Gartner (IT) 10-K 26 Feb 14 2013 FY Annual report Financial data

Document_And_Entity_Informatio

Document And Entity Information (USD $)	12 Months Ended
	Dec. 31, 2013	Jan. 31, 2014	Jun. 30, 2013
Document and Entity Information [Abstract]	'	'	'
Entity Registrant Name	'GARTNER INC	'	'
Entity Central Index Key	'0000749251	'	'
Current Fiscal Year End Date	'--12-31	'	'
Entity Filer Category	'Large Accelerated Filer	'	'
Document Type	'10-K	'	'
Document Period End Date	31-Dec-13	'	'
Document Fiscal Year Focus	'2013	'	'
Document Fiscal Period Focus	'FY	'	'
Amendment Flag	'false	'	'
Entity Common Stock, Shares Outstanding	'	91,968,869	'
Entity Well-known Seasoned Issuer	'Yes	'	'
Entity Voluntary Filers	'No	'	'
Entity Current Reporting Status	'Yes	'	'
Entity Public Float	'	'	$5,152,997,503

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Dec. 31, 2013		Dec. 31, 2012
In Thousands, unless otherwise specified
Current assets:	'		'
Cash and cash equivalents	$423,990		$299,852
Fees receivable, net of allowances of $7,000 and $6,400 respectively	490,923		463,968
Deferred commissions	106,287		87,933
Prepaid expenses and other current assets	63,682		75,713
Total current assets	1,084,882		927,466
Property, equipment and leasehold improvements, net	91,759		89,089
Goodwill	519,203		519,506
Intangible assets, net	6,107		11,821
Other assets	81,631		73,395
Total Assets	1,783,582		1,621,277
Current liabilities:	'		'
Accounts payable and accrued liabilities	325,059		287,763
Deferred revenues	766,114		692,237
Current portion of long-term debt	68,750		90,000
Total current liabilities	1,159,923		1,070,000
Long-term debt	136,250		115,000
Other liabilities	126,093		129,604
Total Liabilities	1,422,266		1,314,604
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	718,644		679,871
Accumulated other comprehensive income, net	8,345	[1]	5,968	[1]
Accumulated earnings	1,091,283		908,482
Treasury stock, at cost, 64,268,863 and 62,873,100 common shares, respectively	-1,457,034		-1,287,726
Total Stockholders’ Equity	361,316		306,673
Total Liabilities and Stockholders’ Equity	$1,783,582		$1,621,277
[1]	(1)Amounts in parentheses represent deferred losses.

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parentheticals) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, except Share data, unless otherwise specified
Fees receivable, allowances (in Dollars)	$7,000	$6,400
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)	$0.00	$0.00
Common stock, shares authorized	250,000,000	250,000,000
Common stock, shares issued	156,234,415	156,234,415
Treasury stock, Shares	64,268,863	62,873,100

Consolidated_Statements_of_Ope

Consolidated Statements of Operations (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Revenues:	'		'		'
Research	$1,271,011		$1,137,147		$1,012,062
Consulting	314,257		304,893		308,047
Events	198,945		173,768		148,479
Total revenues	1,784,213		1,615,808		1,468,588
Costs and expenses:	'		'		'
Cost of services and product development	713,484		659,067		608,755
Selling, general and administrative	760,458		678,843		613,707
Depreciation	28,996		25,369		25,539
Amortization of intangibles	5,446		4,402		6,525
Acquisition and integration charges	337		2,420		0
Total costs and expenses	1,508,721		1,370,101		1,254,526
Operating income	275,492		245,707		214,062
Interest income	1,551		1,046		1,249
Interest expense	-10,388		-9,905		-11,216
Other expense, net	-216		-1,252		-1,911
Income before income taxes	266,439		235,596		202,184
Provision for income taxes	83,638		69,693		65,282
Net income	$182,801		$165,903		$136,902
Net income per share:	'		'		'
Basic (in Dollars per share)	$1.97		$1.78		$1.43
Diluted (in Dollars per share)	$1.93		$1.73		$1.39
Weighted average shares outstanding:	'		'		'
Basic (in shares)	93,015	[1]	93,444	[1]	96,019	[1]
Diluted (in shares)	94,830	[1]	95,842	[1]	98,846	[1]
[1]	Company repurchased 3.4 million, 2.7 million, and 5.9 million shares of its Common Stock in 2013, 2012, and 2011, respectively.

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012	Dec. 31, 2011
Net income	$182,801		$165,903	$136,902
Other comprehensive income (loss), net of tax	'		'	'
Foreign currency translation adjustments	503		4,318	-4,454
Interest rate hedge - deferred gain (loss)	2,107		-76	-4,674
Pension - deferred actuarial (loss) gain	-233		-4,067	283
Other comprehensive income (loss), net of tax	2,377	[1]	175	-8,845
Comprehensive income	$185,178		$166,078	$128,057
[1]	(1)Amounts in parentheses represent deferred losses.

Consolidated_Statements_of_Sto

Consolidated Statements of Stockholders' Equity (USD $)	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income, Net	Accumulated Earnings	Treasury Stock
In Thousands, unless otherwise specified
Beginning Balance at Dec. 31, 2010	$187,056	$78	$611,782	$14,638	$605,677	($1,045,119)
Increase (Decrease) in Stockholders' Equity [Roll Forward]	'	'	'	'	'	'
Net income	136,902	'	'	'	136,902	'
Other comprehensive income (loss)	-8,845	'	'	-8,845	'	'
Issuances under stock plans	20,045	'	-23,579	'	'	43,624
Stock compensation tax benefits	25,778	'	25,778	'	'	'
Common share repurchases	-211,986	'	'	'	'	-211,986
Stock compensation expense	32,834	'	32,834	'	'	'
Ending Balance at Dec. 31, 2011	181,784	78	646,815	5,793	742,579	-1,213,481
Increase (Decrease) in Stockholders' Equity [Roll Forward]	'	'	'	'	'	'
Net income	165,903	'	'	'	165,903	'
Other comprehensive income (loss)	175	'	'	175	'	'
Issuances under stock plans	12,433	'	-24,626	'	'	37,059
Stock compensation tax benefits	21,304	'	21,304	'	'	'
Common share repurchases	-111,304	'	'	'	'	-111,304
Stock compensation expense	'	'	36,378	'	'	'
Ending Balance at Dec. 31, 2012	306,673	78	679,871	5,968	908,482	-1,287,726
Increase (Decrease) in Stockholders' Equity [Roll Forward]	'	'	'	'	'	'
Net income	182,801	'	'	'	182,801	'
Other comprehensive income (loss)	2,377	'	'	2,377	'	'
Issuances under stock plans	6,034	'	-21,354	'	'	27,388
Stock compensation tax benefits	25,392	'	25,392	'	'	'
Common share repurchases	-196,696	'	'	'	'	-196,696
Stock compensation expense	34,735	'	34,735	'	'	'
Ending Balance at Dec. 31, 2013	$361,316	$78	$718,644	$8,345	$1,091,283	($1,457,034)

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Operating activities:	'	'	'
Net income	$182,801	$165,903	$136,902
Adjustments to reconcile net income to net cash provided by operating activities:	'	'	'
Depreciation and amortization of intangibles	34,442	29,771	32,064
Stock-based compensation expense	34,735	36,378	32,865
Excess tax benefits from employee stock-based compensation exercises	-25,392	-21,304	-25,572
Deferred taxes	16,663	973	-965
Amortization and write-off of debt issue costs	2,710	2,008	2,288
Changes in assets and liabilities:	'	'	'
Fees receivable, net	-28,097	-38,617	-58,887
Deferred commissions	-18,608	-8,871	-6,928
Prepaid expenses and other current assets	-1,187	-10,604	3,540
Other assets	-5,268	15,113	4,397
Deferred revenues	80,938	71,645	91,765
Accounts payable, accrued, and other liabilities	41,917	37,418	44,097
Cash provided by operating activities	315,654	279,813	255,566
Investing activities:	'	'	'
Additions to property, equipment and leasehold improvements	-36,498	-44,337	-41,954
Acquisitions (net of cash received)	0	-10,336	0
Cash used in investing activities	-36,498	-54,673	-41,954
Financing activities:	'	'	'
Proceeds from employee stock-based compensation plans and ESP Plan	6,042	12,430	20,011
Proceeds from borrowings	205,625	35,000	0
Payments on debt	-205,625	-30,000	-20,156
Purchases of treasury stock	-181,736	-111,304	-211,986
Fees paid for debt refinancing	-3,553	0	0
Excess tax benefits from employee stock-based compensation exercises	25,392	21,304	25,572
Cash used by financing activities	-153,855	-72,570	-186,559
Net increase in cash and cash equivalents	125,301	152,570	27,053
Effects of exchange rates on cash and cash equivalents	-1,163	4,543	-4,495
Cash and cash equivalents, beginning of period	299,852	142,739	120,181
Cash and cash equivalents, end of period	423,990	299,852	142,739
Cash paid during the period for:	'	'	'
Interest	8,500	8,968	13,312
Income taxes, net of refunds received	$50,767	$46,907	$24,126

Business_and_Significant_Accou

Business and Significant Accounting Policies	12 Months Ended
	Dec. 31, 2013
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 2013, 2012, and 2011 herein refer to the fiscal year unless otherwise indicated.
	Principles of consolidation. The accompanying consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All significant intercompany transactions and balances have been eliminated.
	Use of estimates. The preparation of the accompanying consolidated financial statements requires management to make estimates and assumptions about future events. These estimates and the underlying assumptions affect the amounts of assets and liabilities reported, disclosures about contingent assets and liabilities, and reported amounts of revenues and expenses. Such estimates include the valuation of accounts 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, and the allowance for losses. 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.
	Acquisitions. The Company accounts for 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 consideration paid to be allocated to the net assets and liabilities acquired based on their estimated fair values as of the acquisition date, and any excess of the purchase price over the estimated fair value of the net assets acquired, including identifiable intangible assets, must be allocated 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.
	In 2012 the Company acquired 100% of the outstanding shares of Ideas International Limited (“Ideas International”), a publicly-owned Australian corporation for aggregate cash consideration of $18.8 million. The operating results of Ideas International were not material to the Company’s 2012 results. The Company recorded $7.5 million of goodwill and $8.5 million of amortizable intangible assets as a result of the acquisition. The Company also recorded $0.3 million and $2.4 million of pre-tax charges in 2013 and 2012, respectively, related to the acquisition, which are classified in Acquisition and integration charges in the Consolidated Statements of Operations.
	Revenues. Revenue is recognized in accordance with U.S. GAAP and SEC Staff Accounting Bulletin No. 101, Revenue Recognition in Financial Statements (“SAB 101”), 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 presents 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 derived from annual subscription contracts for research products. These revenues are deferred and recognized ratably over the applicable contract term. The Company typically enters into annually renewable subscription contracts for research products. Reprint fees are recognized when the reprint is shipped.
	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 entire 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 $37.0 million at December 31, 2013 and $34.0 million at December 31, 2012.
	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 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 expected direct costs of producing a scheduled event will exceed 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 as an increase to expense. The amount of the allowance for losses is based on historical loss experience, aging of outstanding receivables, our assessment of current economic conditions and the financial health of specific clients.
	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 (“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 505 and 718, as interpreted by 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 2013, 2012 and 2011, the Company recognized $34.7 million, $36.4 million, and $32.9 million, respectively, of stock-based compensation expense, a portion of which is recorded in both COS and SG&A in the Consolidated Statements of Operations (see Note 8 — Stock-Based Compensation for additional information).
	Income tax expense. 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. We record a valuation allowance to reduce our deferred tax assets when future realization is in question. We consider the availability of loss carryforwards, existing deferred tax liabilities, future taxable income and ongoing prudent and feasible tax planning strategies in assessing the need for the valuation allowance. In the event we determine that we are able to realize our deferred tax assets in the future in excess of the net recorded amount, an adjustment is made to reduce the valuation allowance and increase income in the period such determination is made. Likewise, if we determine that we will not be able to realize all or part of our net deferred tax asset in the future, an adjustment to the valuation allowance is charged against income in the period such determination is made.
	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 $30.8 million, $30.3 million, and $26.2 million in 2013, 2012, and 2011, 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 $29.0 million, $25.4 million, and $25.5 million in 2013, 2012, and 2011, respectively. The Company's total fixed assets, less accumulated depreciation and amortization, consisted of the following (in thousands):
			Useful Life		December 31,
	Category		(Years)		2013				2012
	Computer equipment and software		7-Feb		$	136,640			$	135,167
	Furniture and equipment		8-Mar		34,024				29,907
	Leasehold improvements		15-Feb		70,261				64,346
					$	240,925			$	229,420
	Less — accumulated depreciation and amortization				(149,166		)		(140,331		)
	Property, equipment, and leasehold improvements, net				$	91,759			$	89,089
	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 350 are capitalized and amortized over future periods. At December 31, 2013 and 2012, net capitalized development costs for internal use software were $14.1 million and $14.4 million, 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 $8.2 million, $7.4 million, and $7.8 million during 2013, 2012, and 2011, respectively.
	Stamford headquarters lease
	The Company’s corporate headquarters is located in 213,000 square feet of leased office space in three buildings in Stamford, Connecticut. In addition to the Company's executive offices, the facility hosts a number of business and support functions. In 2010 the Company entered into a new lease agreement for this facility which was accounted for as an operating lease arrangement. The total minimum payments the Company is obligated to pay under this lease, including contractual escalation clauses and reduced rents during the renovation period (see below), are being expensed on a straight-line basis over the lease term.
	Under this lease arrangement, the landlord provided a $25.0 million tenant improvement allowance which was used to renovate the three buildings. The renovation work began in 2011 and was completed in 2013. The Company paid $7.7 million, $17.0 million, and $9.5 million in renovation costs for this project in 2013, 2012, and 2011, respectively, which are recorded as leasehold improvement assets and are being amortized over their useful lives. The paid renovation costs were classified as cash outflows in the Investing activities section of the Company’s Consolidated Statements of Cash Flows. The Company received landlord cash reimbursements for these expenditures of $3.0 million, $13.0 million, and $9.0 million in 2013, 2012, and 2011, respectively, which were recorded as deferred rent and are being amortized as a reduction to rent expense on a straight-line basis over the term of the lease. The landlord cash reimbursements were classified as cash inflows in the Operating activities section of the Company’s Consolidated Statements of Cash Flows.
	Intangible assets. The Company has amortizable 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, 2013 are as follows (in thousands):
	31-Dec-13		Trade				Customer				Content				Software			Total
			Name				Relationships
	Gross cost, December 31, 2012		$	6,019			$	10,562			$	3,447			$	2,124		$	22,152
	Foreign currency translation impact		4				(416		)		49				19			(344		)
	Gross cost		6,023				10,146				3,496				2,143			21,808
	Accumulated amortization (1), (2)		(4,817		)		(8,372		)		(1,388		)		(1,124		)	(15,701		)
	Balance, December 31, 2013		$	1,206			$	1,774			$	2,108			$	1,019		$	6,107
	31-Dec-12		Trade				Customer				Content				Software			Total
			Name				Relationships
	Gross cost, December 31, 2011		$	5,758			$	7,210			$	—			$	—		$	12,968
	Additions due to acquisition (3)		240				3,170				3,170				1,955			8,535
	Foreign currency translation impact		21				182				277				169			649
	Gross cost		6,019				10,562				3,447				2,124			22,152
	Accumulated amortization (1), (2)		(3,531		)		(5,896		)		(497		)		(407		)	(10,331		)
	Balance, December 31, 2012		$	2,488			$	4,666			$	2,950			$	1,717		$	11,821
	-1	Intangible assets are amortized against earnings over the following periods: Trade name— 2 to 5 years; Customer relationships—4 years; Content—4 years; Software—3 years.
	-2	Aggregate amortization expense related to intangible assets was $5.4 million, $4.4 million, and $6.5 million in 2013, 2012, and 2011, respectively.
	-3	The additions are from the Company's acquisition of Ideas International. See Acquisitions above for additional information.
	The estimated future amortization expense by year from amortizable intangibles is as follows (in thousands):
	2014	$	3,530
	2015	1,915
	2016	662
		$	6,107
	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 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 qualitative 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.
The Company conducted a qualitative assessment of the fair value of its three reporting units as of September 30, 2013 based in part on the demonstrated historical trend of the fair values of the Company’s reporting units substantially exceeding their carrying values and the Company's recent financial performance. Among the factors included in the Company’s qualitative assessment were general economic conditions and the competitive environment; actual and projected reporting unit financial performance; forward-looking business measurements; and external market assessments. Based on the results of the qualitative assessment, the Company believes the fair values of its reporting units continue to substantially exceed their respective carrying values.
The following table presents changes to the carrying amount of goodwill by reporting unit during the two year period ended December 31, 2013 (in thousands):
	Research				Consulting				Events				Total
Balance, December 31, 2011 (1)	$	366,980			$	99,677			$	41,893			$	508,550
Addition due to acquisition (2)	7,455				—				—				7,455
Foreign currency translation adjustments	2,790				672				39				3,501
Balance, December 31, 2012	$	377,225			$	100,349			$	41,932			$	519,506
Foreign currency translation adjustments	(657		)		328				26				(303		)
Balance, December 31, 2013	$	376,568			$	100,677			$	41,958			$	519,203
-1	The Company does not have an accumulated goodwill impairment loss.
-2	The additions are from the Company's acquisition of Ideas International. See Acquisitions above for additional information.
Impairment of long-lived and intangible assets. The Company reviews its long-lived and intangible assets other than goodwill 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’s policy regarding long-lived assets and intangible assets other than goodwill is to evaluate the recoverability of these assets by determining whether the balance can be recovered through undiscounted future operating cash flows. Should 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 material impairment charges for long-lived and intangible assets during the three year period ended December 31, 2013.
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 715. The Company determines the periodic pension expense and related liabilities for these plans through actuarial assumptions and valuations. The Company recognized $3.8 million, $2.6 million, and $2.7 million of expense for these plans in 2013, 2012, and 2011, 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. Accrued interest on amounts borrowed is classified in Interest expense in the Consolidated Statements of Operations. The Company had $205.0 million of debt outstanding at both December 31, 2013 and 2012 (see Note 5—Debt for additional information).
Foreign currency exposure. All assets and liabilities of foreign subsidiaries are translated into U.S. dollars at exchange rates in effect at the balance sheet date. Income and expense items are translated at average exchange rates for the year. The resulting translation adjustments are recorded as foreign currency translation adjustments, a component of Accumulated other comprehensive income, net within the Stockholders’ equity section of the Consolidated Balance Sheets.
Currency transaction gains or losses arising from transactions denominated in currencies other than the functional currency of a subsidiary are recognized in results of operations in Other expense, net within the Consolidated Statements of Operations. Net currency transaction losses were $(0.9) million, $(2.3) million, and $(1.3) million in 2013, 2012, and 2011, 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 expense, net. The net (loss) gain from these contracts was $(0.1) million, $0.6 million, $(1.2) million in 2013, 2012, and 2011, respectively.
Comprehensive income. The Company reports comprehensive income in a separate statement termed the Consolidated Statements of Comprehensive Income, which is included herein. The additional required comprehensive income disclosures are included in Note 2 — Comprehensive Income.
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, accounts receivable, interest rate swaps, and a pension reinsurance asset. The majority of the Company’s cash equivalent investments and its interest rate swap contract are with investment grade commercial banks that are participants in the Company’s credit facility. Accounts 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, 2013.
Stock repurchase programs. The Company records the cost to repurchase its own common shares to treasury stock. During 2013, 2012 and 2011, the Company recorded $196.7 million, $111.3 million, and $212.0 million, respectively, of stock repurchases (see Note 7 — Stockholders’ Equity). Shares repurchased by the Company are added to treasury shares and are not retired.
Adoption of new accounting rules. The Company adopted new accounting rules in the year ended December 31, 2013 related to accumulated other comprehensive income (see Note 2 - Comprehensive Income) and balance sheet offsetting of receivables and payables arising from derivative contracts (see Note 11 - Derivatives and Hedging). The adoption of these new rules resulted in additional disclosure only.
Recent accounting developments. Accounting rules that have been issued by the FASB that have not yet become effective and that may impact the Company’s consolidated financial statements or related disclosures in future periods are described below:
In July 2013, the FASB issued ASU No. 2013-11, "Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists" ("ASU 2013-11"). ASU 2013-11 addresses the balance sheet presentation of an unrecognized tax benefit when a net operating loss carryforward, a similar tax loss, or a tax credit carryforward exists. ASU 2013-11 requires that an unrecognized tax benefit, or a portion of an unrecognized tax benefit, should be presented in the financial statements as a reduction to a deferred tax asset for a net operating loss carryforward, a similar tax loss, or a tax credit carryforward. ASU No. 2013-11 is effective for the Company’s fiscal quarter ending March 31, 2014 and impacts balance sheet presentation only. The Company believes the balance sheet impact will not be material.
In March 2013, the FASB issued ASU No. 2013-05, Parent’s Accounting for the Cumulative Translation Adjustment upon Derecognition of Certain Subsidiaries or Groups of Assets within a Foreign Entity or of an Investment in a Foreign Entity. ASU No. 2013-05 provides updated guidance to resolve diversity in practice concerning the release of the cumulative foreign currency translation adjustment into net income when a parent sells a part or all of its investment in a foreign entity or no longer holds a controlling financial interest in a subsidiary or group of assets within a foreign entity. When a company ceases to have a controlling financial interest, the company should recognize any related cumulative translation adjustment into net income only if the sale or transfer results in the complete or substantially complete liquidation of the foreign entity in which the subsidiary had resided. Upon a partial sale, the company should release into earnings a pro rata portion of the cumulative translation adjustment. ASU No. 2013-05 is effective for the Company’s fiscal quarter ending March 31, 2014. The guidance in ASU 2013-05 will only impact the Company's financial statements upon the occurrence of a transaction within its scope.

Comprehensive_Income

Comprehensive Income	12 Months Ended
	Dec. 31, 2013
Equity [Abstract]	'
COMPREHENSIVE INCOME	'
	COMPREHENSIVE INCOME
	On January 1, 2013, the Company adopted FASB Accounting Standards Update 2013-2, Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income, an amendment to FASB ASC Topic 220, Comprehensive Income ("ASU 2013 -2"). ASU 2013-2 requires entities to prospectively disclose the changes in accumulated other comprehensive income (“AOCI’) by component as well as amounts reclassified out of AOCI to income during the period.
	The information required by ASU 2013-2 for the year ended December 31, 2013 is presented in the following table, net of tax (in thousands) (1):
		Interest Rate Swap			Defined Benefit Pension Plans			Foreign Currency Translation Adjustments		Total
	Balance - December 31, 2012	$	(6,010	)	$	(1,578	)	$	13,556	$	5,968
	Changes during the period:
	Change in AOCI before reclassifications to income	(297		)	(257		)	503		(51		)
	Reclassifications from AOCI to income during the period (2), (3)	2,404			24			—		2,428
	Other comprehensive income (loss) for the period	2,107			(233		)	503		2,377
	Balance - December 31, 2013	$	(3,903	)	$	(1,811	)	$	14,059	$	8,345
	-1	Amounts in parentheses represent deferred losses.
	-2	The interest rate swap is accounted for as a cash flow hedge. The reclassified amount resulted in additional expense for the period which was recorded in Interest expense in the Consolidated Statements of Operations and is net of $1.6 million of related tax benefit reflected in the Provision for income taxes. See Note 11 - Derivatives and Hedging for additional information regarding the swap and the Company's hedging activities.
	-3	The pension reclassification amount was recorded in SGA expense in the Consolidated Statements of Operations and had an immaterial tax effect. See Note 13 - Employee Benefits for additional information regarding the Company's defined benefit pension plans.

Other_Assets

Other Assets	12 Months Ended
	Dec. 31, 2013
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]	'
OTHER ASSETS	'
	OTHER ASSETS
	Other assets consist of the following (in thousands):
		December 31,
		2013		2012
	Security deposits	$	5,505	$	7,740
	Debt issuance costs	4,878		2,768
	Benefit plan-related assets	42,367		37,016
	Non-current deferred tax assets	24,371		22,527
	Other	4,510		3,344
	Total other assets	$	81,631	$	73,395

Accounts_Payable_Accrued_and_O

Accounts Payable, Accrued, and Other Liabilities	12 Months Ended
	Dec. 31, 2013
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,
		2013		2012
	Accounts payable	$	17,671	$	27,344
	Payroll, employee benefits, severance	83,224		71,892
	Bonus payable	75,758		68,776
	Commissions payable	57,078		49,128
	Taxes payable	14,392		18,897
	Rent and other facilities costs	3,903		4,310
	Professional, consulting, audit fees	9,159		8,355
	Events fulfillment liabilities	6,600		4,209
	Other accrued liabilities	57,274		34,852
	Total accounts payable and accrued liabilities	$	325,059	$	287,763
	Other liabilities consist of the following (in thousands):
		December 31,
		2013		2012
	Non-current deferred revenue	$	8,959	$	5,508
	Interest rate swap liability	6,505		10,017
	Long-term taxes payable	9,590		16,760
	Deferred rent (1)	18,127		19,586
	Benefit plan-related liabilities	58,000		54,779
	Other	24,912		22,954
	Total other liabilities	$	126,093	$	129,604
	-1	Represents the remaining unamortized long-term deferred rent on the $25.0 million tenant improvement allowance on the Company’s Stamford headquarters facility. See Note 1 — Business and Significant Accounting Policies above for additional information.

Debt

Debt	12 Months Ended
	Dec. 31, 2013
Debt Disclosure [Abstract]	'
DEBT	'
	DEBT
	2013 Credit Agreement
	The Company entered into a new credit arrangement in early 2013 (the “2013 Credit Agreement”) to take advantage of favorable credit conditions. The 2013 Credit Agreement provides for a five-year, $150.0 million term loan and a $600.0 million revolving credit facility. In addition, the 2013 Credit Agreement contains an expansion feature by which the term loan and revolving credit facility may be increased, at the Company’s option and under certain conditions, by up to an additional $250.0 million in the aggregate.
	The term loan will be repaid in 16 consecutive quarterly installments which commenced on June 30, 2013, plus a final payment due in March 2018, and may be prepaid at any time without penalty or premium (other than applicable breakage costs) at the Company’s option. The revolving credit facility may be used for loans, and up to $40.0 million may be used for letters of credit. The revolving loans may be borrowed, repaid and re-borrowed until March 2018, at which time all amounts borrowed must be repaid. The Company recorded a charge of $0.3 million for capitalized debt issuance costs related to the termination of the previous credit arrangement, which was recorded in Interest expense, net in the Condensed Consolidated Statements of Operations. The Company incurred $3.6 million in debt issuance costs related to the new credit facility, which was capitalized and is being amortized to interest expense over the term of the 2013 Credit Agreement.
	Amounts borrowed under the 2013 Credit Agreement bear interest at a rate equal to, at Gartner’s option, either (1) the greatest of: the Administrative Agent’s prime rate; the average rate on overnight federal funds plus 1/2 of 1%; and the Eurodollar rate (adjusted for statutory reserves) plus 1%, in each case plus a margin equal to between 0.25% and 0.75% depending on Gartner’s 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 1.25% and 1.75%, depending on Gartner’s leverage ratio as of the end of the four consecutive fiscal quarters most recently ended. The 2013 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, 2013.
	The following table summarizes the Company’s total outstanding borrowings (in thousands):
		Amount Outstanding December 31,		Amount Outstanding December 31,
	Description:	2013		2012
	Term loan (1)	$	144,375	$	150,000
	Revolver (1), (2)	55,625		50,000
	Other (3)	5,000		5,000
	Total (4)	$	205,000	$	205,000
	-1	The contractual annual interest rate as of December 31, 2013 on both the term loan and the revolver was 1.62%, which consisted of a floating Eurodollar base rate of 0.24% plus a margin of 1.38%. However, the Company has an interest rate swap contract which converts the floating Eurodollar base rate to a 2.26% fixed base rate on the first $200.0 million of Company borrowings (see below). As a result, the Company’s effective annual interest rate on the $200.0 million of outstanding debt under the 2013 Credit Facility as of December 31, 2013, including the margin, was 3.64%.
	-2	The Company had $541.1 million of available borrowing capacity on the revolver (not including the expansion feature) as of December 31, 2013.
	-3	Consists of a $5.0 million State of Connecticut economic development loan with a 3.0% fixed rate of interest. The loan was originated in 2012 and has a 10 year maturity. Principal payments are deferred for the first five years and the loan may be repaid at any point by the Company without penalty. The loan has a principal forgiveness provision in which up to $2.5 million of the loan may be forgiven if the Company meets certain employment targets during the first five years of the loan.
	-4	As of December 31, 2013, $68.7 million of debt was classified as short term and $136.3 million was classified as long term on the Consolidated Balance Sheets.
	Interest Rate Hedge
	The Company has a $200.0 million notional fixed-for-floating interest rate swap contract which it designates as a hedge of the forecasted interest payments on the Company’s variable rate borrowings. Under the swap terms, the Company pays a base fixed rate of 2.26% and in return receives a floating Eurodollar rate.
	The Company accounts for the interest rate swap as a cash flow hedge in accordance with FASB ASC Topic 815. Since the swap is hedging forecasted interest payments, changes in the fair value of the swap are recorded in OCI as long as the swap continues to be a highly effective hedge of the designated interest rate risk. Any ineffective portion of change in the fair value of the hedge is recorded in earnings. At December 31, 2013, there was no ineffective portion of the hedge. The interest rate swap had a negative fair value to the Company of $6.5 million which is recorded in Other liabilities in the Consolidated Balance Sheets.
	Letters of Credit
	The Company had $9.8 million of letters of credit and related guarantees outstanding at year-end 2013. 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, 2013
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 2014 and 2027. The future minimum annual cash payments under these operating lease agreements as of December 31, 2013 were as follows (in thousands):
	Year ended December 31,
	2014	$	34,525
	2015	27,720
	2016	20,415
	2017	14,840
	2018	11,145
	Thereafter	82,485
	Total minimum lease payments (1)	$	191,130
	-1	Excludes $1.2 million of future contractual sublease rental income.
	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, 2013, we did not have any indemnification agreements that could require material payments.

Stockholders_Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2013
Equity [Abstract]	'
STOCKHOLDERS’ EQUITY	'
	STOCKHOLDERS’ EQUITY
	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 credit arrangement 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’ ending December 31, 2013:
		Issued	Treasury
		Shares	Stock
			Shares
	Balance at December 31, 2010	156,234,415	60,245,718
	Issuances under stock plans	—	(3,244,705	)
	Purchases for treasury (1)	—	5,890,238
	Balance at December 31, 2011	156,234,415	62,891,251
	Issuances under stock plans	—	(2,756,389	)
	Purchases for treasury (1)	—	2,738,238
	Balance at December 31, 2012	156,234,415	62,873,100
	Issuances under stock plans	—	(2,037,091	)
	Purchases for treasury (1)	—	3,432,854
	Balance at December 31, 2013	156,234,415	64,268,863
	-1	The total cost of repurchased shares in 2013 was $196.7 million, of which $181.7 million was paid in 2013 and $15.0 million was paid in early 2014. The total cost of repurchased shares in 2012 and 2011 was $111.3 million and $212.0 million respectively.
	Share repurchase authorization. On February 4, 2014, the Company’s Board of Directors authorized $800.0 million to repurchase the Company's common stock. This authorization succeeds the Company’s prior $500.0 million share repurchase authorization, which was substantially utilized. The Company may repurchase its common stock from time to time in amounts and at prices the Company deems appropriate, subject to the availability of stock, prevailing market conditions, the trading price of the stock, the Company’s financial performance and other conditions. Repurchases may be made through open market purchases, private transactions or other transactions and will be funded from cash on hand and borrowings under the Company’s credit agreement.

StockBased_Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2013
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, 2013, the Company had 6.4 million shares of Common Stock available for awards of stock-based compensation under its 2003 Long-Term Incentive Plan.
	On February 4, 2014, the Board of Directors approved a new 2014 Long-Term Incentive Plan, the adoption of which is subject to approval at the 2014 Annual Meeting of Stockholders. The 2014 plan is substantially similar to the 2003 plan. Shares remaining under the 2003 plan will be carried forward to the 2014 plan, and, in addition, the Company will seek approval for additional shares (to be determined) such that the total available shares under the 2014 plan will be within the acceptable parameters set by Institutional Shareholder Services for equity plans. The awards discussed below are available for grant under both the 2003 plan and the 2014 plan.
	The Company accounts for stock-based compensation awards in accordance with FASB ASC Topics 505 and 718, as interpreted by SEC Staff Accounting Bulletins No. 107 (“SAB No. 107”) and No. 110 (“SAB No. 110”). Stock-based compensation expense is based on the fair value of the award on the date of grant, which is then recognized as expense over the related service period, net of estimated forfeitures. 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 amount of employee forfeitures and the likelihood of the achievement of certain performance targets. The assumptions used in calculating the fair value of stock-based compensation awards and the associated periodic expense represent management’s best estimates, which involve inherent uncertainties and the application of judgment. As a result, if factors change and the Company deems it necessary in the future to modify the assumptions it made or to use different assumptions, or if the quantity and nature of the Company’s stock-based compensation awards changes, then the amount of expense may need to be adjusted and future stock-based compensation expense could be materially different from what has been recorded in the current period.
	The Company recognized the following amounts of stock-based compensation expense by award type for the years ended December 31 (in millions):
	Award type:		2013				2012				2011
	Stock appreciation rights		$	5.2			$	6.4			$	4.4
	Common stock equivalents		0.6				0.5				0.5
	Restricted stock units		28.9				29.5				28
	Total (1)		$	34.7			$	36.4			$	32.9
	-1	Includes charges of $12.5 million, $5.1 million, and $3.1 million in 2013, 2012 and 2011, respectively, for awards to retirement-eligible employees since these awards vest on an accelerated basis
	Stock-based compensation expense was recognized by line item in the Consolidated Statements of Operations for the years ended December 31 (in millions):
	Amount recorded in:		2013				2012				2011
	Costs of services and product development		$	15.3			$	15.3			$	14.8
	Selling, general, and administrative		19.4				21.1				18.1
	Total		$	34.7			$	36.4			$	32.9
	As of December 31, 2013, the Company had $41.0 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 2.2 years.
	Stock-Based Compensation Awards
	The following disclosures provide information regarding the Company’s stock-based compensation awards, all of which are classified as equity awards in accordance with FASB ASC Topic 505:
	Stock Appreciation Rights
	Stock-settled stock appreciation rights (SARs) permit the holder to participate in the appreciation of the Common Stock. SARs are settled in shares of Common Stock by the employee once the applicable vesting criteria have been met. SARs vest ratably over a four-year service period and expire seven years from the grant date. The fair value of SARs awards is recognized as compensation expense on a straight-line basis over four years. SARs have only been awarded to the Company’s executive officers.
	When SARs are exercised, the number of shares of Common Stock issued is calculated as follows: (1) the total proceeds from the SARs exercise (calculated as the closing price of the Common Stock on the date of exercise less the exercise price of the SARs, multiplied by the number of SARs exercised) is divided by (2) the closing price of the Common Stock as reported on the New York Stock Exchange on the exercise date. The Company withholds a portion of the shares of Common Stock issued upon exercise to satisfy minimum statutory tax withholding requirements. SARs recipients do not have any stockholder rights until after actual shares of Common Stock are issued in respect of the award, which is subject to the prior satisfaction of the vesting and other criteria relating to such grants.
	The following table summarizes changes in SARs outstanding for the year ended December 31, 2013:
		SARs in			Per Share				Per Share				Weighted-
		millions			Weighted-				Weighted-				Average
					Average				Average				Remaining
					Exercise Price				Grant Date				Contractual
									Fair Value				Term
	Outstanding at December 31, 2012	2			$	24.59			$	9.04			4.10 years
	Granted	0.4			49.37				14.88				6.12 years
	Forfeited	—			—				—				—
	Exercised	(0.8	)		15.99				6.3				na
	Outstanding at December 31, 2013 (1), (2)	1.6			$	34.14			$	11.63			4.34 years
	Vested and exercisable at December 31, 2013 (1)	0.6			$	25.63			$	9.41			3.33 years
	na =ot applicable
	-1	At December 31, 2013, 1.0 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, 2013, SARs outstanding had an intrinsic value of $59.1 million. SARs vested and exercisable had an intrinsic value of $29.0 million.
	The fair value of the SARs granted was estimated on the date of grant using the Black-Scholes-Merton valuation model with the following weighted-average assumptions for the years ended December 31:
		2013			2012			2011
	Expected dividend yield (1)	—	%		—	%		—	%
	Expected stock price volatility (2)	35	%		40	%		38	%
	Risk-free interest rate (3)	0.8	%		0.8	%		2.2	%
	Expected life in years (4)	4.49			4.61			4.75
	-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 right 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 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, 2013:
		Restricted			Per Share
		Stock Units			Weighted
		(RSUs)			Average
		(in millions)			Grant Date
					Fair Value
	Outstanding at December 31, 2012	2.5			$	27.95
	Granted (1)	0.7			49.86
	Vested and released	(1.4	)		22.47
	Forfeited	—			—
	Outstanding at December 31, 2013 (2), (3)	1.8			$	38.83
	-1	The 0.7 million RSUs granted in 2013 consisted of 0.3 million performance-based RSUs awarded to executives and 0.4 million service-based RSUs awarded to non-executive employees and certain board members. The target number of performance-based RSUs awarded to executives in 2013 was 0.2 million, while the final amount could range from 0% to 200% of the target amount. The final amount was dependent on the increase in the Company's subscription-based contract value ("CV') for the year as measured on December 31, 2013. The actual CV increase achieved for 2013 was 117.1%, which resulted in the grant of 0.3 million performance-based RSUs.
-2	The Company expects that substantially all of the outstanding awards at December 31, 2013 will vest in future periods.
-3	The weighted-average remaining contractual term of the outstanding RSUs is approximately 1 year.
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, 2013:
	Common Stock			Per Share
	Equivalents			Weighted
	(CSEs)			Average
				Grant Date
				Fair Value
Outstanding at December 31, 2012	100,545			$	16.89
Granted	9,718			60.34
Converted to common shares	(7,784	)		60.31
Outstanding at December 31, 2013	102,479			$	17.71
Stock Options
The Company made stock option grants until 2006. As of December 31, 2013, there were less than 0.2 million remaining outstanding unexercised options, which are fully vested and expire in 2015. The Company received cash from options exercises in the amount of $1.7 million, $8.6 million, and $16.6 million in 2013, 2012, and 2011, respectively.
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, 2013, the Company had approximately 1.2 million shares available for purchase under the ESP Plan. The ESP Plan is considered non-compensatory under FASB ASC Topic 718, and as a result the Company does not record stock-based compensation expense for employee share purchases. The Company received $4.4 million, $3.8 million, and $3.4 million in cash from share purchases under the ESP Plan during 2013, 2012, and 2011, respectively.

