Amount to be collected annually from a regional transmission organization for system support resource payments.

No definition available.

Name:	cnl_Amounttobecollectedannuallyfromaregionaltransmissionorganization
Namespace Prefix:	cnl_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Effective Income Tax Rate Reconciliation, at Federal and State Statutory Income Tax Rate, Percent

+ References

No definition available.

+ Details

Name:	cnl_EffectiveIncomeTaxRateReconciliationatFederalandStateStatutoryIncomeTaxRatePercent
Namespace Prefix:	cnl_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Payments received for capital expenditures subject to refund

+ References

No definition available.

+ Details

Name:	cnl_Paymentsreceivedforcapitalexpendituressubjecttorefund
Namespace Prefix:	cnl_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The percentage of retail earnings to be returned to retail customers as ordered by the regulatory agency when the return on equity falls within a certain range.

+ References

No definition available.

+ Details

Name:	cnl_PublicUtilitiesReturnonEquityPercentageofretailearningsduetocustomerswithinrange
Namespace Prefix:	cnl_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The high range of the return on equity which triggers a retail customer partial refund obligation. All retail earnings must be returned to customers when the return on equity exceeds this high range.

+ References

No definition available.

+ Details

Name:	cnl_PublicUtilitiesReturnonequityforcustomerrefundhighrange
Namespace Prefix:	cnl_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The low range of the return on equity which triggers a retail customer partial refund obligation.

+ References

No definition available.

+ Details

Name:	cnl_PublicUtilitiesReturnonequityforcustomerrefundlowrange
Namespace Prefix:	cnl_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Tax Cuts and Jobs Act of 2017, Customer Refund Liability, Current

+ References

No definition available.

+ Details

Name:	cnl_TaxCutsandJobsActof2017CustomerRefundLiabilityCurrent
Namespace Prefix:	cnl_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Current regulatory liabilities generally represent obligations to make refunds to customers for various reasons including overpayment.

+ References

No definition available.

+ Details

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

- Definition

The total number of new claims filed pertaining to a loss contingency 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_LossContingencyNewClaimsFiledNumber
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of public utility's approved return on equity.

+ References

No definition available.

+ Details

Name:	us-gaap_PublicUtilitiesApprovedReturnOnEquityPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

- Details

Name:	dei_LegalEntityAxis=cnl_ClecoPowerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RegulatoryAgencyAxis=cnl_LouisianaPublicServiceCommissionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessCombinationSeparatelyRecognizedTransactionsAxis=cnl_MergerCommitmentscostsavingsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PublicUtilitiesRegulatoryProceedingAxis=cnl_MISOTransmissionRatesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RegulatoryAgencyAxis=cnl_FederalEnergyRegulatoryCommissionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PublicUtilitiesRegulatoryProceedingAxis=cnl_FRPMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PublicUtilitiesRegulatoryProceedingAxis=cnl_A2017FRPMonitoringreportMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PublicUtilitiesRegulatoryProceedingAxis=cnl_A2017MergerCommitmentMonitoringreportMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PublicUtilitiesRegulatoryProceedingAxis=cnl_SSRMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PublicUtilitiesRegulatoryProceedingAxis=cnl_SSR2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Regulation and Rates (Details)			1 Months Ended		3 Months Ended	45 Months Ended
Regulation and Rates (Details)	Jan. 01, 2018	Dec. 31, 2017 USD ($)	Sep. 30, 2016	Nov. 30, 2013	Mar. 31, 2018 USD ($) claim	Mar. 31, 2018 USD ($)	Oct. 31, 2017 USD ($)	Feb. 28, 2017 USD ($)
Regulation and Rates [Line Items]
Refund due to customers		$ 4,206,000			$ 11,805,000	$ 11,805,000
Tax Cuts and Jobs Act of 2017, customer refund liability					7,300,000	7,300,000
Federal and state combined statutory tax rate	26.00%	38.00%
Cleco Power
Regulation and Rates [Line Items]
Refund due to customers		$ 4,206,000			11,805,000	11,805,000
Payments received for capital expenditures subject to refund					4,300,000	4,300,000
Cleco Power \| LPSC \| Merger Commitments, cost savings
Regulation and Rates [Line Items]
Refund due to customers					$ 2,100,000	2,100,000
Cleco Power \| MISO Transmission Rates \| FERC
Regulation and Rates [Line Items]
Loss contingency, new claims filed, number \| claim					2
Refund due to customers					$ 2,100,000	$ 2,100,000		$ 1,200,000
Target ROE allowed by FRP (in hundredths)			10.32%	12.38%
Cleco Power \| FRP \| LPSC
Regulation and Rates [Line Items]
Target ROE allowed by FRP (in hundredths)						10.00%
Percentage of retail earnings within range to be returned to customers (in hundredths)						60.00%
ROE for customer credit, low range (in hundredths)						10.90%
ROE for customer credit, high range (in hundredths)						11.75%
Cleco Power \| FRP \| LPSC \| Maximum
Regulation and Rates [Line Items]
Target ROE allowed by FRP (in hundredths)						10.90%
Cleco Power \| 2017 FRP Monitoring report \| LPSC
Regulation and Rates [Line Items]
Refund due to customers							$ 0
Cleco Power \| 2017 Merger Commitment Monitoring report \| LPSC
Regulation and Rates [Line Items]
Tax Cuts and Jobs Act of 2017, customer refund liability							$ 1,200,000
Cleco Power \| SSR \| FERC
Regulation and Rates [Line Items]
Amount collected in SSR payments from MISO					20,300,000	$ 20,300,000
Cleco Power \| SSR 2 \| FERC
Regulation and Rates [Line Items]
Amount collected in SSR payments from MISO					$ 11,800,000	$ 11,800,000