Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2022	Apr. 27, 2022
Cover [Abstract]
Entity Registrant Name	MERCER INTERNATIONAL INC.
Entity Central Index Key	0001333274
Document Type	10-Q
Document Period End Date	Mar. 31, 2022
Trading Symbol	MERC
Amendment Flag	false
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		66,132,492
Entity Shell Company	false
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Emerging Growth Company	false
Entity Small Business	false
Entity File Number	000-51826
Entity Incorporation, State or Country Code	WA
Entity Tax Identification Number	47-0956945
Entity Address, Address Line One	Suite 1120
Entity Address, Address Line Two	700 West Pender Street
Entity Address, City or Town	Vancouver
Entity Address, State or Province	BC
Entity Address, Country	CA
Entity Address, Postal Zip Code	V6C 1G8
City Area Code	604
Local Phone Number	684-1099
Title of 12(b) Security	Common Stock, par value $1.00 per share
Security Exchange Name	NASDAQ
Document Quarterly Report	true
Document Transition Report	false