Basis of Presentation	9 Months Ended
Oct. 02, 2015
Accounting Policies [Abstract]
Basis of Presentation	1. Basis of Presentation GSI Group Inc. and its subsidiaries (collectively referred to as the “Company”, “we”, “us”, “our”) design, develop, manufacture and sell precision photonic and motion control components and subsystems to Original Equipment Manufacturers (“OEMs”) in the medical and advanced industrial markets. The Company is a leader in highly engineered enabling technologies, including CO2 laser sources, laser scanning and beam delivery products, optical data collection and machine vision technologies, medical visualization and informatics solutions, and precision motion control products. The Company specializes in collaborating with OEM customers to adapt its component and subsystem technologies to deliver highly differentiated performance in their applications. The accompanying unaudited interim consolidated financial statements have been prepared in U.S. dollars and pursuant to the rules and regulations of the United States Securities and Exchange Commission (“SEC”), the instructions to Form 10-Q and the provisions of Regulation S-X pertaining to interim financial statements. Accordingly, certain information and footnote disclosures normally included in the financial statements prepared in accordance with U.S. GAAP have been condensed or omitted pursuant to such rules and regulations. The interim consolidated financial statements and notes included in this report should be read in conjunction with the consolidated financial statements and notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2014. In the opinion of management, these interim consolidated financial statements include all adjustments and accruals of a normal and recurring nature necessary to fairly state the results of the interim periods presented. The results for interim periods are not necessarily indicative of results to be expected for the full year or for any future periods. During the second quarter ended July 3, 2015, the Company deconsolidated its 50% owned joint venture, Excel Laser Technology Private Limited (the “India JV”), as a result of an agreement executed in June 2015 to sell 100% of the Company’s interest in the India JV. The accounts of the India JV were previously included in discontinued operations in the consolidated financial statements. The Company owns 41% of Laser Quantum Ltd. (“Laser Quantum”), a privately held company located in the United Kingdom. The Company records the results of this entity under the equity method as it does not have a controlling interest in the entity. The Company’s unaudited interim financial statements are prepared on a quarterly basis ending on the Friday closest to the end of the calendar quarter, with the exception of the fourth quarter which always ends on December 31. Use of Estimates The preparation of financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the dates of the financial statements, and the reported amounts of revenues and expenses during the reporting periods. The Company evaluates its estimates based on historical experience, current conditions and various other assumptions that it believes are reasonable under the circumstances. Estimates and assumptions are reviewed on an on-going basis and the effects of revisions are reflected in the period in which they are deemed to be necessary. Actual results could differ significantly from those estimates. Recent Accounting Pronouncements Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity In April 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2014-08, “Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity.” ASU 2014-08 provides guidance on determining when disposals can be presented as discontinued operations. ASU 2014-08 requires that only disposals representing a strategic shift that has (or will have) a major effect on an entity’s operations and financial results should be presented as discontinued operations. A strategic shift may include a disposal of a major line of business, a major equity method investment or a major part of an entity. Additionally, ASU 2014-08 requires expanded disclosures regarding discontinued operations. ASU 2014-08 is effective prospectively for reporting periods beginning after December 15, 2014. The Company adopted this pronouncement in January 2015. Simplifying the Presentation of Debt Issuance Costs In April 2015, the FASB issued ASU 2015-03, “Simplifying the Presentation of Debt Issuance Costs.” ASU 2015-03 requires debt issuance related costs to be presented in the balance sheet as a direct reduction to the carrying amount of the associated debt liability, consistent with the presentation of a debt discount. The Company adopted the provisions of ASU 2015-03 retrospectively as of the fiscal quarter ended October 2, 2015. Prior period amounts have been reclassified to conform to the current period presentation. As of December 31, 2014, $0.2 million of debt issuance costs were reclassified from prepaid expenses and other current assets to current portion of long-term debt and $2.5 million was reclassified from other long-term assets to long-term debt in the consolidated balance sheet. Other than these reclassifications, the adoption of ASU 2015-03 did not have an impact on the Company’s consolidated financial statements. Customer’s Accounting for Fees Paid in a Cloud Computing Arrangement In April 2015, the FASB issued ASU 2015-05, “Customer’s Accounting for Fees Paid in a Cloud Computing Arrangement,” which provides guidance to customers about whether a cloud computing arrangement includes a software license. If a cloud computing arrangement includes a software license, the customer should account for the software license element of the arrangement consistent with the acquisition of other software licenses. If a cloud computing arrangement does not include a software license, the customer should account for the arrangement as a service contract. ASU 2015-05 will be effective for annual and interim reporting periods beginning after December 15, 2015, with early adoption permitted. Upon adoption, an entity may apply the new guidance either retrospectively or prospectively to all arrangements entered into or materially modified after the effective date. The Company is currently evaluating the impact of ASU 2015-05 on the Company’s consolidated financial statements. Business Combinations In September 2015, the FASB issued ASU 2015-16, “Business Combinations,” which requires an acquirer to recognize adjustments to provisional amounts that are identified during the measurement period in the reporting period in which the adjustment amounts are determined. ASU 2015-16 requires an entity to present separately on the face of the income statement or disclose in the notes the portion of the amount recorded in current-period earnings by line item that would have been recorded in previous reporting periods if the adjustment had been recognized at the acquisition date. ASU 2015-16 will be effective prospectively for reporting periods beginning after December 15, 2015. The Company is currently evaluating the impact of the new standard on the Company’s consolidated financial statements. Revenue from Contracts with Customers In May 2014, the FASB issued ASU 2014-09, “Revenue from Contracts with Customers”, which provides guidance for revenue recognition. ASU 2014-09 supersedes the revenue recognition requirements in Accounting Standards Codification (“ASC”) 605, “Revenue Recognition,” and requires entities to recognize revenue in a way that depicts the transfer of goods or services to customers at an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. ASU 2014-09 will be effective for annual and interim reporting periods beginning after December 15, 2016. Early adoption is not permitted. Upon adoption, an entity may apply the new guidance either retrospectively to each prior reporting period presented or retrospectively only to customer contracts not yet completed as of the date of adoption with the cumulative effect of initially applying the standard recognized in beginning retained earnings at the date of the initial application. In August 2015, the FASB issued ASU 2015-14, “Revenue from Contracts with Customers – Deferral of the Effective Date”, which defers the effective date of ASU 2014-09 by one year, with the option of early adoption as of the original effective date. The amendment in ASU 2015-14 will result in ASU 2014-09 being effective for annual and interim reporting periods beginning after December 15, 2017. The Company is currently evaluating the impact of the new standard on the Company’s consolidated financial statements. Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern In August 2014, the FASB issued ASU 2014-15, "Presentation of Financial Statements - Going Concern (Subtopic 205-40)," which requires management to assess a company’s ability to continue as a going concern and to provide related footnote disclosures in certain circumstances. ASU 2014-15 will be effective for annual reporting periods ending after December 15, 2016. Early application is permitted. The Company does not expect the adoption of ASU 2014-15 to have any impact on the Company’s consolidated financial statements.

