Document and Entity Information - shares
9 Months Ended
Jun. 30, 2018
Aug. 01, 2018
Document and Entity Information    
Entity Registrant Name LIQUIDITY SERVICES INC  
Entity Central Index Key 0001235468  
Document Type 10-Q  
Document Period End Date Jun. 30, 2018  
Amendment Flag false  
Current Fiscal Year End Date --09-30  
Entity Current Reporting Status Yes  
Entity Filer Category Accelerated Filer  
Entity Common Stock, Shares Outstanding (in shares)   32,123,193
Document Fiscal Year Focus 2018  
Document Fiscal Period Focus Q3