Document and Entity Information - shares
3 Months Ended
Dec. 31, 2018
Feb. 05, 2019
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, 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)   33,307,303
Document Fiscal Year Focus 2019  
Document Fiscal Period Focus Q1