Fair Value Accounting and Financial Instruments - Carrying Value and Estimated Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deferred debt issuance costs not included in the carrying value of long-term debt	$ 14,100	$ 13,400
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	8,500	7,000
CARRYING VALUE
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	3,550,179	3,230,500
CARRYING VALUE | CLECO POWER
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	1,820,177	1,494,947
FAIR VALUE
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	3,836,960	3,541,349
FAIR VALUE | CLECO POWER
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	$ 2,100,029	$ 1,794,799