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Subsidiary Guarantors - Schedule of Condensed Consolidating Statement of Cash Flows (Detail) (USD $) In Thousands, unless otherwise specified | 8 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2014 | Apr. 30, 2014 | Apr. 30, 2013 | Apr. 30, 2012
Condensed Financial Statements, Captions [Line Items] |  |  |  |
Net cash provided by (used in) operating activities | $ 38,286 us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations | $ 49,642 us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations | $ 43,906 us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations | $ 64,171 us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations
Cash Flows from Investing Activities: |  |  |  |
Acquisitions, net of cash acquired | (360)us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired | (8,305)us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired | (25,225)us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired | (2,102)us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired
Additions to property, plant and equipment | (55,016)us-gaap_PaymentsToAcquirePropertyPlantAndEquipment | (43,326)us-gaap_PaymentsToAcquirePropertyPlantAndEquipment | (53,281)us-gaap_PaymentsToAcquirePropertyPlantAndEquipment | (57,834)us-gaap_PaymentsToAcquirePropertyPlantAndEquipment
Payments on landfill operating lease contracts | (4,739)cwst_PaymentsForLandfillOperatingLease | (6,505)cwst_PaymentsForLandfillOperatingLease | (6,261)cwst_PaymentsForLandfillOperatingLease | (6,616)cwst_PaymentsForLandfillOperatingLease
Payment for capital related to divestiture |  |  | (618)cwst_PaymentsForCapitalExpenditureOnDivestitureOfBusiness |
Payments related to investments |  | (2,107)us-gaap_PaymentsToAcquireInvestments | (3,207)us-gaap_PaymentsToAcquireInvestments | (5,045)us-gaap_PaymentsToAcquireInvestments
Proceeds from sale of equity method investment |  | 3,442 us-gaap_ProceedsFromSaleOfEquityMethodInvestments |  |
Proceeds from sale of property and equipment | 463 us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment | 1,524 us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment | 883 us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment | 1,492 us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment
Net cash provided by (used in) investing activities | (59,697)us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperations | (57,910)us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperations | (89,455)us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperations | (70,634)us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperations
Cash Flows from Financing Activities: |  |  |  |
Proceeds from long-term borrowings | 136,800 us-gaap_ProceedsFromIssuanceOfLongTermDebtAndCapitalSecuritiesNet | 161,650 us-gaap_ProceedsFromIssuanceOfLongTermDebtAndCapitalSecuritiesNet | 376,346 us-gaap_ProceedsFromIssuanceOfLongTermDebtAndCapitalSecuritiesNet | 163,500 us-gaap_ProceedsFromIssuanceOfLongTermDebtAndCapitalSecuritiesNet
Principal payments on long-term debt | (109,281)us-gaap_RepaymentsOfLongTermDebtAndCapitalSecurities | (152,380)us-gaap_RepaymentsOfLongTermDebtAndCapitalSecurities | (360,858)us-gaap_RepaymentsOfLongTermDebtAndCapitalSecurities | (152,806)us-gaap_RepaymentsOfLongTermDebtAndCapitalSecurities
Change in restricted cash | (5,819)us-gaap_ProceedsFromRepaymentsOfRestrictedCashFinancingActivities |  |  |
Payment of tender premium on second lien notes |  |  | (10,743)us-gaap_PaymentsOfDebtExtinguishmentCosts |
Payments of financing costs | (2,605)us-gaap_PaymentsOfFinancingCosts | (405)us-gaap_PaymentsOfFinancingCosts | (4,609)us-gaap_PaymentsOfFinancingCosts | (1,592)us-gaap_PaymentsOfFinancingCosts
Net proceeds from the issuance of class A common stock |  |  | 42,184 us-gaap_ProceedsFromIssuanceOfCommonStock |
Proceeds from the exercise of share based awards | 143 us-gaap_ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions | 143 us-gaap_ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions |  | 337 us-gaap_ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions
Excess tax benefit on the vesting of share based awards | 84 us-gaap_ExcessTaxBenefitFromShareBasedCompensationFinancingActivities |  | 96 us-gaap_ExcessTaxBenefitFromShareBasedCompensationFinancingActivities | 254 us-gaap_ExcessTaxBenefitFromShareBasedCompensationFinancingActivities
Contributions from noncontrolling interest holders |  |  | 2,531 us-gaap_ProceedsFromMinorityShareholders | 536 us-gaap_ProceedsFromMinorityShareholders
Other |  |  | (4,513)us-gaap_ProceedsFromPaymentsForOtherFinancingActivities | 591 us-gaap_ProceedsFromPaymentsForOtherFinancingActivities
Inter company borrowings |  |  |  |
Net cash provided by (used in) financing activities | 19,322 us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperations | 9,008 us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperations | 44,947 us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperations | 10,229 us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperations
Net cash provided by (used in) discontinued operations | 1,830 us-gaap_NetCashProvidedByUsedInDiscontinuedOperations | (31)us-gaap_NetCashProvidedByUsedInDiscontinuedOperations | (2,177)us-gaap_NetCashProvidedByUsedInDiscontinuedOperations | (1,049)us-gaap_NetCashProvidedByUsedInDiscontinuedOperations
Net increase (decrease) in cash and cash equivalents | (259)us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease | 709 us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease | (2,779)us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease | 2,717 us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease
Cash and cash equivalents, beginning of period | 2,464 us-gaap_CashAndCashEquivalentsAtCarryingValue | 1,755 us-gaap_CashAndCashEquivalentsAtCarryingValue | 4,534 us-gaap_CashAndCashEquivalentsAtCarryingValue | 1,817 us-gaap_CashAndCashEquivalentsAtCarryingValue
Cash and cash equivalents, end of period | 2,205 us-gaap_CashAndCashEquivalentsAtCarryingValue | 2,464 us-gaap_CashAndCashEquivalentsAtCarryingValue | 1,755 us-gaap_CashAndCashEquivalentsAtCarryingValue | 4,534 us-gaap_CashAndCashEquivalentsAtCarryingValue
Discontinued operations: |  |  |  |
Net cash provided by (used in) discontinued operations | 1,830 us-gaap_NetCashProvidedByUsedInDiscontinuedOperations | (31)us-gaap_NetCashProvidedByUsedInDiscontinuedOperations | (2,177)us-gaap_NetCashProvidedByUsedInDiscontinuedOperations | (1,049)us-gaap_NetCashProvidedByUsedInDiscontinuedOperations
Net increase (decrease) in cash and cash equivalents | (259)us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease | 709 us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease | (2,779)us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease | 2,717 us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease
Cash and cash equivalents, beginning of period | 2,464 us-gaap_CashAndCashEquivalentsAtCarryingValue | 1,755 us-gaap_CashAndCashEquivalentsAtCarryingValue | 4,534 us-gaap_CashAndCashEquivalentsAtCarryingValue | 1,817 us-gaap_CashAndCashEquivalentsAtCarryingValue
Cash and cash equivalents, end of period | 2,205 us-gaap_CashAndCashEquivalentsAtCarryingValue | 2,464 us-gaap_CashAndCashEquivalentsAtCarryingValue | 1,755 us-gaap_CashAndCashEquivalentsAtCarryingValue | 4,534 us-gaap_CashAndCashEquivalentsAtCarryingValue
Net cash provided by (used in) operating activities | 38,286 us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations | 49,642 us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations | 43,906 us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations | 64,171 us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations
Parent [Member] |  |  |  |
Condensed Financial Statements, Captions [Line Items] |  |  |  |
Net cash provided by (used in) operating activities | (27,340)us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | (40,365)us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | (5,319)us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 4,552 us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Cash Flows from Investing Activities: |  |  |  |
Acquisitions, net of cash acquired |  |  |  |
Additions to property, plant and equipment | (1,433)us-gaap_PaymentsToAcquirePropertyPlantAndEquipment / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | (1,675)us-gaap_PaymentsToAcquirePropertyPlantAndEquipment / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | (203)us-gaap_PaymentsToAcquirePropertyPlantAndEquipment / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | (574)us-gaap_PaymentsToAcquirePropertyPlantAndEquipment / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Payments on landfill operating lease contracts |  |  |  |
Payment for capital related to divestiture |  |  |  |
Payments related to investments |  | (2,107)us-gaap_PaymentsToAcquireInvestments / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | (4,166)us-gaap_PaymentsToAcquireInvestments / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | (2,740)us-gaap_PaymentsToAcquireInvestments / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Proceeds from sale of equity method investment |  | 3,442 us-gaap_ProceedsFromSaleOfEquityMethodInvestments / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  |
Proceeds from sale of property and equipment |  |  |  |
Net cash provided by (used in) investing activities | (1,433)us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | (340)us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | (4,369)us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | (3,314)us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Cash Flows from Financing Activities: |  |  |  |
Proceeds from long-term borrowings |  | 161,650 us-gaap_ProceedsFromIssuanceOfLongTermDebtAndCapitalSecuritiesNet / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 334,497 us-gaap_ProceedsFromIssuanceOfLongTermDebtAndCapitalSecuritiesNet / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 163,500 us-gaap_ProceedsFromIssuanceOfLongTermDebtAndCapitalSecuritiesNet / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Principal payments on long-term debt | (108,917)us-gaap_RepaymentsOfLongTermDebtAndCapitalSecurities / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | (151,074)us-gaap_RepaymentsOfLongTermDebtAndCapitalSecurities / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | (359,342)us-gaap_RepaymentsOfLongTermDebtAndCapitalSecurities / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | (151,390)us-gaap_RepaymentsOfLongTermDebtAndCapitalSecurities / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Change in restricted cash | (5,819)us-gaap_ProceedsFromRepaymentsOfRestrictedCashFinancingActivities / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  |  |
Payment of tender premium on second lien notes |  |  | (10,743)us-gaap_PaymentsOfDebtExtinguishmentCosts / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |
Payments of financing costs | (2,605)us-gaap_PaymentsOfFinancingCosts / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | (405)us-gaap_PaymentsOfFinancingCosts / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  | (1,592)us-gaap_PaymentsOfFinancingCosts / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Net proceeds from the issuance of class A common stock |  |  | 42,184 us-gaap_ProceedsFromIssuanceOfCommonStock / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |
Proceeds from the exercise of share based awards | 143 us-gaap_ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  |  |
Excess tax benefit on the vesting of share based awards | 84 us-gaap_ExcessTaxBenefitFromShareBasedCompensationFinancingActivities / dei_LegalEntityAxis = us-gaap_ParentCompanyMember |  |  |
Contributions from noncontrolling interest holders |  |  |  |
Other |  |  | (4,513)us-gaap_ProceedsFromPaymentsForOtherFinancingActivities / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 591 us-gaap_ProceedsFromPaymentsForOtherFinancingActivities / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Inter company borrowings | 145,332 cwst_IntercompanyBorrowings / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 31,425 cwst_IntercompanyBorrowings / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 5,066 cwst_IntercompanyBorrowings / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | (10,079)cwst_IntercompanyBorrowings / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Net cash provided by (used in) financing activities | 28,218 us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 41,596 us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 7,149 us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 1,030 us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Net cash provided by (used in) discontinued operations |  |  |  |
Net increase (decrease) in cash and cash equivalents | (555)us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 891 us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | (2,539)us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 2,268 us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Cash and cash equivalents, beginning of period | 2,151 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 1,260 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 3,799 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 1,531 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Cash and cash equivalents, end of period | 1,596 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 2,151 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 1,260 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 3,799 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Discontinued operations: |  |  |  |
Net cash provided by (used in) discontinued operations |  |  |  |
Net increase (decrease) in cash and cash equivalents | (555)us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 891 us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | (2,539)us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 2,268 us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Cash and cash equivalents, beginning of period | 2,151 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 1,260 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 3,799 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 1,531 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Cash and cash equivalents, end of period | 1,596 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 2,151 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 1,260 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 3,799 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Net cash provided by (used in) operating activities | (27,340)us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | (40,365)us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | (5,319)us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 4,552 us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Guarantors [Member] |  |  |  |
Condensed Financial Statements, Captions [Line Items] |  |  |  |
Net cash provided by (used in) operating activities | 65,622 us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 89,792 us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 50,527 us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 59,088 us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Cash Flows from Investing Activities: |  |  |  |
Acquisitions, net of cash acquired | (360)us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | (8,305)us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | (25,225)us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | (2,102)us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Additions to property, plant and equipment | (53,583)us-gaap_PaymentsToAcquirePropertyPlantAndEquipment / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | (41,236)us-gaap_PaymentsToAcquirePropertyPlantAndEquipment / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | (48,058)us-gaap_PaymentsToAcquirePropertyPlantAndEquipment / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | (54,681)us-gaap_PaymentsToAcquirePropertyPlantAndEquipment / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Payments on landfill operating lease contracts | (4,739)cwst_PaymentsForLandfillOperatingLease / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | (6,505)cwst_PaymentsForLandfillOperatingLease / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | (6,261)cwst_PaymentsForLandfillOperatingLease / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | (6,616)cwst_PaymentsForLandfillOperatingLease / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Payment for capital related to divestiture |  |  | (618)cwst_PaymentsForCapitalExpenditureOnDivestitureOfBusiness / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember |
Payments related to investments | (310)us-gaap_PaymentsToAcquireInvestments / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember |  | (2,707)us-gaap_PaymentsToAcquireInvestments / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | (4,184)us-gaap_PaymentsToAcquireInvestments / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Proceeds from sale of equity method investment |  |  |  |
Proceeds from sale of property and equipment | 463 us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 1,524 us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 883 us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 1,492 us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Net cash provided by (used in) investing activities | (58,574)us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | (57,155)us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | (83,732)us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | (66,620)us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Cash Flows from Financing Activities: |  |  |  |
Proceeds from long-term borrowings | 136,800 us-gaap_ProceedsFromIssuanceOfLongTermDebtAndCapitalSecuritiesNet / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember |  | 41,849 us-gaap_ProceedsFromIssuanceOfLongTermDebtAndCapitalSecuritiesNet / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember |
Principal payments on long-term debt | (364)us-gaap_RepaymentsOfLongTermDebtAndCapitalSecurities / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | (1,306)us-gaap_RepaymentsOfLongTermDebtAndCapitalSecurities / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | (1,516)us-gaap_RepaymentsOfLongTermDebtAndCapitalSecurities / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | (1,416)us-gaap_RepaymentsOfLongTermDebtAndCapitalSecurities / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Change in restricted cash |  |  |  |
Payment of tender premium on second lien notes |  |  |  |
Payments of financing costs |  |  |  |
Net proceeds from the issuance of class A common stock |  |  |  |
Proceeds from the exercise of share based awards |  | 143 us-gaap_ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember |  |
Excess tax benefit on the vesting of share based awards |  |  |  |
Contributions from noncontrolling interest holders |  |  |  |
Other |  |  |  |
Inter company borrowings | (145,332)cwst_IntercompanyBorrowings / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | (31,425)cwst_IntercompanyBorrowings / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | (5,066)cwst_IntercompanyBorrowings / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 10,079 cwst_IntercompanyBorrowings / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Net cash provided by (used in) financing activities | (8,896)us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | (32,588)us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 35,267 us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 8,663 us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Net cash provided by (used in) discontinued operations | 1,830 us-gaap_NetCashProvidedByUsedInDiscontinuedOperations / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | (31)us-gaap_NetCashProvidedByUsedInDiscontinuedOperations / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | (2,177)us-gaap_NetCashProvidedByUsedInDiscontinuedOperations / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | (1,049)us-gaap_NetCashProvidedByUsedInDiscontinuedOperations / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Net increase (decrease) in cash and cash equivalents | (18)us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 18 us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | (115)us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 82 us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Cash and cash equivalents, beginning of period | 271 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 253 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 368 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 286 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Cash and cash equivalents, end of period | 253 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 271 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 253 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 368 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Discontinued operations: |  |  |  |
