XML 129 R69.htm IDEA: XBRL DOCUMENT v2.4.1.9

Goodwill and Intangible Assets - Schedule of Activity and Balances Related to Goodwill (Detail) (USD $) In Thousands, unless otherwise specified	8 Months Ended	12 Months Ended
	Dec. 31, 2014	Apr. 30, 2014	Apr. 30, 2013	Apr. 30, 2012
Goodwill And Intangible Assets [Line Items]
Goodwill, beginning balance	$ 119,139us-gaap_Goodwill	$ 115,928us-gaap_Goodwill	$ 101,706us-gaap_Goodwill
Acquisitions	31us-gaap_GoodwillAcquiredDuringPeriod	3,183us-gaap_GoodwillAcquiredDuringPeriod	14,222us-gaap_GoodwillAcquiredDuringPeriod
Other		28us-gaap_GoodwillOtherChanges
Goodwill, ending balance	119,170us-gaap_Goodwill	119,139us-gaap_Goodwill	115,928us-gaap_Goodwill
Recycling [Member]
Goodwill And Intangible Assets [Line Items]
Goodwill, beginning balance	12,315us-gaap_Goodwill / us-gaap_StatementBusinessSegmentsAxis = cwst_RecyclingMember	12,190us-gaap_Goodwill / us-gaap_StatementBusinessSegmentsAxis = cwst_RecyclingMember		12,190us-gaap_Goodwill / us-gaap_StatementBusinessSegmentsAxis = cwst_RecyclingMember
Acquisitions		125us-gaap_GoodwillAcquiredDuringPeriod / us-gaap_StatementBusinessSegmentsAxis = cwst_RecyclingMember
Goodwill, ending balance	12,315us-gaap_Goodwill / us-gaap_StatementBusinessSegmentsAxis = cwst_RecyclingMember	12,315us-gaap_Goodwill / us-gaap_StatementBusinessSegmentsAxis = cwst_RecyclingMember		12,190us-gaap_Goodwill / us-gaap_StatementBusinessSegmentsAxis = cwst_RecyclingMember
Other [Member]
Goodwill And Intangible Assets [Line Items]
Goodwill, beginning balance	1,729us-gaap_Goodwill / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember
Acquisitions		1,729us-gaap_GoodwillAcquiredDuringPeriod / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember
Goodwill, ending balance	1,729us-gaap_Goodwill / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember	1,729us-gaap_Goodwill / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember
Eastern Region [Member]
Goodwill And Intangible Assets [Line Items]
Goodwill, beginning balance	17,429us-gaap_Goodwill / us-gaap_StatementGeographicalAxis = cwst_EasternRegionMember	16,858us-gaap_Goodwill / us-gaap_StatementGeographicalAxis = cwst_EasternRegionMember	58us-gaap_Goodwill / us-gaap_StatementGeographicalAxis = cwst_EasternRegionMember
Acquisitions		539us-gaap_GoodwillAcquiredDuringPeriod / us-gaap_StatementGeographicalAxis = cwst_EasternRegionMember	12,939us-gaap_GoodwillAcquiredDuringPeriod / us-gaap_StatementGeographicalAxis = cwst_EasternRegionMember
Other		32us-gaap_GoodwillOtherChanges / us-gaap_StatementGeographicalAxis = cwst_EasternRegionMember	3,861us-gaap_GoodwillOtherChanges / us-gaap_StatementGeographicalAxis = cwst_EasternRegionMember
Goodwill, ending balance	17,429us-gaap_Goodwill / us-gaap_StatementGeographicalAxis = cwst_EasternRegionMember	17,429us-gaap_Goodwill / us-gaap_StatementGeographicalAxis = cwst_EasternRegionMember	16,858us-gaap_Goodwill / us-gaap_StatementGeographicalAxis = cwst_EasternRegionMember
Western Region [Member]
Goodwill And Intangible Assets [Line Items]
Goodwill, beginning balance	87,666us-gaap_Goodwill / us-gaap_StatementGeographicalAxis = cwst_WesternRegionMember	86,880us-gaap_Goodwill / us-gaap_StatementGeographicalAxis = cwst_WesternRegionMember	89,458us-gaap_Goodwill / us-gaap_StatementGeographicalAxis = cwst_WesternRegionMember
Acquisitions	31us-gaap_GoodwillAcquiredDuringPeriod / us-gaap_StatementGeographicalAxis = cwst_WesternRegionMember	790us-gaap_GoodwillAcquiredDuringPeriod / us-gaap_StatementGeographicalAxis = cwst_WesternRegionMember	1,283us-gaap_GoodwillAcquiredDuringPeriod / us-gaap_StatementGeographicalAxis = cwst_WesternRegionMember
Other		(4)us-gaap_GoodwillOtherChanges / us-gaap_StatementGeographicalAxis = cwst_WesternRegionMember	(3,861)us-gaap_GoodwillOtherChanges / us-gaap_StatementGeographicalAxis = cwst_WesternRegionMember
Goodwill, ending balance	$ 87,697us-gaap_Goodwill / us-gaap_StatementGeographicalAxis = cwst_WesternRegionMember	$ 87,666us-gaap_Goodwill / us-gaap_StatementGeographicalAxis = cwst_WesternRegionMember	$ 86,880us-gaap_Goodwill / us-gaap_StatementGeographicalAxis = cwst_WesternRegionMember

X

- Details

Name:	cwst_GoodwillAndIntangibleAssetsLineItems
Namespace Prefix:	cwst_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

+ Details

Name:	us-gaap_Goodwill
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

+ Details

Name:	us-gaap_GoodwillAcquiredDuringPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

Amount of other (increase) decrease of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (g)

-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

+ Details

Name:	us-gaap_GoodwillOtherChanges
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=cwst_RecyclingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=us-gaap_AllOtherSegmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_StatementGeographicalAxis=cwst_EasternRegionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_StatementGeographicalAxis=cwst_WesternRegionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: