Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Feb. 14, 2018	Jun. 30, 2017
Document Information [Line Items]
Entity Registrant Name	CASELLA WASTE SYSTEMS INC
Entity Central Index Key	0000911177
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Document Type	10-K
Document Period End Date	Dec. 31, 2017
Document Period End Date	2017
Document Fiscal Period Focus	FY
Amendment Flag	false
Trading Symbol	CWST
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Public Float			$ 639.8
Class A Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		41,294,290
Class B Common Stock
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		988,200