-- None. No documentation exists for this element. --

No definition available.

Name:	clh_LegalAndAdministrativeProceedingsAbstract
Namespace Prefix:	clh_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount as of the balance sheet date of potential needed increase in the loss contingency reserves.

+ References

No definition available.

+ Details

Name:	clh_LossContingencyAccrualAtCarryingValuePotentialAdditionalLiability
Namespace Prefix:	clh_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Loss Contingency, General Damages Sought, Value

+ References

No definition available.

+ Details

Name:	clh_LossContingencyGeneralDamagesSoughtValue
Namespace Prefix:	clh_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Loss Contingency, Punitive Damages Sought, Value

+ References

No definition available.

+ Details

Name:	clh_LossContingencyPunitiveDamagesSoughtValue
Namespace Prefix:	clh_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The estimated minimum amount of possible loss from the federal and state enforcement actions.

+ References

No definition available.

+ Details

Name:	clh_LossContingencyRangeOfLoss
Namespace Prefix:	clh_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

This element represents the number of municipalities other than Ville Mercier that filed legal proceedings against the Mercier Subsidiary.

+ References

No definition available.

+ Details

Name:	clh_NumberOfNeighboringMunicipalitiesFilingSeparateLegalProceedings
Namespace Prefix:	clh_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of permits that are granted by the government in relation to environmental liabilities.

+ References

No definition available.

+ Details

Name:	clh_NumberOfPermitsIssuedByGovernmentToDumpOrganicLiquid
Namespace Prefix:	clh_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of loss contingency liability.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14326-108349

+ Details

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

- Definition

The number of claims settled and dismissed during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14435-108349

+ Details

Name:	us-gaap_LossContingencyClaimsSettledAndDismissedNumber
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of pending claims pertaining to a loss contingency.

+ References

+ Details

Name:	us-gaap_LossContingencyPendingClaimsNumber
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_BusinessAcquisitionAxis=clh_SafetyKleenMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	clh_ContingenciesByNatureOfContingencyAxis=clh_LegalAndAdministrativeProceedingsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	clh_ContingenciesByNatureOfContingencyAxis=clh_VilleMercierMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	clh_ContingenciesByNatureOfContingencyAxis=clh_FederalAndStateEnforcementActionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

COMMITMENTS AND CONTINGENCIES (Legal and Administrative Proceedings) (Details) CAD in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) claim proceeding	Dec. 31, 2012 CAD	Dec. 31, 1999 municipality	Dec. 31, 1968 permit	Dec. 31, 2016 USD ($)
Legal and Administrative Proceedings
Reserves	$ 19.3				$ 22.0
Safety-Kleen
Legal and Administrative Proceedings
Number of proceedings \| proceeding	52
Loss contingency, claims settled and dismissed, claims \| claim	33
Legal and Administrative Proceedings
Legal and Administrative Proceedings
Reserves	$ 17.9				18.2
Possible increase in legal and administrative proceedings	1.8				1.9
Ville Mercier
Legal and Administrative Proceedings
Number of permits issued by government, for dumping organic liquid \| permit				2
Number of neighboring municipalities filing separate legal proceedings against the Mercier subsidiary and the government of Quebec \| municipality			3
General damages sought \| CAD		CAD 2.9
Punitive damages sought \| CAD		CAD 10.0
Federal, State, and Provincial Enforcement Actions
Legal and Administrative Proceedings
Reserves relating to legal and administrative proceedings	$ 1.4				$ 3.8
Number of proceedings \| proceeding	5