Gartner (IT) 10-Q 3 Nov 16 2016 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2016	Oct. 31, 2016
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	Sep. 30, 2016
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Common Stock, Shares Outstanding (in shares)		82,609,884

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 465,734	$ 372,976
Fees receivable, net of allowances of $7,000 and $6,900, respectively	560,202	580,763
Deferred commissions	112,697	124,831
Prepaid expenses and other current assets	107,316	62,427
Total current assets	1,245,949	1,140,997
Property, equipment and leasehold improvements, net	118,789	108,733
Goodwill	742,926	715,359
Intangible assets, net	81,769	96,544
Other assets	88,307	113,053
Total Assets	2,277,740	2,174,686
Current liabilities:
Accounts payable and accrued liabilities	348,429	387,691
Deferred revenues	1,028,995	900,801
Current portion of long-term debt	40,000	35,000
Total current liabilities	1,417,424	1,323,492
Long-term debt	696,405	790,000
Other liabilities	174,409	193,594
Total Liabilities	2,288,238	2,307,086
Stockholders’ Deficit
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	851,077	818,546
Accumulated other comprehensive loss, net	(47,784)	(44,402)
Accumulated earnings	1,577,521	1,450,684
Treasury stock, at cost, 73,575,816 and 73,896,245 common shares, respectively	(2,391,390)	(2,357,306)
Total Stockholders’ Deficit	(10,498)	(132,400)
Total Liabilities and Stockholders’ Deficit	$ 2,277,740	$ 2,174,686

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 7,000	$ 6,900
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)	73,575,816	73,896,245

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Revenues:
Research	$ 461,502	$ 396,179	$ 1,350,943	$ 1,162,987
Consulting	79,082	74,686	258,090	239,814
Events	33,475	29,301	132,290	116,487
Total revenues	574,059	500,166	1,741,323	1,519,288
Costs and expenses:
Cost of services and product development	223,122	193,602	666,585	581,859
Selling, general and administrative	269,902	236,355	799,322	703,868
Depreciation	9,531	8,510	27,390	24,939
Amortization of intangibles	6,221	2,737	18,614	6,983
Acquisition and integration charges	16,557	6,488	32,958	15,263
Total costs and expenses	525,333	447,692	1,544,869	1,332,912
Operating income	48,726	52,474	196,454	186,376
Interest expense, net	(5,932)	(6,049)	(19,294)	(14,769)
Other income, net	1,954	5,367	5,086	3,937
Income before income taxes	44,748	51,792	182,246	175,544
Provision for income taxes	14,264	21,426	55,149	65,672
Net income	$ 30,484	$ 30,366	$ 127,097	$ 109,872
Net income per share:
Basic (in dollars per share)	$ 0.37	$ 0.37	$ 1.54	$ 1.30
Diluted (in dollars per share)	$ 0.36	$ 0.36	$ 1.52	$ 1.29
Weighted average shares outstanding:
Basic (in shares)	82,638	82,989	82,549	84,244
Diluted (in shares)	83,803	84,113	83,761	85,435

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 30,484	$ 30,366	$ 127,097	$ 109,872
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	(3,032)	(7,900)	2,371	(21,783)
Interest rate hedges – net change in deferred loss	3,214	(5,810)	(5,865)	(6,480)
Pension – net change in actuarial deferred loss	37	53	112	159
Other comprehensive income (loss), net of tax	219	(13,657)	(3,382)	(28,104)
Comprehensive income	$ 30,703	$ 16,709	$ 123,715	$ 81,768

Condensed Consolidated Stateme6

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Operating activities:
Net income	$ 127,097	$ 109,872
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	46,004	31,922
Stock-based compensation expense	36,128	36,980
Excess tax benefits from stock-based compensation	0	(11,222)
Deferred taxes	(13,415)	(5,724)
Amortization and write-off of deferred financing fees	2,611	2,392
Changes in assets and liabilities:
Fees receivable, net	26,242	57,045
Deferred commissions	12,376	18,251
Prepaid expenses and other current assets	(43,402)	(42,347)
Other assets	21,597	(12,878)
Deferred revenues	114,197	109,595
Accounts payable, accrued, and other liabilities	(47,172)	(27,579)
Cash provided by operating activities	282,263	266,307
Investing activities:
Additions to property, equipment and leasehold improvements	(36,877)	(36,067)
Acquisitions - cash paid (net of cash acquired)	(29,363)	(169,853)
Acquisitions - increase in restricted cash (escrow)	0	25,625
Acquisitions - increase in restricted cash (escrow)	(13,600)
Cash used in investing activities	(66,240)	(231,545)
Financing activities:
Proceeds from employee stock purchase plan	6,931	5,583
Proceeds from borrowings	747,500	450,000
Payments for debt issuance costs	(4,975)	0
Payments on borrowings	(827,500)	(15,000)
Purchases of treasury stock	(52,889)	(453,000)
Excess tax benefits from stock-based compensation	0	11,222
Cash used in financing activities	(130,933)	(1,195)
Net increase in cash and cash equivalents	85,090	33,567
Effects of exchange rates on cash and cash equivalents	7,668	(27,625)
Cash and cash equivalents, beginning of period	372,976	365,302
Cash and cash equivalents, end of period	$ 465,734	$ 371,244

Business and Basis of Presentat

Business and Basis of Presentation	9 Months Ended
	Sep. 30, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Business and Basis of Presentation	Business and Basis of Presentation Business. Gartner, Inc. is a global information technology research and advisory company with its headquarters in Stamford, Connecticut. Gartner delivers its products and services globally through three business segments: Research, Consulting, and Events. When used in these notes, the terms “Gartner,” “Company,” “we,” “us,” or “our” refer to Gartner, Inc. and its consolidated subsidiaries. Basis of presentation . The accompanying interim condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“U.S. GAAP”), as defined in the Financial Accounting Standards Board ("FASB") Accounting Standards Codification (“ASC”) Topic 270 for interim financial information and with the applicable instructions of the U.S. Securities & Exchange Commission (“SEC”) Rule 10-01 of Regulation S-X on Form 10-Q and should be read in conjunction with the consolidated financial statements and related notes of the Company filed in its Annual Report on Form 10-K for the year ended December 31, 2015 . The fiscal year of Gartner is the twelve-month calendar period from January 1 through December 31. In the opinion of management, all normal recurring accruals and adjustments considered necessary for a fair presentation of financial position, results of operations and cash flows at the dates and for the periods presented herein have been included. The results of operations for the three and nine months ended September 30, 2016 may not be indicative of the results of operations for the remainder of 2016 or beyond. Principles of consolidation . The accompanying interim condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany transactions and balances have been eliminated. Use of estimates . The preparation of the accompanying interim condensed consolidated financial statements requires management to make estimates and assumptions about future events. These estimates and the underlying assumptions affect the amounts of assets and liabilities reported, disclosures about contingent assets and liabilities, and reported amounts of revenues and expenses. Such estimates include the valuation of fees receivable, goodwill, intangible assets, and other long-lived assets, as well as tax accruals and other liabilities. In addition, estimates are used in revenue recognition, income tax expense, performance-based compensation charges, depreciation and amortization. Management believes its use of estimates in these interim condensed consolidated financial statements to be reasonable. Management continuously evaluates and revises its estimates using historical experience and other factors, including the general economic environment and actions it may take in the future. Management adjusts these estimates when facts and circumstances dictate. However, these estimates may involve significant uncertainties and judgments and cannot be determined with precision. In addition, these estimates are based on management’s best judgment at a point in time. As a result, differences between our estimates and actual results could be material and would be reflected in the Company’s consolidated financial statements in future periods. Adoption of new accounting standards. The Company has recently adopted the following accounting standard: Stock-Based Compensation Accounting — The Company adopted FASB Accounting Standards Update (ASU) 2016-09, " Improvements to Employee Share-Based Payment Accounting" ("ASU No. 2016-09"), in the third quarter of 2016. While the required effective date for the adoption of this amendment for Gartner is January 1, 2017, the Company elected to early adopt ASU No. 2016-09, as permitted by the amendment. ASU No. 2016-09 requires changes in accounting for stock-based compensation, some of which must be applied to the beginning of the Company's current fiscal year, January 1, 2016. Among the changes required by ASU No. 2016-09 is that excess tax benefits or deficiencies resulting from stock-based compensation awards must be recognized in income tax expense in the Company’s Condensed Consolidated Statements of Operations. Prior to ASU No. 2016-09, excess tax benefits or deficiencies were recorded in additional paid-in capital in Stockholders' (Deficit) Equity in the Condensed Consolidated Balance Sheet. ASU No. 2016-09 requires companies to apply this amendment from the beginning of the fiscal year in which it is adopted. Accordingly, this provision is effective for Gartner beginning January 1, 2016. As a result, our previously reported income tax expense, net income, earnings per share, and accumulated earnings for the six months ended June 30, 2016 have been adjusted, and the table below summarizes these changes. As disclosed in the table, the adoption of ASU No. 2016-09 increased both our basic and diluted earnings per share for the six months ended June 30, 2016 by $0.10 per share. For the three and nine months ended September 30, 2016, the adoption of ASU No. 2016-09 increased both basic and diluted earnings per share by $0.01 and $0.11 per share, respectively. ASU No. 2016-09 also requires excess tax benefits related to stock-based compensation awards to be reported as cash flows from operating activities along with all other income tax cash flows on the Condensed Consolidated Statement of Cash Flows. Previously these excess tax benefits were reported as cash flows from financing activities on the Condensed Consolidated Statement of Cash Flows. ASU No. 2016-09 allows companies to elect either a prospective or retrospective application for the cash flow classification change, for which the Company has elected to apply this classification amendment prospectively, effective January 1, 2016. As a result, approximately $8.5 million in excess tax benefits previously reported as cash flows from financing activities on the Condensed Consolidated Statement of Cash Flows for the six months ended June 30, 2016 have been reclassified as cash flows from operating activities. The table below summarizes these retroactive changes. The Company also recorded an additional $0.5 million of excess tax benefits in the three months ended September 30, 2016 for stock-based compensation awards, resulting in a total excess tax benefit for the nine months ended September 30, 2016 of approximately $9.0 million. ASU No. 2016-09 also permits companies to make an entity-wide accounting policy election to recognize forfeitures of share-based awards as they occur or make an estimate by applying a forfeiture rate each quarter. The Company previously estimated forfeitures but has optionally selected to change its accounting policy and account for forfeitures as they occur. ASU No. 2016-09 requires this change in accounting policy to be applied using a cumulative-effect adjustment to accumulated earnings as of the beginning of the period in which the rule is adopted. Accordingly, the Company has adjusted its opening accumulated earnings effective January 1, 2016 and as a result the previously reported accumulated earnings balances as of March 31, 2016 and June 30, 2016 have been impacted. The table below summarizes these retroactive changes. The following table summarizes the retroactive impact of the adoption of ASU 2016-09 for the periods indicated (in thousands, except earnings per share data): Three Months Ended Three Months Ended Six Months Ended March 31, 2016 June 30, 2016 June 30, 2016 As Originally Reported Adjusted As Originally Reported Adjusted As Originally Reported Adjusted Provision for income taxes $ 20,140 $ 15,320 $ 29,280 $ 25,565 $ 49,420 $ 40,884 Net income 40,167 44,987 47,911 51,626 88,078 96,614 Basic earnings per share 0.49 0.55 0.58 0.63 1.07 1.17 Diluted earnings per share (1) 0.48 0.54 0.57 0.62 1.05 1.15 Operating cash flow 8,580 13,331 144,734 148,452 153,314 161,783 Accumulated earnings $ 1,490,851 $ 1,495,411 $ 1,538,762 $ 1,547,037 $ 1,538,762 $ 1,547,037 (1) ASU No. 2016-09 requires certain changes in the calculation of diluted shares. The impact of applying these changes was not significant. Accounting standards issued but not yet adopted. The FASB has issued several accounting standards that have not yet become effective and that may impact the Company’s consolidated financial statements or related disclosures in future periods. These standards and their potential impact are discussed below: 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, with early adoption permitted. We have evaluated the impact of ASU No. 2016-15 and we do not expect that it will have a material impact on Gartner's consolidated financial statements. Financial Instrument Credit Losses — In June 2016, the FASB issued ASU No. 2016-13, " Financial Instruments—Credit Losses" ("ASU No. 2016-13"). ASU No. 2016-13 amends the current financial instrument impairment model by requiring entities to use a forward-looking approach based on expected losses to estimate credit losses on certain types of financial instruments, including trade receivables. ASU No. 2016-13 is effective for Gartner on January 1, 2020, with early adoption permitted. We are currently evaluating the potential impact of ASU No. 2016-13 on the Company's consolidated financial statements. Leases — In February 2016, the FASB issued ASU No. 2016-02, " Leases " ("ASU No. 2016-02") which will require significant changes in the accounting and disclosure of lease arrangements. Among the significant changes required by ASU No. 2016-02 is that almost all lease obligations will be recorded on the balance sheet as a liability, along with a corresponding right of use asset. Currently under U.S. GAAP, lease arrangements that meet certain criteria are considered operating leases and are not recorded on the balance sheet. ASU No. 2016-02 also requires 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 the Company's consolidated financial statements. Financial Instruments Recognition and Measurement — In January 2016, the FASB issued ASU No. 2016-01, " Financial Instruments Overall - Recognition and Measurement of Financial Assets and Liabilities " ("ASU No. 2016-01") to address certain aspects of recognition, measurement, presentation, and disclosure of financial instruments. Among the significant changes required by ASU No. 2016-01 is that equity investments will be measured at fair value with changes in fair value recognized in net income. ASU No. 2016-01 will be effective for Gartner on January 1, 2018. We have evaluated the impact of ASU No. 2016-1 and we do not expect that it will have a material impact on Gartner's consolidated financial statements but may require additional disclosure. Revenue — In May 2014, the FASB issued ASU No. 2014-09, " Revenue from Contracts with Customers " ("ASU No. 2014-09"). ASU No. 2014-09 and related amendments require changes in revenue recognition policies as well as require enhanced disclosures. ASU No. 2014-09 is intended to clarify the principles for recognizing revenue by removing inconsistencies and weaknesses in existing revenue recognition rules; provide a more robust framework for addressing revenue recognition issues; improve comparability of revenue recognition practices across entities, industries, jurisdictions and capital markets; and provide more useful information to users of financial statements through improved revenue disclosures. ASU No. 2014-09 will be effective for Gartner on January 1, 2018, and the Company expects to complete its assessment of the estimated impact of ASU No. 2014-09 on its consolidated financial statements by the end of 2016. 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. On June 28, 2016, the Company acquired 100% of the outstanding capital stock of Newco 5CL Limited (which operates under the trade name "SCM World"), a privately-held firm based in London with 60 employees. SCM World is a leading cross-industry peer network and learning community providing subscription-based research and conferences for supply chain executives. The Company paid $34.2 million in cash held overseas at close. On a net basis, and for cash flow reporting purposes, the Company paid $28.3 million in cash at close for SCM World, which represents the gross cash paid of $34.2 million less cash held by SCM World at the acquisition date. The Company may also be required to pay up to an additional $15.0 million in cash for potential earn-out payments tied to the performance of SCM World through December 31, 2016. The potential payment under the earn-out and the related fair value of the earn-out payment were determined as of the acquisition date. The fair value of the earn-out on the acquisition date was recorded as part of the cost of the acquisition and will be adjusted to fair value at each reporting period through income until the final amount of the earn-out liability is determined as of December 31, 2016. Separately, the Company also determined on the date of the acquisition that it may also be required to pay up to an additional $8.0 million in cash contingent on the achievement of certain employment conditions by several key employees (who are also former shareholders) of SCM World, which is being recognized as an expense over the related service period of two years . During the three months ended September 30, 2016, the Company recorded $4.5 million of expense for the earn-out due to a change in its fair value and an additional $1.0 million for the achievement of certain employment conditions. The Company recorded $33.9 million of goodwill and amortizable intangible assets for SCM World (see Note 5—Goodwill and Intangible Assets for additional information) and an immaterial amount of other assets on a net basis as of the acquisition date. The valuation of the intangible assets and the overall allocation of the purchase price is preliminary, which the Company expects to finalize in the fourth quarter of 2016. The operating results and the related goodwill are being reported as part of the Company's Research and Events segments and goodwill resulting from the acquisition will not be deductible for tax purposes. Had the Company acquired SCM World in a prior period, the impact to the Company's results would not have been material, and as a result pro forma financial information for prior periods has not been provided. The Company recognized acquisition and integration charges of $16.6 million and $6.5 million in the three months ended September 30, 2016 and 2015, respectively, and $33.0 million and $15.3 million in the nine months ended September 30, 2016 and 2015, respectively. These charges are reported in the line Acquisition and integration charges in the Condensed Consolidated Statements of Operations and include amounts accrued for payments contingent on the achievement of certain performance targets and employment conditions, as well as legal, consulting, severance, and other costs. The Company paid $35.5 million in cash during the nine months ended September 30, 2016 for the achievement of certain employment conditions related to acquisitions completed in prior periods, of which $13.6 million was paid from escrow and $21.9 million was paid from Company cash. Separately, during the nine months ended September 30, 2016, the Company also paid $1.0 million in cash for a working capital settlement related to a 2015 acquisition.

Earnings per Share

Earnings per Share	9 Months Ended
	Sep. 30, 2016
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 Nine Months Ended September 30, September 30, 2016 2015 2016 2015 Numerator: Net income used for calculating basic and diluted earnings per common share $ 30,484 $ 30,366 $ 127,097 $ 109,872 Denominator: Weighted average number of common shares used in the calculation of basic earnings per share 82,638 82,989 82,549 84,244 Common stock equivalents associated with stock-based compensation plans (1) 1,165 1,124 1,212 1,191 Shares used in the calculation of diluted earnings per share 83,803 84,113 83,761 85,435 Basic earnings per share $ 0.37 $ 0.37 $ 1.54 $ 1.30 Diluted earnings per share $ 0.36 $ 0.36 $ 1.52 $ 1.29 (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 0.2 million in each of the periods presented.

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2016
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 September 30, 2016 , the Company had a total of 6.2 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. The Company adopted FASB ASU No. 2016-09, " Improvements to Employee Share-Based Payment Accounting," in the third quarter of 2016 . ASU No. 2016-09 requires certain changes in accounting for stock compensation under FASB ASC Topic No. 718. Among the changes required by ASU No. 2016-09 is that excess tax benefits or deficiencies resulting from stock-based compensation awards must be recognized in income tax expense in the Condensed Consolidated Statement of Operations. Prior to ASU No. 2016-09, excess tax benefits or deficiencies were recorded in additional paid-in capital in Stockholders' (Deficit) Equity in the Condensed Consolidated Balance Sheet. ASU No. 2016-09 also requires that excess tax benefits related to share-based awards to be reported as cash flows from operating activities along with all other income tax cash flows on the Condensed Consolidated Statement of Cash Flows; previously these excess tax benefits were reported as cash flows from financing activities. ASU No. 2016-09 allows companies to elect either a prospective or retrospective application for the cash flow classification change, for which the Company has elected to apply this classification amendment prospectively, effective January 1, 2016. ASU No. 2016-09 also permits companies to make an entity-wide accounting policy election to recognize forfeitures of stock-based compensation awards as they occur or make an estimate by applying a forfeiture rate each quarter. The Company previously estimated forfeitures but has optionally selected to change its accounting policy and account for forfeitures as they occur. Note 1 — Business and Basis of Presentation provides information regarding the impact of the adoption of ASU No. 2016-09. 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 Nine Months Ended September 30, September 30, Award type: 2016 2015 2016 2015 Stock appreciation rights $ 1.3 $ 1.1 $ 4.3 $ 4.5 Common stock equivalents 0.2 0.2 0.5 0.5 Restricted stock units 8.0 8.3 31.3 32.0 Total (1) $ 9.5 $ 9.6 $ 36.1 $ 37.0 Three Months Ended Nine Months Ended September 30, September 30, Amount recorded in: 2016 2015 2016 2015 Cost of services and product development $ 4.6 $ 4.5 $ 17.0 $ 16.1 Selling, general and administrative 4.9 5.1 19.1 20.9 Total (1) $ 9.5 $ 9.6 $ 36.1 $ 37.0 (1) Includes charges of $2.5 million and $3.0 million for the three months ended September 30, 2016 and 2015 , respectively, and $16.5 million and $17.4 million for the nine months ended September 30, 2016 and 2015, respectively, for awards to retirement-eligible employees since these awards vest on an accelerated basis. As of September 30, 2016 , the Company had $59.4 million of total unrecognized stock-based compensation cost, which is expected to be expensed over the remaining weighted-average service period of approximately 2.4 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 minimum 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 nine months ended September 30, 2016 : 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, 2015 1.3 $ 56.47 $ 14.92 4.46 Granted 0.4 80.06 16.50 6.36 Exercised (0.3 ) 42.22 13.45 n/a Outstanding at September 30, 2016 (1), (2) 1.4 $ 65.10 $ 15.60 4.54 Vested and exercisable at September 30, 2016 (2) 0.6 $ 53.33 $ 14.57 3.38 (1) As of September 30, 2016 , 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 September 30, 2016 had an intrinsic value of $32.4 million . SARs vested and exercisable had an intrinsic value of $20.7 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: Nine Months Ended September 30, 2016 2015 Expected dividend yield (1) — % — % Expected stock price volatility (2) 22 % 24 % Risk-free interest rate (3) 1.1 % 1.5 % Expected life in years (4) 4.4 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 nine months ended September 30, 2016 : Restricted Stock Units (RSUs) (in millions) Per Share Weighted Average Grant Date Fair Value Outstanding at December 31, 2015 1.4 $ 62.80 Granted (1) 0.6 81.39 Vested and released (0.6 ) 58.01 Forfeited (0.1 ) 69.02 Outstanding at September 30, 2016 (2), (3) 1.3 $ 73.17 (1) The 0.6 million RSUs granted consisted of 0.3 million performance-based RSUs awarded to executives and 0.3 million service-based RSUs awarded to non-executive employees and non-management board members. The 0.3 million 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 2016 . The final number of performance-based RSUs that will ultimately be awarded for 2016 ranges from 0% to 200% of the target amount, with the final number dependent on the actual increase in total contract value for 2016 as measured on December 31, 2016 . 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 1.3 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 nine months ended September 30, 2016 : Common Stock Equivalents (CSEs) Per Share Weighted Average Grant Date Fair Value Outstanding at December 31, 2015 105,664 $ 19.57 Granted 5,332 91.96 Converted to common shares upon grant (4,127 ) 91.96 Outstanding at September 30, 2016 106,869 $ 20.39 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 September 30, 2016 , the Company had 1.0 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 $6.9 million and $5.6 million in cash from purchases under the ESP Plan during the nine months ended September 30, 2016 and 2015 , respectively.

