Business and Basis of Presentation	3 Months Ended
Mar. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Business and Basis of Presentation	Business and Basis of Presentation Business. Gartner, Inc. is a global information technology research and advisory company founded in 1979 with its headquarters in Stamford, Connecticut. Gartner delivers its products and services globally through three business segments: Research, Consulting, and Events. When used in these notes, the terms “Gartner,” “Company,” “we,” “us,” or “our” refer to Gartner, Inc. and its consolidated subsidiaries. Basis of presentation. The accompanying interim condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“U.S. GAAP”), as defined in the Financial Accounting Standards Board ("FASB") Accounting Standards Codification (“ASC”) Topic 270 for interim financial information and with the applicable instructions of the U.S. Securities & Exchange Commission (“SEC”) Rule 10-01 of Regulation S-X on Form 10-Q and should be read in conjunction with the consolidated financial statements and related notes of the Company filed in its Annual Report on Form 10-K for the year ended December 31, 2015. The fiscal year of Gartner is the twelve-month calendar period from January 1 through December 31. In the opinion of management, all normal recurring accruals and adjustments considered necessary for a fair presentation of financial position, results of operations and cash flows at the dates and for the periods presented herein have been included. The results of operations for the three months ended March 31, 2016 may not be indicative of the results of operations for the remainder of 2016 or beyond. Principles of consolidation. The accompanying interim condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All significant intercompany transactions and balances have been eliminated. Use of estimates. The preparation of the accompanying interim condensed consolidated financial statements requires management to make estimates and assumptions about future events. These estimates and the underlying assumptions affect the amounts of assets and liabilities reported, disclosures about contingent assets and liabilities, and reported amounts of revenues and expenses. Such estimates include the valuation of fees receivable, goodwill, intangible assets, and other long-lived assets, as well as tax accruals and other liabilities. In addition, estimates are used in revenue recognition, income tax expense, performance-based compensation charges, depreciation and amortization. Management believes its use of estimates in these interim condensed consolidated financial statements to be reasonable. Management continuously evaluates and revises its estimates using historical experience and other factors, including the general economic environment and actions it may take in the future. Management adjusts these estimates when facts and circumstances dictate. However, these estimates may involve significant uncertainties and judgments and cannot be determined with precision. In addition, these estimates are based on management’s best judgment at a point in time. As a result, differences between our estimates and actual results could be material and would be reflected in the Company’s financial statements in future periods. Adoption of new accounting standards. The Company adopted the following new accounting standards during the three months ended March 31, 2016: Business Combinations — The Company adopted FASB Accounting Standards Update (ASU) 2015-16, "Business Combinations - Simplifying the Accounting for Measurement-Period Adjustments" ("ASU No. 2015-16") on January 1, 2016. ASU No. 2015-16 requires the recognition of adjustments to business combination provisional amounts, that are identified during the measurement period, in the reporting period in which the adjustments are determined. The effects of the adjustments to provisional amounts on depreciation, amortization or other income effects are required to be recognized in current-period earnings as if the accounting had been completed at the acquisition date. Disclosure of the portion of the adjustment recorded in current-period earnings that would have been reported in prior reporting periods if the adjustment to the provisional amounts had been recognized at the acquisition date is also required. The adoption of ASU No. 2015-16 did not have an impact on the Company’s consolidated financial statements at the date of adoption or for the three months ended March 31, 2016. However, ASU No. 2015-16 could have an impact on the Company's consolidated financial statements in the future if a transaction occurs within the scope of the rule. Debt Issuance Cost Presentation — The Company adopted FASB ASU No. 2015-03, “Simplifying the Presentation of Debt Issuance Costs” ("ASU No. 2015-03") on January 1, 2016. ASU No. 2015-03 requires that certain debt issuance costs related to our term loans be presented in the balance sheet as a direct deduction from the