Fair Value Accounting - Amount of Gain (Loss) Recognized in Income on Derivatives (Details) - Derivatives Not Designated as Hedging Instrument - FTRs - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net gain (loss) recognized in income on derivatives	$ (6,413)	$ (7,814)	$ 35,093
Electric operations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amount of gain recognized in income on derivatives	9,213	13,043	39,659
Purchased power
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amount of loss recognized in income on derivatives	(3,467)	(15,685)	(4,566)
Fuel Used For Electric Generation
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amount of loss recognized in income on derivatives	(12,159)	(5,172)	0
Accumulated Deferred Fuel
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized gains (losses) associated with FTRs	500	(1,700)	11,900
CLECO POWER
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net gain (loss) recognized in income on derivatives	2,410	6,981	35,093
CLECO POWER | Electric operations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amount of gain recognized in income on derivatives	9,213	13,047	39,659
CLECO POWER | Purchased power
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amount of loss recognized in income on derivatives	(6,803)	(6,066)	(4,566)
CLECO POWER | Accumulated Deferred Fuel
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized gains (losses) associated with FTRs	$ 500	$ (900)	$ 11,900