Document And Entity Information - shares
 9 Months Ended
Sep. 30, 2016
Oct. 25, 2016
Document Information [Line Items]    
Entity Registrant Name Proto Labs Inc  
Entity Central Index Key 0001443669  
Trading Symbol prlb  
Current Fiscal Year End Date --12-31  
Entity Filer Category Large Accelerated Filer  
Entity Current Reporting Status Yes  
Entity Voluntary Filers No  
Entity Well-known Seasoned Issuer Yes  
Entity Common Stock, Shares Outstanding (in shares)   26,432,035
Document Type 10-Q  
Document Period End Date Sep. 30, 2016  
Document Fiscal Year Focus 2016  
Document Fiscal Period Focus Q3  
Amendment Flag false