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OTHER ITEMS AND CHARGES - Charges Associated with Closure of Southbridge Landfill (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Site Contingency [Line Items]
Landfill closure project (credit) charge	$ (356)	$ 263	$ 74
Southbridge Landfill closure charge, net	496	4,587	2,709
Southbridge Landfill
Site Contingency [Line Items]
Legal and transaction costs	868	2,285	2,709
Contract settlement charge	572	0	0
Landfill closure project (credit) charge	(944)	490	0
Legal settlement charge	0	2,000	0
Environmental remediation charge	0	(188)	0
Southbridge Landfill closure charge, net	$ 496	$ 4,587	$ 2,709

X

- Definition

The aggregate (recovery) charge associated with the closure of a landfill, which is comprised of an asset impairment charge, a development project charge write-off, an environmental remediation charge, a legal settlement charge, related legal and transaction costs and a recovery on insurance settlement. A positive number is an expense and a negative number is a gain.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

(Credit) charge associated with changes in the estimated costs to execute the closure plan.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

Litigation Settlement Charge

+ References

No definition available.

+ Details

Name:	cwst_LitigationSettlementCharge
Namespace Prefix:	cwst_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

Amount of any recovery from third parties that is credited to environmental remediation costs.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 30
-Section 50
-Paragraph 12
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13296-110859

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X

- Definition

Gain (loss) related to the termination of a contract between the parties. The termination may be due to many causes including early termination of a lease by a lessee, a breach of contract by one party, or a failure to perform.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3602-108585

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X

- Definition

The amount of expense provided in the period for legal costs incurred on or before the balance sheet date pertaining to resolved, pending or threatened litigation, including arbitration and mediation proceedings.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.3)
-URI http://asc.fasb.org/extlink&oid=123367319&loc=SL114868664-224227

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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