XML 75 R58.htm IDEA: XBRL DOCUMENT
v3.20.1

COMMITMENTS AND CONTINGENCIES - Narrative (Detail) numberOfPlantiffs in Thousands | Sep. 17, 2019 numberOfPlantiffs | Apr. 28, 2017 USD ($) | Mar. 31, 2020 USD ($) | Dec. 31, 2019 USD ($) | Mar. 31, 2019 USD ($) | Dec. 31, 2018 USD ($) | Apr. 26, 2017 USD ($) | Jan. 29, 2016 | Apr. 30, 2011 USD ($) | May 31, 2009 USD ($) | Dec. 20, 2000 a
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Southbridge Landfill |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |
Risk free interest percentage rate |  |  | 1.90% |  |  |  |  |  |  |  |
Environmental remediation liability |  |  | $ 4,641,000 | $ 4,596,000 | $ 5,066,000 | $ 5,173,000 |  |  |  |  |
Potsdam Environmental Remediation |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |
Risk free interest percentage rate |  |  | 1.50% |  |  |  |  |  |  |  |
Scrap yard and solid waste transfer station (in acres) | a |  |  |  |  |  |  |  |  |  |  | 25
Undiscounted costs preferred remedies |  |  |  |  |  |  |  |  | $ 12,130,000 | $ 10,219,000 |
Remediation activities, participant share percentage |  |  |  |  |  |  |  | 15.00% |  |  |
Environmental remediation liability |  |  | $ 1,151,000 | $ 1,151,000 |  |  |  |  |  |  |
21E Settlement and Water System Construction Funding Agreement | Bonds |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |
Bond period |  | 20 years |  |  |  |  |  |  |  |  |
21E Settlement and Water System Construction Funding Agreement | Bonds | Maximum |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |
Anticipated cost |  | $ 5,000,000 |  |  |  |  |  |  |  |  |
Notice of Intent to Sue under the Resource Conservation and Recovery Act |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |
Estimate of possible loss |  |  |  |  |  |  | $ 5,000,000 |  |  |  |
Notice of Intent to Sue under the Resource Conservation and Recovery Act | MADEP and Casella Waste Systems |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |
Estimate of possible loss |  |  |  |  |  |  | $ 10,000,000 |  |  |  |
Ontario County, New York Class Action Litigation |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |
Number of citizens seeking damages | numberOfPlantiffs | 1 |  |  |  |  |  |  |  |  |  |
Notice of Intent to Sue for Violations of the CWA | NCES Landfil |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |
Estimate of possible loss |  |  | $ 1,415,000 |  |  |  |  |  |  |  |

X
- Definition Percentage participation in onsite remediation activities. + References No definition available. + Details
Name: | cwst_PercentageParticipationInOnsiteRemediationActivities
Namespace Prefix: | cwst_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Acreage of scrap yard owned by WSI. + References No definition available. + Details
Name: | cwst_ScrapYardAndSolidWasteTransferStation
Namespace Prefix: | cwst_
Data Type: | num:areaItemType
Balance Type: | na
Period Type: | instant

X
- Definition Estimated undiscounted remediation costs. + References No definition available. + Details
Name: | cwst_UndiscountedCostsPreferredRemedies
Namespace Prefix: | cwst_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Total costs accrued as of the balance sheet date for environmental loss contingencies. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=118942415&loc=d3e14326-108349 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 25 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6395460&loc=d3e13647-108346 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 30 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13207-110859 + Details
Name: | us-gaap_AccrualForEnvironmentalLossContingencies
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Rate applied to the undiscounted amount of environmental loss contingencies to arrive at the present value recorded as of the balance sheet date. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 30 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13207-110859 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 5.Y.Q1) -URI http://asc.fasb.org/extlink&oid=27011672&loc=d3e149879-122751 + Details
Name: | us-gaap_AccrualForEnvironmentalLossContingenciesDiscountRate
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- 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

X
- Definition Total anticipated costs associated with remediation, site restoration, postclosure, monitoring commitments, or other exit costs that may occur on the sale, disposal, or abandonment of a particular property resulting from unanticipated contamination of the assets. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 5.Y.Q4) -URI http://asc.fasb.org/extlink&oid=27011672&loc=d3e149879-122751 + Details
Name: | us-gaap_EnvironmentalExitCostsAnticipatedCost
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- 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. + Details
Name: | us-gaap_LossContingenciesLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Reflects the estimated amount of loss from the specified contingency as of the balance sheet date. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=118942415&loc=d3e14435-108349 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 9 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=118942415&loc=d3e14557-108349 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 460 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=118943654&loc=d3e12021-110248 + Details
Name: | us-gaap_LossContingencyEstimateOfPossibleLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Number of plaintiffs that have filed claims pertaining to a loss contingency. + References No definition available. + Details
Name: | us-gaap_LossContingencyNumberOfPlaintiffs
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_EnvironmentalRemediationSiteAxis=cwst_SouthbridgeLandfillMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_EnvironmentalRemediationSiteAxis=cwst_PotsdamEnvironmentalLiabilityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=cwst_A21ESettlementandWaterSystemConstructionFundingAgreementMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongtermDebtTypeAxis=us-gaap_BondsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_LitigationCaseAxis=cwst_NoticeofIntenttoSueundertheResourceConservationandRecoveryActMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=cwst_MassachusettsDepartmentofEnvironmentalProtectionMADEPandCasellaWasteSystemsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_LitigationCaseAxis=cwst_OntarioCountyNewYorkClassActionLitigationMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_LitigationCaseAxis=cwst_NoticeOfIntentToSueForViolationsOfTheCWAMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_EnvironmentalRemediationSiteAxis=cwst_NCESLandfilMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |