CLOSURE AND POST-CLOSURE LIABILITIES (Details) $ in Thousands	9 Months Ended
Sep. 30, 2020 USD ($) facility
Changes to post-closure liabilities
Balance at January 1, 2020	$ 75,651
Liabilities assumed in acquisitions	265
New asset retirement obligations	1,643
Accretion	4,889
Changes in estimates recorded to statement of operations	4,489
Changes in estimates recorded to balance sheet	194
Expenditures	(2,738)
Currency translation and other	(177)
Balance at September 30, 2020	$ 84,216
Number of active landfill facilities \| facility	10
Credit-adjusted risk-free rate	5.60%
Landfill Retirement Liability
Changes to post-closure liabilities
Balance at January 1, 2020	$ 39,401
Liabilities assumed in acquisitions	0
New asset retirement obligations	1,643
Accretion	2,373
Changes in estimates recorded to statement of operations	4,503
Changes in estimates recorded to balance sheet	179
Expenditures	(2,116)
Currency translation and other	(133)
Balance at September 30, 2020	45,850
Non-Landfill Retirement Liability
Changes to post-closure liabilities
Balance at January 1, 2020	36,250
Liabilities assumed in acquisitions	265
New asset retirement obligations	0
Accretion	2,516
Changes in estimates recorded to statement of operations	(14)
Changes in estimates recorded to balance sheet	15
Expenditures	(622)
Currency translation and other	(44)
Balance at September 30, 2020	$ 38,366

Asset Retirement Obligation Changes Recorded in Balance Sheet

No definition available.

Name:	clh_AssetRetirementObligationChangesRecordedInBalanceSheet
Namespace Prefix:	clh_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The amount of change in the asset retirement obligation, during the current period, for changes in estimates recorded in the statement of income.

+ References

No definition available.

+ Details

Name:	clh_AssetRetirementObligationChangesRecordedInStatementOfIncome
Namespace Prefix:	clh_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Asset Retirement Obligation Liabilities Assumed in Acquisition

+ References

No definition available.

+ Details

Name:	clh_AssetRetirementObligationLiabilitiesAssumedInAcquisition
Namespace Prefix:	clh_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Asset Retirement Obligations Discount Rate

+ References

No definition available.

+ Details

Name:	clh_AssetRetirementObligationsDiscountRate
Namespace Prefix:	clh_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Number Of Active Landfill Facilities

+ References

No definition available.

+ Details

Name:	clh_NumberOfActiveLandfillFacilities
Namespace Prefix:	clh_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

The carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees.

+ References

+ Details

Name:	us-gaap_AssetRetirementObligation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of accretion expense recognized during the period that is associated with an asset retirement obligation. Accretion expense measures and incorporates changes due to the passage of time into the carrying amount of the liability.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)(3)
-URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6392676&loc=d3e7480-110848

+ Details

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

- Definition

Amount of foreign currency translation gain (loss) which decreases (increases) asset retirement obligations.

+ References

+ Details

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

- Definition

Amount of asset retirement obligations incurred during the period.

+ References

+ Details

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

- Definition

Amount of asset retirement obligations settled, or otherwise disposed of, during the period. This may include asset retirement obligations transferred to third parties associated with the sale of a long-lived asset.

+ References

+ Details

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

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

Name:	us-gaap_AssetRetirementObligationRollForwardAnalysisRollForward
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	clh_ClosureAndPostClosureLiabilitiesAxis=clh_LandfillRetirementLiabilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	clh_ClosureAndPostClosureLiabilitiesAxis=clh_NonLandfillRetirementLiabilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: