Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Cash Flows from Operating Activities:
Net loss	$ (7,963)us-gaap_ProfitLoss	$ (13,610)us-gaap_ProfitLoss
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Depreciation and amortization	13,748	13,608
Depletion of landfill operating lease obligations	1,690	1,992
Interest accretion on landfill and environmental remediation liabilities	848	1,017
Stock-based compensation	660us-gaap_ShareBasedCompensation	576us-gaap_ShareBasedCompensation
Amortization of discount on long-term debt	80	62
Divestiture transactions	(4,935)cwst_DivestitureTransactions
Gain on sale of property and equipment	(46)	(185)
Development project charge		1,440us-gaap_NoncashProjectAbandonmentCosts
Gain on settlement of acquisition related contingent consideration		(1,058)
Loss on debt extinguishment	521
Loss on derivative instruments	151	150
Income from equity method investments		(27)
Loss on sale of equity method investment		221
Deferred income taxes	(49)us-gaap_DeferredIncomeTaxExpenseBenefit	243us-gaap_DeferredIncomeTaxExpenseBenefit
Changes in assets and liabilities, net of effects of acquisitions and divestitures:
Accounts receivable	3,237	3,764
Accounts payable	(9,108)	(2,953)
Prepaid expenses, inventories and other assets	4,341	1,743
Accrued expenses and other liabilities	(8,870)	(5,622)
Net cash (used in) provided by operating activities	(5,695)	1,361
Cash Flows from Investing Activities:
Proceeds from settlement of contingent consideration		214us-gaap_ProceedsFromPreviousAcquisition
Additions to property, plant and equipment	(4,444)	(7,477)
Payments on landfill operating lease contracts	(478)cwst_PaymentsForLandfillOperatingLease	(563)cwst_PaymentsForLandfillOperatingLease
Payments related to investments		(84)us-gaap_PaymentsToAcquireInvestments
Proceeds from divestiture transactions	4,550
Proceeds from sale of property and equipment	89	216
Net cash used in investing activities	(283)	(7,773)
Cash Flows from Financing Activities:
Proceeds from long-term borrowings	197,591	47,860
Principal payments on long-term debt	(186,500)	(41,250)
Change in restricted cash	4,086
Payments of financing costs	(6,852)us-gaap_PaymentsOfFinancingCosts	(17)us-gaap_PaymentsOfFinancingCosts
Distribution to noncontrolling interest holder	(1,495)us-gaap_PaymentsToMinorityShareholders
Net cash provided by (used in) financing activities	6,830	6,593
Discontinued Operations:
Net cash provided by investing activities		86
Net cash provided by discontinued operations		86
Net increase in cash and cash equivalents	852	267
Cash and cash equivalents, beginning of period	2,205	2,695
Cash and cash equivalents, end of period	3,057	2,962
Cash paid during the period for:
Interest	15,336us-gaap_InterestPaidNet	14,959us-gaap_InterestPaidNet
Income taxes, net of refunds	30us-gaap_IncomeTaxesPaidNet	500us-gaap_IncomeTaxesPaidNet
Acquisition [Member]
Cash Flows from Investing Activities:
Additions to property, plant and equipment	$ (4,444)	$ (79)

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- Definition

The cash inflow from a debt initially having maturity due after one year or beyond the operating cycle, if longer.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Financing Activities

-URI http://asc.fasb.org/extlink&oid=6513228

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 14

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3255-108585

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- Definition

Cash inflow representing an adjustment to the purchase price of a previous acquisition.

+ References

No definition available.

+ Details

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- Definition

The net cash inflow or outflow from cash and cash items that are not available for withdrawal or usage.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 14

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3255-108585

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-Publisher FASB

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-Topic 230

-SubTopic 10

-Section 45

-Paragraph 15

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3291-108585

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- Definition

The cash inflow from the sale of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Investing Activities

-URI http://asc.fasb.org/extlink&oid=6516133

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-Publisher FASB

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-Topic 230

-SubTopic 10

-Section 45

-Paragraph 12

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3179-108585

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- Definition

Aggregate cash proceeds received from a combination of transactions in which noncurrent assets are sold, which may include the sale of a business, an investment in an affiliate (including an equity method investee), property, plant and equipment and intangible assets. Excludes sales of trading, available-for-sale, and held-to-maturity securities.

+ References

No definition available.

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- Definition

The consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 55

-Paragraph 4K

-URI http://asc.fasb.org/extlink&oid=35736750&loc=SL4591552-111686

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 45

-Paragraph 19

-URI http://asc.fasb.org/extlink&oid=7656940&loc=SL4569616-111683

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 50

-Paragraph 1A

-Subparagraph (a),(c)

-URI http://asc.fasb.org/extlink&oid=18733093&loc=SL4573702-111684

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-Topic 810

-SubTopic 10

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-Paragraph 4J

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- Definition

The cash outflow associated with security instruments that either represent a creditor or an ownership relationship with the holder of the investment security with a maturity of beyond one year or normal operating cycle, if longer. Includes repayments of (a) debt, (b) capital lease obligations, (c) mandatory redeemable capital securities, and (d) any combination of (a), (b), or (c).

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Financing Activities

-URI http://asc.fasb.org/extlink&oid=6513228

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-Publisher FASB

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-Topic 230

-SubTopic 10

-Section 45

-Paragraph 15

-Subparagraph (a),(b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3291-108585

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- Definition

The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method.

+ References

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