Fair Value Accounting - Fair Value of Financial Assets and Liabilities Measured On A Recurring Basis (Details) - Measured On A Recurring Basis - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Asset Description
Institutional money market funds	$ 86,001	$ 129,643
Total assets	99,405	136,666
Liability Description
Total liabilities	3,237	6,417
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
SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 2)
Asset Description
Institutional money market funds	86,001	129,643
Total assets	94,600	129,844
Liability Description
Total liabilities	1,612	5,373
SIGNIFICANT UNOBSERVABLE INPUTS (LEVEL 3)
Asset Description
Institutional money market funds	0	0
FTRs and other commodity derivatives	4,805	6,822
Total assets	4,805	6,822
Liability Description
FTRs and other commodity derivatives	1,625	1,044
Total liabilities	1,625	1,044
CLECO POWER
Asset Description
Institutional money market funds	25,357	74,903
Total assets	29,694	81,214
Liability Description
Total liabilities	1,121	586
CLECO POWER | 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
CLECO POWER | SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 2)
Asset Description
Institutional money market funds	25,357	74,903
Total assets	25,357	74,903
Liability Description
Total liabilities	0	0
CLECO POWER | SIGNIFICANT UNOBSERVABLE INPUTS (LEVEL 3)
Asset Description
Institutional money market funds	0	0
FTRs and other commodity derivatives	4,337	6,311
Total assets	4,337	6,311
Liability Description
FTRs and other commodity derivatives	1,121	586
Total liabilities	1,121	586
Financial Transmission Right
Asset Description
FTRs and other commodity derivatives	4,805	6,822
Liability Description
FTRs and other commodity derivatives	1,625	1,044
Financial Transmission Right | QUOTED PRICES IN ACTIVE MARKETS FOR IDENTICAL ASSETS (LEVEL 1)
Asset Description
FTRs and other commodity derivatives	0	0
Liability Description
FTRs and other commodity derivatives	0	0
Financial Transmission Right | SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 2)
Asset Description
FTRs and other commodity derivatives	0	0
Liability Description
FTRs and other commodity derivatives	0	0
Financial Transmission Right | SIGNIFICANT UNOBSERVABLE INPUTS (LEVEL 3)
Asset Description
FTRs and other commodity derivatives	4,805	6,822
Liability Description
FTRs and other commodity derivatives	1,625	1,044
Financial Transmission Right | CLECO POWER
Asset Description
FTRs and other commodity derivatives	4,337	6,311
Liability Description
FTRs and other commodity derivatives	1,121	586
Financial Transmission Right | CLECO POWER | QUOTED PRICES IN ACTIVE MARKETS FOR IDENTICAL ASSETS (LEVEL 1)
Asset Description
FTRs and other commodity derivatives	0	0
Liability Description
FTRs and other commodity derivatives	0	0
Financial Transmission Right | CLECO POWER | SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 2)
Asset Description
FTRs and other commodity derivatives	0	0
Liability Description
FTRs and other commodity derivatives	0	0
Financial Transmission Right | CLECO POWER | SIGNIFICANT UNOBSERVABLE INPUTS (LEVEL 3)
Asset Description
FTRs and other commodity derivatives	4,337	6,311
Liability Description
FTRs and other commodity derivatives	1,121	586
Other commodity derivatives
Asset Description
FTRs and other commodity derivatives	8,599	201
Liability Description
FTRs and other commodity derivatives	1,612	5,373
Other commodity derivatives | QUOTED PRICES IN ACTIVE MARKETS FOR IDENTICAL ASSETS (LEVEL 1)
Asset Description
FTRs and other commodity derivatives	0	0
Liability Description
FTRs and other commodity derivatives	0	0
Other commodity derivatives | SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 2)
Asset Description
FTRs and other commodity derivatives	8,599	201
Liability Description
FTRs and other commodity derivatives	1,612	5,373
Other commodity derivatives | SIGNIFICANT UNOBSERVABLE INPUTS (LEVEL 3)
Asset Description
FTRs and other commodity derivatives	0	0
Liability Description
FTRs and other commodity derivatives	$ 0	$ 0