Gartner (IT) 10-Q 4 May 17 2017 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2017	Apr. 30, 2017
Document and Entity Information [Abstract]
Entity Registrant Name	GARTNER INC
Entity Central Index Key	749,251
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Mar. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Common Stock, Shares Outstanding (in shares)		90,432,223

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 1,227,891	$ 474,233
Fees receivable, net of allowances of $7,900 and $7,400, respectively	716,487	643,013
Deferred commissions	139,771	141,410
Prepaid expenses and other current assets	91,546	84,540
Total current assets	2,175,695	1,343,196
Property, equipment and leasehold improvements, net	126,419	121,606
Goodwill	855,330	738,453
Intangible assets, net	81,209	76,801
Other assets	126,647	87,279
Total Assets	3,365,300	2,367,335
Current liabilities:
Accounts payable and accrued liabilities	331,828	440,771
Deferred revenues	1,109,162	989,478
Current portion of long-term debt	29,366	30,000
Total current liabilities	1,470,356	1,460,249
Long-term debt, net of deferred financing fees	1,599,331	664,391
Other liabilities	192,796	181,817
Total Liabilities	3,262,483	2,306,457
Stockholders’ Equity
Preferred stock, $.01 par value, 5,000,000 shares authorized; none issued or outstanding	0	0
Common stock, $.0005 par value, 250,000,000 shares authorized; 156,234,415 shares issued for both periods	78	78
Additional paid-in capital	880,877	863,127
Accumulated other comprehensive loss, net	(47,832)	(49,683)
Accumulated earnings	1,680,439	1,644,005
Treasury stock, at cost, 73,215,696 and 73,583,172 common shares, respectively	(2,410,745)	(2,396,649)
Total Stockholders’ Equity	102,817	60,878
Total Liabilities and Stockholders’ Equity	$ 3,365,300	$ 2,367,335

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 7,900	$ 7,400
Preferred stock par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	5,000,000	5,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock par value (in dollars per share)	$ 0.0005	$ 0.0005
Common stock, shares authorized (in shares)	250,000,000	250,000,000
Common stock, shares issued (in shares)	156,234,415	156,234,415
Treasury stock, shares (in shares)	73,215,696	73,583,172

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Revenues:
Research	$ 504,652	$ 440,271
Consulting	85,248	84,940
Events	35,269	32,055
Total revenues	625,169	557,266
Costs and expenses:
Cost of services and product development	237,609	212,041
Selling, general and administrative	304,244	257,411
Depreciation	10,240	8,834
Amortization of intangibles	6,290	6,183
Acquisition and integration charges	13,272	8,368
Total costs and expenses	571,655	492,837
Operating income	53,514	64,429
Interest expense, net	(5,906)	(6,006)
Other income, net	889	1,884
Income before income taxes	48,497	60,307
Provision for income taxes	12,064	15,320
Net income	$ 36,433	$ 44,987
Net income per share:
Basic (in dollars per share)	$ 0.44	$ 0.55
Diluted (in dollars per share)	$ 0.43	$ 0.54
Weighted average shares outstanding:
Basic (in shares)	82,835	82,451
Diluted (in shares)	84,095	83,464

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 36,433	$ 44,987
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	4,371	2,068
Interest rate swaps – net change in deferred loss	(2,568)	(7,133)
Pension – net change in deferred actuarial loss	48	37
Other comprehensive income (loss), net of tax	1,851	(5,028)
Comprehensive income	$ 38,284	$ 39,959

Condensed Consolidated Stateme6

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Operating activities:
Net income	$ 36,433	$ 44,987
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Depreciation and amortization	16,530	15,017
Stock-based compensation expense	22,576	15,495
Deferred taxes	(11,998)	(2,191)
Amortization and write-off of debt issuance costs	468	411
Changes in assets and liabilities:
Fees receivable, net	(57,919)	(19,089)
Deferred commissions	3,002	7,047
Prepaid expenses and other current assets	(5,315)	8,205
Other assets	(16,730)	5,436
Deferred revenues	92,373	79,141
Accounts payable, accrued, and other liabilities	(109,025)	(141,128)
Cash (used in) provided by operating activities	(29,605)	13,331
Investing activities:
Additions to property, equipment and leasehold improvements	(10,700)	(6,560)
Business acquisitions - cash paid (net of cash acquired)	(129,315)	(800)
Cash used in investing activities	(140,015)	(7,360)
Financing activities:
Proceeds from employee stock purchase plan	3,022	2,580
Proceeds from borrowings	955,000	70,000
Payments for debt issuance costs	0	0
Payments on borrowings	(18,773)	(5,000)
Purchases of treasury stock	(21,978)	(45,487)
Cash provided by financing activities	917,271	22,093
Net increase in cash and cash equivalents	747,651	28,064
Effects of exchange rates on cash and cash equivalents	6,007	2,903
Cash and cash equivalents, beginning of period	474,233	372,976
Cash and cash equivalents, end of period	$ 1,227,891	$ 403,943

Business and Basis of Presentat

Business and Basis of Presentation	3 Months Ended
	Mar. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Business and Basis of Presentation	Business and Basis of Presentation Business. Gartner, Inc. is the world's leading research and advisory company 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, 2016 . 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, 2017 may not be indicative of the results of operations for the remainder of 2017 or beyond. Principles of consolidation . The accompanying interim condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All 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 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. Subsequent Event. On April 5, 2017, the Company completed its previously announced acquisition of CEB Inc. ("CEB"). Note 14 — Subsequent Events provides information regarding the CEB acquisition. Impact of Stock-Based Compensation Accounting Rule Change . In the third quarter of 2016, the Company early adopted FASB Accounting Standards Update No. 2016-09, " Improvements to Employee Share-Based Payment Accounting" ("ASU No. 2016-09"), which changed the accounting for stock-based compensation awards. The accounting changes required by ASU No. 2016-09 were applied to the beginning of the Company's 2016 fiscal year, and as a result certain previously reported financial results for the three months ended March 31, 2016 were revised. These changes included a $4.8 million increase in net income, and a $0.06 increase in each of basic earnings per share and diluted earnings per share. In addition, our previously reported operating cash flow for the three months ended March 31, 2016 increased by $4.8 million . Adoption of new accounting standards. The Company did not adopt any new accounting standards in the first quarter of 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: Retirement Benefits 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 is effective for Gartner on January 1, 2018. We are currently evaluating the potential impact of ASU No. 2017-07 on the Company's consolidated financial statements. Defined Benefit Pension Plans Disclosure — In February 2017, the FASB issued ASU No. 2017-06, "Employee Benefit Plan Master Trust Reporting" ("ASU No. 2017-06"). ASU No. 2017-06 clarifies presentation requirements for a plan’s interest in certain trust arrangements as well as other changes. ASU No. 2017-06 is effective for Gartner on January 1, 2019. We are currently evaluating the potential impact of ASU No. 2017-06 on the Company's consolidated financial statements. Accounting for Partial Sales of Non-financial Asset s — 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 is effective for Gartner on January 1, 2018. We are currently evaluating the potential impact of ASU No. 2017-05 on the Company's consolidated financial statements. Simplifying the Test for 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 goodwill impairment test. ASU No. 2017-04 is effective for Gartner on January 1, 2020. We are currently evaluating the potential impact of ASU No. 2017-04 on the Company's consolidated financial statements. Business Combinations — In January 2017, the FASB issued ASU No. 2017-01, "Clarifying the Definition of a Business" ("ASU No. 2017-01"), which is effective for Gartner on January 1, 2018. ASU No. 2017-01 changes the GAAP definition of a business which can impact the accounting for asset purchases, acquisitions, goodwill impairment, and other assessments. We are currently evaluating the impact of ASU No. 2017-01 on the Company's consolidated financial statements. Statement of Cash Flows — 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 is effective for Gartner on January 1, 2018. We are currently evaluating the impact of ASU No. 2016-18 on the Company's consolidated financial statements. 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 is effective for Gartner on January 1, 2018. Current 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 will be immediately recognized upon the sale. We have completed an initial evaluation of the impact of ASU No. 2016-16 and believe it could have a material impact on our consolidated financial statements depending on the nature and size of future intra-entity transfers. 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 is effective for Gartner on January 1, 2018, but early adoption is permitted. We have completed an initial evaluation of the impact of ASU No. 2016-15 and we do not expect it will have a material impact on our 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. 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 impact of ASU No. 2016-02 on our 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 will be effective for Gartner on January 1, 2018. We have completed an initial evaluation of the impact of ASU No. 2016-01 and we do not expect it will have a material impact on our consolidated financial statements but may require additional disclosures. 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 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. The Company has completed an initial assessment of the impact of ASU No. 2014-09 on its existing revenue recognition policies and plans to adopt the rule on January 1, 2018 using the cumulative effect method of adoption. 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, which the Company is currently compiling. While the Company has not fully completed its assessment of the impact of ASU No. 2014-09, based on the analysis completed to date, the Company does not currently anticipate that the new rule will have a material impact on its 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. 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.

Acquisitions

Acquisitions	3 Months Ended
	Mar. 31, 2017
Business Combinations [Abstract]
Acquisitions	Acquisitions On March 9, 2017 , the Company acquired 100% of the outstanding capital stock of L2, Inc., ("L2"), a privately-held firm based in New York City with 150 employees, for a total purchase price of $155.0 million . L2 is a subscription-based research business that benchmarks the digital performance of brands. The Company paid $134.2 million in cash at close; but net of cash acquired with the business and for cash flow reporting purposes, the Company paid $129.3 million in cash. In addition, the Company may also be required to pay up to an additional $20.8 million in cash contingent on the achievement of certain employment conditions by several key employees of L2, which will be recognized as compensation expense over approximately three years. The Company recorded $124.7 million of goodwill and amortizable intangible assets for L2 and $9.5 million of other assets on a net basis. The operating results and the related goodwill are being reported as part of the Company's Research segment and goodwill resulting from the acquisition will not be deductible for tax purposes. The allocation of the purchase price is preliminary with respect to the valuation of finite-lived intangible assets, which the Company expects to complete in the second quarter of 2017. The Company believes the recorded goodwill is supported by the anticipated revenue synergies resulting from the acquisition. The Company's financial statements include the operating results of L2 beginning on its acquisition date, which were not material to either the Company's consolidated operating results or segment results for the first quarter of 2017. Had the Company acquired this business in prior periods, the impact to the Company's operating results for prior periods would not have been material, and as a result pro forma financial information for prior periods has not been presented.

Earnings per Share

Earnings per Share	3 Months Ended
	Mar. 31, 2017
Earnings Per Share [Abstract]
Earnings per Share	Earnings per Share The following table sets forth the calculations of basic and diluted earnings per share (in thousands, except per share data): Three Months Ended March 31, 2017 2016 Numerator: Net income used for calculating basic and diluted earnings per common share $ 36,433 $ 44,987 Denominator: Weighted average number of common shares used in the calculation of basic earnings per share 82,835 82,451 Common stock equivalents associated with stock-based compensation plans (1) 1,260 1,013 Shares used in the calculation of diluted earnings per share 84,095 83,464 Basic earnings per share $ 0.44 $ 0.55 Diluted earnings per share $ 0.43 $ 0.54 (1) Certain common stock equivalents were not included in the computation of diluted earnings per share because the effect would have been anti-dilutive. These common share equivalents totaled less than 0.4 million in each of the periods presented.

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	Stock-Based Compensation The Company grants stock-based compensation awards as an incentive for employees and directors to contribute to the Company’s long-term success. The Company currently awards stock-settled stock appreciation rights, service-based and performance-based restricted stock units, and common stock equivalents. At March 31, 2017 , the Company had a total of 5.5 million shares of its common stock, par value $.0005 per share (the “Common Stock”), available for stock-based compensation awards under its 2014 Long-Term Incentive Plan. The Company accounts for stock-based compensation awards in accordance with FASB ASC Topics 505 and 718, as interpreted by SEC Staff Accounting Bulletins No. 107 (“SAB No. 107”) and No. 110 (“SAB No. 110”). Stock-based compensation expense is based on the fair value of the award on the date of grant, which is then recognized as expense over the related service period. The service period is the period over which the related service is performed, which is generally the same as the vesting period. Currently, the Company issues treasury shares upon the exercise, release or settlement of stock-based compensation awards. Determining the appropriate fair value model and calculating the fair value of stock-based compensation awards requires the input of certain complex and subjective assumptions, including the expected life of the stock-based compensation awards and the Common Stock price volatility. In addition, determining the appropriate amount of associated periodic expense requires management to estimate the likelihood of the achievement of certain performance targets. The assumptions used in calculating the fair value of stock-based compensation awards and the associated periodic expense represent management’s best estimates, which involve inherent uncertainties and the application of judgment. As a result, if factors change and the Company deems it necessary in the future to modify the assumptions it made or to use different assumptions, or if the quantity and nature of the Company’s stock-based compensation awards changes, then the amount of expense may need to be adjusted and future stock-based compensation expense could be materially different from what has been recorded in the current period. Stock-Based Compensation Expense The Company recognized the following amounts of stock-based compensation expense by award type and expense category in the periods indicated (in millions): Three Months Ended March 31, Award type: 2017 2016 Stock appreciation rights $ 2.8 $ 1.7 Common stock equivalents 0.2 0.2 Restricted stock units 19.6 13.6 Total (1) $ 22.6 $ 15.5 Three Months Ended March 31, Amount recorded in: 2017 2016 Cost of services and product development $ 9.3 $ 7.6 Selling, general and administrative 13.3 7.9 Total (1) $ 22.6 $ 15.5 (1) Includes charges of $14.5 million and $10.3 million for the three months ended March 31, 2017 and 2016 , respectively, for awards to retirement-eligible employees since these awards vest on an accelerated basis. As of March 31, 2017 , the Company had $ 83.0 million of total unrecognized stock-based compensation cost, which is expected to be expensed over the remaining weighted-average service period of approximately 2.8 years. Stock-Based Compensation Awards The following disclosures provide information regarding the Company’s stock-based compensation awards, all of which are classified as equity awards in accordance with FASB ASC Topic 505: Stock Appreciation Rights Stock-settled stock appreciation rights (SARs) permit the holder to participate in the appreciation of the Common Stock. SARs are settled in shares of Common Stock by the employee once the applicable vesting criteria have been met. SARs vest ratably over a four -year service period and expire seven years from the grant date. The fair value of SARs awards is recognized as compensation expense on a straight-line basis over four years . SARs have only been awarded to the Company’s executive officers. When SARs are exercised, the number of shares of Common Stock issued is calculated as follows: (1) the total proceeds from the SARs exercise (calculated as the closing price of the Common Stock on the date of exercise less the exercise price of the SARs, multiplied by the number of SARs exercised) is divided by (2) the closing price of the Common Stock as reported on the New York Stock Exchange on the exercise date. The Company withholds a portion of the shares of Common Stock issued upon exercise to satisfy statutory tax withholding requirements. SARs recipients do not have any stockholder rights until after actual shares of Common Stock are issued in respect of the award, which is subject to the prior satisfaction of the vesting and other criteria relating to such grants. The following table summarizes changes in SARs outstanding during the three months ended March 31, 2017 : Stock Appreciation Rights (SARS) (in millions) Per Share Weighted- Average Exercise Price Per Share Weighted- Average Grant Date Fair Value Weighted Average Remaining Contractual Term (Years) Outstanding at December 31, 2016 1.3 $ 66.22 $ 15.77 4.40 Granted 0.3 99.07 22.02 6.85 Exercised — — — n/a Outstanding at March 31, 2017 (1), (2) 1.6 $ 73.16 $ 17.02 4.78 Vested and exercisable at March 31, 2017 (2) 0.8 $ 60.70 $ 15.36 3.67 na=not applicable. (1) As of March 31, 2017 , 0.8 million of the SARs outstanding were unvested. The Company expects that substantially all of these unvested awards will vest in future periods. (2) The total SARs outstanding as of March 31, 2017 had an intrinsic value of $54.2 million . SARs vested and exercisable had an intrinsic value of $36.4 million . The fair value of the SARs is determined on the date of grant using the Black-Scholes-Merton valuation model with the following weighted-average assumptions: Three Months Ended March 31, 2017 2016 Expected dividend yield (1) — % — % Expected stock price volatility (2) 22 % 22 % Risk-free interest rate (3) 1.8 % 1.1 % Expected life in years (4) 4.5 4.4 (1) The dividend yield assumption is based on the history and expectation of the Company’s dividend payouts. Historically, the Company has not paid cash dividends on its Common Stock. (2) The determination of expected stock price volatility was based on both historical Common Stock prices and implied volatility from publicly traded options in the Common Stock. (3) The risk-free interest rate is based on the yield of a U.S. Treasury security with a maturity similar to the expected life of the award. (4) The expected life represents the Company’s weighted-average estimate of the period of time the SARs are expected to be outstanding (that is, period between the service inception date and the expected exercise date). Restricted Stock Units Restricted stock units (RSUs) give the awardee the right to receive shares of Common Stock when the vesting conditions are met and the restrictions lapse, and each RSU that vests entitles the awardee to one common share. RSU awardees do not have any of the rights of a Gartner stockholder, including voting rights and the right to receive dividends and distributions, until the shares are released. The fair value of RSUs is determined on the date of grant based on the closing price of the Common Stock as reported by the New York Stock Exchange on that date. Service-based RSUs vest ratably over four years and are expensed on a straight-line basis over four years. Performance-based RSUs are subject to the satisfaction of both performance and service conditions, vest ratably over four years , and are expensed on an accelerated basis. The following table summarizes the changes in RSUs outstanding during the three months ended March 31, 2017 : Restricted Stock Units (RSUs) (in millions) Per Share Weighted Average Grant Date Fair Value Outstanding at December 31, 2016 1.3 $ 73.19 Granted (1) 0.5 99.14 Vested and released (0.5 ) 68.11 Forfeited — 81.85 Outstanding at March 31, 2017 (2), (3) 1.3 $ 84.40 (1) The 0.5 million RSUs granted consisted of 0.2 million performance-based RSUs awarded to executives and 0.3 million service-based RSUs awarded to non-executive employees. The 0.2 million of performance-based RSUs represents the target amount of the grant for the year, which is tied to an increase in the Company's total contract value for 2017. The final number of performance-based RSUs that will ultimately be awarded for 2017 ranges from 0% to 200% of the target amount, with the final number dependent on the actual increase in total contract value for 2017 as measured on December 31, 2017. If the specified minimum level of achievement is not met, the performance-based RSUs will be forfeited in their entirety, and any compensation expense previously recorded will be reversed. (2) The Company expects that substantially all of the outstanding awards will vest in future periods. (3) The weighted-average remaining contractual term of the outstanding RSUs is approximately 1.8 years. Common Stock Equivalents Common stock equivalents (CSEs) are convertible into Common Stock and each CSE entitles the holder to one common share. Members of our Board of Directors receive directors’ fees payable in CSEs unless they opt to receive up to 50% of the fees in cash. Generally, the CSEs have no defined term and are converted into common shares when service as a director terminates unless the director has elected an accelerated release. The fair value of the CSEs awarded is determined on the date of grant based on the closing price of the Common Stock as reported by the New York Stock Exchange on that date. CSEs vest immediately and as a result are recorded as expense on the date of grant. The following table summarizes the changes in CSEs outstanding during the three months ended March 31, 2017 : Common Stock Equivalents (CSEs) Per Share Weighted Average Grant Date Fair Value Outstanding at December 31, 2016 107,338 $ 20.74 Granted 1,592 108.95 Converted to common shares upon grant (1,161 ) 108.95 Outstanding at March 31, 2017 107,769 $ 21.09 Employee Stock Purchase Plan The Company has an employee stock purchase plan (the “ESP Plan”) under which eligible employees are permitted to purchase Common Stock through payroll deductions, which may not exceed 10% of an employee’s compensation (or $23,750 in any calendar year), at a price equal to 95% of the closing price of the Common Stock as reported by the New York Stock Exchange at the end of each offering period. At March 31, 2017 , the Company had 0.9 million shares available for purchase under the ESP Plan. The ESP Plan is considered non-compensatory under FASB ASC Topic 718, and as a result the Company does not record stock-based compensation expense for employee share purchases. The Company received $3.0 million and $2.6 million in cash from purchases under the ESP Plan during the three months ended March 31, 2017 and 2016 , respectively.

Segment Information

Segment Information	3 Months Ended
	Mar. 31, 2017
Segment Reporting [Abstract]
Segment Information	Segment Information The Company manages its business through three reportable segments: Research, Consulting and Events. Research consists primarily of subscription-based research products, access to research inquiry, peer networking services, and membership programs. Consulting consists primarily of consulting, measurement engagements, and strategic advisory services. Events consists of various symposia, conferences, and exhibitions. The Company evaluates segment performance and allocates resources based on gross contribution margin. Gross contribution, as presented in the table below, is defined as operating income excluding certain Cost of services and product development expenses, Selling, general and administrative expenses, Depreciation, Amortization of intangibles, and Acquisition and integration charges. Certain bonus and fringe benefit costs included in consolidated Cost of services and product development are not allocated to segment expense. The accounting policies used by the reportable segments are the same as those used by the Company. There are no intersegment revenues. The Company does not identify or allocate assets, including capital expenditures, by reportable segment. Accordingly, assets are not reported by segment because the information is not available by segment and is not reviewed in the evaluation of segment performance or in making decisions in the allocation of resources. The following tables present operating information about the Company’s reportable segments for the periods indicated (in thousands): Three Months Ended March 31, 2017 Research Consulting Events Consolidated Revenues $ 504,652 $ 85,248 $ 35,269 $ 625,169 Gross contribution 346,708 28,342 13,567 388,617 Corporate and other expenses (335,103 ) Operating income $ 53,514 Three Months Ended March 31, 2016 Research Consulting Events Consolidated Revenues $ 440,271 $ 84,940 $ 32,055 $ 557,266 Gross contribution 308,186 29,378 12,983 350,547 Corporate and other expenses (286,118 ) Operating income $ 64,429 The following table provides a reconciliation of total segment gross contribution to net income for the periods indicated (in thousands): Three Months Ended March 31, 2017 2016 Total segment gross contribution $ 388,617 $ 350,547 Costs and expenses: Cost of services and product development - unallocated (1) 1,057 5,322 Selling, general and administrative 304,244 257,411 Depreciation and amortization 16,530 15,017 Acquisition and integration charges 13,272 8,368 Operating income 53,514 64,429 Interest expense and other, net 5,017 4,122 Provision for income taxes 12,064 15,320 Net income $ 36,433 $ 44,987 (1) The unallocated amounts consist of certain bonus and related fringe costs recorded in Consolidated cost of services and product development expense that are not allocated to segment expense. The Company's policy is to only allocate bonus and related fringe charges to segments for up to 100% of the segment employee's target bonus. Amounts above 100% are absorbed by corporate.

Goodwill and Intangible Assets

Goodwill and Intangible Assets	3 Months Ended
	Mar. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	Goodwill and Intangible Assets Goodwill Goodwill represents the excess of the purchase price of acquired businesses over the estimated fair values of the tangible and identifiable intangible net assets acquired. The evaluation of the recoverability of goodwill is 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. 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. In connection with its most recent annual impairment test of goodwill performed during the quarter ended September 30, 2016, the Company utilized the qualitative approach in assessing the fair values of its reporting units relative to their respective carrying values, which indicated no impairment of recorded goodwill. The following table presents changes to the carrying amount of goodwill by reportable segment during the three months ended March 31, 2017 (in thousands): Research Consulting Events Total Balance, December 31, 2016 (1) $ 595,450 $ 96,480 $ 46,523 $ 738,453 Additions due to acquisitions (2) 114,222 — — 114,222 Foreign currency translation adjustments 2,376 197 82 2,655 Balance, March 31, 2017 $ 712,048 $ 96,677 $ 46,605 $ 855,330 (1) The Company does not have any accumulated goodwill impairment losses. (2) The addition to goodwill was due to the acquisition of L2 in March 2017. Finite-Lived Intangible Assets The following tables present reconciliations of the carrying amounts of the Company's finite-lived intangible assets as of the dates indicated (in thousands): March 31, 2017 Trade Names Customer Relationships Content Software Non-Compete Total Gross cost $ 4,337 $ 63,369 $ 3,728 $ 16,025 $ 29,308 $ 116,767 Additions due to acquisition (1) 500 9,000 — 1,000 — 10,500 Foreign currency translation impact 20 190 37 42 25 314 Gross cost 4,857 72,559 3,765 17,067 29,333 127,581 Accumulated amortization (2), (3) (2,046 ) (19,469 ) (2,521 ) (10,266 ) (12,070 ) (46,372 ) Balance, March 31, 2017 $ 2,811 $ 53,090 $ 1,244 $ 6,801 $ 17,263 $ 81,209 December 31, 2016 Trade Names Customer Relationships Content Software Non-Compete Total Gross cost $ 4,337 $ 63,369 $ 3,728 $ 16,025 $ 29,308 $ 116,767 Accumulated amortization (2), (3) (1,737 ) (16,744 ) (2,033 ) (8,904 ) (10,548 ) (39,966 ) Balance, December 31, 2016 $ 2,600 $ 46,625 $ 1,695 $ 7,121 $ 18,760 $ 76,801 (1) The additions are due to the acquisition of L2 in March 2017. (2) Intangible assets are amortized against earnings over the following periods: Trade names— 2 to 4 years ; Customer relationships— 4 to 8 years ; Content— 1.5 to 2 years ; Software— 3 years ; Non-compete— 3 to 5 years . (3) Aggregate amortization expense related to intangible assets was $6.3 million and $6.2 million for the three months ended March 31, 2017 and 2016 , respectively. The estimated future amortization expense by year from finite-lived intangibles will be as follows (in thousands): 2017 (remaining nine months) $ 18,508 2018 21,836 2019 16,624 2020 14,116 2021 6,533 Thereafter 3,592 $ 81,209

