Fair Value Accounting - Fair Value of Financial Assets and Liabilities Measured On A Recurring Basis (Details) - Measured on a Recurring Basis - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Asset description
Institutional money market funds	$ 530,475	$ 129,643
Total assets	555,725	136,666
Liability description
Total liabilities	2,580	6,417
CLECO POWER
Asset description
Institutional money market funds	326,731	74,903
Total assets	333,908	81,214
Liability description
Total liabilities	1,765	586
FTRs
Asset description
FTRs and other commodity derivatives	7,907	6,822
Liability description
FTRs and other commodity derivatives	2,580	1,044
FTRs | CLECO POWER
Asset description
FTRs and other commodity derivatives	7,177	6,311
Liability description
FTRs and other commodity derivatives	1,765	586
Other commodity derivatives
Asset description
FTRs and other commodity derivatives	17,343	201
Liability description
FTRs and other commodity derivatives	0	5,373
QUOTED PRICES IN ACTIVE MARKETS FOR IDENTICAL ASSETS (LEVEL 1)
Asset description
Institutional money market funds	0	0
Total assets	0	0
Liability description
Total liabilities	0	0
QUOTED PRICES IN ACTIVE MARKETS FOR IDENTICAL ASSETS (LEVEL 1) | CLECO POWER
Asset description
Institutional money market funds	0	0
Total assets	0	0
Liability description
Total liabilities	0	0
QUOTED PRICES IN ACTIVE MARKETS FOR IDENTICAL ASSETS (LEVEL 1) | FTRs
Asset description
FTRs and other commodity derivatives	0	0
Liability description
FTRs and other commodity derivatives	0	0
QUOTED PRICES IN ACTIVE MARKETS FOR IDENTICAL ASSETS (LEVEL 1) | FTRs | CLECO POWER
Asset description
FTRs and other commodity derivatives	0	0
Liability description
FTRs and other commodity derivatives	0	0
QUOTED PRICES IN ACTIVE MARKETS FOR IDENTICAL ASSETS (LEVEL 1) | Other commodity derivatives
Asset description
FTRs and other commodity derivatives	0	0
Liability description
FTRs and other commodity derivatives	0	0
SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 2)
Asset description
Institutional money market funds	530,475	129,643
Total assets	547,818	129,844
Liability description
Total liabilities	0	5,373
SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 2) | CLECO POWER
Asset description
Institutional money market funds	326,731	74,903
Total assets	326,731	74,903
Liability description
Total liabilities	0	0
SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 2) | FTRs
Asset description
FTRs and other commodity derivatives	0	0
Liability description
FTRs and other commodity derivatives	0	0
SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 2) | FTRs | CLECO POWER
Asset description
FTRs and other commodity derivatives	0	0
Liability description
FTRs and other commodity derivatives	0	0
SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 2) | Other commodity derivatives
Asset description
FTRs and other commodity derivatives	17,343	201
Liability description
FTRs and other commodity derivatives	0	5,373
SIGNIFICANT UNOBSERVABLE INPUTS (LEVEL 3)
Asset description
Institutional money market funds	0	0
FTRs and other commodity derivatives	7,907	6,822
Total assets	7,907	6,822
Liability description
FTRs and other commodity derivatives	2,580	1,044
Total liabilities	2,580	1,044
SIGNIFICANT UNOBSERVABLE INPUTS (LEVEL 3) | CLECO POWER
Asset description
Institutional money market funds	0	0
FTRs and other commodity derivatives	7,177	6,311
Total assets	7,177	6,311
Liability description
FTRs and other commodity derivatives	1,765	586
Total liabilities	1,765	586
SIGNIFICANT UNOBSERVABLE INPUTS (LEVEL 3) | FTRs
Asset description
FTRs and other commodity derivatives	7,907	6,822
Liability description
FTRs and other commodity derivatives	2,580	1,044
SIGNIFICANT UNOBSERVABLE INPUTS (LEVEL 3) | FTRs | CLECO POWER
Asset description
FTRs and other commodity derivatives	7,177	6,311
Liability description
FTRs and other commodity derivatives	1,765	586
SIGNIFICANT UNOBSERVABLE INPUTS (LEVEL 3) | Other commodity derivatives
Asset description
FTRs and other commodity derivatives	0	0
Liability description
FTRs and other commodity derivatives	$ 0	$ 0