Gartner (IT) 10-K 22 Feb 17 2016 FY Annual report Financial data

Document And Entity Information

Document And Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2016	Jan. 31, 2017	Jun. 30, 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-K
Document Period End Date	Dec. 31, 2016
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Common Stock, Shares Outstanding		82,652,880
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 7,771,510,947

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 474,233	$ 372,976
Fees receivable, net of allowances of $7,400 and $6,900 respectively	643,013	580,763
Deferred commissions	141,410	124,831
Prepaid expenses and other current assets	84,540	62,427
Total current assets	1,343,196	1,140,997
Property, equipment and leasehold improvements, net	121,606	108,733
Goodwill	738,453	715,359
Intangible assets, net	76,801	96,544
Other assets	87,279	106,884
Total Assets	2,367,335	2,168,517
Current liabilities:
Accounts payable and accrued liabilities	440,771	387,691
Deferred revenues	989,478	900,801
Current portion of long-term debt	30,000	35,000
Total current liabilities	1,460,249	1,323,492
Long-term debt, net of deferred financing fees	664,391	783,831
Other liabilities	181,817	193,594
Total Liabilities	2,306,457	2,300,917
Preferred stock:
$.01 par value, authorized 5,000,000 shares; none issued or outstanding	0	0
Common stock:
$.0005 par value, authorized 250,000,000 shares for both periods; 156,234,415 shares issued for both periods	78	78
Additional paid-in capital	863,127	818,546
Accumulated other comprehensive loss, net	(49,683)	(44,402)
Accumulated earnings	1,644,005	1,450,684
Treasury stock, at cost, 73,583,172 and 73,896,245 common shares, respectively	(2,396,649)	(2,357,306)
Total Stockholders’ Equity (Deficit)	60,878	(132,400)
Total Liabilities and Stockholders’ Equity (Deficit)	$ 2,367,335	$ 2,168,517

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Fees receivable, allowances	$ 7,400	$ 6,900
Preferred stock par value (in Dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock par value (in Dollars per share)	$ 0.0005	$ 0.0005
Common stock, shares authorized	250,000,000	250,000,000
Common stock, shares issued	156,234,415	156,234,415
Treasury stock, Shares	73,583,172	73,896,245

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenues:
Research	$ 1,829,721	$ 1,583,486	$ 1,445,338
Consulting	346,214	327,735	348,396
Events	268,605	251,835	227,707
Total revenues	2,444,540	2,163,056	2,021,441
Costs and expenses:
Cost of services and product development	945,648	839,076	797,933
Selling, general and administrative	1,089,184	962,677	876,067
Depreciation	37,172	33,789	31,186
Amortization of intangibles	24,797	13,342	8,226
Acquisition and integration charges	42,598	26,175	21,867
Total costs and expenses	2,139,399	1,875,059	1,735,279
Operating income	305,141	287,997	286,162
Interest income	2,449	1,766	1,413
Interest expense	(27,565)	(22,548)	(12,300)
Other income (expense), net	8,406	4,996	(592)
Income before income taxes	288,431	272,211	274,683
Provision for income taxes	94,849	96,576	90,917
Net income	$ 193,582	$ 175,635	$ 183,766
Net income per share:
Basic (in Dollars per share)	$ 2.34	$ 2.09	$ 2.06
Diluted (in Dollars per share)	$ 2.31	$ 2.06	$ 2.03
Weighted average shares outstanding:
Basic (in shares)	82,571	83,852	89,337
Diluted (in shares)	83,820	85,056	90,719

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Statement of Comprehensive Income [Abstract]
Net income	$ 193,582	$ 175,635	$ 183,766
Other comprehensive (loss) income, net of tax
Foreign currency translation adjustments	(5,986)	(23,089)	(27,461)
Interest rate hedges - net change in deferred loss	1,670	(1,339)	2,163
Pension plans - net change in deferred actuarial loss	(965)	1,196	(4,217)
Other comprehensive (loss) income, net of tax	(5,281)	(23,232)	(29,515)
Comprehensive income	$ 188,301	$ 152,403	$ 154,251

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive (Loss) Income, Net	Accumulated Earnings	Treasury Stock
Beginning Balance at Dec. 31, 2013	$ 361,316		$ 718,644	$ 8,345	$ 1,091,283	$ (1,457,034)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	183,766				183,766
Other comprehensive income (loss)	(29,515)			(29,515)
Issuances under stock plans	7,800		(11,727)			19,527
Stock compensation tax benefits	18,671		18,671
Common share repurchases	(419,712)					(419,712)
Stock compensation expense	38,845		38,845
Ending Balance at Dec. 31, 2014	161,171	$ 78	764,433	(21,170)	1,275,049	(1,857,219)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	175,635				175,635
Other comprehensive income (loss)	(23,232)			(23,232)
Issuances under stock plans	7,531		(5,964)			13,495
Stock compensation tax benefits	13,928		13,928
Common share repurchases	(513,582)					(513,582)
Stock compensation expense	46,149		46,149
Ending Balance at Dec. 31, 2015	(132,400)	78	818,546	(44,402)	1,450,684	(2,357,306)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adoption of ASU No. 2016-09	(261)				(261)
Net income	193,582				193,582
Other comprehensive income (loss)	(5,281)			(5,281)
Issuances under stock plans	10,339		(2,080)			12,419
Common share repurchases	(51,762)					(51,762)
Stock compensation expense	46,661		46,661
Ending Balance at Dec. 31, 2016	$ 60,878	$ 78	$ 863,127	$ (49,683)	$ 1,644,005	$ (2,396,649)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating activities:
Net income	$ 193,582	$ 175,635	$ 183,766
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization of intangibles	61,969	47,131	39,412
Stock-based compensation expense	46,661	46,149	38,845
Excess tax benefits from stock-based compensation exercises	0	(13,860)	(20,193)
Deferred taxes	(2,648)	344	(759)
Gain on extinguishment of debt	(2,500)	0	0
Amortization and write-off of debt issue costs	3,082	1,512	2,645
Changes in assets and liabilities:
Fees receivable, net	(68,661)	(44,476)	(76,424)
Deferred commissions	(18,673)	(13,236)	(12,340)
Prepaid expenses and other current assets	(21,604)	(13,268)	(3,017)
Other assets	20,005	(14,733)	(7,139)
Deferred revenues	97,979	91,840	105,354
Accounts payable, accrued, and other liabilities	56,440	82,523	96,629
Cash provided by operating activities	365,632	345,561	346,779
Investing activities:
Additions to property, equipment and leasehold improvements	(49,863)	(46,128)	(38,486)
Acquisitions (net of cash acquired)	(34,186)	(196,229)	(124,291)
Cash used in investing activities	(84,049)	(242,357)	(162,777)
Financing activities:
Proceeds from ESP Plan	9,250	7,499	7,767
Proceeds from borrowings	715,000	440,000	400,000
Payments on debt	(835,000)	(20,000)	(200,000)
Purchases of treasury stock	(58,961)	(509,049)	(432,006)
Fees paid for debt refinancing	(4,975)	0	(4,624)
Excess tax benefits from stock-based compensation exercises	0	13,860	20,193
Cash used by financing activities	(174,686)	(67,690)	(208,670)
Net increase (decrease) in cash and cash equivalents	106,897	35,514	(24,668)
Effects of exchange rates on cash and cash equivalents	(5,640)	(27,840)	(34,020)
Cash and cash equivalents, beginning of period	372,976	365,302	423,990
Cash and cash equivalents, end of period	474,233	372,976	365,302
Cash paid during the period for:
Interest	23,400	21,200	10,600
Income taxes, net of refunds received	$ 86,300	$ 83,500	$ 70,100

Business and Significant Accoun

Business and Significant Accounting Policies	12 Months Ended
	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
BUSINESS AND SIGNIFICANT ACCOUNTING POLICIES	BUSINESS AND SIGNIFICANT ACCOUNTING POLICIES Business. Gartner, Inc. is a global information technology research and advisory company founded in 1979 with its headquarters in Stamford, Connecticut. Gartner delivers its principal products and services 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 consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“U.S. GAAP”), as defined in the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Topic 270 for financial information and with the applicable instructions of U.S. Securities & Exchange Commission (“SEC”) Regulation S-X. The fiscal year of Gartner represents the twelve-month period from January 1 through December 31. All references to 2016 , 2015 , and 2014 herein refer to the fiscal year unless otherwise indicated. Certain prior year balance sheet amounts have been reclassified to conform to the current year presentation. Principles of consolidation. The accompanying consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All significant intercompany transactions and balances have been eliminated. Use of estimates. The preparation of the accompanying consolidated financial statements requires management to make estimates and assumptions about future events. These estimates and the underlying assumptions affect the amounts of assets and liabilities reported, disclosures about contingent assets and liabilities, and reported amounts of revenues and expenses. Such estimates include the valuation of fees receivable, goodwill, intangible assets, and other long-lived assets, as well as tax accruals and other liabilities. In addition, estimates are used in revenue recognition, income tax expense, performance-based compensation charges, depreciation, and amortization. Management believes its use of estimates in the accompanying consolidated financial statements to be reasonable. Management 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. Business Acquisitions. The Company completed acquisitions in each of the three years ended December 31, 2016 and detailed information related to these acquisitions is included in Note 2 — Acquisitions. The Company accounts for acquisitions in accordance with the acquisition method of accounting as prescribed by FASB ASC Topic No. 805, Business Combinations. The acquisition method of accounting requires the Company to record the net assets and liabilities acquired based on their estimated fair values as of the acquisition date, with any excess of the consideration transferred over the estimated fair value of the net assets acquired, including identifiable intangible assets, to be recorded to goodwill. Under the acquisition method, the operating results of acquired companies are included in the Company's consolidated financial statements beginning on the date of acquisition. The determination of the fair values of intangible and other assets acquired in acquisitions requires management judgment and the consideration of a number of factors, significant among them the historical financial performance of the acquired businesses and projected performance, estimates surrounding customer turnover, as well as assumptions regarding the level of competition and the cost to reproduce certain assets. Establishing the useful lives of the intangibles also requires management judgment and the evaluation of a number of factors, among them projected cash flows and the likelihood of competition. The Company classifies charges that are directly-related to its acquisitions in the line Acquisition and Integration Charges in the Consolidated Statements of Operations, and the Company recorded $42.6 million , $26.2 million , and $21.9 million of such charges in 2016, 2015, and 2014, respectively. Included in these directly-related and incremental charges are legal, consulting, retention, severance, and accruals for cash payments subject to the continuing employment of certain key employees of the acquired companies. Revenue Recognition. Revenue is recognized in accordance with U.S. GAAP and SEC Staff Accounting Bulletin No. 104, Revenue Recognition (“SAB 104”). Revenues are only recognized once all required criteria for recognition have been met. The accompanying Consolidated Statements of Operations present revenues net of any sales or value-added taxes that we collect from customers and remit to government authorities. The Company’s revenues by significant source are as follows: Research Research revenues are mainly derived from subscription contracts for research products. The related revenues are deferred and recognized ratably over the applicable contract term. Fees derived from assisting organizations in selecting the right business software for their needs is recognized as earned when the leads are provided to vendors. The Company typically enters into subscription contracts for research products for twelve-month periods or longer. The majority of research contracts are billable upon signing, absent special terms granted on a limited basis from time to time. Research contracts are non-cancelable and non-refundable, except for government contracts that may have cancellation or fiscal funding clauses, which historically have not produced material cancellations. It is our policy to record the amount of the contract that is billable as a fee receivable at the time the contract is signed with a corresponding amount as deferred revenue, since the contract represents a legally enforceable claim. Consulting Consulting revenues, primarily derived from consulting, measurement and strategic advisory services (paid one-day analyst engagements), are principally generated from fixed fee or time and materials engagements. Revenues from fixed fee engagements are recognized on a proportional performance basis, while revenues from time and material engagements are recognized as work is delivered and/or services are provided. Revenues related to contract optimization engagements are contingent in nature and are only recognized upon satisfaction of all conditions related to their payment. Unbilled fees receivable associated with consulting engagements were $45.7 million at December 31, 2016 and $43.2 million at December 31, 2015 . Events Events revenues are deferred and recognized upon the completion of the related symposium, conference or exhibition. In addition, the Company defers certain costs directly related to events and expenses these costs in the period during which the related symposium, conference or exhibition occurs. The Company's policy is to defer only those costs, primarily prepaid site and production services costs, which are incremental and are directly attributable to a specific event. Other costs of organizing and producing our events, primarily Company personnel and non-event specific expenses, are expensed in the period incurred. At the end of each fiscal quarter, the Company assesses on an event-by-event basis whether the expected direct costs of producing a scheduled event will exceed the expected revenues. If such costs are expected to exceed revenues, the Company records the expected loss in the period determined. Allowance for losses. The Company maintains an allowance for losses which is composed of a bad debt allowance and a sales reserve. Provisions are charged against earnings, either as a reduction in revenues or an increase to expense. The determination of the allowance for losses is based on historical loss experience, an assessment of current economic conditions, the aging of outstanding receivables, the financial health of specific clients, and probable losses. Cost of services and product development ( “COS” ). COS expense includes the direct costs incurred in the creation and delivery of our products and services. These costs primarily relate to personnel. Selling, general and administrative ( “SG&A” ). SG&A expense includes direct and indirect selling costs, general and administrative costs, and charges against earnings related to uncollectible accounts. Commission expense. The Company records commission obligations upon the signing of customer contracts and amortizes the deferred obligation as commission expense over the period in which the related revenues are earned. Commission expense is included in SG&A in the Consolidated Statements of Operations. Stock-based compensation expense. The Company accounts for stock-based compensation in accordance with FASB ASC Topics No. 505 and 718 and SEC Staff Accounting Bulletins No. 107 (“SAB No. 107”) and No. 110 (“SAB No. 110”). Stock-based compensation cost is based on the fair value of the award on the date of grant, which is expensed over the related service period, net of estimated forfeitures. The service period is the period over which the employee performs the related services, which is normally the same as the vesting period. During 2016 , 2015 and 2014 , the Company recognized $46.7 million , $46.1 million and $38.8 million , respectively, of stock-based compensation expense, a portion of which is recorded in COS and SG&A in the Consolidated Statements of Operations. In 2016 the Company early adopted FASB Accounting Standards Update ("ASU") 2016-09, " Improvements to Employee Share-Based Payment Accounting." See the " Adoption of new accounting standards" section below for additional information. Income taxes expense. The Company uses the asset and liability method of accounting for income taxes. We estimate our income taxes in each of the jurisdictions where we operate. This process involves estimating our current tax expense together with assessing temporary differences resulting from differing treatment of items for tax and accounting purposes. These differences result in deferred tax assets and liabilities, which are included within our consolidated balance sheets. In assessing the realizability of deferred tax assets, management considers if it is more likely than not that some or all of the deferred tax assets will not be realized. We consider the availability of loss carryforwards, projected reversal of deferred tax liabilities, projected future taxable income, and ongoing prudent and feasible tax planning strategies in making this assessment. The Company recognizes the tax benefit from an uncertain tax position only if it is more likely than not the tax position will be sustained based on the technical merits of the position. Cash and cash equivalents. Includes cash and all highly liquid investments with original maturities of three months or less, which are considered cash equivalents. The carrying value of cash equivalents approximates fair value due to their short-term maturity. Investments with maturities of more than three months are classified as marketable securities. Interest earned is classified in Interest income in the Consolidated Statements of Operations. Property, equipment and leasehold improvements. The Company leases all of its facilities and certain equipment. These leases are all classified as operating leases in accordance with FASB ASC Topic 840. The cost of these operating leases, including any contractual rent increases, rent concessions, and landlord incentives, are recognized ratably over the life of the related lease agreement. Lease expense was $38.0 million , $33.8 million , and $31.5 million in 2016 , 2015 , and 2014 , respectively. Equipment, leasehold improvements, and other fixed assets owned by the Company are recorded at cost less accumulated depreciation. Except for leasehold improvements, these fixed assets are depreciated using the straight-line method over the estimated useful lives of the assets. Leasehold improvements are amortized using the straight-line method over the shorter of the estimated useful lives of the improvement or the remaining term of the related lease. The Company had total depreciation expense of $37.2 million , $33.8 million , and $31.2 million in 2016 , 2015 , and 2014 , respectively. The Company's total fixed assets, less accumulated depreciation and amortization, consisted of the following (in thousands): Useful Life December 31, Category (Years) 2016 2015 Computer equipment and software 2-7 $ 166,385 $ 148,195 Furniture and equipment 3-8 43,137 39,072 Leasehold improvements 2-15 96,603 87,103 $ 306,125 $ 274,370 Less — accumulated depreciation and amortization (184,519 ) (165,637 ) Property, equipment, and leasehold improvements, net $ 121,606 $ 108,733 The Company incurs costs to develop internal use software used in our operations, and certain of these costs meeting the criteria outlined in FASB ASC Topic No. 350 are capitalized and amortized over future periods. Net capitalized development costs for internal use software was $16.6 million and $14.1 million at December 31, 2016 and 2015 , respectively, which is included in the Computer equipment and software category above. Amortization of capitalized internal software development costs, which is classified in Depreciation in the Consolidated Statements of Operations, totaled $8.8 million and $8.2 million in 2016 and 2015, respectively. Intangible assets. The Company has finite-lived intangible assets which are amortized against earnings using the straight-line method over their expected useful lives. Changes in intangible assets subject to amortization during the two-year period ended December 31, 2016 were as follows (in thousands): December 31, 2016 Trade Names 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 3,677 1,948 — — 5,927 Intangibles fully amortized — — (162 ) (125 ) — (287 ) Foreign currency translation impact (109 ) (3,168 ) (3,508 ) (69 ) (22 ) (6,876 ) Gross cost 4,337 63,369 3,728 16,025 29,308 116,767 Accumulated amortization (2), (3) (1,737 ) (16,744 ) (2,033 ) (8,904 ) (10,548 ) (39,966 ) Balance, December 31, 2016 $ 2,600 $ 46,625 $ 1,695 $ 7,121 $ 18,760 $ 76,801 December 31, 2015 Trade Names Customer Relationships Content Software Non-Compete Total Gross cost, December 31, 2014 $ 6,924 $ 27,933 $ 3,560 $ 6,569 $ 9,272 $ 54,258 Additions due to acquisitions (1) 3,260 42,620 2,000 11,656 20,075 79,611 Intangibles fully amortized (6,013 ) (7,210 ) — — — (13,223 ) Foreign currency translation impact (27 ) (483 ) (110 ) (2,006 ) (17 ) (2,643 ) 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 due to the Company's acquisitions. See Note 2 — Acquisitions for additional information. (2) Intangible assets are 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 $24.8 million , $13.3 million , and $8.2 million in 2016 , 2015 , and 2014 , respectively. The estimated future amortization expense by year from finite-lived intangibles is as follows (in thousands): 2017 $ 23,356 2018 20,072 2019 15,081 2020 12,897 2021 and thereafter 5,395 $ 76,801 Goodwill. Goodwill represents the excess of the purchase price of acquired businesses over the estimated fair value of the tangible and identifiable intangible net assets acquired. The evaluation of the recoverability of goodwill is performed in accordance with FASB ASC No. 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. If our annual goodwill impairment evaluation determines that the fair value of a reporting unit is less than its related carrying amount, we may recognize an impairment charge against earnings. In connection with its most recent annual impairment test of goodwill performed during the third quarter of 2016, the Company utilized the qualitative approach in assessing the fair value of its reporting units relative to their respective carrying values, which indicated no impairment of recorded goodwill. The following table presents changes to the carrying amount of goodwill by segment during the two-year period ended December 31, 2016 (in thousands): Research Consulting Events Total Balance, December 31, 2014 (1) $ 445,460 $ 99,417 $ 41,788 $ 586,665 Additions due to acquisitions (2) 138,053 — — 138,053 Foreign currency translation adjustments (8,221 ) (1,005 ) (133 ) (9,359 ) Balance, December 31, 2015 $ 575,292 $ 98,412 $ 41,655 $ 715,359 Additions due to acquisitions (2) 28,465 — 5,843 34,308 Foreign currency translation adjustments (8,307 ) (1,932 ) (975 ) (11,214 ) Balance, December 31, 2016 $ 595,450 $ 96,480 $ 46,523 $ 738,453 (1) The Company does not have any accumulated goodwill impairment losses. (2) The additions are due to the Company's acquisitions (See Note 2—Acquisitions for additional information). Impairment of long-lived assets. The Company's long-lived assets primarily consist of intangible assets other than goodwill and property, equipment, and leasehold improvements. The Company reviews its long-lived asset groups for impairment whenever events or changes in circumstances indicate that the carrying amount of the respective asset may not be recoverable. Such evaluation may be based on a number of factors including current and projected operating results and cash flows, changes in management’s strategic direction as well as external economic and market factors. The Company evaluates the recoverability of these assets by determining whether the carrying value can be recovered through undiscounted future operating cash flows. If events or circumstances indicate that the carrying value might not be recoverable based on undiscounted future operating cash flows, an impairment loss would be recognized. The amount of impairment, if any, is measured based on the difference between projected discounted future operating cash flows using a discount rate reflecting the Company’s average cost of funds and the carrying value of the asset. The Company did not record any impairment charges for long-lived asset groups during the three year period ended December 31, 2016 . Pension obligations. The Company has defined-benefit pension plans in several of its international locations (see Note 13 — Employee Benefits). Benefits earned under these plans are generally based on years of service and level of employee compensation. The Company accounts for defined benefit plans in accordance with the requirements of FASB ASC Topic No. 715. The Company determines the periodic pension expense and related liabilities for these plans through actuarial assumptions and valuations. The Company recognized $3.5 million , $3.5 million , and $3.4 million of expense for these plans in 2016 , 2015 , and 2014 , respectively. The Company classifies pension expense in SG&A in the Consolidated Statements of Operations. Debt. The Company presents amounts borrowed in the Consolidated Balance Sheets at amortized cost, net of deferred financing fees. Interest accrued on amounts borrowed is classified in Interest expense in the Consolidated Statements of Operations. The Company refinanced its debt in 2016 and had $702.5 million of debt outstanding at December 31, 2016 (see Note 5—Debt for additional information). Foreign currency exposure. The functional currency of our foreign subsidiaries is typically the local currency. All assets and liabilities of foreign subsidiaries are translated into U.S. dollars at exchange rates in effect at the balance sheet date. Income and expense items are translated at average exchange rates for the year. The resulting translation adjustments are recorded as foreign currency translation adjustments, a component of Accumulated other comprehensive (loss) income, net within the Stockholders’ Equity (Deficit) section of the Consolidated Balance Sheets. Currency transaction gains or losses arising from transactions denominated in currencies other than the functional currency of a subsidiary are recognized in results of operations in Other income (expense), net within the Consolidated Statements of Operations. The Company had net currency transaction losses of $(0.4) million , $(2.6) million , and $(1.7) million in 2016 , 2015 , and 2014 , respectively. The Company enters into foreign currency forward exchange contracts to mitigate the effects of adverse fluctuations in foreign currency exchange rates on these transactions. These contracts generally have a short duration and are recorded at fair value with both realized and unrealized gains and losses recorded in Other income (expense), net. The net (loss) gain from these contracts was $(0.3) million , $(0.1) million , and $0.6 million in 2016 , 2015 , and 2014 , respectively. Comprehensive income. The Company reports comprehensive income in a separate statement called the Consolidated Statements of Comprehensive Income, which is included herein. The Company's comprehensive income disclosures are included in Note 7 — Stockholders' Equity (Deficit). Fair value disclosures. The Company has a limited number of assets and liabilities that are adjusted to fair value at each balance sheet date. The Company’s fair value disclosures are included in Note 12 — Fair Value Disclosures. Concentrations of credit risk. Assets that may subject the Company to concentration of credit risk consist primarily of short-term, highly liquid investments classified as cash equivalents, fees receivable, interest rate swaps, and a pension reinsurance asset. The majority of the Company’s cash equivalent investments and its interest rate swap contracts are with investment grade commercial banks. Fees receivable balances deemed to be collectible from customers have limited concentration of credit risk due to our diverse customer base and geographic dispersion. The Company’s pension reinsurance asset (see Note 13 — Employee Benefits) is maintained with a large international insurance company that was rated investment grade as of December 31, 2016 . Stock repurchase programs. The Company records the cost to repurchase its own common shares to treasury stock. During 2016, 2015 and 2014, the Company used $59.0 million , $509.0 million , and $432.0 million , respectively, in cash for stock repurchases (see Note 7 — Stockholders’ Equity (Deficit). Shares repurchased by the Company are added to treasury shares and are not retired. Adoption of new accounting standards . The Company adopted the following new accounting standards in the year ended December 31, 2016: Extraordinary Items — The Company adopted FASB ASU No. 2015-01, " Simplifying Income Statement Presentation by Eliminating the Concept of Extraordinary Items" ("ASU No. 2015-01") on January 1, 2016. ASU No. 2015-01 eliminated the concept of extraordinary items. Historically the concept caused uncertainty because it was somewhat unclear when an item should be considered both unusual and infrequent and it was rare that a transaction or event met the requirements. The adoption of ASU No. 2015-01 did not have an impact on the Company’s consolidated financial statements. Cloud Computing Arrangement Fees — The Company adopted FASB ASU No. 2015-05, " Customer’s Accounting for Fees Paid in a Cloud Computing Arrangement " ("ASU No. 2015-05) on January 1, 2016. ASU No. 2015-05 provides guidance regarding the costs related to cloud computing and hosting arrangements by identifying what portion of the cost relates to purchased software, if any, and what portion relates to paying for a service. The adoption of ASU No. 2015-05 did not have an impact on the Company’s consolidated financial statements. Business Combinations — The Company adopted FASB ASU No. 2015-16, " Business Combinations - Simplifying the Accounting for Measurement-Period Adjustments " ("ASU No. 2015-16") on January 1, 2016. ASU No. 2015-16 requires the recognition of adjustments to business combination provisional amounts, that are identified during the measurement period, in the reporting period in which the adjustments are determined. The effects of the adjustments to provisional amounts on depreciation, amortization or other income effects are required to be recognized in current-period earnings as if the accounting had been completed at the acquisition date. Certain disclosures are also required. The adoption of ASU No. 2015-16 did not have an impact on the Company’s consolidated financial statements. Debt Issuance Cost Presentation — The Company adopted FASB ASU No. 2015-03, “ Simplifying the Presentation of Debt Issuance Costs ” ("ASU No. 2015-03") on January 1, 2016. ASU No. 2015-03 required that certain debt issuance costs be presented on the balance sheet as a direct deduction from the carrying amount of the liability rather than as deferred assets. The Company reclassified its current and prior year debt issuance costs as required by the rule. Stock-Based Compensation Accounting — The Company early adopted FASB 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 rule was January 1, 2017, the Company elected to early adopt ASU No. 2016-09, as permitted by the amendment. ASU No. 2016-09 requires certain changes in accounting for stock-based compensation, some of which was required to be applied to the beginning of the Company's fiscal year beginning January 1, 2016. Our financial results for periods prior to 2016 were not impacted. 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 Consolidated Statement of Operations. Prior to ASU No. 2016-09, excess tax benefits or deficiencies were recorded in additional paid-in capital in Stockholders' Equity (Deficit) in the Consolidated Balance Sheet. As a result, the benefit from approximately $10.0 million in excess tax benefits from stock compensation awards was recognized in income tax expense in 2016. This benefit increased our 2016 basic and diluted income per share by $0.12 per share. In addition, 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 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 elected to apply this classification amendment prospectively, effective January 1, 2016. The adoption of ASU No. 2016-09 increased the Company's 2016 operating cash flow by $10.0 million with a corresponding decrease in financing activities. ASU No. 2016-09 also permits companies to make an entity-wide accounting policy election to recognize forfeitures of share-based compensation awards as they occur or make an estimate by applying a forfeiture rate each quarter. The Company previously estimated forfeitures but optionally elected to change its accounting policy and account for forfeitures as they occur. ASU No. 2016-09 requires this change in accounting policy to be applied using a cumulative-effect adjustment to accumulated earnings as of the beginning of the period in which the rule is adopted. Accordingly, the Company recorded a $0.3 million decrease to its opening accumulated earnings effective January 1, 2016. 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: Business Combinations — In January 2017, the FASB issued ASU No. 2017-01, "Clarifying the Definition of a Business" ("ASU No. 2017-01"), which is effective for Gartner on January 1, 2018. ASU No. 2017-01 changes the GAAP definition of a business which can impact the accounting for asset purchases, acquisitions, goodwill impairment, and other assessments. We are currently evaluating the impact of ASU No. 2017-01 on the Company's consolidated financial statements. Statement of Cash Flows — In November 2016, the FASB issued ASU No. 2016-18, "Restricted Cash" ("ASU No. 2016-18"). ASU No. 2016-18 requires that amounts generally described as restricted cash and restricted cash equivalents be presented with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. If different, a reconciliation of the cash balances reported in the cash flow statement and the balance sheet would need to be provided along with explanatory information. ASU No. 2016-18 is effective for Gartner on January 1, 2018. We are currently evaluating the impact of ASU No. 2016-18 on the Company's consolidated financial statements. Income Taxes — In October 2016, the FASB issued ASU No. 2016-16, "Intra-Entity Transfers of Assets Other Than Inventory" ("ASU No. 2016-16"). ASU No. 2016-16 accelerates the recognition of taxes on certain intra-entity transactions and is effective for Gartner on January 1, 2018. Current GAAP requires deferral of the income tax implications of an intercompany sale of assets until the assets are sold to a third party or recovered through use. Under the new rule, the seller’s tax effects and the buyer’s deferred taxes will be immediately recognized upon the sale. We have completed an initial evaluation of the impact of ASU No. 2016-16 and we do not expect it will have a material impact on our consolidated financial statements when adopted but could impact the timing of recognition of taxes on future intra-entity transfers. Statement of Cash Flows — In August 2016, the FASB issued ASU No. 2016-15, "Classification of Certain Cash Receipts and Cash Payments" ("ASU No. 2016-15"). ASU No. 2016-15 sets forth classification requirements for certain cash flow transactions. ASU No. 2016-15 is effective for Gartner on January 1, 2018, but early adoption is permitted. We have completed an initial evaluation of the impact of ASU No. 2016-15 and we do not expect it will have a material impact on our consolidated financial statements. Financial Instrument Credit Losses — In June 2016, the FASB issued ASU No. 2016-13, " Financial Instruments—Credit Losses" ("ASU No. 2016-13"). ASU No. 2016-13 amends the current financial instrument impairment model by requiring entities to use a forward-looking approach based on expected losses to estimate credit losses on certain types of financial instruments, including trade receivables. ASU No. 2016-13 is effective for Gartner on January 1, 2020, with early adoption permitted. We are currently evaluating the potential impact of ASU No. 2016-13 on our consolidated financial statements. Leases — In February 2016, the FASB issued ASU No. 2016-02, " Leases " ("ASU No. 2016-02") which will require significant changes in the accounting and disclosure for lease arrangements. Currently under U.S. GAAP, lease arrangements th

