COVER PAGE - shares	3 Months Ended
	Mar. 31, 2020	Apr. 30, 2020
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Entity Registrant Name	CASELLA WASTE SYSTEMS, INC.
Entity File Number	000-23211
Document Period End Date	Mar. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	--12-31
Entity Central Index Key	0000911177
Entity Incorporation, State or Country Code	DE
Entity Filer Category	Large Accelerated Filer
Title of 12(b) Security	Class A common stock, $0.01 par value per share
Trading Symbol	CWST
Security Exchange Name	NASDAQ
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Amendment Flag	false
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Tax Identification Number	03-0338873
Entity Address, Address Line One	25 Greens Hill Lane,
Entity Address, City or Town	Rutland,
Entity Address, State or Province	VT
Entity Address, Postal Zip Code	05701
City Area Code	802
Local Phone Number	775-0325
Class A Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		47,321,483
Class B Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		988,200