carrying amount of the liability. Previously such costs were presented on the balance sheet as deferred assets. The adoption of ASU No. 2015-03 did not have an impact on the Company’s consolidated balance sheet at adoption since the Company did not have any of these specific debt issuance costs recorded in its accounts. However, ASU No. 2015-03 could impact the Company's balance sheet presentation in the future if the Company incurs debt issuance costs that are covered by the standard. Recently issued accounting Standards. The FASB has also issued several accounting standards that have not yet become effective and that may impact the Company’s consolidated financial statements or related disclosures in future periods. These standards and their potential impact are discussed below: Stock-Based Compensation—In March 2016, the FASB issued Accounting Standards Update (ASU) No. 2016-09, Improvements to Employee Share-Based Payment Accounting ("ASU No. 2016-09"). ASU 2016-09 modifies several aspects of the accounting for employee share-based payment transactions, to include the accounting for income taxes, forfeitures, and statutory tax withholding requirements, as well as the classification of related amounts within the statement of cash flows. The provisions of the new rule will be effective for Gartner on January 1, 2017, with early adoption permitted. We are currently evaluating the potential impact of ASU No. 2016-09 on the Company's consolidated financial statements upon adoption. Leases — In February 2016, the FASB issued ASU 2016-02, "Leases" ("ASU No. 2016-02") which will require significant changes in the accounting and disclosure of lease arrangements. Among the significant changes required by ASU No. 2016-02 is that almost all lease obligations will be recorded on the balance sheet as a liability, along with a corresponding right of use asset. Currently under U.S. GAAP, lease arrangements that meet certain criteria are considered operating leases and are not recorded on the balance sheet. ASU No. 2016-02 also requires certain key information about leasing arrangements be disclosed. ASU No. 2016-02 will be effective for Gartner on January 1, 2019. We are currently evaluating the impact of ASU No. 2016-02. Revenue — In May 2014, the FASB issued ASU No. 2014-09, "Revenue from Contracts with Customers" ("ASU No. 2014-09"). ASU No. 2014-09 and related amendments require changes in revenue recognition policies as well as require enhanced disclosures. ASU No. 2014-09 is intended to clarify the principles for recognizing revenue by removing inconsistencies and weaknesses in existing revenue recognition rules; provide a more robust framework for addressing revenue recognition issues; improve comparability of revenue recognition practices across entities, industries, jurisdictions and capital markets; and provide more useful information to users of financial statements through improved revenue disclosures. ASU No. 2014-09 will be effective for Gartner on January 1, 2018. We continue to evaluate the impact of ASU No. 2014-09 on the Company's consolidated financial statements upon adoption. The FASB also continues to work on a number of other significant accounting standards which if issued could materially impact the Company's accounting policies and disclosures in future periods. However, since these standards have not yet been issued, the effective dates and potential impact are unknown. Acquisitions. The Company accounts for business acquisitions in accordance with the acquisition method of accounting as prescribed by FASB ASC Topic 805, Business Combinations. The acquisition method of accounting requires the Company to record the net assets and liabilities acquired based on their estimated fair values as of the acquisition date, with any excess of the consideration transferred over the estimated fair value of the net assets acquired, including identifiable intangible assets, to be recorded to goodwill. Under the acquisition method, the operating results of acquired companies are included in the Company's consolidated financial statements beginning on the date of acquisition. The Company recognized $8.4 million and $5.1 million of acquisition and integration charges in the three months ended March 31, 2016 and 2015, respectively, related to prior business acquisitions. These charges are classified in Acquisition and integration charges in the Condensed Consolidated Statements of Operations and include amounts accrued for payments contingent on the achievement of certain employment conditions, legal, consulting, and severance costs. The Company paid $22.7 million in the three months ended March 31, 2016 for the achievement of certain employment conditions related to an acquisition completed in 2014, of which $13.6 million was paid from escrow and $9.1 million was paid from existing Company cash. During the same period the Company also paid $0.8 million for an immaterial working capital adjustment related to one of its 2015 acquisitions.