Debt

Debt	3 Months Ended
	Mar. 31, 2017
Debt Disclosure [Abstract]
Debt	Debt 2016 Credit Agreement The Company entered into the 2016 Credit Agreement on June 17, 2016, which provided for a $600.0 million Term loan A facility and a $1.2 billion revolving credit facility. As of March 31, 2017, the Company had $585.0 million outstanding under the Term loan A facility and $270.0 million of outstanding revolver loans under the 2016 Credit Agreement. The 2016 Credit Agreement contains certain customary restrictive loan covenants, including, among others, financial covenants that apply a maximum leverage ratio and a minimum interest expense coverage ratio, and covenants limiting Gartner’s ability to incur indebtedness, grant liens, make acquisitions, merge, dispose of assets, pay dividends, repurchase stock, make investments and enter into certain transactions with affiliates. The Company was in full compliance with the loan covenants as of March 31, 2017. As discussed below, the 2016 Credit Agreement was amended twice in the first quarter of 2017 to permit the acquisition of CEB and the incurrence of additional debt, as well as to extend the maturity date of the Term loan A facility and revolving credit facility through March 20, 2022 and to revise the interest rate and repayment schedule. On January 20, 2017, the Company entered into a First Amendment of the 2016 Credit Agreement, which was entered into to permit the acquisition of CEB and the incurrence of additional debt to finance, in part, the acquisition and repay certain debt of CEB, and to modify certain covenants. On March 20, 2017, the Company entered into a Second Amendment of the 2016 Credit Agreement. The Second Amendment was also entered into in connection with the acquisition of CEB and was executed primarily to extend the maturity date of the Term loan A facility and revolving credit facility through March 20, 2022 and to revise the interest rate and amortization schedule. The Term loan A facility will be repaid in 16 consecutive quarterly installments commencing on June 30, 2017, plus a final payment to be made on March 20, 2022. The revolving credit facility may be borrowed, repaid, and re-borrowed through March 20, 2022, at which time all amounts must be repaid. Loans will bear interest at a rate equal to, at the Company's option, either: (i) the greatest of: (x) the Administrative Agent’s prime rate; (y) the average rate on Federal Reserve Board of New York rate plus 1/2 of 1% ; and (z) the eurodollar rate (adjusted for statutory reserves) plus 1% , in each case plus a margin equal to between 0.125% and 1.50% depending on Gartner’s consolidated leverage ratio as of the end of the four consecutive fiscal quarters most recently ended, or (ii) the eurodollar rate (adjusted for statutory reserves) plus a margin equal to between 1.125% and 2.50% , depending on Gartner’s leverage ratio as of the end of the four consecutive fiscal quarters most recently ended. $800.0 million Principal Amount Senior Notes On March 30, 2017 , in conjunction with the acquisition of CEB, the Company issued $800.0 million aggregate principal amount of 5.125% Senior Notes due 2025 (the “Senior Notes”). The Senior Notes were issued at an issue price of 100.00% and bear interest at a fixed rate of 5.125% per annum. Interest on the Senior Notes is payable on April 1 and October 1 of each year, beginning on October 1, 2017. The Senior Notes will mature on April 1, 2025. The Company may redeem some or all of the Senior Notes at any time on or after April 1, 2020 for cash at the redemption prices set forth in the Note Indenture, plus accrued and unpaid interest to, but not including, the redemption date. Prior to April 1, 2020, the Company may redeem up to 40% of the aggregate principal amount of the Senior Notes with the proceeds of certain equity offerings at a redemption price of 105.125% plus accrued and unpaid interest to, but not including, the redemption date. In addition, the Company may redeem some or all of the Senior Notes prior to April 1, 2020, at a redemption price of 100% of the principal amount of the Senior Notes plus accrued and unpaid interest to, but not including, the redemption date, plus a “make-whole” premium. If the Company experiences specific kinds of change of control, it will be required to offer to purchase the Senior Notes at a price equal to 101% of the principal amount thereof plus accrued and unpaid interest. The Senior Notes are the Company’s general unsecured senior obligations, and are effectively subordinated to all of the Company’s existing and future secured indebtedness to the extent of the value of the collateral securing such indebtedness, structurally subordinated to all existing and future indebtedness and other liabilities of the Company’s non-guarantor subsidiaries, equal in right of payment to all of the Company’s and Company’s guarantor subsidiaries’ existing and future senior indebtedness and senior in right of payment to all of the Company’s future subordinated indebtedness, if any. Acquisition of CEB On April 5, 2017, the Company completed the CEB acquisition and borrowed in total approximately $2.8 billion to complete the transaction, including the Senior Notes discussed above. The Company also entered into a third amendment to the 2016 Credit Agreement in conjunction with and on the same date as the CEB acquisition. The Company's total indebtedness after the close of the CEB acquisition was approximately $3.6 billion . Note 14 — Subsequent Events provides additional information regarding the CEB acquisition and the third amendment to the 2016 Credit Agreement. Outstanding Borrowings March 31, 2017 The following table summarizes the Company’s total outstanding borrowings (in thousands): Balance Balance March 31, December 31, Description: 2017 2016 2016 Credit Agreement - Term loan A facility (1) $ 585,000 $ 585,000 2016 Credit Agreement - Revolving credit facility (1), (2) 270,000 115,000 Senior Notes, $800.0 million principal amount (3) 800,000 — Other (4) 2,500 2,500 Subtotal (5) 1,657,500 702,500 Less: deferred financing fees (6) (28,803 ) (8,109 ) Net carrying amount (7) $ 1,628,697 $ 694,391 (1) The contractual annualized interest rate as of March 31, 2017 on both the Term loan A facility and revolving credit facility was 2.23% , which consisted of a floating eurodollar base rate of 0.98% plus a margin of 1.25% . However, the Company has interest rate swap contracts, accounted for as cash flow hedges, which effectively convert the floating eurodollar base rates to a fixed base rate. (2) The Company had $927.0 million of available borrowing capacity on the revolver (not including the expansion feature) as of March 31, 2017 . (3) Consists of $800.0 million principal amount of Senior Notes outstanding, which the Company issued on March 30, 2017 to finance in part the CEB acquisition. The Senior Notes pay a fixed rate of 5.125% and have an eight year maturity. (4) Consists of a $2.5 million State of Connecticut economic development loan with a 3.00% fixed rate of interest. The loan was originated in 2012 and has a 10 year maturity. Principal payments are deferred for the first five years and the loan may be repaid at any point by the Company without penalty. (5) The average annual effective rate on the Company's total debt outstanding for the three months ended March 31, 2017 , including the effect of its interest rate swaps discussed below, was approximately 2.89% . (6) The deferred financing fees are being amortized to Interest Expense, net over the term of the respective debt obligation. (7) On April 5, 2017, the Company completed the acquisition of CEB. The Company had approximately $3.6 billion in total debt outstanding after the close of the acquisition. Note 14 — Subsequent Events provides additional information regarding the CEB acquisition and the additional amounts borrowed. Interest Rate Swaps The Company has fixed-for-floating interest rate swap contracts which it designates as accounting hedges of the forecasted interest payments on the Company’s variable rate borrowings. The Company pays base fixed rates on the swaps and in return receives a floating eurodollar base rate on 30 day notional borrowings. The Company accounts for the interest rate swaps as cash flow hedges in accordance with FASB ASC Topic 815. Since the swaps hedge forecasted interest payments, changes in the fair value of the swaps are recorded in accumulated other comprehensive income (loss), a component of equity, as long as the swaps continue to be highly effective hedges of the designated interest rate risk. Any ineffective portion of change in the fair value of the hedges is recorded in earnings. All of the swaps were highly effective hedges of the forecasted interest payments as of March 31, 2017 . The interest rate swaps had a total negative fair value (liability) to the Company of $6.6 million at March 31, 2017 , which is deferred and recorded in Accumulated other comprehensive loss, net of tax effect.

Equity

Equity	3 Months Ended
	Mar. 31, 2017
Stockholders' Equity Note [Abstract]
Equity	Equity Share Repurchase Program The Company has a $1.2 billion board approved authorization to repurchase the Company's common stock, of which $1.1 billion remained available as of March 31, 2017. The Company may repurchase its common stock from time to time in amounts and at prices the Company deems appropriate, subject to the availability of stock, prevailing market conditions, the trading price of the stock, the Company’s financial performance and other conditions. Repurchases may be made through open market purchases, private transactions or other transactions and will be funded from cash on hand and borrowings under the Company’s credit arrangement. The Company’s recent share repurchase activity is presented in the following table: Three Months Ended March 31, 2017 2016 Number of shares repurchased (1) 218,752 466,823 Cash paid for repurchased shares (in thousands) (2) $ 21,978 $ 45,487 (1) The average purchase price for repurchased shares was $100.47 and $82.02 for the three months ended March 31, 2017 and 2016, respectively. (2) The cash paid for the three months ended March 31, 2016 included $7.2 million for share repurchases that were executed in late December 2015 and were settled in early January 2016. Acquisition of CEB On April 5, 2017, the Company completed the CEB acquisition and issued 7.4 million common shares. Note 14 — Subsequent Events provides additional information regarding the CEB acquisition. Accumulated Other Comprehensive (Loss) Income ("AOCL/I") The following tables disclose information about changes in AOCL/I by component and the related amounts reclassified out of AOCL/I to income during the periods indicated (net of tax, in thousands) (1): For the three months ended March 31, 2017 : Interest Rate Swaps Defined Benefit Pension Plans Foreign Currency Translation Adjustments Total Balance - December 31, 2016 $ (1,409 ) $ (5,797 ) $ (42,477 ) $ (49,683 ) Changes during the period: Change in AOCL/I before reclassifications to income (3,393 ) — 4,371 978 Reclassifications from AOCL/I to income during the period (2), (3) 825 48 — 873 Other comprehensive (loss) income for the period (2,568 ) 48 4,371 1,851 Balance – March 31, 2017 $ (3,977 ) $ (5,749 ) $ (38,106 ) $ (47,832 ) For the three months ended March 31, 2016 : Interest Rate Defined Foreign Total Balance – December 31, 2015 $ (3,079 ) $ (4,832 ) $ (36,491 ) $ (44,402 ) Changes during the period: Change in AOCL/I before reclassifications to income (8,357 ) — 2,068 (6,289 ) Reclassifications from AOCL/I to income during the period (2), (3) 1,224 37 — 1,261 Other comprehensive (loss) income for the period (7,133 ) 37 2,068 (5,028 ) Balance – March 31, 2016 $ (10,212 ) $ (4,795 ) $ (34,423 ) $ (49,430 ) (1) Amounts in parentheses represent debits (deferred losses). (2) The reclassifications related to interest rate swaps (cash flow hedges) were recorded in Interest expense, net of tax effect. See Note 10 – Derivatives and Hedging for information regarding the hedges. (3) The reclassifications related to defined benefit pension plans were recorded in Selling, general and administrative expense, net of tax effect. See Note 12 – Employee Benefits for information regarding the Company’s defined benefit pension plans.

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The provision for income taxes was $12.1 million for the three months ended March 31, 2017 compared to $15.3 million in the three months ended March 31, 2016 . The effective income tax rate was 24.9% for the three months ended March 31, 2017 and 25.4% for the same period in 2016 . The quarter-over-quarter decrease in the effective income tax rate was primarily attributable to an increase in stock-based compensation benefits partially offset by an increase in unrecognized tax benefits. As of March 31, 2017 and December 31, 2016 , the Company had gross unrecognized tax benefits of $42.6 million and $37.1 million , respectively. It is reasonably possible that gross unrecognized tax benefits will decrease by approximately $3.8 million within the next 12 months, due to the anticipated closure of audits and the expiration of certain statutes of limitation. In July 2015, the United States Tax Court (the “Court”) issued an opinion relating to the treatment of stock-based compensation expense in an inter-company cost-sharing arrangement. In its opinion, the Court held that affiliated companies may exclude stock-based compensation expense from their cost-sharing arrangement. The Internal Revenue Service is appealing the decision. Because of uncertainty related to the final resolution of this litigation and the recognition of potential benefits to the Company, the Company has not recorded any financial statement benefit associated with this decision. The Company will monitor developments related to this case and the potential impact of those developments on the Company’s consolidated financial statements.

