XML 126 R51.htm IDEA: XBRL DOCUMENT
v2.4.0.8

Summary of Significant Accounting Policies - Cash and Cash Equivalents - Additional Information (Detail) | 12 Months Ended
--- | ---
Apr. 30, 2014
Accounting Policies [Abstract] |
Maximum cash equivalents maturity period | Three months

X
- Definition Maturity for a highly liquid investment to be considered a cash equivalent. + References No definition available. + Details
Name: | cwst_CashAndCashEquivalentMaximumMaturity
Namespace Prefix: | cwst_
Data Type: | us-types:durationStringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_AccountingPoliciesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration