XML 63 R49.htm IDEA: XBRL DOCUMENT
v3.8.0.1

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Landfill Accounting (Detail) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2017 USD ($) Agreement | Dec. 31, 2016 USD ($) | Dec. 31, 2015 USD ($)
Property, Plant and Equipment [Line Items] |  |  |
Capitalized interest | $ 295 | $ 273 | $ 62
Closure and post-closure costs incurrence period | 30 years |  |
Estimate of inflation rate | 1.70% |  |
Accretion expense | $ 4,401 | 3,606 |
Number of operation and management agreements entered into | Agreement | 5 |  |
Closure And Post Closure Costs |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Accretion expense | $ 4,401 | 3,606 | $ 3,370
Surety bond | 164,893 | 161,095 |
Letters of credit | $ 0 | $ 0 |
Minimum |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Rate of asset retirement obligation | 9.20% |  |
Maximum |  |  |
Property, Plant and Equipment [Line Items] |  |  |
Rate of asset retirement obligation | 9.90% |  |

X
- Definition Closure and Post-Closure Costs Incurrence Period + References No definition available. + Details
Name: | cwst_ClosureandPostClosureCostsIncurrencePeriod
Namespace Prefix: | cwst_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Estimated inflation rate. + References No definition available. + Details
Name: | cwst_InflationRate
Namespace Prefix: | cwst_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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

X
- Definition Amount of surety bonds that are available for the future payment of landfill capping, closure and post-closure obligations. + References No definition available. + Details
Name: | cwst_SuretyBonds
Namespace Prefix: | cwst_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of accretion expense recognized during the period that is associated with an asset retirement obligation. Accretion expense measures and incorporates changes due to the passage of time into the carrying amount of the liability. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c)(3) -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6392676&loc=d3e7480-110848 + Details
Name: | us-gaap_AssetRetirementObligationAccretionExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Interest rate used to find the present value of an amount to be paid or received in the future as an input to measure fair value. For example, but not limited to, weighted average cost of capital (WACC), cost of capital, cost of equity and cost of debt. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (bbb) -URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueInputsDiscountRate
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of interest capitalized during the period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6450988&loc=d3e26243-108391 + Details
Name: | us-gaap_InterestCostsCapitalized
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The total amount of the contingent obligation under letters of credit outstanding as of the reporting date. + References No definition available. + Details
Name: | us-gaap_LettersOfCreditOutstandingAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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_PropertyPlantAndEquipmentLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_PropertyPlantAndEquipmentByTypeAxis=cwst_ClosureAndPostClosureCostsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |