Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	FIDELITY SALEM STREET TRUST
Prospectus Date	rr_ProspectusDate	Mar. 31, 2018
01.31 Fidelity Series 1000 Value Index Fund Series PRO-07 | Fidelity® Series 1000 Value Index Fund
Risk/Return:	rr_RiskReturnAbstract
Strategy Narrative [Text Block]	rr_StrategyNarrativeTextBlock	Normally investing at least 80% of assets in securities of companies with large market capitalizations included in the Russell 1000® Value Index, which is a market capitalization-weighted index designed to measure the performance of the large-cap value segment of the U.S. equity market.