Jointly Owned Generation Units (Details)	Dec. 31, 2017 USD ($) MW	Apr. 13, 2016 USD ($)
Jointly Owned Utility Plant Interests [Line Items]
Utility plant in service	$ 257,285,000
Accumulated depreciation	18,205,000
Construction work in progress	5,093,000
Rodemacher Unit #2 [Member]
Jointly Owned Utility Plant Interests [Line Items]
Utility plant in service	72,129,000
Accumulated depreciation	3,111,000
Construction work in progress	$ 436,000
Ownership interest percentage (in hundredths)	30.00%
Jointly Owned Utility Plant, Nameplate Capacity of Generation Unit \| MW	523
Ownership interest (MW) \| MW	157
Dolet Hills [Member]
Jointly Owned Utility Plant Interests [Line Items]
Utility plant in service	$ 185,156,000
Accumulated depreciation	15,094,000
Construction work in progress	$ 4,657,000
Ownership interest percentage (in hundredths)	50.00%
Jointly Owned Utility Plant, Nameplate Capacity of Generation Unit \| MW	650
Ownership interest (MW) \| MW	325
Successor [Member]
Jointly Owned Utility Plant Interests [Line Items]
Accumulated depreciation		$ 0
Cleco Power [Member]
Jointly Owned Utility Plant Interests [Line Items]
Utility plant in service	$ 548,962,000
Accumulated depreciation	309,881,000
Construction work in progress	5,093,000
Cleco Power [Member] \| Rodemacher Unit #2 [Member]
Jointly Owned Utility Plant Interests [Line Items]
Utility plant in service	146,309,000
Accumulated depreciation	77,291,000
Construction work in progress	$ 436,000
Ownership interest percentage (in hundredths)	30.00%
Jointly Owned Utility Plant, Nameplate Capacity of Generation Unit \| MW	523
Ownership interest (MW) \| MW	157
Cleco Power [Member] \| Dolet Hills [Member]
Jointly Owned Utility Plant Interests [Line Items]
Utility plant in service	$ 402,653,000
Accumulated depreciation	232,590,000
Construction work in progress	$ 4,657,000
Ownership interest percentage (in hundredths)	50.00%
Jointly Owned Utility Plant, Nameplate Capacity of Generation Unit \| MW	650
Ownership interest (MW) \| MW	325

The capacity (in megawatts) of the jointly owned generation unit.

No definition available.

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Namespace Prefix:	cnl_
Data Type:	num:powerItemType
Balance Type:	na
Period Type:	instant

- Definition

The entity's ownership interest in the generation unit's name plate capacity (in megawatts).

+ References

No definition available.

+ Details

Name:	cnl_JointlyOwnedUtilityPlantOwnershipShareOfCapacity
Namespace Prefix:	cnl_
Data Type:	num:powerItemType
Balance Type:	na
Period Type:	instant

- Definition

The period end amount owned by the reporting utility of a jointly owned utility plant in service.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 980
-SubTopic 360
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 10.C)
-URI http://asc.fasb.org/extlink&oid=6500719&loc=d3e659983-123033

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- 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

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

- Definition

The period end amount of construction work in progress at a jointly owned electricity generation plant.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The period end amount of accumulated depreciation in a jointly owned electricity generation plant.

+ References

+ Details

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

- Definition

The proportionate share of interest (percent) in a jointly owned utility plant.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
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Period Type:	instant

- Details

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Namespace Prefix:
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- Details

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Namespace Prefix:
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- Details

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- Details

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Namespace Prefix:
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