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2016
Business Combinations [Abstract]
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. The Company completed the following business acquisitions during the years ended December 31: 2016 On November 9, 2016, the Company acquired 100% of the outstanding capital stock of Machina Research Limited ("Machina"), a privately-held firm based in London with 16 employees. The Company paid approximately $4.5 million in cash at close. Machina provides clients with subscription-based research that provides strategic insight and market intelligence in areas such as IOT ("Internet of things"). 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, for $34.2 million in cash paid at close. SCM World is a leading cross-industry peer network and learning community providing subscription-based research and conferences for supply chain executives. Net of cash acquired with the business and for cash flow reporting purposes, the Company paid approximately $27.9 million in cash for SCM World. The acquisition of SCM World also included an earn-out provision. The fair value of the earn-out was recorded on the acquisition date as part of the cost of the acquisition. The earn-out liability was subsequently adjusted to fair value with a charge to expense at September 30, 2016. At December 31, 2016, the Company determined the final amount of the earn-out and adjusted the liability with an additional charge to expense. In total, the Company recognized $6.5 million in expense related to the earn-out in 2016. The Company expects to pay the earn-out in cash in early 2017. In addition to the earn-out, the Company may also be required to pay up to an additional $5.4 million in cash in the future that is 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 and is being reported in Acquisition and Integration Charges in the Consolidated Statements of Operations. The Company recorded $32.4 million of goodwill and $5.9 million of amortizable intangible assets for these two acquisitions and an immaterial amount of other assets on a net basis. The operating results and the related goodwill are being reported as part of the Company's Research and Events segments and goodwill resulting from these acquisitions will not be deductible for tax purposes. The Company considers the allocation of the purchase price to be preliminary with respect to the completion of certain tax contingencies. The Company believes the recorded goodwill is supported by the anticipated revenue synergies resulting from the acquisitions. The Company's financial statements include the operating results of the acquired businesses beginning from their respective acquisition dates, which were not material to either the Company's consolidated operating results or segment results for 2016. Had the Company acquired these businesses in prior periods, the impact to the Company's operating results for prior periods would not have been material, and as a result pro forma financial information for prior periods has not been presented. The Company also recorded an additional $1.9 million of goodwill in 2016 related to its prior year acquisition of Capterra, Inc. The goodwill increase resulted from certain measurement period adjustments as well as payments related to the settlement of working capital provisions. 2015 The Company acquired 100% of the outstanding shares of Nubera eBusiness S.L., and Capterra, Inc., during 2015. Each of these businesses assist clients with selecting business software. The aggregate purchase price was $206.9 million in cash, which included $25.6 million placed in escrow which the Company expects to pay in late 2017. Net of cash acquired with the businesses and for cash flow reporting purposes the Company paid $196.2 million in cash in 2015. The Company may also be required to pay up to an additional $32.0 million in cash in the future subject to the continuing employment of certain key employees. The $32.0 million is being recognized as compensation expense over three years and is being reported in Acquisition and Integration Charges in the Consolidated Statements of Operations. The Company recorded $79.6 million and $138.1 million of amortizable intangible assets and goodwill, respectively, and $10.8 million in liabilities on a net basis for these acquisitions. 2014 100% of the outstanding shares of three companies in 2014: Software Advice, Inc., Market-Visio Oy, and SircleIT Inc. Software Advice, Inc. assists clients with software purchases, while Market-Visio Oy was previously an independent sales agent of Gartner research products. SircleIT Inc. is a developer of cloud-based knowledge automation software. The aggregate purchase price of these businesses was $115.4 million in cash. Net of cash acquired with the businesses and for cash flow reporting purposes the Company paid $109.9 million . The Company also placed an additional $14.4 million in escrow, of which $0.8 million was paid in 2015. The Company recorded $110.3 million of goodwill and other intangible assets and $5.1 million of other assets on a net basis for these acquisitions. The Company also paid an additional $31.9 million in cash related to the continuing employment of certain key employees which was recognized as compensation expense over the two -year service period of the employees and was classified in Acquisition and Integration Charges in the Consolidated Statements of Operations. The Company paid $9.2 million of the $31.9 million in 2015 and $22.7 million in 2016, of which $13.6 million was paid from escrow.

Other Assets

Other Assets	12 Months Ended
	Dec. 31, 2016
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
OTHER ASSETS	OTHER ASSETS Other assets consist of the following (in thousands): December 31, 2016 2015 Benefit plan-related assets $ 45,958 $ 42,168 Non-current deferred tax assets 27,275 26,418 Other 14,046 38,298 Total other assets $ 87,279 $ 106,884

Accounts Payable, Accrued, and

Accounts Payable, Accrued, and Other Liabilities	12 Months Ended
	Dec. 31, 2016
Payables and Accruals [Abstract]
ACCOUNTS PAYABLE, ACCRUED, AND OTHER LIABILITIES	ACCOUNTS PAYABLE, ACCRUED, AND OTHER LIABILITIES Accounts payable and accrued liabilities consist of the following (in thousands): December 31, 2016 2015 Accounts payable $ 41,009 $ 31,570 Payroll and employee benefits payable 87,821 85,575 Severance and retention bonus payable 22,425 38,557 Bonus payable 105,549 90,989 Commissions payable 68,273 66,054 Taxes payable 20,378 13,714 Other accrued liabilities 95,316 61,232 Total accounts payable and accrued liabilities $ 440,771 $ 387,691 Other liabilities consist of the following (in thousands): December 31, 2016 2015 Non-current deferred revenue $ 11,289 $ 7,603 Long-term taxes payable 19,737 13,784 Deferred rent 13,747 15,207 Benefit plan-related liabilities 67,747 62,675 Other 69,297 94,325 Total other liabilities $ 181,817 $ 193,594

Debt

Debt	12 Months Ended
	Dec. 31, 2016
Debt Disclosure [Abstract]
DEBT	DEBT 2016 Credit Agreement The Company has a $1.8 billion credit arrangement that it entered into in mid-2016 (the “2016 Credit Agreement”) that provides for a five -year, $600.0 million term loan and a $1.2 billion revolving credit facility. The term loan will be repaid in 16 consecutive quarterly installments which commenced on September 30, 2016 , plus a final payment due in June 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 2021 , at which time all amounts borrowed must be repaid. Amounts borrowed under the 2016 Credit Agreement bear interest at a rate equal to, at Gartner’s option, either: (1) the greater of: (i) the administrative agent’s prime rate; (ii) the average rate on overnight federal funds plus 1/2 of 1% ; (iii) the eurodollar rate (adjusted for statutory reserves) plus 1% ; in each case plus a margin equal to between 0.125% and 0.50% 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 3.00% , depending on Gartner’s leverage ratio as of the end of the four consecutive fiscal quarters most recently ended. The 2016 Credit Agreement contains certain customary restrictive loan covenants, including, among others, financial covenants requiring a maximum leverage ratio, a minimum interest expense coverage ratio, and covenants limiting Gartner’s ability to incur indebtedness, grant liens, make acquisitions, be acquired, dispose of assets, pay dividends, repurchase stock, make capital expenditures, make investments and enter into certain transactions with affiliates. The Company was in full compliance with the loan covenants as of December 31, 2016 . The 2016 Credit Agreement was amended on January 20, 2017 to permit the acquisition of CEB (see Note 16—Subsequent Events) and the incurrence of an additional $1.375 billion senior secured term loan B facility, $300.0 million 364-day senior unsecured bridge facility and a senior unsecured high-yield bridge facility of up to $600.0 million (or the issuance of a corresponding amount of debt securities) to finance, in part, the acquisition and repay certain debt of CEB, and to modify certain covenants. The following table summarizes the Company’s total outstanding borrowings (in thousands): Amount Outstanding December 31, Amount Outstanding December 31, Description: 2016 2015 Term loan (1) $ 585,000 $ 380,000 Revolver (1), (2) 115,000 440,000 Other (3) 2,500 5,000 Subtotal (4), (5) 702,500 825,000 Less: deferred financing fees (8,109 ) (6,169 ) Net carrying amount $ 694,391 $ 818,831 (1) The contractual annual interest rate as of December 31, 2016 on both the term loan and the revolver was 2.15% , which consisted of a floating Eurodollar base rate of 0.77% plus a margin of 1.38% . However, the Company has interest rate swap contracts which effectively convert the floating eurodollar base rate to a fixed base rate on $700.0 million of borrowings (see below). (2) The Company had $1.1 billion of available borrowing capacity on the revolver (not including the expansion feature) as of December 31, 2016 . (3) Consists of a State of Connecticut economic development loan with a 3.0% fixed rate of interest that matures in 2022. During 2016, $2.5 million of the $5.0 million original balance was extinguished after the Company met certain employment targets. As a result of the loan extinguishment, the Company recorded a gain of $2.5 million , which was recorded in Other income (expense), net in the Consolidated Statements of Operations. (4) As of December 31, 2016, $30.0 million of the debt was classified as short-term and $672.5 million was classified as long- term on the Consolidated Balance Sheet. (5) The weighted-average annual interest rate on the Company's outstanding debt as of December 31, 2016 was 2.80% , which includes the impact of the Company's interest swap contracts, which are discussed below. Interest Rate Hedges As of December 31, 2016, the Company had three fixed-for-floating interest rate swap contracts. The swaps have a total notional value of $700.0 million and mature in late 2019. The Company designates the swaps 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 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 No. 815. Since the swaps hedge forecasted interest payments, changes in the fair value of the swaps are recorded in accumulated other comprehensive (loss) income, 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 December 31, 2016. The interest rate swaps had a total negative fair value to the Company as of December 31, 2016 and 2015 of $2.3 million and $5.1 million , respectively, which is deferred and classified in accumulated other comprehensive (loss) income, net of tax effect. Letters of Credit The Company had $8.5 million of letters of credit and related guarantees outstanding at year-end 2016. The Company issues these instruments in the ordinary course of business to facilitate transactions with customers and others.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES Contractual Lease Commitments. The Company leases various facilities, computer and office equipment, furniture, and other assets under non-cancelable operating lease agreements expiring between 2017 and 2032 . The future minimum annual cash payments under these operating lease agreements as of December 31, 2016 was as follows (in thousands): Year ended December 31, 2017 $ 49,250 2018 41,074 2019 33,640 2020 25,452 2021 22,898 Thereafter 142,930 Total minimum lease payments $ 315,244 Legal Matters. We are involved in various legal and administrative proceedings and litigation arising in the ordinary course of business. The outcome of these individual matters is not predictable at this time. However, we believe that the ultimate resolution of these matters, after considering amounts already accrued and insurance coverage, will not have a material adverse effect on our financial position, results of operations, or cash flows in future periods. Indemnifications. 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 December 31, 2016, we did not have any indemnification agreements that could require material payments.

Stockholders' Equity (Deficit)

Stockholders' Equity (Deficit)	12 Months Ended
	Dec. 31, 2016
Equity [Abstract]
STOCKHOLDERS’ EQUITY (DEFICIT)	STOCKHOLDERS’ EQUITY (DEFICIT) Common stock. Holders of Gartner’s Common Stock, par value $.0005 per share (“Common Stock”) are entitled to one vote per share on all matters to be voted by stockholders. The Company does not currently pay cash dividends on its Common Stock. Also, our 2016 Credit Agreement contains a negative covenant which may limit our ability to pay dividends. The following table summarizes transactions relating to Common Stock for the three years ended December 31, 2016: Issued Shares Treasury Stock Shares Balance at December 31, 2013 156,234,415 64,268,863 Issuances under stock plans (1,452,419 ) Purchases for treasury (1) 5,897,446 Balance at December 31, 2014 156,234,415 68,713,890 Issuances under stock plans — (1,003,746 ) Purchases for treasury (1) — 6,186,101 Balance at December 31, 2015 156,234,415 73,896,245 Issuances under stock plans — (923,696 ) Purchases for treasury (1) — 610,623 Balance at December 31, 2016 156,234,415 73,583,172 (1) The Company used a total of $59.0 million , $509.0 million , and $432.0 million in cash for share repurchases in 2016, 2015, and 2014, respectively. Share repurchase authorization. The Company has a $1.2 billion board authorization to repurchase the Company's common stock. 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 2016 Credit Agreement. As of December 31, 2016, approximately $1.1 billion of this authorization remained available for repurchases. Opening adjustment to accumulated earnings. The Company early adopted FASB ASU No. 2016-09, " Improvements to Employee Share-Based Payment Accounting" in 2016. The adoption of ASU No. 2016-09 resulted in a $0.3 million decrease to the Company's opening accumulated earnings balance effective January 1, 2016. Note 1 — Business and Significant Accounting Policies provides additional information regarding ASU No. 2016-09. Accumulated other comprehensive (loss) income, net. The following tables disclose information about changes in accumulated other comprehensive (loss) income ("AOCL/I"), a component of equity, by component and the related amounts reclassified out of AOCL/I to income during the years indicated (net of tax, in thousands) (1): 2016 Interest Rate Swaps Defined Benefit Pension Plans Foreign Currency Translation Adjustments 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 (2,902 ) (1,113 ) (5,986 ) (10,001 ) Reclassifications from AOCL/I to income during the period (2), (3) 4,572 148 — 4,720 Other comprehensive income (loss) for the period 1,670 (965 ) (5,986 ) (5,281 ) Balance - December 31, 2016 $ (1,409 ) $ (5,797 ) $ (42,477 ) $ (49,683 ) 2015 Interest Rate Swaps Defined Benefit Pension Plans Foreign Currency Translation Adjustments 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 (6,356 ) 986 (23,089 ) (28,459 ) Reclassifications from AOCL/I to income during the period (2), (3) 5,017 210 — 5,227 Other comprehensive (loss) income for the period (1,339 ) 1,196 (23,089 ) (23,232 ) Balance - December 31, 2015 $ (3,079 ) $ (4,832 ) $ (36,491 ) $ (44,402 ) (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 11 – 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 13 – Employee Benefits for information regarding the Company’s defined benefit pension plans.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 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 December 31, 2016, the Company had 6.2 million shares of its Common Stock, par value $.0005 per share 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 No. 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. Adoption of ASU No. 2016-09 The Company early 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 Consolidated Statements of Operations. Prior to ASU No. 2016-09, excess tax benefits or deficiencies were recorded in additional paid-in capital in Stockholders' Equity (Deficit) in the Consolidated Balance Sheets. ASU No. 2016-09 also requires that excess tax benefits related to stock-based compensation awards be reported as cash flows from operating activities on the Consolidated Statements 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 optionally selected to change its accounting policy and account for forfeitures as they occur, the impact of which was not material. The adoption of ASU No. 2016-09 increased the Company's diluted net income per share for 2016 by $0.12 per share. In addition, ASU No. 2016-09 increased the Company's operating cash flow in 2016 by $10.0 million with a corresponding decrease in financing activities cash flow. The Company's financial results for periods prior to 2016 were not impacted. Stock-Based Compensation Expense The Company recognized the following amounts of stock-based compensation expense by award type for the years ended December 31 (in millions): Award type: 2016 2015 2014 Stock appreciation rights $ 5.6 $ 5.7 $ 5.0 Common stock equivalents 0.7 0.6 0.6 Restricted stock units 40.4 39.8 33.2 Total (1) $ 46.7 $ 46.1 $ 38.8 Stock-based compensation expense was recognized by line item in the Consolidated Statements of Operations for the years ended December 31 as follows (in millions): Amount recorded in: 2016 2015 2014 Costs of services and product development $ 21.9 $ 20.6 $ 17.6 Selling, general, and administrative 24.8 25.5 21.2 Total (1) $ 46.7 $ 46.1 $ 38.8 (1) Includes charges of $19.4 million , $20.1 million , and $14.8 million in 2016, 2015 and 2014, respectively, for awards to retirement-eligible employees. These awards vest on an accelerated basis. As of December 31, 2016, the Company had $49.4 million of total unrecognized stock-based compensation cost, which is expected to be recognized as stock-based compensation expense over the remaining weighted-average service period of approximately 2.3 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 No. 505: Stock Appreciation Rights Stock-settled stock appreciation rights (SARs) permit the holder to participate in the appreciation of the Common Stock. SARs are settled in shares of Common Stock by the employee once the applicable vesting criteria have been met. SARs vest ratably over a four -year service period and expire seven years from the grant date. The fair value of SARs awards is recognized as compensation expense on a straight-line basis over four years . SARs have only been awarded to the Company’s executive officers. When SARs are exercised, the number of shares of Common Stock issued is calculated as follows: (1) the total proceeds from the SARs exercise (calculated as the closing price of the Common Stock on the date of exercise less the exercise price of the SARs, multiplied by the number of SARs exercised) is divided by (2) the closing price of the Common Stock as reported on the New York Stock Exchange on the exercise date. The Company withholds a portion of the shares of Common Stock issued upon exercise to satisfy statutory tax withholding requirements. SARs recipients do not have any stockholder rights until after actual shares of Common Stock are issued in respect of the award, which is subject to the prior satisfaction of the vesting and other criteria relating to such grants. The following table summarizes changes in SARs outstanding for the year ended December 31, 2016: Stock Appreciation Rights (SARs) (in millions) Per Share Weighted- Average Exercise Price Per Share Weighted- Average Grant Date Fair Value Weighted-Average Remaining Contractual Term (in years) Outstanding at December 31, 2015 1.3 $ 56.47 $ 14.92 4.46 years Granted 0.4 80.06 16.50 6.11 years Forfeited — — — — Exercised (0.4 ) 40.65 13.03 na Outstanding at December 31, 2016 (1), (2) 1.3 $ 66.22 $ 15.77 4.40 years Vested and exercisable at December 31, 2016 (2) 0.5 $ 55.15 $ 14.91 3.25 years na = not applicable (1) At December 31, 2016, 0.8 million of these SARs were unvested. The Company expects that substantially all of these unvested awards will vest in future periods. (2) At December 31, 2016, SARs outstanding had an intrinsic value of $46.8 million . SARs vested and exercisable had an intrinsic value of $25.1 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 for the years ended December 31: 2016 2015 2014 Expected dividend yield (1) — % — % — % Expected stock price volatility (2) 22 % 24 % 25 % Risk-free interest rate (3) 1.1 % 1.5 % 1.3 % Expected life in years (4) 4.39 4.41 4.43 (1) The dividend yield assumption is based on both 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 the implied volatility from publicly traded options in 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, the 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 year ended December 31, 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 81.41 Vested and released (0.6 ) 58.15 Forfeited (0.1 ) 69.40 Outstanding at December 31, 2016 (2), (3) 1.3 $ 73.19 (1) The 0.6 million RSUs granted in 2016 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 of performance-based RSUs was determined based on the achievement of an increase in the Company's total contract value in 2016. Total contract value represents the value attributable to all of our subscription-related contracts. (2) The Company expects that substantially all of the outstanding awards at December 31, 2016 will vest in future periods. (3) The weighted-average remaining contractual term of the outstanding RSUs is approximately 1.1 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 the director terminates unless the director has elected an accelerated release. The fair value of the CSEs 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 for the year ended December 31, 2016: Common Stock Equivalents (CSEs) Per Share Weighted-Average Grant Date Fair Value Outstanding at December 31, 2015 105,664 $ 19.57 Granted 7,069 93.90 Converted to common stock (5,395 ) 93.90 Outstanding at December 31, 2016 107,338 $ 20.74 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 December 31, 2016, the Company had approximately 0.9 million shares available for purchase under the ESP Plan. The ESP Plan is considered non-compensatory under FASB ASC Topic No. 718, and as a result the Company does not record stock-based compensation expense for employee share purchases. The Company received $9.3 million , $7.5 million , and $7.8 million in cash from share purchases under the ESP Plan during 2016, 2015, and 2014, respectively.

Computation of Earnings Per Sha

Computation of Earnings Per Share	12 Months Ended
	Dec. 31, 2016
Earnings Per Share [Abstract]
COMPUTATION OF EARNINGS PER SHARE	COMPUTATION OF EARNINGS PER SHARE Basic earnings per share (“EPS”) is computed by dividing net income by the weighted average number of shares of Common Stock outstanding for the period. Diluted EPS reflects the potential dilution of securities that could share in earnings. When the impact of common share equivalents is anti-dilutive, they are excluded from the calculation. The following table sets forth the reconciliation of the basic and diluted earnings per share computations for the years ended December 31 (in thousands, except per share amounts): 2016 2015 2014 Numerator: Net income used for calculating basic and diluted earnings per common share $ 193,582 $ 175,635 $ 183,766 Denominator: (1) Weighted average number of common shares used in the calculation of basic earnings per share 82,571 83,852 89,337 Common share equivalents associated with stock-based compensation plans 1,249 1,204 1,382 Shares used in the calculation of diluted earnings per share 83,820 85,056 90,719 Earnings per share: Basic $ 2.34 $ 2.09 $ 2.06 Diluted $ 2.31 $ 2.06 $ 2.03 (1) The Company repurchased 0.6 million , 6.2 million , and 5.9 million shares of its Common Stock in 2016, 2015, and 2014, respectively. The following table presents the number of common share equivalents that were not included in the computation of diluted EPS in the table above because the effect would have been anti-dilutive. During periods with net income, these common share equivalents were anti-dilutive because their exercise price was greater than the average market value of a share of Common Stock during the period. 2016 2015 2014 Anti-dilutive common share equivalents as of December 31 (in millions): 0.2 0.3 0.3 Average market price per share of Common Stock during the year $ 92.58 $ 86.02 $ 73.27

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2016
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES The following is a summary of the components of the Company's income before income taxes for the years ended December 31 (in thousands): 2016 2015 2014 U.S. $ 182,178 $ 165,848 $ 188,963 Non-U.S. 106,253 106,363 85,720 Income before income taxes $ 288,431 $ 272,211 $ 274,683 The expense for income taxes on the above income consists of the following components (in thousands): 2016 2015 2014 Current tax expense: U.S. federal $ 58,616 $ 48,801 $ 49,281 State and local 11,292 10,300 5,135 Foreign 27,536 23,225 16,653 Total current 97,444 82,326 71,069 Deferred tax (benefit) expense: U.S. federal (61 ) (884 ) (6,670 ) State and local (349 ) (702 ) 6,477 Foreign (1,626 ) 1,550 779 Total deferred (2,036 ) (36 ) 586 Total current and deferred 95,408 82,290 71,655 Benefit (expense) relating to interest rate swaps used to increase (decrease) equity (1,113 ) 893 (1,442 ) Benefit from stock transactions with employees used to increase equity 52 13,960 18,704 Benefit (expense) relating to defined-benefit pension adjustments used to increase (decrease) equity 502 (567 ) 2,000 Total tax expense $ 94,849 $ 96,576 $ 90,917 Long-term deferred tax assets and liabilities are comprised of the following (in thousands): December 31, 2016 2015 Accrued liabilities $ 62,439 $ 67,888 Loss and credit carryforwards 7,766 8,522 Assets relating to equity compensation 25,569 22,686 Other assets 6,652 6,712 Gross deferred tax assets 102,426 105,808 Property, equipment, and leasehold improvements (11,796 ) (9,904 ) Intangible assets (43,548 ) (55,275 ) Prepaid expenses (32,971 ) (28,535 ) Other liabilities (7,925 ) (7,244 ) Gross deferred tax liabilities (96,240 ) (100,958 ) Valuation allowance (1,431 ) (1,828 ) Net deferred tax assets $ 4,755 $ 3,022 Net deferred tax assets and net deferred tax liabilities were $27.3 million and $22.5 million as of December 31, 2016 , respectively, and $26.4 million and $23.4 million as of December 31, 2015 , respectively, and are reported in Other assets and Other liabilities in the Consolidated Balance Sheets. Management has concluded it is more likely than not that the reversal of deferred tax liabilities and results of future operations will generate sufficient taxable income to realize the deferred tax assets, net of the valuation allowance at December 31, 2016. The valuation allowances of $1.4 million as of December 31, 2016 and $1.8 million as of 2015 , primarily relate to net operating losses which are not likely to be realized. As of December 31, 2016 , the Company had state and local tax net operating loss carryforwards of $2.4 million , of which $0.1 million expire within one to five years and $2.3 million expire within six to fifteen years . The Company also had state tax credits of $1.9 million , a majority of which will expire in five to six years years. As of December 31, 2016, the Company had non-U.S. net operating loss carryforwards of $19.5 million , of which $0.9 million expire over the next 20 years and $18.6 million can be carried forward indefinitely. In addition, the Company also had foreign tax credit carryforwards of $0.6 million , the majority of which will expire at the end of 2027. These amounts have been reduced for associated unrecognized tax benefits, consistent with FASB ASU No. 2013-11. The differences between the U.S. federal statutory income tax rate and the Company’s effective tax rate on income before income taxes for the years ended December 31 follow: 2016 2015 2014 Statutory tax rate 35.0 % 35.0 % 35.0 % State income taxes, net of federal benefit 2.4 3.3 3.1 Effect of non-U.S. operations (5.9 ) (6.5 ) (6.3 ) Record (release) reserve for tax contingencies 3.2 1.7 1.8 Excess tax benefits from stock based compensation (3.8 ) — — Nondeductible acquisition costs 2.6 0.8 0.1 Record (release) valuation allowance (0.2 ) 0.5 — Other items, net (0.4 ) 0.7 (0.6 ) Effective tax rate 32.9 % 35.5 % 33.1 % As disclosed in Note 1 — Business and Significant Accounting Policies, 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 $10.0 million for the twelve months ended December 31, 2016. For 2016 and 2015 , state income taxes, net of federal tax benefit, include approximately $(0.3) million and $1.6 million , respectively, of benefit/(expense) relating to economic development tax credits associated with the renovation of the Company’s Stamford headquarters facility. In July 2015, the United States Tax Court (the “Court”) issued an opinion relating to the treatment of stock-based compensation expense in an inter-company cost-sharing arrangement. In its opinion, the Court held that affiliated companies may exclude stock-based compensation expense from their cost-sharing arrangement. The Internal Revenue Service is appealing the decision. Because of uncertainty related to the final resolution of this litigation and the recognition of potential benefits to the Company, the Company has not recorded any financial statement benefit associated with this decision. The Company will monitor developments related to this case and the potential impact of those developments on the Company’s consolidated financial statements As of December 31, 2016 and December 31, 2015 , the Company had unrecognized tax benefits of $37.1 million and $25.9 million , respectively. The increase is primarily attributable to positions taken with respect to the exclusion of stock-based compensation expense from the Company's cost-sharing arrangement and certain state refund claims. The unrecognized tax benefits as of December 31, 2016 related primarily to the utilization of certain tax attributes, state income tax positions, the ability to realize certain refund claims, and intercompany transactions. It is reasonably possible that unrecognized tax benefits will be decreased by $1.7 million within the next 12 months due to anticipated closure of audits and the expiration of certain statutes of limitation. Included in the balance of unrecognized tax benefits at December 31, 2016 are potential benefits of $33.4 million that if recognized would reduce the effective tax rate on income from continuing operations. Also included in the balance of unrecognized tax benefits as of December 31, 2016 are potential benefits of $3.7 million that, if recognized, would result in adjustments to other tax accounts, primarily deferred taxes. The following is a reconciliation of the beginning and ending amount of unrecognized tax benefits, excluding interest and penalties, for the years ended December 31 (in thousands): 2016 2015 Beginning balance $ 25,911 $ 20,645 Additions based on tax positions related to the current year 7,086 5,150 Additions for tax positions of prior years 6,443 7,839 Reductions for tax positions of prior years (496 ) (3,880 ) Reductions for expiration of statutes (1,006 ) (2,287 ) Settlements (544 ) (960 ) Change in foreign currency exchange rates (295 ) (596 ) Ending balance $ 37,099 $ 25,911 The Company accrues interest and penalties related to unrecognized tax benefits in its income tax provision. As of December 31, 2016 and 2015, the Company had $4.3 million and $3.7 million , respectively, of accrued interest and penalties related to unrecognized tax benefits. These amounts are in addition to the unrecognized tax benefits disclosed above. The total amount of interest and penalties recognized in the income tax provision for both the years ended December 31, 2016 and December 31, 2015 was $0.9 million . The number of years with open statutes of limitation varies depending on the tax jurisdiction. The Company’s statutes are open with respect to the U.S. federal jurisdiction for 2013 and forward, and India for 2003 and forward. For other major taxing jurisdictions including the U.S. states, the United Kingdom, Canada, Japan, France, and Ireland, the Company's statutes vary and are open as far back as 2009. Under U.S. GAAP rules, no provision for income taxes that may result from the remittance of earnings held overseas is required if the Company has the ability and intent to indefinitely reinvest such funds overseas. Our current plans do not demonstrate a need to repatriate these undistributed earnings to fund our U.S. operations or otherwise satisfy the liquidity needs of our U.S operations. We intend to reinvest these earnings in our non-U.S. operations, except in instances in which the repatriation of these earnings would result in minimal additional tax. As a result, the Company has not recognized income tax expense that may result from the remittance of these earnings. The accumulated undistributed earnings of non-U.S. subsidiaries were approximately $340.0 million as of December 31, 2016. The income tax that would be payable if such earnings were not indefinitely invested is estimated at $69.0 million .

Derivatives and Hedging

Derivatives and Hedging	12 Months Ended
	Dec. 31, 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 No. 815, which requires all derivatives, including derivatives designated as accounting hedges, to be recorded on the balance sheet at fair value. The following tables provide information regarding the Company’s outstanding derivatives contracts as of and for the years ended December 31 (in thousands, except for number of outstanding contracts): 2016 Derivative Contract Type Number of Outstanding Contracts Contract Notional Amount Fair Value Asset (Liability) (3) Balance Sheet Line Item AOCI Unrealized (Loss), Net Of Tax Interest rate swaps (1) 3 $ 700,000 $ (2,349 ) Other liabilities $ (1,409 ) Foreign currency forwards (2) 84 86,946 (320 ) Other current assets — Total 87 $ 786,946 $ (2,669 ) $ (1,409 ) 2015 Derivative Contract Type Number of Outstanding Contracts Contract Notional Amount Fair Value Asset (Liability) (3) Balance Sheet Line Item AOCI Unrealized (Loss), Net Of Tax Interest rate swap (1) 3 $ 700,000 $ (5,132 ) Other liabilities $ (3,079 ) Foreign currency forwards (2) 102 193,610 235 Other current assets — 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 the fair value of the swaps are deferred and are recorded in AOCL/I, net of tax effect (see Note 5 — 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 outstanding contracts at December 31, 2016 matured by the end of January 2017. (3) See Note 12 — Fair Value Disclosures for the determination of the fair value of these instruments. At December 31, 2016, 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 Consolidated Statements of Operations for derivative contracts for the years ended December 31 (in millions): Amount recorded in: 2016 2015 2014 Interest expense (1) $ 7.6 $ 8.5 $ 4.1 Other expense (income), net (2) 0.3 0.1 (0.5 ) Total expense $ 7.9 $ 8.6 $ 3.6 (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	12 Months Ended
	Dec. 31, 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 approximates their fair value due to their short-term nature. The Company’s financial instruments also include its outstanding borrowings under the 2016 Credit Agreement, and at December 31, 2016, the Company had $700.0 million of floating rate debt outstanding under this arrangement, which is carried at amortized cost. The Company believes the carrying amount of the outstanding borrowings reasonably approximates 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 Company’s Consolidated Balance Sheets. FASB ASC Topic No. 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 goodwill (information regarding the Company's periodic assessment of goodwill is included in Note 1 — Business and Significant Accounting Policies). 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: December 31, December 31, Assets: Values based on Level 1 inputs: Deferred compensation plan assets (1) $ 10,247 $ 8,671 Total Level 1 inputs $ 10,247 $ 8,671 Values based on Level 2 inputs: Deferred compensation plan assets (1) $ 27,847 $ 25,474 Foreign currency forward contracts (2) 165 610 Total Level 2 inputs $ 28,012 $ 26,084 Total Assets $ 38,259 $ 34,755 Liabilities: Values based on Level 2 inputs: Deferred compensation plan liabilities (1) $ 43,075 $ 39,071 Foreign currency forward contracts (2) 485 375 Interest rate swap contracts (3) 2,349 5,132 Total Level 2 inputs $ 45,909 $ 44,578 Total Liabilities $ 45,909 $ 44,578 (1) The Company has a deferred compensation plan for the benefit of certain highly compensated officers, managers and other key employees (see Note 13 — Employee Benefits). The assets consist of investments in money market and mutual funds, and company-owned life insurance contracts. The money market funds consist of cash equivalents while the mutual fund investments consist of publicly-traded and quoted equity shares. The Company considers the fair value of these assets to be based on Level 1 inputs, and these assets had a fair value of $10.2 million and $8.7 million as of December 31, 2016 and 2015, respectively. The carrying amount of the life insurance contracts equals their cash surrender value. Cash surrender value represents the estimated amount that the Company would receive upon termination of the contract, which approximates fair value. The Company considers the life insurance contracts to be valued based on a Level 2 input, and these assets had a fair value of $27.8 million and $25.5 million at December 31, 2016 and 2015, respectively. 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 (see Note 11 — Derivatives and Hedging). Valuation of the foreign currency forward contracts is based on 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 variability of interest payments on its borrowings (see Note 11 — Derivatives and Hedging). The fair value of the swaps is based on mark-to-market valuations provided 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	12 Months Ended
	Dec. 31, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
EMPLOYEE BENEFITS	EMPLOYEE BENEFITS Defined contribution plan. The Company has a savings and investment plan (the “401k Plan”) covering substantially all U.S. employees. Company contributions are based upon the level of employee contributions, up to a maximum of 4% of the employee’s eligible salary, subject to an annual maximum. For 2016, the maximum match was $7,200 . Amounts expensed in connection with the 401k Plan totaled $22.9 million , $20.0 million , and $17.4 million , in 2016, 2015, and 2014, respectively. Deferred compensation plan. The Company has a supplemental deferred compensation plan for the benefit of certain highly compensated officers, managers and other key employees, which is structured as a rabbi trust. The plan’s investment assets are recorded in Other assets on the Consolidated Balance Sheets at fair value. The value of these assets was $38.1 million and $34.1 million at December 31, 2016 and 2015, respectively (see Note 12 — Fair Value Disclosures for fair value information). The corresponding deferred compensation liability, which was $43.1 million and $39.1 million at December 31, 2016 and 2015, respectively, is carried at fair value, and is adjusted with a corresponding charge or credit to compensation expense to reflect the fair value of the amount owed to the employees and is classified in Other liabilities on the Consolidated Balance Sheets. Compensation expense recognized for the plan was $0.1 million , $0.5 million , and $0.6 million , in 2016, 2015, and 2014, respectively. 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 No. 715 and 960. The following are the components of defined benefit pension expense for the years ended December 31 (in thousands): 2016 2015 2014 Service cost $ 2,780 $ 2,620 $ 2,630 Interest cost 850 790 1,190 Expected return on plan assets (375 ) (345 ) (540 ) Recognition of actuarial loss 200 300 75 Recognition of termination benefits — 85 30 Total defined benefit pension plan expense (1) $ 3,455 $ 3,450 $ 3,385 (1) Pension expense is classified in SG&A in the Consolidated Statements of Operations. The following are the key assumptions used in the computation of pension expense for the years ended December 31: 2016 2015 2014 Weighted-average discount rate (1) 1.78 % 2.19 % 2.15 % Average compensation increase 2.67 % 2.66 % 2.65 % (1) Discount rates are typically determined by utilizing the yields on long-term corporate or government bonds in the relevant country with a duration consistent with the expected term of the underlying pension obligations. The following table provides information related to changes in the projected benefit obligation for the years ended December 31 (in thousands): 2016 2015 2014 Projected benefit obligation at beginning of year $ 35,870 $ 38,115 $ 34,585 Service cost 2,780 2,620 2,630 Interest cost 850 790 1,190 Actuarial loss (gain) due to assumption changes and plan experience 1,480 (1,190 ) 6,300 Additions and contractual termination benefits — 85 30 Benefits paid (1) (1,640 ) (775 ) (1,350 ) Foreign currency impact (940 ) (3,775 ) (5,270 ) Projected benefit obligation at end of year (2) $ 38,400 $ 35,870 $ 38,115 (1) The Company projects the following benefit payments will be made in future years to plan participants: $1.4 million in 2017; $2.0 million in 2018; $1.1 million in 2019, $1.5 million in 2020, $1.5 million in 2021; and $9.5 million in total in the five years thereafter. (2) Measured as of December 31. The following table provides information regarding the funded status of the plans and related amounts recorded in the Company’s Consolidated Balance Sheets as of December 31 (in thousands): Funded status of the plans: 2016 2015 2014 Projected benefit obligation $ 38,400 $ 35,870 $ 38,115 Pension plan assets at fair value (1) (14,465 ) (13,190 ) (13,220 ) Funded status – shortfall (2) $ 23,935 $ 22,680 $ 24,895 Amounts recorded in the Consolidated Balance Sheets for the plans: Other liabilities — accrued pension obligation (2) $ 23,935 $ 22,680 $ 24,895 Stockholders’ equity — deferred actuarial loss (3) $ (5,797 ) $ (4,832 ) $ (6,028 ) (1) The pension plan assets are held by third-party trustees and are invested in a diversified portfolio of equities, high quality government and corporate bonds, and other investments. The assets are primarily valued based on Level 1 and Level 2 inputs under the fair value hierarchy in FASB ASC Topic No. 820, with the majority of the invested assets considered to be of low-to-medium investment risk. The Company projects a future long-term rate of return on these plan assets of 2.7% , which it believes is reasonable based on the composition of the assets and both current and projected market conditions. For the year-ended December 31, 2016, the Company contributed $2.4 million to these plans, and benefits paid to participants were $1.6 million . (2) The Funded status - shortfall represents the amount of the projected benefit obligation that the Company has not funded with a third-party trustee. This amount is a liability of the Company and is recorded in Other liabilities on the Company’s Consolidated Balance Sheets. (3) The deferred actuarial loss as of December 31, 2016 is recorded in AOCL/I and will be reclassified out of AOCL/I and recognized as pension expense over approximately 13 years , subject to certain limitations set forth in FASB ASC Topic No. 715. The impact of this amortization on pension expense in 2017 is projected to result in approximately $0.3 million of additional expense. The amortization of deferred actuarial losses from AOCL/I to pension expense in each of the three years ended December 31, 2016 was immaterial. The Company also maintains a reinsurance asset arrangement with a large international insurance company whose purpose is to provide funding for benefit payments for one of the plans. The reinsurance asset is not a pension plan asset but is an asset of the Company. At December 31, 2016 and 2015, the reinsurance asset was recorded at its cash surrender value of $7.8 million and $7.9 million , respectively, and is classified in Other Assets on the Company's Consolidated Balance Sheets. The Company believes the cash surrender value approximates fair value and is equivalent to a Level 2 input under the FASB’s fair value framework in ASC Topic No. 820.

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2016
Segment Reporting [Abstract]
SEGMENT INFORMATION	SEGMENT INFORMATION The Company manages its business through three reportable segments: Research, Consulting and Events. Research primarily consists of subscription-based research products, access to research inquiry, peer networking services, and membership programs. Consulting consists of consulting, measurement engagements, and strategic advisory services. Events consists of various symposia, conferences and exhibitions. The Company evaluates reportable 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 Company earns revenue from clients in many countries. Other than the United States, there is no individual country in which revenues from external clients represent 10% or more of the Company’s consolidated revenues. Additionally, no single client accounted for 10% or more of total revenue and the loss of a single client, in management’s opinion, would not have a material adverse effect on revenues. The following tables present operating results for the Company’s reportable segments for the years ended December 31 (in thousands): Research Consulting Events Consolidated 2016 Revenues $ 1,829,721 $ 346,214 $ 268,605 $ 2,444,540 Gross contribution 1,267,760 107,585 136,655 1,512,000 Corporate and other expenses (1,206,859 ) Operating income $ 305,141 Research Consulting Events Consolidated 2015 Revenues $ 1,583,486 $ 327,735 $ 251,835 $ 2,163,056 Gross contribution 1,096,827 107,193 130,527 1,334,547 Corporate and other expenses (1,046,550 ) Operating income $ 287,997 Research Consulting Events Consolidated 2014 Revenues $ 1,445,338 $ 348,396 $ 227,707 $ 2,021,441 Gross contribution 1,001,914 119,931 112,384 1,234,229 Corporate and other expenses (948,067 ) Operating income $ 286,162 The following table provides a reconciliation of total segment gross contribution to net income for the periods indicated (in thousands): Twelve months ended December 31, 2016 2015 2014 Total segment gross contribution $ 1,512,000 $ 1,334,547 $ 1,234,229 Costs and expenses: Cost of services and product development - unallocated (1) 13,108 10,567 10,721 Selling, general and administrative 1,089,184 962,677 876,067 Depreciation and amortization 61,969 47,131 39,412 Acquisition and integration charges 42,598 26,175 21,867 Operating income 305,141 287,997 286,162 Interest expense and other 16,710 15,786 11,479 Provision for income taxes 94,849 96,576 90,917 Net income $ 193,582 $ 175,635 $ 183,766 (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. The Company’s revenues are generated primarily through direct sales to clients by domestic and international sales forces and a network of independent international sales agents. Most of the Company’s products and services are provided on an integrated worldwide basis, and because of this integrated delivery, it is not practical to precisely separate our revenues by geographic location. Accordingly, the separation set forth in the table below is based upon internal allocations, which involve certain management estimates and judgments. Revenues in the table are reported based on where the sale is fulfilled; “Other International” revenues are those attributable to all areas located outside of the United States and Canada, as well as Europe, Middle East, and Africa. Summarized information by geographic location as of and for the years ended December 31 follows (in thousands): 2016 2015 2014 Revenues: United States and Canada $ 1,519,748 $ 1,347,676 $ 1,204,476 Europe, Middle East and Africa 616,721 557,165 570,334 Other International 308,071 258,215 246,631 Total revenues $ 2,444,540 $ 2,163,056 $ 2,021,441 Long-lived assets: (1) United States and Canada $ 143,921 $ 163,933 $ 142,963 Europe, Middle East and Africa 42,326 31,130 34,093 Other International 24,630 16,050 13,282 Total long-lived assets $ 210,877 $ 211,113 $ 190,338 (1) Excludes goodwill and other intangible assets.

Valuation and Qualifying Accoun

Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2016
Valuation and Qualifying Accounts [Abstract]
VALUATION AND QUALIFYING ACCOUNTS	VALUATION AND QUALIFYING ACCOUNTS The Company maintains an allowance for losses which is composed of a bad debt allowance and a revenue reserve. Provisions are charged against earnings either as an increase to expense or a reduction in revenues. The following table summarizes activity in the Company’s allowance for the years ended December 31 (in thousands): Balance at Beginning of Year Additions Charged to Expense Additions Charged Against Revenues Deductions from Reserve Balance at End of Year 2016: Allowance for doubtful accounts and returns and allowances $ 6,900 $ 4,750 $ 4,850 $ (9,100 ) $ 7,400 2015: Allowance for doubtful accounts and returns and allowances $ 6,700 $ 3,480 $ 5,420 $ (8,700 ) $ 6,900 2014: Allowance for doubtful accounts and returns and allowances $ 7,000 $ 2,950 $ 3,240 $ (6,490 ) $ 6,700

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2016
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	SUBSEQUENT EVENTS On January 5, 2017, Gartner and CEB Inc. (NYSE: CEB) ("CEB"), an industry leader in providing best practice and talent management insights, announced that they had entered into a definitive agreement whereby Gartner will acquire all of the outstanding shares of CEB in a cash and stock transaction valued at approximately $2.6 billion . Gartner will also assume (and refinance) approximately $0.9 billion in CEB debt. The transaction has been unanimously approved by the Boards of Directors of both companies. Closing of the transaction is subject to the approval of CEB shareholders and the satisfaction of customary closing conditions, including applicable regulatory approvals. On February 1, 2017, the Federal Trade Commission granted early termination of the waiting period under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended, applicable to the proposed transaction. Closing of the transaction is expected to be completed in the first half of 2017. In connection with the proposed acquisition, the Company entered into a commitment letter for the purposes of financing the majority of the cash consideration payable and to refinance CEB’s indebtedness. The commitment letter provides for a total of $2.275 billion in additional financing, which includes a seven -year senior secured term loan B facility of up to $1.375 billion , a 364-day senior unsecured bridge facility of up to $300.0 million , and a senior unsecured high-yield bridge facility of up to $600.0 million . It is expected that on or prior to the closing of the CEB acquisition, senior unsecured notes will be issued and sold to pursuant to an offering pursuant to Rule 144A or a private placement in lieu of a portion of, or all of the drawings under, the high-yield bridge facility. The Company expects that the proceeds from the additional financing described above, together with its balance sheet cash and available borrowing capacity under its revolving credit facility, will be sufficient to pay the aggregate cash consideration and refinance CEB's indebtedness, as well as pay for certain fees and expenses incurred in connection with the acquisition. On February 6, 2017, the Company filed a Registration Statement on Form S-4 with the SEC pertaining to the shares of Gartner common stock that will be issued in connection with the proposed transaction and a prospectus relating to the special meeting of the CEB stockholders that will be called for purposes of voting on the proposed transaction.

Business and Significant Acco24

Business and Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of presentation	Basis of presentation. The accompanying consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“U.S. GAAP”), as defined in the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Topic 270 for financial information and with the applicable instructions of U.S. Securities & Exchange Commission (“SEC”) Regulation S-X. The fiscal year of Gartner represents the twelve-month period from January 1 through December 31. All references to 2016 , 2015 , and 2014 herein refer to the fiscal year unless otherwise indicated. Certain prior year balance sheet amounts have been reclassified to conform to the current year presentation.
Principles of consolidation	Principles of consolidation. The accompanying consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All significant intercompany transactions and balances have been eliminated.
Use of estimates	Use of estimates. The preparation of the accompanying consolidated financial statements requires management to make estimates and assumptions about future events. These estimates and the underlying assumptions affect the amounts of assets and liabilities reported, disclosures about contingent assets and liabilities, and reported amounts of revenues and expenses. Such estimates include the valuation of fees receivable, goodwill, intangible assets, and other long-lived assets, as well as tax accruals and other liabilities. In addition, estimates are used in revenue recognition, income tax expense, performance-based compensation charges, depreciation, and amortization. Management believes its use of estimates in the accompanying consolidated financial statements to be reasonable. Management 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.
Business Acquisitions	Business Acquisitions. The Company completed acquisitions in each of the three years ended December 31, 2016 and detailed information related to these acquisitions is included in Note 2 — Acquisitions. The Company accounts for acquisitions in accordance with the acquisition method of accounting as prescribed by FASB ASC Topic No. 805, Business Combinations. The acquisition method of accounting requires the Company to record the net assets and liabilities acquired based on their estimated fair values as of the acquisition date, with any excess of the consideration transferred over the estimated fair value of the net assets acquired, including identifiable intangible assets, to be recorded to goodwill. Under the acquisition method, the operating results of acquired companies are included in the Company's consolidated financial statements beginning on the date of acquisition. The determination of the fair values of intangible and other assets acquired in acquisitions requires management judgment and the consideration of a number of factors, significant among them the historical financial performance of the acquired businesses and projected performance, estimates surrounding customer turnover, as well as assumptions regarding the level of competition and the cost to reproduce certain assets. Establishing the useful lives of the intangibles also requires management judgment and the evaluation of a number of factors, among them projected cash flows and the likelihood of competition. The Company classifies charges that are directly-related to its acquisitions in the line Acquisition and Integration Charges in the Consolidated Statements of Operations, and the Company recorded $42.6 million , $26.2 million , and $21.9 million of such charges in 2016, 2015, and 2014, respectively. Included in these directly-related and incremental charges are legal, consulting, retention, severance, and accruals for cash payments subject to the continuing employment of certain key employees of the acquired companies.
Revenue Recognition	Revenue Recognition. Revenue is recognized in accordance with U.S. GAAP and SEC Staff Accounting Bulletin No. 104, Revenue Recognition (“SAB 104”). Revenues are only recognized once all required criteria for recognition have been met. The accompanying Consolidated Statements of Operations present revenues net of any sales or value-added taxes that we collect from customers and remit to government authorities. The Company’s revenues by significant source are as follows: Research Research revenues are mainly derived from subscription contracts for research products. The related revenues are deferred and recognized ratably over the applicable contract term. Fees derived from assisting organizations in selecting the right business software for their needs is recognized as earned when the leads are provided to vendors. The Company typically enters into subscription contracts for research products for twelve-month periods or longer. The majority of research contracts are billable upon signing, absent special terms granted on a limited basis from time to time. Research contracts are non-cancelable and non-refundable, except for government contracts that may have cancellation or fiscal funding clauses, which historically have not produced material cancellations. It is our policy to record the amount of the contract that is billable as a fee receivable at the time the contract is signed with a corresponding amount as deferred revenue, since the contract represents a legally enforceable claim. Consulting Consulting revenues, primarily derived from consulting, measurement and strategic advisory services (paid one-day analyst engagements), are principally generated from fixed fee or time and materials engagements. Revenues from fixed fee engagements are recognized on a proportional performance basis, while revenues from time and material engagements are recognized as work is delivered and/or services are provided. Revenues related to contract optimization engagements are contingent in nature and are only recognized upon satisfaction of all conditions related to their payment. Unbilled fees receivable associated with consulting engagements were $45.7 million at December 31, 2016 and $43.2 million at December 31, 2015 . Events Events revenues are deferred and recognized upon the completion of the related symposium, conference or exhibition. In addition, the Company defers certain costs directly related to events and expenses these costs in the period during which the related symposium, conference or exhibition occurs. The Company's policy is to defer only those costs, primarily prepaid site and production services costs, which are incremental and are directly attributable to a specific event. Other costs of organizing and producing our events, primarily Company personnel and non-event specific expenses, are expensed in the period incurred. At the end of each fiscal quarter, the Company assesses on an event-by-event basis whether the expected direct costs of producing a scheduled event will exceed the expected revenues. If such costs are expected to exceed revenues, the Company records the expected loss in the period determined.
Allowance for losses	Allowance for losses. The Company maintains an allowance for losses which is composed of a bad debt allowance and a sales reserve. Provisions are charged against earnings, either as a reduction in revenues or an increase to expense. The determination of the allowance for losses is based on historical loss experience, an assessment of current economic conditions, the aging of outstanding receivables, the financial health of specific clients, and probable losses.
Cost of services and product development	Cost of services and product development ( “COS” ). COS expense includes the direct costs incurred in the creation and delivery of our products and services.
Selling, general and administrative	Selling, general and administrative ( “SG&A” ). SG&A expense includes direct and indirect selling costs, general and administrative costs, and charges against earnings related to uncollectible accounts.
Commissions expense	Commission expense. The Company records commission obligations upon the signing of customer contracts and amortizes the deferred obligation as commission expense over the period in which the related revenues are earned.
Stock-based compensation expense	Stock-based compensation expense. The Company accounts for stock-based compensation in accordance with FASB ASC Topics No. 505 and 718 and SEC Staff Accounting Bulletins No. 107 (“SAB No. 107”) and No. 110 (“SAB No. 110”). Stock-based compensation cost is based on the fair value of the award on the date of grant, which is expensed over the related service period, net of estimated forfeitures. The service period is the period over which the employee performs the related services, which is normally the same as the vesting period. During 2016 , 2015 and 2014 , the Company recognized $46.7 million , $46.1 million and $38.8 million , respectively, of stock-based compensation expense, a portion of which is recorded in COS and SG&A in the Consolidated Statements of Operations. In 2016 the Company early adopted FASB Accounting Standards Update ("ASU") 2016-09, " Improvements to Employee Share-Based Payment Accounting." See the " Adoption of new accounting standards" section below for additional information.
Income tax expense	Income taxes expense. The Company uses the asset and liability method of accounting for income taxes. We estimate our income taxes in each of the jurisdictions where we operate. This process involves estimating our current tax expense together with assessing temporary differences resulting from differing treatment of items for tax and accounting purposes. These differences result in deferred tax assets and liabilities, which are included within our consolidated balance sheets. In assessing the realizability of deferred tax assets, management considers if it is more likely than not that some or all of the deferred tax assets will not be realized. We consider the availability of loss carryforwards, projected reversal of deferred tax liabilities, projected future taxable income, and ongoing prudent and feasible tax planning strategies in making this assessment. The Company recognizes the tax benefit from an uncertain tax position only if it is more likely than not the tax position will be sustained based on the technical merits of the position.
Cash and cash equivalents	Cash and cash equivalents. Includes cash and all highly liquid investments with original maturities of three months or less, which are considered cash equivalents. The carrying value of cash equivalents approximates fair value due to their short-term maturity. Investments with maturities of more than three months are classified as marketable securities. Interest earned is classified in Interest income in the Consolidated Statements of Operations.
Property, equipment and leasehold improvements	Property, equipment and leasehold improvements. The Company leases all of its facilities and certain equipment. These leases are all classified as operating leases in accordance with FASB ASC Topic 840. The cost of these operating leases, including any contractual rent increases, rent concessions, and landlord incentives, are recognized ratably over the life of the related lease agreement. Lease expense was $38.0 million , $33.8 million , and $31.5 million in 2016 , 2015 , and 2014 , respectively. Equipment, leasehold improvements, and other fixed assets owned by the Company are recorded at cost less accumulated depreciation. Except for leasehold improvements, these fixed assets are depreciated using the straight-line method over the estimated useful lives of the assets. Leasehold improvements are amortized using the straight-line method over the shorter of the estimated useful lives of the improvement or the remaining term of the related lease. The Company had total depreciation expense of $37.2 million , $33.8 million , and $31.2 million in 2016 , 2015 , and 2014 , respectively. The Company's total fixed assets, less accumulated depreciation and amortization, consisted of the following (in thousands): Useful Life December 31, Category (Years) 2016 2015 Computer equipment and software 2-7 $ 166,385 $ 148,195 Furniture and equipment 3-8 43,137 39,072 Leasehold improvements 2-15 96,603 87,103 $ 306,125 $ 274,370 Less — accumulated depreciation and amortization (184,519 ) (165,637 ) Property, equipment, and leasehold improvements, net $ 121,606 $ 108,733 The Company incurs costs to develop internal use software used in our operations, and certain of these costs meeting the criteria outlined in FASB ASC Topic No. 350 are capitalized and amortized over future periods.
Intangible assets	Intangible assets. The Company has finite-lived intangible assets which are amortized against earnings using the straight-line method over their expected useful lives.
Goodwill	Goodwill. Goodwill represents the excess of the purchase price of acquired businesses over the estimated fair value of the tangible and identifiable intangible net assets acquired. The evaluation of the recoverability of goodwill is performed in accordance with FASB ASC No. 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. If our annual goodwill impairment evaluation determines that the fair value of a reporting unit is less than its related carrying amount, we may recognize an impairment charge against earnings.
Impairment of long-lived assets	Impairment of long-lived assets. The Company's long-lived assets primarily consist of intangible assets other than goodwill and property, equipment, and leasehold improvements. The Company reviews its long-lived asset groups for impairment whenever events or changes in circumstances indicate that the carrying amount of the respective asset may not be recoverable. Such evaluation may be based on a number of factors including current and projected operating results and cash flows, changes in management’s strategic direction as well as external economic and market factors. The Company evaluates the recoverability of these assets by determining whether the carrying value can be recovered through undiscounted future operating cash flows. If events or circumstances indicate that the carrying value might not be recoverable based on undiscounted future operating cash flows, an impairment loss would be recognized. The amount of impairment, if any, is measured based on the difference between projected discounted future operating cash flows using a discount rate reflecting the Company’s average cost of funds and the carrying value of the asset.
Pension obligations	Pension obligations. The Company has defined-benefit pension plans in several of its international locations (see Note 13 — Employee Benefits). Benefits earned under these plans are generally based on years of service and level of employee compensation. The Company accounts for defined benefit plans in accordance with the requirements of FASB ASC Topic No. 715. The Company determines the periodic pension expense and related liabilities for these plans through actuarial assumptions and valuations.
Debt	Debt. The Company presents amounts borrowed in the Consolidated Balance Sheets at amortized cost, net of deferred financing fees. Interest accrued on amounts borrowed is classified in Interest expense in the Consolidated Statements of Operations.
Foreign currency exposure	Foreign currency exposure. The functional currency of our foreign subsidiaries is typically the local currency. All assets and liabilities of foreign subsidiaries are translated into U.S. dollars at exchange rates in effect at the balance sheet date. Income and expense items are translated at average exchange rates for the year. The resulting translation adjustments are recorded as foreign currency translation adjustments, a component of Accumulated other comprehensive (loss) income, net within the Stockholders’ Equity (Deficit) section of the Consolidated Balance Sheets. Currency transaction gains or losses arising from transactions denominated in currencies other than the functional currency of a subsidiary are recognized in results of operations in Other income (expense), net within the Consolidated Statements of Operations. The Company had net currency transaction losses of $(0.4) million , $(2.6) million , and $(1.7) million in 2016 , 2015 , and 2014 , respectively. The Company enters into foreign currency forward exchange contracts to mitigate the effects of adverse fluctuations in foreign currency exchange rates on these transactions. These contracts generally have a short duration and are recorded at fair value with both realized and unrealized gains and losses recorded in Other income (expense), net.
Comprehensive income	Comprehensive income. The Company reports comprehensive income in a separate statement called the Consolidated Statements of Comprehensive Income, which is included herein.
Fair value disclosures	Fair value disclosures. The Company has a limited number of assets and liabilities that are adjusted to fair value at each balance sheet date.
Concentrations of credit risk	Concentrations of credit risk. Assets that may subject the Company to concentration of credit risk consist primarily of short-term, highly liquid investments classified as cash equivalents, fees receivable, interest rate swaps, and a pension reinsurance asset. The majority of the Company’s cash equivalent investments and its interest rate swap contracts are with investment grade commercial banks. Fees receivable balances deemed to be collectible from customers have limited concentration of credit risk due to our diverse customer base and geographic dispersion. The Company’s pension reinsurance asset (see Note 13 — Employee Benefits) is maintained with a large international insurance company that was rated investment grade as of December 31, 2016 .
Stock repurchase programs	Stock repurchase programs. The Company records the cost to repurchase its own common shares to treasury stock. During 2016, 2015 and 2014, the Company used $59.0 million , $509.0 million , and $432.0 million , respectively, in cash for stock repurchases (see Note 7 — Stockholders’ Equity (Deficit). Shares repurchased by the Company are added to treasury shares and are not retired.
Adoption of new accounting standards and Accounting standards issued but not yet adopted	Adoption of new accounting standards . The Company adopted the following new accounting standards in the year ended December 31, 2016: Extraordinary Items — The Company adopted FASB ASU No. 2015-01, " Simplifying Income Statement Presentation by Eliminating the Concept of Extraordinary Items" ("ASU No. 2015-01") on January 1, 2016. ASU No. 2015-01 eliminated the concept of extraordinary items. Historically the concept caused uncertainty because it was somewhat unclear when an item should be considered both unusual and infrequent and it was rare that a transaction or event met the requirements. The adoption of ASU No. 2015-01 did not have an impact on the Company’s consolidated financial statements. Cloud Computing Arrangement Fees — The Company adopted FASB ASU No. 2015-05, " Customer’s Accounting for Fees Paid in a Cloud Computing Arrangement " ("ASU No. 2015-05) on January 1, 2016. ASU No. 2015-05 provides guidance regarding the costs related to cloud computing and hosting arrangements by identifying what portion of the cost relates to purchased software, if any, and what portion relates to paying for a service. The adoption of ASU No. 2015-05 did not have an impact on the Company’s consolidated financial statements. Business Combinations — The Company adopted FASB ASU No. 2015-16, " Business Combinations - Simplifying the Accounting for Measurement-Period Adjustments " ("ASU No. 2015-16") on January 1, 2016. ASU No. 2015-16 requires the recognition of adjustments to business combination provisional amounts, that are identified during the measurement period, in the reporting period in which the adjustments are determined. The effects of the adjustments to provisional amounts on depreciation, amortization or other income effects are required to be recognized in current-period earnings as if the accounting had been completed at the acquisition date. Certain disclosures are also required. The adoption of ASU No. 2015-16 did not have an impact on the Company’s consolidated financial statements. Debt Issuance Cost Presentation — The Company adopted FASB ASU No. 2015-03, “ Simplifying the Presentation of Debt Issuance Costs ” ("ASU No. 2015-03") on January 1, 2016. ASU No. 2015-03 required that certain debt issuance costs be presented on the balance sheet as a direct deduction from the carrying amount of the liability rather than as deferred assets. The Company reclassified its current and prior year debt issuance costs as required by the rule. Stock-Based Compensation Accounting — The Company early adopted FASB 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 rule was January 1, 2017, the Company elected to early adopt ASU No. 2016-09, as permitted by the amendment. ASU No. 2016-09 requires certain changes in accounting for stock-based compensation, some of which was required to be applied to the beginning of the Company's fiscal year beginning January 1, 2016. Our financial results for periods prior to 2016 were not impacted. 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 Consolidated Statement of Operations. Prior to ASU No. 2016-09, excess tax benefits or deficiencies were recorded in additional paid-in capital in Stockholders' Equity (Deficit) in the Consolidated Balance Sheet. As a result, the benefit from approximately $10.0 million in excess tax benefits from stock compensation awards was recognized in income tax expense in 2016. This benefit increased our 2016 basic and diluted income per share by $0.12 per share. In addition, 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 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 elected to apply this classification amendment prospectively, effective January 1, 2016. The adoption of ASU No. 2016-09 increased the Company's 2016 operating cash flow by $10.0 million with a corresponding decrease in financing activities. ASU No. 2016-09 also permits companies to make an entity-wide accounting policy election to recognize forfeitures of share-based compensation awards as they occur or make an estimate by applying a forfeiture rate each quarter. The Company previously estimated forfeitures but optionally elected to change its accounting policy and account for forfeitures as they occur. ASU No. 2016-09 requires this change in accounting policy to be applied using a cumulative-effect adjustment to accumulated earnings as of the beginning of the period in which the rule is adopted. Accordingly, the Company recorded a $0.3 million decrease to its opening accumulated earnings effective January 1, 2016. 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: Business Combinations — In January 2017, the FASB issued ASU No. 2017-01, "Clarifying the Definition of a Business" ("ASU No. 2017-01"), which is effective for Gartner on January 1, 2018. ASU No. 2017-01 changes the GAAP definition of a business which can impact the accounting for asset purchases, acquisitions, goodwill impairment, and other assessments. We are currently evaluating the impact of ASU No. 2017-01 on the Company's consolidated financial statements. Statement of Cash Flows — In November 2016, the FASB issued ASU No. 2016-18, "Restricted Cash" ("ASU No. 2016-18"). ASU No. 2016-18 requires that amounts generally described as restricted cash and restricted cash equivalents be presented with cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. If different, a reconciliation of the cash balances reported in the cash flow statement and the balance sheet would need to be provided along with explanatory information. ASU No. 2016-18 is effective for Gartner on January 1, 2018. We are currently evaluating the impact of ASU No. 2016-18 on the Company's consolidated financial statements. Income Taxes — In October 2016, the FASB issued ASU No. 2016-16, "Intra-Entity Transfers of Assets Other Than Inventory" ("ASU No. 2016-16"). ASU No. 2016-16 accelerates the recognition of taxes on certain intra-entity transactions and is effective for Gartner on January 1, 2018. Current GAAP requires deferral of the income tax implications of an intercompany sale of assets until the assets are sold to a third party or recovered through use. Under the new rule, the seller’s tax effects and the buyer’s deferred taxes will be immediately recognized upon the sale. We have completed an initial evaluation of the impact of ASU No. 2016-16 and we do not expect it will have a material impact on our consolidated financial statements when adopted but could impact the timing of recognition of taxes on future intra-entity transfers. Statement of Cash Flows — In August 2016, the FASB issued ASU No. 2016-15, "Classification of Certain Cash Receipts and Cash Payments" ("ASU No. 2016-15"). ASU No. 2016-15 sets forth classification requirements for certain cash flow transactions. ASU No. 2016-15 is effective for Gartner on January 1, 2018, but early adoption is permitted. We have completed an initial evaluation of the impact of ASU No. 2016-15 and we do not expect it will have a material impact on our consolidated financial statements. Financial Instrument Credit Losses — In June 2016, the FASB issued ASU No. 2016-13, " Financial Instruments—Credit Losses" ("ASU No. 2016-13"). ASU No. 2016-13 amends the current financial instrument impairment model by requiring entities to use a forward-looking approach based on expected losses to estimate credit losses on certain types of financial instruments, including trade receivables. ASU No. 2016-13 is effective for Gartner on January 1, 2020, with early adoption permitted. We are currently evaluating the potential impact of ASU No. 2016-13 on our consolidated financial statements. Leases — In February 2016, the FASB issued ASU No. 2016-02, " Leases " ("ASU No. 2016-02") which will require significant changes in the accounting and disclosure for lease arrangements. Currently under U.S. GAAP, lease arrangements that meet certain criteria are considered operating leases and are not recorded on the balance sheet. All of the Company's existing lease arrangements are accounted for as operating leases and are thus not recorded on the Company's balance sheet. ASU No. 2016-02 will significantly change the accounting for leases since a right-of-use ("ROU") model must be used in which the lessee must record a ROU asset and a lease liability on the balance sheet for leases with terms longer than 12 months. Leases will be classified as either finance or operating arrangements, with classification affecting the pattern of expense recognition in the income statement. ASU No. 2016-02 also requires expanded disclosures about leasing arrangements. ASU No. 2016-02 will be effective for Gartner on January 1, 2019. We are currently evaluating the impact of ASU No. 2016-02 on our consolidated financial statements. Financial Instruments Recognition and Measurement — In January 2016, the FASB issued ASU No. 2016-01, " Financial Instruments Overall - Recognition and Measurement of Financial Assets and Liabilities " ("ASU No. 2016-01") to address certain aspects of recognition, measurement, presentation, and disclosure of financial instruments. Among the significant changes required by ASU No. 2016-01 is that equity investments will be measured at fair value with changes in fair value recognized in net income. ASU No. 2016-01 will be effective for Gartner on January 1, 2018. We have completed an initial evaluation of the impact of ASU No. 2016-01 and we do not expect it will have a material impact on our consolidated financial statements but may require additional disclosures. Revenue — In May 2014, the FASB issued ASU No. 2014-09, " Revenue from Contracts with Customers " ("ASU No. 2014-09"). ASU No. 2014-09 and related amendments require changes in revenue recognition policies as well as enhanced disclosures. ASU No. 2014-09 is intended to clarify the principles for recognizing revenue by removing inconsistencies and weaknesses in existing revenue recognition rules; provide a more robust framework for addressing revenue recognition issues; improve comparability of revenue recognition practices across entities, industries, jurisdictions and capital markets; and provide more useful information to users of financial statements through improved disclosures. The Company has completed an initial assessment of the impact of ASU No. 2014-09 on its existing revenue recognition policies and plans to adopt the rule on January 1, 2018 using the cumulative effect method of adoption. ASU No. 2014-09 also requires significantly expanded disclosures around the nature, amount, timing and uncertainty of revenue and cash flows arising from contracts with customers, which the Company is currently compiling. While the Company has not completed its assessment of the impact of ASU No. 2014-09, based on the analysis completed to date, the Company does not currently anticipate that the new rule will have a material impact on its consolidated financial statements. The FASB also continues to work on a number of other significant accounting standards which if issued could materially impact the Company's accounting policies and disclosures in future periods. However, since these standards have not yet been issued, the effective dates and potential impact are unknown.

Business and Significant Acco25

Business and Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Property, Plant and Equipment	The Company's total fixed assets, less accumulated depreciation and amortization, consisted of the following (in thousands): Useful Life December 31, Category (Years) 2016 2015 Computer equipment and software 2-7 $ 166,385 $ 148,195 Furniture and equipment 3-8 43,137 39,072 Leasehold improvements 2-15 96,603 87,103 $ 306,125 $ 274,370 Less — accumulated depreciation and amortization (184,519 ) (165,637 ) Property, equipment, and leasehold improvements, net $ 121,606 $ 108,733
Schedule of Changes in Intangible Assets Subject to Amortization	Changes in intangible assets subject to amortization during the two-year period ended December 31, 2016 were as follows (in thousands): December 31, 2016 Trade Names 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 3,677 1,948 — — 5,927 Intangibles fully amortized — — (162 ) (125 ) — (287 ) Foreign currency translation impact (109 ) (3,168 ) (3,508 ) (69 ) (22 ) (6,876 ) Gross cost 4,337 63,369 3,728 16,025 29,308 116,767 Accumulated amortization (2), (3) (1,737 ) (16,744 ) (2,033 ) (8,904 ) (10,548 ) (39,966 ) Balance, December 31, 2016 $ 2,600 $ 46,625 $ 1,695 $ 7,121 $ 18,760 $ 76,801 December 31, 2015 Trade Names Customer Relationships Content Software Non-Compete Total Gross cost, December 31, 2014 $ 6,924 $ 27,933 $ 3,560 $ 6,569 $ 9,272 $ 54,258 Additions due to acquisitions (1) 3,260 42,620 2,000 11,656 20,075 79,611 Intangibles fully amortized (6,013 ) (7,210 ) — — — (13,223 ) Foreign currency translation impact (27 ) (483 ) (110 ) (2,006 ) (17 ) (2,643 ) 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 due to the Company's acquisitions. See Note 2 — Acquisitions for additional information. (2) Intangible assets are 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 $24.8 million , $13.3 million , and $8.2 million in 2016 , 2015 , and 2014 , respectively.
Schedule of Estimated Future Amortization Expense by Year From Amortizable Intangibles	The estimated future amortization expense by year from finite-lived intangibles is as follows (in thousands): 2017 $ 23,356 2018 20,072 2019 15,081 2020 12,897 2021 and thereafter 5,395 $ 76,801
Schedule of Changes to The Carrying Amount of Goodwill by Reporting Unit	The following table presents changes to the carrying amount of goodwill by segment during the two-year period ended December 31, 2016 (in thousands): Research Consulting Events Total Balance, December 31, 2014 (1) $ 445,460 $ 99,417 $ 41,788 $ 586,665 Additions due to acquisitions (2) 138,053 — — 138,053 Foreign currency translation adjustments (8,221 ) (1,005 ) (133 ) (9,359 ) Balance, December 31, 2015 $ 575,292 $ 98,412 $ 41,655 $ 715,359 Additions due to acquisitions (2) 28,465 — 5,843 34,308 Foreign currency translation adjustments (8,307 ) (1,932 ) (975 ) (11,214 ) Balance, December 31, 2016 $ 595,450 $ 96,480 $ 46,523 $ 738,453 (1) The Company does not have any accumulated goodwill impairment losses. (2) The additions are due to the Company's acquisitions (See Note 2—Acquisitions for additional information).

Other Assets (Tables)

Other Assets (Tables)	12 Months Ended
	Dec. 31, 2016
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Schedule of Other Assets	Other assets consist of the following (in thousands): December 31, 2016 2015 Benefit plan-related assets $ 45,958 $ 42,168 Non-current deferred tax assets 27,275 26,418 Other 14,046 38,298 Total other assets $ 87,279 $ 106,884

Accounts Payable, Accrued, an27

Accounts Payable, Accrued, and Other Liabilities (Tables)	12 Months Ended
	Dec. 31, 2016
Payables and Accruals [Abstract]
Schedule of Accounts Payable and Accrued Liabilities	Accounts payable and accrued liabilities consist of the following (in thousands): December 31, 2016 2015 Accounts payable $ 41,009 $ 31,570 Payroll and employee benefits payable 87,821 85,575 Severance and retention bonus payable 22,425 38,557 Bonus payable 105,549 90,989 Commissions payable 68,273 66,054 Taxes payable 20,378 13,714 Other accrued liabilities 95,316 61,232 Total accounts payable and accrued liabilities $ 440,771 $ 387,691
Schedule of Other Liabilities	Other liabilities consist of the following (in thousands): December 31, 2016 2015 Non-current deferred revenue $ 11,289 $ 7,603 Long-term taxes payable 19,737 13,784 Deferred rent 13,747 15,207 Benefit plan-related liabilities 67,747 62,675 Other 69,297 94,325 Total other liabilities $ 181,817 $ 193,594

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2016
Debt Disclosure [Abstract]
Schedule of Debt	The following table summarizes the Company’s total outstanding borrowings (in thousands): Amount Outstanding December 31, Amount Outstanding December 31, Description: 2016 2015 Term loan (1) $ 585,000 $ 380,000 Revolver (1), (2) 115,000 440,000 Other (3) 2,500 5,000 Subtotal (4), (5) 702,500 825,000 Less: deferred financing fees (8,109 ) (6,169 ) Net carrying amount $ 694,391 $ 818,831 (1) The contractual annual interest rate as of December 31, 2016 on both the term loan and the revolver was 2.15% , which consisted of a floating Eurodollar base rate of 0.77% plus a margin of 1.38% . However, the Company has interest rate swap contracts which effectively convert the floating eurodollar base rate to a fixed base rate on $700.0 million of borrowings (see below). (2) The Company had $1.1 billion of available borrowing capacity on the revolver (not including the expansion feature) as of December 31, 2016 . (3) Consists of a State of Connecticut economic development loan with a 3.0% fixed rate of interest that matures in 2022. During 2016, $2.5 million of the $5.0 million original balance was extinguished after the Company met certain employment targets. As a result of the loan extinguishment, the Company recorded a gain of $2.5 million , which was recorded in Other income (expense), net in the Consolidated Statements of Operations. (4) As of December 31, 2016, $30.0 million of the debt was classified as short-term and $672.5 million was classified as long- term on the Consolidated Balance Sheet. (5) The weighted-average annual interest rate on the Company's outstanding debt as of December 31, 2016 was 2.80% , which includes the impact of the Company's interest swap contracts, which are discussed below.

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Schedule of Future Minimum Lease Payments under Operating Leases	The future minimum annual cash payments under these operating lease agreements as of December 31, 2016 was as follows (in thousands): Year ended December 31, 2017 $ 49,250 2018 41,074 2019 33,640 2020 25,452 2021 22,898 Thereafter 142,930 Total minimum lease payments $ 315,244

Stockholders' Equity (Deficit)

Stockholders' Equity (Deficit) (Tables)	12 Months Ended
	Dec. 31, 2016
Equity [Abstract]
Schedule of Transactions Relating to Common Stock	The following table summarizes transactions relating to Common Stock for the three years ended December 31, 2016: Issued Shares Treasury Stock Shares Balance at December 31, 2013 156,234,415 64,268,863 Issuances under stock plans (1,452,419 ) Purchases for treasury (1) 5,897,446 Balance at December 31, 2014 156,234,415 68,713,890 Issuances under stock plans — (1,003,746 ) Purchases for treasury (1) — 6,186,101 Balance at December 31, 2015 156,234,415 73,896,245 Issuances under stock plans — (923,696 ) Purchases for treasury (1) — 610,623 Balance at December 31, 2016 156,234,415 73,583,172 (1) The Company used a total of $59.0 million , $509.0 million , and $432.0 million in cash for share repurchases in 2016, 2015, and 2014, respectively.
Schedule of Accumulated Other Comprehensive (Loss) Income, Net by Components	The following tables disclose information about changes in accumulated other comprehensive (loss) income ("AOCL/I"), a component of equity, by component and the related amounts reclassified out of AOCL/I to income during the years indicated (net of tax, in thousands) (1): 2016 Interest Rate Swaps Defined Benefit Pension Plans Foreign Currency Translation Adjustments 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 (2,902 ) (1,113 ) (5,986 ) (10,001 ) Reclassifications from AOCL/I to income during the period (2), (3) 4,572 148 — 4,720 Other comprehensive income (loss) for the period 1,670 (965 ) (5,986 ) (5,281 ) Balance - December 31, 2016 $ (1,409 ) $ (5,797 ) $ (42,477 ) $ (49,683 ) 2015 Interest Rate Swaps Defined Benefit Pension Plans Foreign Currency Translation Adjustments 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 (6,356 ) 986 (23,089 ) (28,459 ) Reclassifications from AOCL/I to income during the period (2), (3) 5,017 210 — 5,227 Other comprehensive (loss) income for the period (1,339 ) 1,196 (23,089 ) (23,232 ) Balance - December 31, 2015 $ (3,079 ) $ (4,832 ) $ (36,491 ) $ (44,402 ) (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 11 – 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 13 – Employee Benefits for information regarding the Company’s defined benefit pension plans.

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 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 for the years ended December 31 (in millions): Award type: 2016 2015 2014 Stock appreciation rights $ 5.6 $ 5.7 $ 5.0 Common stock equivalents 0.7 0.6 0.6 Restricted stock units 40.4 39.8 33.2 Total (1) $ 46.7 $ 46.1 $ 38.8
Schedule of Stock-based Compensation Expense by Expense Category	Stock-based compensation expense was recognized by line item in the Consolidated Statements of Operations for the years ended December 31 as follows (in millions): Amount recorded in: 2016 2015 2014 Costs of services and product development $ 21.9 $ 20.6 $ 17.6 Selling, general, and administrative 24.8 25.5 21.2 Total (1) $ 46.7 $ 46.1 $ 38.8
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 for the years ended December 31: 2016 2015 2014 Expected dividend yield (1) — % — % — % Expected stock price volatility (2) 22 % 24 % 25 % Risk-free interest rate (3) 1.1 % 1.5 % 1.3 % Expected life in years (4) 4.39 4.41 4.43 (1) The dividend yield assumption is based on both 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 the implied volatility from publicly traded options in 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, the 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 for the year ended December 31, 2016: Stock Appreciation Rights (SARs) (in millions) Per Share Weighted- Average Exercise Price Per Share Weighted- Average Grant Date Fair Value Weighted-Average Remaining Contractual Term (in years) Outstanding at December 31, 2015 1.3 $ 56.47 $ 14.92 4.46 years Granted 0.4 80.06 16.50 6.11 years Forfeited — — — — Exercised (0.4 ) 40.65 13.03 na Outstanding at December 31, 2016 (1), (2) 1.3 $ 66.22 $ 15.77 4.40 years Vested and exercisable at December 31, 2016 (2) 0.5 $ 55.15 $ 14.91 3.25 years na = not applicable (1) At December 31, 2016, 0.8 million of these SARs were unvested. The Company expects that substantially all of these unvested awards will vest in future periods. (2) At December 31, 2016, SARs outstanding had an intrinsic value of $46.8 million . SARs vested and exercisable had an intrinsic value of $25.1 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 year ended December 31, 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 81.41 Vested and released (0.6 ) 58.15 Forfeited (0.1 ) 69.40 Outstanding at December 31, 2016 (2), (3) 1.3 $ 73.19 (1) The 0.6 million RSUs granted in 2016 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 of performance-based RSUs was determined based on the achievement of an increase in the Company's total contract value in 2016. Total contract value represents the value attributable to all of our subscription-related contracts. (2) The Company expects that substantially all of the outstanding awards at December 31, 2016 will vest in future periods. (3) The weighted-average remaining contractual term of the outstanding RSUs is approximately 1.1 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 for the year ended December 31, 2016: Common Stock Equivalents (CSEs) Per Share Weighted-Average Grant Date Fair Value Outstanding at December 31, 2015 105,664 $ 19.57 Granted 7,069 93.90 Converted to common stock (5,395 ) 93.90 Outstanding at December 31, 2016 107,338 $ 20.74

Computation of Earnings Per S32

Computation of Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2016
Earnings Per Share [Abstract]
Schedule of Reconciliation of the Basic and Diluted Earnings Per Share Computations	The following table sets forth the reconciliation of the basic and diluted earnings per share computations for the years ended December 31 (in thousands, except per share amounts): 2016 2015 2014 Numerator: Net income used for calculating basic and diluted earnings per common share $ 193,582 $ 175,635 $ 183,766 Denominator: (1) Weighted average number of common shares used in the calculation of basic earnings per share 82,571 83,852 89,337 Common share equivalents associated with stock-based compensation plans 1,249 1,204 1,382 Shares used in the calculation of diluted earnings per share 83,820 85,056 90,719 Earnings per share: Basic $ 2.34 $ 2.09 $ 2.06 Diluted $ 2.31 $ 2.06 $ 2.03 (1) The Company repurchased 0.6 million , 6.2 million , and 5.9 million shares of its Common Stock in 2016, 2015, and 2014, respectively.
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	The following table presents the number of common share equivalents that were not included in the computation of diluted EPS in the table above because the effect would have been anti-dilutive. During periods with net income, these common share equivalents were anti-dilutive because their exercise price was greater than the average market value of a share of Common Stock during the period. 2016 2015 2014 Anti-dilutive common share equivalents as of December 31 (in millions): 0.2 0.3 0.3 Average market price per share of Common Stock during the year $ 92.58 $ 86.02 $ 73.27

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Schedule of Components of Income before Income Taxes	The following is a summary of the components of the Company's income before income taxes for the years ended December 31 (in thousands): 2016 2015 2014 U.S. $ 182,178 $ 165,848 $ 188,963 Non-U.S. 106,253 106,363 85,720 Income before income taxes $ 288,431 $ 272,211 $ 274,683
Schedule of Components of Income Tax	The expense for income taxes on the above income consists of the following components (in thousands): 2016 2015 2014 Current tax expense: U.S. federal $ 58,616 $ 48,801 $ 49,281 State and local 11,292 10,300 5,135 Foreign 27,536 23,225 16,653 Total current 97,444 82,326 71,069 Deferred tax (benefit) expense: U.S. federal (61 ) (884 ) (6,670 ) State and local (349 ) (702 ) 6,477 Foreign (1,626 ) 1,550 779 Total deferred (2,036 ) (36 ) 586 Total current and deferred 95,408 82,290 71,655 Benefit (expense) relating to interest rate swaps used to increase (decrease) equity (1,113 ) 893 (1,442 ) Benefit from stock transactions with employees used to increase equity 52 13,960 18,704 Benefit (expense) relating to defined-benefit pension adjustments used to increase (decrease) equity 502 (567 ) 2,000 Total tax expense $ 94,849 $ 96,576 $ 90,917
Schedule of Deferred Tax Assets and Liabilities	Long-term deferred tax assets and liabilities are comprised of the following (in thousands): December 31, 2016 2015 Accrued liabilities $ 62,439 $ 67,888 Loss and credit carryforwards 7,766 8,522 Assets relating to equity compensation 25,569 22,686 Other assets 6,652 6,712 Gross deferred tax assets 102,426 105,808 Property, equipment, and leasehold improvements (11,796 ) (9,904 ) Intangible assets (43,548 ) (55,275 ) Prepaid expenses (32,971 ) (28,535 ) Other liabilities (7,925 ) (7,244 ) Gross deferred tax liabilities (96,240 ) (100,958 ) Valuation allowance (1,431 ) (1,828 ) Net deferred tax assets $ 4,755 $ 3,022
Schedule of Effective Income Tax Rate Reconciliation	The differences between the U.S. federal statutory income tax rate and the Company’s effective tax rate on income before income taxes for the years ended December 31 follow: 2016 2015 2014 Statutory tax rate 35.0 % 35.0 % 35.0 % State income taxes, net of federal benefit 2.4 3.3 3.1 Effect of non-U.S. operations (5.9 ) (6.5 ) (6.3 ) Record (release) reserve for tax contingencies 3.2 1.7 1.8 Excess tax benefits from stock based compensation (3.8 ) — — Nondeductible acquisition costs 2.6 0.8 0.1 Record (release) valuation allowance (0.2 ) 0.5 — Other items, net (0.4 ) 0.7 (0.6 ) Effective tax rate 32.9 % 35.5 % 33.1 %
Schedule of Reconciliation of Beginning and Ending Unrecognized Tax Benefits	The following is a reconciliation of the beginning and ending amount of unrecognized tax benefits, excluding interest and penalties, for the years ended December 31 (in thousands): 2016 2015 Beginning balance $ 25,911 $ 20,645 Additions based on tax positions related to the current year 7,086 5,150 Additions for tax positions of prior years 6,443 7,839 Reductions for tax positions of prior years (496 ) (3,880 ) Reductions for expiration of statutes (1,006 ) (2,287 ) Settlements (544 ) (960 ) Change in foreign currency exchange rates (295 ) (596 ) Ending balance $ 37,099 $ 25,911

Derivatives and Hedging (Tables

Derivatives and Hedging (Tables)	12 Months Ended
	Dec. 31, 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 and for the years ended December 31 (in thousands, except for number of outstanding contracts): 2016 Derivative Contract Type Number of Outstanding Contracts Contract Notional Amount Fair Value Asset (Liability) (3) Balance Sheet Line Item AOCI Unrealized (Loss), Net Of Tax Interest rate swaps (1) 3 $ 700,000 $ (2,349 ) Other liabilities $ (1,409 ) Foreign currency forwards (2) 84 86,946 (320 ) Other current assets — Total 87 $ 786,946 $ (2,669 ) $ (1,409 ) 2015 Derivative Contract Type Number of Outstanding Contracts Contract Notional Amount Fair Value Asset (Liability) (3) Balance Sheet Line Item AOCI Unrealized (Loss), Net Of Tax Interest rate swap (1) 3 $ 700,000 $ (5,132 ) Other liabilities $ (3,079 ) Foreign currency forwards (2) 102 193,610 235 Other current assets — 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 the fair value of the swaps are deferred and are recorded in AOCL/I, net of tax effect (see Note 5 — 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 outstanding contracts at December 31, 2016 matured by the end of January 2017. (3) See Note 12 — 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 Consolidated Statements of Operations for derivative contracts for the years ended December 31 (in millions): Amount recorded in: 2016 2015 2014 Interest expense (1) $ 7.6 $ 8.5 $ 4.1 Other expense (income), net (2) 0.3 0.1 (0.5 ) Total expense $ 7.9 $ 8.6 $ 3.6 (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)	12 Months Ended
	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Schedule of Assets and Liabilities Measured to Fair Value 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: December 31, December 31, Assets: Values based on Level 1 inputs: Deferred compensation plan assets (1) $ 10,247 $ 8,671 Total Level 1 inputs $ 10,247 $ 8,671 Values based on Level 2 inputs: Deferred compensation plan assets (1) $ 27,847 $ 25,474 Foreign currency forward contracts (2) 165 610 Total Level 2 inputs $ 28,012 $ 26,084 Total Assets $ 38,259 $ 34,755 Liabilities: Values based on Level 2 inputs: Deferred compensation plan liabilities (1) $ 43,075 $ 39,071 Foreign currency forward contracts (2) 485 375 Interest rate swap contracts (3) 2,349 5,132 Total Level 2 inputs $ 45,909 $ 44,578 Total Liabilities $ 45,909 $ 44,578 (1) The Company has a deferred compensation plan for the benefit of certain highly compensated officers, managers and other key employees (see Note 13 — Employee Benefits). The assets consist of investments in money market and mutual funds, and company-owned life insurance contracts. The money market funds consist of cash equivalents while the mutual fund investments consist of publicly-traded and quoted equity shares. The Company considers the fair value of these assets to be based on Level 1 inputs, and these assets had a fair value of $10.2 million and $8.7 million as of December 31, 2016 and 2015, respectively. The carrying amount of the life insurance contracts equals their cash surrender value. Cash surrender value represents the estimated amount that the Company would receive upon termination of the contract, which approximates fair value. The Company considers the life insurance contracts to be valued based on a Level 2 input, and these assets had a fair value of $27.8 million and $25.5 million at December 31, 2016 and 2015, respectively. 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 (see Note 11 — Derivatives and Hedging). Valuation of the foreign currency forward contracts is based on 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 variability of interest payments on its borrowings (see Note 11 — Derivatives and Hedging). The fair value of the swaps is based on mark-to-market valuations provided 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 (Tables)

Employee Benefits (Tables)	12 Months Ended
	Dec. 31, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
Schedule of Components of Defined Benefit Pension Expense	The following are the components of defined benefit pension expense for the years ended December 31 (in thousands): 2016 2015 2014 Service cost $ 2,780 $ 2,620 $ 2,630 Interest cost 850 790 1,190 Expected return on plan assets (375 ) (345 ) (540 ) Recognition of actuarial loss 200 300 75 Recognition of termination benefits — 85 30 Total defined benefit pension plan expense (1) $ 3,455 $ 3,450 $ 3,385 (1) Pension expense is classified in SG&A in the Consolidated Statements of Operations.
Schedule of Assumptions Used in the Computation of Pension Expense	The following are the key assumptions used in the computation of pension expense for the years ended December 31: 2016 2015 2014 Weighted-average discount rate (1) 1.78 % 2.19 % 2.15 % Average compensation increase 2.67 % 2.66 % 2.65 % (1) Discount rates are typically determined by utilizing the yields on long-term corporate or government bonds in the relevant country with a duration consistent with the expected term of the underlying pension obligations.
Schedule of Changes in the Projected Benefit Obligation	The following table provides information related to changes in the projected benefit obligation for the years ended December 31 (in thousands): 2016 2015 2014 Projected benefit obligation at beginning of year $ 35,870 $ 38,115 $ 34,585 Service cost 2,780 2,620 2,630 Interest cost 850 790 1,190 Actuarial loss (gain) due to assumption changes and plan experience 1,480 (1,190 ) 6,300 Additions and contractual termination benefits — 85 30 Benefits paid (1) (1,640 ) (775 ) (1,350 ) Foreign currency impact (940 ) (3,775 ) (5,270 ) Projected benefit obligation at end of year (2) $ 38,400 $ 35,870 $ 38,115 (1) The Company projects the following benefit payments will be made in future years to plan participants: $1.4 million in 2017; $2.0 million in 2018; $1.1 million in 2019, $1.5 million in 2020, $1.5 million in 2021; and $9.5 million in total in the five years thereafter. (2) Measured as of December 31.
Schedule of Funded Status of the Plans and Related Amounts Recorded in Consolidated Balance Sheet	The following table provides information regarding the funded status of the plans and related amounts recorded in the Company’s Consolidated Balance Sheets as of December 31 (in thousands): Funded status of the plans: 2016 2015 2014 Projected benefit obligation $ 38,400 $ 35,870 $ 38,115 Pension plan assets at fair value (1) (14,465 ) (13,190 ) (13,220 ) Funded status – shortfall (2) $ 23,935 $ 22,680 $ 24,895 Amounts recorded in the Consolidated Balance Sheets for the plans: Other liabilities — accrued pension obligation (2) $ 23,935 $ 22,680 $ 24,895 Stockholders’ equity — deferred actuarial loss (3) $ (5,797 ) $ (4,832 ) $ (6,028 ) (1) The pension plan assets are held by third-party trustees and are invested in a diversified portfolio of equities, high quality government and corporate bonds, and other investments. The assets are primarily valued based on Level 1 and Level 2 inputs under the fair value hierarchy in FASB ASC Topic No. 820, with the majority of the invested assets considered to be of low-to-medium investment risk. The Company projects a future long-term rate of return on these plan assets of 2.7% , which it believes is reasonable based on the composition of the assets and both current and projected market conditions. For the year-ended December 31, 2016, the Company contributed $2.4 million to these plans, and benefits paid to participants were $1.6 million . (2) The Funded status - shortfall represents the amount of the projected benefit obligation that the Company has not funded with a third-party trustee. This amount is a liability of the Company and is recorded in Other liabilities on the Company’s Consolidated Balance Sheets. (3) The deferred actuarial loss as of December 31, 2016 is recorded in AOCL/I and will be reclassified out of AOCL/I and recognized as pension expense over approximately 13 years , subject to certain limitations set forth in FASB ASC Topic No. 715. The impact of this amortization on pension expense in 2017 is projected to result in approximately $0.3 million of additional expense. The amortization of deferred actuarial losses from AOCL/I to pension expense in each of the three years ended December 31, 2016 was immaterial.

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2016
Segment Reporting [Abstract]
Schedule of Segment Reporting Information by Segment	The following tables present operating results for the Company’s reportable segments for the years ended December 31 (in thousands): Research Consulting Events Consolidated 2016 Revenues $ 1,829,721 $ 346,214 $ 268,605 $ 2,444,540 Gross contribution 1,267,760 107,585 136,655 1,512,000 Corporate and other expenses (1,206,859 ) Operating income $ 305,141 Research Consulting Events Consolidated 2015 Revenues $ 1,583,486 $ 327,735 $ 251,835 $ 2,163,056 Gross contribution 1,096,827 107,193 130,527 1,334,547 Corporate and other expenses (1,046,550 ) Operating income $ 287,997 Research Consulting Events Consolidated 2014 Revenues $ 1,445,338 $ 348,396 $ 227,707 $ 2,021,441 Gross contribution 1,001,914 119,931 112,384 1,234,229 Corporate and other expenses (948,067 ) Operating income $ 286,162
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): Twelve months ended December 31, 2016 2015 2014 Total segment gross contribution $ 1,512,000 $ 1,334,547 $ 1,234,229 Costs and expenses: Cost of services and product development - unallocated (1) 13,108 10,567 10,721 Selling, general and administrative 1,089,184 962,677 876,067 Depreciation and amortization 61,969 47,131 39,412 Acquisition and integration charges 42,598 26,175 21,867 Operating income 305,141 287,997 286,162 Interest expense and other 16,710 15,786 11,479 Provision for income taxes 94,849 96,576 90,917 Net income $ 193,582 $ 175,635 $ 183,766 (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.
Schedule of Revenue from External Customers and Long-Lived Assets by Geographical Areas	Summarized information by geographic location as of and for the years ended December 31 follows (in thousands): 2016 2015 2014 Revenues: United States and Canada $ 1,519,748 $ 1,347,676 $ 1,204,476 Europe, Middle East and Africa 616,721 557,165 570,334 Other International 308,071 258,215 246,631 Total revenues $ 2,444,540 $ 2,163,056 $ 2,021,441 Long-lived assets: (1) United States and Canada $ 143,921 $ 163,933 $ 142,963 Europe, Middle East and Africa 42,326 31,130 34,093 Other International 24,630 16,050 13,282 Total long-lived assets $ 210,877 $ 211,113 $ 190,338 (1) Excludes goodwill and other intangible assets.

Valuation and Qualifying Acco38

Valuation and Qualifying Accounts (Tables)	12 Months Ended
	Dec. 31, 2016
Valuation and Qualifying Accounts [Abstract]
Summary of Valuation Allowance	The following table summarizes activity in the Company’s allowance for the years ended December 31 (in thousands): Balance at Beginning of Year Additions Charged to Expense Additions Charged Against Revenues Deductions from Reserve Balance at End of Year 2016: Allowance for doubtful accounts and returns and allowances $ 6,900 $ 4,750 $ 4,850 $ (9,100 ) $ 7,400 2015: Allowance for doubtful accounts and returns and allowances $ 6,700 $ 3,480 $ 5,420 $ (8,700 ) $ 6,900 2014: Allowance for doubtful accounts and returns and allowances $ 7,000 $ 2,950 $ 3,240 $ (6,490 ) $ 6,700

Business and Significant Acco39

Business and Significant Accounting Policies (Detail)	3 Months Ended	12 Months Ended
	Sep. 30, 2016USD ($)	Dec. 31, 2016USD ($)segment	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)
Business and Significant Accounting Policies [Line Items]
Number of reportable segments | segment		3
Acquisition and integration charges		$ 42,598,000	$ 26,175,000	$ 21,867,000
Unbilled fees receivable		45,700,000	43,200,000
Stock-based compensation expense		46,661,000	46,149,000	38,845,000
Rent expense		38,000,000	33,800,000	31,500,000
Depreciation expense		37,172,000	33,789,000	31,186,000
Net capitalized development costs for internal use software		16,600,000	14,100,000
Amortization of capitalized internal software development costs		8,800,000	8,200,000	8,200,000
Amortization of intangibles		24,797,000	13,342,000	8,226,000
Pension expense		3,500,000	3,500,000	3,400,000
Foreign currency transaction gain (loss)		(400,000)	(2,600,000)	(1,700,000)
Derivative instruments, gain (loss) recognized in income, net		7,900,000	8,600,000	3,600,000
Payments for purchases of treasury stock		58,961,000	509,049,000	432,006,000
Goodwill, impairment loss	$ 0
Impairment of long-lived assets		0	0	0
Foreign currency exchange contracts
Business and Significant Accounting Policies [Line Items]
Derivative instruments, gain (loss) recognized in income, net		$ (300,000)	(100,000)	$ 600,000
Software
Business and Significant Accounting Policies [Line Items]
Remaining amortization period		3 years
Minimum | Trade Names
Business and Significant Accounting Policies [Line Items]
Remaining amortization period		2 years
Minimum | Customer Relationships
Business and Significant Accounting Policies [Line Items]
Remaining amortization period		4 years
Minimum | Content
Business and Significant Accounting Policies [Line Items]
Remaining amortization period		1 year 6 months
Minimum | Non-Compete
Business and Significant Accounting Policies [Line Items]
Remaining amortization period		3 years
Maximum | Trade Names
Business and Significant Accounting Policies [Line Items]
Remaining amortization period		4 years
Maximum | Customer Relationships
Business and Significant Accounting Policies [Line Items]
Remaining amortization period		7 years
Maximum | Content
Business and Significant Accounting Policies [Line Items]
Remaining amortization period		4 years
Maximum | Non-Compete
Business and Significant Accounting Policies [Line Items]
Remaining amortization period		5 years
Software Advice, Inc., Market-Visio Oy, and SircleIT Inc.
Business and Significant Accounting Policies [Line Items]
Decrease in contingent liability		$ 22,700,000	$ 9,200,000

Business and Significant Acco40

Business and Significant Accounting Policies (Detail) - Property, Equipment and Leasehold Improvements, Less Accumulated Depreciation and Amortization - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Rent expense	$ 38,000	$ 33,800	$ 31,500
Property, equipment and leasehold improvements, gross	306,125	274,370
Less — accumulated depreciation and amortization	(184,519)	(165,637)
Property, equipment and leasehold improvements, net	121,606	108,733
Software
Property, Plant and Equipment [Line Items]
Property, equipment and leasehold improvements, gross	$ 166,385	148,195
Software | Minimum
Property, Plant and Equipment [Line Items]
Useful Life	2 years
Software | Maximum
Property, Plant and Equipment [Line Items]
Useful Life	7 years
Furniture and equipment
Property, Plant and Equipment [Line Items]
Property, equipment and leasehold improvements, gross	$ 43,137	39,072
Furniture and equipment | Minimum
Property, Plant and Equipment [Line Items]
Useful Life	3 years
Furniture and equipment | Maximum
Property, Plant and Equipment [Line Items]
Useful Life	8 years
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, equipment and leasehold improvements, gross	$ 96,603	$ 87,103
Leasehold improvements | Minimum
Property, Plant and Equipment [Line Items]
Useful Life	2 years
Leasehold improvements | Maximum
Property, Plant and Equipment [Line Items]
Useful Life	15 years

Business and Significant Acco41

Business and Significant Accounting Policies (Detail) - Intangible Assets Subject to Amortization - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Finite-lived Intangible Assets [Roll Forward]
Gross cost	$ 118,003	$ 54,258
Additions due to acquisitions	5,927	79,611
Finite-Lived Intangible Assets, Fully Amortized Intangibles	(287)	(13,223)
Foreign currency translation impact	(6,876)	(2,643)
Gross cost	116,767	118,003
Accumulated amortization	(39,966)	(21,459)
Finite-lived intangible assets, net	76,801	96,544
Trade Names
Finite-lived Intangible Assets [Roll Forward]
Gross cost	4,144	6,924
Additions due to acquisitions	302	3,260
Finite-Lived Intangible Assets, Fully Amortized Intangibles	0	(6,013)
Foreign currency translation impact	(109)	(27)
Gross cost	4,337	4,144
Accumulated amortization	(1,737)	(681)
Finite-lived intangible assets, net	2,600	3,463
Customer Relationships
Finite-lived Intangible Assets [Roll Forward]
Gross cost	62,860	27,933
Additions due to acquisitions	3,677	42,620
Finite-Lived Intangible Assets, Fully Amortized Intangibles	0	(7,210)
Foreign currency translation impact	(3,168)	(483)
Gross cost	63,369	62,860
Accumulated amortization	(16,744)	(9,028)
Finite-lived intangible assets, net	46,625	53,832
Content
Finite-lived Intangible Assets [Roll Forward]
Gross cost	5,450	3,560
Additions due to acquisitions	1,948	2,000
Finite-Lived Intangible Assets, Fully Amortized Intangibles	(162)	0
Foreign currency translation impact	(3,508)	(110)
Gross cost	3,728	5,450
Accumulated amortization	(2,033)	(3,525)
Finite-lived intangible assets, net	1,695	1,925
Software
Finite-lived Intangible Assets [Roll Forward]
Gross cost	16,219	6,569
Additions due to acquisitions	0	11,656
Finite-Lived Intangible Assets, Fully Amortized Intangibles	(125)	0
Foreign currency translation impact	(69)	(2,006)
Gross cost	16,025	16,219
Accumulated amortization	(8,904)	(3,699)
Finite-lived intangible assets, net	7,121	12,520
Non-Compete
Finite-lived Intangible Assets [Roll Forward]
Gross cost	29,330	9,272
Additions due to acquisitions	0	20,075
Finite-Lived Intangible Assets, Fully Amortized Intangibles	0	0
Foreign currency translation impact	(22)	(17)
Gross cost	29,308	29,330
Accumulated amortization	(10,548)	(4,526)
Finite-lived intangible assets, net	$ 18,760	$ 24,804

Business and Significant Acco42

Business and Significant Accounting Policies (Detail) - Estimated Future Amortization Expense by Year from Purchased Intangibles - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2,017	$ 23,356
2,018	20,072
2,019	15,081
2,020	12,897
2,021	5,395
Finite-lived intangible assets, net	$ 76,801	$ 96,544

Business and Significant Acco43

Business and Significant Accounting Policies (Detail) - Changes to the Carrying Amount of Goodwill by Reporting Unit - USD ($)	3 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015
Goodwill [Line Items]
Goodwill, impairment loss	$ 0
Goodwill [Roll Forward]
Beginning Balance		$ 715,359,000	$ 586,665,000
Additions due to acquisition		34,308,000	138,053,000
Foreign currency translation adjustments		(11,214,000)	(9,359,000)
Ending Balance		738,453,000	715,359,000
Research
Goodwill [Roll Forward]
Beginning Balance		575,292,000	445,460,000
Additions due to acquisition		28,465,000	138,053,000
Foreign currency translation adjustments		(8,307,000)	(8,221,000)
Ending Balance		595,450,000	575,292,000
Consulting
Goodwill [Roll Forward]
Beginning Balance		98,412,000	99,417,000
Additions due to acquisition		0	0
Foreign currency translation adjustments		(1,932,000)	(1,005,000)
Ending Balance		96,480,000	98,412,000
Events
Goodwill [Roll Forward]
Beginning Balance		41,655,000	41,788,000
Additions due to acquisition		5,843,000	0
Foreign currency translation adjustments		(975,000)	(133,000)
Ending Balance		$ 46,523,000	$ 41,655,000

Business and Significant Acco44

Business and Significant Accounting Policies Business and Significant Accounting Policies (Detail) - New Accounting Pronouncements - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Effective income tax rate reconciliation share-based compensation excess tax benefit amount	$ 10,000
Provision for income taxes	94,849	$ 96,576	$ 90,917
Net income	$ 193,582	$ 175,635	$ 183,766
Basic earnings per share, basic (in Dollars per share)	$ 2.34	$ 2.09	$ 2.06
Diluted earnings per share (in Dollars per share)	$ 2.31	$ 2.06	$ 2.03
Operating cash flow	$ 365,632	$ 345,561	$ 346,779
Cash used by financing activities	(174,686)	(67,690)	(208,670)
Accumulated earnings	$ 1,644,005	1,450,684
Cumulative effect of adoption of ASU No. 2016-09		261
New Accounting Pronouncement, Early Adoption, Effect | Accounting Standards Update 2016-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Basic earnings per share, basic (in Dollars per share)	$ 0.12
Diluted earnings per share (in Dollars per share)	$ 0.12
New Accounting Pronouncement, Early Adoption, Effect | Accounting Standards Update 2016-09, Statutory Tax Withholding Component
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating cash flow	$ 10,000
Cash used by financing activities	(10,000)
Accumulated Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net income	$ 193,582	175,635	$ 183,766
Cumulative effect of adoption of ASU No. 2016-09		261
Accumulated Earnings | New Accounting Pronouncement, Early Adoption, Effect | Accounting Standards Update 2016-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of adoption of ASU No. 2016-09		$ 300

Acquisitions - (Details)

Acquisitions - (Details)	Nov. 09, 2016USD ($)employee	Jun. 28, 2016USD ($)employee	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)company
Business Acquisition [Line Items]
Number of Businesses Acquired | company						3
Goodwill				$ 738,453,000	$ 715,359,000	$ 586,665,000
Net cash paid for acquisition				34,186,000	$ 196,229,000	$ 124,291,000
Market-Visio Oy
Business Acquisition [Line Items]
Percentage of voting interests acquired					100.00%
SircleIT Inc.
Business Acquisition [Line Items]
Percentage of voting interests acquired					100.00%
Machina Research
Business Acquisition [Line Items]
Percentage of voting interests acquired	100.00%
Entity number of employees | employee	16
Aggregate purchase price	$ 4,500,000
SCM World
Business Acquisition [Line Items]
Percentage of voting interests acquired		100.00%
Entity number of employees | employee		60
Aggregate purchase price		$ 34,200,000
Goodwill		32,400,000
Net cash paid for acquisition		27,900,000
Business combination, amortizable intangible assets recognized		5,900,000
Nubera and Capterra
Business Acquisition [Line Items]
Percentage of voting interests acquired					100.00%
Aggregate purchase price					$ 206,900,000
Business combinations, payables and accrueds recognized					25,600,000
Goodwill					138,100,000
Business combination, liabilities assumed					10,800,000
Net cash paid for acquisition					196,200,000
Contingent consideration arrangements, maximum value (up to)					$ 32,000,000
Contingent consideration arrangements, maximum value, period of expense recognition					3 years
Business combination, amortizable intangible assets recognized					$ 79,600,000
Capterra
Business Acquisition [Line Items]
Goodwill, purchase accounting adjustments				1,900,000
Software Advice
Business Acquisition [Line Items]
Percentage of voting interests acquired						100.00%
Software Advice, Inc., Market-Visio Oy, and SircleIT Inc.
Business Acquisition [Line Items]
Aggregate purchase price						$ 115,400,000
Net cash paid for acquisition						109,900,000
Acquisition cash place in escrow						$ 14,400,000
Contingent consideration arrangements, maximum value, period of expense recognition						2 years
Change in contingent consideration				(22,700,000)	(9,200,000)
Other payments to acquire businesses, restricted cash				13,600,000	$ 800,000
Business combination, goodwill and amortizable intangible assets recognized						$ 110,300,000
Business combinations, other assets recognized						5,100,000
Contingent consideration, earn-out | SCM World
Business Acquisition [Line Items]
Change in contingent consideration				$ 6,500,000
Contingent consideration, employee conditions | SCM World
Business Acquisition [Line Items]
Contingent consideration arrangements, maximum value (up to)		$ 5,400,000
Contingent consideration arrangements, maximum value, period of expense recognition		2 years
Acquisition and Integration Charges | Software Advice, Inc., Market-Visio Oy, and SircleIT Inc.
Business Acquisition [Line Items]
Contingent consideration arrangements, maximum value (up to)						$ 31,900,000
Scenario, Forecast | Capterra
Business Acquisition [Line Items]
Other payments to acquire businesses, restricted cash			$ 25,600,000

Other Assets (Detail) - Composi

Other Assets (Detail) - Composition of Other Assets - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Benefit plan-related assets	$ 45,958	$ 42,168
Non-current deferred tax assets	27,275	26,418
Other	14,046	38,298
Total other assets	$ 87,279	$ 106,884

Accounts Payable, Accrued, an47

Accounts Payable, Accrued, and Other Liabilities (Detail) - Accounts Payable and Accrued Liabilities - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Payables and Accruals [Abstract]
Accounts payable	$ 41,009	$ 31,570
Payroll and employee benefits payable	87,821	85,575
Severance and retention bonus payable	22,425	38,557
Bonus payable	105,549	90,989
Commissions payable	68,273	66,054
Taxes payable	20,378	13,714
Other accrued liabilities	95,316	61,232
Total accounts payable and accrued liabilities	$ 440,771	$ 387,691

Accounts Payable, Accrued, an48

Accounts Payable, Accrued, and Other Liabilities (Detail) - Other Liabilities - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Payables and Accruals [Abstract]
Non-current deferred revenue	$ 11,289	$ 7,603
Long-term taxes payable	19,737	13,784
Deferred rent	13,747	15,207
Benefit plan-related liabilities	67,747	62,675
Other	69,297	94,325
Total other liabilities	$ 181,817	$ 193,594

Debt (Detail)

Debt (Detail)	Jan. 20, 2017USD ($)	Dec. 31, 2016USD ($)installmentcontractoutstanding_contract	Dec. 31, 2012USD ($)	Dec. 31, 2015USD ($)outstanding_contract
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity		$ 1,800,000,000
Debt instrument, interest, additional interest above eurodollar rate		1.00%
Contract notional amount		$ 786,946,000		$ 893,610,000
Current portion of long-term debt		30,000,000		$ 35,000,000
Long-term debt, net of deferred financing fees		$ 672,500,000
Debt instrument, interest rate at period end		2.80%
Number of Outstanding Contracts | outstanding_contract		87		105
Federal Funds rate
Debt Instrument [Line Items]
Debt instrument, interest, additional interest above federal fund rate		0.50%
Euro Dollar rate | Federal Funds rate
Debt Instrument [Line Items]
Minimum applicable margin rate		0.125%
Maximum applicable margin rate		0.50%
Interest Rate Contract
Debt Instrument [Line Items]
Contract notional amount		$ 700,000,000
Interest rate swap
Debt Instrument [Line Items]
Contract notional amount		$ 700,000,000
Number of Outstanding Contracts | contract		3
Derivative, term of contract		30 days
Interest rate derivative hedge, negative fair value		$ 2,300,000		$ 5,100,000
Euro Dollar rate
Debt Instrument [Line Items]
Minimum applicable margin rate		1.125%
Maximum applicable margin rate		3.00%
Minimum | Interest rate swap
Debt Instrument [Line Items]
Derivative, fixed interest rate		1.53%
Maximum | Interest rate swap
Debt Instrument [Line Items]
Derivative, fixed interest rate		1.60%
Term loan
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity		$ 600,000,000
Debt instrument term		5 years
Interest rate at period end		2.15%
Debt instrument, interest base rate		0.77%
Debt instrument, interest, additional interest above base rate		1.38%
Connecticut Economic Development Program
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity			$ 5,000,000
Debt instrument, fixed interest rate			3.00%
Line of credit facility, decrease, forgiveness			$ 2,500,000
Debt instrument, debt forgiveness		$ 2,500,000
Letter of credit
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity		50,000,000
Letters of credit outstanding		8,500,000
Revolving Credit Facility
Debt Instrument [Line Items]
Line of credit facility, current borrowing capacity		$ 1,200,000,000
Line of credit facility, frequency of payments in quarterly installments | installment		16
Interest rate at period end		2.15%
Line of credit facility, remaining borrowing capacity		$ 1,100,000,000
Subsequent Event
Debt Instrument [Line Items]
Line of credit, capacity available for specific purpose	$ 2,275,000,000
Subsequent Event | Secured Debt
Debt Instrument [Line Items]
Debt instrument term	7 years
Line of credit, capacity available for specific purpose	$ 1,375,000,000
Subsequent Event | Unsecured Debt
Debt Instrument [Line Items]
Line of credit, capacity available for specific purpose	$ 600,000,000
Bridge Loan | Subsequent Event
Debt Instrument [Line Items]
Debt instrument term	11 months 29 days
Line of credit, capacity available for specific purpose	$ 300,000,000

Debt (Detail) - Borrowings

Debt (Detail) - Borrowings - USD ($)	Dec. 31, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Long-term debt, gross	$ 702,500,000	$ 825,000,000
Less: deferred financing fees	(8,109,000)	(6,169,000)
Long-term debt	694,391,000	818,831,000
Revolving Credit Facility
Debt Instrument [Line Items]
Long-term debt, gross	115,000,000	440,000,000
Term loan
Debt Instrument [Line Items]
Long-term debt, gross	585,000,000	380,000,000
Connecticut Economic Development Program
Debt Instrument [Line Items]
Long-term debt, gross	$ 2,500,000	$ 5,000,000

Commitments and Contingencies51

Commitments and Contingencies (Detail) - Future Minimum Annual Cash Payments Under Non-Cancelable Operating Lease Agreements $ in Thousands	Dec. 31, 2016USD ($)
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2,017	$ 49,250
2,018	41,074
2,019	33,640
2,020	25,452
2,021	22,898
Thereafter	142,930
Total minimum lease payments	$ 315,244

Stockholders' Equity (Deficit52

Stockholders' Equity (Deficit) (Detail)	12 Months Ended
	Dec. 31, 2016USD ($)vote$ / shares	Dec. 31, 2015USD ($)$ / shares	Dec. 31, 2014USD ($)
Equity [Abstract]
Common stock par value (in Dollars per share) | $ / shares	$ 0.0005	$ 0.0005
Common stock, number of votes per share | vote	1
Payments for purchases of treasury stock	$ 58,961,000	$ 509,049,000	$ 432,006,000
Stock repurchase program, authorized amount	1,200,000,000
Stock repurchase program, remaining authorized amount	$ 1,100,000,000
New Accounting Pronouncement, Early Adoption [Line Items]
Cumulative effect of adoption of ASU No. 2016-09		(261,000)
Accumulated Earnings
New Accounting Pronouncement, Early Adoption [Line Items]
Cumulative effect of adoption of ASU No. 2016-09		(261,000)
New Accounting Pronouncement, Early Adoption, Effect | Accounting Standards Update 2016-09 | Accumulated Earnings
New Accounting Pronouncement, Early Adoption [Line Items]
Cumulative effect of adoption of ASU No. 2016-09		$ (300,000)

Stockholders' Equity (Deficit53

Stockholders' Equity (Deficit) (Detail) - Summary of Transactions Relating to Common Stock - shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Common Stock
Common Stock Outstanding Roll Forward [Roll Forward]
Beginning Balance	156,234,415	156,234,415	156,234,415
Issuances under stock plans	0	0
Purchases for treasury	0	0
Ending Balance	156,234,415	156,234,415	156,234,415
Treasury Stock
Common Stock Outstanding Roll Forward [Roll Forward]
Beginning Balance	73,896,245	68,713,890	64,268,863
Issuances under stock plans	923,696	1,003,746	1,452,419
Purchases for treasury	610,623	6,186,101	5,897,446
Ending Balance	73,583,172	73,896,245	68,713,890

Stockholders' Equity (Deficit54

Stockholders' Equity (Deficit) (Details) - Changes in AOCL/I by Component - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accumulated Other Comprehensive (Loss) Income, Net of Tax [Roll Forward]
Beginning Balance	$ (132,400)	$ 161,171	$ 361,316
Changes during the period:
Other comprehensive (loss) income, net of tax	(5,281)	(23,232)	(29,515)
Ending Balance	60,878	(132,400)	161,171
Interest Rate Swaps
Accumulated Other Comprehensive (Loss) Income, Net of Tax [Roll Forward]
Beginning Balance	(3,079)	(1,740)
Changes during the period:
Change in AOCL/I before reclassifications to income	(2,902)	(6,356)
Reclassifications from AOCL/I to income during the period	4,572	5,017
Other comprehensive (loss) income, net of tax	1,670	(1,339)
Ending Balance	(1,409)	(3,079)	(1,740)
Defined Benefit Pension Plans
Accumulated Other Comprehensive (Loss) Income, Net of Tax [Roll Forward]
Beginning Balance	(4,832)	(6,028)
Changes during the period:
Change in AOCL/I before reclassifications to income	(1,113)	986
Reclassifications from AOCL/I to income during the period	148	210
Other comprehensive (loss) income, net of tax	(965)	1,196
Ending Balance	(5,797)	(4,832)	(6,028)
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive (Loss) Income, Net of Tax [Roll Forward]
Beginning Balance	(36,491)	(13,402)
Changes during the period:
Change in AOCL/I before reclassifications to income	(5,986)	(23,089)
Reclassifications from AOCL/I to income during the period	0	0
Other comprehensive (loss) income, net of tax	(5,986)	(23,089)
Ending Balance	(42,477)	(36,491)	(13,402)
AOCI Attributable to Parent
Accumulated Other Comprehensive (Loss) Income, Net of Tax [Roll Forward]
Beginning Balance	(44,402)	(21,170)	8,345
Changes during the period:
Change in AOCL/I before reclassifications to income	(10,001)	(28,459)
Reclassifications from AOCL/I to income during the period	4,720	5,227
Other comprehensive (loss) income, net of tax	(5,281)	(23,232)
Ending Balance	$ (49,683)	$ (44,402)	$ (21,170)

Stock-Based Compensation (Detai

Stock-Based Compensation (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for grant	6,200,000
Common stock par value (in Dollars per share)	$ 0.0005	$ 0.0005
Stock-based compensation expense	$ 46,661,000	$ 46,149,000	$ 38,845,000
Total share-based compensation cost not yet recognized	$ 49,400,000
Remaining weighted average service period	2 years 3 months 18 days
Weighted average remaining contractual term	1 year 1 month 6 days
Diluted earnings per share (in Dollars per share)	$ 2.31	$ 2.06	$ 2.03
Operating cash flow	$ 365,632,000	$ 345,561,000	$ 346,779,000
Cash used by financing activities	$ (174,686,000)	(67,690,000)	(208,670,000)
Executive Officer | Service-based Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants during period (in shares)	300,000
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee stock purchase plan, stock purchases as a percentage of employee compensation, maximum	10.00%
Maximum share value authorized for purchase under employee stock purchase plan	$ 23,750
Exercisable price percentage of closing price of another class of stock	95.00%
Maximum number of shares that may be purchased by eligible participants	900,000
Proceeds from stock grants	$ 9,300,000	$ 7,500,000	7,800,000
Stock Appreciation Rights (SARs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining weighted average service period	6 years 1 month 10 days
Award vesting period	4 years
Award expiry period from date of grant	7 years
Total compensation cost not yet recognized, period for recognition	4 years
Equity instruments number of shares unvested (in shares)	1,300,000	1,300,000
Aggregate intrinsic value of outstanding shares	$ 46,800,000
Aggregate intrinsic value of shares vested and exercisable	$ 25,100,000
Grants during period (in shares)	400,000
Stock Appreciation Rights (SARs) | Non Executive
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants during period (in shares)	300,000
Stock Appreciation Rights (SARs) | Unvested
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity instruments number of shares unvested (in shares)	800,000
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity instruments number of shares unvested (in shares)	1,300,000	1,400,000
Grants during period (in shares)	600,000
Restricted Stock Units (RSUs) | Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	4 years
Grants during period (in shares)	600,000
Restricted Stock Units (RSUs) | Service-based Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	4 years
Common Stock Equivalents (CSEs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity instruments number of shares unvested (in shares)	107,338	105,664
Grants during period (in shares)	7,069
Base fee percentage	50.00%
Retirement Eligible Employees Equity Award
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 19,400,000	$ 20,100,000	$ 14,800,000
Accounting Standards Update 2016-09 | New Accounting Pronouncement, Early Adoption, Effect
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Diluted earnings per share (in Dollars per share)	$ 0.12
Accounting Standards Update 2016-09, Statutory Tax Withholding Component | New Accounting Pronouncement, Early Adoption, Effect
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Operating cash flow	$ 10,000,000
Cash used by financing activities	$ (10,000,000)

Stock-Based Compensation (Det56

Stock-Based Compensation (Detail) - Stock-Based Compensation Expense By Award Type - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 46.7	$ 46.1	$ 38.8
Stock appreciation rights
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	5.6	5.7	5
Common stock equivalents
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	0.7	0.6	0.6
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 40.4	$ 39.8	$ 33.2

Stock-Based Compensation (Det57

Stock-Based Compensation (Detail) - Stock-Based Compensation Expense Recognized In Consolidated Statements Of Operations - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 46.7	$ 46.1	$ 38.8
Costs of services and product development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	21.9	20.6	17.6
Selling, general, and administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 24.8	$ 25.5	$ 21.2

Stock-Based Compensation (Det58

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)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected dividend yield	0.00%	0.00%	0.00%
Expected stock price volatility	22.00%	24.00%	25.00%
Risk-free interest rate	1.10%	1.50%	1.30%
Expected life in years	4 years 4 months 21 days	4 years 4 months 28 days	4 years 5 months 5 days

Stock-Based Compensation (Det59

Stock-Based Compensation (Detail) - Summary Of Changes In SARs Outstanding - $ / shares shares in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Weighted-Average Remaining Contractual Term (in years)
Granted	2 years 3 months 18 days
Stock Appreciation Rights (SARs)
SARs
Outstanding at December 31, 2015 (in shares)	1.3
Granted (in shares)	0.4
Forfeited (in shares)	0
Exercised (in shares)	(0.4)
Outstanding at December 31, 2016 (in shares)	1.3	1.3
Vested and exercisable at December 31, 2016 (in shares)	0.5
Per Share Weighted- Average Exercise Price
Outstanding at December 31, 2015 (in Dollars per share)	$ 56.47
Granted (in Dollars per share)	80.06
Exercised (in Dollars per share)	40.65
Outstanding at December 31, 2016 (in Dollars per share)	66.22	$ 56.47
Vested and exercisable at December 31, 2016 (in Dollars per share)	55.15
Per Share Weighted- Average Grant Date Fair Value
Outstanding at December 31, 2015 (in Dollars per share)	14.92
Granted (in Dollars per share)	16.50
Exercised (in Dollars per share)	13.03
Outstanding at December 31, 2016 (in Dollars per share)	15.77	$ 14.92
Vested and exercisable at December 31, 2016 (in Dollars per share)	$ 14.91
Weighted-Average Remaining Contractual Term (in years)
Outstanding at December 31, 2015	4 years 4 months 24 days	4 years 5 months 16 days
Granted	6 years 1 month 10 days
Outstanding at December 31, 2016	4 years 4 months 24 days	4 years 5 months 16 days
Vested and exercisable at December 31, 2016	3 years 3 months
Unvested | Stock Appreciation Rights (SARs)
SARs
Outstanding at December 31, 2016 (in shares)	0.8

Stock-Based Compensation (Det60

Stock-Based Compensation (Detail) - Summary Of Changes In RSUs Outstanding - Restricted Stock Units (RSUs) shares in Millions	12 Months Ended
	Dec. 31, 2016$ / sharesshares
Restricted Stock Units (RSUs)
Outstanding at December 31, 2015 (in shares) | shares	1.4
Granted (in shares) | shares	0.6
Vested and released (in shares) | shares	(0.6)
Forfeited (in shares) | shares	(0.1)
Outstanding at December 31, 2016 (in shares) | shares	1.3
Per Share Weighted Average Grant Date Fair Value
Outstanding at December 31, 2015 (in Dollars per share) | $ / shares	$ 62.80
Granted (in Dollars per share) | $ / shares	81.41
Vested and released (in Dollars per share) | $ / shares	58.15
Forfeited (in Dollars per share) | $ / shares	69.40
Outstanding at December 31, 2016 (in Dollars per share) | $ / shares	$ 73.19

Stock-Based Compensation (Det61

Stock-Based Compensation (Detail) - Summary Of Changes In CSEs Outstanding - Common Stock Equivalents (CSEs)	12 Months Ended
	Dec. 31, 2016$ / sharesshares
Common Stock Equivalents (CSEs)
Outstanding at December 31, 2015 (in shares) | shares	105,664
Granted (in shares) | shares	7,069
Converted to common shares (in shares) | shares	(5,395)
Outstanding at December 31, 2016 (in shares) | shares	107,338
Per Share Weighted- Average Grant Date Fair Value
Outstanding at December 31, 2015 (in Dollars per share) | $ / shares	$ 19.57
Granted (in Dollars per share) | $ / shares	93.90
Converted to common stock (in Dollars per share) | $ / shares	93.90
Outstanding at December 31, 2016 (in Dollars per share) | $ / shares	$ 20.74

Computation of Earnings Per S62

Computation of Earnings Per Share (Detail) - shares shares in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Common Stock Equivalents (CSEs)
Class of Stock [Line Items]
Stock repurchased during period (in shares)	0.6	6.2	5.9

Computation of Earnings Per S63

Computation of Earnings Per Share (Detail) - Calculations Of Basic And Diluted Earnings Per Share - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Numerator:
Net income used for calculating basic and diluted earnings per common share	$ 193,582	$ 175,635	$ 183,766
Denominator:
Weighted average number of common shares used in the calculation of basic earnings per share	82,571	83,852	89,337
Common share equivalents associated with stock-based compensation plans	1,249	1,204	1,382
Shares used in the calculation of diluted earnings per share	83,820	85,056	90,719
Earnings per share:
Basic (in Dollars per share)	$ 2.34	$ 2.09	$ 2.06
Diluted (in Dollars per share)	$ 2.31	$ 2.06	$ 2.03

Computation of Earnings Per S64

Computation of Earnings Per Share (Detail) - Common Share Equivalents Not Included in the Computation of Diluted EPS - $ / shares shares in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share [Abstract]
Antidilutive common share equivalents as of December 31	0.2	0.3	0.3
Average market price per share of common stock during the year	$ 92.58	$ 86.02	$ 73.27

Income Taxes (Detail)

Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax [Line Items]
Non-current deferred tax assets	$ 27,275	$ 26,418
Valuation allowance	1,431	1,828
Effective income tax rate reconciliation share-based compensation excess tax benefit amount	10,000
Unrecognized tax benefits	37,099	25,911	$ 20,645
Unrecognized tax benefits reductions resulting from settlements with taxing authorities and lapse of applicable statute of limitations	1,700
Unrecognized tax benefits that would impact effective tax rate	33,400
Unrecognized tax benefits that would result adjustments to other tax accounts	3,700
Income tax penalties and interest expense	4,300	3,700
Income tax examination, penalties and interest expense	900	900
Earnings of certain non US subsidiaries indefinitely reinvested	340,000
Undistributed foreign earnings	69,000
Stamford
Income Tax [Line Items]
Effective income tax rate reconciliation, state and local income taxes, amount	(300)	1,600
State and local jurisdiction
Income Tax [Line Items]
Operating loss carryforwards	2,400
Tax credit carryforwards	$ 1,900
State and local jurisdiction | Minimum
Income Tax [Line Items]
Tax credit carryforwards, expiration period	5 years
State and local jurisdiction | Maximum
Income Tax [Line Items]
Tax credit carryforwards, expiration period	6 years
Non US
Income Tax [Line Items]
Operating loss carryforwards	$ 19,500
Foreign tax credit carryforwards	600
Expire within one to five years | State and local jurisdiction
Income Tax [Line Items]
Operating loss carryforwards	$ 100
Expire within one to five years | State and local jurisdiction | Minimum
Income Tax [Line Items]
Operating loss carryforwards expiration period	1 year
Expire within one to five years | State and local jurisdiction | Maximum
Income Tax [Line Items]
Operating loss carryforwards expiration period	5 years
Expire within six to fifteen years | State and local jurisdiction
Income Tax [Line Items]
Operating loss carryforwards	$ 2,300
Expire within six to fifteen years | State and local jurisdiction | Minimum
Income Tax [Line Items]
Operating loss carryforwards expiration period	6 years
Expire within six to fifteen years | State and local jurisdiction | Maximum
Income Tax [Line Items]
Operating loss carryforwards expiration period	15 years
Expire over next twenty years | State and local jurisdiction
Income Tax [Line Items]
Operating loss carryforwards expiration period	20 years
Expire over next twenty years | Non US
Income Tax [Line Items]
Operating loss carryforwards	$ 900
Carried forward indefinitely | Non US
Income Tax [Line Items]
Operating loss carryforwards	18,600
Other assets
Income Tax [Line Items]
Non-current deferred tax assets	27,300	26,400
Other liabilities
Income Tax [Line Items]
Non-current deferred tax liabilities	$ 22,500	$ 23,400

Income Taxes (Detail) - Summary

Income Taxes (Detail) - Summary of Components of Income Before Income Taxes - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest [Abstract]
U.S.	$ 182,178	$ 165,848	$ 188,963
Non-U.S.	106,253	106,363	85,720
Income before income taxes	$ 288,431	$ 272,211	$ 274,683

Income Taxes (Detail) - Compone

Income Taxes (Detail) - Components of Income Tax Expenses - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current tax expense:
U.S. federal	$ 58,616	$ 48,801	$ 49,281
State and local	11,292	10,300	5,135
Foreign	27,536	23,225	16,653
Total current	97,444	82,326	71,069
Deferred tax (benefit) expense:
U.S. federal	(61)	(884)	(6,670)
State and local	(349)	(702)	6,477
Foreign	(1,626)	1,550	779
Total deferred	(2,036)	(36)	586
Total current and deferred	95,408	82,290	71,655
Total tax expense	94,849	96,576	90,917
Benefit (expense) relating to interest rate swaps used to increase (decrease) equity
Deferred tax (benefit) expense:
Other tax benefit (expense)	(1,113)	893	(1,442)
Benefit from stock transactions with employees used to increase equity
Deferred tax (benefit) expense:
Other tax benefit (expense)	52	13,960	18,704
Benefit (expense) relating to defined-benefit pension adjustments used to increase (decrease) equity
Deferred tax (benefit) expense:
Other tax benefit (expense)	$ 502	$ (567)	$ 2,000

Income Taxes (Detail) - Current

Income Taxes (Detail) - Current and Long-Term Deferred Tax Assets and Liabilities - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Accrued liabilities	$ 62,439	$ 67,888
Loss and credit carryforwards	7,766	8,522
Assets relating to equity compensation	25,569	22,686
Other assets	6,652	6,712
Gross deferred tax assets	102,426	105,808
Property, equipment, and leasehold improvements	(11,796)	(9,904)
Intangible assets	(43,548)	(55,275)
Prepaid expenses	(32,971)	(28,535)
Other liabilities	(7,925)	(7,244)
Gross deferred tax liabilities	(96,240)	(100,958)
Valuation allowance	(1,431)	(1,828)
Net deferred tax assets	$ 4,755	$ 3,022

Income Taxes (Detail) - Differe

Income Taxes (Detail) - Differences Between U.S. Federal Statutory Income Tax Rate and Effective Tax Rate on Income Before Income Taxes	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Statutory tax rate	35.00%	35.00%	35.00%
State income taxes, net of federal benefit	2.40%	3.30%	3.10%
Effect of non-U.S. operations	(5.90%)	(6.50%)	(6.30%)
Record (release) reserve for tax contingencies	3.20%	1.70%	1.80%
Excess tax benefits from stock based compensation	(3.80%)	(0.00%)	(0.00%)
Nondeductible acquisition costs	2.60%	0.80%	0.10%
Record (release) valuation allowance	(0.20%)	0.50%	0.00%
Other items, net	(0.40%)	0.70%	(0.60%)
Effective tax rate	32.90%	35.50%	33.10%

Income Taxes (Detail) - Reconci

Income Taxes (Detail) - Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits, Excluding Interest and Penalties - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Beginning balance	$ 25,911	$ 20,645
Additions based on tax positions related to the current year	7,086	5,150
Additions for tax positions of prior years	6,443	7,839
Reductions for tax positions of prior years	(496)	(3,880)
Reductions for expiration of statutes	(1,006)	(2,287)
Settlements	(544)	(960)
Change in foreign currency exchange rates	(295)	(596)
Ending balance	$ 37,099	$ 25,911

Derivatives and Hedging (Detail

Derivatives and Hedging (Detail) - Outstanding Derivatives Contracts	12 Months Ended
	Dec. 31, 2016USD ($)contractoutstanding_contract	Dec. 31, 2015USD ($)outstanding_contract
Derivatives, Fair Value [Line Items]
Number of Outstanding Contracts | outstanding_contract	87	105
Contract Notional Amount	$ 786,946,000	$ 893,610,000
Fair Value Asset (Liability)	(2,669,000)	(4,897,000)
AOCI Unrealized (Loss), Net Of Tax	$ (1,409,000)	$ (3,079,000)
Interest rate swap
Derivatives, Fair Value [Line Items]
Number of Outstanding Contracts | contract	3
Contract Notional Amount	$ 700,000,000
Other liabilities | Interest rate swap | Designated as hedging instrument
Derivatives, Fair Value [Line Items]
Number of Outstanding Contracts | outstanding_contract	3	3
Contract Notional Amount	$ 700,000,000	$ 700,000,000
Fair Value Asset (Liability)	(2,349,000)	(5,132,000)
AOCI Unrealized (Loss), Net Of Tax	$ (1,409,000)	$ (3,079,000)
Other current assets | Foreign currency forwards
Derivatives, Fair Value [Line Items]
Number of Outstanding Contracts | outstanding_contract	84	102
Contract Notional Amount	$ 86,946,000	$ 193,610,000
Fair Value Asset (Liability)	(320,000)	235,000
AOCI Unrealized (Loss), Net Of Tax	$ 0	$ 0

Derivatives and Hedging (Deta72

Derivatives and Hedging (Detail) - Derivative Gains And Losses That Have Been Recognized In Condensed Consolidated Statements Of Operations - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments, gain (loss) recognized in income, net	$ 7.9	$ 8.6	$ 3.6
Interest expense
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments, gain (loss) recognized in income, net	7.6	8.5	4.1
Other expense, net
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments, gain (loss) recognized in income, net	$ 0.3	$ 0.1	$ (0.5)

Fair Value Disclosures (Detail)

Fair Value Disclosures (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Borrowings, fair value disclosure	$ 700
Money market funds at carrying value	10.2	$ 8.7
Cash surrender value of life insurance	$ 27.8	$ 25.5

Fair Value Disclosures (Detai74

Fair Value Disclosures (Detail) - Assets And Liabilities Measured At Fair Value On Recurring Basis - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Assets:
Assets measured at fair value on a recurring basis	$ 38,259	$ 34,755
Liabilities:
Liabilities measured at fair value on a recurring basis	45,909	44,578
Level 1
Assets:
Deferred compensation plan assets	10,247	8,671
Assets measured at fair value on a recurring basis	10,247	8,671
Level 2
Assets:
Deferred compensation plan assets	27,847	25,474
Assets measured at fair value on a recurring basis	28,012	26,084
Liabilities:
Deferred compensation plan liabilities	43,075	39,071
Liabilities measured at fair value on a recurring basis	45,909	44,578
Level 2 | Foreign currency forward contracts
Assets:
Derivative asset	165	610
Liabilities:
Derivative liability	485	375
Level 2 | Interest rate swap contracts
Liabilities:
Derivative liability	$ 2,349	$ 5,132

Employee Benefits (Detail)

Employee Benefits (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Employer matching contribution, percent	4.00%
Maximum annual contribution per employee, amount	$ 7,200
Defined contribution plan cost recognized	22,900,000	$ 20,000,000	$ 17,400,000
Compensation expense related to deferred compensation plan	100,000	500,000	600,000
Expected future benefit payments, in 2017	1,400,000
Expected future benefit payments, in 2018	2,000,000
Expected future benefit payments, in 2019	1,100,000
Expected future benefit payments, in 2020	1,500,000
Expected future benefit payments, in 2021	1,500,000
Expected future benefit payments in the five years thereafter	$ 9,500,000
Expected long-term return on assets	2.70%
Contributions by employer	$ 2,400,000
Benefits paid to participants under defined benefit plans	$ 1,640,000	775,000	1,350,000
Weighted average amortization period	13 years
Future amortization of unrecognized gains losses	$ 300,000
Amortization of deferred actuarial losses from AOCL/I	0	0	$ 0
Other assets	7,800,000	7,900,000
Other assets
Defined Benefit Plan Disclosure [Line Items]
Deferred compensation plan assets	38,100,000	34,100,000
Other liabilities
Defined Benefit Plan Disclosure [Line Items]
Deferred compensation liability	$ 43,100,000	$ 39,100,000

Employee Benefits (Detail) - Co

Employee Benefits (Detail) - Components of Net Periodic Pension Expense - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Service cost	$ 2,780	$ 2,620	$ 2,630
Interest cost	850	790	1,190
Expected return on plan assets	(375)	(345)	(540)
Recognition of actuarial loss	200	300	75
Recognition of termination benefits	0	85	30
Total defined benefit pension expense	$ 3,455	$ 3,450	$ 3,385

Employee Benefits (Detail) - As

Employee Benefits (Detail) - Assumptions Used in Computation of Net Periodic Pension Expense	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
Weighted-average discount rate	1.78%	2.19%	2.15%
Average compensation increase	2.67%	2.66%	2.65%

Employee Benefits (Detail) - In

Employee Benefits (Detail) - Information Related to Changes in Projected Benefit Obligation - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Projected benefit obligation at beginning of year	$ 35,870	$ 38,115	$ 34,585
Service cost	2,780	2,620	2,630
Interest cost	850	790	1,190
Actuarial loss (gain) due to assumption changes and plan experience	1,480	(1,190)	6,300
Additions and contractual termination benefits	0	85	30
Benefits paid	(1,640)	(775)	(1,350)
Foreign currency impact	(940)	(3,775)	(5,270)
Projected benefit obligation at end of year	$ 38,400	$ 35,870	$ 38,115

Employee Benefits (Detail) - Be

Employee Benefits (Detail) - Benefit Plans and Related Amounts Recorded in Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]
Projected benefit obligation	$ 38,400	$ 35,870	$ 38,115	$ 34,585
Pension plan assets at fair value	(14,465)	(13,190)	(13,220)
Funded status – shortfall	23,935	22,680	24,895
Amounts recorded in the Consolidated Balance Sheets for the plans:
Other liabilities — accrued pension obligation	23,935	22,680	24,895
Stockholders’ equity — deferred actuarial loss	$ (5,797)	$ (4,832)	$ (6,028)

Segment Information (Detail)

Segment Information (Detail)	12 Months Ended
	Dec. 31, 2016segment
Segment Reporting Information [Line Items]
Number of reportable segments	3
Maximum
Segment Reporting Information [Line Items]
Percent of target bonus charges allocated to segments	100.00%

Segment Information (Detail) -

Segment Information (Detail) - Information About Reportable Segments - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Operating income	$ 305,141	$ 287,997	$ 286,162
Operating Segments
Segment Reporting Information [Line Items]
Revenues	2,444,540	2,163,056	2,021,441
Total segment gross contribution	1,512,000	1,334,547	1,234,229
Operating Segments | Research
Segment Reporting Information [Line Items]
Revenues	1,829,721	1,583,486	1,445,338
Total segment gross contribution	1,267,760	1,096,827	1,001,914
Operating Segments | Consulting
Segment Reporting Information [Line Items]
Revenues	346,214	327,735	348,396
Total segment gross contribution	107,585	107,193	119,931
Operating Segments | Events
Segment Reporting Information [Line Items]
Revenues	268,605	251,835	227,707
Total segment gross contribution	136,655	130,527	112,384
Corporate and Reconciling Items
Segment Reporting Information [Line Items]
Corporate and other expenses	$ (1,206,859)	$ (1,046,550)	$ (948,067)

Segment Information (Detail) 82

Segment Information (Detail) - Reconciliation of Segment Gross Contribution to Net Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Costs and expenses:
Cost of services and product development	$ 945,648	$ 839,076	$ 797,933
Selling, general and administrative	1,089,184	962,677	876,067
Acquisition and integration charges	42,598	26,175	21,867
Operating income	305,141	287,997	286,162
Interest expense and other	16,710	15,786	11,479
Provision for income taxes	94,849	96,576	90,917
Net income	193,582	175,635	183,766
Operating Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total segment gross contribution	1,512,000	1,334,547	1,234,229
Corporate and Reconciling Items
Costs and expenses:
Cost of services and product development	13,108	10,567	10,721
Selling, general and administrative	1,089,184	962,677	876,067
Depreciation and amortization	61,969	47,131	39,412
Acquisition and integration charges	$ 42,598	$ 26,175	$ 21,867

Segment Information (Detail) 83

Segment Information (Detail) - Summarized Information by Geographic Location - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenues:
Revenues	$ 2,444,540	$ 2,163,056	$ 2,021,441
Long-lived assets:
Long-lived assets	210,877	211,113	190,338
United States and Canada
Revenues:
Revenues	1,519,748	1,347,676	1,204,476
Long-lived assets:
Long-lived assets	143,921	163,933	142,963
Europe, Middle East and Africa
Revenues:
Revenues	616,721	557,165	570,334
Long-lived assets:
Long-lived assets	42,326	31,130	34,093
Other International
Revenues:
Revenues	308,071	258,215	246,631
Long-lived assets:
Long-lived assets	$ 24,630	$ 16,050	$ 13,282

Valuation and Qualifying Acco84

Valuation and Qualifying Accounts (Detail) - Summarized Activity in Allowances - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	$ 6,900	$ 6,700	$ 7,000
Additions Charged to Expense	4,750	3,480	2,950
Additions Charged Against Revenues	4,850	5,420	3,240
Deductions from Reserve	(9,100)	(8,700)	(6,490)
Balance at End of Year	$ 7,400	$ 6,900	$ 6,700

Subsequent Events - (Details)

Subsequent Events - (Details) - Subsequent Event - USD ($)	Jan. 20, 2017	Jan. 05, 2017
Subsequent Event [Line Items]
Line of credit, capacity available for specific purpose	$ 2,275,000,000
Bridge Loan
Subsequent Event [Line Items]
Debt instrument term	11 months 29 days
Line of credit, capacity available for specific purpose	$ 300,000,000
CEB
Subsequent Event [Line Items]
Anticipated aggregate purchase price		$ 2,600,000,000
Business combination, liabilities anticipated to be incurred		$ 900,000,000
Secured Debt
Subsequent Event [Line Items]
Debt instrument term	7 years
Line of credit, capacity available for specific purpose	$ 1,375,000,000
Unsecured Debt
Subsequent Event [Line Items]
Line of credit, capacity available for specific purpose	$ 600,000,000