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v2.4.1.9

Related Party Transactions - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified | 8 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2014 Lease | Dec. 31, 2013 | Apr. 30, 2014 | Apr. 30, 2013 | Apr. 30, 2012
Related Party Transaction [Line Items] |  |  |  |  |
Total services purchased | $ 5,562 us-gaap_RelatedPartyTransactionPurchasesFromRelatedParty |  | $ 7,818 us-gaap_RelatedPartyTransactionPurchasesFromRelatedParty | $ 6,574 us-gaap_RelatedPartyTransactionPurchasesFromRelatedParty | $ 2,612 us-gaap_RelatedPartyTransactionPurchasesFromRelatedParty
Outstanding accounts payable | 2 us-gaap_AccountsPayableRelatedPartiesCurrent |  | 890 us-gaap_AccountsPayableRelatedPartiesCurrent | 1,187 us-gaap_AccountsPayableRelatedPartiesCurrent |
Number of leases | 2 cwst_NumberOfLeases |  |  |  |
Capital lease expiration date | Apr. 30, 2023 |  |  |  |
Total expense charged to operations under lease agreement | 263 us-gaap_CapitalLeasesIncomeStatementAmortizationExpense |  | 386 us-gaap_CapitalLeasesIncomeStatementAmortizationExpense | 286 us-gaap_CapitalLeasesIncomeStatementAmortizationExpense | 300 us-gaap_CapitalLeasesIncomeStatementAmortizationExpense
Accrued costs associated with post-closure obligations | 39,829 us-gaap_AssetRetirementObligation |  | 44,654 us-gaap_AssetRetirementObligation | 43,170 us-gaap_AssetRetirementObligation | 39,629 us-gaap_AssetRetirementObligation
Loan to an employee outstanding |  |  | 149 us-gaap_NotesReceivableRelatedPartiesNoncurrent | 147 us-gaap_NotesReceivableRelatedPartiesNoncurrent |
Charges in general and administration to reserve for the notes | 45,732 us-gaap_GeneralAndAdministrativeExpense | 40,803 us-gaap_GeneralAndAdministrativeExpense | 61,865 us-gaap_GeneralAndAdministrativeExpense | 58,205 us-gaap_GeneralAndAdministrativeExpense | 60,264 us-gaap_GeneralAndAdministrativeExpense
Landfills [Member] |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |
Landfill owned | 2 cwst_NumberOfMajorShareholders / us-gaap_PropertyPlantAndEquipmentByTypeAxis = us-gaap_LandfillMember |  |  |  |
Landfill post-closure cost | 8 us-gaap_AssetRetirementObligationCashPaidToSettle / us-gaap_PropertyPlantAndEquipmentByTypeAxis = us-gaap_LandfillMember |  | 8 us-gaap_AssetRetirementObligationCashPaidToSettle / us-gaap_PropertyPlantAndEquipmentByTypeAxis = us-gaap_LandfillMember | 8 us-gaap_AssetRetirementObligationCashPaidToSettle / us-gaap_PropertyPlantAndEquipmentByTypeAxis = us-gaap_LandfillMember | 8 us-gaap_AssetRetirementObligationCashPaidToSettle / us-gaap_PropertyPlantAndEquipmentByTypeAxis = us-gaap_LandfillMember
Accrued costs associated with post-closure obligations | 84 us-gaap_AssetRetirementObligation / us-gaap_PropertyPlantAndEquipmentByTypeAxis = us-gaap_LandfillMember |  | 94 us-gaap_AssetRetirementObligation / us-gaap_PropertyPlantAndEquipmentByTypeAxis = us-gaap_LandfillMember | 100 us-gaap_AssetRetirementObligation / us-gaap_PropertyPlantAndEquipmentByTypeAxis = us-gaap_LandfillMember |
Cash [Member] | Southbridge Landfill [Member] |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |
Related party contributions on business divestitures | 350 cwst_CashRemediationSettlement / us-gaap_CashAndCashEquivalentsAxis = us-gaap_CashMember / us-gaap_EnvironmentalRemediationSiteAxis = cwst_SouthbridgeLandfillMember |  |  |  |
Non Cash [Member] | Southbridge Landfill [Member] |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |
Related party contributions on business divestitures | 390 cwst_NonCashRemediationSettlement / us-gaap_CashAndCashEquivalentsAxis = cwst_NonCashMember / us-gaap_EnvironmentalRemediationSiteAxis = cwst_SouthbridgeLandfillMember |  |  |  |
Allowance for Notes Receivable [Member] |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |
Charges in general and administration to reserve for the notes |  |  | 149 us-gaap_GeneralAndAdministrativeExpense / us-gaap_IncomeStatementLocationAxis = us-gaap_AllowanceForNotesReceivableMember |  |
Related Party [Member] |  |  |  |  |
Related Party Transaction [Line Items] |  |  |  |  |
Leases monthly payments | $ 27 us-gaap_DebtInstrumentPeriodicPayment / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = cwst_RelatedPartyMember |  |  |  |

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- Definition Amount for accounts payable to related parties. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(k)(1)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 850 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39622-107864 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 850 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39603-107864 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 08 -Paragraph k -Subparagraph 1 -Article 4 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 19 -Subparagraph a -Article 5 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(a)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 850 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864 + Details
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