Significant Accounting Policies (Policies)	3 Months Ended
Significant Accounting Policies (Policies)	Mar. 31, 2018
Accounting Policies [Abstract]
Basis of Accounting, Policy [Policy Text Block]	The unaudited interim Consolidated Financial Statements of Proto Labs, Inc. (Protolabs, the Company, we, us or our) have been prepared in accordance with accounting principles generally accepted in the United States of America (U.S. GAAP) for interim financial information and with the instructions to Form 10 -Q and Article 10 of Regulation S- X. In the opinion of management, the accompanying financial statements reflect all adjustments necessary for a fair presentation of the Company’s statements of financial position, results of operations and cash flows for the periods presented. Except as otherwise disclosed herein, these adjustments consist of normal, recurring items. Operating results for interim periods are not necessarily indicative of results that may be expected for the fiscal year as a whole. The preparation of the financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenues, expenses, and the related disclosures at the date of the financial statements and during the reporting period. Actual results could materially differ from these estimates. For further information, refer to the audited Consolidated Financial Statements and Notes thereto included in the Company’s Annual Report on Form 10 -K for the year ended December 31, 2017 as filed with the Securities and Exchange Commission (SEC) on February 23, 2018. The accompanying Consolidated Balance Sheet as of December 31, 2017 was derived from the audited Consolidated Financial Statements but does not include all disclosures required by U.S. GAAP for a full set of financial statements. This Form 10 -Q should be read in conjunction with the Company’s Consolidated Financial Statements and Notes included in the Annual Report on Form 10 -K filed on February 23, 2018 as referenced above.
New Accounting Pronouncements, Policy [Policy Text Block]	Recently Adopted Accounting Pronouncements During the first quarter of 2018, the Company adopted the Financial Accounting Standards Board (FASB) Accounting Standards Update (ASU) 2014 - 09, Revenue from Contracts with Customers (ASC 606 ). This ASU is a comprehensive new revenue recognition model that requires a company to recognize revenue from the transfer of goods or services to customers in an amount that reflects the consideration that the entity expects to receive in exchange for those goods or services. The Company has adopted the new revenue standard using the modified retrospective approach. The Company manufactures parts that have no alternative use to the Company since the parts are custom made to specific customer orders, and the Company believes there is a legally enforceable right to payment for performance completed to date on these manufactured parts. For those manufactured parts that meet these two criteria, the Company will recognize revenue over time. The transition adjustment recorded was an increase of $1.5 million to the Company’s retained earnings balance as of January 1, 2018. During the fourth quarter of 2017, the Company early adopted ASU 2017 - 01, Business Combinations, which is intended to clarify the definition of a business to assist with evaluating whether transactions should be accounted for as acquisitions or disposals of assets or businesses. The adoption of this guidance did not have a material impact on the Company’s consolidated financial statements. During the first quarter of 2018, the Company adopted ASU 2017 - 09, Compensation – Stock Compensation , which is intended to provide clarity and reduce diversity in practice as well as cost and complexity when applying the guidance to a change to the terms or conditions of a share-based payment award. The adoption of this guidance did not have a material impact on the Company’s consolidated financial statements. Recently Issued Accounting Pronouncements In February 2016, the FASB issued ASU 2016 - 02, Leases , which introduces the balance sheet recognition of lease assets and lease liabilities by lessees for those leases classified as operating leases under previous guidance. The guidance will be effective for annual reporting periods beginning after December 15, 2018 and interim periods within those fiscal years with early adoption permitted. The Company is evaluating the impact of the future adoption of this standard on its consolidated financial statements, but because the Company owns a majority of its buildings and significant assets, it does not expect the impact to be material. In January 2017, the FASB issued ASU 2017 - 04, Intangibles – Goodwill and Other, which is intended to simplify the subsequent measurement of goodwill. This guidance will be effective for impairment tests in fiscal years beginning after December 15, 2019 and interim periods within those fiscal years with early adoption permitted. The Company is evaluating the impact of future adoption of this guidance on its consolidated financial statements, but does not expect the impact to be material.