Segment Information

Segment Information	9 Months Ended
	Sep. 30, 2016
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 September 30, 2016 Research Consulting Events Consolidated Revenues $ 461,502 $ 79,082 $ 33,475 $ 574,059 Gross contribution 319,239 21,622 14,529 355,390 Corporate and other expenses (306,664 ) Operating income $ 48,726 Three Months Ended September 30, 2015 Research Consulting Events Consolidated Revenues $ 396,179 $ 74,686 $ 29,301 $ 500,166 Gross contribution 274,967 21,593 11,543 308,103 Corporate and other expenses (255,629 ) Operating income $ 52,474 Nine Months Ended September 30, 2016 Research Consulting Events Consolidated Revenues $ 1,350,943 $ 258,090 $ 132,290 $ 1,741,323 Gross contribution 941,113 84,273 63,574 1,088,960 Corporate and other expenses (892,506 ) Operating income $ 196,454 Nine Months Ended September 30, 2015 Research Consulting Events Consolidated Revenues $ 1,162,987 $ 239,814 $ 116,487 $ 1,519,288 Gross contribution 811,877 81,175 53,427 946,479 Corporate and other expenses (760,103 ) Operating income $ 186,376 The following table provides a reconciliation of total segment gross contribution to net income for the periods indicated (in thousands): Three Months Ended Nine Months Ended September 30, September 30, 2016 2015 2016 2015 Total segment gross contribution $ 355,390 $ 308,103 $ 1,088,960 $ 946,479 Costs and expenses: Cost of services and product development - unallocated (1) 4,453 1,539 14,222 9,050 Selling, general and administrative 269,902 236,355 799,322 703,868 Depreciation and amortization 15,752 11,247 46,004 31,922 Acquisition and integration charges 16,557 6,488 32,958 15,263 Operating income 48,726 52,474 196,454 186,376 Interest expense and other, net 3,978 682 14,208 10,832 Provision for income taxes 14,264 21,426 55,149 65,672 Net income $ 30,484 $ 30,366 $ 127,097 $ 109,872 (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	9 Months Ended
	Sep. 30, 2016
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 value of its reporting units relative to their respective carrying value, which indicated no impairment of recorded goodwill. The following table presents changes to the carrying amount of goodwill by reportable segment during the nine months ended September 30, 2016 (in thousands): Research Consulting Events Total Balance, December 31, 2015 (1) $ 575,292 $ 98,412 $ 41,655 $ 715,359 Additions due to acquisitions (2) 25,744 — 5,958 31,702 Foreign currency translation adjustments (2,291 ) (1,188 ) (656 ) (4,135 ) Balance, September 30, 2016 $ 598,745 $ 97,224 $ 46,957 $ 742,926 (1) The Company does not have any accumulated goodwill impairment losses. (2) The additions to goodwill include the acquisition of SCM World in June 2016 and certain measurement period working capital adjustments from a prior acquisition. Amortizable Intangible Assets The following tables present reconciliations of the carrying amounts of amortizable intangible assets as of the dates indicated (in thousands): September 30, 2016 Trade Name Customer Relationships Content Software Non-Compete Total Gross cost, December 31, 2015 $ 4,144 $ 62,860 $ 5,450 $ 16,219 $ 29,330 $ 118,003 Additions due to acquisitions (1) 302 2,769 1,039 — — 4,110 Intangibles fully amortized — — (162 ) (125 ) — (287 ) Foreign currency translation impact (49 ) (2,631 ) (3,416 ) 45 22 (6,029 ) Gross cost 4,397 62,998 2,911 16,139 29,352 115,797 Accumulated amortization (2), (3) (1,466 ) (14,312 ) (1,573 ) (7,617 ) (9,060 ) (34,028 ) Balance, September 30, 2016 $ 2,931 $ 48,686 $ 1,338 $ 8,522 $ 20,292 $ 81,769 December 31, 2015 Trade Name Customer Relationships Content Software Non-Compete Total Gross cost $ 4,144 $ 62,860 $ 5,450 $ 16,219 $ 29,330 $ 118,003 Accumulated amortization (2), (3) (681 ) (9,028 ) (3,525 ) (3,699 ) (4,526 ) (21,459 ) Balance, December 31, 2015 $ 3,463 $ 53,832 $ 1,925 $ 12,520 $ 24,804 $ 96,544 (1) The additions are for the acquisition of SCM World in June 2016. (2) Intangible assets are being amortized against earnings over the following periods: Trade name— 2 to 4 years ; Customer relationships— 4 to 7 years ; Content— 1.5 to 4 years ; Software— 3 years ; Non-compete— 3 to 5 years . (3) Aggregate amortization expense related to intangible assets was $6.2 million and $2.7 million for the three months ended September 30, 2016 and 2015 , respectively, and $18.6 million and $7.0 million for the nine months ended September 30, 2016 and 2015, respectively. The estimated future amortization expense by year from amortizable intangibles is as follows (in thousands): 2016 (remaining three months) $ 6,124 2017 22,722 2018 19,761 2019 14,958 2020 12,776 2021 5,428 Thereafter — $ 81,769

Debt

Debt	9 Months Ended
	Sep. 30, 2016
Debt Disclosure [Abstract]
Debt	Debt 2016 Credit Agreement On June 17, 2016, the Company entered into a new credit arrangement (the "2016 Credit Agreement”) with several lenders to take advantage of favorable financing conditions and to obtain greater flexibility through a larger revolving credit facility. The 2016 Credit Agreement provides for a $600.0 million secured five-year term loan and a $1.2 billion secured five-year revolving credit facility. The term loan and revolving credit facility may be increased, at the Company's option and under certain conditions, by up to an additional $500.0 million in the aggregate plus additional amounts subject to the satisfaction of certain conditions, including a maximum secured leverage ratio. The term loan will be repaid in 16 consecutive quarterly installments commencing September 30, 2016, plus a final payment due on June 17, 2021, and may be prepaid at any time without penalty or premium (other than applicable breakage costs) at the option of the Company. The revolving credit facility may be used for loans, and up to $50.0 million may be used for letters of credit. The revolving loans may be borrowed, repaid and re-borrowed until June 17, 2021, at which time all amounts borrowed must be repaid. The 2016 Credit Agreement contains certain customary restrictive loan covenants, with respect to which the Company was in full compliance as of September 30, 2016. In addition, the Company’s obligations under the 2016 Credit Agreement are guaranteed by certain existing and future direct and indirect U.S. subsidiaries (the “Subsidiary Guarantors”). The Company’s obligations and the Subsidiary Guarantor’s obligations are secured by first priority security interests in substantially all of the assets of the Company and the Subsidiary Guarantors, including pledges of all stock and other equity interests in direct subsidiaries owned by the Company and the Subsidiary Guarantors (but only up to 66% of the voting stock of each direct foreign subsidiary or foreign subsidiary holding company owned by Gartner or any Subsidiary Guarantor). The security and pledges are subject to certain exceptions. On June 17, 2016, the Company drew down $600.0 million in term loans and $200.0 million in revolving loans under the 2016 Credit Agreement which was used to pay down the amounts outstanding under the Company's prior credit arrangement, which was terminated. Additional amounts drawn down under the 2016 Credit Agreement will be used for general working capital purposes. The Company recorded $5.0 million in deferred financing fees related to the 2016 Credit Agreement, which will be amortized to Interest expense, net in the Condensed Consolidated Statement of Operations. The Company also recorded a $1.3 million charge in the nine months ended September 30, 2016 in connection with the new credit arrangement for the write-off of fees from a previous financing, which was recorded in Interest expense, net. Amounts borrowed under the 2016 Credit Agreement bear interest at a rate equal to, at Gartner’s option, either: (1) the greatest of: (i) the Administrative Agent’s prime rate; (ii) the average rate on overnight federal funds plus 1/2 of 1%; (iii) and the eurodollar rate (adjusted for statutory reserves) plus 1% , in each case plus a margin equal to between 0.125% and 1.0% depending on Gartner’s consolidated leverage ratio as of the end of the four consecutive fiscal quarters most recently ended; or (2) the eurodollar rate (adjusted for statutory reserves) plus a margin equal to between 1.125% and 2.0% , depending on Gartner’s leverage ratio as of the end of the four consecutive fiscal quarters most recently ended. The Company’s total outstanding borrowings for the periods indicated were as follows (in thousands): Balance Balance September 30, December 31, Description: 2016 2015 Term loans (1) $ 592,500 $ 380,000 Revolver loans (1), (2) 147,500 440,000 Other (3) 5,000 5,000 Subtotal (4) $ 745,000 $ 825,000 Less: deferred financing fees (5) (8,595 ) — Net carrying amount $ 736,405 $ 825,000 (1) The contractual annualized interest rate as of September 30, 2016 on both the term loan and the revolver was 1.90% , which consisted of a floating eurodollar base rate of 0.52% plus a margin of 1.38% . However, the Company has outstanding interest rate swap contracts, accounted for as cash flow hedges, which effectively convert the floating eurodollar base rates to a fixed base rate on $700.0 million of borrowings (see below). (2) The Company had $1.05 billion of available borrowing capacity on the revolver (not including the expansion feature) as of September 30, 2016 . (3) Consists of a $5.0 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. The loan has a principal forgiveness provision in which up to $2.5 million of the loan may be forgiven if the Company meets certain employment targets during the first five years of the loan. In October 2016, the Company was notified that it had met these targets and was entitled to a loan forgiveness credit of $2.5 million, which will be recognized in the fourth quarter of 2016. (4) The average annual effective rate on the Company's total debt outstanding for the nine months ended September 30, 2016 , including the effect of the interest rate swaps discussed below, was approximately 2.77% . (5) Includes $5.0 million of deferred financing fees related to the 2016 Credit Agreement and fees previously classified in Other Assets. The fees are being amortized to Interest Expense, net over the term of the 2016 Credit Agreement. Interest Rate Swaps The Company has three fixed-for-floating interest rate swap contracts which it designates as accounting hedges of the forecasted interest payments on $700.0 million of the Company’s variable rate borrowings. The Company pays base fixed rates on these three swaps ranging from 1.53% to 1.60% and in return receives a floating eurodollar base rate on $700.0 million of 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 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 September 30, 2016 . The interest rate swaps had a total negative fair value (liability) to the Company of $14.9 million at September 30, 2016 , which is deferred and recorded in Accumulated other comprehensive loss, net of tax effect. Letters of Credit The Company had $3.8 million of letters of credit outstanding at September 30, 2016 . The Company enters into these instruments in the ordinary course of business to facilitate transactions with customers and others.

Equity

Equity	9 Months Ended
	Sep. 30, 2016
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 $1.11 billion remained available as of September 30, 2016. 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 Nine Months Ended September 30, September 30, 2016 2015 2016 2015 Number of shares repurchased (1) 9,882 210,012 542,792 5,538,612 Cash paid for repurchased shares (in thousands) (2) $ 922 $ 11,558 $ 52,889 $ 453,000 (1) The average purchase price for repurchased shares was $93.33 and $84.17 for the three and nine months ended September 30, 2016 , respectively, and $83.79 and $82.40 for the three and nine months ended September 30, 2015, respectively. (2) The cash paid for the nine months ended September 30, 2016 includes $7.2 million for share repurchases that were executed in late December 2015 and were settled in early January 2016. 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 September 30, 2016 : Interest Rate Swaps Defined Benefit Pension Plans Foreign Currency Translation Adjustments Total Balance - June 30, 2016 $ (12,158 ) $ (4,757 ) $ (31,088 ) $ (48,003 ) Changes during the period: Change in AOCL/I before reclassifications to income 2,076 — (3,032 ) (956 ) Reclassifications from AOCL/I to income during the period (2), (3) 1,138 37 — 1,175 Other comprehensive income (loss) for the period 3,214 37 (3,032 ) 219 Balance – September 30, 2016 $ (8,944 ) $ (4,720 ) $ (34,120 ) $ (47,784 ) For the three months ended September 30, 2015 : Interest Rate Defined Foreign Total Balance – June 30, 2015 $ (2,410 ) $ (5,922 ) $ (27,285 ) $ (35,617 ) Changes during the period: Change in AOCL/I before reclassifications to income (7,457 ) — (7,900 ) (15,357 ) Reclassifications from AOCL/I to income during the period (2), (3) 1,647 53 — 1,700 Other comprehensive (loss) income for the period (5,810 ) 53 (7,900 ) (13,657 ) Balance – September 30, 2015 $ (8,220 ) $ (5,869 ) $ (35,185 ) $ (49,274 ) For the nine months ended September 30, 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 (9,376 ) — 2,371 (7,005 ) Reclassifications from AOCL/I to income during the period (2), (3) 3,511 112 — 3,623 Other comprehensive (loss) income for the period (5,865 ) 112 2,371 (3,382 ) Balance – September 30, 2016 $ (8,944 ) $ (4,720 ) $ (34,120 ) $ (47,784 ) For the nine months ended September 30, 2015: Interest Rate Defined Foreign Total Balance – December 31, 2014 $ (1,740 ) $ (6,028 ) $ (13,402 ) $ (21,170 ) Changes during the period: Change in AOCL/I before reclassifications to income (9,910 ) — (21,783 ) (31,693 ) Reclassifications from AOCL/I to income during the period (2), (3) 3,430 159 — 3,589 Other comprehensive (loss) income for the period (6,480 ) 159 (21,783 ) (28,104 ) Balance – September 30, 2015 $ (8,220 ) $ (5,869 ) $ (35,185 ) $ (49,274 ) (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 9 – 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 11 – Employee Benefits for information regarding the Company’s defined benefit pension plans.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2016
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The provision for income taxes was $14.3 million for the three months ended September 30, 2016 compared to $21.4 million in the three months ended September 30, 2015 . The effective income tax rate was 31.9% for the three months ended September 30, 2016 and 41.4% for the same period in 2015 . The quarter-over-quarter decrease in the effective income tax rate was primarily attributable t o the early adoption of ASU No. 2016-09, an estimated greater percentage of 2016 pretax income being earned in lower tax countries, and an increase in federal R&D credits partially offset by increases in non-deductible expenses relating to acquisitions. The provision for income taxes was $55.1 million for the nine months ended September 30, 2016 compared to $65.7 million in the nine months ended September 30, 2015 . The effective income tax rate was 30.3% for the nine months ended September 30, 2016 and 37.4% for the same period in 2015 . The decrease in the effective income tax rate for the nine months ended September 30, 2016 was primarily attributable to the same factors as the quarter-over-quarter results. As disclosed in Note 1 — Business and Basis of Presentation, the Company adopted FASB ASU No. 2016-09 in the third quarter of 2016. The effect of the adoption reduced the provision for income taxes by $0.5 million and $9.0 million for the three and nine months ended September 30, 2016, respectively. As of September 30, 2016 and December 31, 2015 , the Company had gross unrecognized tax benefits of $31.8 million and $25.9 million , respectively. It is reasonably possible that gross unrecognized tax benefits will decrease by approximately $2.5 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 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	9 Months Ended
	Sep. 30, 2016
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): September 30, 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 $ (14,907 ) Other liabilities $ (8,944 ) Foreign currency forwards (2) 16 23,089 (67 ) Accrued liabilities — Total 19 $ 723,089 $ (14,974 ) $ (8,944 ) December 31, 2015 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 $ (5,132 ) Other liabilities $ (3,079 ) Foreign currency forwards (2) 102 193,610 235 Accrued liabilities — Total 105 $ 893,610 $ (4,897 ) $ (3,079 ) (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 6 — 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 September 30, 2016 matured by the end of October 2016. (3) See Note 10 — Fair Value Disclosures for the determination of the fair value of these instruments. At September 30, 2016 , 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 Nine Months Ended September 30, September 30, Amount recorded in: 2016 2015 2016 2015 Interest expense, net (1) $ 1,895 $ 2,762 $ 5,851 $ 6,094 Other (income) expense, net (2) (814 ) (369 ) (239 ) 74 Total expense, net $ 1,081 $ 2,393 $ 5,612 $ 6,168 (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	9 Months Ended
	Sep. 30, 2016
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 variable rate 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 5 — 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: September 30, December 31, Assets: Values based on Level 1 inputs: Deferred compensation plan assets (1) $ 10,051 $ 8,671 Total Level 1 inputs 10,051 8,671 Values based on Level 2 inputs: Deferred compensation plan assets (1) 26,997 25,474 Foreign currency forward contracts (2) 58 610 Total Level 2 inputs 27,055 26,084 Total Assets $ 37,106 $ 34,755 Liabilities: Values based on Level 2 inputs: Deferred compensation plan liabilities (1) $ 42,060 $ 39,071 Foreign currency forward contracts (2) 125 375 Interest rate swap contracts (3) 14,907 5,132 Total Level 2 inputs 57,092 44,578 Total Liabilities $ 57,092 $ 44,578 (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 6 — 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	9 Months Ended
	Sep. 30, 2016
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 $0.9 million and $2.4 million for the three and nine months ended September 30, 2016 , respectively, and $0.8 million and $2.3 million for the three and nine months ended September 30, 2015, respectively.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2016
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 September 30, 2016 , the Company did not have any material payment obligations under any such indemnification agreements.

Business and Basis of Present19

Business and Basis of Presentation (Policies)	9 Months Ended
	Sep. 30, 2016
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, 2015 . The fiscal year of Gartner is the twelve-month calendar period from January 1 through December 31. In the opinion of management, all normal recurring accruals and adjustments considered necessary for a fair presentation of financial position, results of operations and cash flows at the dates and for the periods presented herein have been included. The results of operations for the three and nine months ended September 30, 2016 may not be indicative of the results of operations for the remainder of 2016 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 continuously evaluates and revises its estimates using historical experience and other factors, including the general economic environment and actions it may take in the future. Management adjusts these estimates when facts and circumstances dictate. However, these estimates may involve significant uncertainties and judgments and cannot be determined with precision. In addition, these estimates are based on management’s best judgment at a point in time. As a result, differences between our estimates and actual results could be material and would be reflected in the Company’s consolidated financial statements in future periods.
Adoption of new accounting standard	Adoption of new accounting standards. The Company has recently adopted the following accounting standard: Stock-Based Compensation Accounting — The Company adopted FASB Accounting Standards Update (ASU) 2016-09, " Improvements to Employee Share-Based Payment Accounting" ("ASU No. 2016-09"), in the third quarter of 2016. While the required effective date for the adoption of this amendment for Gartner is January 1, 2017, the Company elected to early adopt ASU No. 2016-09, as permitted by the amendment. ASU No. 2016-09 requires changes in accounting for stock-based compensation, some of which must be applied to the beginning of the Company's current fiscal year, January 1, 2016. Among the changes required by ASU No. 2016-09 is that excess tax benefits or deficiencies resulting from stock-based compensation awards must be recognized in income tax expense in the Company’s Condensed Consolidated Statements of Operations. Prior to ASU No. 2016-09, excess tax benefits or deficiencies were recorded in additional paid-in capital in Stockholders' (Deficit) Equity in the Condensed Consolidated Balance Sheet. ASU No. 2016-09 requires companies to apply this amendment from the beginning of the fiscal year in which it is adopted. Accordingly, this provision is effective for Gartner beginning January 1, 2016. As a result, our previously reported income tax expense, net income, earnings per share, and accumulated earnings for the six months ended June 30, 2016 have been adjusted, and the table below summarizes these changes. As disclosed in the table, the adoption of ASU No. 2016-09 increased both our basic and diluted earnings per share for the six months ended June 30, 2016 by $0.10 per share. For the three and nine months ended September 30, 2016, the adoption of ASU No. 2016-09 increased both basic and diluted earnings per share by $0.01 and $0.11 per share, respectively. ASU No. 2016-09 also requires excess tax benefits related to stock-based compensation awards to be reported as cash flows from operating activities along with all other income tax cash flows on the Condensed Consolidated Statement of Cash Flows. Previously these excess tax benefits were reported as cash flows from financing activities on the Condensed Consolidated Statement of Cash Flows. ASU No. 2016-09 allows companies to elect either a prospective or retrospective application for the cash flow classification change, for which the Company has elected to apply this classification amendment prospectively, effective January 1, 2016. As a result, approximately $8.5 million in excess tax benefits previously reported as cash flows from financing activities on the Condensed Consolidated Statement of Cash Flows for the six months ended June 30, 2016 have been reclassified as cash flows from operating activities. The table below summarizes these retroactive changes. The Company also recorded an additional $0.5 million of excess tax benefits in the three months ended September 30, 2016 for stock-based compensation awards, resulting in a total excess tax benefit for the nine months ended September 30, 2016 of approximately $9.0 million. ASU No. 2016-09 also permits companies to make an entity-wide accounting policy election to recognize forfeitures of share-based awards as they occur or make an estimate by applying a forfeiture rate each quarter. The Company previously estimated forfeitures but has optionally selected to change its accounting policy and account for forfeitures as they occur. ASU No. 2016-09 requires this change in accounting policy to be applied using a cumulative-effect adjustment to accumulated earnings as of the beginning of the period in which the rule is adopted. Accordingly, the Company has adjusted its opening accumulated earnings effective January 1, 2016 and as a result the previously reported accumulated earnings balances as of March 31, 2016 and June 30, 2016 have been impacted. The table below summarizes these retroactive changes. The following table summarizes the retroactive impact of the adoption of ASU 2016-09 for the periods indicated (in thousands, except earnings per share data): Three Months Ended Three Months Ended Six Months Ended March 31, 2016 June 30, 2016 June 30, 2016 As Originally Reported Adjusted As Originally Reported Adjusted As Originally Reported Adjusted Provision for income taxes $ 20,140 $ 15,320 $ 29,280 $ 25,565 $ 49,420 $ 40,884 Net income 40,167 44,987 47,911 51,626 88,078 96,614 Basic earnings per share 0.49 0.55 0.58 0.63 1.07 1.17 Diluted earnings per share (1) 0.48 0.54 0.57 0.62 1.05 1.15 Operating cash flow 8,580 13,331 144,734 148,452 153,314 161,783 Accumulated earnings $ 1,490,851 $ 1,495,411 $ 1,538,762 $ 1,547,037 $ 1,538,762 $ 1,547,037 (1) ASU No. 2016-09 requires certain changes in the calculation of diluted shares. The impact of applying these changes was not significant. Accounting standards issued but not yet adopted. The FASB has issued several accounting standards that have not yet become effective and that may impact the Company’s consolidated financial statements or related disclosures in future periods. These standards and their potential impact are discussed below: 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, with early adoption permitted. We have evaluated the impact of ASU No. 2016-15 and we do not expect that it will have a material impact on Gartner's consolidated financial statements. Financial Instrument Credit Losses — In June 2016, the FASB issued ASU No. 2016-13, " Financial Instruments—Credit Losses" ("ASU No. 2016-13"). ASU No. 2016-13 amends the current financial instrument impairment model by requiring entities to use a forward-looking approach based on expected losses to estimate credit losses on certain types of financial instruments, including trade receivables. ASU No. 2016-13 is effective for Gartner on January 1, 2020, with early adoption permitted. We are currently evaluating the potential impact of ASU No. 2016-13 on the Company's consolidated financial statements. Leases — In February 2016, the FASB issued ASU No. 2016-02, " Leases " ("ASU No. 2016-02") which will require significant changes in the accounting and disclosure of lease arrangements. Among the significant changes required by ASU No. 2016-02 is that almost all lease obligations will be recorded on the balance sheet as a liability, along with a corresponding right of use asset. Currently under U.S. GAAP, lease arrangements that meet certain criteria are considered operating leases and are not recorded on the balance sheet. ASU No. 2016-02 also requires 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 the Company's consolidated financial statements. Financial Instruments Recognition and Measurement — In January 2016, the FASB issued ASU No. 2016-01, " Financial Instruments Overall - Recognition and Measurement of Financial Assets and Liabilities " ("ASU No. 2016-01") to address certain aspects of recognition, measurement, presentation, and disclosure of financial instruments. Among the significant changes required by ASU No. 2016-01 is that equity investments will be measured at fair value with changes in fair value recognized in net income. ASU No. 2016-01 will be effective for Gartner on January 1, 2018. We have evaluated the impact of ASU No. 2016-1 and we do not expect that it will have a material impact on Gartner's consolidated financial statements but may require additional disclosure. Revenue — In May 2014, the FASB issued ASU No. 2014-09, " Revenue from Contracts with Customers " ("ASU No. 2014-09"). ASU No. 2014-09 and related amendments require changes in revenue recognition policies as well as require enhanced disclosures. ASU No. 2014-09 is intended to clarify the principles for recognizing revenue by removing inconsistencies and weaknesses in existing revenue recognition rules; provide a more robust framework for addressing revenue recognition issues; improve comparability of revenue recognition practices across entities, industries, jurisdictions and capital markets; and provide more useful information to users of financial statements through improved revenue disclosures. ASU No. 2014-09 will be effective for Gartner on January 1, 2018, and the Company expects to complete its assessment of the estimated impact of ASU No. 2014-09 on its consolidated financial statements by the end of 2016. 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.

Business and Basis of Present20

Business and Basis of Presentation Business and Basis of Presentation (Tables)	9 Months Ended
	Sep. 30, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of New Accounting Pronouncements and Changes in Accounting Principles	The following table summarizes the retroactive impact of the adoption of ASU 2016-09 for the periods indicated (in thousands, except earnings per share data): Three Months Ended Three Months Ended Six Months Ended March 31, 2016 June 30, 2016 June 30, 2016 As Originally Reported Adjusted As Originally Reported Adjusted As Originally Reported Adjusted Provision for income taxes $ 20,140 $ 15,320 $ 29,280 $ 25,565 $ 49,420 $ 40,884 Net income 40,167 44,987 47,911 51,626 88,078 96,614 Basic earnings per share 0.49 0.55 0.58 0.63 1.07 1.17 Diluted earnings per share (1) 0.48 0.54 0.57 0.62 1.05 1.15 Operating cash flow 8,580 13,331 144,734 148,452 153,314 161,783 Accumulated earnings $ 1,490,851 $ 1,495,411 $ 1,538,762 $ 1,547,037 $ 1,538,762 $ 1,547,037 (1) ASU No. 2016-09 requires certain changes in the calculation of diluted shares. The impact of applying these changes was not significant.

Earnings per Share (Tables)

Earnings per Share (Tables)	9 Months Ended
	Sep. 30, 2016
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 Nine Months Ended September 30, September 30, 2016 2015 2016 2015 Numerator: Net income used for calculating basic and diluted earnings per common share $ 30,484 $ 30,366 $ 127,097 $ 109,872 Denominator: Weighted average number of common shares used in the calculation of basic earnings per share 82,638 82,989 82,549 84,244 Common stock equivalents associated with stock-based compensation plans (1) 1,165 1,124 1,212 1,191 Shares used in the calculation of diluted earnings per share 83,803 84,113 83,761 85,435 Basic earnings per share $ 0.37 $ 0.37 $ 1.54 $ 1.30 Diluted earnings per share $ 0.36 $ 0.36 $ 1.52 $ 1.29 (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 0.2 million in each of the periods presented.

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2016
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 Nine Months Ended September 30, September 30, Award type: 2016 2015 2016 2015 Stock appreciation rights $ 1.3 $ 1.1 $ 4.3 $ 4.5 Common stock equivalents 0.2 0.2 0.5 0.5 Restricted stock units 8.0 8.3 31.3 32.0 Total (1) $ 9.5 $ 9.6 $ 36.1 $ 37.0
Schedule of stock-based compensation expense by expense category	Three Months Ended Nine Months Ended September 30, September 30, Amount recorded in: 2016 2015 2016 2015 Cost of services and product development $ 4.6 $ 4.5 $ 17.0 $ 16.1 Selling, general and administrative 4.9 5.1 19.1 20.9 Total (1) $ 9.5 $ 9.6 $ 36.1 $ 37.0 (1) Includes charges of $2.5 million and $3.0 million for the three months ended September 30, 2016 and 2015 , respectively, and $16.5 million and $17.4 million for the nine months ended September 30, 2016 and 2015, 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: Nine Months Ended September 30, 2016 2015 Expected dividend yield (1) — % — % Expected stock price volatility (2) 22 % 24 % Risk-free interest rate (3) 1.1 % 1.5 % Expected life in years (4) 4.4 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 nine months ended September 30, 2016 : 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, 2015 1.3 $ 56.47 $ 14.92 4.46 Granted 0.4 80.06 16.50 6.36 Exercised (0.3 ) 42.22 13.45 n/a Outstanding at September 30, 2016 (1), (2) 1.4 $ 65.10 $ 15.60 4.54 Vested and exercisable at September 30, 2016 (2) 0.6 $ 53.33 $ 14.57 3.38 (1) As of September 30, 2016 , 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 September 30, 2016 had an intrinsic value of $32.4 million . SARs vested and exercisable had an intrinsic value of $20.7 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 nine months ended September 30, 2016 : Restricted Stock Units (RSUs) (in millions) Per Share Weighted Average Grant Date Fair Value Outstanding at December 31, 2015 1.4 $ 62.80 Granted (1) 0.6 81.39 Vested and released (0.6 ) 58.01 Forfeited (0.1 ) 69.02 Outstanding at September 30, 2016 (2), (3) 1.3 $ 73.17 (1) The 0.6 million RSUs granted consisted of 0.3 million performance-based RSUs awarded to executives and 0.3 million service-based RSUs awarded to non-executive employees and non-management board members. The 0.3 million 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 2016 . The final number of performance-based RSUs that will ultimately be awarded for 2016 ranges from 0% to 200% of the target amount, with the final number dependent on the actual increase in total contract value for 2016 as measured on December 31, 2016 . 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 1.3 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 nine months ended September 30, 2016 : Common Stock Equivalents (CSEs) Per Share Weighted Average Grant Date Fair Value Outstanding at December 31, 2015 105,664 $ 19.57 Granted 5,332 91.96 Converted to common shares upon grant (4,127 ) 91.96 Outstanding at September 30, 2016 106,869 $ 20.39

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2016
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 September 30, 2016 Research Consulting Events Consolidated Revenues $ 461,502 $ 79,082 $ 33,475 $ 574,059 Gross contribution 319,239 21,622 14,529 355,390 Corporate and other expenses (306,664 ) Operating income $ 48,726 Three Months Ended September 30, 2015 Research Consulting Events Consolidated Revenues $ 396,179 $ 74,686 $ 29,301 $ 500,166 Gross contribution 274,967 21,593 11,543 308,103 Corporate and other expenses (255,629 ) Operating income $ 52,474 Nine Months Ended September 30, 2016 Research Consulting Events Consolidated Revenues $ 1,350,943 $ 258,090 $ 132,290 $ 1,741,323 Gross contribution 941,113 84,273 63,574 1,088,960 Corporate and other expenses (892,506 ) Operating income $ 196,454 Nine Months Ended September 30, 2015 Research Consulting Events Consolidated Revenues $ 1,162,987 $ 239,814 $ 116,487 $ 1,519,288 Gross contribution 811,877 81,175 53,427 946,479 Corporate and other expenses (760,103 ) Operating income $ 186,376
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 Nine Months Ended September 30, September 30, 2016 2015 2016 2015 Total segment gross contribution $ 355,390 $ 308,103 $ 1,088,960 $ 946,479 Costs and expenses: Cost of services and product development - unallocated (1) 4,453 1,539 14,222 9,050 Selling, general and administrative 269,902 236,355 799,322 703,868 Depreciation and amortization 15,752 11,247 46,004 31,922 Acquisition and integration charges 16,557 6,488 32,958 15,263 Operating income 48,726 52,474 196,454 186,376 Interest expense and other, net 3,978 682 14,208 10,832 Provision for income taxes 14,264 21,426 55,149 65,672 Net income $ 30,484 $ 30,366 $ 127,097 $ 109,872 (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)	9 Months Ended
	Sep. 30, 2016
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 nine months ended September 30, 2016 (in thousands): Research Consulting Events Total Balance, December 31, 2015 (1) $ 575,292 $ 98,412 $ 41,655 $ 715,359 Additions due to acquisitions (2) 25,744 — 5,958 31,702 Foreign currency translation adjustments (2,291 ) (1,188 ) (656 ) (4,135 ) Balance, September 30, 2016 $ 598,745 $ 97,224 $ 46,957 $ 742,926 (1) The Company does not have any accumulated goodwill impairment losses. (2) The additions to goodwill include the acquisition of SCM World in June 2016 and certain measurement period working capital adjustments from a prior acquisition.
Schedule of amortizable intangible assets	The following tables present reconciliations of the carrying amounts of amortizable intangible assets as of the dates indicated (in thousands): September 30, 2016 Trade Name Customer Relationships Content Software Non-Compete Total Gross cost, December 31, 2015 $ 4,144 $ 62,860 $ 5,450 $ 16,219 $ 29,330 $ 118,003 Additions due to acquisitions (1) 302 2,769 1,039 — — 4,110 Intangibles fully amortized — — (162 ) (125 ) — (287 ) Foreign currency translation impact (49 ) (2,631 ) (3,416 ) 45 22 (6,029 ) Gross cost 4,397 62,998 2,911 16,139 29,352 115,797 Accumulated amortization (2), (3) (1,466 ) (14,312 ) (1,573 ) (7,617 ) (9,060 ) (34,028 ) Balance, September 30, 2016 $ 2,931 $ 48,686 $ 1,338 $ 8,522 $ 20,292 $ 81,769 December 31, 2015 Trade Name Customer Relationships Content Software Non-Compete Total Gross cost $ 4,144 $ 62,860 $ 5,450 $ 16,219 $ 29,330 $ 118,003 Accumulated amortization (2), (3) (681 ) (9,028 ) (3,525 ) (3,699 ) (4,526 ) (21,459 ) Balance, December 31, 2015 $ 3,463 $ 53,832 $ 1,925 $ 12,520 $ 24,804 $ 96,544 (1) The additions are for the acquisition of SCM World in June 2016. (2) Intangible assets are being amortized against earnings over the following periods: Trade name— 2 to 4 years ; Customer relationships— 4 to 7 years ; Content— 1.5 to 4 years ; Software— 3 years ; Non-compete— 3 to 5 years . (3) Aggregate amortization expense related to intangible assets was $6.2 million and $2.7 million for the three months ended September 30, 2016 and 2015 , respectively, and $18.6 million and $7.0 million for the nine months ended September 30, 2016 and 2015, respectively.
Schedule of estimated future amortization expense by year	The estimated future amortization expense by year from amortizable intangibles is as follows (in thousands): 2016 (remaining three months) $ 6,124 2017 22,722 2018 19,761 2019 14,958 2020 12,776 2021 5,428 Thereafter — $ 81,769

Debt (Tables)

Debt (Tables)	9 Months Ended
	Sep. 30, 2016
Debt Disclosure [Abstract]
Schedule of debt	The Company’s total outstanding borrowings for the periods indicated were as follows (in thousands): Balance Balance September 30, December 31, Description: 2016 2015 Term loans (1) $ 592,500 $ 380,000 Revolver loans (1), (2) 147,500 440,000 Other (3) 5,000 5,000 Subtotal (4) $ 745,000 $ 825,000 Less: deferred financing fees (5) (8,595 ) — Net carrying amount $ 736,405 $ 825,000 (1) The contractual annualized interest rate as of September 30, 2016 on both the term loan and the revolver was 1.90% , which consisted of a floating eurodollar base rate of 0.52% plus a margin of 1.38% . However, the Company has outstanding interest rate swap contracts, accounted for as cash flow hedges, which effectively convert the floating eurodollar base rates to a fixed base rate on $700.0 million of borrowings (see below). (2) The Company had $1.05 billion of available borrowing capacity on the revolver (not including the expansion feature) as of September 30, 2016 . (3) Consists of a $5.0 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. The loan has a principal forgiveness provision in which up to $2.5 million of the loan may be forgiven if the Company meets certain employment targets during the first five years of the loan. In October 2016, the Company was notified that it had met these targets and was entitled to a loan forgiveness credit of $2.5 million, which will be recognized in the fourth quarter of 2016. (4) The average annual effective rate on the Company's total debt outstanding for the nine months ended September 30, 2016 , including the effect of the interest rate swaps discussed below, was approximately 2.77% . (5) Includes $5.0 million of deferred financing fees related to the 2016 Credit Agreement and fees previously classified in Other Assets. The fees are being amortized to Interest Expense, net over the term of the 2016 Credit Agreement.

Equity (Tables)

Equity (Tables)	9 Months Ended
	Sep. 30, 2016
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 Nine Months Ended September 30, September 30, 2016 2015 2016 2015 Number of shares repurchased (1) 9,882 210,012 542,792 5,538,612 Cash paid for repurchased shares (in thousands) (2) $ 922 $ 11,558 $ 52,889 $ 453,000 (1) The average purchase price for repurchased shares was $93.33 and $84.17 for the three and nine months ended September 30, 2016 , respectively, and $83.79 and $82.40 for the three and nine months ended September 30, 2015, respectively. (2) The cash paid for the nine months ended September 30, 2016 includes $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 September 30, 2016 : Interest Rate Swaps Defined Benefit Pension Plans Foreign Currency Translation Adjustments Total Balance - June 30, 2016 $ (12,158 ) $ (4,757 ) $ (31,088 ) $ (48,003 ) Changes during the period: Change in AOCL/I before reclassifications to income 2,076 — (3,032 ) (956 ) Reclassifications from AOCL/I to income during the period (2), (3) 1,138 37 — 1,175 Other comprehensive income (loss) for the period 3,214 37 (3,032 ) 219 Balance – September 30, 2016 $ (8,944 ) $ (4,720 ) $ (34,120 ) $ (47,784 ) For the three months ended September 30, 2015 : Interest Rate Defined Foreign Total Balance – June 30, 2015 $ (2,410 ) $ (5,922 ) $ (27,285 ) $ (35,617 ) Changes during the period: Change in AOCL/I before reclassifications to income (7,457 ) — (7,900 ) (15,357 ) Reclassifications from AOCL/I to income during the period (2), (3) 1,647 53 — 1,700 Other comprehensive (loss) income for the period (5,810 ) 53 (7,900 ) (13,657 ) Balance – September 30, 2015 $ (8,220 ) $ (5,869 ) $ (35,185 ) $ (49,274 ) For the nine months ended September 30, 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 (9,376 ) — 2,371 (7,005 ) Reclassifications from AOCL/I to income during the period (2), (3) 3,511 112 — 3,623 Other comprehensive (loss) income for the period (5,865 ) 112 2,371 (3,382 ) Balance – September 30, 2016 $ (8,944 ) $ (4,720 ) $ (34,120 ) $ (47,784 ) For the nine months ended September 30, 2015: Interest Rate Defined Foreign Total Balance – December 31, 2014 $ (1,740 ) $ (6,028 ) $ (13,402 ) $ (21,170 ) Changes during the period: Change in AOCL/I before reclassifications to income (9,910 ) — (21,783 ) (31,693 ) Reclassifications from AOCL/I to income during the period (2), (3) 3,430 159 — 3,589 Other comprehensive (loss) income for the period (6,480 ) 159 (21,783 ) (28,104 ) Balance – September 30, 2015 $ (8,220 ) $ (5,869 ) $ (35,185 ) $ (49,274 ) (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 9 – 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 11 – Employee Benefits for information regarding the Company’s defined benefit pension plans.

Derivatives and Hedging (Tables

Derivatives and Hedging (Tables)	9 Months Ended
	Sep. 30, 2016
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): September 30, 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 $ (14,907 ) Other liabilities $ (8,944 ) Foreign currency forwards (2) 16 23,089 (67 ) Accrued liabilities — Total 19 $ 723,089 $ (14,974 ) $ (8,944 ) December 31, 2015 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 $ (5,132 ) Other liabilities $ (3,079 ) Foreign currency forwards (2) 102 193,610 235 Accrued liabilities — Total 105 $ 893,610 $ (4,897 ) $ (3,079 ) (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 6 — 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 September 30, 2016 matured by the end of October 2016. (3) See Note 10 — 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 Nine Months Ended September 30, September 30, Amount recorded in: 2016 2015 2016 2015 Interest expense, net (1) $ 1,895 $ 2,762 $ 5,851 $ 6,094 Other (income) expense, net (2) (814 ) (369 ) (239 ) 74 Total expense, net $ 1,081 $ 2,393 $ 5,612 $ 6,168 (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)	9 Months Ended
	Sep. 30, 2016
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: September 30, December 31, Assets: Values based on Level 1 inputs: Deferred compensation plan assets (1) $ 10,051 $ 8,671 Total Level 1 inputs 10,051 8,671 Values based on Level 2 inputs: Deferred compensation plan assets (1) 26,997 25,474 Foreign currency forward contracts (2) 58 610 Total Level 2 inputs 27,055 26,084 Total Assets $ 37,106 $ 34,755 Liabilities: Values based on Level 2 inputs: Deferred compensation plan liabilities (1) $ 42,060 $ 39,071 Foreign currency forward contracts (2) 125 375 Interest rate swap contracts (3) 14,907 5,132 Total Level 2 inputs 57,092 44,578 Total Liabilities $ 57,092 $ 44,578 (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 6 — 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 Present29

Business and Basis of Presentation (Details)	Jun. 28, 2016USD ($)employee	Sep. 30, 2016USD ($)	Sep. 30, 2015USD ($)	Sep. 30, 2016USD ($)segment	Sep. 30, 2015USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of reportable segments | segment				3
Business Acquisition [Line Items]
Increase (decrease) in contingent consideration				$ 35,500,000
Acquisition and integration charges		$ 16,557,000	$ 6,488,000	32,958,000	$ 15,263,000
Acquisitions - increase in restricted cash (escrow)				13,600,000
Contingent consideration cash payment				21,900,000
Business combination, working capital adjustment, adjustment				$ 1,000,000
SCM World
Business Acquisition [Line Items]
Percentage of stock acquired	100.00%
Number of employees | employee	60
Payments to acquire businesses	$ 34,200,000
Payments to acquire businesses, net of cash acquired	28,300,000
Goodwill and intangible assets acquired	33,900,000
Other assets acquired	0
Contingent Consideration, Earn-out | SCM World
Business Acquisition [Line Items]
Increase (decrease) in contingent consideration		4,500,000
Maximum contingent consideration	15,000,000
Contingent Consideration, Employee Conditions | SCM World
Business Acquisition [Line Items]
Increase (decrease) in contingent consideration		$ 1,000,000
Maximum contingent consideration	$ 8,000,000
Maximum contingent consideration, period of expense recognition	2 years

Business and Basis of Present30

Business and Basis of Presentation - New Accounting Pronouncements (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended	9 Months Ended
	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Sep. 30, 2015	Jun. 30, 2016	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Basic earnings per share (in dollars per share)	$ 0.37	$ 0.63	$ 0.55	$ 0.37	$ 1.17	$ 1.54	$ 1.30
Diluted earnings per share (in dollars per share)	$ 0.36	$ 0.62	$ 0.54	$ 0.36	$ 1.15	$ 1.52	$ 1.29
Cash provided by operating activities		$ 148,452	$ 13,331		$ 161,783	$ 282,263	$ 266,307
Cash used in financing activities						(130,933)	(1,195)
Effective income tax rate reconciliation share based compensation excess tax benefit amount	$ 500					9,000
Provision for income taxes	14,264	25,565	15,320	$ 21,426	40,884	55,149	65,672
Net income	30,484	51,626	44,987	$ 30,366	96,614	127,097	$ 109,872
Accumulated earnings	$ 1,577,521	$ 1,547,037	$ 1,495,411		$ 1,547,037	$ 1,577,521		$ 1,450,684
Scenario, Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Basic earnings per share (in dollars per share)		$ 0.58	$ 0.49		$ 1.07
Diluted earnings per share (in dollars per share)		$ 0.57	$ 0.48		$ 1.05
Cash provided by operating activities		$ 144,734	$ 8,580		$ 153,314
Provision for income taxes		29,280	20,140		49,420
Net income		47,911	40,167		88,078
Accumulated earnings		$ 1,538,762	$ 1,490,851		$ 1,538,762
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)	$ 0.01				$ 0.10	$ 0.11
Diluted earnings per share (in dollars per share)	$ 0.01				$ 0.10	$ 0.11
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					$ 8,500
Cash used in financing activities					$ (8,500)

Earnings per Share (Detail)

Earnings per Share (Detail) - shares shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Earnings Per Share [Abstract]
Antidilutive securities excluded from computation of earnings per share (less than .3 million in all periods) (in shares)	0.2	0.2	0.2	0.2

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				6 Months Ended	9 Months Ended
	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Sep. 30, 2015	Jun. 30, 2016	Sep. 30, 2016	Sep. 30, 2015
Numerator:
Net income used for calculating basic and diluted earnings per common share	$ 30,484	$ 51,626	$ 44,987	$ 30,366	$ 96,614	$ 127,097	$ 109,872
Denominator:
Weighted average number of common shares used in the calculation of basic earnings per share	82,638			82,989		82,549	84,244
Common stock equivalents associated with stock-based compensation plans (in shares)	1,165			1,124		1,212	1,191
Shares used in the calculation of diluted earnings per share	83,803			84,113		83,761	85,435
Basic earnings per share (in dollars per share)	$ 0.37	$ 0.63	$ 0.55	$ 0.37	$ 1.17	$ 1.54	$ 1.30
Diluted earnings per share (in dollars per share)	$ 0.36	$ 0.62	$ 0.54	$ 0.36	$ 1.15	$ 1.52	$ 1.29

Stock-Based Compensation (Detai

Stock-Based Compensation (Detail) - USD ($) $ / shares in Units, shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for grant (in shares)	6.2		6.2
Common stock par value (in dollars per share)	$ 0.0005		$ 0.0005		$ 0.0005
Total share-based compensation cost not yet recognized	$ 59,400,000		$ 59,400,000
Total compensation cost not yet recognized, period for recognition			2 years 4 months 24 days
Total stock-based compensation expense	9,500,000	$ 9,600,000	$ 36,100,000	$ 37,000,000
Retirement Eligible Employees Equity Award
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	2,500,000	3,000,000	$ 16,500,000	17,400,000
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	1,300,000	1,100,000	$ 4,300,000	4,500,000
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	$ 8,000,000	$ 8,300,000	$ 31,300,000	32,000,000
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%		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%		95.00%
Maximum number of shares that may be purchased by eligible participants (in shares)	1		1
Proceeds from stock plans			$ 6,900,000	$ 5,600,000