Business and Basis of Presentation

Business. Gartner, Inc. is a global information technology research and advisory company founded in 1979 with its headquarters in Stamford, Connecticut. Gartner delivers its products and services globally through three business segments: Research, Consulting, and Events. When used in these notes, the terms “Gartner,” “Company,” “we,” “us,” or “our” refer to Gartner, Inc. and its consolidated subsidiaries.

Basis of presentation. The accompanying interim condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“U.S. GAAP”), as defined in the Financial Accounting Standards Board ("FASB") Accounting Standards Codification (“ASC”) Topic 270 for interim financial information and with the applicable instructions of the U.S. Securities & Exchange Commission (“SEC”) Rule 10-01 of Regulation S-X on Form 10-Q and should be read in conjunction with the consolidated financial statements and related notes of the Company filed in its Annual Report on Form 10-K for the year ended December 31, 2015. The fiscal year of Gartner is the twelve-month calendar period from January 1 through December 31. In the opinion of management, all normal recurring accruals and adjustments considered necessary for a fair presentation of financial position, results of operations and cash flows at the dates and for the periods presented herein have been included. The results of operations for the three months ended March 31, 2016 may not be indicative of the results of operations for the remainder of 2016 or beyond.

Principles of consolidation. The accompanying interim condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All significant intercompany transactions and balances have been eliminated.

Use of estimates. The preparation of the accompanying interim condensed consolidated financial statements requires management to make estimates and assumptions about future events. These estimates and the underlying assumptions affect the amounts of assets and liabilities reported, disclosures about contingent assets and liabilities, and reported amounts of revenues and expenses. Such estimates include the valuation of fees receivable, goodwill, intangible assets, and other long-lived assets, as well as tax accruals and other liabilities. In addition, estimates are used in revenue recognition, income tax expense, performance-based compensation charges, depreciation and amortization. Management believes its use of estimates in these interim condensed consolidated financial statements to be reasonable.

Management continuously evaluates and revises its estimates using historical experience and other factors, including the general economic environment and actions it may take in the future. Management adjusts these estimates when facts and circumstances dictate. However, these estimates may involve significant uncertainties and judgments and cannot be determined with precision. In addition, these estimates are based on management’s best judgment at a point in time. As a result, differences between our estimates and actual results could be material and would be reflected in the Company’s financial statements in future periods.

Adoption of new accounting standards. The Company adopted the following new accounting standards during the three months ended March 31, 2016:

Business Combinations — The Company adopted FASB Accounting Standards Update (ASU) 2015-16, "Business Combinations - Simplifying the Accounting for Measurement-Period Adjustments" ("ASU No. 2015-16") on January 1, 2016. ASU No. 2015-16 requires the recognition of adjustments to business combination provisional amounts, that are identified during the measurement period, in the reporting period in which the adjustments are determined. The effects of the adjustments to provisional amounts on depreciation, amortization or other income effects are required to be recognized in current-period earnings as if the accounting had been completed at the acquisition date. Disclosure of the portion of the adjustment recorded in current-period earnings that would have been reported in prior reporting periods if the adjustment to the provisional amounts had been recognized at the acquisition date is also required. The adoption of ASU No. 2015-16 did not have an impact on the Company’s consolidated financial statements at the date of adoption or for the three months ended March 31, 2016. However, ASU No. 2015-16 could have an impact on the Company's consolidated financial statements in the future if a transaction occurs within the scope of the rule.

Debt Issuance Cost Presentation — The Company adopted FASB ASU No. 2015-03, “Simplifying the Presentation of Debt Issuance Costs” ("ASU No. 2015-03") on January 1, 2016. ASU No. 2015-03 requires that certain debt issuance costs related to our term loans be presented in the balance sheet as a direct deduction from the carrying amount of the liability. Previously such costs were presented on the balance sheet as deferred assets. The adoption of ASU No. 2015-03 did not have an impact on the Company’s consolidated balance sheet at adoption since the Company did not have any of these specific debt issuance costs recorded in its accounts. However, ASU No. 2015-03 could impact the Company's balance sheet presentation in the future if the Company incurs debt issuance costs that are covered by the standard.

