Pension Plan and Employee Benefits - Current and Non-Current Portions of SERP Liability (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Non-current	$ 320,504	$ 314,653
SERP Benefits
Defined Benefit Plan Disclosure [Line Items]
Current	4,703	4,703
Non-current	90,880	92,522
CLECO POWER
Defined Benefit Plan Disclosure [Line Items]
Non-current	237,818	230,825
CLECO POWER | SERP Benefits
Defined Benefit Plan Disclosure [Line Items]
Current	711	711
Non-current	$ 19,240	$ 19,828