Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2022	Jul. 22, 2022
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2022
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q2
Trading Symbol	CASA
Entity Registrant Name	Casa Systems, Inc.
Entity Central Index Key	0001333835
Current Fiscal Year End Date	--12-31
Document Quarterly Report	true
Document Transition Report	false
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Shell Company	false
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity File Number	001-38324
Entity Tax Identification Number	75-3108867
Entity Incorporation, State or Country Code	DE
Entity Address, Address Line One	100 Old River Road
Entity Address, City or Town	Andover
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	01810
City Area Code	978
Local Phone Number	688-6706
Entity Common Stock, Shares Outstanding		94,412,431
Title of 12(b) Security	Common Stock, $0.001 par value per share
Security Exchange Name	NASDAQ