Stock-Based Compensation (Det34

Stock-Based Compensation (Detail) - Stock-Based Compensation Expense Recognized In Consolidated Statements Of Operations - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 9.5	$ 9.6	$ 36.1	$ 37
Cost of services and product development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	4.6	4.5	17	16.1
Cost of services and product development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	4.9	5.1	19.1	20.9
Stock appreciation rights (SARs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	1.3	1.1	4.3	4.5
Common Stock Equivalents (CSEs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	0.2	0.2	0.5	0.5
Restricted stock units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 8	$ 8.3	$ 31.3	$ 32

Stock-Based Compensation (Det35

Stock-Based Compensation (Detail) - Summary Of Changes In SARs Outstanding - Stock appreciation rights (SARs) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
SARs [Roll Forward]
Outstanding at December 31, 2015 (in shares)	1.3
Granted (in shares)	0.4
Exercised (in shares)	(0.3)
Outstanding at September 30, 2016 (in shares)	1.4	1.3
Vested and exercisable at September 30, 2016 (in shares)	0.6
Per Share Weighted- Average Exercise Price [Roll Forward]
Outstanding at December 31, 2015 (in dollars per share)	$ 56.47
Granted (in dollars per share)	80.06
Exercised (in dollars per share)	42.22
Outstanding at September 30, 2016 (in dollars per share)	65.10	$ 56.47
Vested and exercisable at September 30, 2016 (in dollars per share)	53.33
Per Share Weighted Average Grant Date Fair Value [Roll Forward]
Outstanding at December 31, 2015 (in dollars per share)	14.92
Granted (in dollars per share)	16.50
Exercised (in dollars per share)	13.45
Outstanding at September 30, 2016 (in dollars per share)	15.60	$ 14.92
Vested and exercisable at September 30, 2016 (in dollars per share)	$ 14.57
Weighted Average Remaining Contractual Term [Roll Forward]
Granted	6 years 4 months 10 days
Outstanding at September 30, 2016	4 years 6 months 15 days	4 years 5 months 16 days
Vested and exercisable at September 30, 2016	3 years 4 months 16 days
Aggregate Intrinsic value of outstanding shares	$ 32.4
Aggregate intrinsic value of shares vested and exercisable	$ 20.7
Unvested
SARs [Roll Forward]
Outstanding at September 30, 2016 (in shares)	0.8

Stock-Based Compensation (Det36

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)	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
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%	24.00%
Risk-free interest rate	1.10%	1.50%
Expected life in years	4 years 4 months 24 days	4 years 4 months 24 days

Stock-Based Compensation (Det37

Stock-Based Compensation (Detail) - Summary Of Changes In RSUs Outstanding - Restricted stock units (RSUs) shares in Millions	9 Months Ended
	Sep. 30, 2016$ / sharesshares
Restricted Stock Units (RSUs) [Roll Forward]
Outstanding at December 31, 2015 (in shares)	1.4
Granted (in shares)	0.6
Vested and released (in shares)	(0.6)
Forfeited (in shares)	(0.1)
Outstanding at September 30, 2016 (in shares)	1.3
Per Share Weighted Average Grant Date Fair Value [Roll Forward]
Outstanding at December 31, 2015 (in dollars per share) | $ / shares	$ 62.80
Granted (in dollars per share) | $ / shares	81.39
Vested and released (in dollars per share) | $ / shares	58.01
Forfeited (in dollars per share) | $ / shares	69.02
Outstanding at September 30, 2016 (in dollars per share) | $ / shares	$ 73.17
Weighted average remaining contractual terms	1 year 3 months 18 days
Executive officer
Restricted Stock Units (RSUs) [Roll Forward]
Granted (in shares)	0.3
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 (Det38

Stock-Based Compensation (Detail) - Summary Of Changes In CSEs Outstanding - Common stock equivalents (CSEs)	9 Months Ended
	Sep. 30, 2016$ / 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, 2015 (in shares) | shares	105,664
Granted (in shares) | shares	5,332
Converted to common shares upon grant (in shares) | shares	(4,127)
Outstanding at September 30, 2016 (in shares) | shares	106,869
Per Share Weighted Average Grant Date Fair Value [Roll Forward]
Outstanding at December 31, 2015 (in dollars per share) | $ / shares	$ 19.57
Granted (in dollars per share) | $ / shares	91.96
Converted to common shares upon grant (in dollars per share) | $ / shares	91.96
Outstanding at September 30, 2016 (in dollars per share) | $ / shares	$ 20.39

Segment Information (Details) -

Segment Information (Details) - Information About Reportable Segments	3 Months Ended		9 Months Ended
	Sep. 30, 2016USD ($)	Sep. 30, 2015USD ($)	Sep. 30, 2016USD ($)segment	Sep. 30, 2015USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment			3
Revenues	$ 574,059,000	$ 500,166,000	$ 1,741,323,000	$ 1,519,288,000
Operating income	48,726,000	52,474,000	196,454,000	186,376,000
Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Reportable segments
Segment Reporting Information [Line Items]
Revenues	574,059,000	500,166,000	1,741,323,000	1,519,288,000
Gross contribution	355,390,000	308,103,000	1,088,960,000	946,479,000
Corporate and other expenses
Segment Reporting Information [Line Items]
Corporate and other expenses	(306,664,000)	(255,629,000)	(892,506,000)	(760,103,000)
Research | Reportable segments
Segment Reporting Information [Line Items]
Revenues	461,502,000	396,179,000	1,350,943,000	1,162,987,000
Gross contribution	319,239,000	274,967,000	941,113,000	811,877,000
Consulting | Reportable segments
Segment Reporting Information [Line Items]
Revenues	79,082,000	74,686,000	258,090,000	239,814,000
Gross contribution	21,622,000	21,593,000	84,273,000	81,175,000
Events | Reportable segments
Segment Reporting Information [Line Items]
Revenues	33,475,000	29,301,000	132,290,000	116,487,000
Gross contribution	$ 14,529,000	$ 11,543,000	$ 63,574,000	$ 53,427,000

Segment Information (Details)40

Segment Information (Details) - Reconciliation of Segment Gross Contribution to Net Income - USD ($) $ in Thousands	3 Months Ended				6 Months Ended	9 Months Ended
	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Sep. 30, 2015	Jun. 30, 2016	Sep. 30, 2016	Sep. 30, 2015
Costs and expenses:
Cost of services and product development - unallocated	$ 223,122			$ 193,602		$ 666,585	$ 581,859
Selling, general and administrative	269,902			236,355		799,322	703,868
Acquisition and integration charges	16,557			6,488		32,958	15,263
Operating income	48,726			52,474		196,454	186,376
Interest expense and other, net	3,978			682		14,208	10,832
Provision for income taxes	14,264	$ 25,565	$ 15,320	21,426	$ 40,884	55,149	65,672
Net income	30,484	$ 51,626	$ 44,987	30,366	$ 96,614	127,097	109,872
Reportable segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total segment gross contribution	355,390			308,103		$ 1,088,960	946,479
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	4,453			1,539		$ 14,222	9,050
Selling, general and administrative	269,902			236,355		799,322	703,868
Depreciation and amortization	15,752			11,247		46,004	31,922
Acquisition and integration charges	$ 16,557			$ 6,488		$ 32,958	$ 15,263

Goodwill and Intangible Asset41

Goodwill and Intangible Assets (Detail) - Changes to Carrying Amount of Goodwill by Reporting Unit - USD ($)	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Goodwill [Line Items]
Goodwill, Impaired, Accumulated Impairment Loss	$ 0
Goodwill impairment		$ 0
Goodwill [Roll Forward]
Balance, December 31, 2015	715,359,000
Additions due to acquisitions	31,702,000
Foreign currency translation adjustments	(4,135,000)
Balance, September 30, 2016	742,926,000
Research
Goodwill [Roll Forward]
Balance, December 31, 2015	575,292,000
Additions due to acquisitions	25,744,000
Foreign currency translation adjustments	(2,291,000)
Balance, September 30, 2016	598,745,000
Consulting
Goodwill [Roll Forward]
Balance, December 31, 2015	98,412,000
Additions due to acquisitions	0
Foreign currency translation adjustments	(1,188,000)
Balance, September 30, 2016	97,224,000
Events
Goodwill [Roll Forward]
Balance, December 31, 2015	41,655,000
Additions due to acquisitions	5,958,000
Foreign currency translation adjustments	(656,000)
Balance, September 30, 2016	$ 46,957,000

Goodwill and Intangible Asset42

Goodwill and Intangible Assets (Detail) - Carrying Amounts of Amortizable Intangible Assets - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Finite-lived Intangible Assets Acquired			$ 4,110
Finite-Lived Intangible Assets, Fully Amortized Intangibles			287
Finite-lived Intangible Assets [Roll Forward]
Gross carrying amount			118,003
Foreign currency translation impact			(6,029)
Gross carrying amount	$ 115,797		115,797
Accumulated amortization	(34,028)		(34,028)		$ (21,459)
Finite-lived intangible assets, net	81,769		81,769		96,544
Amortization of intangibles	6,221	$ 2,737	18,614	$ 6,983
Trade Name
Finite-Lived Intangible Assets [Line Items]
Finite-lived Intangible Assets Acquired			302
Finite-Lived Intangible Assets, Fully Amortized Intangibles			0
Finite-lived Intangible Assets [Roll Forward]
Gross carrying amount			4,144
Foreign currency translation impact			(49)
Gross carrying amount	4,397		4,397
Accumulated amortization	(1,466)		(1,466)		(681)
Finite-lived intangible assets, net	2,931		$ 2,931		3,463
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 [Line Items]
Finite-lived Intangible Assets Acquired			$ 2,769
Finite-Lived Intangible Assets, Fully Amortized Intangibles			0
Finite-lived Intangible Assets [Roll Forward]
Gross carrying amount			62,860
Foreign currency translation impact			(2,631)
Gross carrying amount	62,998		62,998
Accumulated amortization	(14,312)		(14,312)		(9,028)
Finite-lived intangible assets, net	48,686		$ 48,686		53,832
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			7 years
Content
Finite-Lived Intangible Assets [Line Items]
Finite-lived Intangible Assets Acquired			$ 1,039
Finite-Lived Intangible Assets, Fully Amortized Intangibles			162
Finite-lived Intangible Assets [Roll Forward]
Gross carrying amount			5,450
Foreign currency translation impact			(3,416)
Gross carrying amount	2,911		2,911
Accumulated amortization	(1,573)		(1,573)		(3,525)
Finite-lived intangible assets, net	1,338		$ 1,338		1,925
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			4 years
Software
Finite-Lived Intangible Assets [Line Items]
Finite-lived Intangible Assets Acquired			$ 0
Finite-Lived Intangible Assets, Fully Amortized Intangibles			125
Finite-lived Intangible Assets [Roll Forward]
Gross carrying amount			16,219
Foreign currency translation impact			45
Gross carrying amount	16,139		16,139
Accumulated amortization	(7,617)		(7,617)		(3,699)
Finite-lived intangible assets, net	8,522		$ 8,522		12,520
Finite-lived intangible assets useful life			3 years
Non-Compete
Finite-Lived Intangible Assets [Line Items]
Finite-lived Intangible Assets Acquired			$ 0
Finite-Lived Intangible Assets, Fully Amortized Intangibles			0
Finite-lived Intangible Assets [Roll Forward]
Gross carrying amount			29,330
Foreign currency translation impact			22
Gross carrying amount	29,352		29,352
Accumulated amortization	(9,060)		(9,060)		(4,526)
Finite-lived intangible assets, net	$ 20,292		$ 20,292		$ 24,804
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 Asset43

