Summary of Significant Accounting Policies - Restricted Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Restricted Cash and Cash Equivalents Items [Line Items]
Current	$ 2,352	$ 4,545
Non-current	745	744
Total restricted cash and cash equivalents	3,097	5,289
CLECO POWER
Restricted Cash and Cash Equivalents Items [Line Items]
Current	2,352	4,545
Total restricted cash and cash equivalents	2,352	4,545
Cleco Katrina/Rita storm recovery surcharge
Restricted Cash and Cash Equivalents Items [Line Items]
Current	1,674	2,626
Cleco Katrina/Rita storm recovery surcharge | CLECO POWER
Restricted Cash and Cash Equivalents Items [Line Items]
Current	1,674	2,626
Charitable contributions
Restricted Cash and Cash Equivalents Items [Line Items]
Current	678	1,718
Charitable contributions | CLECO POWER
Restricted Cash and Cash Equivalents Items [Line Items]
Current	678	1,718
Rate credit escrow
Restricted Cash and Cash Equivalents Items [Line Items]
Current	0	201
Rate credit escrow | CLECO POWER
Restricted Cash and Cash Equivalents Items [Line Items]
Current	0	201
Diversified Lands’ mitigation escrow
Restricted Cash and Cash Equivalents Items [Line Items]
Non-current	22	22
Cleco Cajun’s defense fund
Restricted Cash and Cash Equivalents Items [Line Items]
Non-current	$ 723	$ 722