Fair Value Accounting - Institutional Money Market Funds (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Cash and cash equivalents	$ 525,112	$ 103,409
CLECO POWER
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Cash and cash equivalents	322,112	49,509
Current restricted cash and cash equivalents
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Restricted cash and cash equivalents	4,619	11,100
Current restricted cash and cash equivalents | CLECO POWER
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Restricted cash and cash equivalents	4,619	11,100
Non-current restricted cash and cash equivalents
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Restricted cash and cash equivalents	744	15,134
Non-current restricted cash and cash equivalents | CLECO POWER
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Restricted cash and cash equivalents	$ 0	$ 14,294