Business Combinations - Narrative (Details)		1 Months Ended	3 Months Ended	12 Months Ended
	Feb. 04, 2019 USD ($) cooperative investor_owned_utility municipality MW	Jan. 31, 2019 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Business Acquisition [Line Items]
Proceeds from long-term lines of credit				$ 238,000,000	$ 108,000,000	$ 0
Regulated operating revenue, electric, non-nuclear				1,370,893,000	1,496,736,000	1,181,907,000
Decrease in other operating income				(180,524,000)	(182,832,000)	(82,332,000)
Depreciation expense				219,363,000	216,320,000	170,414,000
Power supply agreements
Business Acquisition [Line Items]
Business combination, finite-lived intangibles	$ 98,900,000
Power supply agreements
Business Acquisition [Line Items]
Business combination, recognized identifiable assets and intangible liabilities	14,200,000
NRG South Central
Business Acquisition [Line Items]
Repayments of long-term debt	400,000,000.0	$ 400,000,000.0
Business combination, liabilities arising from contingencies, amount recognized	10,000,000.0
Business combination, indemnification assets, amount as of acquisition date	10,000,000.0
Purchase price consideration	962,200,000
Cash paid	1,000,000,000.0
Working capital adjustment	37,800,000
Business combination, finite-lived intangibles	98,900,000
Business combination, recognized identifiable assets and intangible liabilities	38,300,000
Business combination, deferred revenue	58,300,000
Net income					154,898,000	170,224,000
NRG South Central | Fair Value Adjustments
Business Acquisition [Line Items]
Regulated operating revenue, electric, non-nuclear			$ 500,000
Decrease in other operating income			100,000
Depreciation expense			$ 200,000
NRG South Central | Acquisition-related Costs
Business Acquisition [Line Items]
Net income					4,700,000
NRG South Central | Power supply agreements
Business Acquisition [Line Items]
Business combination, recognized identifiable assets and intangible liabilities	14,200,000
NRG South Central | LTSA
Business Acquisition [Line Items]
Business combination, recognized identifiable assets and intangible liabilities	$ 24,100,000
Cleco Cajun
Business Acquisition [Line Items]
Number of customers served | investor_owned_utility	1
CLECO POWER
Business Acquisition [Line Items]
Public utilities, requested rate increase (decrease), amount		$ (4,000,000.0)
Proceeds from long-term lines of credit				150,000,000	33,000,000	0
Regulated operating revenue, electric, non-nuclear				1,015,018,000	1,130,928,000	1,191,587,000
Decrease in other operating income				(65,237,000)	(72,833,000)	(82,330,000)
Depreciation expense				$ 166,987,000	$ 172,471,000	$ 162,069,000
Cleco Holdings
Business Acquisition [Line Items]
Debt instrument, term	3 years
Debt to capital ratio	0.65
Cleco Holdings | Revolving Credit Facility
Business Acquisition [Line Items]
Proceeds from credit facility	$ 75,000,000.0
Line of credit facility, maximum borrowing capacity	175,000,000.0
Proceeds from long-term lines of credit	75,000,000.0
Cleco Holdings | Bridge Loan
Business Acquisition [Line Items]
Debt instrument, face amount	300,000,000.0
Cleco Holdings | Loans Payable
Business Acquisition [Line Items]
Debt instrument, face amount	100,000,000.0
Cleco Holdings | NRG South Central
Business Acquisition [Line Items]
Cash paid	102,300,000
Cleco Group | NRG South Central
Business Acquisition [Line Items]
Business combination, equity interests issued and issuable	$ 384,900,000
Sterlington, Louisiana | Natural-gas-fired Generating Station | Cleco Cajun
Business Acquisition [Line Items]
Number of megawatts in station or facility (mw) | MW	176
Jarreau, Louisiana | Natural-gas-fired Facility | Cleco Cajun
Business Acquisition [Line Items]
Number of megawatts in station or facility (mw) | MW	220
Jarreau, Louisiana | Natural-gas-fired Peaking Facility | Cleco Cajun
Business Acquisition [Line Items]
Number of megawatts in station or facility (mw) | MW	210
New Roads, Louisiana | Natural-gas-fired Generating Station | Cleco Cajun
Business Acquisition [Line Items]
Number of megawatts in station or facility (mw) | MW	540
New Roads, Louisiana | Coal-fired Generating Facility | Cleco Cajun
Business Acquisition [Line Items]
Number of megawatts in station or facility (mw) | MW	580
New Roads, Louisiana | Coal-fired Generating Station | Cleco Cajun | Jointly Owned Electricity Generation Plant
Business Acquisition [Line Items]
Number of megawatts in station or facility (mw) | MW	588
Ownership interest percentage	58.00%
Jennings, Louisiana | Cleco Cajun
Business Acquisition [Line Items]
Number of megawatts in station or facility (mw) | MW	225
Jennings, Louisiana | Natural-gas-fired Peaking Facility | Cleco Cajun
Business Acquisition [Line Items]
Number of megawatts in station or facility (mw) | MW	300
Deweyville, Texas | Natural-gas-fired Generating Station | Cleco Cajun
Business Acquisition [Line Items]
Number of megawatts in station or facility (mw) | MW	1,263
Louisiana | Cleco Cajun
Business Acquisition [Line Items]
Number of customers served | cooperative	9
Arkansas, Louisiana, And Texas | Cleco Cajun
Business Acquisition [Line Items]
Number of customers served | municipality	5