Debt Instrument, Floor Interest Rate

No definition available.

Name:	cwst_DebtInstrumentFloorInterestRate
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Balance Type:	na
Period Type:	instant

- Definition

Debt Instrument, Interest Rate, Annual Increase, Upon Other Event Of Default

+ References

No definition available.

+ Details

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Namespace Prefix:	cwst_
Data Type:	dtr-types1:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt Instrument, Interest Rate, Annual Increase, Upon Payment Default

+ References

No definition available.

+ Details

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Namespace Prefix:	cwst_
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Balance Type:	na
Period Type:	duration

- Definition

Debt Instrument, Variable Rate Adjustment

+ References

No definition available.

+ Details

Name:	cwst_DebtInstrumentVariableRateAdjustment
Namespace Prefix:	cwst_
Data Type:	dtr-types1:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Sublimit to the amount of letters of credit allowed under credit agreement.

+ References

No definition available.

+ Details

Name:	cwst_LettersOfCreditSublimit
Namespace Prefix:	cwst_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of additional optional borrowing capacity under the credit facility.

+ References

No definition available.

+ Details

Name:	cwst_LineOfCreditFacilityAdditionalBorrowingCapacity
Namespace Prefix:	cwst_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line Of Credit Facility, Commitment Fee, Basis Spread

+ References

No definition available.

+ Details

Name:	cwst_LineOfCreditFacilityCommitmentFeeBasisSpread
Namespace Prefix:	cwst_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Line Of Credit Facility, Commitment Fee Percentage, Adjustment

+ References

No definition available.

+ Details

Name:	cwst_LineOfCreditFacilityCommitmentFeePercentageAdjustment
Namespace Prefix:	cwst_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Line of Credit Facility, Fronting Fee Percentage

+ References

No definition available.

+ Details

Name:	cwst_LineOfCreditFacilityFrontingFeePercentage
Namespace Prefix:	cwst_
Data Type:	dtr-types1:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

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-SubTopic 30
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+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

Name:	us-gaap_LettersOfCreditOutstandingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

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+ Details

Name:	us-gaap_LineOfCredit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- 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

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+ Details

Name:	us-gaap_LineOfCreditFacilityLineItems
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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-SubTopic 10
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+ Details

Name:	us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_LineOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=cwst_CreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
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Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
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Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SecuredDebtMember
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Balance Type:
Period Type:

- Details

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- Details

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Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_LetterOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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DEBT - Credit Facility (Details) - USD ($)	1 Months Ended	12 Months Ended
DEBT - Credit Facility (Details) - USD ($)	Sep. 30, 2024	Dec. 31, 2024	Jun. 30, 2023
Line of Credit \| Revolving Credit Facility
Line of Credit Facility [Line Items]
Line of credit drawn		$ 0
Credit Facility
Line of Credit Facility [Line Items]
Additional revolver capacity	$ 200,000,000
Facility term	5 years
Variable rate adjustment	0.04%
Commitment fee percentage, adjustment		0.01%
Floor interest rate		0.00%
Interest rate, annual increase upon payment default		2.00%
Interest rate, annual increase upon other event of default		2.00%
Credit Facility \| Minimum
Line of Credit Facility [Line Items]
Commitment fee percentage		0.20%
Credit Facility \| Maximum
Line of Credit Facility [Line Items]
Commitment fee percentage		0.40%
Credit Facility \| Secured Debt
Line of Credit Facility [Line Items]
Aggregate principal amount issued	$ 800,000,000
Credit Facility \| Line of Credit \| Minimum \| SOFR
Line of Credit Facility [Line Items]
Basis spread on variable rate		1.30%
Credit Facility \| Line of Credit \| Minimum \| Base Rate
Line of Credit Facility [Line Items]
Basis spread on variable rate		0.30%
Credit Facility \| Line of Credit \| Maximum \| SOFR
Line of Credit Facility [Line Items]
Basis spread on variable rate		2.175%
Credit Facility \| Line of Credit \| Maximum \| Base Rate
Line of Credit Facility [Line Items]
Basis spread on variable rate		1.175%
Credit Facility \| Line of Credit \| Revolving Credit Facility
Line of Credit Facility [Line Items]
Maximum borrowing	700,000,000
Letters of credit sublimit	$ 155,000,000
Remaining capacity		$ 675,403,000
Credit Facility \| Line of Credit \| Letter of Credit
Line of Credit Facility [Line Items]
Fronting fee		0.25%
Letters of credit		$ 24,597,000
2023 Term Loan A Facility \| Secured Debt
Line of Credit Facility [Line Items]
Aggregate principal amount issued			$ 430,000,000