Pension Plan and Employee Benefits - Narrative (Details) - USD ($)	1 Months Ended	3 Months Ended		9 Months Ended
	Mar. 31, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2016
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost		$ 4,709,000	$ 4,140,000	$ 14,126,000	$ 12,419,000
Other Benefits Plan
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost		793,000	654,000	2,192,000	2,223,000
Assets held-in-trust, noncurrent		0		0
SERP
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost		1,593,000	1,412,000	4,779,000	4,551,000
Discount rate	4.08%					4.22%
Special termination benefit for executive officer	$ 300,000	0	0	0	315,000
CLECO POWER | Other Benefits Plan
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost		900,000	800,000	2,500,000	2,500,000
CLECO POWER | SERP
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost		400,000	300,000	1,100,000	900,000
Other Subsidiaries | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost		$ 500,000	$ 500,000	$ 1,500,000	$ 1,400,000