Pension Plan and Employee Benefits, Components of Periodic Benefit Costs and Weighted-Average Assumptions (Details) - USD ($) $ in Thousands		3 Months Ended		4 Months Ended	5 Months Ended	9 Months Ended		12 Months Ended
	Mar. 30, 2017	Mar. 30, 2017	Apr. 12, 2016	Dec. 31, 2016	Aug. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Mar. 29, 2017	Apr. 13, 2016
Pension Plan [Member]
Weighted-average assumptions used to determine the benefit obligation
Discount rate (in hundredths)				4.27%		3.73%	4.27%		3.73%	4.27%
Rate of compensation increase (in hundredths)				3.03%		2.98%	3.03%		2.98%	3.03%
Weighted-average assumptions used to determine the net benefit cost
Expected return on plan assets (in hundredths)									6.08%	6.21%
Other Postretirement Benefits Plan [Member]
Weighted-average assumptions used to determine the benefit obligation
Discount rate (in hundredths)				3.81%		3.47%	3.81%		3.47%	3.81%
SERP Benefits [Member]
Components of net periodic pension and other benefits costs [Abstract]
Curtailments			$ 3,600
Special/contractual termination benefits	$ 300		$ 3,200
Weighted-average assumptions used to determine the benefit obligation
Discount rate (in hundredths)	4.08%	4.08%	4.60%	4.22%	3.47%	3.70%	4.22%		3.70%	4.22%		4.22%	4.15%
Rate of compensation increase (in hundredths)				5.00%		5.00%	5.00%		5.00%	5.00%
Subsequent Event [Member] | Pension Plan [Member]
Weighted-average assumptions used to determine the net benefit cost
Expected return on plan assets (in hundredths)								5.86%
Increase (decrease) in expected pension costs								$ 1,800
Successor [Member] | Pension Plan [Member]
Components of net periodic pension and other benefits costs [Abstract]
Service cost							$ 6,909		$ 9,039
Interest cost							15,088		21,648
Expected return on plan assets							(17,310)		(24,064)
Prior period service (credit) cost							(51)		(71)
Net loss							8,138		10,008
Net periodic benefit cost							12,774		$ 16,560
Expected net periodic benefit cost, pension plan							$ 17,500
Weighted-average assumptions used to determine the benefit obligation
Discount rate (in hundredths)													4.21%
Weighted-average assumptions used to determine the net benefit cost
Discount rate (in hundredths)							4.21%		4.27%
Rate of compensation increase (in hundredths)							3.03%		2.98%
Successor [Member] | Other Postretirement Benefits Plan [Member]
Components of net periodic pension and other benefits costs [Abstract]
Service cost							$ 1,112		$ 1,446
Interest cost							1,237		1,569
Expected return on plan assets							0		0
Prior period service (credit) cost							0		0
Net loss							0		(50)
Net periodic benefit cost							$ 2,349		$ 2,965
Weighted-average assumptions used to determine the net benefit cost
Discount rate (in hundredths)							4.08%		3.81%
Successor [Member] | SERP Benefits [Member]
Components of net periodic pension and other benefits costs [Abstract]
Service cost							$ 571		$ 494
Interest cost							2,275		3,239
Prior period service (credit) cost							(50)		(190)
Net loss							1,651		2,105
Net Periodic Benefit Cost, excluding Settlements and Curtailments							4,447		5,648
Curtailments							0		0
Special/contractual termination benefits							0		315
Net periodic benefit cost							4,447		5,963
Weighted-average assumptions used to determine the net benefit cost
Discount rate (in hundredths)		4.22%		3.47%	4.15%	4.08%
Rate of compensation increase (in hundredths)		5.00%		5.00%	5.00%	5.00%
Predecessor [Member] | Pension Plan [Member]
Components of net periodic pension and other benefits costs [Abstract]
Service cost			$ 2,563								$ 10,419
Interest cost			6,242								20,795
Expected return on plan assets			(6,812)								(23,382)
Prior period service (credit) cost			(20)								(71)
Net loss			2,798								13,828
Net periodic benefit cost			4,771								$ 21,589
Expected net periodic benefit cost, pension plan			$ 15,900
Weighted-average assumptions used to determine the benefit obligation
Discount rate (in hundredths)			4.62%
Weighted-average assumptions used to determine the net benefit cost
Discount rate (in hundredths)			4.62%								4.21%
Expected return on plan assets (in hundredths)			6.21%								6.15%
Rate of compensation increase (in hundredths)			3.03%								3.082%
Predecessor [Member] | Other Postretirement Benefits Plan [Member]
Components of net periodic pension and other benefits costs [Abstract]
Service cost			$ 431								$ 1,635
Interest cost			476								1,607
Expected return on plan assets			0								0
Prior period service (credit) cost			34								119
Net loss			181								866
Net periodic benefit cost			$ 1,122								$ 4,227
Weighted-average assumptions used to determine the net benefit cost
Discount rate (in hundredths)			4.08%								3.76%
Predecessor [Member] | SERP Benefits [Member]
Components of net periodic pension and other benefits costs [Abstract]
Service cost			$ 702								$ 2,705
Interest cost			900								3,056
Prior period service (credit) cost			17								54
Net loss			574								2,973
Net Periodic Benefit Cost, excluding Settlements and Curtailments			2,193								8,788
Curtailments			3,602								0
Special/contractual termination benefits			3,222								0
Net periodic benefit cost			$ 9,017								$ 8,788
Weighted-average assumptions used to determine the net benefit cost
Discount rate (in hundredths)			4.60%								4.20%
Rate of compensation increase (in hundredths)			5.00%								5.00%
Cleco Power [Member] | Other Postretirement Benefits Plan [Member]
Components of net periodic pension and other benefits costs [Abstract]
Net periodic benefit cost									3,300	$ 3,500	$ 3,600
Cleco Power [Member] | SERP Benefits [Member]
Components of net periodic pension and other benefits costs [Abstract]
Net periodic benefit cost									1,300	$ 1,400	2,200
Other Subsidiaries [Member] | Successor [Member] | Pension Plan [Member]
Components of net periodic pension and other benefits costs [Abstract]
Net periodic benefit cost							$ 1,300		$ 1,800
Other Subsidiaries [Member] | Predecessor [Member] | Pension Plan [Member]
Components of net periodic pension and other benefits costs [Abstract]
Net periodic benefit cost			$ 500								$ 2,100