Fair Value Accounting - Narrative (Details) MWh in Millions, $ in Millions	9 Months Ended	12 Months Ended
Sep. 30, 2018 USD ($) MWh	Dec. 31, 2017 USD ($) MWh
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Fair value, concentration of risk, amount of money market funds in cash and cash equivalents	$ 175.6	$ 111.1
Current restricted cash and cash equivalents
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Fair value, concentration of risk, amount of money market funds in institutional money market funds	5.2	13.1
Non-current restricted cash and cash equivalents
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Fair value, concentration of risk, amount of money market funds in institutional money market funds	18.7	20.1
CLECO POWER
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Fair value, concentration of risk, amount of money market funds in cash and cash equivalents	$ 54.2	$ 62.5
Volume of FTRs outstanding (MWh) \| MWh	13.0	9.0
CLECO POWER \| Current restricted cash and cash equivalents
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Fair value, concentration of risk, amount of money market funds in institutional money market funds	$ 5.2	$ 13.1
CLECO POWER \| Non-current restricted cash and cash equivalents
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Fair value, concentration of risk, amount of money market funds in institutional money market funds	$ 18.7	$ 20.1

Nominal energy measure used to calculate payments on a derivative instrument.

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- Definition

This item represents disclosure of all significant concentrations of credit risk or market risk arising from the subject financial instrument (as defined), whether from an individual counterparty or groups of counterparties.

+ References

No definition available.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=109250915&loc=d3e13531-108611

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