Net cash provided by (used in) discontinued operations | 1,830 us-gaap_NetCashProvidedByUsedInDiscontinuedOperations / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | (31)us-gaap_NetCashProvidedByUsedInDiscontinuedOperations / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | (2,177)us-gaap_NetCashProvidedByUsedInDiscontinuedOperations / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | (1,049)us-gaap_NetCashProvidedByUsedInDiscontinuedOperations / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Net increase (decrease) in cash and cash equivalents | (18)us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 18 us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | (115)us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 82 us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Cash and cash equivalents, beginning of period | 271 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 253 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 368 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 286 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Cash and cash equivalents, end of period | 253 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 271 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 253 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 368 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Net cash provided by (used in) operating activities | 65,622 us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 89,792 us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 50,527 us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember | 59,088 us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember
Non-Guarantors [Member] |  |  |  |
Condensed Financial Statements, Captions [Line Items] |  |  |  |
Net cash provided by (used in) operating activities | 4 us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 215 us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | (1,302)us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 531 us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
Cash Flows from Investing Activities: |  |  |  |
Acquisitions, net of cash acquired |  |  |  |
Additions to property, plant and equipment |  | (415)us-gaap_PaymentsToAcquirePropertyPlantAndEquipment / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | (5,020)us-gaap_PaymentsToAcquirePropertyPlantAndEquipment / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | (2,579)us-gaap_PaymentsToAcquirePropertyPlantAndEquipment / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
Payments on landfill operating lease contracts |  |  |  |
Payment for capital related to divestiture |  |  |  |
Payments related to investments | 310 us-gaap_PaymentsToAcquireInvestments / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember |  | 3,666 us-gaap_PaymentsToAcquireInvestments / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 1,879 us-gaap_PaymentsToAcquireInvestments / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
Proceeds from sale of equity method investment |  |  |  |
Proceeds from sale of property and equipment |  |  |  |
Net cash provided by (used in) investing activities | 310 us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | (415)us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | (1,354)us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | (700)us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
Cash Flows from Financing Activities: |  |  |  |
Proceeds from long-term borrowings |  |  |  |
Principal payments on long-term debt |  |  |  |
Change in restricted cash |  |  |  |
Payment of tender premium on second lien notes |  |  |  |
Payments of financing costs |  |  |  |
Net proceeds from the issuance of class A common stock |  |  |  |
Proceeds from the exercise of share based awards |  |  |  |
Excess tax benefit on the vesting of share based awards |  |  |  |
Contributions from noncontrolling interest holders |  |  | 2,531 us-gaap_ProceedsFromMinorityShareholders / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 536 us-gaap_ProceedsFromMinorityShareholders / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
Other |  |  |  |
Inter company borrowings |  |  |  |
Net cash provided by (used in) financing activities |  |  | 2,531 us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 536 us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
Net cash provided by (used in) discontinued operations |  |  |  |
Net increase (decrease) in cash and cash equivalents | 314 us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | (200)us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | (125)us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 367 us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
Cash and cash equivalents, beginning of period | 42 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 242 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 367 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember |
Cash and cash equivalents, end of period | 356 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 42 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 242 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 367 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
Discontinued operations: |  |  |  |
Net cash provided by (used in) discontinued operations |  |  |  |
Net increase (decrease) in cash and cash equivalents | 314 us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | (200)us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | (125)us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 367 us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
Cash and cash equivalents, beginning of period | 42 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 242 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 367 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember |
Cash and cash equivalents, end of period | 356 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 42 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 242 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 367 us-gaap_CashAndCashEquivalentsAtCarryingValue / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
