Agreement and Plan of Merger (Details) - USD ($) $ / shares in Units, $ in Millions	Mar. 31, 2016	Sep. 30, 2015	Feb. 26, 2015	Dec. 31, 2014	Oct. 17, 2014
Business Acquisition [Line Items]
Common stock, par value (in dollars per share)		$ 1		$ 1
Merger Agreement, Acquirer Required Termination Fee					$ 180.0
Cleco Corporation [Member]
Business Acquisition [Line Items]
Common stock, par value (in dollars per share)					$ 1.00
Share price at the time of the Merger (in dollars per share)					$ 55.37
Percentage of shareholder approval of the Merger Agreement (in hundredths)			77.00%
Merger Agreement, Acquiree Required Termination Fee					$ 120.0
Subsequent Event [Member] | Cleco Corporation [Member]
Business Acquisition [Line Items]
Additional contingency fees payable upon the completion of the Merger	$ 12.0