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Other Items - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified | 3 Months Ended |  |
--- | --- | --- | ---
Mar. 31, 2014 | Mar. 31, 2015 | Dec. 31, 2014
Asset Retirement Obligation [Line Items] |  |  |
Development project charges | $ 1,440 us-gaap_NoncashProjectAbandonmentCosts |  |
Deferred project costs |  | 0 us-gaap_OtherDeferredCostsGross | 0 us-gaap_OtherDeferredCostsGross
Gain on settlement of acquisition related contingent consideration | (1,058)us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1 |  |
Industrial Service Management Business [Member] |  |  |
Asset Retirement Obligation [Line Items] |  |  |
Gain on settlement of acquisition related contingent consideration | 1,058 us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1 / us-gaap_BusinessAcquisitionAxis = cwst_IndustrialServiceManagementBusinessMember |  |
Maine Energy Facility [Member] |  |  |
Asset Retirement Obligation [Line Items] |  |  |
Development project charges | $ 1,440 us-gaap_NoncashProjectAbandonmentCosts / us-gaap_SignificantAcquisitionsAndDisposalsByTransactionAxis = cwst_MaineEnergyFacilityMember |  |

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- Definition Amount of increase (decrease) in the value of a contingent consideration liability, including, but not limited to, differences arising upon settlement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 50 -Paragraph 4 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e7008-128479 + Details
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- Definition The expense charged against earnings to eliminate the capitalized costs of projects that have been terminated during the reporting period, which is added back to net income when calculating cash provided by (used in) operations using the indirect method. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 + Details
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- Definition Gross amount of other deferred costs capitalized at the end of the reporting period. Does not include deferred finance costs or deferred acquisition costs of insurance companies. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.17) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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