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LEASES - Narrative (Details) | 6 Months Ended
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Jun. 30, 2020 Agreement
Leases [Abstract] |
Number of landfill operation and management agreements | 3

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- Definition Number of Landfill Operation and Management Agreements Entered Into + References No definition available. + Details
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Namespace Prefix: | cwst_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

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- References No definition available. + Details
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Namespace Prefix: | us-gaap_
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Balance Type: | na
Period Type: | duration