1. Basis of Presentation

GSI Group Inc. and its subsidiaries (collectively referred to as the “Company”, “we”, “us”, “our”) design, develop, manufacture and sell precision photonic and motion control components and subsystems to Original Equipment Manufacturers (“OEMs”) in the medical and advanced industrial markets. The Company is a leader in highly engineered enabling technologies, including CO2 laser sources, laser scanning and beam delivery products, optical data collection and machine vision technologies, medical visualization and informatics solutions, and precision motion control products. The Company specializes in collaborating with OEM customers to adapt its component and subsystem technologies to deliver highly differentiated performance in their applications.

The accompanying unaudited interim consolidated financial statements have been prepared in U.S. dollars and pursuant to the rules and regulations of the United States Securities and Exchange Commission (“SEC”), the instructions to Form 10-Q and the provisions of Regulation S-X pertaining to interim financial statements. Accordingly, certain information and footnote disclosures normally included in the financial statements prepared in accordance with U.S. GAAP have been condensed or omitted pursuant to such rules and regulations. The interim consolidated financial statements and notes included in this report should be read in conjunction with the consolidated financial statements and notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2014. In the opinion of management, these interim consolidated financial statements include all adjustments and accruals of a normal and recurring nature necessary to fairly state the results of the interim periods presented. The results for interim periods are not necessarily indicative of results to be expected for the full year or for any future periods.

During the second quarter ended July 3, 2015, the Company deconsolidated its 50% owned joint venture, Excel Laser Technology Private Limited (the “India JV”), as a result of an agreement executed in June 2015 to sell 100% of the Company’s interest in the India JV. The accounts of the India JV were previously included in discontinued operations in the consolidated financial statements.

The Company owns 41% of Laser Quantum Ltd. (“Laser Quantum”), a privately held company located in the United Kingdom. The Company records the results of this entity under the equity method as it does not have a controlling interest in the entity.

The Company’s unaudited interim financial statements are prepared on a quarterly basis ending on the Friday closest to the end of the calendar quarter, with the exception of the fourth quarter which always ends on December 31.

Use of Estimates

The preparation of financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the dates of the financial statements, and the reported amounts of revenues and expenses during the reporting periods. The Company evaluates its estimates based on historical experience, current conditions and various other assumptions that it believes are reasonable under the circumstances. Estimates and assumptions are reviewed on an on-going basis and the effects of revisions are reflected in the period in which they are deemed to be necessary. Actual results could differ significantly from those estimates.

Recent Accounting Pronouncements

Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity

In April 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2014-08, “Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity.” ASU 2014-08 provides guidance on determining when disposals can be presented as discontinued operations. ASU 2014-08 requires that only disposals representing a strategic shift that has (or will have) a major effect on an entity’s operations and financial results should be presented as discontinued operations. A strategic shift may include a disposal of a major line of business, a major equity method investment or a major part of an entity. Additionally, ASU 2014-08 requires expanded disclosures regarding discontinued operations. ASU 2014-08 is effective prospectively for reporting periods beginning after December 15, 2014. The Company adopted this pronouncement in January 2015.

Simplifying the Presentation of Debt Issuance Costs

In April 2015, the FASB issued ASU 2015-03, “Simplifying the Presentation of Debt Issuance Costs.” ASU 2015-03 requires debt issuance related costs to be presented in the balance sheet as a direct reduction to the carrying amount of the associated debt liability, consistent with the presentation of a debt discount. The Company adopted the provisions of ASU 2015-03 retrospectively as of the fiscal quarter ended October 2, 2015. Prior period amounts have been reclassified to conform to the current period presentation. As of December 31, 2014, $0.2 million of debt issuance costs were reclassified from prepaid expenses and other current assets to current portion of long-term debt and $2.5 million was reclassified from other long-term assets to long-term debt in the consolidated balance sheet. Other than these reclassifications, the adoption of ASU 2015-03 did not have an impact on the Company’s consolidated financial statements.

Customer’s Accounting for Fees Paid in a Cloud Computing Arrangement

In April 2015, the FASB issued ASU 2015-05, “Customer’s Accounting for Fees Paid in a Cloud Computing Arrangement,” which provides guidance to customers about whether a cloud computing arrangement includes a software license. If a cloud computing arrangement includes a software license, the customer should account for the software license element of the arrangement consistent with the acquisition of other software licenses. If a cloud computing arrangement does not include a software license, the customer should account for the arrangement as a service contract. ASU 2015-05 will be effective for annual and interim reporting periods beginning after December 15, 2015, with early adoption permitted. Upon adoption, an entity may apply the new guidance either retrospectively or prospectively to all arrangements entered into or materially modified after the effective date. The Company is currently evaluating the impact of ASU 2015-05 on the Company’s consolidated financial statements.

Business Combinations

In September 2015, the FASB issued ASU 2015-16, “Business Combinations,” which requires an acquirer to recognize adjustments to provisional amounts that are identified during the measurement period in the reporting period in which the adjustment amounts are determined. ASU 2015-16 requires an entity to present separately on the face of the income statement or disclose in the notes the portion of the amount recorded in current-period earnings by line item that would have been recorded in previous reporting periods if the adjustment had been recognized at the acquisition date. ASU 2015-16 will be effective prospectively for reporting periods beginning after December 15, 2015. The Company is currently evaluating the impact of the new standard on the Company’s consolidated financial statements.

Revenue from Contracts with Customers

In May 2014, the FASB issued ASU 2014-09, “Revenue from Contracts with Customers”, which provides guidance for revenue recognition. ASU 2014-09 supersedes the revenue recognition requirements in Accounting Standards Codification (“ASC”) 605, “Revenue Recognition,” and requires entities to recognize revenue in a way that depicts the transfer of goods or services to customers at an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. ASU 2014-09 will be effective for annual and interim reporting periods beginning after December 15, 2016. Early adoption is not permitted. Upon adoption, an entity may apply the new guidance either retrospectively to each prior reporting period presented or retrospectively only to customer contracts not yet completed as of the date of adoption with the cumulative effect of initially applying the standard recognized in beginning retained earnings at the date of the initial application. In August 2015, the FASB issued ASU 2015-14, “Revenue from Contracts with Customers – Deferral of the Effective Date”, which defers the effective date of ASU 2014-09 by one year, with the option of early adoption as of the original effective date. The amendment in ASU 2015-14 will result in ASU 2014-09 being effective for annual and interim reporting periods beginning after December 15, 2017. The Company is currently evaluating the impact of the new standard on the Company’s consolidated financial statements.

Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern

In August 2014, the FASB issued ASU 2014-15, "Presentation of Financial Statements - Going Concern (Subtopic 205-40)," which requires management to assess a company’s ability to continue as a going concern and to provide related footnote disclosures in certain circumstances. ASU 2014-15 will be effective for annual reporting periods ending after December 15, 2016. Early application is permitted. The Company does not expect the adoption of ASU 2014-15 to have any impact on the Company’s consolidated financial statements.