Derivatives and Hedging

Derivatives and Hedging	3 Months Ended
	Mar. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivatives and Hedging	Derivatives and Hedging The Company enters into a limited number of derivative contracts to mitigate the cash flow risk associated with changes in interest rates on variable rate debt and changes in foreign exchange rates on forecasted foreign currency transactions. The Company accounts for its outstanding derivative contracts in accordance with FASB ASC Topic 815, which requires all derivatives, including derivatives designated as accounting hedges, to be recorded on the balance sheet and recognized at fair value. The following tables provide information regarding the Company’s outstanding derivatives contracts as of the dates indicated (in thousands, except for number of outstanding contracts): March 31, 2017 Derivative Contract Type Number of Outstanding Contracts Notional Amounts Fair Value Asset (Liability), Net (3) Balance Sheet Line Item Unrealized Loss Recorded in OCI Interest rate swaps (1) 5 $ 1,400,000 $ (6,630 ) Other liabilities (3,977 ) Foreign currency forwards (2) 23 45,425 (159 ) Accrued liabilities — Total 28 $ 1,445,425 $ (6,789 ) (3,977 ) December 31, 2016 Derivative Contract Type Number of Outstanding Contracts Notional Amounts Fair Value Asset (Liability), Net (3) Balance Sheet Line Item Unrealized Loss Recorded in OCI Interest rate swaps (1) 3 $ 700,000 $ (2,349 ) Other liabilities $ (1,409 ) Foreign currency forwards (2) 84 86,946 (320 ) Accrued liabilities — Total 87 $ 786,946 $ (2,669 ) $ (1,409 ) (1) The swaps have been designated and are accounted for as cash flow hedges of the forecasted interest payments on borrowings. As a result, changes in fair value of the swaps are deferred and are recorded in AOCL/I, net of tax effect (see Note 7 — Debt for additional information). (2) The Company has foreign exchange transaction risk since it typically enters into transactions in the normal course of business that are denominated in foreign currencies that differ from the local functional currency. The Company enters into short-term foreign currency forward exchange contracts to mitigate the cash flow risk associated with changes in foreign currency rates on forecasted foreign currency transactions. These contracts are accounted for at fair value with realized and unrealized gains and losses recognized in Other expense, net since the Company does not designate these contracts as hedges for accounting purposes. All of the contracts outstanding at March 31, 2017 matured by the end of April 2017. (3) See Note 11 — Fair Value Disclosures for the determination of the fair value of these instruments. At March 31, 2017 , all of the Company’s derivative counterparties were investment grade financial institutions. The Company did not have any collateral arrangements with its derivative counterparties, and none of the derivative contracts contained credit-risk related contingent features. The following table provides information regarding amounts recognized in the Condensed Consolidated Statements of Operations for derivative contracts for the periods indicated (in thousands): Three Months Ended March 31, Amount recorded in: 2017 2016 Interest expense, net (1) $ 1,375 $ 1,987 Other expense, net (2) 219 335 Total expense, net $ 1,594 $ 2,322 (1) Consists of interest expense from interest rate swap contracts. (2) Consists of realized and unrealized gains and losses on foreign currency forward contracts.

Fair Value Disclosures

Fair Value Disclosures	3 Months Ended
	Mar. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value Disclosures	Fair Value Disclosures The Company’s financial instruments include cash equivalents, fees receivable from customers, accounts payable, and accruals which are normally short-term in nature. The Company believes the carrying amounts of these financial instruments reasonably approximate their fair value due to their short-term nature. The Company’s financial instruments also include its outstanding borrowings. The Company believes the carrying amount of the outstanding borrowings reasonably approximates their fair value since the rate of interest on these borrowings reflect current market rates of interest for similar instruments with comparable maturities. The Company enters into a limited number of derivatives transactions but does not enter into repurchase agreements, securities lending transactions, or master netting arrangements. Receivables or payables that result from derivatives transactions are recorded gross in the Condensed Consolidated Balance Sheets. FASB ASC Topic 820 provides a framework for the measurement of fair value and a valuation hierarchy based upon the transparency of inputs used in the valuation of assets and liabilities. Classification within the hierarchy is based upon the lowest level of input that is significant to the resulting fair value measurement. The valuation hierarchy contains three levels. Level 1 measurements consist of quoted prices in active markets for identical assets or liabilities. Level 2 measurements include significant other observable inputs such as quoted prices for similar assets or liabilities in active markets; identical assets or liabilities in inactive markets; observable inputs such as interest rates and yield curves; and other market-corroborated inputs. Level 3 measurements include significant unobservable inputs, such as internally-created valuation models. The Company does not currently utilize Level 3 valuation inputs to remeasure any of its assets or liabilities. However, level 3 inputs may be used by the Company in its required annual impairment review of recorded goodwill. Information regarding the periodic assessment of the Company’s goodwill is included in Note 6 — Goodwill and Intangible Assets. The Company does not typically transfer assets or liabilities between different levels of the fair value hierarchy. The Company’s assets and liabilities that are remeasured to fair value are presented in the following table (in thousands): Fair Value Fair Value Description: March 31, December 31, Assets: Values based on Level 1 inputs: Deferred compensation plan assets (1) $ 11,211 $ 10,247 Total Level 1 inputs 11,211 10,247 Values based on Level 2 inputs: Deferred compensation plan assets (1) 29,174 27,847 Foreign currency forward contracts (2) 39 165 Total Level 2 inputs 29,213 28,012 Total Assets $ 40,424 $ 38,259 Liabilities: Values based on Level 2 inputs: Deferred compensation plan liabilities (1) $ 45,595 $ 43,075 Foreign currency forward contracts (2) 198 485 Interest rate swap contracts (3) 6,630 2,349 Total Level 2 inputs 52,423 45,909 Total Liabilities $ 52,423 $ 45,909 (1) The Company has a deferred compensation plan for the benefit of certain highly compensated officers, managers and other key employees. The assets consist of investments in money market and mutual funds, and company-owned life insurance contracts, all of which are valued based on Level 1 or Level 2 valuation inputs. The related deferred compensation plan liabilities are recorded at fair value, or the estimated amount needed to settle the liability, which the Company considers to be a Level 2 input. (2) The Company enters into foreign currency forward exchange contracts to hedge the effects of adverse fluctuations in foreign currency exchange rates. Valuation of the foreign currency forward contracts is based on observable foreign currency exchange rates in active markets, which the Company considers a Level 2 input. (3) The Company has interest rate swap contracts which hedge the risk of variability from interest payments on its borrowings (see Note 7 — Debt). The fair value of the swaps is based on mark-to-market valuations prepared by a third-party broker. The valuations are based on observable interest rates from recently executed market transactions and other observable market data, which the Company considers Level 2 inputs. The Company independently corroborates the reasonableness of the valuations prepared by the third-party broker through the use of an electronic quotation service.

Employee Benefits

Employee Benefits	3 Months Ended
	Mar. 31, 2017
Compensation and Retirement Disclosure [Abstract]
Employee Benefits	Employee Benefits Defined-Benefit Pension Plans The Company has defined-benefit pension plans in several of its international locations. Benefits paid under these plans are based on years of service and level of employee compensation. The Company’s defined-benefit pension plans are accounted for in accordance with FASB ASC Topics 715 and 960. Net periodic pension expense was $0.7 million for both the three months ended March 31, 2017 and March 31, 2016.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Contingencies The Company is involved in legal proceedings and litigation arising in the ordinary course of business. We believe that the potential liability, if any, in excess of amounts already accrued from all proceedings, claims and litigation will not have a material effect on our financial position, cash flows, or results of operations when resolved in a future period. The Company has various agreements that may obligate us to indemnify the other party with respect to certain matters. Generally, these indemnification clauses are included in contracts arising in the normal course of business under which we customarily agree to hold the other party harmless against losses arising from a breach of representations related to such matters as title to assets sold and licensed or certain intellectual property rights. It is not possible to predict the maximum potential amount of future payments under these indemnification agreements due to the conditional nature of the Company’s obligations and the unique facts of each particular agreement. Historically, payments made by us under these agreements have not been material. As of March 31, 2017 , the Company did not have any material payment obligations under any such indemnification agreements.

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2017
Subsequent Events [Abstract]
Subsequent Events	On April 5, 2017, the Company completed the previously announced acquisition of CEB. Gartner acquired all of the outstanding shares of CEB in a cash and stock transaction with a total enterprise value of approximately $3.5 billion gross. Gartner paid $2.7 billion in cash at close and issued 7.4 million of its common shares. The Company borrowed approximately $2.8 billion in conjunction with the acquisition, which included $800.0 million of principal amount Senior Notes (see Note 7 — Debt) issued on March 30, 2017; approximately $1.7 billion borrowed on April 5, 2017 under the 2016 Credit Agreement, which was amended for a third time on April 5, 2017; and $300.0 million borrowed under a 364 -day Bridge Credit Facility, entered into on April 5, 2017. The Company had $3.6 billion in total debt outstanding after the close of the acquisition. The third amendment to the 2016 Credit Agreement and the 364 -day Bridge Credit Facility, and the amounts borrowed under those borrowing arrangements in conjunction with the acquisition, are discussed in more detail below. Third Amendment to the 2016 Credit Agreement On April 5, 2017, in conjunction with the closing of the CEB acquisition, the Company entered into a third amendment to the 2016 Credit Agreement with its lenders (the "Incremental Amendment"). The Incremental Amendment increased the aggregate principal amount of the existing Term loan A facility by $900.0 million and added a new incremental Term loan B facility in an aggregate principal amount of $500.0 million . Immediately upon entry into the Incremental Amendment, the Company drew down $900.0 million under the increased Term loan A facility and $500.0 million under the new Term loan B facility and made an additional draw of $275.0 million on its existing revolving credit facility. Along with the funds raised through the issuance of the Senior Notes and the 364 -Bridge Credit Facility, the amounts drawn under the 2016 Credit Agreement were used to fund the cash paid for the CEB acquisition. The additional amount drawn under the Term loan A facility has the same maturity date and is subject to the same interest, repayment terms, amortization schedules, representations and warranties, affirmative and negative covenants and events of default as the amounts outstanding under such facility prior to entry by the Company into the Incremental Amendment. The Term loan B facility contains representations and warranties, affirmative and negative covenants and events of default that are the same as the Term loan A facility and revolving credit facility, except that a breach of financial maintenance covenants will not result in an event of default under the Term loan B facility unless the lenders under the revolving credit facility and Term loan A facility have accelerated the revolving loans and Term loan A loans and terminated their commitments thereunder. Additionally, the Term loan B facility includes mandatory prepayment requirements related to asset sales (subject to reinvestment), debt incurrence (other than permitted debt) and excess cash flow, subject to certain limitations described therein. Any voluntary prepayment of the Term loan B facility made in connection with a repricing transaction in the first six months following April 5, 2017 will be subject to a 1.00% prepayment premium. The Term loan B facility will mature on April 5, 2024 and amounts outstanding thereunder will bear interest at a rate per annum equal to, at the option of Gartner, (i) adjusted LIBOR plus 2.00% or (ii) an alternate base rate plus 1.00% . 364-day Bridge Credit Facility Also on April 5, 2017, and in connection with the closing of the CEB acquisition, the Company entered into a senior unsecured 364 -day Bridge Credit Facility in an aggregate principal amount of $300.0 million , which amount was immediately drawn by the Company to fund a portion of the costs associated with the acquisition. The 364 -day Bridge Credit Facility will mature on the 364 th day after the closing date of the acquisition. Amounts outstanding under the 364 -day Bridge Credit Facility will bear interest at a rate per annum equal to, at the option of the Company: (i) adjusted LIBOR plus 2.75% or (ii) an alternate base rate plus 1.75% , with the margins on both increasing by 0.25% 180 days after the closing date and an additional 0.25% each 90 days thereafter. The 364 -day Bridge Credit Facility contains representations and warranties, affirmative and negative covenants and events of default that are substantially the same as in the 2016 Credit Agreement. Additionally, the 364 -Day Bridge Credit Facility includes mandatory prepayment requirements related to the receipt by the Company of repatriated funds from its foreign subsidiaries, subject to certain exceptions and reduced by any taxes payable or reasonably estimated by the Company to be payable upon such repatriation and proceeds from certain debt and equity issuances.

