Cover Page - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2021	Feb. 17, 2022	Jun. 30, 2021
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2021
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	1-14443
Entity Registrant Name	GARTNER, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	04-3099750
Entity Address, Address Line One	P.O. Box 10212
Entity Address, Address Line Two	56 Top Gallant Road
Entity Address, City or Town	Stamford,
Entity Address, State or Province	CT
Entity Address, Postal Zip Code	06902-7700
City Area Code	203
Local Phone Number	316-1111
Title of 12(b) Security	Common Stock, $0.0005 par value per share
Trading Symbol	IT
Security Exchange Name	NYSE
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 19.7
Entity Common Stock, Shares Outstanding		82,287,402
Documents Incorporated by Reference	The definitive Proxy Statement for the Annual Meeting of Stockholders to be held on June 2, 2022 (the “2022 Proxy Statement”) is incorporated by reference into Part III to the extent described therein.
Entity Central Index Key	0000749251
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Amendment Flag	false