Net cash provided by (used in) operating activities | 4 us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 215 us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | (1,302)us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember | 531 us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations / dei_LegalEntityAxis = us-gaap_NonGuarantorSubsidiariesMember
Elimination [Member] |  |  |  |
Condensed Financial Statements, Captions [Line Items] |  |  |  |
Net cash provided by (used in) operating activities |  |  |  |
Cash Flows from Investing Activities: |  |  |  |
Acquisitions, net of cash acquired |  |  |  |
Additions to property, plant and equipment |  |  |  |
Payments on landfill operating lease contracts |  |  |  |
Payment for capital related to divestiture |  |  |  |
Payments related to investments |  |  |  |
Proceeds from sale of equity method investment |  |  |  |
Proceeds from sale of property and equipment |  |  |  |
Net cash provided by (used in) investing activities |  |  |  |
Cash Flows from Financing Activities: |  |  |  |
Proceeds from long-term borrowings |  |  |  |
Principal payments on long-term debt |  |  |  |
Change in restricted cash |  |  |  |
Payment of tender premium on second lien notes |  |  |  |
Payments of financing costs |  |  |  |
Net proceeds from the issuance of class A common stock |  |  |  |
Proceeds from the exercise of share based awards |  |  |  |
Excess tax benefit on the vesting of share based awards |  |  |  |
Contributions from noncontrolling interest holders |  |  |  |
Other |  |  |  |
Inter company borrowings |  |  |  |
Net cash provided by (used in) financing activities |  |  |  |
Net cash provided by (used in) discontinued operations |  |  |  |
Net increase (decrease) in cash and cash equivalents |  |  |  |
Cash and cash equivalents, beginning of period |  |  |  |
Cash and cash equivalents, end of period |  |  |  |
Discontinued operations: |  |  |  |
Net cash provided by (used in) discontinued operations |  |  |  |
Net increase (decrease) in cash and cash equivalents |  |  |  |
Cash and cash equivalents, beginning of period |  |  |  |
Cash and cash equivalents, end of period |  |  |  |
Net cash provided by (used in) operating activities |  |  |  |
Acquisition [Member] |  |  |  |
Cash Flows from Investing Activities: |  |  |  |
Additions to property, plant and equipment | (45)us-gaap_PaymentsToAcquirePropertyPlantAndEquipment / us-gaap_PropertyPlantAndEquipmentByTypeAxis = cwst_AcquisitionsMember | (2,633)us-gaap_PaymentsToAcquirePropertyPlantAndEquipment / us-gaap_PropertyPlantAndEquipmentByTypeAxis = cwst_AcquisitionsMember | (1,746)us-gaap_PaymentsToAcquirePropertyPlantAndEquipment / us-gaap_PropertyPlantAndEquipmentByTypeAxis = cwst_AcquisitionsMember | (529)us-gaap_PaymentsToAcquirePropertyPlantAndEquipment / us-gaap_PropertyPlantAndEquipmentByTypeAxis = cwst_AcquisitionsMember
Acquisition [Member] | Parent [Member] |  |  |  |
Cash Flows from Investing Activities: |  |  |  |
Additions to property, plant and equipment |  |  |  |
Acquisition [Member] | Guarantors [Member] |  |  |  |
Cash Flows from Investing Activities: |  |  |  |
Additions to property, plant and equipment | (45)us-gaap_PaymentsToAcquirePropertyPlantAndEquipment / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember / us-gaap_PropertyPlantAndEquipmentByTypeAxis = cwst_AcquisitionsMember | (2,633)us-gaap_PaymentsToAcquirePropertyPlantAndEquipment / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember / us-gaap_PropertyPlantAndEquipmentByTypeAxis = cwst_AcquisitionsMember | (1,746)us-gaap_PaymentsToAcquirePropertyPlantAndEquipment / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember / us-gaap_PropertyPlantAndEquipmentByTypeAxis = cwst_AcquisitionsMember | (529)us-gaap_PaymentsToAcquirePropertyPlantAndEquipment / dei_LegalEntityAxis = us-gaap_GuarantorSubsidiariesMember / us-gaap_PropertyPlantAndEquipmentByTypeAxis = cwst_AcquisitionsMember
Acquisition [Member] | Non-Guarantors [Member] |  |  |  |
Cash Flows from Investing Activities: |  |  |  |
Additions to property, plant and equipment |  |  |  |
Acquisition [Member] | Elimination [Member] |  |  |  |
Cash Flows from Investing Activities: |  |  |  |
Additions to property, plant and equipment |  |  |  |
Transition Period 2014 [Member] |  |  |  |
Condensed Financial Statements, Captions [Line Items] |  |  |  |
Net cash provided by (used in) operating activities | 38,286 us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations / us-gaap_StatementScenarioAxis = cwst_TransitionPeriodMember |  |  |
Cash Flows from Investing Activities: |  |  |  |
Acquisitions, net of cash acquired | (360)us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired / us-gaap_StatementScenarioAxis = cwst_TransitionPeriodMember |  |  |
Additions to property, plant and equipment | (55,016)us-gaap_PaymentsToAcquirePropertyPlantAndEquipment / us-gaap_StatementScenarioAxis = cwst_TransitionPeriodMember |  |  |
Payments on landfill operating lease contracts | (4,739)cwst_PaymentsForLandfillOperatingLease / us-gaap_StatementScenarioAxis = cwst_TransitionPeriodMember |  |  |
Proceeds from sale of property and equipment | 463 us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment / us-gaap_StatementScenarioAxis = cwst_TransitionPeriodMember |  |  |
Net cash provided by (used in) investing activities | (59,697)us-gaap_NetCashProvidedByUsedInInvestingActivitiesContinuingOperations / us-gaap_StatementScenarioAxis = cwst_TransitionPeriodMember |  |  |
