Business Combination - Narrative (Details)		3 Months Ended
	Feb. 04, 2019 USD ($) instrument MW	Mar. 31, 2019 USD ($) municipality cooperative investor_owned_utility	Mar. 31, 2018 USD ($)	Jan. 31, 2019 USD ($)
Business Acquisition [Line Items]
Indemnification asset	$ 10,000,000
Draws on credit facilities		$ 108,000,000	$ 0
NRG South Central
Business Acquisition [Line Items]
Conditional commitment due within one year		66,700,000
Consideration transferred	962,200,000
Acquisition price	1,000,000,000
Working capital and other adjustments	37,800,000
Debt amount				$ 400,000,000.0
Intangible assets	102,500,000
Intangible liabilities	31,900,000
Deferred lease revenue	61,900,000
Pro forma net income		32,986,000	32,637,000
NRG South Central | Transaction Related Expenses
Business Acquisition [Line Items]
Pro forma net income		$ 3,900,000	1,600,000
Power supply agreements
Business Acquisition [Line Items]
Intangible liabilities	7,800,000
Intangible liabilities, remaining life		6 years
Power supply agreements | NRG South Central
Business Acquisition [Line Items]
Intangible liabilities	$ 7,800,000
LTSA
Business Acquisition [Line Items]
Intangible liabilities, remaining life	7 years
LTSA | NRG South Central
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		5
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]
Annual reduction to retail customer rates	$ 4,000,000
Draws on credit facilities		$ 33,000,000	$ 0
CLECO HOLDINGS
Business Acquisition [Line Items]
Debt instrument term	3 years
Debt to capital ratio	0.65
Repayment period	12 months
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 | NRG South Central
Business Acquisition [Line Items]
Acquisition price	102,300,000
Cleco Group | NRG South Central
Business Acquisition [Line Items]
Equity contribution	$ 384,900,000