Business and Significant Accounting Policies (Policies)	12 Months Ended
Business and Significant Accounting Policies (Policies)	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of presentation	The accompanying 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 financial information and with the applicable instructions of U.S. Securities & Exchange Commission (“SEC”) Regulation S-X. The fiscal year of Gartner is the twelve-month period from January 1 through December 31. All references to 2017, 2016 and 2015 herein refer to the fiscal year unless otherwise indicated.
Principles of consolidation	The accompanying 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 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 the accompanying consolidated financial statements to be reasonable. Management continually 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 consolidated financial statements in future periods.
Business Acquisitions	The Company completed acquisitions in each of the three years ended December 31, 2017 and detailed information related to these acquisitions is included in Note 2 — Acquisitions and Divestiture. The Company accounts for acquisitions in accordance with the acquisition method of accounting as prescribed by FASB ASC Topic No. 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 determination of the fair values of intangible and other assets acquired in acquisitions requires management judgment and the consideration of a number of factors, significant among them the historical financial performance of the acquired businesses and projected performance, estimates surrounding customer turnover, as well as assumptions regarding the level of competition and the cost to reproduce certain assets. Establishing the useful lives of the intangibles also requires management judgment and the evaluation of a number of factors, among them projected cash flows and the likelihood of competition. The Company classifies charges that are directly-related to its acquisitions in the line Acquisition and integration charges in the Consolidated Statements of Operations. The Company recorded $158.5 million, $42.6 million and $26.2 million of such charges in 2017, 2016 and 2015, respectively. Included in these directly-related and incremental charges are legal, consulting, retention, severance, and accruals for cash payments subject to the continuing employment of certain key employees of the acquired companies.
Revenue Recognition	Revenue is recognized in accordance with U.S. GAAP and SEC Staff Accounting Bulletin No. 104, Revenue Recognition (“SAB 104”). Revenues are only recognized once all required criteria for recognition have been met. The accompanying Consolidated Statements of Operations present revenues net of any sales or value-added taxes that we collect from customers and remit to government authorities. On January 1, 2018, the Company adopted FASB Accounting Standards Update ("ASU") No. 2014-09, "Revenue from Contracts with Customers" ("ASU No. 2014-09") which requires changes in revenue recognition policies as well as enhanced disclosures. The adoption of ASU No. 2014-09 did not have a material impact on the Company’s consolidated financial statements. Additional information regarding the Company's adoption of ASU No. 2014-09 is provided below in the section titled Accounting standards issued but not yet adopted. The Company’s revenues by significant source are as follows: Research Research revenues are mainly derived from subscription contracts for research products. The related revenues are deferred and recognized ratably over the applicable contract term. Fees derived from assisting organizations in selecting the right business software for their needs are recognized as earned when the leads are provided to vendors. The Company typically enters into subscription contracts for research products for twelve-month periods or longer. The majority of research contracts are billable upon signing, absent special terms granted on a limited basis from time to time. Research contracts are non-cancelable and non-refundable, except for government contracts that may have cancellation or fiscal funding clauses, which historically have not produced material cancellations. It is our policy to record the amount of the contract that is billable as a fee receivable at the time the contract is signed with a corresponding amount as deferred revenue, since the contract represents a legally enforceable claim. Consulting Consulting revenues, primarily derived from custom consulting and measurement services, are principally generated from fixed fee or time and materials engagements. Revenues from fixed fee engagements are recognized on a proportional performance basis, while revenues from time and material engagements are recognized as work is delivered and/or services are provided. Revenues related to contract optimization engagements are contingent in nature and are only recognized upon satisfaction of all conditions related to their payment. Unbilled fees receivable associated with consulting engagements were $66.2 million at December 31, 2017 and $45.7 million at December 31, 2016. Events Events revenues are deferred and recognized upon the completion of the related symposium, conference or exhibition. In addition, the Company defers certain costs directly related to events and expenses these costs in the period during which the related symposium, conference or exhibition occurs. The Company's policy is to defer only those costs, primarily prepaid site and production services costs, which are incremental and are directly attributable to a specific event. Other costs of organizing and producing our events, primarily Company personnel and non-event specific expenses, are expensed in the period incurred. At the end of each fiscal quarter, the Company assesses on an event-by-event basis whether the expected direct costs of producing a scheduled event will exceed the expected revenues. If such costs are expected to exceed revenues, the Company records the expected loss in the period determined. Talent Assessment & Other Talent Assessment & Other revenues arising from knowledge and skill assessment services are recognized depending on the nature of the underlying contract: (i) ratably over the term of the service period; (ii) upon delivery; or (iii) on a proportional performance basis. Revenues from training programs and survey and questionnaire products are primarily recognized upon delivery of the service.
