Fair Value Accounting and Financial Instruments - Institutional Money Market Funds (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 249,711	$ 80,712
CLECO POWER
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Cash and cash equivalents	133,411	20,812
Current restricted cash and cash equivalents
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Restricted cash and cash equivalents	2,352	4,545
Current restricted cash and cash equivalents | CLECO POWER
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Restricted cash and cash equivalents	2,352	4,545
Non-current restricted cash and cash equivalents
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Restricted cash and cash equivalents	$ 744	$ 744