Cover Page - shares	9 Months Ended
	Sep. 30, 2021	Nov. 08, 2021	Oct. 28, 2021
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2021
Document Transition Report	false
Entity File Number	001-13718
Entity Registrant Name	Stagwell Inc
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	86-1390679
Entity Address, Address Line One	One World Trade Center, Floor 65
Entity Address, City or Town	New York,
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	10007
City Area Code	646
Local Phone Number	429-1800
Title of 12(b) Security	Class A Common Stock, par value $0.001 per share
Trading Symbol	STGW
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Central Index Key	0000876883
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Amendment Flag	false
Common Class A
Entity Information [Line Items]
Entity Common Stock, Shares Outstanding		113,198,517
Common Class B
Entity Information [Line Items]
Entity Common Stock, Shares Outstanding			3,946
Common Class C
Entity Information [Line Items]
Entity Common Stock, Shares Outstanding			179,970,051