Intangible Assets and Liabilities - Narrative (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2008	Mar. 31, 2020	Feb. 04, 2019
Trade name
Finite-Lived Intangible Assets [Line Items]
Intangible assets, residual value	$ 0
Finite-lived intangible asset, useful life	20 years
Power supply agreements | Minimum
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life	7 years
Power supply agreements | Maximum
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life	19 years
Cleco Katrina/Rita
Finite-Lived Intangible Assets [Line Items]
Intangible assets, residual value			$ 0
Cleco Katrina/Rita | Cleco Katrina/Rita right to bill and collect storm recovery charges
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets acquired		$ 177,500,000
Cleco Katrina/Rita | Cleco Katrina/Rita right to bill and collect storm recovery charges from customers, net of financing costs
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets acquired		176,000,000.0
Cleco Katrina/Rita | Financing costs
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets acquired		$ 1,500,000
Cleco Cajun | LTSA
Finite-Lived Intangible Assets [Line Items]
Intangible liabilities, remaining life	7 years
Cleco Cajun | Power supply agreements
Finite-Lived Intangible Assets [Line Items]
Intangible assets, residual value				$ 0
Cleco Cajun | Power supply agreements | Minimum
Finite-Lived Intangible Assets [Line Items]
Intangible assets, remaining life	2 years
Cleco Cajun | Power supply agreements | Maximum
Finite-Lived Intangible Assets [Line Items]
Intangible assets, remaining life	8 years