Intangible Assets and Goodwill - Narrative (Details) - USD ($)		9 Months Ended	12 Months Ended
	Apr. 13, 2016	Dec. 31, 2016	Dec. 31, 2018	Dec. 31, 2008	Aug. 01, 2018	Dec. 31, 2017	Dec. 31, 2015
Acquired Finite-Lived Intangible Assets [Line Items]
Accumulated amortization			$ 76,491,000			$ 45,948,000
Expected amortization in the year 2019			29,414,000
Expected amortization in the year 2020			11,549,000
Goodwill	$ 1,490,797,000		1,490,797,000			1,490,797,000
Carrying value of equity			2,124,740,000			2,096,357,000
Power supply agreements
Acquired Finite-Lived Intangible Assets [Line Items]
Residual value	$ 0
Trade name
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible asset expected useful life (in years)	20 years	20 years
Residual value	$ 0
MINIMUM | Power supply agreements
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible asset expected useful life (in years)	4 years
MAXIMUM | Power supply agreements
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible asset expected useful life (in years)	16 years
Cleco Katrina/Rita | Cleco Katrina/Rita right to bill and collect storm recovery charges
Acquired Finite-Lived Intangible Assets [Line Items]
Acquired intangible asset				$ 177,500,000
Residual value				0
Accumulated amortization	$ 0
Cleco Katrina/Rita | Contractual Rights
Acquired Finite-Lived Intangible Assets [Line Items]
Acquired intangible asset				176,000,000
Cleco Katrina/Rita | Financing costs
Acquired Finite-Lived Intangible Assets [Line Items]
Acquired intangible asset				$ 1,500,000
Cleco Katrina/Rita | MINIMUM | Cleco Katrina/Rita right to bill and collect storm recovery charges
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible asset expected useful life (in years)				12 years
Cleco Katrina/Rita | MAXIMUM | Cleco Katrina/Rita right to bill and collect storm recovery charges
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible asset expected useful life (in years)				15 years
CLECO POWER
Acquired Finite-Lived Intangible Assets [Line Items]
Expected amortization in the year 2019			19,500,000
Expected amortization in the year 2020			1,600,000
Impairment of goodwill			0
Equity, fair value					$ 3,550,000,000
Carrying value of equity		$ 1,535,202,000	1,594,533,000		$ 3,300,000,000	1,550,679,000	$ 1,552,404,000
Excess of the fair value over the carrying value, percent					7.50%
Excess of the fair value over the carrying value					$ 247,400,000
Accumulated impairment charges					$ 0
CLECO POWER | Measurement Input, Discount Rate
Acquired Finite-Lived Intangible Assets [Line Items]
WACC					5.70%
CLECO POWER | Measurement Input, Long-term Revenue Growth Rate
Acquired Finite-Lived Intangible Assets [Line Items]
WACC					2.50%
CLECO POWER | Cleco Katrina/Rita right to bill and collect storm recovery charges
Acquired Finite-Lived Intangible Assets [Line Items]
Accumulated amortization			$ 156,444,000			$ 135,836,000
CLECO POWER | MINIMUM | Measurement Input, Discount Rate | Pro Forma
Acquired Finite-Lived Intangible Assets [Line Items]
Equity, fair value					$ 3,630,000,000
WACC					5.60%
CLECO POWER | MINIMUM | Measurement Input, Long-term Revenue Growth Rate | Pro Forma
Acquired Finite-Lived Intangible Assets [Line Items]
Equity, fair value					$ 3,480,000,000
WACC					2.40%
CLECO POWER | MAXIMUM | Measurement Input, Discount Rate | Pro Forma
Acquired Finite-Lived Intangible Assets [Line Items]
Equity, fair value					$ 3,470,000,000
WACC					5.80%
CLECO POWER | MAXIMUM | Measurement Input, Long-term Revenue Growth Rate | Pro Forma
Acquired Finite-Lived Intangible Assets [Line Items]
Equity, fair value					$ 3,620,000,000
WACC					2.60%