Fair Value Accounting - Carrying Value and Estimated Fair Value (Details) - USD ($) $ in Thousands	Mar. 31, 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	$ 12,700	$ 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	6,800	7,000
CARRYING VALUE
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	3,228,726	3,230,500
CARRYING VALUE | CLECO POWER
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	1,495,024	1,494,947
FAIR VALUE
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	3,556,579	3,541,349
FAIR VALUE | CLECO POWER
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	$ 1,865,938	$ 1,794,799