.10%
Fidelity SAI International Index Fund | TH9Member  
Holdings [Line Items]  
Percent of Net Asset Value 1.00%
Fidelity SAI International Index Fund | MSFinancialsSectorMember  
Holdings [Line Items]  
Percent of Net Asset Value 23.30%
Fidelity SAI International Index Fund | Information Technology Member  
Holdings [Line Items]  
Percent of Net Asset Value 8.10%
Fidelity SAI International Index Fund | Healthcare Sector  
Holdings [Line Items]  
Percent of Net Asset Value 11.60%
Fidelity SAI International Index Fund | Real Estate Sector  
Holdings [Line Items]  
Percent of Net Asset Value 1.80%
Fidelity SAI International Index Fund | Industrial Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 18.00%
Fidelity SAI International Index Fund | Materials Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 5.50%
Fidelity SAI International Index Fund | Consumer Discretionary Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 10.10%
Fidelity SAI International Index Fund | Consumer Staples Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 8.50%
Fidelity SAI International Index Fund | Communications Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 5.10%
Fidelity SAI International Index Fund | Energy Sector  
Holdings [Line Items]  
Percent of Net Asset Value 3.00%
Fidelity SAI International Index Fund | Utilities Sector Member  
Holdings [Line Items]  
Percent of Net Asset Value 3.20%
Fidelity SAI International Index Fund | Japan  
Holdings [Line Items]  
Percent of Net Asset Value 21.60%
Fidelity SAI International Index Fund | United Kingdom  
Holdings [Line Items]  
Percent of Net Asset Value 11.40%
Fidelity SAI International Index Fund | United States  
Holdings [Line Items]  
Percent of Net Asset Value 12.20%
Fidelity SAI International Index Fund | Germany  
Holdings [Line Items]  
Percent of Net Asset Value 10.10%
Fidelity SAI International Index Fund | France  
Holdings [Line Items]  
Percent of Net Asset Value 9.60%
Fidelity SAI International Index Fund | OtherMember  
Holdings [Line Items]  
Percent of Net Asset Value 16.70%
Fidelity SAI International Index Fund | Switzerland  
Holdings [Line Items]  
Percent of Net Asset Value 4.80%
Fidelity SAI International Index Fund | Netherlands  
Holdings [Line Items]  
Percent of Net Asset Value 3.90%
Fidelity SAI International Index Fund | Australia  
Holdings [Line Items]  
Percent of Net Asset Value 6.60%
Fidelity SAI International Index Fund | Sweden  
Holdings [Line Items]  
Percent of Net Asset Value 3.10%
Fidelity SAI International Index Fund | AACommonStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 97.90%
Fidelity SAI International Index Fund | AAPreferredStocksMember  
Holdings [Line Items]  
Percent of Net Asset Value 0.30%
Fidelity SAI International Index Fund | AAShortTermInvestmentsandNetOtherAssetsLiabilitiesMember  
Holdings [Line Items]  
Percent of Net Asset Value 1.80%