Allowance for losses	The Company maintains an allowance for losses which is composed of a bad debt allowance and a sales reserve. Provisions are charged against earnings, either as a reduction in revenues or an increase to expense. The determination of the allowance for losses is based on historical loss experience, an assessment of current economic conditions, the aging of outstanding receivables, the financial health of specific clients, and probable losses.
Cost of services and product development	COS expense includes the direct costs incurred in the creation and delivery of our products and services. These costs primarily relate to personnel.
Selling, general and administrative	SG&A expense includes direct and indirect selling costs, general and administrative costs, and charges against earnings related to uncollectible accounts.
Commissions expense	The Company records deferred commissions upon the signing of customer contracts and amortizes the deferred amount as commission expense over the period in which the related revenues are earned. Commission expense is included in SG&A in the Consolidated Statements of Operations.
Stock-based compensation expense	The Company accounts for stock-based compensation awards in accordance with FASB ASC Topics 505 and 718 and SEC Staff Accounting Bulletins No. 107 and No. 110. Stock-based compensation expense is based on the fair value of the award on the date of grant. The Company recognizes stock-based compensation expense over the period that the related service is performed, which is generally the same as the vesting period of the underlying award.
Income taxes	The Company uses the asset and liability method of accounting for income taxes. We estimate our income taxes in each of the jurisdictions where we operate. This process involves estimating our current tax expense together with assessing temporary differences resulting from differing treatment of items for tax and accounting purposes. These differences result in deferred tax assets and liabilities, which are included within our consolidated balance sheets. In assessing the realizability of deferred tax assets, management considers if it is more likely than not that some or all of the deferred tax assets will not be realized. We consider the availability of loss carryforwards, projected reversal of deferred tax liabilities, projected future taxable income, and ongoing prudent and feasible tax planning strategies in making this assessment. The Company recognizes the tax benefit from an uncertain tax position only if it is more likely than not the tax position will be sustained based on the technical merits of the position.
Cash and cash equivalents	Includes cash and all highly liquid investments with original maturities of three months or less, which are considered cash equivalents. The carrying value of cash equivalents approximates fair value due to their short-term maturity. Investments with maturities of more than three months are classified as marketable securities. Interest earned is classified in Interest income in the Consolidated Statements of Operations.
Property, equipment and leasehold improvements	The Company leases all of its facilities and certain equipment. These leases are all classified as operating leases in accordance with FASB ASC Topic 840. The cost of these operating leases, including any contractual rent increases, rent concessions, and landlord incentives, are recognized ratably over the life of the related lease agreement. Equipment, leasehold improvements, and other fixed assets owned by the Company are recorded at cost less accumulated depreciation. Except for leasehold improvements, these fixed assets are depreciated using the straight-line method over the estimated useful lives of the assets. Leasehold improvements are amortized using the straight-line method over the shorter of the estimated useful lives of the improvement or the remaining term of the related lease. The Company incurs costs to develop internal use software used in our operations, and certain of these costs meeting the criteria outlined in FASB ASC Topic No. 350 are capitalized and amortized over future periods.
Finite-Lived Intangible assets	The Company has finite-lived intangible assets which are amortized against earnings using the straight-line method over their expected useful lives.
Goodwill	Goodwill represents the excess of the purchase price of acquired businesses over the estimated fair value of the tangible and identifiable intangible net assets acquired. Evaluations of the recoverability of goodwill are performed in accordance with FASB ASC Topic 350, which requires an annual assessment of potential goodwill impairment at the reporting unit level and whenever events or changes in circumstances indicate that the carrying value of goodwill may not be recoverable. The annual assessment of the recoverability of recorded goodwill can be based on either a qualitative or quantitative assessment or a combination of the two approaches. Both methods utilize estimates which, in turn, require judgments and assumptions regarding future trends and events. As a result, both the precision and reliability of the resulting estimates are subject to uncertainty. If our annual goodwill impairment evaluation determines that the fair value of a reporting unit is less than its related carrying amount, we may recognize an impairment charge.
Impairment of long-lived assets	The Company's long-lived assets primarily consist of intangible assets other than goodwill and property, equipment, and leasehold improvements. The Company reviews its long-lived asset groups for impairment whenever events or changes in circumstances indicate that the carrying amount of the respective asset may not be recoverable. Such evaluation may be based on a number of factors including current and projected operating results and cash flows, changes in management’s strategic direction as well as external economic and market factors. The Company evaluates the recoverability of these assets by determining whether the carrying value can be recovered through undiscounted future operating cash flows. If events or circumstances indicate that the carrying value might not be recoverable based on undiscounted future operating cash flows, an impairment loss would be recognized. The amount of impairment, if any, is measured based on the difference between projected discounted future operating cash flows using a discount rate reflecting the Company’s average cost of funds and the carrying value of the asset.
Pension obligations	The Company has defined-benefit pension plans in several of its international locations (see Note 13 — Employee Benefits). Benefits earned under these plans are generally based on years of service and level of employee compensation. The Company accounts for defined benefit plans in accordance with the requirements of FASB ASC Topic No. 715. The Company determines the periodic pension expense and related liabilities for these plans through actuarial assumptions and valuations.
Debt	The Company presents amounts borrowed in the Consolidated Balance Sheets at amortized cost, net of deferred financing fees. Interest accrued on amounts borrowed is classified in Interest expense in the Consolidated Statements of Operations.
Foreign currency exposure	The functional currency of our foreign subsidiaries is typically the local currency. All assets and liabilities of foreign subsidiaries are translated into U.S. dollars at exchange rates in effect at the balance sheet date. Income and expense items are translated at average exchange rates for the year. The resulting translation adjustments are recorded as foreign currency translation adjustments, a component of Accumulated other comprehensive income (loss), net within the Stockholders’ Equity section of the Consolidated Balance Sheets. Currency transaction gains or losses arising from transactions denominated in currencies other than the functional currency of a subsidiary are recognized in results of operations in Other income, net within the Consolidated Statements of Operations. The Company had net currency transaction losses of $(5.5) million, $(0.4) million, and $(2.6) million in 2017, 2016, and 2015, respectively. The Company enters into foreign currency forward exchange contracts to mitigate the effects of adverse fluctuations in foreign currency exchange rates on these transactions. These contracts generally have a short duration and are recorded at fair value with both realized and unrealized gains and losses recorded in Other income, net.
Comprehensive income	The Company reports comprehensive income in a separate statement called the Consolidated Statements of Comprehensive Income, which is included herein.
Fair value disclosures	The Company has a limited number of assets and liabilities that are adjusted to fair value at each balance sheet date.
Concentrations of credit risk	Assets that may subject the Company to concentration of credit risk consist primarily of short-term, highly liquid investments classified as cash equivalents, fees receivable, interest rate swaps, and a pension reinsurance asset. The majority of the Company’s cash equivalent investments and its interest rate swap contracts are with investment grade commercial banks. Fees receivable balances deemed to be collectible from customers have limited concentration of credit risk due to our diverse customer base and geographic dispersion. The Company’s pension reinsurance asset (see Note 13 — Employee Benefits) is maintained with a large international insurance company that was rated investment grade as of December 31, 2017 and 2016.
Stock repurchase programs	The Company records the cost to repurchase its own common shares to treasury stock. During 2017, 2016 and 2015, the Company used $41.3 million, $59.0 million, and $509.0 million, respectively, in cash for stock repurchases (see Note 7 — Stockholders’ Equity for additional information). Shares repurchased by the Company are added to treasury shares and are not retired.
Adoption of new accounting standards	Effective January 1, 2016, the Company adopted FASB ASU No. 2016-09, "Improvements to Employee Share-Based Payment Accounting" ("ASU No. 2016-09"). ASU No. 2016-09 mandated certain changes in accounting for stock-based compensation, including a requirement that excess tax benefits or deficiencies resulting from stock-based compensation awards be recognized in income tax expense or benefit subsequent to the date of adopting the new accounting standard. Previously, an entity’s excess tax benefits or deficiencies were recorded in additional paid-in capital. ASU No. 2016-09 also requires that excess tax benefits related to stock-based compensation awards be reported as an operating activity in an entity’s statement of cash flows. Previously, excess tax benefits were reported as financing activities. As permitted by ASU No. 2016-09, the Company elected to apply these changes prospectively, commencing on January 1, 2016. The provisions of ASU No. 2016-09 had no impact on our financial results for periods prior to 2016. If the Company had applied ASU No. 2016-09 to 2015: (i) income tax expense would have declined by $13.9 million; (ii) basic and diluted income per share would have increased by $0.17 and $0.16, respectively; and (iii) cash provided by operating activities would have increased by $13.9 million. ASU No. 2016-09 also permits companies to make an entity-wide accounting policy election to recognize forfeitures of share-based compensation awards as they occur or make an estimate by applying a forfeiture rate each quarter. The Company previously estimated forfeitures but optionally elected to change its accounting policy and account for forfeitures as they occur. ASU No. 2016-09 requires this change in accounting