| Document And Entity Information | Jul. 29, 2019 |
| Document Information [Line Items] | |
| Entity Registrant Name | Proto Labs Inc |
| Document Type | 8-K |
| Document Period End Date | Jul. 29, 2019 |
| Entity Incorporation, State or Country Code | MN |
| Entity File Number | 001-35435 |
| 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 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Entity Ex Transition Period | false |
| Title of 12(b) Security | Common Stock |
| Trading Symbol | PRLB |
| Security Exchange Name | NYSE |
| Amendment Flag | false |
| Entity Central Index Key | 0001443669 |