Business and Basis of Present21

Business and Basis of Presentation (Policies)	3 Months Ended
	Mar. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of presentation	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, 2016 . 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, 2017 may not be indicative of the results of operations for the remainder of 2017 or beyond.
Principles of consolidation	Principles of consolidation . The accompanying interim condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany transactions and balances have been eliminated.
Use of estimates	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 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.
Adoption of new accounting standard	Impact of Stock-Based Compensation Accounting Rule Change . In the third quarter of 2016, the Company early adopted FASB Accounting Standards Update No. 2016-09, " Improvements to Employee Share-Based Payment Accounting" ("ASU No. 2016-09"), which changed the accounting for stock-based compensation awards. The accounting changes required by ASU No. 2016-09 were applied to the beginning of the Company's 2016 fiscal year, and as a result certain previously reported financial results for the three months ended March 31, 2016 were revised. These changes included a $4.8 million increase in net income, and a $0.06 increase in each of basic earnings per share and diluted earnings per share. In addition, our previously reported operating cash flow for the three months ended March 31, 2016 increased by $4.8 million . Adoption of new accounting standards. The Company did not adopt any new accounting standards in the first quarter of 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: Retirement Benefits 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 is effective for Gartner on January 1, 2018. We are currently evaluating the potential impact of ASU No. 2017-07 on the Company's consolidated financial statements. Defined Benefit Pension Plans Disclosure — In February 2017, the FASB issued ASU No. 2017-06, "Employee Benefit Plan Master Trust Reporting" ("ASU No. 2017-06"). ASU No. 2017-06 clarifies presentation requirements for a plan’s interest in certain trust arrangements as well as other changes. ASU No. 2017-06 is effective for Gartner on January 1, 2019. We are currently evaluating the potential impact of ASU No. 2017-06 on the Company's consolidated financial statements. Accounting for Partial Sales of Non-financial Asset s — 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 is effective for Gartner on January 1, 2018. We are currently evaluating the potential impact of ASU No. 2017-05 on the Company's consolidated financial statements. Simplifying the Test for 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 goodwill impairment test. ASU No. 2017-04 is effective for Gartner on January 1, 2020. We are currently evaluating the potential impact of ASU No. 2017-04 on the Company's consolidated financial statements. Business Combinations — In January 2017, the FASB issued ASU No. 2017-01, "Clarifying the Definition of a Business" ("ASU No. 2017-01"), which is effective for Gartner on January 1, 2018. ASU No. 2017-01 changes the GAAP definition of a business which can impact the accounting for asset purchases, acquisitions, goodwill impairment, and other assessments. We are currently evaluating the impact of ASU No. 2017-01 on the Company's consolidated financial statements. Statement of Cash Flows — 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 is effective for Gartner on January 1, 2018. We are currently evaluating the impact of ASU No. 2016-18 on the Company's consolidated financial statements. 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 is effective for Gartner on January 1, 2018. Current 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 will be immediately recognized upon the sale. We have completed an initial evaluation of the impact of ASU No. 2016-16 and believe it could have a material impact on our consolidated financial statements depending on the nature and size of future intra-entity transfers. 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 is effective for Gartner on January 1, 2018, but early adoption is permitted. We have completed an initial evaluation of the impact of ASU No. 2016-15 and we do not expect it will have a material impact on our 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. 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 impact of ASU No. 2016-02 on our 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 will be effective for Gartner on January 1, 2018. We have completed an initial evaluation of the impact of ASU No. 2016-01 and we do not expect it will have a material impact on our consolidated financial statements but may require additional disclosures. 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 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. The Company has completed an initial assessment of the impact of ASU No. 2014-09 on its existing revenue recognition policies and plans to adopt the rule on January 1, 2018 using the cumulative effect method of adoption. 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, which the Company is currently compiling. While the Company has not fully completed its assessment of the impact of ASU No. 2014-09, based on the analysis completed to date, the Company does not currently anticipate that the new rule will have a material impact on its 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.
Acquisitions	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.

Earnings per Share (Tables)

Earnings per Share (Tables)	3 Months Ended
	Mar. 31, 2017
Earnings Per Share [Abstract]
Schedule of earnings per share reconciliation	The following table sets forth the calculations of basic and diluted earnings per share (in thousands, except per share data): Three Months Ended March 31, 2017 2016 Numerator: Net income used for calculating basic and diluted earnings per common share $ 36,433 $ 44,987 Denominator: Weighted average number of common shares used in the calculation of basic earnings per share 82,835 82,451 Common stock equivalents associated with stock-based compensation plans (1) 1,260 1,013 Shares used in the calculation of diluted earnings per share 84,095 83,464 Basic earnings per share $ 0.44 $ 0.55 Diluted earnings per share $ 0.43 $ 0.54 (1) Certain common stock equivalents were not included in the computation of diluted earnings per share because the effect would have been anti-dilutive. These common share equivalents totaled less than 0.4 million in each of the periods presented.

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule of stock-based compensation expense by award type	The Company recognized the following amounts of stock-based compensation expense by award type and expense category in the periods indicated (in millions): Three Months Ended March 31, Award type: 2017 2016 Stock appreciation rights $ 2.8 $ 1.7 Common stock equivalents 0.2 0.2 Restricted stock units 19.6 13.6 Total (1) $ 22.6 $ 15.5
Schedule of stock-based compensation expense by expense category	Three Months Ended March 31, Amount recorded in: 2017 2016 Cost of services and product development $ 9.3 $ 7.6 Selling, general and administrative 13.3 7.9 Total (1) $ 22.6 $ 15.5 (1) Includes charges of $14.5 million and $10.3 million for the three months ended March 31, 2017 and 2016 , respectively, for awards to retirement-eligible employees since these awards vest on an accelerated basis.
Schedule of fair value assumptions of SARs	The fair value of the SARs is determined on the date of grant using the Black-Scholes-Merton valuation model with the following weighted-average assumptions: Three Months Ended March 31, 2017 2016 Expected dividend yield (1) — % — % Expected stock price volatility (2) 22 % 22 % Risk-free interest rate (3) 1.8 % 1.1 % Expected life in years (4) 4.5 4.4 (1) The dividend yield assumption is based on the history and expectation of the Company’s dividend payouts. Historically, the Company has not paid cash dividends on its Common Stock. (2) The determination of expected stock price volatility was based on both historical Common Stock prices and implied volatility from publicly traded options in the Common Stock. (3) The risk-free interest rate is based on the yield of a U.S. Treasury security with a maturity similar to the expected life of the award. (4) The expected life represents the Company’s weighted-average estimate of the period of time the SARs are expected to be outstanding (that is, period between the service inception date and the expected exercise date).
Stock appreciation rights (SARs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule of summary of the changes in SARS, RSUs, and CSEs outstanding	The following table summarizes changes in SARs outstanding during the three months ended March 31, 2017 : Stock Appreciation Rights (SARS) (in millions) Per Share Weighted- Average Exercise Price Per Share Weighted- Average Grant Date Fair Value Weighted Average Remaining Contractual Term (Years) Outstanding at December 31, 2016 1.3 $ 66.22 $ 15.77 4.40 Granted 0.3 99.07 22.02 6.85 Exercised — — — n/a Outstanding at March 31, 2017 (1), (2) 1.6 $ 73.16 $ 17.02 4.78 Vested and exercisable at March 31, 2017 (2) 0.8 $ 60.70 $ 15.36 3.67 na=not applicable. (1) As of March 31, 2017 , 0.8 million of the SARs outstanding were unvested. The Company expects that substantially all of these unvested awards will vest in future periods. (2) The total SARs outstanding as of March 31, 2017 had an intrinsic value of $54.2 million . SARs vested and exercisable had an intrinsic value of $36.4 million .
Restricted stock units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule of summary of the changes in SARS, RSUs, and CSEs outstanding	The following table summarizes the changes in RSUs outstanding during the three months ended March 31, 2017 : Restricted Stock Units (RSUs) (in millions) Per Share Weighted Average Grant Date Fair Value Outstanding at December 31, 2016 1.3 $ 73.19 Granted (1) 0.5 99.14 Vested and released (0.5 ) 68.11 Forfeited — 81.85 Outstanding at March 31, 2017 (2), (3) 1.3 $ 84.40 (1) The 0.5 million RSUs granted consisted of 0.2 million performance-based RSUs awarded to executives and 0.3 million service-based RSUs awarded to non-executive employees. The 0.2 million of performance-based RSUs represents the target amount of the grant for the year, which is tied to an increase in the Company's total contract value for 2017. The final number of performance-based RSUs that will ultimately be awarded for 2017 ranges from 0% to 200% of the target amount, with the final number dependent on the actual increase in total contract value for 2017 as measured on December 31, 2017. If the specified minimum level of achievement is not met, the performance-based RSUs will be forfeited in their entirety, and any compensation expense previously recorded will be reversed. (2) The Company expects that substantially all of the outstanding awards will vest in future periods. (3) The weighted-average remaining contractual term of the outstanding RSUs is approximately 1.8 years.
Common stock equivalents (CSEs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule of summary of the changes in SARS, RSUs, and CSEs outstanding	The following table summarizes the changes in CSEs outstanding during the three months ended March 31, 2017 : Common Stock Equivalents (CSEs) Per Share Weighted Average Grant Date Fair Value Outstanding at December 31, 2016 107,338 $ 20.74 Granted 1,592 108.95 Converted to common shares upon grant (1,161 ) 108.95 Outstanding at March 31, 2017 107,769 $ 21.09

Segment Information (Tables)

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2017
Segment Reporting [Abstract]
Schedule of segment reporting information, by segment	The following tables present operating information about the Company’s reportable segments for the periods indicated (in thousands): Three Months Ended March 31, 2017 Research Consulting Events Consolidated Revenues $ 504,652 $ 85,248 $ 35,269 $ 625,169 Gross contribution 346,708 28,342 13,567 388,617 Corporate and other expenses (335,103 ) Operating income $ 53,514 Three Months Ended March 31, 2016 Research Consulting Events Consolidated Revenues $ 440,271 $ 84,940 $ 32,055 $ 557,266 Gross contribution 308,186 29,378 12,983 350,547 Corporate and other expenses (286,118 ) Operating income $ 64,429
Schedule of reconciliation of segment gross contribution to net income	The following table provides a reconciliation of total segment gross contribution to net income for the periods indicated (in thousands): Three Months Ended March 31, 2017 2016 Total segment gross contribution $ 388,617 $ 350,547 Costs and expenses: Cost of services and product development - unallocated (1) 1,057 5,322 Selling, general and administrative 304,244 257,411 Depreciation and amortization 16,530 15,017 Acquisition and integration charges 13,272 8,368 Operating income 53,514 64,429 Interest expense and other, net 5,017 4,122 Provision for income taxes 12,064 15,320 Net income $ 36,433 $ 44,987 (1) The unallocated amounts consist of certain bonus and related fringe costs recorded in Consolidated cost of services and product development expense that are not allocated to segment expense. The Company's policy is to only allocate bonus and related fringe charges to segments for up to 100% of the segment employee's target bonus. Amounts above 100% are absorbed by corporate.

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	3 Months Ended
	Mar. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of changes to the carrying amount of goodwill by reporting unit	The following table presents changes to the carrying amount of goodwill by reportable segment during the three months ended March 31, 2017 (in thousands): Research Consulting Events Total Balance, December 31, 2016 (1) $ 595,450 $ 96,480 $ 46,523 $ 738,453 Additions due to acquisitions (2) 114,222 — — 114,222 Foreign currency translation adjustments 2,376 197 82 2,655 Balance, March 31, 2017 $ 712,048 $ 96,677 $ 46,605 $ 855,330 (1) The Company does not have any accumulated goodwill impairment losses. (2) The addition to goodwill was due to the acquisition of L2 in March 2017.
Schedule of amortizable intangible assets	The following tables present reconciliations of the carrying amounts of the Company's finite-lived intangible assets as of the dates indicated (in thousands): March 31, 2017 Trade Names Customer Relationships Content Software Non-Compete Total Gross cost $ 4,337 $ 63,369 $ 3,728 $ 16,025 $ 29,308 $ 116,767 Additions due to acquisition (1) 500 9,000 — 1,000 — 10,500 Foreign currency translation impact 20 190 37 42 25 314 Gross cost 4,857 72,559 3,765 17,067 29,333 127,581 Accumulated amortization (2), (3) (2,046 ) (19,469 ) (2,521 ) (10,266 ) (12,070 ) (46,372 ) Balance, March 31, 2017 $ 2,811 $ 53,090 $ 1,244 $ 6,801 $ 17,263 $ 81,209 December 31, 2016 Trade Names Customer Relationships Content Software Non-Compete Total Gross cost $ 4,337 $ 63,369 $ 3,728 $ 16,025 $ 29,308 $ 116,767 Accumulated amortization (2), (3) (1,737 ) (16,744 ) (2,033 ) (8,904 ) (10,548 ) (39,966 ) Balance, December 31, 2016 $ 2,600 $ 46,625 $ 1,695 $ 7,121 $ 18,760 $ 76,801 (1) The additions are due to the acquisition of L2 in March 2017. (2) Intangible assets are amortized against earnings over the following periods: Trade names— 2 to 4 years ; Customer relationships— 4 to 8 years ; Content— 1.5 to 2 years ; Software— 3 years ; Non-compete— 3 to 5 years . (3) Aggregate amortization expense related to intangible assets was $6.3 million and $6.2 million for the three months ended March 31, 2017 and 2016 , respectively
Schedule of estimated future amortization expense by year	The estimated future amortization expense by year from finite-lived intangibles will be as follows (in thousands): 2017 (remaining nine months) $ 18,508 2018 21,836 2019 16,624 2020 14,116 2021 6,533 Thereafter 3,592 $ 81,209

Debt (Tables)

Debt (Tables)	3 Months Ended
	Mar. 31, 2017
Debt Disclosure [Abstract]
Schedule of debt	Balance Balance March 31, December 31, Description: 2017 2016 2016 Credit Agreement - Term loan A facility (1) $ 585,000 $ 585,000 2016 Credit Agreement - Revolving credit facility (1), (2) 270,000 115,000 Senior Notes, $800.0 million principal amount (3) 800,000 — Other (4) 2,500 2,500 Subtotal (5) 1,657,500 702,500 Less: deferred financing fees (6) (28,803 ) (8,109 ) Net carrying amount (7) $ 1,628,697 $ 694,391 (1) The contractual annualized interest rate as of March 31, 2017 on both the Term loan A facility and revolving credit facility was 2.23% , which consisted of a floating eurodollar base rate of 0.98% plus a margin of 1.25% . However, the Company has interest rate swap contracts, accounted for as cash flow hedges, which effectively convert the floating eurodollar base rates to a fixed base rate. (2) The Company had $927.0 million of available borrowing capacity on the revolver (not including the expansion feature) as of March 31, 2017 . (3) Consists of $800.0 million principal amount of Senior Notes outstanding, which the Company issued on March 30, 2017 to finance in part the CEB acquisition. The Senior Notes pay a fixed rate of 5.125% and have an eight year maturity. (4) Consists of a $2.5 million State of Connecticut economic development loan with a 3.00% fixed rate of interest. The loan was originated in 2012 and has a 10 year maturity. Principal payments are deferred for the first five years and the loan may be repaid at any point by the Company without penalty. (5) The average annual effective rate on the Company's total debt outstanding for the three months ended March 31, 2017 , including the effect of its interest rate swaps discussed below, was approximately 2.89% . (6) The deferred financing fees are being amortized to Interest Expense, net over the term of the respective debt obligation. (7) On April 5, 2017, the Company completed the acquisition of CEB. The Company had approximately $3.6 billion in total debt outstanding after the close of the acquisition. Note 14 — Subsequent Events provides additional information regarding the CEB acquisition and the additional amounts borrowed.

Equity (Tables)

Equity (Tables)	3 Months Ended
	Mar. 31, 2017
Stockholders' Equity Note [Abstract]
Schedule of share repurchase activity	The Company’s recent share repurchase activity is presented in the following table: Three Months Ended March 31, 2017 2016 Number of shares repurchased (1) 218,752 466,823 Cash paid for repurchased shares (in thousands) (2) $ 21,978 $ 45,487 (1) The average purchase price for repurchased shares was $100.47 and $82.02 for the three months ended March 31, 2017 and 2016, respectively. (2) The cash paid for the three months ended March 31, 2016 included $7.2 million for share repurchases that were executed in late December 2015 and were settled in early January 2016.
Schedule of the changes in AOCI by component (net of tax)	The following tables disclose information about changes in AOCL/I by component and the related amounts reclassified out of AOCL/I to income during the periods indicated (net of tax, in thousands) (1): For the three months ended March 31, 2017 : Interest Rate Swaps Defined Benefit Pension Plans Foreign Currency Translation Adjustments Total Balance - December 31, 2016 $ (1,409 ) $ (5,797 ) $ (42,477 ) $ (49,683 ) Changes during the period: Change in AOCL/I before reclassifications to income (3,393 ) — 4,371 978 Reclassifications from AOCL/I to income during the period (2), (3) 825 48 — 873 Other comprehensive (loss) income for the period (2,568 ) 48 4,371 1,851 Balance – March 31, 2017 $ (3,977 ) $ (5,749 ) $ (38,106 ) $ (47,832 ) For the three months ended March 31, 2016 : Interest Rate Defined Foreign Total Balance – December 31, 2015 $ (3,079 ) $ (4,832 ) $ (36,491 ) $ (44,402 ) Changes during the period: Change in AOCL/I before reclassifications to income (8,357 ) — 2,068 (6,289 ) Reclassifications from AOCL/I to income during the period (2), (3) 1,224 37 — 1,261 Other comprehensive (loss) income for the period (7,133 ) 37 2,068 (5,028 ) Balance – March 31, 2016 $ (10,212 ) $ (4,795 ) $ (34,423 ) $ (49,430 ) (1) Amounts in parentheses represent debits (deferred losses). (2) The reclassifications related to interest rate swaps (cash flow hedges) were recorded in Interest expense, net of tax effect. See Note 10 – Derivatives and Hedging for information regarding the hedges. (3) The reclassifications related to defined benefit pension plans were recorded in Selling, general and administrative expense, net of tax effect. See Note 12 – Employee Benefits for information regarding the Company’s defined benefit pension plans.

Derivatives and Hedging (Tables

Derivatives and Hedging (Tables)	3 Months Ended
	Mar. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of notional amounts of outstanding derivative positions	The following tables provide information regarding the Company’s outstanding derivatives contracts as of the dates indicated (in thousands, except for number of outstanding contracts): March 31, 2017 Derivative Contract Type Number of Outstanding Contracts Notional Amounts Fair Value Asset (Liability), Net (3) Balance Sheet Line Item Unrealized Loss Recorded in OCI Interest rate swaps (1) 5 $ 1,400,000 $ (6,630 ) Other liabilities (3,977 ) Foreign currency forwards (2) 23 45,425 (159 ) Accrued liabilities — Total 28 $ 1,445,425 $ (6,789 ) (3,977 ) December 31, 2016 Derivative Contract Type Number of Outstanding Contracts Notional Amounts Fair Value Asset (Liability), Net (3) Balance Sheet Line Item Unrealized Loss Recorded in OCI Interest rate swaps (1) 3 $ 700,000 $ (2,349 ) Other liabilities $ (1,409 ) Foreign currency forwards (2) 84 86,946 (320 ) Accrued liabilities — Total 87 $ 786,946 $ (2,669 ) $ (1,409 ) (1) The swaps have been designated and are accounted for as cash flow hedges of the forecasted interest payments on borrowings. As a result, changes in fair value of the swaps are deferred and are recorded in AOCL/I, net of tax effect (see Note 7 — Debt for additional information). (2) The Company has foreign exchange transaction risk since it typically enters into transactions in the normal course of business that are denominated in foreign currencies that differ from the local functional currency. The Company enters into short-term foreign currency forward exchange contracts to mitigate the cash flow risk associated with changes in foreign currency rates on forecasted foreign currency transactions. These contracts are accounted for at fair value with realized and unrealized gains and losses recognized in Other expense, net since the Company does not designate these contracts as hedges for accounting purposes. All of the contracts outstanding at March 31, 2017 matured by the end of April 2017. (3) See Note 11 — Fair Value Disclosures for the determination of the fair value of these instruments.
Schedule of derivative instruments, gain (loss) in statement of financial performance	The following table provides information regarding amounts recognized in the Condensed Consolidated Statements of Operations for derivative contracts for the periods indicated (in thousands): Three Months Ended March 31, Amount recorded in: 2017 2016 Interest expense, net (1) $ 1,375 $ 1,987 Other expense, net (2) 219 335 Total expense, net $ 1,594 $ 2,322 (1) Consists of interest expense from interest rate swap contracts. (2) Consists of realized and unrealized gains and losses on foreign currency forward contracts.

Fair Value Disclosures (Tables)

Fair Value Disclosures (Tables)	3 Months Ended
	Mar. 31, 2017
Fair Value Disclosures [Abstract]
Schedule of fair value, assets and liabilities measured on recurring basis	The Company’s assets and liabilities that are remeasured to fair value are presented in the following table (in thousands): Fair Value Fair Value Description: March 31, December 31, Assets: Values based on Level 1 inputs: Deferred compensation plan assets (1) $ 11,211 $ 10,247 Total Level 1 inputs 11,211 10,247 Values based on Level 2 inputs: Deferred compensation plan assets (1) 29,174 27,847 Foreign currency forward contracts (2) 39 165 Total Level 2 inputs 29,213 28,012 Total Assets $ 40,424 $ 38,259 Liabilities: Values based on Level 2 inputs: Deferred compensation plan liabilities (1) $ 45,595 $ 43,075 Foreign currency forward contracts (2) 198 485 Interest rate swap contracts (3) 6,630 2,349 Total Level 2 inputs 52,423 45,909 Total Liabilities $ 52,423 $ 45,909 (1) The Company has a deferred compensation plan for the benefit of certain highly compensated officers, managers and other key employees. The assets consist of investments in money market and mutual funds, and company-owned life insurance contracts, all of which are valued based on Level 1 or Level 2 valuation inputs. The related deferred compensation plan liabilities are recorded at fair value, or the estimated amount needed to settle the liability, which the Company considers to be a Level 2 input. (2) The Company enters into foreign currency forward exchange contracts to hedge the effects of adverse fluctuations in foreign currency exchange rates. Valuation of the foreign currency forward contracts is based on observable foreign currency exchange rates in active markets, which the Company considers a Level 2 input. (3) The Company has interest rate swap contracts which hedge the risk of variability from interest payments on its borrowings (see Note 7 — Debt). The fair value of the swaps is based on mark-to-market valuations prepared by a third-party broker. The valuations are based on observable interest rates from recently executed market transactions and other observable market data, which the Company considers Level 2 inputs. The Company independently corroborates the reasonableness of the valuations prepared by the third-party broker through the use of an electronic quotation service.

Business and Basis of Present30

Business and Basis of Presentation (Details)	3 Months Ended
	Mar. 31, 2017segment
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of reportable segments	3

Business and Basis of Present31

Business and Basis of Presentation - New Accounting Pronouncements (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Basic earnings per share (in dollars per share)	$ 0.44	$ 0.55
Diluted earnings per share (in dollars per share)	$ 0.43	$ 0.54
Cash provided by operating activities	$ (29,605)	$ 13,331
Net income	$ 36,433	$ 44,987
Accounting Standards Update 2016-09 | New Accounting Pronouncement, Early Adoption, Effect
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Basic earnings per share (in dollars per share)		$ 0.06
Diluted earnings per share (in dollars per share)		$ 0.06
Net income		$ 4,800
Accounting Standards Update 2016-09, Statutory Tax Withholding Component | New Accounting Pronouncement, Early Adoption, Effect
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cash provided by operating activities		$ 4,800

Acquisitions - (Details)

Acquisitions - (Details)	Mar. 09, 2017USD ($)employee	Mar. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Business Acquisition [Line Items]
Goodwill		$ 855,330,000	$ 738,453,000
L2, Inc.
Business Acquisition [Line Items]
Percentage of voting interests acquired	100.00%
Entity number of employees | employee	150
Business combination, consideration transferred	$ 155,000,000
Aggregate purchase price	134,200,000
Net cash paid for acquisition	129,300,000
Contingent consideration arrangements, maximum value (up to)	$ 20,800,000
Contingent consideration arrangements, maximum value, period of expense recognition	3 years
Goodwill	$ 124,700,000
Business combination, amortizable intangible assets recognized	9,500,000
Business acquisition, goodwill, expected tax deductible amount	$ 0

Earnings per Share (Detail)

Earnings per Share (Detail) - shares shares in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Earnings Per Share [Abstract]
Antidilutive securities excluded from computation of earnings per share (less than) (in shares)	0.4	0.4

Earnings per Share (Detail) - C

Earnings per Share (Detail) - Calculations Of Basic And Diluted Earnings Per Share - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Numerator:
Net income used for calculating basic and diluted earnings per common share	$ 36,433	$ 44,987
Denominator:
Weighted average number of common shares used in the calculation of basic earnings per share	82,835	82,451
Common stock equivalents associated with stock-based compensation plans (in shares)	1,260	1,013
Shares used in the calculation of diluted earnings per share	84,095	83,464
Basic earnings per share (in dollars per share)	$ 0.44	$ 0.55
Diluted earnings per share (in dollars per share)	$ 0.43	$ 0.54

Stock-Based Compensation (Detai

Stock-Based Compensation (Detail) - USD ($) $ / shares in Units, shares in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for grant (in shares)	5.5
Common stock par value (in dollars per share)	$ 0.0005		$ 0.0005
Total share-based compensation cost not yet recognized	$ 83,000,000
Total compensation cost not yet recognized, period for recognition	2 years 9 months 18 days
Total stock-based compensation expense	$ 22,600,000	$ 15,500,000
Retirement Eligible Employees Equity Award
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 14,500,000	10,300,000
Stock appreciation rights (SARs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total compensation cost not yet recognized, period for recognition	4 years
Award vesting period	4 years
Award expiration period from date of grant	7 years
Total stock-based compensation expense	$ 2,800,000	1,700,000
Restricted stock units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	4 years
Total stock-based compensation expense	$ 19,600,000	13,600,000
Performance-based RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	4 years
Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee stock purchase plan, stock purchases as percentage of employee compensation maximum	10.00%
Maximum share value authorized for purchase under employee stock purchase plan	$ 23,750
Exercisable price percentage of closing price of another class of stock	95.00%
Maximum number of shares that may be purchased by eligible participants (in shares)	0.9
Proceeds from stock plans	$ 3,000,000	$ 2,600,000

Stock-Based Compensation (Det36

Stock-Based Compensation (Detail) - Stock-Based Compensation Expense Recognized In Consolidated Statements Of Operations - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 22.6	$ 15.5
Cost of services and product development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	9.3	7.6
Cost of services and product development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	13.3	7.9
Stock appreciation rights (SARs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	2.8	1.7
Common Stock Equivalents (CSEs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	0.2	0.2
Restricted stock units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 19.6	$ 13.6