policy to be applied using a cumulative effect adjustment to accumulated earnings as of the beginning of the period in which the rule is adopted. Accordingly, the Company recorded a $0.3 million decrease to its opening accumulated earnings effective January 1, 2016. The Company did not adopt any significant new accounting standards during 2017. Accounting standards issued but not yet adopted. The FASB has issued 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: Accounting standards effective in 2018 Stock Compensation Award Modifications — In May 2017, the FASB issued ASU No. 2017-09, "Compensation—Stock Compensation - Scope of Modification Accounting" ("ASU No. 2017-09"). ASU No. 2017-09 provides guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting. ASU No. 2017-09 was effective for Gartner on January 1, 2018. We have concluded that the adoption of ASU No. 2017-09 will not have a material impact on the Company's consolidated financial statements. Retirement Benefits Cost Presentation — In March 2017, the FASB issued ASU No. 2017-07, "Compensation—Retirement Benefits" ("ASU No. 2017-07"). ASU No. 2017-07 improves the reporting of net benefit cost in the financial statements, and provides additional guidance on the presentation of net benefit cost in the income statement and clarifies the components eligible for capitalization. ASU No. 2017-07 was effective for Gartner on January 1, 2018. We have concluded that the adoption of ASU No. 2017-07 will not have a material impact on the Company's consolidated financial statements. Partial Sales of Non-financial Assets — In February 2017, the FASB issued ASU No. 2017-05, "Clarifying the Scope of Asset Derecognition Guidance and Accounting for Partial Sales of Non-financial Assets" ("ASU No. 2017-05"). ASU No. 2017-05 clarifies the scope of the FASB’s recently established guidance on non-financial asset de-recognition as well as the accounting for partial sales of non-financial assets. It conforms the de-recognition guidance on non-financial assets with the model for revenue transactions. ASU No. 2017-05 was effective for Gartner on January 1, 2018. We have concluded that the adoption of ASU No. 2017-05 will not have a material impact on the Company's consolidated financial statements. Definition of a Business — In January 2017, the FASB issued ASU No. 2017-01, "Clarifying the Definition of a Business" ("ASU No. 2017-01"), which was effective for Gartner on January 1, 2018. ASU No. 2017-01 changes the U.S. GAAP definition of a business which can impact the accounting for asset purchases, acquisitions, goodwill impairment, and other assessments. We have concluded that the adoption of ASU No. 2017-01 will not have a material impact on the Company's consolidated financial statements. Presentation of Restricted Cash — In November 2016, the FASB issued ASU No. 2016-18, "Restricted Cash" ("ASU No. 2016-18"). ASU No. 2016-18 requires that amounts generally described as restricted cash and restricted cash equivalents be presented with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. If different, a reconciliation of the cash balances reported in the cash flow statement and the balance sheet would need to be provided along with explanatory information. ASU No. 2016-18 was effective for Gartner on January 1, 2018. The adoption of ASU No. 2016-18 will require the Company to disclose restricted cash and, as a result, will change the presentation of its consolidated statements of cash flows. Income Taxes — In October 2016, the FASB issued ASU No. 2016-16, "Intra-Entity Transfers of Assets Other Than Inventory" ("ASU No. 2016-16"). ASU No. 2016-16 accelerates the recognition of taxes on certain intra-entity transactions and was effective for Gartner on January 1, 2018. Current U.S. GAAP requires deferral of the income tax implications of an intercompany sale of assets until the assets are sold to a third party or recovered through use. Under the new rule, the seller’s tax effects and the buyer’s deferred taxes on post-adoption asset transfers will be immediately recognized upon the sale. On the date of adoption of ASU No. 2016-16 any taxes attributable to pre-2018 intra-entity transfers that were previously deferred will be accelerated and recorded to accumulated earnings as permitted by the transition rules. ASU 2016-16 could have a material impact on our consolidated financial statements in the future depending on the nature, size, and tax consequences of future intra-entity transfers, if any. Statement of Cash Flows — In August 2016, the FASB issued ASU No. 2016-15, "Classification of Certain Cash Receipts and Cash Payments" ("ASU No. 2016-15"). ASU No. 2016-15 sets forth classification requirements for certain cash flow transactions. ASU No. 2016-15 was effective for Gartner on January 1, 2018. We have concluded that the adoption of ASU No. 2016-15 will not have a material impact on the Company's consolidated financial statements. Financial Instruments Recognition and Measurement — In January 2016, the FASB issued ASU No. 2016-01, "Financial Instruments Overall - Recognition and Measurement of Financial Assets and Liabilities" ("ASU No. 2016-01") to address certain aspects of recognition, measurement, presentation, and disclosure of financial instruments. Among