Significant Accounting Policies (Policies)	6 Months Ended
Significant Accounting Policies (Policies)	Jun. 30, 2017
Accounting Policies [Abstract]
Basis of Accounting, Policy [Policy Text Block]	The unaudited interim Consolidated Financial Statements of Proto Labs, Inc. (Proto Labs, 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, 2016 as filed with the Securities and Exchange Commission (SEC) on February 22, 2017. The accompanying Consolidated Balance Sheet as of December 31, 2016 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 22, 2017 as referenced above.
New Accounting Pronouncements, Policy [Policy Text Block]	Recently Adopted Accounting Pronouncements During the first quarter of 2017, the Company adopted the Financial Accounting Standards Board (FASB) Accounting Standards Update (ASU) 2016 - 09, Employee Share-Based Payment Accounting , which is intended to simplify several aspects of the accounting for employee share-based payment transactions, including the accounting for income taxes, forfeitures, statutory tax withholding requirements, and classification in the statement of cash flows. As a result of the adoption, the amount in excess tax benefits from stock-based compensation is recorded in our provision for income taxes. For the three and six months ended June 30, 2017, the amount recorded in the provision for income taxes was $0.1 million and $0.2 million, respectively. Historically, these amounts were recorded as additional paid-in capital as required by the accounting pronouncements in force during the periods presented. In addition, for each period presented, cash flows related to excess tax benefits are now classified as an operating activity along with other income tax cash flows. Retrospective application of the cash flow presentation requirements resulted in an increase to net cash provided by operations and a decrease to net cash provided by financing activities of $1.9 million for the six months ended June 30, 2016. Recently Issued Accounting Pronouncements In May 2014, the FASB issued ASU No. 2014 - 09, Revenue from Contracts with Customers . 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 is required to adopt the new pronouncement using one of two retrospective application methods. On July 9, 2015, the FASB voted to approve a deferral of the effective date of ASU 2014 - 09 by one year to December 15, 2017 for annual reporting periods beginning after that date. The Company expects to adopt the new revenue standard using the modified re trospective approach. As of June 30, 2017, the Company has identified revenue streams and continues to review individual contracts. Based on this review, the Company expects to recognize revenue over time for the majority of contracts. While the Company is still evaluating the impact of the amended guidance, it does not expect the impact to the timing or amount of revenue recognized to be material. The Company expects to quantify and disclose the expected impact, if any, of adopting this amended guidance in its Annual Report on Form 10 -K for the year ending December 31, 2017. 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 does not expect the impact to be material. In August 2016, the FASB issued ASU 2016 - 15, Statement of Cash Flows , which is intended to reduce diversity in how companies present and classify certain cash receipts and cash payments in the statement of cash flows. This guidance will be effective for annual reporting periods beginning after December 15, 2017 and interim periods within those fiscal years with early adoption permitted. The Company is evaluating the impact of the future adoption of this guidance on its consolidated financial statements, but 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. In January 2017, the FASB issued 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. This guidance will be effective for annual reporting periods beginning after December 15, 2017 and interim periods within those fiscal years with early adoption permitted. The Company is evaluating the impact of the future adoption of this guidance on its consolidated financial statements. In May 2017, the FASB issued 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. This guidance will be effective for annual reporting periods beginning after December 15, 2017 and interim periods within those fiscal years with early adoption permitted. The Company is evaluating the impact of the future adoption of this guidance on its consolidated financial statements.