Basis Of Presentation (Narrative) (Detail) (USD $) In Thousands, unless otherwise specified	1 Months Ended
Aug. 08, 2012	Aug. 01, 2012 Purchase And Sale Agreement [Member]
Purchase consideration		$ 6,650
Purchase consideration payment period		21 years
Severance and reorganization charge	$ 1,475

The charge against earnings in the period for known and estimated costs of termination benefits to current employees that are involuntary terminated.

No definition available.

Name:	cwst_SeveranceAndReorganizationCharge
Namespace Prefix:	cwst_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration