Fair Value Accounting - Fair Value of Financial Assets and Liabilities Measured On A Recurring Basis (Details) - Measured on a Recurring Basis - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Asset description
Institutional money market funds	$ 87,686	$ 86,001
Total assets	101,951	99,405
Liability description
Total liabilities	1,545	3,237
CLECO POWER
Asset description
Institutional money market funds	38,242	25,357
Total assets	40,228	29,694
Liability description
Total liabilities	898	1,121
FTRs
Asset description
FTRs and other commodity derivatives	2,140	4,805
Liability description
FTRs and other commodity derivatives	1,117	1,625
FTRs | CLECO POWER
Asset description
FTRs and other commodity derivatives	1,986	4,337
Liability description
FTRs and other commodity derivatives	898	1,121
Other commodity derivatives
Asset description
FTRs and other commodity derivatives	12,125	8,599
Liability description
FTRs and other commodity derivatives	428	1,612
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	87,686	86,001
Total assets	99,811	94,600
Liability description
Total liabilities	428	1,612
SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 2) | CLECO POWER
Asset description
Institutional money market funds	38,242	25,357
Total assets	38,242	25,357
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	12,125	8,599
Liability description
FTRs and other commodity derivatives	428	1,612
SIGNIFICANT UNOBSERVABLE INPUTS (LEVEL 3)
Asset description
Institutional money market funds	0	0
FTRs and other commodity derivatives	2,140	4,805
Total assets	2,140	4,805
Liability description
FTRs and other commodity derivatives	1,117	1,625
Total liabilities	1,117	1,625
SIGNIFICANT UNOBSERVABLE INPUTS (LEVEL 3) | CLECO POWER
Asset description
Institutional money market funds	0	0
FTRs and other commodity derivatives	1,986	4,337
Total assets	1,986	4,337
Liability description
FTRs and other commodity derivatives	898	1,121
Total liabilities	898	1,121
SIGNIFICANT UNOBSERVABLE INPUTS (LEVEL 3) | FTRs
Asset description
FTRs and other commodity derivatives	2,140	4,805
Liability description
FTRs and other commodity derivatives	1,117	1,625
SIGNIFICANT UNOBSERVABLE INPUTS (LEVEL 3) | FTRs | CLECO POWER
Asset description
FTRs and other commodity derivatives	1,986	4,337
Liability description
FTRs and other commodity derivatives	898	1,121
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