Business Combination - Narrative (Details)		1 Months Ended	3 Months Ended			9 Months Ended
	Feb. 04, 2019 USD ($) municipality cooperative investor_owned_utility instrument MW	Jan. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)
Business Acquisition [Line Items]
Repayment of long-term debt						$ 390,571,000	$ 19,193,000
Draws on credit facilities						108,000,000	0
Electric operations			$ 451,902,000		$ 341,062,000	1,130,318,000	897,486,000
Other operations revenue			(49,780,000)		(20,186,000)	(131,544,000)	(61,067,000)
Depreciation and amortization			57,004,000		43,763,000	158,395,000	128,076,000
South Central Generating
Business Acquisition [Line Items]
Repayment of long-term debt	$ 400,000,000	$ 400,000,000
Conditional commitment due within one year			66,700,000			66,700,000
Indemnification asset	10,000,000
Contingent liability	10,000,000
Consideration transferred	962,200,000
Acquisition price	1,000,000,000
Working capital and other adjustments	37,800,000
Intangible assets	98,900,000
Intangible liabilities	38,300,000
Deferred lease revenue	58,300,000
Pro forma net income			56,004,000		71,076,000	122,771,000	140,255,000
South Central Generating | Fair Value Adjustments
Business Acquisition [Line Items]
Electric operations				$ 500,000
Other operations revenue				100,000
Depreciation and amortization				$ 200,000
South Central Generating | Transaction Related Expenses
Business Acquisition [Line Items]
Pro forma net income			600,000			$ 4,500,000
Power supply agreements
Business Acquisition [Line Items]
Intangible liabilities	14,200,000
Intangible liabilities, remaining life						6 years
Power supply agreements | South Central Generating
Business Acquisition [Line Items]
Intangible liabilities	$ 14,200,000
LTSA
Business Acquisition [Line Items]
Intangible liabilities, remaining life	7 years
LTSA | South Central Generating
Business Acquisition [Line Items]
Intangible liabilities	$ 24,100,000
Intangible liabilities, remaining life	7 years
Cleco Cajun
Business Acquisition [Line Items]
Number of customers served | investor_owned_utility	1
Cleco Cajun | Letters of Credit
Business Acquisition [Line Items]
Line of credit facility, maximum borrowing capacity	$ 1,100,000.0
Number of letters of credit | instrument	3
Cleco Cajun | Jennings, Louisiana
Business Acquisition [Line Items]
Number of megawatts in station or facility (mw) | MW	225
Cleco Cajun | Louisiana
Business Acquisition [Line Items]
Number of customers served | cooperative	9
Cleco Cajun | Arkansas, Louisiana, and Texas
Business Acquisition [Line Items]
Number of customers served | municipality	3
Cleco Cajun | Natural-gas-fired Facility | Jarreau, Louisiana
Business Acquisition [Line Items]
Number of megawatts in station or facility (mw) | MW	220
Cleco Cajun | Natural-gas-fired Peaking Facility | Jarreau, Louisiana
Business Acquisition [Line Items]
Number of megawatts in station or facility (mw) | MW	210
Cleco Cajun | Natural-gas-fired Peaking Facility | Jennings, Louisiana
Business Acquisition [Line Items]
Number of megawatts in station or facility (mw) | MW	300
Cleco Cajun | Coal-fired Generating Facility | New Roads, Louisiana
Business Acquisition [Line Items]
Number of megawatts in station or facility (mw) | MW	580
Cleco Cajun | Coal-fired Generating Station | New Roads, Louisiana | Jointly Owned Electricity Generation Plant
Business Acquisition [Line Items]
Number of megawatts in station or facility (mw) | MW	588
Percentage ownership	58.00%
Cleco Cajun | Natural-gas-fired Generating Station | Sterlington, Louisiana
Business Acquisition [Line Items]
Number of megawatts in station or facility (mw) | MW	176
Cleco Cajun | Natural-gas-fired Generating Station | New Roads, Louisiana
Business Acquisition [Line Items]
Number of megawatts in station or facility (mw) | MW	540
Cleco Cajun | Natural-gas-fired Generating Station | Deweyville, Texas
Business Acquisition [Line Items]
Number of megawatts in station or facility (mw) | MW	1,263
CLECO POWER
Business Acquisition [Line Items]
Repayment of long-term debt						$ 20,571,000	19,193,000
Annual reduction to retail customer rates	$ 4,000,000	$ 4,000,000
Draws on credit facilities						33,000,000	0
Electric operations			339,869,000		343,482,000	862,969,000	904,746,000
Other operations revenue			(18,485,000)		(20,186,000)	(53,318,000)	(61,066,000)
Depreciation and amortization			$ 44,903,000		$ 41,687,000	$ 126,610,000	$ 121,796,000
CLECO HOLDINGS
Business Acquisition [Line Items]
Debt instrument term	3 years
Debt to capital ratio	0.65
CLECO HOLDINGS | Revolving Credit Facility
Business Acquisition [Line Items]
Increase in credit facility capacity	$ 75,000,000
Line of credit facility, maximum borrowing capacity	175,000,000.0
Draws on credit facilities	75,000,000.0
Repayments of credit facilities	75,000,000
CLECO HOLDINGS | Letters of Credit
Business Acquisition [Line Items]
Line of credit facility, maximum borrowing capacity	1,100,000.0
CLECO HOLDINGS | Bridge Loan
Business Acquisition [Line Items]
Debt amount	300,000,000.0
CLECO HOLDINGS | Term loan
Business Acquisition [Line Items]
Debt amount	100,000,000.0
CLECO HOLDINGS | South Central Generating
Business Acquisition [Line Items]
Acquisition price	102,300,000
Cleco Group | South Central Generating
Business Acquisition [Line Items]
Equity contribution	$ 384,900,000