Fair Value Accounting - Carrying Value and Estimated Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deferred debt issuance costs not included in the carrying value of long-term debt	$ 13,400	$ 13,700
CARRYING VALUE*
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	3,230,500	3,188,664
FAIR VALUE
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	3,541,349	3,371,915
CLECO POWER
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deferred debt issuance costs not included in the carrying value of long-term debt	7,000	7,400
CLECO POWER | CARRYING VALUE*
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	1,494,947	1,380,688
CLECO POWER | FAIR VALUE
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	$ 1,794,799	$ 1,601,865