Cash Flows from Financing Activities: |  |  |  |
Proceeds from long-term borrowings | 136,800 us-gaap_ProceedsFromIssuanceOfLongTermDebtAndCapitalSecuritiesNet / us-gaap_StatementScenarioAxis = cwst_TransitionPeriodMember |  |  |
Principal payments on long-term debt | (109,281)us-gaap_RepaymentsOfLongTermDebtAndCapitalSecurities / us-gaap_StatementScenarioAxis = cwst_TransitionPeriodMember |  |  |
Change in restricted cash | (5,819)us-gaap_ProceedsFromRepaymentsOfRestrictedCashFinancingActivities / us-gaap_StatementScenarioAxis = cwst_TransitionPeriodMember |  |  |
Payments of financing costs | (2,605)us-gaap_PaymentsOfFinancingCosts / us-gaap_StatementScenarioAxis = cwst_TransitionPeriodMember |  |  |
Proceeds from the exercise of share based awards | 143 us-gaap_ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlansIncludingStockOptions / us-gaap_StatementScenarioAxis = cwst_TransitionPeriodMember |  |  |
Excess tax benefit on the vesting of share based awards | 84 us-gaap_ExcessTaxBenefitFromShareBasedCompensationFinancingActivities / us-gaap_StatementScenarioAxis = cwst_TransitionPeriodMember |  |  |
Net cash provided by (used in) financing activities | 19,322 us-gaap_NetCashProvidedByUsedInFinancingActivitiesContinuingOperations / us-gaap_StatementScenarioAxis = cwst_TransitionPeriodMember |  |  |
Net cash provided by (used in) discontinued operations | 1,830 us-gaap_NetCashProvidedByUsedInDiscontinuedOperations / us-gaap_StatementScenarioAxis = cwst_TransitionPeriodMember |  |  |
Net increase (decrease) in cash and cash equivalents | (259)us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / us-gaap_StatementScenarioAxis = cwst_TransitionPeriodMember |  |  |
Cash and cash equivalents, beginning of period | 2,464 us-gaap_CashAndCashEquivalentsAtCarryingValue / us-gaap_StatementScenarioAxis = cwst_TransitionPeriodMember |  |  |
Cash and cash equivalents, end of period | 2,205 us-gaap_CashAndCashEquivalentsAtCarryingValue / us-gaap_StatementScenarioAxis = cwst_TransitionPeriodMember |  |  |
Discontinued operations: |  |  |  |
Net cash provided by (used in) discontinued operations | 1,830 us-gaap_NetCashProvidedByUsedInDiscontinuedOperations / us-gaap_StatementScenarioAxis = cwst_TransitionPeriodMember |  |  |
Net increase (decrease) in cash and cash equivalents | (259)us-gaap_CashAndCashEquivalentsPeriodIncreaseDecrease / us-gaap_StatementScenarioAxis = cwst_TransitionPeriodMember |  |  |
Cash and cash equivalents, beginning of period | 2,464 us-gaap_CashAndCashEquivalentsAtCarryingValue / us-gaap_StatementScenarioAxis = cwst_TransitionPeriodMember |  |  |
Cash and cash equivalents, end of period | 2,205 us-gaap_CashAndCashEquivalentsAtCarryingValue / us-gaap_StatementScenarioAxis = cwst_TransitionPeriodMember |  |  |
Net cash provided by (used in) operating activities | 38,286 us-gaap_NetCashProvidedByUsedInOperatingActivitiesContinuingOperations / us-gaap_StatementScenarioAxis = cwst_TransitionPeriodMember |  |  |
Transition Period 2014 [Member] | Acquisition [Member] |  |  |  |
Cash Flows from Investing Activities: |  |  |  |
Additions to property, plant and equipment | $ (45)us-gaap_PaymentsToAcquirePropertyPlantAndEquipment / us-gaap_PropertyPlantAndEquipmentByTypeAxis = cwst_AcquisitionsMember / us-gaap_StatementScenarioAxis = cwst_TransitionPeriodMember |  |  |

X
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- Definition The cash outflow associated with landfill operating agreements consisting of up-front or one-time payments, future minimum rental payments, including success/expansion fees, other direct costs and capping, closure and post closure costs. + References No definition available. + Details
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- Definition Amount of increase (decrease) in cash and cash equivalents. Cash and cash equivalents are the amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Includes effect from exchange rate changes. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3521-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 230 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6450594&loc=d3e33268-110906 + Details
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- Definition Amount of cash inflow from realized tax benefit related to deductible compensation cost reported on the entity's tax return for equity instruments in excess of the compensation cost for those instruments recognized for financial reporting purposes. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 20 -Section 55 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=32706628&loc=d3e11374-113907 + Details
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- Definition Increase (decrease) in cash associated with the entity's discontinued operations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3521-108585 + Details
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- Definition Amount of cash inflow (outflow) of financing activities, excluding discontinued operations. Financing activity cash flows include obtaining resources from owners and providing them with a return on, and a return of, their investment; borrowing money and repaying amounts borrowed, or settling the obligation; and obtaining and paying for other resources obtained from creditors on long-term credit. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3521-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 26 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3574-108585 + Details
