Intangible Assets - Narrative (Details) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2008	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Accumulated amortization	$ 60,909,000		$ 60,909,000			$ 45,948,000
Reduction in revenue on intangible assets for power supply agreements	2,400,000	$ 2,400,000	4,800,000	$ 6,000,000
Trade name
Finite-Lived Intangible Assets [Line Items]
Residual value	0		0
Amortization of intangible assets (less than for Trade name)	100,000	100,000	$ 100,000	100,000
Finite-lived intangible asset, useful life			20 years
Power supply agreements
Finite-Lived Intangible Assets [Line Items]
Residual value	0		$ 0
Power supply agreements | Minimum
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life			5 years
Power supply agreements | Maximum
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, useful life			17 years
CLECO POWER
Finite-Lived Intangible Assets [Line Items]
Residual value	0		$ 0
Accumulated amortization	145,830,000		145,830,000		$ 0	$ 135,836,000
CLECO POWER | Cleco Katrina/Rita right to bill and collect storm recovery charges
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets acquired					177,500,000
Amortization of intangible assets (less than for Trade name)	$ 5,500,000	$ 4,700,000	$ 10,000,000	$ 8,200,000
CLECO POWER | Cleco Katrina/Rita right to bill and collect storm recovery charges from customers, net of financing costs
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets acquired					176,000,000
CLECO POWER | Financing costs
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets acquired					$ 1,500,000