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Label Element Value
Risk/Return: rr_RiskReturnAbstract  
Document Type dei_DocumentType Other
Document Period End Date dei_DocumentPeriodEndDate Jan. 31, 2011
Registrant Name dei_EntityRegistrantName Vanguard Fixed Income Securities Funds
Central Index Key dei_EntityCentralIndexKey 0000106444
Amendment Flag dei_AmendmentFlag false
Document Creation Date dei_DocumentCreationDate Nov. 30, 2011
Document Effective Date dei_DocumentEffectiveDate Nov. 22, 2011
Vanguard Long-Term Investment-Grade Fund | Participant
 
Risk/Return: rr_RiskReturnAbstract  
Prospectus Date rr_ProspectusDate May 26, 2011
Vanguard Long-Term Investment-Grade Fund | Participant:
 
Risk/Return: rr_RiskReturnAbstract  
Prospectus Date rr_ProspectusDate May 26, 2011
Vanguard Long-Term Investment-Grade Fund | Retail
 
Risk/Return: rr_RiskReturnAbstract  
Prospectus Date rr_ProspectusDate May 26, 2011