XML 21 R57.htm IDEA: XBRL DOCUMENT
v2.4.0.6

Development Project Charge (Narrative) (Detail) (USD $) In Thousands, unless otherwise specified | 9 Months Ended |  |
--- | --- | --- | ---
Jan. 31, 2012 | Jan. 31, 2013 | Apr. 30, 2012
Collaborative Arrangements Non collaborative Arrangements And Business Acquisitions Transactions [Line Items] |  |  |
Deferred costs associated with development projects | $ 131 |  |
Deferred project costs |  | $ 1,554 | $ 1,163

X
- Definition Amount recognized as an operating expense or loss during the period to write-off the deferred costs associated with development projects no longer deemed viable. + References No definition available. + Details
Name: | cwst_AbandonedDevelopmentProjectExpense
Namespace Prefix: | cwst_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | cwst_CollaborativeArrangementsNonCollaborativeArrangementsAndBusinessAcquisitionsTransactionsLineItems
Namespace Prefix: | cwst_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Capitalized costs related to projects that are ongoing. + References No definition available. + Details
Name: | cwst_DeferredProjectCosts
Namespace Prefix: | cwst_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant