Document and Entity Information - shares
9 Months Ended
Sep. 30, 2018
Oct. 30, 2018
Document And Entity Information    
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Sep. 30, 2018  
Document Fiscal Year Focus 2018  
Document Fiscal Period Focus Q3  
Trading Symbol PCCC  
Entity Registrant Name PC CONNECTION INC  
Entity Central Index Key 0001050377  
Current Fiscal Year End Date --12-31  
Entity Current Reporting Status Yes  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Filer Category Accelerated Filer  
Entity Common Stock, Shares Outstanding   26,730,061