Cover Page - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Feb. 15, 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	001-32147
Entity Registrant Name	GREENHILL & CO., INC
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	51-0500737
Entity Address, Address Line One	1271 Avenue of the Americas
Entity Address, City or Town	New York
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	10020
City Area Code	212
Local Phone Number	389-1500
Title of 12(b) Security	Common Stock, par value $.01 per share
Trading Symbol	GHL
Security Exchange Name	NYSE
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Entity Shell Company	false
Entity Public Float			$ 220
Entity Common Stock, Shares Outstanding		18,323,436
Documents Incorporated by Reference	Portions of the Registrant’s definitive proxy statement to be delivered to stockholders in connection with the 2022 annual meeting of stockholders to be held on April 27, 2022 are incorporated by reference in response to Part III of this Report.
Amendment Flag	false
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Entity Central Index Key	0001282977