Document And Entity Information - shares	6 Months Ended
	Jun. 30, 2019	Jul. 25, 2019
Document Information [Line Items]
Entity Central Index Key	0001443669
Entity Shell Company	false
Entity Registrant Name	Proto Labs Inc
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Document Fiscal Period Focus	Q2
Document Fiscal Year Focus	2019
Entity Small Business	false
Entity Emerging Growth Company	false
Document Quarterly Report	true
Document Transition Report	false
Document Type	10-Q
Document Period End Date	Jun. 30, 2019
Entity File Number	001-35435
Entity Incorporation, State or Country Code	MN
Entity Tax Identification Number	41-1939628
Entity Address, Address Line One	5540 Pioneer Creek Drive
Entity Address, City or Town	Maple Plain
Entity Address, State or Province	MN
Entity Address, Postal Zip Code	55359
City Area Code	763
Local Phone Number	479-3680
Title of 12(b) Security	Common Stock
Trading Symbol	PRLB
Security Exchange Name	NYSE
Entity Interactive Data Current	Yes
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		26,882,097