Document And Entity Information - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2015	Feb. 17, 2016	Jun. 30, 2015
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)		26,201,818
Entity Public Float			$ 1.6
Document Type	10-K
Document Period End Date	Dec. 31, 2015
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	FY
Amendment Flag	false