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INCOME TAXES (Unrecognized Tax Benefits) (Details) (USD $)
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Sep. 30, 2014
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]        
Unrecognized tax benefits at beginning of year $ 1,304,000us-gaap_UnrecognizedTaxBenefits $ 3,543,000us-gaap_UnrecognizedTaxBenefits $ 36,217,000us-gaap_UnrecognizedTaxBenefits $ 5,400,000us-gaap_UnrecognizedTaxBenefits
Additions to current year tax positions 419,000us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions 0us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions 0us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromPriorPeriodTaxPositions  
Unrecognized Tax Benefits, Increase Resulting from Acquisition 0us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromAcquisition 0us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromAcquisition 2,652,000us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromAcquisition  
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities 0us-gaap_UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities 0us-gaap_UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities 0us-gaap_UnrecognizedTaxBenefitsDecreasesResultingFromSettlementsWithTaxingAuthorities  
Additions due to acquisitions 904,000us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions 210,000us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions 0us-gaap_UnrecognizedTaxBenefitsIncreasesResultingFromCurrentPeriodTaxPositions  
Statute expiration 0us-gaap_UnrecognizedTaxBenefitsReductionsResultingFromLapseOfApplicableStatuteOfLimitations (2,843,000)us-gaap_UnrecognizedTaxBenefitsReductionsResultingFromLapseOfApplicableStatuteOfLimitations (35,328,000)us-gaap_UnrecognizedTaxBenefitsReductionsResultingFromLapseOfApplicableStatuteOfLimitations  
Foreign currency translation (90,000)us-gaap_ForeignCurrencyTransactionGainLossUnrealized 394,000us-gaap_ForeignCurrencyTransactionGainLossUnrealized 2,000us-gaap_ForeignCurrencyTransactionGainLossUnrealized  
Unrecognized tax benefits at end of year 2,537,000us-gaap_UnrecognizedTaxBenefits 1,304,000us-gaap_UnrecognizedTaxBenefits 3,543,000us-gaap_UnrecognizedTaxBenefits 5,400,000us-gaap_UnrecognizedTaxBenefits
Unrecognized tax benefits, income tax penalties and interest accrued 400,000us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued 200,000us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued 1,400,000us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestAccrued  
Unrecognized tax benefits, income tax penalties and interest expense 300,000us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense 300,000us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense 2,800,000us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense  
Expiring of statutes of limitations        
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]        
Statute expiration $ (300,000)us-gaap_UnrecognizedTaxBenefitsReductionsResultingFromLapseOfApplicableStatuteOfLimitations
/ us-gaap_ReasonablyPossibleSignificantChangeInUnrecognizedTaxBenefitsByItemAxis
= clh_ExpiringOfStatutesOfLimitationsMember