Computation_of_Earnings_Per_Sh

Computation of Earnings Per Share	12 Months Ended
	Dec. 31, 2013
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 antidilutive, 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):
		2013		2012		2011
	Numerator:
	Net income used for calculating basic and diluted earnings per common share	$	182,801	$	165,903	$	136,902
	Denominator: (1)
	Weighted average number of common shares used in the calculation of basic earnings per share	93,015		93,444		96,019
	Common share equivalents associated with stock-based compensation plans	1,815		2,398		2,827
	Shares used in the calculation of diluted earnings per share	94,830		95,842		98,846
	Earnings per share:
	Basic	$	1.97	$	1.78	$	1.43
	Diluted	$	1.93	$	1.73	$	1.39
	-1	The Company repurchased 3.4 million, 2.7 million, and 5.9 million shares of its Common Stock in 2013, 2012, and 2011, 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 antidilutive. During periods with net income, these common share equivalents were antidilutive because their exercise price was greater than the average market value of a share of Common Stock during the period.
		2013		2012		2011
	Antidilutive common share equivalents as of December 31 (in millions):	0.3		0.7		0.5
	Average market price per share of Common Stock during the year	$	57.5	$	43.8	$	37.53

Income_Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2013
Income Tax Disclosure [Abstract]	'
INCOME TAXES	'
	INCOME TAXES
	Following is a summary of the components of income before income taxes for the years ended December 31 (in thousands):
		2013				2012				2011
	U.S.	$	186,330			$	150,023			$	124,915
	Non-U.S.	80,109				85,573				77,269
	Income before income taxes	$	266,439			$	235,596			$	202,184
	The expense for income taxes on the above income consists of the following components (in thousands):
		2013				2012				2011
	Current tax expense:
	U.S. federal	$	20,111			$	25,290			$	23,327
	State and local	4,943				2,508				4,236
	Foreign	17,460				18,889				13,845
	Total current	42,514				46,687				41,408
	Deferred tax (benefit) expense:
	U.S. federal	18,806				8,494				(5,192		)
	State and local	2,742				(753		)		1,269
	Foreign	(4,688		)		(8,080		)		(1,434		)
	Total deferred	16,860				(339		)		(5,357		)
	Total current and deferred	59,374				46,348				36,051
	Benefit (expense) relating to interest rate swap used to increase (decrease) equity	(1,405		)		51				3,134
	Benefit from stock transactions with employees used to increase equity	25,373				21,304				25,812
	Benefit (expense) relating to defined-benefit pension adjustments used to increase (decrease) equity	482				1,926				285
	Benefit (expense) of acquired tax assets (liabilities) used to decrease (increase) goodwill	(186		)		64				—
	Total tax expense	$	83,638			$	69,693			$	65,282
	Current and long-term deferred tax assets and liabilities are comprised of the following (in thousands):
		December 31,
		2013				2012
	Expense accruals	$	56,787			$	49,404
	Loss and credit carryforwards	17,648				22,433
	Assets relating to equity compensation	19,773				18,878
	Other assets	1,306				7,613
	Gross deferred tax asset	95,514				98,328
	Depreciation	(12,067		)		(8,995		)
	Intangible assets	(25,338		)		(23,129		)
	Prepaid expenses	(22,517		)		(10,500		)
	Gross deferred tax liability	(59,922		)		(42,624		)
	Valuation allowance	(617		)		(1,943		)
	Net deferred tax asset	$	34,975			$	53,761
	Current net deferred tax assets and current net deferred tax liabilities were $19.5 million and $8.7 million as of December 31, 2013 and $32.6 million and $1.3 million as of December 31, 2012, respectively, and are included in Prepaid expenses and other current assets and Accounts payable and accrued liabilities in the Consolidated Balance Sheets. Long-term net deferred tax assets and long-term net deferred tax liabilities were $24.4 million and $0.2 million as of December 31, 2013 and $22.5 million and $0.1 million as of December 31, 2012, respectively, and are included in Other assets and Other liabilities in the Consolidated Balance Sheets. It is more likely than not that the results of future operations will generate sufficient taxable income to realize the deferred tax assets.
	The valuation allowances of $0.6 million as of December 31, 2013 and $1.9 million as of December 31, 2012 largely relate to net operating losses.
	As of December 31, 2013, the Company had state and local tax net operating loss carryforwards of $91.3 million, of which $2.9 million expire within one to five years, $87.3 million expire within six to fifteen years, and $1.1 million expire within sixteen to twenty years. The Company also had state tax credits of $2.9 million which will expire within two to five years.
	As of December 31, 2013, the Company had non-U.S. net operating loss carryforwards of $30.3 million, of which $1.0 million expire over the next 20 years and $29.3 million can be carried forward indefinitely. In addition, the Company also had foreign tax credit carryforwards of $1.3 million, the majority of which expire in 2017.
	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:
		2013			2012			2011
	Statutory tax rate	35	%		35	%		35	%
	State income taxes, net of federal benefit	3.2			1.8			3.8
	Foreign income taxed at different rates	(5.6	)		(6.4	)		(5.9	)
	Foreign tax credits	—			(1.0	)		(2.3	)
	Record (release) reserve for tax contingencies	0.3			0.7			3.1
	Record (release) valuation allowance	(0.5	)		—			(0.4	)
	Other items, net	(1.0	)		(0.5	)		(1.0	)
	Effective tax rate	31.4	%		29.6	%		32.3	%
	In 2013 and 2012 state income taxes, net of federal tax benefit include approximately $1.3 million and $2.6 million, respectively, of benefit relating to economic development tax credits associated with the renovation of the Company’s Stamford headquarters facility.
	As of December 31, 2013 and December 31, 2012, the Company had unrecognized tax benefits of $14.5 million and $17.6 million, respectively. The decrease is primarily attributable to reductions for tax positions of prior years and settlements resulting from closure of tax audits, partially offset by additions in unrecognized tax benefits attributable to 2013. It is reasonably possible that the unrecognized tax benefits will be decreased by $3.1 million within the next 12 months due to anticipated closure of audits and the expiration of certain statutes of limitation. The unrecognized tax benefits relate primarily to the utilization of certain tax attributes.
	The Company classifies uncertain tax positions not expected to be settled within one year as long term liabilities. As of December 31, 2013 and December 31, 2012, the Company had $11.4 million and $13.1 million, respectively, related to long term uncertain tax positions included in Other Liabilities.
	The following is a reconciliation of the beginning and ending amount of unrecognized tax benefits, excluding interest and penalties, for the years ending December 31 (in thousands):
		2013				2012
	Beginning balance	$	17,552			$	18,345
	Additions based on tax positions related to the current year	4,237				4,301
	Additions for tax positions of prior years	827				105
	Reductions for tax positions of prior years	(1,973		)		(3,427		)
	Reductions for expiration of statutes	(3,860		)		(296		)
	Settlements	(1,575		)		(1,372		)
Change in foreign currency exchange rates	(720		)		(104		)
Ending balance	$	14,488			$	17,552
Included in the balance of unrecognized tax benefits at December 31, 2013 are potential benefits of $11.8 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, 2013 are potential benefits of $2.7 million that, if recognized, would result in adjustments to other tax accounts, primarily deferred taxes.
The Company accrues interest and penalties related to unrecognized tax benefits in its income tax provision. As of December 31, 2013 and December 31, 2012, the Company had $3.3 million and $4.6 million of accrued interest and penalties, respectively, 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 Consolidated Statements of Operations for the years ending December 31, 2013 and December 31, 2012 was $0.3 million and $0.4 million, respectively.
The number of years with open statutes of limitation varies depending on the tax jurisdiction. Generally, the Company’s statutes are open for tax years ended December 31, 2008 and forward, with the exception of India which is open for tax years 2003 and forward. Major taxing jurisdictions include the U.S. (federal and state), the United Kingdom, Canada, Japan, Italy, India, and Ireland.
During 2013, the Company closed the Internal Revenue Service (“IRS”) audit of its 2008 and 2009 federal income tax returns. The resolution of the audit did not have a material adverse effect on the consolidated financial position, cash flows, or results of operations of the Company.
In late 2013 the Company received notice that the IRS intends to conduct an audit of the Company's 2010 and 2011 tax years. The audits for these years have commenced and are in the early stages of examination. Although the final resolution of these audits is uncertain, the Company believes that the ultimate disposition will not have a material adverse effect on its consolidated financial position, cash flows, or results of operations.
Earnings of non-U.S. subsidiaries are generally subject to U.S. taxation when repatriated. The Company intends to reinvest these earnings outside the U.S. except in instances where repatriating such earnings would result in minimal additional tax. The Company currently has no plan to remit earnings which will result in a material tax cost. Accordingly, the Company has not recognized additional tax expense that may result from the remittance of such earnings. The accumulated undistributed earnings of non-U.S. subsidiaries are approximately $140.0 million as of December 31, 2013. An estimate of the income tax liability that would be payable if such earnings were not indefinitely invested is $33.0 million.

Derivatives_and_Hedging

Derivatives and Hedging	12 Months Ended
	Dec. 31, 2013
Derivative Instruments and Hedging Activities Disclosure [Abstract]	'
DERIVATIVES AND HEDGING	'
	DERIVATIVES AND HEDGING
	The Company enters into a limited number of derivative contracts to offset the potentially negative economic effects of interest rate and foreign exchange movements. The Company accounts for its outstanding derivative contracts in accordance with FASB ASC Topic 815, which requires all derivatives, including derivatives designated as accounting hedges, to be recorded on the balance sheet at fair value.
	The following tables provide information regarding the Company’s outstanding derivatives contracts as of, and for, the years ended (in thousands, except for number of outstanding contracts):
	December 31, 2013
	Derivative Contract Type		Number of		Contract				Fair Value			Balance Sheet	OCI
			Outstanding		Notional				Asset			Line Item	Unrealized
			Contracts		Amount				(Liability) (3)				(Loss), Net
													Of Tax
	Interest rate swap (1)		1		$	200,000			$	(6,505	)	Other liabilities	$	(3,903	)
	Foreign currency forwards (2)		89		61,325				(60		)	Other current liabilities	—
	Total		90		$	261,325			$	(6,565	)		$	(3,903	)
	December 31, 2012
	Derivative Contract Type		Number of		Contract				Fair Value			Balance Sheet	OCI
			Outstanding		Notional				Asset			Line Item	Unrealized
			Contracts		Amount				(Liability) (3)				(Loss), Net
													Of Tax
	Interest rate swap (1)		1		$	200,000			$	(10,000	)	Other liabilities	$	(6,010	)
	Foreign currency forwards (2)		68		76,100				4			Other current assets	—
	Total		69		$	276,100			$	(9,996	)		$	(6,010	)
	-1	The swap is designated as a cash flow hedge of the forecasted interest payments on borrowings. As a result, changes in the fair value of this swap are deferred and are recorded in OCI, 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 offset the economic effects of these foreign currency transaction risks. 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. Substantially all of the outstanding contracts at December 31, 2013 matured by the end of January 2014.
	-3	See Note 12 — Fair Value Disclosures below for the determination of the fair value of these instruments.
	At December 31, 2013, the Company’s derivative counterparties were all large 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 thousands):
	Amount recorded in:		2013			2012				2011
	Interest expense (1)		$	4		$	3.6			$	4.1
	Other expense, net (2)		0.1			(0.6		)		1.2
	Total expense		$	4.1		$	3			$	5.3
	-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, 2013
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 includes borrowings outstanding under its 2013 Credit Agreement, and at December 31, 2013, the Company had $200.0 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 the borrowings reflect current market rates of interest for similar instruments with comparable maturities.
	FASB ASC Topic 820 provides a framework for the measurement of fair value and a valuation hierarchy based upon the transparency of inputs used in the valuation of assets and liabilities. Classification within the hierarchy is based upon the lowest level of input that is significant to the resulting fair value measurement. The valuation hierarchy contains three levels. Level 1 measurements consist of quoted prices in active markets for identical assets or liabilities. Level 2 measurements include significant other observable inputs such as quoted prices for similar assets or liabilities in active markets; identical assets or liabilities in inactive markets; observable inputs such as interest rates and yield curves; and other market-corroborated inputs. Level 3 measurements include significant unobservable inputs, such as internally-created valuation models. The Company does not currently utilize Level 3 valuation inputs to remeasure any of its assets or liabilities. However, level 3 inputs may be used by the Company in its required annual impairment review of goodwill. Information regarding the periodic assessment of the Company’s 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):
	Description:		Fair Value December 31, 2013		Fair Value December 31, 2012
	Assets:
	Deferred compensation plan assets (1)		$	32,555	$	27,795
	Foreign currency forward contracts (2)		116		204
			$	32,671	$	27,999
	Liabilities:
	Deferred compensation plan liabilities (1)		$	36,410	$	31,260
	Foreign currency forward contracts (2)		176		200
	Interest rate swap contracts (3)		6,505		10,000
			$	43,091	$	41,460
	-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 plan’s 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 $7.8 million and $8.2 million as of December 31, 2013 and 2012, 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 $24.8 million and $19.6 million at December 31, 2013 and 2012, respectively. The related deferred compensation plan liabilities are recorded at the amount needed to settle the liability, which approximates fair value, and is based on 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 an interest rate swap contract which hedges the risk from variability of interest rates on its borrowings (see Note 11 — Derivatives and Hedging). The fair value of the swap is based on a mark-to-market valuation prepared by a third-party broker. Valuation is 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 valuation prepared by the third-party broker through the use of an electronic quotation service.
	Disclosures about Offsetting of Assets and Liabilities
	On January 1, 2013, the Company adopted FASB ASU No. 2013-1, Clarifying the Scope of Disclosures about Offsetting Assets and Liabilities, which updates FASB ASU No. 2011-11, Disclosures about Offsetting Assets and Liabilities. These rules require certain disclosures of assets and liabilities resulting from derivative transactions, repurchase agreements, and securities lending arrangements. Among the required disclosures are the gross amounts of assets and liabilities resulting from these transactions, amounts potentially subject to offset under master netting arrangements, and resulting amounts recorded in the balance sheets.
	The Company enters into a limited number of derivatives transactions but does not enter into repurchase agreements or securities lending transactions. In addition, the Company does not enter into master netting arrangements and receivables or payables that result from derivatives transactions are recorded gross in the Company’s Consolidated Balance Sheets. Information regarding the Company’s derivatives contracts and related amounts recorded in the Consolidated Balance Sheets as of December 31, 2013 and 2012 are included in the fair value table above.

Employee_Benefits

Employee Benefits	12 Months Ended
	Dec. 31, 2013
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 2013, the maximum match was $7,000. Amounts expensed in connection with the 401k Plan totaled $15.8 million, $14.2 million, and $15.9 million, in 2013, 2012, and 2011, 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 classified in Other assets on the Consolidated Balance Sheets at fair value. The value of these assets was $32.6 million and $27.8 million at December 31, 2013 and 2012, respectively (see Note 12 — Fair Value Disclosures for fair value information). The corresponding deferred compensation liability of $36.4 million and $31.3 million at December 31, 2013 and 2012, respectively, is carried at fair value, and is adjusted with a corresponding charge or credit to compensation cost to reflect the fair value of the amount owed to the employees which is classified in Other liabilities on the Consolidated Balance Sheets. Total compensation expense recognized for the plan was $0.4 million in both 2013 and 2012 and $0.3 million in 2011.
	Defined benefit pension plans. The Company has defined-benefit pension plans in several of its non-U.S. locations. Benefits earned under these plans are 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 Topics 715 and 960.
	The following are the components of defined benefit pension expense for the years ended December 31 (in thousands):
		2013				2012				2011
	Service cost (1)	$	2,545			$	1,775			$	1,890
	Interest cost	1,075				980				1,010
	Expected return on plan assets	(340		)		(115		)		(125		)
	Recognition of actuarial loss (gain)	30				(215		)		(135		)
	Recognition of termination benefits	455				175				65
	Total defined benefit pension expense (2)	$	3,765			$	2,600			$	2,705
	-1	The higher 2013 service cost was primarily due to additional employees covered under the plans.
	-2	Pension expense is classified in SG&A in the Consolidated Statements of Operations.
	The following are the assumptions used in the computation of pension expense for the years ended December 31:
		2013			2012			2011
	Weighted-average discount rate (1)	3.35	%		3.2	%		4.4	%
	Average compensation increase	2.7	%		2.7	%		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):
		2013				2012				2011
	Projected benefit obligation at beginning of year	$	31,605			$	21,160			$	19,730
	Service cost	2,545				1,775				1,890
	Interest cost	1,075				980				1,010
	Actuarial loss (gain) due to assumption changes and plan experience (1)	625				6,265				(948		)
	Additions and contractual termination benefits	460				1,925				—
	Benefits paid (2)	(1,255		)		(680		)		(390		)
	Foreign currency impact	(470		)		180				(132		)
	Projected benefit obligation at end of year (3)	$	34,585			$	31,605			$	21,160
	-1	The 2012 actuarial loss was primarily due to a decline in the weighted-average discount rate.
	-2	The Company projects the following approximate amounts will be paid in future years to plan participants: $0.6 million in 2014; $1.8 million in 2015; $0.7 million in 2016; $1.1 million in 2017; $1.0 million in 2018; and $7.5 million in the five years thereafter.
	-3	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:
		2013				2012				2011
	Projected benefit obligation	$	34,585			$	31,605			$	21,160
	Plan assets at fair value (1)	(13,870		)		(8,885		)		(2,480		)
	Funded status – shortfall (2)	$	20,715			$	22,720			$	18,680
	Amounts recorded in the Consolidated Balance Sheets for the plans:
	Other liabilities — accrued pension obligation (2)	$	20,715			$	22,720			$	18,680
	Stockholders’ equity — deferred actuarial (loss) gain (3)	$	(1,811	)		$	(1,578	)		$	2,488
	-1	The 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 820, and the Company considers the overall portfolio of these assets to be of low-to-medium investment risk. The Company projects a future long-term rate of return on these plan assets of 3.8%, 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, 2013, the Company contributed $5.9 million to these plans, and benefits paid to participants were $1.3 million.
	In addition to the plan assets held with third-party trustees, the Company also maintains a reinsurance asset arrangement with a large international insurance company. The reinsurance asset is an asset of the Company whose purpose is to provide funding for benefit payments for one of the plans. At December 31, 2013, the reinsurance asset was carried on the Company’s Consolidated Balance Sheets at its cash surrender value of $9.3 million and is classified in Other Assets. 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 820.
	-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, 2013, is recorded in Accumulated Other Comprehensive Income (“AOCI”) and will be reclassified out of AOCI and recognized as pension expense over approximately 15 years, subject to certain limitations set forth in FASB ASC Topic 715. The impact of this amortization on the periodic pension expense in 2014 is projected to be less than $0.1 million. The actual amortization of deferred actuarial losses (gains) from AOCI to pension expense was less than $0.1 million in 2013, $(0.2) million in 2012, and $(0.1) million in 2011.

Segment_Information

Segment Information	12 Months Ended
	Dec. 31, 2013
Segment Reporting [Abstract]	'
SEGMENT INFORMATION	'
	SEGMENT INFORMATION
	The Company manages its business through three reportable segments: Research, Consulting and Events. Research consists primarily of subscription-based research products, access to research inquiry, peer networking services, and membership programs. Consulting consists primarily of consulting, measurement engagements, and strategic advisory services. Events consists of various symposia, conferences and exhibitions.
	The Company evaluates 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 COS expenses, SG&A expense, depreciation, acquisition and integration charges, and amortization of intangibles. Certain bonus and fringe benefit costs included in consolidated COS 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 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 Company does not identify or allocate assets, including capital expenditures, by reportable segment. Accordingly, assets are not being reported by segment because the information is not available by segment and is not reviewed in the evaluation of performance or making decisions in the allocation of resources.
	The following tables present operating information about the Company’s reportable segments for the years ended December 31 (in thousands):
		Research			Consulting			Events			Consolidated
	2013
	Revenues	$	1,271,011		$	314,257		$	198,945		$	1,784,213
	Gross contribution	879,384			107,565			91,216			1,078,165
	Corporate and other expenses										(802,673		)
	Operating income										$	275,492
		Research			Consulting			Events			Consolidated
	2012
	Revenues	$	1,137,147		$	304,893		$	173,768		$	1,615,808
	Gross contribution	774,342			109,253			80,119			963,714
	Corporate and other expenses										(718,007		)
	Operating income										$	245,707
		Research			Consulting			Events			Consolidated
	2011
	Revenues	$	1,012,062		$	308,047		$	148,479		$	1,468,588
	Gross contribution	682,136			114,838			66,265			863,239
	Corporate and other expenses										(649,177		)
	Operating income										$	214,062
	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,
			2013			2012			2011
	Total segment gross contribution		$	1,078,165		$	963,714		$	863,239
	Costs and expenses:
	Cost of services and product development - unallocated (1)		7,436			6,973			3,406
	Selling, general and administrative		760,458			678,843			613,707
	Depreciation and amortization		34,442			29,771			32,064
	Acquisition and integration charges		337			2,420			—
	Operating income		275,492			245,707			214,062
	Interest expense and other		9,053			10,111			11,878
	Provision for income taxes		83,638			69,693			65,282
	Net income		$	182,801		$	165,903		$	136,902
	-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, and Europe, Middle East, and Africa.
	Summarized information by geographic location as of and for the years ended December 31 follows (in thousands):
		2013			2012			2011
	Revenues:
	United States and Canada	$	1,049,734		$	947,075		$	861,481
	Europe, Middle East and Africa	508,755			458,675			437,194
	Other International	225,724			210,058			169,913
	Total revenues	$	1,784,213		$	1,615,808		$	1,468,588
	Long-lived assets: (1)
	United States and Canada (2)	$	123,877		$	114,557		$	85,194
	Europe, Middle East and Africa	34,363			30,967			23,673
	Other International	13,936			16,956			10,754
	Total long-lived assets	$	172,176		$	162,480		$	119,621
	-1	Excludes goodwill and other intangible assets.
	-2	The United States and Canada balances include costs capitalized in connection with the renovation of the Company’s Stamford headquarters facility (see Note 1 — Business and Significant Accounting Policies for additional description). These capitalized costs amounted to $7.7 million in 2013, $17.0 million in 2012, and $9.5 million in 2011.

Valuation_and_Qualifying_Accou

Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2013
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		Additions		Additions		Deductions			Balance
		Beginning		Charged to		Charged		from			at End
		of Year		Expense		Against		Reserve			of Year
						Revenues
	2013:00:00
	Allowance for doubtful accounts and returns and allowances	$	6,400	$	2,350	$	5,050	$	(6,800	)	$	7,000
	2012:00:00
	Allowance for doubtful accounts and returns and allowances	$	7,260	$	1,930	$	1,860	$	(4,650	)	$	6,400
	2011:00:00
	Allowance for doubtful accounts and returns and allowances	$	7,200	$	930	$	4,390	$	(5,260	)	$	7,260

Subsequent_Event

Subsequent Event	12 Months Ended
	Dec. 31, 2013
Subsequent Events [Abstract]	'
SUBSEQUENT EVENT	'
	SUBSEQUENT EVENT
	On February 4, 2014, the Company’s Board of Directors authorized $800.0 million to repurchase the Company's Common Stock. This authorization succeeds the Company’s prior $500.0 million share repurchase authorization, which was substantially utilized. See Note 7 — Stockholders' Equity above for additional information regarding the $800.0 million share repurchase authorization and the Company's share repurchase activity.

Business_and_Significant_Accou1

Business and Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2013
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 2013, 2012, and 2011 herein refer to the fiscal year unless otherwise indicated.
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 accounts 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, and the allowance for losses. 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.
	Acquisitions. The Company accounts for 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 consideration paid to be allocated to the net assets and liabilities acquired based on their estimated fair values as of the acquisition date, and any excess of the purchase price over the estimated fair value of the net assets acquired, including identifiable intangible assets, must be allocated 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.
	In 2012 the Company acquired 100% of the outstanding shares of Ideas International Limited (“Ideas International”), a publicly-owned Australian corporation for aggregate cash consideration of $18.8 million. The operating results of Ideas International were not material to the Company’s 2012 results. The Company recorded $7.5 million of goodwill and $8.5 million of amortizable intangible assets as a result of the acquisition. The Company also recorded $0.3 million and $2.4 million of pre-tax charges in 2013 and 2012, respectively, related to the acquisition, which are classified in Acquisition and integration charges in the Consolidated Statements of Operations.
Revenues	'
	Revenues. Revenue is recognized in accordance with U.S. GAAP and SEC Staff Accounting Bulletin No. 101, Revenue Recognition in Financial Statements (“SAB 101”), 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 presents 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 derived from annual subscription contracts for research products. These revenues are deferred and recognized ratably over the applicable contract term. The Company typically enters into annually renewable subscription contracts for research products. Reprint fees are recognized when the reprint is shipped.
	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 entire 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 $37.0 million at December 31, 2013 and $34.0 million at December 31, 2012.
	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 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 expected direct costs of producing a scheduled event will exceed 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 as an increase to expense. The amount of the allowance for losses is based on historical loss experience, aging of outstanding receivables, our assessment of current economic conditions and the financial health of specific clients.
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. Commission expense is included in SG&A in the Consolidated Statements of Operations.
Stock-based compensation expense	'
	Stock-based compensation expense. The Company accounts for stock-based compensation in accordance with FASB ASC Topics 505 and 718, as interpreted by SEC Staff Accounting Bulletins No. 107 (“SAB No. 107”) and No. 110 (“SAB No. 110”). Stock-based compensation 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 2013, 2012 and 2011, the Company recognized $34.7 million, $36.4 million, and $32.9 million, respectively, of stock-based compensation expense, a portion of which is recorded in both COS and SG&A in the Consolidated Statements of Operations (see Note 8 — Stock-Based Compensation for additional information).
Income tax expense	'
	Income tax expense.
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 $30.8 million, $30.3 million, and $26.2 million in 2013, 2012, and 2011, 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 $29.0 million, $25.4 million, and $25.5 million in 2013, 2012, and 2011, respectively. The Company's total fixed assets, less accumulated depreciation and amortization, consisted of the following (in thousands):
			Useful Life		December 31,
	Category		(Years)		2013				2012
	Computer equipment and software		7-Feb		$	136,640			$	135,167
	Furniture and equipment		8-Mar		34,024				29,907
	Leasehold improvements		15-Feb		70,261				64,346
					$	240,925			$	229,420
	Less — accumulated depreciation and amortization				(149,166		)		(140,331		)
	Property, equipment, and leasehold improvements, net				$	91,759			$	89,089
	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 350 are capitalized and amortized over future periods. At December 31, 2013 and 2012, net capitalized development costs for internal use software were $14.1 million and $14.4 million, 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 $8.2 million, $7.4 million, and $7.8 million during 2013, 2012, and 2011, respectively.
	Stamford headquarters lease
	The Company’s corporate headquarters is located in 213,000 square feet of leased office space in three buildings in Stamford, Connecticut. In addition to the Company's executive offices, the facility hosts a number of business and support functions. In 2010 the Company entered into a new lease agreement for this facility which was accounted for as an operating lease arrangement. The total minimum payments the Company is obligated to pay under this lease, including contractual escalation clauses and reduced rents during the renovation period (see below), are being expensed on a straight-line basis over the lease term.
	Under this lease arrangement, the landlord provided a $25.0 million tenant improvement allowance which was used to renovate the three buildings. The renovation work began in 2011 and was completed in 2013. The Company paid $7.7 million, $17.0 million, and $9.5 million in renovation costs for this project in 2013, 2012, and 2011, respectively, which are recorded as leasehold improvement assets and are being amortized over their useful lives. The paid renovation costs were classified as cash outflows in the Investing activities section of the Company’s Consolidated Statements of Cash Flows. The Company received landlord cash reimbursements for these expenditures of $3.0 million, $13.0 million, and $9.0 million in 2013, 2012, and 2011, respectively, which were recorded as deferred rent and are being amortized as a reduction to rent expense on a straight-line basis over the term of the lease. The landlord cash reimbursements were classified as cash inflows in the Operating activities section of the Company’s Consolidated Statements of Cash Flows.
Intangible assets	'
	Intangible assets. The Company has amortizable 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, 2013 are as follows (in thousands):
	31-Dec-13		Trade				Customer				Content				Software			Total
			Name				Relationships
	Gross cost, December 31, 2012		$	6,019			$	10,562			$	3,447			$	2,124		$	22,152
	Foreign currency translation impact		4				(416		)		49				19			(344		)
	Gross cost		6,023				10,146				3,496				2,143			21,808
	Accumulated amortization (1), (2)		(4,817		)		(8,372		)		(1,388		)		(1,124		)	(15,701		)
	Balance, December 31, 2013		$	1,206			$	1,774			$	2,108			$	1,019		$	6,107
	31-Dec-12		Trade				Customer				Content				Software			Total
			Name				Relationships
	Gross cost, December 31, 2011		$	5,758			$	7,210			$	—			$	—		$	12,968
	Additions due to acquisition (3)		240				3,170				3,170				1,955			8,535
	Foreign currency translation impact		21				182				277				169			649
	Gross cost		6,019				10,562				3,447				2,124			22,152
	Accumulated amortization (1), (2)		(3,531		)		(5,896		)		(497		)		(407		)	(10,331		)
	Balance, December 31, 2012		$	2,488			$	4,666			$	2,950			$	1,717		$	11,821
	-1	Intangible assets are amortized against earnings over the following periods: Trade name— 2 to 5 years; Customer relationships—4 years; Content—4 years; Software—3 years.
	-2	Aggregate amortization expense related to intangible assets was $5.4 million, $4.4 million, and $6.5 million in 2013, 2012, and 2011, respectively.
	-3	The additions are from the Company's acquisition of Ideas International. See Acquisitions above for additional information.
	The estimated future amortization expense by year from amortizable intangibles is as follows (in thousands):
	2014	$	3,530
	2015	1,915
	2016	662
		$	6,107
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 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 qualitative 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.
	The Company conducted a qualitative assessment of the fair value of its three reporting units as of September 30, 2013 based in part on the demonstrated historical trend of the fair values of the Company’s reporting units substantially exceeding their carrying values and the Company's recent financial performance. Among the factors included in the Company’s qualitative assessment were general economic conditions and the competitive environment; actual and projected reporting unit financial performance; forward-looking business measurements; and external market assessments. Based on the results of the qualitative assessment, the Company believes the fair values of its reporting units continue to substantially exceed their respective carrying values.
	The following table presents changes to the carrying amount of goodwill by reporting unit during the two year period ended December 31, 2013 (in thousands):
		Research				Consulting				Events				Total
	Balance, December 31, 2011 (1)	$	366,980			$	99,677			$	41,893			$	508,550
	Addition due to acquisition (2)	7,455				—				—				7,455
	Foreign currency translation adjustments	2,790				672				39				3,501
	Balance, December 31, 2012	$	377,225			$	100,349			$	41,932			$	519,506
	Foreign currency translation adjustments	(657		)		328				26				(303		)
	Balance, December 31, 2013	$	376,568			$	100,677			$	41,958			$	519,203
	-1	The Company does not have an accumulated goodwill impairment loss.
	-2	The additions are from the Company's acquisition of Ideas International. See Acquisitions above for additional information.
Impairment of long-lived and intangible assets	'
	Impairment of long-lived and intangible assets. The Company reviews its long-lived and intangible assets other than goodwill 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’s policy regarding long-lived assets and intangible assets other than goodwill is to evaluate the recoverability of these assets by determining whether the balance can be recovered through undiscounted future operating cash flows. Should 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 material impairment charges for long-lived and intangible assets during the three year period ended December 31, 2013.
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 715. The Company determines the periodic pension expense and related liabilities for these plans through actuarial assumptions and valuations. The Company recognized $3.8 million, $2.6 million, and $2.7 million of expense for these plans in 2013, 2012, and 2011, respectively. The Company classifies pension expense in SG&A in the Consolidated Statements of Operations.
Debt	'
	Debt. The Company presents amounts borrowed in the Consolidated Balance Sheets at amortized cost. Accrued interest on amounts borrowed is classified in Interest expense in the Consolidated Statements of Operations. The Company had $205.0 million of debt outstanding at both December 31, 2013 and 2012 (see Note 5—Debt for additional information).
Foreign currency exposure	'
	Foreign currency exposure. All assets and liabilities of foreign subsidiaries are translated into U.S. dollars at exchange rates in effect at the balance sheet date. Income and expense items are translated at average exchange rates for the year. The resulting translation adjustments are recorded as foreign currency translation adjustments, a component of Accumulated other comprehensive income, net within the Stockholders’ equity section of the Consolidated Balance Sheets.
	Currency transaction gains or losses arising from transactions denominated in currencies other than the functional currency of a subsidiary are recognized in results of operations in Other expense, net within the Consolidated Statements of Operations. Net currency transaction losses were $(0.9) million, $(2.3) million, and $(1.3) million in 2013, 2012, and 2011, 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 expense, net. The net (loss) gain from these contracts was $(0.1) million, $0.6 million, $(1.2) million in 2013, 2012, and 2011, respectively.
Comprehensive income	'
	Comprehensive income. The Company reports comprehensive income in a separate statement termed the Consolidated Statements of Comprehensive Income, which is included herein. The additional required comprehensive income disclosures are included in Note 2 — Comprehensive Income.
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. The Company’s fair value disclosures are included in Note 12 — Fair Value Disclosures.
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, accounts receivable, interest rate swaps, and a pension reinsurance asset. The majority of the Company’s cash equivalent investments and its interest rate swap contract are with investment grade commercial banks that are participants in the Company’s credit facility. Accounts 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, 2013.
Stock repurchase programs	'
	Stock repurchase programs. The Company records the cost to repurchase its own common shares to treasury stock. During 2013, 2012 and 2011, the Company recorded $196.7 million, $111.3 million, and $212.0 million, respectively, of stock repurchases (see Note 7 — Stockholders’ Equity). Shares repurchased by the Company are added to treasury shares and are not retired.
Adoption of new accounting rules	'
	Adoption of new accounting rules. The Company adopted new accounting rules in the year ended December 31, 2013 related to accumulated other comprehensive income (see Note 2 - Comprehensive Income) and balance sheet offsetting of receivables and payables arising from derivative contracts (see Note 11 - Derivatives and Hedging). The adoption of these new rules resulted in additional disclosure only.
Recent accounting developments	'
	Recent accounting developments. Accounting rules that have been issued by the FASB that have not yet become effective and that may impact the Company’s consolidated financial statements or related disclosures in future periods are described below:
	In July 2013, the FASB issued ASU No. 2013-11, "Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists" ("ASU 2013-11"). ASU 2013-11 addresses the balance sheet presentation of an unrecognized tax benefit when a net operating loss carryforward, a similar tax loss, or a tax credit carryforward exists. ASU 2013-11 requires that an unrecognized tax benefit, or a portion of an unrecognized tax benefit, should be presented in the financial statements as a reduction to a deferred tax asset for a net operating loss carryforward, a similar tax loss, or a tax credit carryforward. ASU No. 2013-11 is effective for the Company’s fiscal quarter ending March 31, 2014 and impacts balance sheet presentation only. The Company believes the balance sheet impact will not be material.
	In March 2013, the FASB issued ASU No. 2013-05, Parent’s Accounting for the Cumulative Translation Adjustment upon Derecognition of Certain Subsidiaries or Groups of Assets within a Foreign Entity or of an Investment in a Foreign Entity. ASU No. 2013-05 provides updated guidance to resolve diversity in practice concerning the release of the cumulative foreign currency translation adjustment into net income when a parent sells a part or all of its investment in a foreign entity or no longer holds a controlling financial interest in a subsidiary or group of assets within a foreign entity. When a company ceases to have a controlling financial interest, the company should recognize any related cumulative translation adjustment into net income only if the sale or transfer results in the complete or substantially complete liquidation of the foreign entity in which the subsidiary had resided. Upon a partial sale, the company should release into earnings a pro rata portion of the cumulative translation adjustment. ASU No. 2013-05 is effective for the Company’s fiscal quarter ending March 31, 2014. The guidance in ASU 2013-05 will only impact the Company's financial statements upon the occurrence of a transaction within its scope.

Business_and_Significant_Accou2

Business and Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2013
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)		2013				2012
	Computer equipment and software		7-Feb		$	136,640			$	135,167
	Furniture and equipment		8-Mar		34,024				29,907
	Leasehold improvements		15-Feb		70,261				64,346
					$	240,925			$	229,420
	Less — accumulated depreciation and amortization				(149,166		)		(140,331		)
	Property, equipment, and leasehold improvements, net				$	91,759			$	89,089
Schedule of Changes in Intangible Assets Subject to Amortization	'
	Changes in intangible assets subject to amortization during the two year period ended December 31, 2013 are as follows (in thousands):
	31-Dec-13		Trade				Customer				Content				Software			Total
			Name				Relationships
	Gross cost, December 31, 2012		$	6,019			$	10,562			$	3,447			$	2,124		$	22,152
	Foreign currency translation impact		4				(416		)		49				19			(344		)
	Gross cost		6,023				10,146				3,496				2,143			21,808
	Accumulated amortization (1), (2)		(4,817		)		(8,372		)		(1,388		)		(1,124		)	(15,701		)
	Balance, December 31, 2013		$	1,206			$	1,774			$	2,108			$	1,019		$	6,107
	31-Dec-12		Trade				Customer				Content				Software			Total
			Name				Relationships
	Gross cost, December 31, 2011		$	5,758			$	7,210			$	—			$	—		$	12,968
	Additions due to acquisition (3)		240				3,170				3,170				1,955			8,535
	Foreign currency translation impact		21				182				277				169			649
	Gross cost		6,019				10,562				3,447				2,124			22,152
	Accumulated amortization (1), (2)		(3,531		)		(5,896		)		(497		)		(407		)	(10,331		)
	Balance, December 31, 2012		$	2,488			$	4,666			$	2,950			$	1,717		$	11,821
	-1	Intangible assets are amortized against earnings over the following periods: Trade name— 2 to 5 years; Customer relationships—4 years; Content—4 years; Software—3 years.
	-2	Aggregate amortization expense related to intangible assets was $5.4 million, $4.4 million, and $6.5 million in 2013, 2012, and 2011, respectively.
	-3	The additions are from the Company's acquisition of Ideas International. See Acquisitions above for additional information.
Schedule of Estimated Future Amortization Expense by Year From Amortizable Intangibles	'
	The estimated future amortization expense by year from amortizable intangibles is as follows (in thousands):
	2014	$	3,530
	2015	1,915
	2016	662
		$	6,107
Schedule of Changes to The Carrying Amount of Goodwill by Reporting Unit	'
	The following table presents changes to the carrying amount of goodwill by reporting unit during the two year period ended December 31, 2013 (in thousands):
		Research				Consulting				Events				Total
	Balance, December 31, 2011 (1)	$	366,980			$	99,677			$	41,893			$	508,550
	Addition due to acquisition (2)	7,455				—				—				7,455
	Foreign currency translation adjustments	2,790				672				39				3,501
	Balance, December 31, 2012	$	377,225			$	100,349			$	41,932			$	519,506
	Foreign currency translation adjustments	(657		)		328				26				(303		)
	Balance, December 31, 2013	$	376,568			$	100,677			$	41,958			$	519,203
	-1	The Company does not have an accumulated goodwill impairment loss.
	-2	The additions are from the Company's acquisition of Ideas International. See Acquisitions above for additional information

Comprehensive_Income_Tables

Comprehensive Income (Tables)	12 Months Ended
	Dec. 31, 2013
Equity [Abstract]	'
Schedule of Changes in AOCI by Component	'
	The information required by ASU 2013-2 for the year ended December 31, 2013 is presented in the following table, net of tax (in thousands) (1):
		Interest Rate Swap			Defined Benefit Pension Plans			Foreign Currency Translation Adjustments		Total
	Balance - December 31, 2012	$	(6,010	)	$	(1,578	)	$	13,556	$	5,968
	Changes during the period:
	Change in AOCI before reclassifications to income	(297		)	(257		)	503		(51		)
	Reclassifications from AOCI to income during the period (2), (3)	2,404			24			—		2,428
	Other comprehensive income (loss) for the period	2,107			(233		)	503		2,377
	Balance - December 31, 2013	$	(3,903	)	$	(1,811	)	$	14,059	$	8,345
	-1	Amounts in parentheses represent deferred losses.
	-2	The interest rate swap is accounted for as a cash flow hedge. The reclassified amount resulted in additional expense for the period which was recorded in Interest expense in the Consolidated Statements of Operations and is net of $1.6 million of related tax benefit reflected in the Provision for income taxes. See Note 11 - Derivatives and Hedging for additional information regarding the swap and the Company's hedging activities.
	-3	The pension reclassification amount was recorded in SGA expense in the Consolidated Statements of Operations and had an immaterial tax effect. See Note 13 - Employee Benefits for additional information regarding the Company's defined benefit pension plans.

Other_Assets_Tables

Other Assets (Tables)	12 Months Ended
	Dec. 31, 2013
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]	'
Schedule of Other Assets	'
	Other assets consist of the following (in thousands):
		December 31,
		2013		2012
	Security deposits	$	5,505	$	7,740
	Debt issuance costs	4,878		2,768
	Benefit plan-related assets	42,367		37,016
	Non-current deferred tax assets	24,371		22,527
	Other	4,510		3,344
	Total other assets	$	81,631	$	73,395

Accounts_Payable_Accrued_and_O1

Accounts Payable, Accrued, and Other Liabilities (Tables)	12 Months Ended
	Dec. 31, 2013
Payables and Accruals [Abstract]	'
Schedule of Accounts Payable and Accrued Liabilities	'
	Accounts payable and accrued liabilities consist of the following (in thousands):
		December 31,
		2013		2012
	Accounts payable	$	17,671	$	27,344
	Payroll, employee benefits, severance	83,224		71,892
	Bonus payable	75,758		68,776
	Commissions payable	57,078		49,128
	Taxes payable	14,392		18,897
	Rent and other facilities costs	3,903		4,310
	Professional, consulting, audit fees	9,159		8,355
	Events fulfillment liabilities	6,600		4,209
	Other accrued liabilities	57,274		34,852
	Total accounts payable and accrued liabilities	$	325,059	$	287,763
Schedule of Other Liabilities	'
	Other liabilities consist of the following (in thousands):
		December 31,
		2013		2012
	Non-current deferred revenue	$	8,959	$	5,508
	Interest rate swap liability	6,505		10,017
	Long-term taxes payable	9,590		16,760
	Deferred rent (1)	18,127		19,586
	Benefit plan-related liabilities	58,000		54,779
	Other	24,912		22,954
	Total other liabilities	$	126,093	$	129,604
	-1	Represents the remaining unamortized long-term deferred rent on the $25.0 million tenant improvement allowance on the Company’s Stamford headquarters facility. See Note 1 — Business and Significant Accounting Policies above for additional information.

Debt_Tables

Debt (Tables)	12 Months Ended
	Dec. 31, 2013
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:	2013		2012
	Term loan (1)	$	144,375	$	150,000
	Revolver (1), (2)	55,625		50,000
	Other (3)	5,000		5,000
	Total (4)	$	205,000	$	205,000
	-1	The contractual annual interest rate as of December 31, 2013 on both the term loan and the revolver was 1.62%, which consisted of a floating Eurodollar base rate of 0.24% plus a margin of 1.38%. However, the Company has an interest rate swap contract which converts the floating Eurodollar base rate to a 2.26% fixed base rate on the first $200.0 million of Company borrowings (see below). As a result, the Company’s effective annual interest rate on the $200.0 million of outstanding debt under the 2013 Credit Facility as of December 31, 2013, including the margin, was 3.64%.
	-2	The Company had $541.1 million of available borrowing capacity on the revolver (not including the expansion feature) as of December 31, 2013.
	-3	Consists of a $5.0 million State of Connecticut economic development loan with a 3.0% fixed rate of interest. The loan was originated in 2012 and has a 10 year maturity. Principal payments are deferred for the first five years and the loan may be repaid at any point by the Company without penalty. The loan has a principal forgiveness provision in which up to $2.5 million of the loan may be forgiven if the Company meets certain employment targets during the first five years of the loan.

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2013
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, 2013 were as follows (in thousands):
	Year ended December 31,
	2014	$	34,525
	2015	27,720
	2016	20,415
	2017	14,840
	2018	11,145
	Thereafter	82,485
	Total minimum lease payments (1)	$	191,130
	-1	Excludes $1.2 million of future contractual sublease rental income.

Stockholders_Equity_Tables

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2013
Equity [Abstract]	'
Schedule of Transactions Relating to Common Stock	'
	The following table summarizes transactions relating to Common Stock for the three years’ ending December 31, 2013:
		Issued	Treasury
		Shares	Stock
			Shares
	Balance at December 31, 2010	156,234,415	60,245,718
	Issuances under stock plans	—	(3,244,705	)
	Purchases for treasury (1)	—	5,890,238
	Balance at December 31, 2011	156,234,415	62,891,251
	Issuances under stock plans	—	(2,756,389	)
	Purchases for treasury (1)	—	2,738,238
	Balance at December 31, 2012	156,234,415	62,873,100
	Issuances under stock plans	—	(2,037,091	)
	Purchases for treasury (1)	—	3,432,854
	Balance at December 31, 2013	156,234,415	64,268,863
	-1	The total cost of repurchased shares in 2013 was $196.7 million, of which $181.7 million was paid in 2013 and $15.0 million was paid in early 2014. The total cost of repurchased shares in 2012 and 2011 was $111.3 million and $212.0 million respectively.

StockBased_Compensation_Tables

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2013
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:		2013				2012				2011
	Stock appreciation rights		$	5.2			$	6.4			$	4.4
	Common stock equivalents		0.6				0.5				0.5
	Restricted stock units		28.9				29.5				28
	Total (1)		$	34.7			$	36.4			$	32.9
	-1	Includes charges of $12.5 million, $5.1 million, and $3.1 million in 2013, 2012 and 2011, respectively, for awards to retirement-eligible employees since these awards vest on an accelerated basis
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 (in millions):
	Amount recorded in:		2013				2012				2011
	Costs of services and product development		$	15.3			$	15.3			$	14.8
	Selling, general, and administrative		19.4				21.1				18.1
	Total		$	34.7			$	36.4			$	32.9
Schedule of Fair Value Assumptions of SARS	'
	The fair value of the SARs granted was estimated on the date of grant using the Black-Scholes-Merton valuation model with the following weighted-average assumptions for the years ended December 31:
		2013			2012			2011
	Expected dividend yield (1)	—	%		—	%		—	%
	Expected stock price volatility (2)	35	%		40	%		38	%
	Risk-free interest rate (3)	0.8	%		0.8	%		2.2	%
	Expected life in years (4)	4.49			4.61			4.75
	-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, 2013:
		SARs in			Per Share				Per Share				Weighted-
		millions			Weighted-				Weighted-				Average
					Average				Average				Remaining
					Exercise Price				Grant Date				Contractual
									Fair Value				Term
	Outstanding at December 31, 2012	2			$	24.59			$	9.04			4.10 years
	Granted	0.4			49.37				14.88				6.12 years
	Forfeited	—			—				—				—
	Exercised	(0.8	)		15.99				6.3				na
	Outstanding at December 31, 2013 (1), (2)	1.6			$	34.14			$	11.63			4.34 years
	Vested and exercisable at December 31, 2013 (1)	0.6			$	25.63			$	9.41			3.33 years
	na =ot applicable
	-1	At December 31, 2013, 1.0 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, 2013, SARs outstanding had an intrinsic value of $59.1 million. SARs vested and exercisable had an intrinsic value of $29.0 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, 2013:
		Restricted			Per Share
		Stock Units			Weighted
		(RSUs)			Average
		(in millions)			Grant Date
					Fair Value
	Outstanding at December 31, 2012	2.5			$	27.95
	Granted (1)	0.7			49.86
	Vested and released	(1.4	)		22.47
	Forfeited	—			—
	Outstanding at December 31, 2013 (2), (3)	1.8			$	38.83
	-1	The 0.7 million RSUs granted in 2013 consisted of 0.3 million performance-based RSUs awarded to executives and 0.4 million service-based RSUs awarded to non-executive employees and certain board members. The target number of performance-based RSUs awarded to executives in 2013 was 0.2 million, while the final amount could range from 0% to 200% of the target amount. The final amount was dependent on the increase in the Company's subscription-based contract value ("CV') for the year as measured on December 31, 2013. The actual CV increase achieved for 2013 was 117.1%, which resulted in the grant of 0.3 million performance-based RSUs.
	-2	The Company expects that substantially all of the outstanding awards at December 31, 2013 will vest in future periods.
	-3	The weighted-average remaining contractual term of the outstanding RSUs is approximately 1 year.
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, 2013:
		Common Stock			Per Share
		Equivalents			Weighted
		(CSEs)			Average
					Grant Date
					Fair Value
	Outstanding at December 31, 2012	100,545			$	16.89
	Granted	9,718			60.34
	Converted to common shares	(7,784	)		60.31
	Outstanding at December 31, 2013	102,479			$	17.71

Computation_of_Earnings_Per_Sh1

Computation of Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2013
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):
		2013		2012		2011
	Numerator:
	Net income used for calculating basic and diluted earnings per common share	$	182,801	$	165,903	$	136,902
	Denominator: (1)
	Weighted average number of common shares used in the calculation of basic earnings per share	93,015		93,444		96,019
	Common share equivalents associated with stock-based compensation plans	1,815		2,398		2,827
	Shares used in the calculation of diluted earnings per share	94,830		95,842		98,846
	Earnings per share:
	Basic	$	1.97	$	1.78	$	1.43
	Diluted	$	1.93	$	1.73	$	1.39
	-1	The Company repurchased 3.4 million, 2.7 million, and 5.9 million shares of its Common Stock in 2013, 2012, and 2011, respectively.
Schedule of Share Equivalents Excluded from Computation of Diluted 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 antidilutive. During periods with net income, these common share equivalents were antidilutive because their exercise price was greater than the average market value of a share of Common Stock during the period.
		2013		2012		2011
	Antidilutive common share equivalents as of December 31 (in millions):	0.3		0.7		0.5
	Average market price per share of Common Stock during the year	$	57.5	$	43.8	$	37.53

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2013
Income Tax Disclosure [Abstract]	'
Schedule of Components of Income before Income Taxes	'
	Following is a summary of the components of income before income taxes for the years ended December 31 (in thousands):
		2013				2012				2011
	U.S.	$	186,330			$	150,023			$	124,915
	Non-U.S.	80,109				85,573				77,269
	Income before income taxes	$	266,439			$	235,596			$	202,184
Schedule of Components of Income Tax	'
	The expense for income taxes on the above income consists of the following components (in thousands):
		2013				2012				2011
	Current tax expense:
	U.S. federal	$	20,111			$	25,290			$	23,327
	State and local	4,943				2,508				4,236
	Foreign	17,460				18,889				13,845
	Total current	42,514				46,687				41,408
	Deferred tax (benefit) expense:
	U.S. federal	18,806				8,494				(5,192		)
	State and local	2,742				(753		)		1,269
	Foreign	(4,688		)		(8,080		)		(1,434		)
	Total deferred	16,860				(339		)		(5,357		)
	Total current and deferred	59,374				46,348				36,051
	Benefit (expense) relating to interest rate swap used to increase (decrease) equity	(1,405		)		51				3,134
	Benefit from stock transactions with employees used to increase equity	25,373				21,304				25,812
	Benefit (expense) relating to defined-benefit pension adjustments used to increase (decrease) equity	482				1,926				285
	Benefit (expense) of acquired tax assets (liabilities) used to decrease (increase) goodwill	(186		)		64				—
	Total tax expense	$	83,638			$	69,693			$	65,282
Schedule of Deferred Tax Assets and Liabilities	'
	Current and long-term deferred tax assets and liabilities are comprised of the following (in thousands):
		December 31,
		2013				2012
	Expense accruals	$	56,787			$	49,404
	Loss and credit carryforwards	17,648				22,433
	Assets relating to equity compensation	19,773				18,878
	Other assets	1,306				7,613
	Gross deferred tax asset	95,514				98,328
	Depreciation	(12,067		)		(8,995		)
	Intangible assets	(25,338		)		(23,129		)
	Prepaid expenses	(22,517		)		(10,500		)
	Gross deferred tax liability	(59,922		)		(42,624		)
	Valuation allowance	(617		)		(1,943		)
	Net deferred tax asset	$	34,975			$	53,761
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:
		2013			2012			2011
	Statutory tax rate	35	%		35	%		35	%
	State income taxes, net of federal benefit	3.2			1.8			3.8
	Foreign income taxed at different rates	(5.6	)		(6.4	)		(5.9	)
	Foreign tax credits	—			(1.0	)		(2.3	)
	Record (release) reserve for tax contingencies	0.3			0.7			3.1
	Record (release) valuation allowance	(0.5	)		—			(0.4	)
	Other items, net	(1.0	)		(0.5	)		(1.0	)
	Effective tax rate	31.4	%		29.6	%		32.3	%
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 ending December 31 (in thousands):
		2013				2012
	Beginning balance	$	17,552			$	18,345
	Additions based on tax positions related to the current year	4,237				4,301
	Additions for tax positions of prior years	827				105
	Reductions for tax positions of prior years	(1,973		)		(3,427		)
	Reductions for expiration of statutes	(3,860		)		(296		)
	Settlements	(1,575		)		(1,372		)
	Change in foreign currency exchange rates	(720		)		(104		)
	Ending balance	$	14,488			$	17,552

Derivatives_and_Hedging_Tables

Derivatives and Hedging (Tables)	12 Months Ended
	Dec. 31, 2013
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 (in thousands, except for number of outstanding contracts):
	December 31, 2013
	Derivative Contract Type		Number of		Contract				Fair Value			Balance Sheet	OCI
			Outstanding		Notional				Asset			Line Item	Unrealized
			Contracts		Amount				(Liability) (3)				(Loss), Net
													Of Tax
	Interest rate swap (1)		1		$	200,000			$	(6,505	)	Other liabilities	$	(3,903	)
	Foreign currency forwards (2)		89		61,325				(60		)	Other current liabilities	—
	Total		90		$	261,325			$	(6,565	)		$	(3,903	)
	December 31, 2012
	Derivative Contract Type		Number of		Contract				Fair Value			Balance Sheet	OCI
			Outstanding		Notional				Asset			Line Item	Unrealized
			Contracts		Amount				(Liability) (3)				(Loss), Net
													Of Tax
	Interest rate swap (1)		1		$	200,000			$	(10,000	)	Other liabilities	$	(6,010	)
	Foreign currency forwards (2)		68		76,100				4			Other current assets	—
	Total		69		$	276,100			$	(9,996	)		$	(6,010	)
	-1	The swap is designated as a cash flow hedge of the forecasted interest payments on borrowings. As a result, changes in the fair value of this swap are deferred and are recorded in OCI, 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 offset the economic effects of these foreign currency transaction risks. 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. Substantially all of the outstanding contracts at December 31, 2013 matured by the end of January 2014.
	-3	See Note 12 — Fair Value Disclosures below 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 thousands):
	Amount recorded in:		2013			2012				2011
	Interest expense (1)		$	4		$	3.6			$	4.1
	Other expense, net (2)		0.1			(0.6		)		1.2
	Total expense		$	4.1		$	3			$	5.3
	-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, 2013
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):
	Description:		Fair Value December 31, 2013		Fair Value December 31, 2012
	Assets:
	Deferred compensation plan assets (1)		$	32,555	$	27,795
	Foreign currency forward contracts (2)		116		204
			$	32,671	$	27,999
	Liabilities:
	Deferred compensation plan liabilities (1)		$	36,410	$	31,260
	Foreign currency forward contracts (2)		176		200
	Interest rate swap contracts (3)		6,505		10,000
			$	43,091	$	41,460
	-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 plan’s 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 $7.8 million and $8.2 million as of December 31, 2013 and 2012, 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 $24.8 million and $19.6 million at December 31, 2013 and 2012, respectively. The related deferred compensation plan liabilities are recorded at the amount needed to settle the liability, which approximates fair value, and is based on 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 an interest rate swap contract which hedges the risk from variability of interest rates on its borrowings (see Note 11 — Derivatives and Hedging). The fair value of the swap is based on a mark-to-market valuation prepared by a third-party broker. Valuation is 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 valuation 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, 2013
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):
		2013				2012				2011
	Service cost (1)	$	2,545			$	1,775			$	1,890
	Interest cost	1,075				980				1,010
	Expected return on plan assets	(340		)		(115		)		(125		)
	Recognition of actuarial loss (gain)	30				(215		)		(135		)
	Recognition of termination benefits	455				175				65
	Total defined benefit pension expense (2)	$	3,765			$	2,600			$	2,705
	-1	The higher 2013 service cost was primarily due to additional employees covered under the plans.
	-2	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 assumptions used in the computation of pension expense for the years ended December 31:
		2013			2012			2011
	Weighted-average discount rate (1)	3.35	%		3.2	%		4.4	%
	Average compensation increase	2.7	%		2.7	%		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):
		2013				2012				2011
	Projected benefit obligation at beginning of year	$	31,605			$	21,160			$	19,730
	Service cost	2,545				1,775				1,890
	Interest cost	1,075				980				1,010
	Actuarial loss (gain) due to assumption changes and plan experience (1)	625				6,265				(948		)
	Additions and contractual termination benefits	460				1,925				—
	Benefits paid (2)	(1,255		)		(680		)		(390		)
	Foreign currency impact	(470		)		180				(132		)
	Projected benefit obligation at end of year (3)	$	34,585			$	31,605			$	21,160
	-1	The 2012 actuarial loss was primarily due to a decline in the weighted-average discount rate.
	-2	The Company projects the following approximate amounts will be paid in future years to plan participants: $0.6 million in 2014; $1.8 million in 2015; $0.7 million in 2016; $1.1 million in 2017; $1.0 million in 2018; and $7.5 million in the five years thereafter.
	-3	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:
		2013				2012				2011
	Projected benefit obligation	$	34,585			$	31,605			$	21,160
	Plan assets at fair value (1)	(13,870		)		(8,885		)		(2,480		)
	Funded status – shortfall (2)	$	20,715			$	22,720			$	18,680
	Amounts recorded in the Consolidated Balance Sheets for the plans:
	Other liabilities — accrued pension obligation (2)	$	20,715			$	22,720			$	18,680
	Stockholders’ equity — deferred actuarial (loss) gain (3)	$	(1,811	)		$	(1,578	)		$	2,488
	-1	The 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 820, and the Company considers the overall portfolio of these assets to be of low-to-medium investment risk. The Company projects a future long-term rate of return on these plan assets of 3.8%, 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, 2013, the Company contributed $5.9 million to these plans, and benefits paid to participants were $1.3 million.
	In addition to the plan assets held with third-party trustees, the Company also maintains a reinsurance asset arrangement with a large international insurance company. The reinsurance asset is an asset of the Company whose purpose is to provide funding for benefit payments for one of the plans. At December 31, 2013, the reinsurance asset was carried on the Company’s Consolidated Balance Sheets at its cash surrender value of $9.3 million and is classified in Other Assets. 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 820.
	-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, 2013, is recorded in Accumulated Other Comprehensive Income (“AOCI”) and will be reclassified out of AOCI and recognized as pension expense over approximately 15 years, subject to certain limitations set forth in FASB ASC Topic 715. The impact of this amortization on the periodic pension expense in 2014 is projected to be less than $0.1 million. The actual amortization of deferred actuarial losses (gains) from AOCI to pension expense was less than $0.1 million in 2013, $(0.2) million in 2012, and $(0.1) million in 2011.

