Regulatory Assets and Liabilities - Schedule of Regulatory Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Regulatory Liabilities [Line Items]
Total regulatory assets, net	$ 408,265	$ 311,525
CLECO POWER
Regulatory Liabilities [Line Items]
Total regulatory assets, net	257,939	152,549
CLECO POWER | Corporate franchise tax, net
Regulatory Liabilities [Line Items]
Regulatory liabilities	(1,262)	(1,145)
CLECO POWER | Deferred taxes, net
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ (145,173)	(146,948)
CLECO POWER | St. Mary Clean Energy Center
Regulatory Liabilities [Line Items]
Regulatory liabilities		$ (4,696)	$ (9,600)