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- Definition Amount of cash inflow (outflow) of investing activities, excluding discontinued operations. Investing activity cash flows include making and collecting loans and acquiring and disposing of debt or equity instruments and property, plant, and equipment and other productive assets. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3521-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 26 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3574-108585 + Details
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- Definition Amount of cash inflow (outflow) from operating activities, excluding discontinued operations. Operating activity cash flows include transactions, adjustments, and changes in value not defined as investing or financing activities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 24 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3521-108585 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 25 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3536-108585 + Details
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- Definition The cash outflow for incremental, external costs directly pertaining to an early extinguishment of debt, including legal costs and prepayment penalties, and excluding interest and repayment of debt principal. + References No definition available. + Details
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- Definition The cash outflow for loan and debt issuance costs. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3291-108585 + Details
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- Definition The cash outflow associated with the acquisition of a business, net of the cash acquired from the purchase. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3213-108585 + Details
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- Definition The cash outflow associated with the purchase of all investments (debt, security, other) during the period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3213-108585 + Details
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- Definition The cash outflow associated with the acquisition of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale; includes cash outflows to pay for construction of self-constructed assets. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3213-108585 + Details
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- Definition The cash inflow from the additional capital contribution to the entity. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3255-108585 + Details
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- Definition The cash inflow associated with security instrument that either represents a creditor or an ownership relationship with the holder of the investment security with a maturity of beyond one year or normal operating cycle, if longer. Includes proceeds from (a) debt, (b) capital lease obligations, (c) mandatory redeemable capital securities, and (d) any combination of (a), (b), or (c). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -Subparagraph (a),(b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3255-108585 + Details
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- Definition The total cash inflow associated with the amount received from holders to acquire the entity's shares under incentive and share awards, including stock option exercises. This item inherently excludes any excess tax benefit, which the entity may have realized and reported separately. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3255-108585 + Details
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- Definition Amount of cash inflow from a noncontrolling interest. Includes, but is not limited to, purchase of additional shares or other increase in noncontrolling interest ownership. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3255-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 + Details
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- Definition The net cash inflow or outflow from other financing activities. This element is used when there is not a more specific and appropriate element in the taxonomy. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3095-108585 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 9 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3098-108585 + Details
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- Definition The net cash inflow or outflow from cash and cash items that are not available for withdrawal or usage. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3255-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3291-108585 + Details
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- Definition The cash inflow associated with the sale of equity method investments, which are investments in joint ventures and entities in which the entity has an equity ownership interest normally of 20 to 50 percent and exercises significant influence. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 12 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3179-108585 + Details
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- Definition The cash inflow from the sale of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 12 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3179-108585 + Details
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