Cover Page - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Feb. 15, 2020	Jun. 28, 2019
Document Information [Line Items]
Entity Registrant Name	CASELLA WASTE SYSTEMS, INC.
Document Type	10-K
Document Annual Report	true
Document Transition Report	false
Entity Central Index Key	0000911177
Current Fiscal Year End Date	--12-31
Entity File Number	000-23211
Entity Filer Category	Large Accelerated Filer
Document Period End Date	Dec. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	FY
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	03-0338873
Title of 12(b) Security	Class A common stock, $0.01 par value per share
Trading Symbol	CWST
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Interactive Data Current	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Shell Company	false
Amendment Flag	false
Entity Small Business	false
Entity Emerging Growth Company	false
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
Entity Public Float			$ 1,765
Documents Incorporated by Reference	Part III of this Annual Report on Form 10-K incorporates by reference information from the definitive Proxy Statement for the registrant’s 2020 Annual Meeting of Stockholders or a Form10-K/A to be filed with the Securities and Exchange Commission not later than 120 days after the registrant’s fiscal year ended December 31, 2019
Class A Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		46,803,112
Class B Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		988,200