Stock-Based Compensation (Det37

Stock-Based Compensation (Detail) - Summary Of Changes In SARs Outstanding - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum number of shares that may be purchased by eligible participants (in shares)	0.9
Weighted Average Remaining Contractual Term [Roll Forward]
Proceeds from stock plans	$ 3	$ 2.6
Restricted stock units (RSUs)
SARs [Roll Forward]
Outstanding at December 31, 2016 (in shares)	1.3
Granted (in shares)	0.5
Outstanding at March 31, 2017 (in shares)	1.3		1.3
Per Share Weighted Average Grant Date Fair Value [Roll Forward]
Outstanding at December 31, 2016 (in dollars per share)	$ 73.19
Granted (in dollars per share)	99.14
Outstanding at March 31, 2017 (in dollars per share)	$ 84.40		$ 73.19
Weighted Average Remaining Contractual Term [Roll Forward]
Outstanding at March 31, 2017	1 year 9 months 18 days
Stock appreciation rights (SARs)
SARs [Roll Forward]
Outstanding at December 31, 2016 (in shares)	1.3
Granted (in shares)	0.3
Exercised (in shares)	0
Outstanding at March 31, 2017 (in shares)	1.6		1.3
Vested and exercisable at March 31, 2017 (in shares)	0.8
Per Share Weighted- Average Exercise Price [Roll Forward]
Outstanding at December 31, 2016 (in dollars per share)	$ 66.22
Granted (in dollars per share)	99.07
Exercised (in dollars per share)	0
Outstanding at March 31, 2017 (in dollars per share)	73.16		$ 66.22
Vested and exercisable at March 31, 2017 (in dollars per share)	60.70
Per Share Weighted Average Grant Date Fair Value [Roll Forward]
Outstanding at December 31, 2016 (in dollars per share)	15.77
Granted (in dollars per share)	22.02
Exercised (in dollars per share)	0
Outstanding at March 31, 2017 (in dollars per share)	17.02		$ 15.77
Vested and exercisable at March 31, 2017 (in dollars per share)	$ 15.36
Weighted Average Remaining Contractual Term [Roll Forward]
Granted	6 years 10 months 6 days
Outstanding at March 31, 2017	4 years 9 months 11 days		4 years 4 months 24 days
Vested and exercisable at March 31, 2017	3 years 8 months 1 day
Aggregate Intrinsic value of outstanding shares	$ 54.2
Aggregate intrinsic value of shares vested and exercisable	$ 36.4
Stock appreciation rights (SARs) | Unvested
SARs [Roll Forward]
Outstanding at March 31, 2017 (in shares)	0.8
Executive officer | Restricted stock units (RSUs)
SARs [Roll Forward]
Granted (in shares)	0.2
Target amount | Executive officer | Minimum | Restricted stock units (RSUs)
SARs [Roll Forward]
Percentage of shares authorized for grant	0.00%
Target amount | Executive officer | Maximum | Restricted stock units (RSUs)
SARs [Roll Forward]
Percentage of shares authorized for grant	200.00%

Stock-Based Compensation (Det38

Stock-Based Compensation (Detail) - Weighted-Average Assumptions Used To Determine Fair Value Of SARs Grants On Date Of Grant Using Black-Scholes-Merton Valuation Model - Stock appreciation rights (SARs)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract]
Expected dividend yield	0.00%	0.00%
Expected stock price volatility	22.00%	22.00%
Risk-free interest rate	1.80%	1.10%
Expected life in years	4 years 6 months	4 years 4 months 24 days

Stock-Based Compensation (Det39

Stock-Based Compensation (Detail) - Summary Of Changes In RSUs Outstanding - Restricted stock units (RSUs) shares in Millions	3 Months Ended
	Mar. 31, 2017$ / sharesshares
Restricted Stock Units (RSUs) [Roll Forward]
Outstanding at December 31, 2016 (in shares)	1.3
Granted (in shares)	0.5
Vested and released (in shares)	0.5
Forfeited (in shares)	0
Outstanding at March 31, 2017 (in shares)	1.3
Per Share Weighted Average Grant Date Fair Value [Roll Forward]
Outstanding at December 31, 2016 (in dollars per share) | $ / shares	$ 73.19
Granted (in dollars per share) | $ / shares	99.14
Vested and released (in dollars per share) | $ / shares	68.11
Forfeited (in dollars per share) | $ / shares	81.85
Outstanding at March 31, 2017 (in dollars per share) | $ / shares	$ 84.40
Weighted average remaining contractual terms	1 year 9 months 18 days
Executive officer
Restricted Stock Units (RSUs) [Roll Forward]
Granted (in shares)	0.2
Executive officer | Minimum | Target amount
Per Share Weighted Average Grant Date Fair Value [Roll Forward]
Percentage of shares authorized for grant	0.00%
Executive officer | Maximum | Target amount
Per Share Weighted Average Grant Date Fair Value [Roll Forward]
Percentage of shares authorized for grant	200.00%
Non executive
Restricted Stock Units (RSUs) [Roll Forward]
Granted (in shares)	0.3

Stock-Based Compensation (Det40

Stock-Based Compensation (Detail) - Summary Of Changes In CSEs Outstanding - Common stock equivalents (CSEs)	3 Months Ended
	Mar. 31, 2017$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Base fee percentage (up to)	50.00%
Common Stock Equivalents (CSEs) [Roll Forward]
Outstanding at December 31, 2016 (in shares) | shares	107,338
Granted (in shares) | shares	1,592
Converted to common shares upon grant (in shares) | shares	1,161
Outstanding at March 31, 2017 (in shares) | shares	107,769
Per Share Weighted Average Grant Date Fair Value [Roll Forward]
Outstanding at December 31, 2016 (in dollars per share) | $ / shares	$ 20.74
Granted (in dollars per share) | $ / shares	108.95
Converted to common shares upon grant (in dollars per share) | $ / shares	108.95
Outstanding at March 31, 2017 (in dollars per share) | $ / shares	$ 21.09

Segment Information (Details) -

Segment Information (Details) - Information About Reportable Segments	3 Months Ended
	Mar. 31, 2017USD ($)segment	Mar. 31, 2016USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment	3
Revenues	$ 625,169,000	$ 557,266,000
Operating income	53,514,000	64,429,000
Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenues	0	0
Reportable segments
Segment Reporting Information [Line Items]
Revenues	625,169,000	557,266,000
Gross contribution	388,617,000	350,547,000
Corporate and other expenses
Segment Reporting Information [Line Items]
Corporate and other expenses	(335,103,000)	(286,118,000)
Research | Reportable segments
Segment Reporting Information [Line Items]
Revenues	504,652,000	440,271,000
Gross contribution	346,708,000	308,186,000
Consulting | Reportable segments
Segment Reporting Information [Line Items]
Revenues	85,248,000	84,940,000
Gross contribution	28,342,000	29,378,000
Events | Reportable segments
Segment Reporting Information [Line Items]
Revenues	35,269,000	32,055,000
Gross contribution	$ 13,567,000	$ 12,983,000

Segment Information (Details)42

Segment Information (Details) - Reconciliation of Segment Gross Contribution to Net Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Costs and expenses:
Cost of services and product development - unallocated	$ 237,609	$ 212,041
Selling, general and administrative	304,244	257,411
Acquisition and integration charges	13,272	8,368
Operating income	53,514	64,429
Interest expense and other, net	5,017	4,122
Provision for income taxes	12,064	15,320
Net income	36,433	44,987
Reportable segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total segment gross contribution	$ 388,617	350,547
Reportable segments | Maximum
Costs and expenses:
Percent of target bonus allocated to segments	100.00%
Corporate and other expenses
Costs and expenses:
Cost of services and product development - unallocated	$ 1,057	5,322
Selling, general and administrative	304,244	257,411
Depreciation and amortization	16,530	15,017
Acquisition and integration charges	$ 13,272	$ 8,368

Goodwill and Intangible Asset43

Goodwill and Intangible Assets (Detail) - Changes to Carrying Amount of Goodwill by Reporting Unit - USD ($)	3 Months Ended
	Mar. 31, 2017	Sep. 30, 2016
Goodwill [Line Items]
Goodwill, accumulated impairment losses	$ 0
Goodwill impairment		$ 0
Goodwill [Roll Forward]
Balance, December 31, 2016	738,453,000
Additions due to acquisitions	114,222,000
Foreign currency translation adjustments	2,655,000
Balance, March 31, 2017	855,330,000
Research
Goodwill [Roll Forward]
Balance, December 31, 2016	595,450,000
Additions due to acquisitions	114,222,000
Foreign currency translation adjustments	2,376,000
Balance, March 31, 2017	712,048,000
Consulting
Goodwill [Roll Forward]
Balance, December 31, 2016	96,480,000
Additions due to acquisitions	0
Foreign currency translation adjustments	197,000
Balance, March 31, 2017	96,677,000
Events
Goodwill [Roll Forward]
Balance, December 31, 2016	46,523,000
Additions due to acquisitions	0
Foreign currency translation adjustments	82,000
Balance, March 31, 2017	$ 46,605,000

Goodwill and Intangible Asset44

Goodwill and Intangible Assets (Detail) - Carrying Amounts of Amortizable Intangible Assets - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Finite-lived Intangible Assets [Roll Forward]
Gross carrying amount	$ 116,767
Finite-lived Intangible Assets Acquired	10,500
Foreign currency translation impact	314
Gross carrying amount	127,581
Accumulated amortization	(46,372)		$ (39,966)
Finite-lived intangible assets, net	81,209		76,801
Amortization of intangibles	6,290	$ 6,183
Trade Name
Finite-lived Intangible Assets [Roll Forward]
Gross carrying amount	4,337
Finite-lived Intangible Assets Acquired	500
Foreign currency translation impact	20
Gross carrying amount	4,857
Accumulated amortization	(2,046)		(1,737)
Finite-lived intangible assets, net	$ 2,811		2,600
Trade Name | Minimum
Finite-lived Intangible Assets [Roll Forward]
Finite-lived intangible assets useful life	4 years
Trade Name | Maximum
Finite-lived Intangible Assets [Roll Forward]
Finite-lived intangible assets useful life	2 years
Customer Relationships
Finite-lived Intangible Assets [Roll Forward]
Gross carrying amount	$ 63,369
Finite-lived Intangible Assets Acquired	9,000
Foreign currency translation impact	190
Gross carrying amount	72,559
Accumulated amortization	(19,469)		(16,744)
Finite-lived intangible assets, net	$ 53,090		46,625
Customer Relationships | Minimum
Finite-lived Intangible Assets [Roll Forward]
Finite-lived intangible assets useful life	4 years
Customer Relationships | Maximum
Finite-lived Intangible Assets [Roll Forward]
Finite-lived intangible assets useful life	8 years
Content
Finite-lived Intangible Assets [Roll Forward]
Gross carrying amount	$ 3,728
Finite-lived Intangible Assets Acquired	0
Foreign currency translation impact	37
Gross carrying amount	3,765
Accumulated amortization	(2,521)		(2,033)
Finite-lived intangible assets, net	$ 1,244		1,695
Content | Minimum
Finite-lived Intangible Assets [Roll Forward]
Finite-lived intangible assets useful life	1 year 6 months
Content | Maximum
Finite-lived Intangible Assets [Roll Forward]
Finite-lived intangible assets useful life	2 years
Software
Finite-lived Intangible Assets [Roll Forward]
Gross carrying amount	$ 16,025
Finite-lived Intangible Assets Acquired	1,000
Foreign currency translation impact	42
Gross carrying amount	17,067
Accumulated amortization	(10,266)		(8,904)
Finite-lived intangible assets, net	$ 6,801		7,121
Finite-lived intangible assets useful life	3 years
Non-Compete
Finite-lived Intangible Assets [Roll Forward]
Gross carrying amount	$ 29,308
Finite-lived Intangible Assets Acquired	0
Foreign currency translation impact	25
Gross carrying amount	29,333
Accumulated amortization	(12,070)		(10,548)
Finite-lived intangible assets, net	$ 17,263		$ 18,760
Non-Compete | Minimum
Finite-lived Intangible Assets [Roll Forward]
Finite-lived intangible assets useful life	3 years
Non-Compete | Maximum
Finite-lived Intangible Assets [Roll Forward]
Finite-lived intangible assets useful life	5 years

Goodwill and Intangible Asset45

Goodwill and Intangible Assets (Detail) - Estimated Future Amortization Expense By Year From Amortizable Intangibles - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2017 (remaining nine months)	$ 18,508
2,018	21,836
2,019	16,624
2,020	14,116
2,021	6,533
Thereafter	3,592
Finite-lived intangible assets, net	$ 81,209	$ 76,801

Debt (Detail)

