Document and Entity Information - shares
3 Months Ended
Dec. 31, 2017
Jan. 29, 2018
Document and Entity Information    
Entity Registrant Name LIQUIDITY SERVICES INC  
Entity Central Index Key 0001235468  
Document Type 10-Q  
Document Period End Date Dec. 31, 2017  
Amendment Flag false  
Current Fiscal Year End Date --12-31  
Entity Current Reporting Status Yes  
Entity Filer Category Accelerated Filer  
Entity Common Stock, Shares Outstanding   31,935,263
Document Fiscal Year Focus 2018  
Document Fiscal Period Focus Q1