the significant changes required by ASU No. 2016-01 is that equity investments will be measured at fair value with changes in fair value recognized in net income. ASU No. 2016-01 was effective for Gartner on January 1, 2018. We have concluded that the adoption of ASU No. 2016-01 will not have a material impact on the Company's consolidated financial statements. Revenue Recognition — 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 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 disclosures. ASU No. 2014-09 also requires significantly expanded disclosures around the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers. An entity may adopt ASU No. 2014-09 using either a full retrospective approach for each prior reporting period presented or a modified retrospective approach (the cumulative effect method). The Company adopted ASU No. 2014-09 on January 1, 2018 using the cumulative effect method of adoption. The adoption of ASU No. 2014-09 did not have a material impact on the Company’s consolidated financial statements. The adoption of the standard does require the Company to reclassify certain immaterial amounts in the Company’s consolidated balance sheet as well as provide the enhanced disclosures required by the standard, both of which will be provided in the Company's Form 10-Q filing for the quarterly period ending March 31, 2018. Accounting standards effective in 2019 Targeted Improvements to Accounting for Hedging Activities - In August 2017, the FASB issued ASU No. 2017-12, "Derivatives and Hedging ("ASU No. 2017-12"). ASU No. 2017-12 is intended to improve the financial reporting of hedging relationships to better portray economic results of an entity’s risk management activities in its financial statements. In addition to that main objective, the standard makes certain targeted improvements to simplify the application of the hedge accounting guidance in current U.S. GAAP. ASU No. 2017-12 is effective for Gartner on January 1, 2019. We are currently evaluating the impact of ASU No. 2017-12 on the Company's consolidated financial statements. Distinguishing Liabilities from Equity — In July 2017, the FASB issued ASU No. 2017-11, "Earnings Per Share, Distinguishing Liabilities from Equity, and Derivatives and Hedging" ("ASU No. 2017-11"). ASU No. 2017-11 is intended to simplify the accounting for financial instruments with characteristics of liabilities and equity. Among the issues addressed are: (i) determining whether an instrument (or embedded feature) is indexed to an entity’s own stock; (ii) distinguishing liabilities from equity for mandatorily redeemable financial instruments of certain nonpublic entities; and (iii) identifying mandatorily redeemable non-controlling interests. ASU No. 2017-11 is effective for Gartner on January 1, 2019. We are currently evaluating the potential impact of ASU No. 2017-11 on the Company's consolidated financial statements. Leases — In February 2016, the FASB issued ASU No. 2016-02, "Leases" ("ASU No. 2016-02") which will require significant changes in the accounting and disclosure for lease arrangements. Currently under U.S. GAAP, lease arrangements that meet certain criteria are considered operating leases and are not recorded on the balance sheet. All of the Company's existing lease arrangements are accounted for as operating leases and are thus not recorded on the Company's balance sheet. ASU No. 2016-02 will significantly change the accounting for leases since a right-of-use ("ROU") model must be used in which the lessee must record a ROU asset and a lease liability on the balance sheet for leases with terms longer than 12 months. Leases will be classified as either finance or operating arrangements, with classification affecting the pattern of expense recognition in the income statement. ASU No. 2016-02 also requires expanded disclosures about leasing arrangements. ASU No. 2016-02 will be effective for Gartner on January 1, 2019. We are currently evaluating the potential impact of ASU No. 2016-02 on our consolidated financial statements. Accounting standards effective in 2020 Goodwill Impairment — In January 2017, the FASB issued ASU No. 2017-04, "Intangibles—Goodwill and Other - Simplifying the Test for Goodwill Impairment" ("ASU No. 2017-04"). ASU No. 2017-04 simplifies the determination of the amount of goodwill to be potentially charged off by eliminating Step 2 of the current goodwill impairment test. ASU No. 2017-04 is effective for Gartner on January 1, 2020. We have concluded that the adoption of ASU No. 2017-04 will not have a material impact on the Company's consolidated financial statements. Financial Instrument Credit Losses — In June 2016, the FASB issued ASU No. 2016-13, "Financial Instruments—Credit Losses" ("ASU No. 2016-13"). ASU No. 2016-13 amends the current financial instrument impairment model by requiring entities to use a forward-looking approach based on expected losses to estimate credit losses on certain types of financial instruments, including trade receivables. ASU No. 2016-13 is effective for Gartner on January 1, 2020, with early adoption permitted. We are currently evaluating the potential impact of ASU No. 2016-13 on our consolidated financial statements. 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.