Goodwill and Intangible Assets (Detail) - Estimated Future Amortization Expense By Year From Amortizable Intangibles - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2016 (remaining three months)	$ 6,124
2,017	22,722
2,018	19,761
2,019	14,958
2,020	12,776
2,021	5,428
Thereafter	0
Finite-lived intangible assets, net	$ 81,769	$ 96,544

Debt (Detail)

Debt (Detail)	Jun. 17, 2016USD ($)	Sep. 30, 2016USD ($)installment	Dec. 31, 2015USD ($)
Debt Instrument [Line Items]
Long-term debt		$ 736,405,000	$ 825,000,000
Debt instrument, interest, additional interest above eurodollar rate	1.00%
Euro Dollar rate
Debt Instrument [Line Items]
Minimum applicable margin rate	1.125%
Maximum applicable margin rate	2.00%
2016 Credit Facility Agreement
Debt Instrument [Line Items]
Debt issuance costs, gross	$ 5,000,000	$ 5,000,000
Federal Funds rate
Debt Instrument [Line Items]
Debt instrument interest additional interest above federal fund rate	0.50%
Federal Funds rate | Euro Dollar rate
Debt Instrument [Line Items]
Minimum applicable margin rate	0.125%
Maximum applicable margin rate	1.00%
Bank Term Loan
Debt Instrument [Line Items]
Long-term debt	$ 600,000,000
Proceeds from issuance of debt	600,000,000
Revolving credit facility
Debt Instrument [Line Items]
Line of credit facility, current borrowing capacity	1,200,000,000
Line of credit facility, additional borrowing capacity (up to)	$ 500,000,000
Line of credit facility, frequency of payments | installment		16
Debt instrument covenant, maximum pledge of subsidiaries voting stock	66.00%
Proceeds from issuance of debt	$ 200,000,000
Letter of Credit
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 50,000,000
Interest expense, net
Debt Instrument [Line Items]
Write off of deferred debt issuance cost		$ 1,300,000

Debt (Detail) - Borrowings

Debt (Detail) - Borrowings	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2016USD ($)	Sep. 30, 2016USD ($)contractoutstanding_contract	Dec. 31, 2012USD ($)	Jun. 17, 2016USD ($)	Dec. 31, 2015USD ($)outstanding_contract
Debt Instrument [Line Items]
Long-term debt, gross		$ 745,000,000			$ 825,000,000
Debt issuance costs, line of credit arrangements, net		(8,595,000)			0
Long-term debt		$ 736,405,000			825,000,000
Debt instrument interest additional interest above base rate		1.38%
Notional amount of interest rate derivatives		$ 723,089,000			$ 893,610,000
Debt instrument, effective percentage		2.77%
Number of derivative contracts | outstanding_contract		19			105
Interest rate swap
Debt Instrument [Line Items]
Notional amount of interest rate derivatives		$ 700,000,000
Number of derivative contracts | contract		3
Derivative, term of contract		30 days
Interest rate, fair value hedge derivative at fair value, net (negative fair value)		$ 14,900,000
Interest rate swap | Minimum
Debt Instrument [Line Items]
Derivative, fixed interest rate		1.53%
Interest rate swap | Maximum
Debt Instrument [Line Items]
Derivative, fixed interest rate		1.60%
2016 Credit Facility Agreement
Debt Instrument [Line Items]
Debt issuance costs, gross		$ 5,000,000		$ 5,000,000
Bank Term Loan
Debt Instrument [Line Items]
Long-term debt, gross		$ 592,500,000			$ 380,000,000
Long-term debt				$ 600,000,000
Contractual annualized interest rate		1.90%
Floating eurodollar based rate		0.52%
Bank Term Loan | Interest rate swap
Debt Instrument [Line Items]
Notional amount of interest rate derivatives		$ 700,000,000
Connecticut Economic Development Program
Debt Instrument [Line Items]
Long-term debt, gross		5,000,000			5,000,000
Debt instrument, fixed interest rate			3.00%
Debt instrument term			10 years
Debt instrument, period principal payments are deferred			5 years
Debt instrument, principal forgiveness provision			$ 2,500,000
Debt instrument, forgiveness period under the terms of the loan			5 years
Revolving credit facility
Debt Instrument [Line Items]
Long-term debt, gross		$ 147,500,000			$ 440,000,000
Contractual annualized interest rate		1.84%
Line of credit facility, remaining borrowing capacity		$ 1,050,000,000
Letter of Credit
Debt Instrument [Line Items]
Letters of credit outstanding, amount		$ 3,800,000
Scenario, Forecast | Connecticut Economic Development Program
Debt Instrument [Line Items]
Debt instrument, decrease, forgiveness	$ 2,500,000

Equity (Detail) - Share Repurch

Equity (Detail) - Share Repurchase Program and Share Repurchase Activity - USD ($)	1 Months Ended	3 Months Ended		9 Months Ended
	Jan. 31, 2016	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Stockholders' Equity Note [Abstract]
Stock repurchase program, authorized amount		$ 1,200,000,000		$ 1,200,000,000
Stock repurchase program, remaining authorized repurchase amount		$ 1,110,000,000		$ 1,110,000,000
Number of shares repurchased (in shares)		9,882	210,012	542,792	5,538,612
Cash paid for repurchased shares during the quarter	$ 7,200,000	$ 922,000	$ 11,558,000	$ 52,889,000	$ 453,000,000
Treasury stock, average price paid per share (in dollars per share)		$ 93.33	$ 83.79	$ 84.17	$ 82.40

Equity (Details) - Changes in A

Equity (Details) - Changes in AOCI by Component (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			$ (132,400)
Other comprehensive income (loss), net of tax	$ 219	$ (13,657)	(3,382)	$ (28,104)
Ending balance	(10,498)		(10,498)
Interest Rate Swaps
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(12,158)	(2,410)	(3,079)	(1,740)
Change in AOCL/I before reclassifications to income	2,076	(7,457)	(9,376)	(9,910)
Reclassifications from AOCI to income during the period	1,138	1,647	3,511	3,430
Other comprehensive income (loss), net of tax	3,214	(5,810)	(5,865)	(6,480)
Ending balance	(8,944)	(8,220)	(8,944)	(8,220)
Defined Benefit Pension Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(4,757)	(5,922)	(4,832)	(6,028)
Change in AOCL/I before reclassifications to income	0	0	0	0
Reclassifications from AOCI to income during the period	37	53	112	159
Other comprehensive income (loss), net of tax	37	53	112	159
Ending balance	(4,720)	(5,869)	(4,720)	(5,869)
Foreign Currency Translation Adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(31,088)	(27,285)	(36,491)	(13,402)
Change in AOCL/I before reclassifications to income	(3,032)	(7,900)	2,371	(21,783)
Reclassifications from AOCI to income during the period	0	0	0	0
Other comprehensive income (loss), net of tax	(3,032)	(7,900)	2,371	(21,783)
Ending balance	(34,120)	(35,185)	(34,120)	(35,185)
AOCI Attributable to Parent
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(48,003)	(35,617)	(44,402)	(21,170)
Change in AOCL/I before reclassifications to income	(956)	(15,357)	(7,005)	(31,693)
Reclassifications from AOCI to income during the period	1,175	1,700	3,623	3,589
Other comprehensive income (loss), net of tax	219	(13,657)	(3,382)	(28,104)
Ending balance	$ (47,784)	$ (49,274)	$ (47,784)	$ (49,274)

Income Taxes (Detail)

Income Taxes (Detail) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended	9 Months Ended
	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Sep. 30, 2015	Jun. 30, 2016	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Provision for income taxes	$ 14,264	$ 25,565	$ 15,320	$ 21,426	$ 40,884	$ 55,149	$ 65,672
Effective income tax rate	31.90%			41.40%		30.30%	37.40%
Effective income tax rate reconciliation share based compensation excess tax benefit amount	$ 500					$ 9,000
Unrecognized tax benefits	31,800					31,800		$ 25,900
Decrease in unrecognized tax benefits is reasonably possible	$ 2,500					$ 2,500

Derivatives and Hedging (Detail

Derivatives and Hedging (Detail) - Outstanding Derivatives Contracts	9 Months Ended	12 Months Ended
	Sep. 30, 2016USD ($)contractoutstanding_contract	Dec. 31, 2015USD ($)outstanding_contract
Derivatives, Fair Value [Line Items]
Number of Outstanding Contracts | outstanding_contract	19	105
Notional Amounts	$ 723,089,000	$ 893,610,000
Fair Value Asset (Liability), Net	(14,974,000)	(4,897,000)
Unrealized Loss Recorded in OCI	$ (8,944,000)	(3,079,000)
Interest rate swap
Derivatives, Fair Value [Line Items]
Number of Outstanding Contracts | contract	3
Notional Amounts	$ 700,000,000
Designated as hedging instrument | Interest rate swap
Derivatives, Fair Value [Line Items]
Unrealized Loss Recorded in OCI	$ (8,944,000)	$ (3,079,000)
Designated as hedging instrument | Other liabilities | Interest rate swap
Derivatives, Fair Value [Line Items]
Number of Outstanding Contracts | outstanding_contract	3	3
Notional Amounts	$ 700,000,000	$ 700,000,000
Fair Value Asset (Liability), Net	$ (14,907,000)	$ (5,132,000)
Not designated as hedging instrument | Accrued liabilities | Foreign currency forwards
Derivatives, Fair Value [Line Items]
Number of Outstanding Contracts | outstanding_contract	16	102
Notional Amounts	$ 23,089,000	$ 193,610,000
Fair Value Asset (Liability), Net	$ (67,000)	$ 235,000

Derivatives and Hedging (Deta50

Derivatives and Hedging (Detail) - Derivative Gains And Losses That Have Been Recognized In Condensed Consolidated Statements Of Operations - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Total expense, net	$ 1,081	$ 2,393	$ 5,612	$ 6,168
Interest expense, net
Derivative Instruments, Gain (Loss) [Line Items]
Total expense, net	1,895	2,762	5,851	6,094
Other expense (income), net
Derivative Instruments, Gain (Loss) [Line Items]
Total expense, net	$ (814)	$ (369)	$ (239)	$ 74

Fair Value Disclosures (Detail)

Fair Value Disclosures (Detail) - Assets And Liabilities Measured At Fair Value On Recurring Basis - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Assets:
Assets measured at fair value on a recurring basis	$ 37,106	$ 34,755
Fair Value, Inputs, Level 1 | Deferred compensation plan assets
Assets:
Assets measured at fair value on a recurring basis	10,051	8,671
Fair Value, Inputs, Level 2
Assets:
Assets measured at fair value on a recurring basis	27,055	26,084
Liabilities:
Liabilities measured at fair value on a recurring basis	57,092	44,578
Fair Value, Inputs, Level 2 | Foreign currency forward contracts
Assets:
Assets measured at fair value on a recurring basis	58	610
Liabilities:
Liabilities measured at fair value on a recurring basis	125	375
Fair Value, Inputs, Level 2 | Interest rate swap contract
Liabilities:
Liabilities measured at fair value on a recurring basis	14,907	5,132
Fair Value, Inputs, Level 2 | Deferred compensation plan assets
Assets:
Assets measured at fair value on a recurring basis	26,997	25,474
Fair Value, Inputs, Level 2 | Deferred compensation plan liabilities
Liabilities:
Liabilities measured at fair value on a recurring basis	$ 42,060	$ 39,071

Employee Benefits (Detail)

Employee Benefits (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Compensation and Retirement Disclosure [Abstract]
Net periodic pension expense	$ 0.9	$ 0.8	$ 2.4	$ 2.3

Commitments and Contingencies (

Commitments and Contingencies (Details)	Sep. 30, 2016USD ($)
Commitments and Contingencies Disclosure [Abstract]
Loss Contingency Accrual	$ 0