Recently issued accounting Standards. The FASB has also issued several accounting standards that have not yet become effective and that may impact the Company’s consolidated financial statements or related disclosures in future periods. These standards and their potential impact are discussed below:

Stock-Based Compensation—In March 2016, the FASB issued Accounting Standards Update (ASU) No. 2016-09, Improvements to Employee Share-Based Payment Accounting ("ASU No. 2016-09"). ASU 2016-09 modifies several aspects of the accounting for employee share-based payment transactions, to include the accounting for income taxes, forfeitures, and statutory tax withholding requirements, as well as the classification of related amounts within the statement of cash flows. The provisions of the new rule will be effective for Gartner on January 1, 2017, with early adoption permitted. We are currently evaluating the potential impact of ASU No. 2016-09 on the Company's consolidated financial statements upon adoption.

Leases — In February 2016, the FASB issued ASU 2016-02, "Leases" ("ASU No. 2016-02") which will require significant changes in the accounting and disclosure of lease arrangements. Among the significant changes required by ASU No. 2016-02 is that almost all lease obligations will be recorded on the balance sheet as a liability, along with a corresponding right of use asset. Currently under U.S. GAAP, lease arrangements that meet certain criteria are considered operating leases and are not recorded on the balance sheet. ASU No. 2016-02 also requires certain key information about leasing arrangements be disclosed. ASU No. 2016-02 will be effective for Gartner on January 1, 2019. We are currently evaluating the impact of ASU No. 2016-02.

Revenue — In May 2014, the FASB issued ASU No. 2014-09, "Revenue from Contracts with Customers" ("ASU No. 2014-09"). ASU No. 2014-09 and related amendments require changes in revenue recognition policies as well as require enhanced disclosures. ASU No. 2014-09 is intended to clarify the principles for recognizing revenue by removing inconsistencies and weaknesses in existing revenue recognition rules; provide a more robust framework for addressing revenue recognition issues; improve comparability of revenue recognition practices across entities, industries, jurisdictions and capital markets; and provide more useful information to users of financial statements through improved revenue disclosures. ASU No. 2014-09 will be effective for Gartner on January 1, 2018. We continue to evaluate the impact of ASU No. 2014-09 on the Company's consolidated financial statements upon adoption.

The FASB also continues to work on a number of other significant accounting standards which if issued could materially impact the Company's accounting policies and disclosures in future periods. However, since these standards have not yet been issued, the effective dates and potential impact are unknown.

Acquisitions. The Company accounts for business acquisitions in accordance with the acquisition method of accounting as prescribed by FASB ASC Topic 805, Business Combinations. The acquisition method of accounting requires the Company to record the net assets and liabilities acquired based on their estimated fair values as of the acquisition date, with any excess of the consideration transferred over the estimated fair value of the net assets acquired, including identifiable intangible assets, to be recorded to goodwill. Under the acquisition method, the operating results of acquired companies are included in the Company's consolidated financial statements beginning on the date of acquisition.

The Company recognized $8.4 million and $5.1 million of acquisition and integration charges in the three months ended March 31, 2016 and 2015, respectively, related to prior business acquisitions. These charges are classified in Acquisition and integration charges in the Condensed Consolidated Statements of Operations and include amounts accrued for payments contingent on the achievement of certain employment conditions, legal, consulting, and severance costs. The Company paid $22.7 million in the three months ended March 31, 2016 for the achievement of certain employment conditions related to an acquisition completed in 2014, of which $13.6 million was paid from escrow and $9.1 million was paid from existing Company cash. During the same period the Company also paid $0.8 million for an immaterial working capital adjustment related to one of its 2015 acquisitions.