Cleco Cajun Transaction (Details)	Feb. 05, 2019 USD ($)	Feb. 04, 2019 USD ($) instrument municipality cooperative investor_owned_utility MW	Dec. 31, 2018 USD ($)
Subsequent Event | New Roads, Louisiana | Coal-fired Generating Station
Business Acquisition [Line Items]
Number of megawatts in station or facility (mw) | MW		588
Subsequent Event | Jennings, Louisiana | Natural-gas-fired Peaking Facility
Business Acquisition [Line Items]
Number of megawatts in station or facility (mw) | MW		225
Total number of megawatts in facility (mw) | MW		300
Subsequent Event | Cleco Holdings
Business Acquisition [Line Items]
Debt term		3 years
Debt to capital ratio		0.65
Repayment period		12 months
Subsequent Event | Cleco Holdings | Revolving Credit Facility
Business Acquisition [Line Items]
Increase in credit facility capacity		$ 75,000,000
Maximum borrowing capacity		175,000,000.0
Repayments of credit facility		75,000,000
Subsequent Event | Cleco Holdings | Letters of Credit
Business Acquisition [Line Items]
Maximum borrowing capacity		1,100,000.0
Subsequent Event | Cleco Holdings | Bridge Loan
Business Acquisition [Line Items]
Debt amount		300,000,000.0
Subsequent Event | Cleco Holdings | Term Loan
Business Acquisition [Line Items]
Debt amount		100,000,000.0
Subsequent Event | Cleco Cajun | Letters of Credit
Business Acquisition [Line Items]
Maximum borrowing capacity		$ 1,100,000.0
Number of instruments issued | instrument		3
Subsequent Event | NRG South Central
Business Acquisition [Line Items]
Number of customers served | investor_owned_utility		1
Business acquisition, transaction price		$ 962,200,000
Cash paid		1,000,000,000
Working capital adjustment		$ 37,800,000
Subsequent Event | NRG South Central | Sterlington, Louisiana | Natural-gas-fired Generating Station
Business Acquisition [Line Items]
Number of megawatts in station or facility (mw) | MW		176
Subsequent Event | NRG South Central | Jarreau, Louisiana | Natural-gas-fired Facility
Business Acquisition [Line Items]
Number of megawatts in station or facility (mw) | MW		220
Subsequent Event | NRG South Central | Jarreau, Louisiana | Natural-gas-fired Peaking Facility
Business Acquisition [Line Items]
Number of megawatts in station or facility (mw) | MW		210
Subsequent Event | NRG South Central | New Roads, Louisiana | Coal-fired Generating Facility
Business Acquisition [Line Items]
Number of megawatts in station or facility (mw) | MW		580
Subsequent Event | NRG South Central | New Roads, Louisiana | Coal-fired Generating Station
Business Acquisition [Line Items]
Percentage of voting interests acquired		58.00%
Subsequent Event | NRG South Central | New Roads, Louisiana | Natural-gas-fired Generating Station
Business Acquisition [Line Items]
Number of megawatts in station or facility (mw) | MW		540
Subsequent Event | NRG South Central | Deweyville, Texas | Natural-gas-fired Generating Station
Business Acquisition [Line Items]
Number of megawatts in station or facility (mw) | MW		1,263
Subsequent Event | NRG South Central | Louisiana
Business Acquisition [Line Items]
Number of customers served | cooperative		9
Subsequent Event | NRG South Central | Arkansas, Louisiana, and Texas
Business Acquisition [Line Items]
Number of customers served | municipality		5
Subsequent Event | NRG South Central | Cleco Holdings
Business Acquisition [Line Items]
Cash paid		$ 102,300,000
Subsequent Event | NRG South Central | Cleco Group
Business Acquisition [Line Items]
Equity infusion		$ 384,900,000
Line of Credit | Cleco Holdings
Business Acquisition [Line Items]
Maximum borrowing capacity			$ 100,000,000
Line of Credit | Subsequent Event | Cleco Holdings
Business Acquisition [Line Items]
Payments on credit facilities	$ 75,000,000