Document and Entity Information - shares
6 Months Ended
Dec. 31, 2016
Jan. 31, 2017
Document And Entity Information [Abstract]    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Dec. 31, 2016  
Document Fiscal Year Focus 2017  
Document Fiscal Period Focus Q2  
Trading Symbol QNST  
Entity Registrant Name QUINSTREET, INC  
Entity Central Index Key 0001117297  
Current Fiscal Year End Date --06-30  
Entity Filer Category Accelerated Filer  
Entity Common Stock, Shares Outstanding   45,419,451