Debt (Detail)	Mar. 30, 2017USD ($)	Mar. 20, 2017installment	Mar. 31, 2017USD ($)amendment	Apr. 05, 2017USD ($)	Dec. 31, 2016USD ($)
Debt Instrument [Line Items]
Long-term debt, gross			$ 1,657,500,000		$ 702,500,000
Debt instrument, effective percentage			2.89%
Long-term debt			$ 1,628,697,000		694,391,000
Bank Term Loan
Debt Instrument [Line Items]
Long-term debt, gross			$ 585,000,000		585,000,000
Debt instrument interest additional interest above base rate			1.25%
Connecticut Economic Development Program
Debt Instrument [Line Items]
Long-term debt, gross			$ 2,500,000		2,500,000
Revolving credit facility
Debt Instrument [Line Items]
Long-term debt, gross			$ 270,000,000		$ 115,000,000
Floating eurodollar based rate			0.98%
Debt instrument interest additional interest above base rate			1.25%
Line of credit facility, remaining borrowing capacity			$ 927,000,000
Interest rate swaps
Debt Instrument [Line Items]
Interest rate, fair value hedge derivative at fair value, net (negative fair value)			$ 6,600,000
2016 Agreement
Debt Instrument [Line Items]
Debt instrument, number of debt agreement amendments | amendment			2
Debt instrument, interest, additional interest above eurodollar rate		1.00%
2016 Agreement | Federal Funds Rate
Debt Instrument [Line Items]
Debt instrument interest additional interest above federal fund rate		0.50%
Minimum applicable margin rate		0.125%
Maximum applicable margin rate		1.50%
2016 Agreement | Euro Dollar rate
Debt Instrument [Line Items]
Minimum applicable margin rate		1.125%
Maximum applicable margin rate		2.50%
2016 Agreement | Bank Term Loan
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity			$ 600,000,000
Long-term debt, gross			585,000,000
2016 Agreement | Revolving credit facility
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity			1,200,000,000
Long-term debt, gross			270,000,000
Line of credit facility, frequency of payments, number of quarterly installments | installment		16
Subsequent Event
Debt Instrument [Line Items]
Long-term debt				$ 3,600,000,000
CEB | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross	$ 800,000,000		$ 800,000,000
Debt instrument, issue price, percent	100.00%
Debt instrument, redemption, prince, percentage of principal amount that may be redeemed	40.00%
CEB | Debt instrument, redemption with the proceeds of certain equity offerings | Senior Notes
Debt Instrument [Line Items]
Debt instrument, redemption price, percentage	105.125%
CEB | Debt instrument, redemption excluding make whole premium | Senior Notes
Debt Instrument [Line Items]
Debt instrument, redemption price, percentage	100.00%
CEB | Debt instrument, redemption due to specific kinds of change of control | Senior Notes
Debt Instrument [Line Items]
Debt instrument, redemption price, percentage	101.00%

Debt (Detail) - Borrowings

Debt (Detail) - Borrowings - USD ($)	Mar. 30, 2017	Mar. 31, 2017	Dec. 31, 2012	Dec. 31, 2016
Debt Instrument [Line Items]
Long-term debt, gross		$ 1,657,500,000		$ 702,500,000
Debt issuance costs, line of credit arrangements, net		(28,803,000)		(8,109,000)
Long-term debt		$ 1,628,697,000		694,391,000
Debt instrument, effective percentage		2.89%
Interest rate swaps
Debt Instrument [Line Items]
Derivative, term of contract		30 days
Interest rate, fair value hedge derivative at fair value, net (negative fair value)		$ 6,600,000
Bank Term Loan
Debt Instrument [Line Items]
Long-term debt, gross		$ 585,000,000		585,000,000
Contractual annualized interest rate		2.23%
Debt instrument interest base rate		0.98%
Debt instrument interest additional interest above base rate		1.25%
Bank Term Loan | 2016 Agreement
Debt Instrument [Line Items]
Long-term debt, gross		$ 585,000,000
Senior Notes
Debt Instrument [Line Items]
Debt instrument term	8 years
Connecticut Economic Development Program
Debt Instrument [Line Items]
Long-term debt, gross		2,500,000		2,500,000
Debt instrument, fixed interest rate			3.00%
Debt instrument term			10 years
Debt instrument, period principal payments are deferred			5 years
Revolving credit facility
Debt Instrument [Line Items]
Long-term debt, gross		$ 270,000,000		$ 115,000,000
Contractual annualized interest rate		2.23%
Debt instrument interest additional interest above base rate		1.25%
Line of credit facility, remaining borrowing capacity		$ 927,000,000
Revolving credit facility | 2016 Agreement
Debt Instrument [Line Items]
Long-term debt, gross		270,000,000
CEB | Senior Notes
Debt Instrument [Line Items]
Long-term debt, gross	$ 800,000,000	$ 800,000,000
Proceeds from issuance of debt	$ 800,000,000
Debt instrument, fixed interest rate	5.125%

Equity (Detail) - Share Repurch

Equity (Detail) - Share Repurchase Program and Share Repurchase Activity - USD ($)	Apr. 05, 2017	Jan. 31, 2016	Mar. 31, 2017	Mar. 31, 2016
Class of Stock [Line Items]
Stock repurchase program, authorized amount			$ 1,200,000,000
Stock repurchase program, remaining authorized repurchase amount			$ 1,100,000,000
Number of shares repurchased (in shares)			218,752	466,823
Cash paid for repurchased shares during the quarter		$ 7,200,000	$ 21,978,000	$ 45,487,000
Treasury stock, average price paid per share (in dollars per share)			$ 100.47	$ 82.02
CEB | Subsequent Event
Class of Stock [Line Items]
Business acquisition, equity interest issued, number of shares (in shares)	7,400,000

Equity (Details) - Changes in A

Equity (Details) - Changes in AOCI by Component (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 60,878
Other comprehensive income (loss), net of tax	1,851	$ (5,028)
Ending balance	102,817
Interest Rate Swaps
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(1,409)	(3,079)
Change in AOCL/I before reclassifications to income	(3,393)	(8,357)
Reclassifications from AOCI to income during the period	825	1,224
Other comprehensive income (loss), net of tax	(2,568)	(7,133)
Ending balance	(3,977)	(10,212)
Defined Benefit Pension Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(5,797)	(4,832)
Change in AOCL/I before reclassifications to income	0	0
Reclassifications from AOCI to income during the period	48	37
Other comprehensive income (loss), net of tax	48	37
Ending balance	(5,749)	(4,795)
Foreign Currency Translation Adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(42,477)	(36,491)
Change in AOCL/I before reclassifications to income	4,371	2,068
Reclassifications from AOCI to income during the period	0	0
Other comprehensive income (loss), net of tax	4,371	2,068
Ending balance	(38,106)	(34,423)
AOCI Attributable to Parent
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(49,683)	(44,402)
Change in AOCL/I before reclassifications to income	978	(6,289)
Reclassifications from AOCI to income during the period	873	1,261
Other comprehensive income (loss), net of tax	1,851	(5,028)
Ending balance	$ (47,832)	$ (49,430)

Income Taxes (Detail)

Income Taxes (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Provision for income taxes	$ 12,064	$ 15,320
Effective income tax rate	24.90%	25.40%
Unrecognized tax benefits	$ 42,600		$ 37,100
Decrease in unrecognized tax benefits is reasonably possible	$ 3,800

Derivatives and Hedging (Detail

Derivatives and Hedging (Detail) - Outstanding Derivatives Contracts $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2017USD ($)outstanding_contract	Dec. 31, 2016USD ($)outstanding_contract
Derivatives, Fair Value [Line Items]
Number of Outstanding Contracts | outstanding_contract	28	87
Notional Amounts	$ 1,445,425	$ 786,946
Fair Value Asset (Liability), Net	$ (6,789)	(2,669)
Unrealized Loss Recorded in OCI		$ (1,409)
Designated as hedging instrument | Other liabilities | Interest rate swaps
Derivatives, Fair Value [Line Items]
Number of Outstanding Contracts | outstanding_contract	5	3
Notional Amounts	$ 1,400,000	$ 700,000
Fair Value Asset (Liability), Net	(6,630)	(2,349)
Unrealized Loss Recorded in OCI	$ (3,977)	$ (1,409)
Not Designated as Hedging Instrument | Accrued liabilities | Foreign currency forwards
Derivatives, Fair Value [Line Items]
Number of Outstanding Contracts | outstanding_contract	23	84
Notional Amounts	$ 45,425	$ 86,946
Fair Value Asset (Liability), Net	(159)	(320)
Unrealized Loss Recorded in OCI	$ 0	$ 0

Derivatives and Hedging (Deta52

Derivatives and Hedging (Detail) - Derivative Gains And Losses That Have Been Recognized In Condensed Consolidated Statements Of Operations - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Total expense, net	$ 1,594	$ 2,322
Interest expense, net
Derivative Instruments, Gain (Loss) [Line Items]
Total expense, net	1,375	1,987
Other expense (income), net
Derivative Instruments, Gain (Loss) [Line Items]
Total expense, net	$ 219	$ 335

Fair Value Disclosures (Detail)

Fair Value Disclosures (Detail) - Assets And Liabilities Measured At Fair Value On Recurring Basis - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Assets:
Assets measured at fair value on a recurring basis	$ 40,424	$ 38,259
Fair Value, Inputs, Level 1 | Deferred compensation plan assets
Assets:
Assets measured at fair value on a recurring basis	11,211	10,247
Fair Value, Inputs, Level 2
Assets:
Assets measured at fair value on a recurring basis	29,213	28,012
Liabilities:
Liabilities measured at fair value on a recurring basis	52,423	45,909
Fair Value, Inputs, Level 2 | Foreign currency forward contracts
Assets:
Assets measured at fair value on a recurring basis	39	165
Liabilities:
Liabilities measured at fair value on a recurring basis	198	485
Fair Value, Inputs, Level 2 | Interest rate swap contracts
Liabilities:
Liabilities measured at fair value on a recurring basis	6,630	2,349
Fair Value, Inputs, Level 2 | Deferred compensation plan assets
Assets:
Assets measured at fair value on a recurring basis	29,174	27,847
Fair Value, Inputs, Level 2 | Deferred compensation plan liabilities
Liabilities:
Liabilities measured at fair value on a recurring basis	$ 45,595	$ 43,075

Employee Benefits (Detail)

Employee Benefits (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Compensation and Retirement Disclosure [Abstract]
Net periodic pension expense	$ 0.7	$ 0.7

Commitments and Contingencies (

Commitments and Contingencies (Details) $ in Thousands	Mar. 31, 2017USD ($)
Commitments and Contingencies Disclosure [Abstract]
Loss Contingency Accrual	$ 0

Subsequent Events - (Details)

Subsequent Events - (Details) - USD ($) shares in Millions	Apr. 05, 2017	Mar. 30, 2017	Mar. 31, 2017	Dec. 31, 2016
Subsequent Event [Line Items]
Long-term debt			$ 1,628,697,000	$ 694,391,000
Subsequent Event
Subsequent Event [Line Items]
Long-term debt	$ 3,600,000,000
Subsequent Event | CEB
Subsequent Event [Line Items]
Business combination, consideration transferred	3,500,000,000
Aggregate purchase price	$ 2,700,000,000
Business acquisition, equity interest issued, number of shares (in shares)	7.4
Proceeds from issuance of debt	$ 2,800,000,000
Debt instrument, prepayment premium term	6 months
Debt instrument, prepayment premium	1.00%
Subsequent Event | CEB | Bridge Loan
Subsequent Event [Line Items]
Proceeds from issuance of debt	$ 300,000,000
Debt instrument term	364 days
Subsequent Event | Revolving credit facility | CEB
Subsequent Event [Line Items]
Proceeds from issuance of debt	$ 275,000,000
London Interbank Offered Rate (LIBOR) | Subsequent Event | CEB | Bridge Loan
Subsequent Event [Line Items]
Debt instrument, basis spread on variable rate	2.75%
London Interbank Offered Rate (LIBOR) | Subsequent Event | Secured Debt | CEB
Subsequent Event [Line Items]
Debt instrument, basis spread on variable rate	2.00%
Base Rate | Subsequent Event | CEB | Bridge Loan
Subsequent Event [Line Items]
Debt instrument, basis spread on variable rate	1.75%
Base Rate | Subsequent Event | Secured Debt | CEB
Subsequent Event [Line Items]
Debt instrument, basis spread on variable rate	1.00%
Senior Notes
Subsequent Event [Line Items]
Debt instrument term		8 years
Senior Notes | CEB
Subsequent Event [Line Items]
Proceeds from issuance of debt		$ 800,000,000
Line of Credit | Subsequent Event | CEB
Subsequent Event [Line Items]
Proceeds from issuance of debt	$ 1,700,000,000
Bank Term Loan | Subsequent Event | Secured Debt | CEB
Subsequent Event [Line Items]
Proceeds from issuance of debt	900,000,000
Line of credit facility, additional borrowing capacity	900,000,000
Bank Term Loan - B Facility | Subsequent Event | Secured Debt | CEB
Subsequent Event [Line Items]
Proceeds from issuance of debt	500,000,000
Line of credit facility, maximum borrowing capacity	$ 500,000,000
One Hundred and Eighty Days | London Interbank Offered Rate (LIBOR) | Subsequent Event | CEB | Bridge Loan
Subsequent Event [Line Items]
Debt instrument rate, basis spread increase	0.25%
One Hundred and Eighty Days | Base Rate | Subsequent Event | CEB | Bridge Loan
Subsequent Event [Line Items]
Debt instrument rate, basis spread increase	0.25%
Ninety Days Thereafter | London Interbank Offered Rate (LIBOR) | Subsequent Event | CEB | Bridge Loan
Subsequent Event [Line Items]
Debt instrument rate, basis spread increase	0.25%
Ninety Days Thereafter | Base Rate | Subsequent Event | CEB | Bridge Loan
Subsequent Event [Line Items]
Debt instrument rate, basis spread increase	0.25%