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, 2019	Dec. 31, 2018
Asset description
Institutional money market funds	$ 111,885	$ 133,722
Total assets	122,556	157,077
Liability description
Total liabilities	1,298	468
FTRs
Asset description
FTRs and other commodity derivatives	9,926	23,355
Liability description
FTRs and other commodity derivatives	1,257	468
Other commodity derivatives
Asset description
FTRs and other commodity derivatives	745	0
Liability description
FTRs and other commodity derivatives	41	0
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) | 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) | 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	111,885	133,722
Total assets	112,630	133,722
Liability description
Total liabilities	41	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) | Other commodity derivatives
Asset description
FTRs and other commodity derivatives	745	0
Liability description
FTRs and other commodity derivatives	41	0
SIGNIFICANT UNOBSERVABLE INPUTS (LEVEL 3)
Asset description
Institutional money market funds	0	0
FTRs and other commodity derivatives	9,926	23,355
Total assets	9,926	23,355
Liability description
FTRs and other commodity derivatives	1,257	468
Total liabilities	1,257	468
SIGNIFICANT UNOBSERVABLE INPUTS (LEVEL 3) | FTRs
Asset description
FTRs and other commodity derivatives	9,926	23,355
Liability description
FTRs and other commodity derivatives	1,257	468
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
CLECO POWER
Asset description
Institutional money market funds	76,947	55,900
FTRs and other commodity derivatives	8,601	23,355
Total assets	85,548	79,255
Liability description
FTRs and other commodity derivatives	577	468
Total liabilities	577	468
CLECO POWER | QUOTED PRICES IN ACTIVE MARKETS FOR IDENTICAL ASSETS (LEVEL 1)
Asset description
Institutional money market funds	0	0
FTRs and other commodity derivatives	0	0
Total assets	0	0
Liability description
FTRs and other commodity derivatives	0	0
Total liabilities	0	0
CLECO POWER | SIGNIFICANT OTHER OBSERVABLE INPUTS (LEVEL 2)
Asset description
Institutional money market funds	76,947	55,900
FTRs and other commodity derivatives	0	0
Total assets	76,947	55,900
Liability description
FTRs and other commodity derivatives	0	0
Total liabilities	0	0
CLECO POWER | SIGNIFICANT UNOBSERVABLE INPUTS (LEVEL 3)
Asset description
Institutional money market funds	0	0
FTRs and other commodity derivatives	8,601	23,355
Total assets	8,601	23,355
Liability description
FTRs and other commodity derivatives	577	468
Total liabilities	$ 577	$ 468