Summary of Significant Accounting Policies	3 Months Ended
Apr. 02, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies As permitted by the rules of the Securities and Exchange Commission applicable to Quarterly Reports on Form 10-Q, these notes are condensed and do not contain all disclosures required by generally accepted accounting principles (GAAP). Cognex Corporation (the "Company") has provided new disclosures related to inventories and internal-use software in this quarterly report on Form 10-Q. Reference should be made to the consolidated financial statements and related notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2016 for a full description of significant accounting policies. In the opinion of the management of the Company, the accompanying consolidated unaudited financial statements contain all adjustments, consisting of normal, recurring adjustments and financial statement reclassifications, including those related to the disposition of a business, necessary to present fairly the Company’s financial position as of April 2, 2017, and the results of its operations for the three-month periods ended April 2, 2017 and April 3, 2016, and changes in shareholders’ equity, comprehensive income, and cash flows for the periods presented. The results disclosed in the Consolidated Statements of Operations for the three-month period ended April 2, 2017 are not necessarily indicative of the results to be expected for the full year. Inventories On January 1, 2017, the Company adopted Accounting Standards Update (ASU) 2015-11 "Inventory - Simplifying the Measurement of Inventory." This Update requires companies to measure inventory at the lower of cost and net realizable value. Net realizable value is the estimated selling prices in the ordinary course of business, less reasonably predictable costs of completion, disposal, and transportation. This adoption did not have an impact on the Company's inventory value. Internal-use Software The Company accounts for the costs of computer software developed or obtained for internal use under Accounting Standards Codification 350-40 "Intangibles - Goodwill and Other, Internal-use Software." Internal-use software is software acquired, internally developed, or modified solely to meet the entity's internal needs, and during the software's development, no substantive plan exists to sell the software. The preliminary project stage includes determination of system requirements, vendor demonstrations, and final selection of vendors, and during this stage costs are expensed as incurred. The application development stage includes software design, coding, hardware installation, and testing. During this stage, certain costs are capitalized, including external direct costs of materials and services, as well as payroll and payroll-related costs for employees who are directly associated with the project, while certain costs are expensed as incurred, including training and data conversion costs. The post-implementation stage includes training and maintenance, and during this stage costs are expensed as incurred. Capitalization begins when both the preliminary project stage is completed and management commits to funding the project. Capitalization ceases at the point the project is substantially complete and ready for its intended use, that is, after all substantial testing is completed. Costs of specified upgrades and enhancements to internal-use software are capitalized if it is probable that those expenditures result in additional functionality. Capitalized costs are amortized on a straight line basis over the estimated useful life.

Summary of Significant Accounting Policies

As permitted by the rules of the Securities and Exchange Commission applicable to Quarterly Reports on Form 10-Q, these notes are condensed and do not contain all disclosures required by generally accepted accounting principles (GAAP). Cognex Corporation (the "Company") has provided new disclosures related to inventories and internal-use software in this quarterly report on Form 10-Q. Reference should be made to the consolidated financial statements and related notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2016 for a full description of significant accounting policies.

In the opinion of the management of the Company, the accompanying consolidated unaudited financial statements contain all adjustments, consisting of normal, recurring adjustments and financial statement reclassifications, including those related to the disposition of a business, necessary to present fairly the Company’s financial position as of April 2, 2017, and the results of its operations for the three-month periods ended April 2, 2017 and April 3, 2016, and changes in shareholders’ equity, comprehensive income, and cash flows for the periods presented.

The results disclosed in the Consolidated Statements of Operations for the three-month period ended April 2, 2017 are not necessarily indicative of the results to be expected for the full year.

Inventories

On January 1, 2017, the Company adopted Accounting Standards Update (ASU) 2015-11 "Inventory - Simplifying the Measurement of Inventory." This Update requires companies to measure inventory at the lower of cost and net realizable value. Net realizable value is the estimated selling prices in the ordinary course of business, less reasonably predictable costs of completion, disposal, and transportation. This adoption did not have an impact on the Company's inventory value.

Internal-use Software

The Company accounts for the costs of computer software developed or obtained for internal use under Accounting Standards Codification 350-40 "Intangibles - Goodwill and Other, Internal-use Software." Internal-use software is software acquired, internally developed, or modified solely to meet the entity's internal needs, and during the software's development, no substantive plan exists to sell the software.

The preliminary project stage includes determination of system requirements, vendor demonstrations, and final selection of vendors, and during this stage costs are expensed as incurred. The application development stage includes software design, coding, hardware installation, and testing. During this stage, certain costs are capitalized, including external direct costs of materials and services, as well as payroll and payroll-related costs for employees who are directly associated with the project, while certain costs are expensed as incurred, including training and data conversion costs. The post-implementation stage includes training and maintenance, and during this stage costs are expensed as incurred.

Capitalization begins when both the preliminary project stage is completed and management commits to funding the project. Capitalization ceases at the point the project is substantially complete and ready for its intended use, that is, after all substantial testing is completed. Costs of specified upgrades and enhancements to internal-use software are capitalized if it is probable that those expenditures result in additional functionality. Capitalized costs are amortized on a straight line basis over the estimated useful life.