Document and Entity Information (USD $)
15 Months Ended
Sep. 30, 2011
Oct. 31, 2011
Dec. 31, 2010
Document and Entity Information [Abstract]      
Entity Registrant Name QUINSTREET, INC    
Entity Central Index Key 0001117297    
Document Type 10-Q    
Document Period End Date Sep. 30, 2011    
Amendment Flag false    
Document Fiscal Year Focus 2012    
Document Fiscal Period Focus Q1    
Current Fiscal Year End Date --06-30    
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Filer Category Accelerated Filer    
Entity Public Float     $ 404,319,901
Entity Common Stock, Shares Outstanding   47,641,625