Segment_Information_Tables

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2013
Segment Reporting [Abstract]	'
Schedule of Segment Reporting Information by Segment	'
	The following tables present operating information about the Company’s reportable segments for the years ended December 31 (in thousands):
		Research			Consulting			Events			Consolidated
	2013
	Revenues	$	1,271,011		$	314,257		$	198,945		$	1,784,213
	Gross contribution	879,384			107,565			91,216			1,078,165
	Corporate and other expenses										(802,673		)
	Operating income										$	275,492
		Research			Consulting			Events			Consolidated
	2012
	Revenues	$	1,137,147		$	304,893		$	173,768		$	1,615,808
	Gross contribution	774,342			109,253			80,119			963,714
	Corporate and other expenses										(718,007		)
	Operating income										$	245,707
		Research			Consulting			Events			Consolidated
	2011
	Revenues	$	1,012,062		$	308,047		$	148,479		$	1,468,588
	Gross contribution	682,136			114,838			66,265			863,239
	Corporate and other expenses										(649,177		)
	Operating income										$	214,062
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,
			2013			2012			2011
	Total segment gross contribution		$	1,078,165		$	963,714		$	863,239
	Costs and expenses:
	Cost of services and product development - unallocated (1)		7,436			6,973			3,406
	Selling, general and administrative		760,458			678,843			613,707
	Depreciation and amortization		34,442			29,771			32,064
	Acquisition and integration charges		337			2,420			—
	Operating income		275,492			245,707			214,062
	Interest expense and other		9,053			10,111			11,878
	Provision for income taxes		83,638			69,693			65,282
	Net income		$	182,801		$	165,903		$	136,902
	-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):
		2013			2012			2011
	Revenues:
	United States and Canada	$	1,049,734		$	947,075		$	861,481
	Europe, Middle East and Africa	508,755			458,675			437,194
	Other International	225,724			210,058			169,913
	Total revenues	$	1,784,213		$	1,615,808		$	1,468,588
	Long-lived assets: (1)
	United States and Canada (2)	$	123,877		$	114,557		$	85,194
	Europe, Middle East and Africa	34,363			30,967			23,673
	Other International	13,936			16,956			10,754
	Total long-lived assets	$	172,176		$	162,480		$	119,621
	-1	Excludes goodwill and other intangible assets.
	-2	The United States and Canada balances include costs capitalized in connection with the renovation of the Company’s Stamford headquarters facility (see Note 1 — Business and Significant Accounting Policies for additional description). These capitalized costs amounted to $7.7 million in 2013, $17.0 million in 2012, and $9.5 million in 2011

Valuation_and_Qualifying_Accou1

Valuation and Qualifying Accounts (Tables)	12 Months Ended
	Dec. 31, 2013
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		Additions		Additions		Deductions			Balance
		Beginning		Charged to		Charged		from			at End
		of Year		Expense		Against		Reserve			of Year
						Revenues
	2013:00:00
	Allowance for doubtful accounts and returns and allowances	$	6,400	$	2,350	$	5,050	$	(6,800	)	$	7,000
	2012:00:00
	Allowance for doubtful accounts and returns and allowances	$	7,260	$	1,930	$	1,860	$	(4,650	)	$	6,400
	2011:00:00
	Allowance for doubtful accounts and returns and allowances	$	7,200	$	930	$	4,390	$	(5,260	)	$	7,260

Business_and_Significant_Accou3

Business and Significant Accounting Policies (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
	building
	segment
	sqft
Business and Significant Accounting Policies [Line Items]	'		'		'
Number of reportable segments	3		'		'
Goodwill acquired	$7,455,000	[1]	'		'
Amortizable intangible assets acquired	'		8,535,000	[1]	'
Acquisition and integration charges	337,000		2,420,000		0
Unbilled fees receivable	37,000,000		34,000,000		'
Stock-based compensation expense	34,735,000		36,378,000		32,865,000
Rent expense	30,800,000		30,300,000		26,200,000
Depreciation expense	28,996,000		25,369,000		25,539,000
Net capitalized development costs for internal use software	14,100,000		14,400,000		'
Amortization of capitalized internal software development costs	8,200,000		7,400,000		7,800,000
Leased office space	213,000		'		'
Number of leased properties	3		'		'
Deferred rent credit	25,000,000		'		'
Payments for capital improvements	36,498,000		44,337,000		41,954,000
Leasehold improvements	3,000,000		13,000,000		9,000,000
Amortization of intangibles	5,446,000		4,402,000		6,525,000
Pension expense	3,800,000		2,600,000		2,700,000
Outstanding debt	205,000,000		205,000,000		'
Foreign currency transaction gain (loss	-900,000		-2,300,000		-1,300,000
Derivative instruments, gain (loss) recognized in income, net	4,100		3,000		5,300
Cost of repurchased stock	196,696,000		111,304,000		211,986,000
Payments for purchases of treasury stock	181,736,000		111,304,000		211,986,000
Foreign currency exchange contracts	'		'		'
Business and Significant Accounting Policies [Line Items]	'		'		'
Derivative instruments, gain (loss) recognized in income, net	-100,000		600,000		-1,200,000
Trade Name	'		'		'
Business and Significant Accounting Policies [Line Items]	'		'		'
Amortizable intangible assets acquired	'		240,000	[1]	'
Intangible assets amortization period, minimum	'2 years		'		'
Intangible assets amortization period, maximum	'5 years		'		'
Customer Relationships	'		'		'
Business and Significant Accounting Policies [Line Items]	'		'		'
Amortizable intangible assets acquired	'		3,170,000	[1]	'
Amortization period	'4 years		'		'
Content	'		'		'
Business and Significant Accounting Policies [Line Items]	'		'		'
Amortizable intangible assets acquired	'		3,170,000	[1]	'
Amortization period	'4 years		'		'
Software	'		'		'
Business and Significant Accounting Policies [Line Items]	'		'		'
Amortizable intangible assets acquired	'		1,955,000	[1]	'
Amortization period	'3 years		'		'
Stamford	'		'		'
Business and Significant Accounting Policies [Line Items]	'		'		'
Payments for capital improvements	7,700,000		17,000,000		9,500,000
Ideas International Limited	'		'		'
Business and Significant Accounting Policies [Line Items]	'		'		'
Percentage of outstanding shares acquired	'		100.00%		'
Aggregate cash consideration paid for acquisition	'		18,800,000		'
Goodwill acquired	'		'		7,500,000	[1]
Amortizable intangible assets acquired	'		8,500,000	[1]	'
Acquisition and integration charges	$300,000		$2,400,000		'
[1]	The additions are from the Company's acquisition of Ideas International. See Acquisitions above for additional information.

Business_and_Significant_Accou4

Business and Significant Accounting Policies (Detail) - Property, Equipment and Leasehold Improvements, Less Accumulated Depreciation and Amortization (USD $)

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2013

In Thousands, unless otherwise specified

Computer equipment and software

Computer equipment and software

Computer equipment and software

Computer equipment and software

Furniture and equipment

Furniture and equipment

Furniture and equipment

Furniture and equipment

Leasehold improvements

Leasehold improvements

Leasehold improvements

Leasehold improvements

Minimum

Maximum

Minimum

Maximum

Minimum

Maximum

Property, Plant and Equipment [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Useful Life

'

'

'

'

'2 years

'7 years

'

'

'3 years

'8 years

'

'

'2 years

'15 years

Property, equipment and Leasehold Improvements, gross

$240,925

$229,420

$136,640

$135,167

'

'

$34,024

$29,907

'

'

$70,261

$64,346

'

'

Less — accumulated depreciation and amortization

-149,166

-140,331

'

'

'

'

'

'

'

'

'

'

'

'

Property, equipment and leasehold improvements, net

$91,759

$89,089

'

'

'

'

'

'

'

'

'

'

'

'

Business_and_Significant_Accou5

Business and Significant Accounting Policies (Detail) - Intangible Assets Subject to Amortization (USD $)	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
In Thousands, unless otherwise specified
Finite-Lived Intangible Assets [Line Items]	'		'		'
Gross cost	'		$22,152		$12,968
Additions due to acquisition	'		8,535	[1]	'
Foreign currency translation impact	-344		649		'
Gross cost after foreign currency translation adjustment	21,808		22,152		'
Accumulated amortization	-15,701	[2],[3]	-10,331	[2],[3]	'
Balance	6,107		11,821		'
Trade Name	'		'		'
Finite-Lived Intangible Assets [Line Items]	'		'		'
Gross cost	'		6,019		5,758
Additions due to acquisition	'		240	[1]	'
Foreign currency translation impact	4		21		'
Gross cost after foreign currency translation adjustment	6,023		6,019		'
Accumulated amortization	-4,817	[2],[3]	-3,531	[2],[3]	'
Balance	1,206		2,488		'
Customer Relationships	'		'		'
Finite-Lived Intangible Assets [Line Items]	'		'		'
Gross cost	'		10,562		7,210
Additions due to acquisition	'		3,170	[1]	'
Foreign currency translation impact	-416		182		'
Gross cost after foreign currency translation adjustment	10,146		10,562		'
Accumulated amortization	-8,372	[2],[3]	-5,896	[2],[3]	'
Balance	1,774		4,666		'
Content	'		'		'
Finite-Lived Intangible Assets [Line Items]	'		'		'
Gross cost	'		3,447		0
Additions due to acquisition	'		3,170	[1]	'
Foreign currency translation impact	49		277		'
Gross cost after foreign currency translation adjustment	3,496		3,447		'
Accumulated amortization	-1,388	[2],[3]	-497	[2],[3]	'
Balance	2,108		2,950		'
Software	'		'		'
Finite-Lived Intangible Assets [Line Items]	'		'		'
Gross cost	'		2,124		0
Additions due to acquisition	'		1,955	[1]	'
Foreign currency translation impact	19		169		'
Gross cost after foreign currency translation adjustment	2,143		2,124		'
Accumulated amortization	-1,124	[2],[3]	-407	[2],[3]	'
Balance	$1,019		$1,717		'
[1]	The additions are from the Company's acquisition of Ideas International. See Acquisitions above for additional information.
[2]	Intangible assets are amortized against earnings over the following periods: Trade name— 2 to 5 years; Customer relationships—4 years; Content—4 years; Software—3 years.
[3]	Aggregate amortization expense related to intangible assets was $5.4 million, $4.4 million, and $6.5 million in 2013, 2012, and 2011, respectively.

Business_and_Significant_Accou6

Business and Significant Accounting Policies (Detail) - Estimated Future Amortization Expense by Year from Purchased Intangibles (USD $)	Dec. 31, 2013
In Thousands, unless otherwise specified
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]	'
2014	$3,530
2015	1,915
2016	662
Total	$6,107

Business_and_Significant_Accou7

Business and Significant Accounting Policies (Detail) - Changes to the Carrying Amount of Goodwill by Reporting Unit (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Goodwill [Roll Forward]	'		'		'
Beginning Balance	$519,506		$508,550	[1]	'
Addition due to acquisition	7,455	[2]	'		'
Foreign currency translation adjustments	-303		3,501		'
Ending Balance	519,203		519,506		'
Research	'		'		'
Goodwill [Roll Forward]	'		'		'
Beginning Balance	377,225		366,980	[1]	'
Addition due to acquisition	'		'		7,455	[2]
Foreign currency translation adjustments	-657		2,790		'
Ending Balance	376,568		377,225		366,980	[1]
Consulting	'		'		'
Goodwill [Roll Forward]	'		'		'
Beginning Balance	100,349		99,677	[1]	'
Addition due to acquisition	0	[2]	'		'
Foreign currency translation adjustments	328		672		'
Ending Balance	100,677		100,349		'
Events	'		'		'
Goodwill [Roll Forward]	'		'		'
Beginning Balance	41,932		41,893	[1]	'
Addition due to acquisition	0	[2]	'		'
Foreign currency translation adjustments	26		39		'
Ending Balance	$41,958		$41,932		'
[1]	The Company does not have an accumulated goodwill impairment loss.
[2]	The additions are from the Company's acquisition of Ideas International. See Acquisitions above for additional information.

Comprehensive_Income_Detail_Ch

Comprehensive Income (Detail) - Changes in AOCI by Component (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]	'		'		'
Balance - December 31, 2012	$5,968	[1]	'		'
Changes during the period:	'		'		'
Change in AOCI before reclassifications to income	-51	[1]	'		'
Reclassifications from AOCI to income during the period (2), (3)	2,428	[1],[2],[3]	'		'
Other comprehensive income (loss), net of tax	2,377	[1]	175		-8,845
Balance - December 31, 2013	8,345	[1]	5,968	[1]	'
Interest Rate Swap	'		'		'
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]	'		'		'
Balance - December 31, 2012	-6,010	[1]	'		'
Changes during the period:	'		'		'
Change in AOCI before reclassifications to income	-297	[1]	'		'
Reclassifications from AOCI to income during the period (2), (3)	2,404	[1],[2],[3]	'		'
Other comprehensive income (loss), net of tax	2,107	[1]	'		'
Balance - December 31, 2013	-3,903	[1]	'		'
Defined Benefit Pension Plans	'		'		'
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]	'		'		'
Balance - December 31, 2012	-1,578	[1]	'		'
Changes during the period:	'		'		'
Change in AOCI before reclassifications to income	-257	[1]	'		'
Reclassifications from AOCI to income during the period (2), (3)	24	[1],[2],[3]	'		'
Other comprehensive income (loss), net of tax	-233	[1]	'		'
Balance - December 31, 2013	-1,811	[1]	'		'
Foreign Currency Translation Adjustments	'		'		'
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]	'		'		'
Balance - December 31, 2012	13,556	[1]	'		'
Changes during the period:	'		'		'
Change in AOCI before reclassifications to income	503	[1]	'		'
Reclassifications from AOCI to income during the period (2), (3)	0	[1],[2],[3]	'		'
Other comprehensive income (loss), net of tax	503	[1]	'		'
Balance - December 31, 2013	$14,059	[1]	'		'
[1]	(1)Amounts in parentheses represent deferred losses.
[2]	(2)The interest rate swap is accounted for as a cash flow hedge. The reclassified amount resulted in additional expense for the period which was recorded in Interest expense in the Consolidated Statements of Operations and is net of $1.6 million of related tax benefit reflected in the Provision for income taxes. See Note 11 - Derivatives and Hedging for additional information regarding the swap and the Company's hedging activities.
[3]	The pension reclassification amount was recorded in SGA expense in the Consolidated Statements of Operations and had an immaterial tax effect. See Note 13 - Employee Benefits for additional information regarding the Company's defined benefit pension plans.

Comprehensive_Income_Detail

Comprehensive Income (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2013
Equity [Abstract]	'
Reclassification adjustment on derivatives included in net income, tax benefit	$1.60

Other_Assets_Detail_Compositio

Other Assets (Detail) - Composition of Other Assets (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]	'	'
Security deposits	$5,505	$7,740
Debt issuance costs	4,878	2,768
Benefit plan-related assets	42,367	37,016
Non-current deferred tax assets	24,371	22,527
Other	4,510	3,344
Total other assets	$81,631	$73,395

Accounts_Payable_Accrued_and_O2

Accounts Payable, Accrued, and Other Liabilities (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2013
Payables and Accruals [Abstract]	'
Payments for (proceeds from) tenant allowance	$25

Accounts_Payable_Accrued_and_O3

Accounts Payable, Accrued, and Other Liabilities (Detail) - Accounts Payable and Accrued Liabilities (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Payables and Accruals [Abstract]	'	'
Accounts payable	$17,671	$27,344
Payroll, employee benefits, severance	83,224	71,892
Bonus payable	75,758	68,776
Commissions payable	57,078	49,128
Taxes payable	14,392	18,897
Rent and other facilities costs	3,903	4,310
Professional, consulting, audit fees	9,159	8,355
Events fulfillment liabilities	6,600	4,209
Other accrued liabilities	57,274	34,852
Total accounts payable and accrued liabilities	$325,059	$287,763

Accounts_Payable_Accrued_and_O4

Accounts Payable, Accrued, and Other Liabilities (Detail) - Other Liabilities (USD $)	Dec. 31, 2013		Dec. 31, 2012
In Thousands, unless otherwise specified
Payables and Accruals [Abstract]	'		'
Non-current deferred revenue	$8,959		$5,508
Interest rate swap liability	6,505		10,017
Long-term taxes payable	9,590		16,760
Deferred rent (1)	18,127	[1]	19,586	[1]
Benefit plan-related liabilities	58,000		54,779
Other	24,912		22,954
Total other liabilities	$126,093		$129,604
[1]	Represents the remaining unamortized long-term deferred rent on the $25.0 million tenant improvement allowance on the Company’s Stamford headquarters facility. See Note 1 — Business and Significant Accounting Policies above for additional information.

Debt_Detail

Debt (Detail) (USD $)	12 Months Ended		9 Months Ended			12 Months Ended					12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Sep. 30, 2013	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2013
			Federal Funds rate	Euro Dollar rate	Euro Dollar rate	Revolving credit facility	Refinancing of debt	Term loan	Revolver	Revolver	Connecticut Economic Development Program
					Federal Funds rate			installment		Letter of credit
Debt Instrument [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Debt instrument, maturity duration	'	'	'	'	'	'	'	'5 years	'	'	'
Line of credit facility, maximum borrowing capacity	'	'	'	'	'	'	'	$150,000,000	$600,000,000	$40,000,000	$5,000,000
Line of credit facility, additional borrowing capacity	250,000,000	'	'	'	'	'	'	'	'	'	'
Line of credit facility, frequency of payments in quarterly installments	'	'	'	'	'	'	'	16	'	'	'
Debt issuance cost	'	'	'	'	'	3,600,000	300,000	'	'	'	'
Debt instrument, interest, additional interest above federal fund rate	'	'	0.50%	'	'	'	'	'	'	'	'
Debt instrument, interest, additional interest above Eurodollar rate	1.00%	'	'	'	'	'	'	'	'	'	'
Minimum applicable margin rate	'	'	'	1.25%	0.25%	'	'	'	'	'	'
Maximum applicable margin rate	'	'	'	1.75%	0.75%	'	'	'	'	'	'
Contractual annualized interest rate	1.62%	'	'	'	'	'	'	'	'	'	'
Debt instrument, interest base rate	'	'	'	'	'	'	'	0.24%	'	'	'
Debt instrument, interest, additional interest above base rate	'	'	'	'	'	'	'	1.38%	'	'	'
Derivative, fixed interest rate	2.26%	'	'	'	'	'	'	'	'	'	'
Notional amount of interest rate derivatives	200,000,000	'	'	'	'	'	'	'	'	'	'
Debt instrument, interest rate at period end	3.64%	'	'	'	'	'	'	'	'	'	'
Line of credit facility, remaining borrowing capacity	541,100,000	'	'	'	'	'	'	'	'	'	'
Debt instrument, fixed interest rate	'	'	'	'	'	'	'	'	'	'	3.00%
Debt instrument, maturity period	'	'	'	'	'	'	'	'	'	'	'10 years
Debt instrument, period principal payments are deferred	'	'	'	'	'	'	'	'	'	'	'5 years
Line of credit facility, decrease, forgiveness	'	'	'	'	'	'	'	'	'	'	2,500,000
Debt instrument, forgiveness period under the terms of the loan	'	'	'	'	'	'	'	'	'	'	'5 years
Current portion of long-term debt	68,750,000	90,000,000	'	'	'	'	'	'	'	'	'
Long-term debt	136,250,000	115,000,000	'	'	'	'	'	'	'	'	'
Interest rate derivative hedge, negative fair value	6,500,000	'	'	'	'	'	'	'	'	'	'
Letters of credit outstanding, amount	$9,800,000	'	'	'	'	'	'	'	'	'	'

Debt_Detail_Borrowings

Debt (Detail) - Borrowings (USD $)	Dec. 31, 2013		Dec. 31, 2012
In Thousands, unless otherwise specified
Debt Instrument [Line Items]	'		'
Amount outstanding	$205,000		$205,000
Term loan	'		'
Debt Instrument [Line Items]	'		'
Amount outstanding	144,375	[1]	150,000	[1]
Revolver	'		'
Debt Instrument [Line Items]	'		'
Amount outstanding	55,625	[1],[2]	50,000	[1],[2]
Other	'		'
Debt Instrument [Line Items]	'		'
Amount outstanding	$5,000	[3]	$5,000	[3]
[1]	The contractual annual interest rate as of December 31, 2013 on both the term loan and the revolver was 1.62%, which consisted of a floating Eurodollar base rate of 0.24% plus a margin of 1.38%. However, the Company has an interest rate swap contract which converts the floating Eurodollar base rate to a 2.26% fixed base rate on the first $200.0 million of Company borrowings (see below). As a result, the Company’s effective annual interest rate on the $200.0 million of outstanding debt under the 2013 Credit Facility as of December 31, 2013, including the margin, was 3.64%.
[2]	The Company had $541.1 million of available borrowing capacity on the revolver (not including the expansion feature) as of December 31, 2013.
[3]	Consists of a $5.0 million State of Connecticut economic development loan with a 3.0% fixed rate of interest. The loan was originated in 2012 and has a 10 year maturity. Principal payments are deferred for the first five years and the loan may be repaid at any point by the Company without penalty. The loan has a principal forgiveness provision in which up to $2.5 million of the loan may be forgiven if the Company meets certain employment targets during the first five years of the loan.

Commitments_and_Contingencies_1

Commitments and Contingencies (Detail) (USD $)	Dec. 31, 2013
In Millions, unless otherwise specified
Commitments and Contingencies Disclosure [Abstract]	'
Future contractual sublease rental income	$1.20

Commitments_and_Contingencies_2

Commitments and Contingencies (Detail) - Future Minimum Annual Cash Payments Under Non-Cancelable Operating Lease Agreements (USD $)	Dec. 31, 2013
In Thousands, unless otherwise specified
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]	'
2014	$34,525
2015	27,720
2016	20,415
2017	14,840
2018	11,145
Thereafter	82,485
Total minimum lease payments	$191,130	[1]
[1]	Excludes $1.2 million of future contractual sublease rental income.

Stockholders_Equity_Detail

Stockholders' Equity (Detail) (USD $)	12 Months Ended			0 Months Ended	2 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Feb. 04, 2014	Feb. 26, 2014
				Subsequent event	Subsequent event
Class of Stock [Line Items]	'	'	'	'	'
Common stock par value (in Dollars per share)	$0.00	$0.00	'	'	'
Cost of repurchased stock	$196,696,000	$111,304,000	$211,986,000	'	'
Payments for purchases of treasury stock	181,736,000	111,304,000	211,986,000	'	15,000,000
Stock repurchase program, authorized amount	$500,000,000	'	'	$800,000,000	'

Stockholders_Equity_Detail_Sum

Stockholders' Equity (Detail) - Summary of Transactions Relating to Common Stock	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
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	0
Purchases for treasury	0	0	0	[1]
Ending Balance	156,234,415	156,234,415	156,234,415
Treasury Stock	'	'	'
Common Stock Outstanding Roll Forward [Roll Forward]	'	'	'
Beginning Balance	62,873,100	62,891,251	60,245,718
Issuances under stock plans	-2,037,091	-2,756,389	-3,244,705
Purchases for treasury	3,432,854	2,738,238	5,890,238	[1]
Ending Balance	64,268,863	62,873,100	62,891,251
[1]	{F|ahBzfndlYmZpbGluZ3MtaHJkcmoLEgZYTUxEb2MiXlhCUkxEb2NHZW5JbmZvOmMwMzIzZjM1YzVlNjRiOTU4NjEwOTk2NTM1ZWFhZjZifFRleHRTZWxlY3Rpb246QjEzNTU3RTZCMDYxN0Y1NUE4MDg5MDcxRkQ5MkNCOEQM}

StockBased_Compensation_Detail

Stock-Based Compensation (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012	Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'		'	'
Number of shares available for grant	6,400,000		'	'
Stock-based compensation expense	$34,735,000		$36,378,000	$32,865,000
Total share-based compensation cost not yet recognized	41,000,000		'	'
Total share-based compensation expense not yet recognized, remaining weighted average service period	'2 years 73 days		'	'
Aggregate intrinsic value of outstanding shares	59,100,000		'	'
Aggregate intrinsic value of shares vested and exercisable	29,000,000		'	'
Stock grants during period (in shares)	300,000		'	'
Award percentage of shares achieved	117.10%		'	'
Weighted average remaining contractual term	'1 year		'	'
Remaining fully vested unexercised options outstanding, shares (less than)	200,000		'	'
Target Amount | Minimum	'		'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'		'	'
Percent of shares authorized for grant	0.00%		'	'
Target Amount | Maximum	'		'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'		'	'
Percent of shares authorized for grant	200.00%		'	'
Executive Officer | Performance Shares	'		'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'		'	'
Stock grants during period (in shares)	200,000		'	'
Executive Officer | Service-based Awards	'		'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'		'	'
Stock grants during period (in shares)	300,000		'	'
Employee Stock Option	'		'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'		'	'
Proceeds from stock options exercised	1,700,000		8,600,000	16,600,000
Unvested	'		'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'		'	'
Outstanding shares unvested	1,000,000		'	'
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	1,200,000		'	'
Proceeds from stock grants	4,400,000		3,800,000	3,400,000
Stock Appreciation Rights (SARs)	'		'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'		'	'
Total share-based compensation expense not yet recognized, remaining weighted average service period	'6 years 45 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		'	'
Outstanding shares unvested	1,600,000	[1],[2]	2,000,000	'
Stock grants during period (in shares)	400,000		'	'
Stock Appreciation Rights (SARs) | Non Executive	'		'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'		'	'
Stock grants during period (in shares)	400,000		'	'
Restricted Stock Units (RSUs)	'		'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'		'	'
Outstanding shares unvested	1,800,000	[3],[4]	2,500,000	'
Stock grants during period (in shares)	700,000	[5]	'	'
Restricted Stock Units (RSUs) | Performance Shares	'		'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'		'	'
Award vesting period	'4 years		'	'
Stock grants during period (in shares)	700,000		'	'
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]	'		'	'
Outstanding shares unvested	102,479		100,545	'
Stock grants during period (in shares)	9,718		'	'
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	$12,500,000		$5,100,000	$3,100,000
[1]	At December 31, 2013, SARs outstanding had an intrinsic value of $59.1 million. SARs vested and exercisable had an intrinsic value of $29.0 million.
[2]	At December 31, 2013, 1.0 million of these SARs were unvested. The Company expects that substantially all of these unvested awards will vest in future periods.
[3]	The weighted-average remaining contractual term of the outstanding RSUs is approximately 1 year.
[4]	The Company expects that substantially all of the outstanding awards at December 31, 2013 will vest in future periods.
[5]	The 0.7 million RSUs granted in 2013 consisted of 0.3 million performance-based RSUs awarded to executives and 0.4 million service-based RSUs awarded to non-executive employees and certain board members. The target number of performance-based RSUs awarded to executives in 2013 was 0.2 million, while the final amount could range from 0% to 200% of the target amount. The final amount was dependent on the increase in the Company's subscription-based contract value ("CV') for the year as measured on December 31, 2013. The actual CV increase achieved for 2013 was 117.1%, which resulted in the grant of 0.3 million performance-based RSUs.

StockBased_Compensation_Detail1

Stock-Based Compensation (Detail) - Stock-Based Compensation Expense By Award Type (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'		'		'
Stock-based compensation expense	$34.70	[1]	$36.40	[1]	$32.90	[1]
Stock appreciation rights	'		'		'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'		'		'
Stock-based compensation expense	5.2		6.4		4.4
Common stock equivalents	'		'		'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'		'		'
Stock-based compensation expense	0.6		0.5		0.5
Restricted stock units	'		'		'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'		'		'
Stock-based compensation expense	$28.90		$29.50		$28
[1]	Includes charges of $12.5 million, $5.1 million, and $3.1 million in 2013, 2012 and 2011, respectively, for awards to retirement-eligible employees since these awards vest on an accelerated basis

StockBased_Compensation_Detail2

Stock-Based Compensation (Detail) - Stock-Based Compensation Expense Recognized In Consolidated Statements Of Operations (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'		'		'
Stock-based compensation expense	$34.70	[1]	$36.40	[1]	$32.90	[1]
Costs of services and product development	'		'		'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'		'		'
Stock-based compensation expense	15.3		15.3		14.8
Selling, general, and administrative	'		'		'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'		'		'
Stock-based compensation expense	$19.40		$21.10		$18.10
[1]	Includes charges of $12.5 million, $5.1 million, and $3.1 million in 2013, 2012 and 2011, respectively, for awards to retirement-eligible employees since these awards vest on an accelerated basis

StockBased_Compensation_Detail3

Stock-Based Compensation (Detail) - Summary Of Changes In SARs Outstanding (USD $)	12 Months Ended
	Dec. 31, 2013
SARs	'
Granted (in shares)	300,000
Weighted- Average Remaining Contractual Term	'
Granted	'2 years 73 days
Stock Appreciation Rights (SARs)	'
SARs	'
Outstanding at December 31, 2012 (in shares)	2,000,000
Granted (in shares)	400,000
Forfeited (in shares)	0
Exercised (in shares)	-800,000
Outstanding at December 31, 2013 (in shares)	1,600,000	[1],[2]
Vested and exercisable at December 31, 2013 (in shares)	600,000	[2]
Per Share Weighted- Average Exercise Price	'
Outstanding at December 31, 2012 (in Dollars per share)	24.59
Granted (in Dollars per share)	49.37
Forfeited (in Dollars per share)	0
Exercised (in Dollars per share)	15.99
Outstanding at December 31, 2013 (in Dollars per share)	34.14	[1],[2]
Vested and exercisable at December 31, 2013 (in Dollars per share)	25.63	[2]
Per Share Weighted- Average Grant Date Fair Value	'
Outstanding at December 31, 2012 (in Dollars per share)	9.04
Granted (in Dollars per share)	14.88
Forfeited (in Dollars per share)	0
Exercised (in Dollars per share)	6.3
Outstanding at December 31, 2013 (in Dollars per share)	11.63	[1],[2]
Vested and exercisable at December 31, 2013 (in Dollars per share)	9.41	[2]
Weighted- Average Remaining Contractual Term	'
Outstanding at December 31, 2012	'4 years 36 days
Granted	'6 years 45 days
Outstanding at December 31, 2013	'4 years 125 days	[1],[2]
Vested and exercisable at December 31, 2013	'3 years 120 days	[2]
[1]	At December 31, 2013, SARs outstanding had an intrinsic value of $59.1 million. SARs vested and exercisable had an intrinsic value of $29.0 million.
[2]	At December 31, 2013, 1.0 million of these SARs were unvested. The Company expects that substantially all of these unvested awards will vest in future periods.

StockBased_Compensation_Detail4

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, 2013		Dec. 31, 2012		Dec. 31, 2011
Stock Appreciation Rights (SARs)	'		'		'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'		'		'
Expected dividend yield	0.00%	[1]	0.00%	[1]	0.00%	[1]
Expected stock price volatility	35.00%	[2]	40.00%	[2]	38.00%	[2]
Risk-free interest rate	0.80%	[3]	0.80%	[3]	2.20%	[3]
Expected life in years	'4 years 180 days	[4]	'4 years 222 days	[4]	'4 years 9 months	[4]
[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).

StockBased_Compensation_Detail5

Stock-Based Compensation (Detail) - Summary Of Changes In RSUs Outstanding (USD $)	12 Months Ended
	Dec. 31, 2013
Restricted Stock Units (RSUs)	'
Granted (in shares)	300,000
Restricted Stock Units (RSUs)	'
Restricted Stock Units (RSUs)	'
Outstanding at December 31, 2012 (in shares)	2,500,000
Granted (in shares)	700,000	[1]
Vested and released (in shares)	-1,400,000
Forfeited (in shares)	0
Outstanding at December 31, 2013 (in shares)	1,800,000	[2],[3]
Per Share Weighted Average Grant Date Fair Value	'
Outstanding at December 31, 2012 (in Dollars per share)	27.95
Granted (in Dollars per share)	49.86	[1]
Vested and released (in Dollars per share)	22.47
Forfeited (in Dollars per share)	0
Outstanding at December 31, 2013 (in Dollars per share)	38.83	[2],[3]
[1]	The 0.7 million RSUs granted in 2013 consisted of 0.3 million performance-based RSUs awarded to executives and 0.4 million service-based RSUs awarded to non-executive employees and certain board members. The target number of performance-based RSUs awarded to executives in 2013 was 0.2 million, while the final amount could range from 0% to 200% of the target amount. The final amount was dependent on the increase in the Company's subscription-based contract value ("CV') for the year as measured on December 31, 2013. The actual CV increase achieved for 2013 was 117.1%, which resulted in the grant of 0.3 million performance-based RSUs.
[2]	The weighted-average remaining contractual term of the outstanding RSUs is approximately 1 year.
[3]	The Company expects that substantially all of the outstanding awards at December 31, 2013 will vest in future periods.

StockBased_Compensation_Detail6

Stock-Based Compensation (Detail) - Summary Of Changes In CSEs Outstanding (USD $)	12 Months Ended
	Dec. 31, 2013
Common Stock Equivalents (CSEs)	'
Granted (in shares)	300,000
Common Stock Equivalents (CSEs)	'
Common Stock Equivalents (CSEs)	'
Outstanding at December 31, 2012 (in shares)	100,545
Granted (in shares)	9,718
Converted to common shares (in shares)	-7,784
Outstanding at December 31, 2013 (in shares)	102,479
Per Share Weighted- Average Grant Date Fair Value	'
Outstanding at December 31, 2012 (in Dollars per share)	16.89
Granted (in Dollars per share)	60.34
Converted to common shares (in Dollars per share)	60.31
Outstanding at December 31, 2013 (in Dollars per share)	17.71

Computation_of_Earnings_Per_Sh2

Computation of Earnings Per Share (Detail) (Common Stock Equivalents (CSEs))	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Common Stock Equivalents (CSEs)	'	'	'
Stock repurchased during period (in shares)	3.4	2.7	5.9

Computation_of_Earnings_Per_Sh3

Computation of Earnings Per Share (Detail) - Calculations Of Basic And Diluted Earnings Per Share (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Numerator:	'		'		'
Net income used for calculating basic and diluted earnings per common share	$182,801		$165,903		$136,902
Denominator:	'		'		'
Weighted average number of common shares used in the calculation of basic earnings per share	93,015	[1]	93,444	[1]	96,019	[1]
Common share equivalents associated with stock-based compensation plans	1,815	[1]	2,398	[1]	2,827	[1]
Shares used in the calculation of diluted earnings per share	94,830	[1]	95,842	[1]	98,846	[1]
Earnings per share:	'		'		'
Basic (in Dollars per share)	$1.97		$1.78		$1.43
Diluted (in Dollars per share)	$1.93		$1.73		$1.39
[1]	Company repurchased 3.4 million, 2.7 million, and 5.9 million shares of its Common Stock in 2013, 2012, and 2011, respectively.

Computation_of_Earnings_Per_Sh4

Computation of Earnings Per Share (Detail) - Common Share Equivalents Not Included in the Computation of Diluted EPS (USD $)	12 Months Ended
In Millions, except Per Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Earnings Per Share [Abstract]	'	'	'
Antidilutive common share equivalents as of December 31	0.3	0.7	0.5
Average market price per share of Common Stock during the year	$57.50	$43.80	$37.53

Income_Taxes_Detail

Income Taxes (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax [Line Items]	'	'	'
Current deferred tax assets	$19,500,000	$32,600,000	'
Current deferred tax liabilities	8,700,000	1,300,000	'
Non-current deferred tax assets	24,371,000	22,527,000	'
Non-current deferred tax liabilities	200,000	100,000	'
Valuation allowance, amount	600,000	1,900,000	'
Unrecognized tax benefits	14,488,000	17,552,000	18,345,000
Unrecognized tax benefits reductions resulting from settlements with taxing authorities and lapse of applicable statute of limitations	3,100,000	'	'
Liability for uncertain tax positions	11,400,000	13,100,000	'
Income tax penalties and interest expense	3,300,000	4,600,000	'
Penalties and interest expense	300,000	400,000	'
Unrecognized tax benefits that would impact effective tax rate	11,800,000	'	'
Unrecognized tax benefits that would result adjustments to other tax accounts	2,700,000	'	'
Earnings of certain non US subsidiaries indefinitely reinvested	140,000,000	'	'
Undistributed foreign earnings	33,000,000	'	'
Stamford	'	'	'
Income Tax [Line Items]	'	'	'
Unrecognized tax benefits	1,300,000	2,600,000	'
State and local jurisdiction	'	'	'
Income Tax [Line Items]	'	'	'
Operating loss carryforwards	91,300,000	'	'
Tax credit carryforwards	2,900,000	'	'
State and local jurisdiction | Minimum	'	'	'
Income Tax [Line Items]	'	'	'
Tax credit carryforwards, expiration period	'2 years	'	'
State and local jurisdiction | Maximum	'	'	'
Income Tax [Line Items]	'	'	'
Tax credit carryforwards, expiration period	'5 years	'	'
Non US	'	'	'
Income Tax [Line Items]	'	'	'
Operating loss carryforwards	30,300,000	'	'
Foreign tax credit carryforwards	1,300,000	'	'
Expire within one to five years | State and local jurisdiction	'	'	'
Income Tax [Line Items]	'	'	'
Operating loss carryforwards	2,900,000	'	'
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	87,300,000	'	'
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 within sixteen to twenty years | State and local jurisdiction	'	'	'
Income Tax [Line Items]	'	'	'
Operating loss carryforwards	1,100,000	'	'
Expire within sixteen to twenty years | State and local jurisdiction | Minimum	'	'	'
Income Tax [Line Items]	'	'	'
Operating loss carryforwards expiration period	'16 years	'	'
Expire within sixteen to twenty years | State and local jurisdiction | Maximum	'	'	'
Income Tax [Line Items]	'	'	'
Operating loss carryforwards expiration period	'20 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	1,000,000	'	'
Carried forward indefinitely | Non US	'	'	'
Income Tax [Line Items]	'	'	'
Operating loss carryforwards	$29,300,000	'	'

Income_Taxes_Detail_Summary_of

Income Taxes (Detail) - Summary of Components of Income Before Income Taxes (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest [Abstract]	'	'	'
U.S.	$186,330	$150,023	$124,915
Non-U.S.	80,109	85,573	77,269
Income before income taxes	$266,439	$235,596	$202,184

Income_Taxes_Detail_Components

Income Taxes (Detail) - Components of Income Tax Expenses (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Current tax expense:	'	'	'
U.S. federal	$20,111	$25,290	$23,327
State and local	4,943	2,508	4,236
Foreign	17,460	18,889	13,845
Total current	42,514	46,687	41,408
Deferred tax (benefit) expense:	'	'	'
U.S. federal	18,806	8,494	-5,192
State and local	2,742	-753	1,269
Foreign	-4,688	-8,080	-1,434
Total deferred	16,860	-339	-5,357
Total current and deferred	59,374	46,348	36,051
Total tax expense	83,638	69,693	65,282
Benefit (expense) relating to interest rate swap used to increase (decrease) equity	'	'	'
Deferred tax (benefit) expense:	'	'	'
Benefit (expense)	-1,405	51	3,134
Benefit from stock transactions with employees used to increase equity	'	'	'
Deferred tax (benefit) expense:	'	'	'
Benefit (expense)	25,373	21,304	25,812
Benefit (expense) relating to defined-benefit pension adjustments used to increase (decrease) equity	'	'	'
Deferred tax (benefit) expense:	'	'	'
Benefit (expense)	482	1,926	285
Benefit (expense) of acquired tax assets (liabilities) used to decrease (increase) goodwill	'	'	'
Deferred tax (benefit) expense:	'	'	'
Benefit (expense)	($186)	$64	$0

Income_Taxes_Detail_Current_an

Income Taxes (Detail) - Current and Long-Term Deferred Tax Assets and Liabilities (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Income Tax Disclosure [Abstract]	'	'
Expense accruals	$56,787	$49,404
Loss and credit carryforwards	17,648	22,433
Assets relating to equity compensation	19,773	18,878
Other assets	1,306	7,613
Gross deferred tax asset	95,514	98,328
Depreciation	-12,067	-8,995
Intangible assets	-25,338	-23,129
Prepaid expenses	-22,517	-10,500
Gross deferred tax liability	-59,922	-42,624
Valuation allowance	-617	-1,943
Net deferred tax asset	$34,975	$53,761

Income_Taxes_Detail_Difference

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, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Disclosure [Abstract]	'	'	'
Statutory tax rate	35.00%	35.00%	35.00%
State income taxes, net of federal benefit	3.20%	1.80%	3.80%
Foreign income taxed at different rates	-5.60%	-6.40%	-5.90%
Foreign tax credits	0.00%	-1.00%	-2.30%
Record (release) reserve for tax contingencies	0.30%	0.70%	3.10%
Record (release) valuation allowance	-0.50%	0.00%	-0.40%
Other items, net	-1.00%	-0.50%	-1.00%
Effective tax rate	31.40%	29.60%	32.30%

Income_Taxes_Detail_Reconcilia

Income Taxes (Detail) - Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits, Excluding Interest and Penalties (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]	'	'
Beginning balance	$17,552	$18,345
Additions based on tax positions related to the current year	4,237	4,301
Additions for tax positions of prior years	827	105
Reductions for tax positions of prior years	-1,973	-3,427
Reductions for expiration of statutes	-3,860	-296
Settlements	-1,575	-1,372
Change in foreign currency exchange rates	-720	-104
Ending balance	$14,488	$17,552

Derivatives_and_Hedging_Detail

Derivatives and Hedging (Detail) - Outstanding Derivatives Contracts (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012
	outstanding_contract		outstanding_contract
Number of Outstanding Contracts	90		69
Contract Notional Amount	$261,325		$276,100
Fair Value Asset (Liability)	-6,565	[1]	-9,996	[1]
OCI Unrealized (Loss), Net Of Tax	-3,903		-6,010
Other liabilities | Interest rate swap	'		'
Contract Notional Amount	200,000	[2]	'
Other current liabilities | Foreign currency forwards	'		'
Number of Outstanding Contracts	89	[3]	'
Contract Notional Amount	61,325	[3]	'
Fair Value Asset (Liability)	-60	[1],[3]	'
OCI Unrealized (Loss), Net Of Tax	0	[3]	'
Other current assets | Foreign currency forwards	'		'
Number of Outstanding Contracts	'		68	[3]
Contract Notional Amount	'		76,100	[3]
Fair Value Asset (Liability)	'		4	[1],[3]
OCI Unrealized (Loss), Net Of Tax	'		0	[3]
Designated as hedging instrument | Other liabilities | Interest rate swap	'		'
Number of Outstanding Contracts	1	[2]	1	[2]
Contract Notional Amount	'		200,000	[2]
Fair Value Asset (Liability)	-6,505	[1],[2]	-10,000	[1],[2]
OCI Unrealized (Loss), Net Of Tax	($3,903)	[2]	($6,010)	[2]
[1]	See Note 12 — Fair Value Disclosures below for the determination of the fair value of these instruments.
[2]	The swap is designated as a cash flow hedge of the forecasted interest payments on borrowings. As a result, changes in the fair value of this swap are deferred and are recorded in OCI, net of tax effect (see Note 5 — Debt for additional information).
[3]	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 offset the economic effects of these foreign currency transaction risks. 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. Substantially all of the outstanding contracts at December 31, 2013 matured by the end of January 2014.

Derivatives_and_Hedging_Detail1

Derivatives and Hedging (Detail) - Derivative Gains And Losses That Have Been Recognized In Condensed Consolidated Statements Of Operations (USD $)	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Derivative Instruments, Gain (Loss) [Line Items]	'		'		'
Derivative instruments, gain (loss) recognized in income, net	$4,100		$3,000		$5,300
Interest expense	'		'		'
Derivative Instruments, Gain (Loss) [Line Items]	'		'		'
Derivative instruments, gain (loss) recognized in income, net	4,000	[1]	3,600	[1]	4,100	[1]
Other expense, net	'		'		'
Derivative Instruments, Gain (Loss) [Line Items]	'		'		'
Derivative instruments, gain (loss) recognized in income, net	$100	[2]	($600)	[2]	$1,200	[2]
[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_Detail

Fair Value Disclosures (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Millions, unless otherwise specified
Fair Value Disclosures [Abstract]	'	'
Borrowings, fair value disclosure	$200	'
Money market funds at carrying value	7.8	8.2
Cash surrender value of life insurance	$24.80	$19.60

Fair_Value_Disclosures_Detail_

Fair Value Disclosures (Detail) - Assets And Liabilities Measured At Fair Value On Recurring Basis (USD $)	Dec. 31, 2013		Dec. 31, 2012
In Thousands, unless otherwise specified
Assets:	'		'
Assets measured at fair value on a recurring basis	$32,671		$27,999
Liabilities:	'		'
Liabilities measured at fair value on a recurring basis	43,091		41,460
Foreign currency forward contracts	'		'
Assets:	'		'
Assets measured at fair value on a recurring basis	116	[1]	204	[1]
Liabilities:	'		'
Liabilities measured at fair value on a recurring basis	176		200
Interest rate swap contracts	'		'
Liabilities:	'		'
Liabilities measured at fair value on a recurring basis	6,505	[2]	10,000	[2]
Plan assets	'		'
Assets:	'		'
Assets measured at fair value on a recurring basis	32,555	[3]	27,795	[3]
Plan liabilities	'		'
Liabilities:	'		'
Liabilities measured at fair value on a recurring basis	$36,410	[3]	$31,260	[3]
[1]	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.
[2]	The Company has an interest rate swap contract which hedges the risk from variability of interest rates on its borrowings (see Note 11 — Derivatives and Hedging). The fair value of the swap is based on a mark-to-market valuation prepared by a third-party broker. Valuation is 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 valuation prepared by the third-party broker through the use of an electronic quotation service.
[3]	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 plan’s 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 $7.8 million and $8.2 million as of December 31, 2013 and 2012, 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 $24.8 million and $19.6 million at December 31, 2013 and 2012, respectively. The related deferred compensation plan liabilities are recorded at the amount needed to settle the liability, which approximates fair value, and is based on a Level 2 input.

Employee_Benefits_Detail

Employee Benefits (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013
				Forecast	Saving And Investment Plan	Saving And Investment Plan	Saving And Investment Plan	Pension Reinsurance Asset
Defined Benefit Plan Disclosure [Line Items]	'	'	'	'	'	'	'	'
Employer matching contribution, percent	4.00%	'	'	'	'	'	'	'
Maximum annual contribution per employee, Amount	$7,000	'	'	'	'	'	'	'
Amount expensed in connection with 401k Plan	3,765,000	2,600,000	2,705,000	'	15,800,000	14,200,000	15,900,000	'
Deferred compensation plan assets	32,600,000	27,800,000	'	'	'	'	'	'
Deferred compensation liability	36,400,000	31,300,000	'	'	'	'	'	'
Compensation expense related to deferred compensation plan	400,000	300,000	'	'	'	'	'	'
Expected future benefit payments in 2014	600,000	'	'	'	'	'	'	'
Expected future benefit payments, in 2015	1,800,000	'	'	'	'	'	'	'
Expected future benefit payments, in 2016	700,000	'	'	'	'	'	'	'
Expected future benefit payments, in 2017	1,100,000	'	'	'	'	'	'	'
Expected future benefit payments, in 2018	1,000,000	'	'	'	'	'	'	'
Expected future benefit payments in the five years thereafter	7,500,000	'	'	'	'	'	'	'
Expected long-term return on assets	3.80%	'	'	'	'	'	'	'
Contributions by employer	5,900,000	'	'	'	'	'	'	'
Benefits paid to participants under defined benefit plans	-1,255,000	-680,000	-390,000	'	'	'	'	'
Other assets	'	'	'	'	'	'	'	9,300,000
Weighted average amortization period	'15 years	'	'	'	'	'	'	'
Defined Benefit Plan Amortization of Unrecognized Gains Losses (less than $0.1 million for 2014)	$100,000	($200,000)	($100,000)	$100,000	'	'	'	'

Employee_Benefits_Detail_Compo

Employee Benefits (Detail) - Components of Net Periodic Pension Expense (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]	'		'		'
Service cost	$2,545	[1]	$1,775	[1]	$1,890	[1]
Interest cost	1,075		980		1,010
Expected return on plan assets	-340		-115		-125
Recognition of actuarial loss (gain)	30		-215		-135
Recognition of termination benefits	455		175		65
Total defined benefit pension expense	$3,765		$2,600		$2,705
[1]	(1)The higher 2013 service cost was primarily due to additional employees covered under the plans.

Employee_Benefits_Detail_Assum

Employee Benefits (Detail) - Assumptions Used in Computation of Net Periodic Pension Expense	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]	'		'		'
Weighted-average discount rate	3.35%	[1]	3.20%	[1]	4.40%	[1]
Average compensation increase	2.70%		2.70%		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.

Employee_Benefits_Detail_Infor

Employee Benefits (Detail) - Information Related to Changes in Projected Benefit Obligation (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]	'		'		'
Projected benefit obligation at beginning of year	$31,605	[1]	$21,160	[1]	$19,730
Service cost	2,545	[2]	1,775	[2]	1,890	[2]
Interest cost	1,075		980		1,010
Actuarial loss (gain) due to assumption changes and plan experience	625		6,265		-948
Additions and contractual termination benefits	460		1,925		0
Benefits paid	-1,255		-680		-390
Foreign currency impact	-470		180		-132
Projected benefit obligation at end of year	$34,585	[1]	$31,605	[1]	$21,160	[1]
[1]	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.
[2]	(1)The higher 2013 service cost was primarily due to additional employees covered under the plans.

Employee_Benefits_Detail_Benef

Employee Benefits (Detail) - Benefit Plans and Related Amounts Recorded in Consolidated Balance Sheets (USD $)	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
In Thousands, unless otherwise specified
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]	'		'		'		'
Projected benefit obligation	$34,585	[1]	$31,605	[1]	$21,160	[1]	$19,730
Plan assets at fair value	-13,870		-8,885		-2,480		'
Funded status – shortfall	20,715		22,720		18,680		'
Amounts recorded in the Consolidated Balance Sheets for the plans:	'		'		'		'
Other liabilities — accrued pension obligation	20,715		22,720		18,680		'
Stockholders’ equity — deferred actuarial (loss) gain	'		($1,578)		$2,488		'
[1]	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.

Segment_Information_Detail

Segment Information (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
	segment
Number of reportable segments	3	'	'
Payments for capital improvements	$36,498	$44,337	$41,954
Stamford	'	'	'
Payments for capital improvements	$7,700	$17,000	$9,500
Maximum | Reportable segments	'	'	'
Percent of target bonus charges allocated to segments	100.00%	'	'

Segment_Information_Detail_Inf

Segment Information (Detail) - Information About Reportable Segments (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenues	$1,784,213	$1,615,808	$1,468,588
Total segment gross contribution	1,078,165	963,714	863,239
Corporate and other expenses	-802,673	-718,007	-649,177
Operating income	275,492	245,707	214,062
Research	'	'	'
Revenues	1,271,011	1,137,147	1,012,062
Total segment gross contribution	879,384	774,342	682,136
Consulting	'	'	'
Revenues	314,257	304,893	308,047
Total segment gross contribution	107,565	109,253	114,838
Events	'	'	'
Revenues	198,945	173,768	148,479
Total segment gross contribution	$91,216	$80,119	$66,265

Segment_Information_Segment_In

Segment Information Segment Information (Detail) - Reconciliation of Segment Gross Contribution to Net Income (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]	'		'		'
Total segment gross contribution	$1,078,165		$963,714		$863,239
Costs and expenses:	'		'		'
Selling, general and administrative	760,458		678,843		613,707
Acquisition and integration charges	337		2,420		0
Operating income	275,492		245,707		214,062
Provision for income taxes	83,638		69,693		65,282
Net income	182,801		165,903		136,902
Reportable segments	'		'		'
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]	'		'		'
Total segment gross contribution	1,078,165		963,714		863,239
Costs and expenses:	'		'		'
Selling, general and administrative	760,458		678,843		613,707
Depreciation and amortization	34,442		29,771		32,064
Acquisition and integration charges	337		2,420		0
Operating income	275,492		245,707		214,062
Interest expense and other	9,053		10,111		11,878
Provision for income taxes	83,638		69,693		65,282
Net income	182,801		165,903		136,902
Unallocated	'		'		'
Costs and expenses:	'		'		'
Cost of services and product development - unallocated	$7,436	[1]	$6,973	[1]	$3,406	[1]
[1]	(1)Amounts in parentheses represent deferred losses.

Segment_Information_Detail_Sum

Segment Information (Detail) - Summarized Information by Geographic Location (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Revenues:	'		'		'
Revenues	$1,784,213		$1,615,808		$1,468,588
Long-lived assets:	'		'		'
Long-lived assets	172,176	[1]	162,480	[1]	119,621	[1]
United States and Canada	'		'		'
Revenues:	'		'		'
Revenues	1,049,734		947,075		861,481
Long-lived assets:	'		'		'
Long-lived assets	123,877	[1],[2]	114,557	[1],[2]	85,194	[1],[2]
Europe, Middle East and Africa	'		'		'
Revenues:	'		'		'
Revenues	508,755		458,675		437,194
Long-lived assets:	'		'		'
Long-lived assets	34,363	[1]	30,967	[1]	23,673	[1]
Other International	'		'		'
Revenues:	'		'		'
Revenues	225,724		210,058		169,913
Long-lived assets:	'		'		'
Long-lived assets	$13,936	[1]	$16,956	[1]	$10,754	[1]
[1]	Excludes goodwill and other intangible assets.
[2]	The United States and Canada balances include costs capitalized in connection with the renovation of the Company’s Stamford headquarters facility (see Note 1 — Business and Significant Accounting Policies for additional description). These capitalized costs amounted to $7.7 million in 2013, $17.0 million in 2012, and $9.5 million in 2011.

Valuation_and_Qualifying_Accou2

Valuation and Qualifying Accounts (Detail) - Summarized Activity in Allowances (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Movement in Valuation Allowances and Reserves [Roll Forward]	'	'	'
Balance at Beginning of Year	$6,400	$7,260	$7,200
Additions Charged to Expense	2,350	1,930	930
Additions Charged Against Revenues	5,050	1,860	4,390
Deductions from Reserve	-6,800	-4,650	-5,260
Balance at End of Year	$7,000	$6,400	$7,260

Subsequent_Event_Detail

Subsequent Event (Detail) (USD $)	12 Months Ended	0 Months Ended
	Dec. 31, 2013	Feb. 04, 2014
		Subsequent event
Subsequent event	'	'
Stock repurchase program, authorized amount	$500,000,000	$800,000,000